Progress 01/31/07 to 01/29/12
Outputs
Progress Report Objectives (from AD-416): The existing project objectives (as given below) reflect the redirection towards quantification of climate change effects: 1. Develop methods and techniques for quantifying natural and anthropogenic induced ephemeral-channel runoff and subsequent recharge in cooperation with U.S. Geological Survey Tucson Science Center under current and projected climate scenarios. 2. Develop methods and techniques to quantify and predict water budgets of riparian ecosystems under current and projected climate scenarios through direct measurements of evaporation and plant transpiration and predict water savings by removal of invasive mesquite vegetation. 3. Develop methods and techniques to explicitly quantify the spatial and temporal distribution of vegetation, land use, and infiltration reduction using remotely sensed methods to improve prediction of basin scale semi- arid water budget components. Approach (from AD-416): Methods of investigation include field and laboratory experimentation, as well as the development and use of state-of-the-science watershed models and the use of remote sensing for watershed characterization. Satellite derived rainfall will be evaluated using raingages for large area rainfall estimation, the enhancement of recharge due to urbanization will be examined in adjacent, well instrumented, natural and residentially developed catchments. High-resolution remotely sensing and rainfall simulator experiments will be used to evaluate the capability to remote estimate infiltration rates on compacted and constructed surfaces common to development at the urban-rural interface. Remote spectral surface responses will be combined with energy balance models and radiative transfer theory to estimate surface water, carbon and energy fluxes based on observations from a network of five eddy-covariance and two Bowen ratio towers. A number of modeling components for the Automated Geospatial Watershed Assessment (AGWA) will be developed or enhanced to enable a more realistic representation of watershed processes and best management practices. AGWA will be migrated to both the internet and ARCGIS platforms to enhance usability and access. In addition we will quantify the physical mechanisms and component fluxes that are responsible for the observed ecosystem-scale water and CO2 fluxes. Scientists will carry out this research at sites located across both a riparian and an upland woody plant encroachment gradient. Continue existing research under objective #3, and add activities to develop methods and techniques to quantify and predict water budgets under current and projected climate scenarios through direct measurements of evaporation and plant transpiration, and predict water savings by removal of invasive mesquite vegetation. This the final report for project 5342-13610-010-00D terminated in Jan. 2012. This project is followed by project 5342-13610-011-00D (Ecohydrological Processes, Scale, Climate Variability, and Watershed Management). Over the 5 years of the project a number of important advances were made under all project objectives which all fall under NP211 � Component Area 5: Watershed Management, Water Availability, and Ecosystem Restoration. Under Objective 1 classification strategies were developed to obtain improved estimates of impervious area with high- resolution remotely sensed imagery to refine the estimate of groundwater recharge resulting from urbanization. An important factor in determining the increase in runoff resulting from urbanization beyond the addition of impervious area was the compaction of soils from site preparation. Increases in runoff from a well-monitored sub-division were successfully modeled with a new �Urban� modeling element incorporated into the KINEROS2 rainfall-runoff and erosion model. Under Objective 2 the Automated Geospatial Watershed Assessment (AGWA) tool was significantly enhanced and a new version was released. AGWA has become an accepted and trusted tool for watershed management by local, state and Federal agencies as well as numerous universities and private consultants with over 3000 registered users from 160 countries or territories. Under Objective 3 research results contradicted the commonly held hypothesis that there is a positive feedback between canopy cover and soil moisture that then explains the stability of woody vegetation patterns - a key finding to understand desertification. In the case of woody plant encroachment, the current paradigm that more ecosystem carbon sequestration would occur under such conditions was not supported due to an increase in the release of CO2 from enhanced soil microbial respiration. A number of important advances were made in climate, plant, water, and carbon cycle interactions as a result of invasive species (Lehmann Lovegrass) encroachment in the ARS Walnut Gulch Experimental Watershed (WGEW) due to a long-term drought. The structural difference of Lovegrass (small basal area as compared to native gramma grasses) resulted in several important feedbacks. The small basal area resulted in higher runoff velocities and the first measureable erosion is over 20 years. Soil water evaporation more than doubled over the growing season and carbon uptake and the ratio of post-storm evaporation to evapotranspiration was altered. In addition, the MU completed a multi-year effort resulting in the publication of 20 papers in Water Resources Research describing and analyzing over 50 years of data collected at the WGEW. Substantial progress was also made in planning and conducting research and field experiments for the rangeland portion of the congressionally mandated NRCS Conservation Effects Assessment Project (CEAP). A major review of the importance of ephemeral and intermittent streams at the request of EPA in response to the 2006 Rapanos Supreme Court decisions as to whether these streams constitute �waters of the United States� under the Clean Water Act was completed. Significant Activities that Support Special Target Populations: In 2011/12, an undergraduate student of African-American descent worked with SWRC as a UA NASA Space Grant Intern to assess chlorophyll fluorescence for use as an indicator of crop growth efficiency. The results for her research showed chlorophyll fluorescence to be a good surrogate for photosynthetic efficiency and will contribute to plans for a satellite-based sensor to measure chlorophyll fluorescence over large agricultural areas. The undergraduate wrote an abstract describing her research results and presented the results (with a powerpoint presentation) at the Annual Statewide Space Grant Symposium. Accomplishments 01 New satellites map crop type and monitor crop and soil condition. For decades, satellite imagery has played a unique and important role in far management, but new satellites using radar technology promise even more information at 3-day frequency during day, night, and even under cloudy conditions. We found that the time-series data provided by recently launched radar sensors was suitable for distinguishing crop types, monitoring crop phenology, and capturing rapid changes in soil moisture condition. These results contribute to mission planning by providing information to balance the cost of additional sensor capabilities and th benefit to farm managers. These findings have been incorporated into the design of the European Space Agency Sentinel-1 mission for classifying a monitoring agricultural crops. 02 Cool-season performance of invasive and native grasses. Previous resear has suggested the success of introduced South African grasses in invadin Southwestern U.S. desert grasslands is their potential utilization of co season rains. Native perennial grasses are not thought to use cool-seaso rains, extensively. ARS scientists at the Southwest Watershed Research Center demonstrated, contrary to this expectation, that some native grasses were better able to sustain higher levels of whole plant carbon uptake, and had higher water use efficiency, during exceptionally wet winter/spring conditions associated with a Southern Oscillation/El Nino event than a highly successful South African invasive. These findings suggest that the invasive success of this grass is not supported by effective winter rain use. Predicted reductions in cool-season precipitation and increasing temperatures may facilitate the further spread and continued dominance of South African grasses across southwestern United States semi-desert grasslands.
Impacts
(N/A)
Publications
- Krishnan, P., Meyers, T., Scott, R.L., Kennedy, L., Heuer, M. 2012. Energy exchange and evapotranspiration over two temperate semi-arid grasslands in North America. Agricultural and Forest Meteorology. 153: 31-44.
- Blonquist, J., Montzka, S., Munger, J.W., Yakir, D., Desai, A., Dragoni, D. , Griffis, T., Monson, R., Scott, R.L., Bowling, D. 2011. The potential of carbonyl sulfide as a proxy for gross primary production at flux tower sites. Journal of Geophysical Research. 116: 1-18.
- Nearing, G., Moran, M.S., Scott, R.L. 2012. Coupling diffusion and maximum entropy models to estimate thermal inertia. Remote Sensing of Environment. 119:222-231.
- Cavanaugh, M.L., Kurc, S.A., Scott, R.L. 2011. Evapotranspiration partitioning in semiarid shrubland ecosystems: A two-site evaluation of soil moisture control on transpiration. Ecohydrology. 4:671-681.
- Chen, M., Zhuang, Q., Cook, D., Coulter, R., Pekour, M., Scott, R.L., Munger, J., Bible, K. 2011. Quantification of terrestrial ecosystem carbon dynamics in the conterminous United States combining a process-based biogeochemical model and MODIS and AmeriFlux data. Biogeosciences. 8:2665- 2688.
- Jackson, T.J., Bindlish, R., Cosh, M.H., Zhao, T., Starks, P.J., Bosch, D. D., Moran, M.S., Seyfried, M.S., Kerr, Y., Leroux, D., Goodrich, D.C. 2012. SMOS validation of soil moisture and ocen salinity (SMOS) soil moisture over watershed networks in the U.S. IEEE Transactions on Geoscience and Remote Sensing. 50:1530-1543.
- Snyder, K.A., Scott, R.L., Mcgwire, K. 2012. Multiple year effects of a biological control agent (Diorhabda carinulata) on Tamarix (saltcedar) ecosystem exchanges of carbon dioxide and water. Agricultural and Forest Meteorology. 164:161-169.
- Hamerlynck, E.P., Scott, R.L., Barron-Gafford, B., Cavanaugh, M.L., Moran, M.S., Huxman, T. 2012. Cool-season whole-plant gas exchange of exotic and native desert semiarid bunchgrasses. Plant Ecology. 213:1229�1239. DOI 10. 1007/s11258-012-0081-x.
- Cable, J., Barron-Gafford, G., Ogle, K., Pavao-Zuckerman, M., Scott, R.L., Williams, D., Huxman, T. 2012. Shrub encroachment alters sensitivity of soil respiration to temperature and moisture. Journal of Geophysical Research. 117:1-11.
- 5. Burba, G., Schmidt, A., Scott, R.L., Nakai, T., Kathilankal, J., Fratini, G., Hanson, C., Law, B., Mcdermitt, D., Eckles, R., Furtaw, M., Velgersdyk, M. 2012. Calculating CO2 and H2O eddy covariance fluxes from an enclosed gas analyzer using an instantaneous mixing ratio. Global Change Biology. 18:385-399.
- Yan, H., Wang, S., Billesbach, D., Oechel, W., Zhang, J., Meyes, T., Martin, T., Matamala, R., Baldocchi, D., Bohrer, G., Dragoni, D., Scott, R. L. 2012. Global estimation of evapotranspiration using a leaf area index- based surface energy and water balance model. Remote Sensing of Environment. 124:581-595. doi:10.1016/j.rse.2012.06.004.
|
Progress 10/01/10 to 09/30/11
Outputs
Progress Report Objectives (from AD-416) The existing project objectives (as given below) reflect the redirection towards quantification of climate change effects: 1. Develop methods and techniques for quantifying natural and anthropogenic induced ephemeral-channel runoff and subsequent recharge in cooperation with U.S. Geological Survey Tucson Science Center under current and projected climate scenarios. 2. Develop methods and techniques to quantify and predict water budgets of riparian ecosystems under current and projected climate scenarios through direct measurements of evaporation and plant transpiration and predict water savings by removal of invasive mesquite vegetation. 3. Develop methods and techniques to explicitly quantify the spatial and temporal distribution of vegetation, land use, and infiltration reduction using remotely sensed methods to improve prediction of basin scale semi- arid water budget components. Approach (from AD-416) Methods of investigation include field and laboratory experimentation, as well as the development and use of state-of-the-science watershed models and the use of remote sensing for watershed characterization. Satellite derived rainfall will be evaluated using raingages for large area rainfall estimation, the enhancement of recharge due to urbanization will be examined in adjacent, well instrumented, natural and residentially developed catchments. High-resolution remotely sensing and rainfall simulator experiments will be used to evaluate the capability to remote estimate infiltration rates on compacted and constructed surfaces common to development at the urban-rural interface. Remote spectral surface responses will be combined with energy balance models and radiative transfer theory to estimate surface water, carbon and energy fluxes based on observations from a network of five eddy-covariance and two Bowen ratio towers. A number of modeling components for the Automated Geospatial Watershed Assessment (AGWA) will be developed or enhanced to enable a more realistic representation of watershed processes and best management practices. AGWA will be migrated to both the internet and ARCGIS platforms to enhance usability and access. In addition we will quantify the physical mechanisms and component fluxes that are responsible for the observed ecosystem-scale water and CO2 fluxes. Scientists will carry out this research at sites located across both a riparian and an upland woody plant encroachment gradient. Continue existing research under objective #3, and add activities to develop methods and techniques to quantify and predict water budgets under current and projected climate scenarios through direct measurements of evaporation and plant transpiration, and predict water savings by removal of invasive mesquite vegetation. A number of important advances were made on all three of our objectives, which fall under NP211. Under Objective 1 the management unit (MU) continued its membership and regular participation with Upper San Pedro Partnership (USPP-http://www.usppartnership.com/) to provide it with research and technical assistance. In addition to on-going water cycle observations for the USPP the MU has worked on obtaining improved estimates of impervious area using MU research and high resolution remotely-sensed imagery. This information will be coupled with prior runoff modeling studies to refine the estimate of groundwater recharge resulting from urbanization. Under Objective 2 research results contradicted the commonly held hypothesis that there is a positive feedback between canopy cover and soil moisture that then explains the stability of woody vegetation distribution patterns - a key finding to understand desertification. Projected hotter, dryer weather should lead to increased riparian plant water use (ET) when access to groundwater is not limited. However, actual daily ET at studied field sites would remain largely unchanged due to constraining plant mechanisms, but the longer growing season will increase riparian plant water use. In the case of woody plant encroachment into arid and semiarid lands, the current paradigm that more ecosystem carbon sequestration would occur under such conditions was not supported as we found an increase in the release of CO2 due to enhanced soil microbial respiration. Under Objective 3 a new approach was developed to map soil moisture patterns over large areas using satellites coupled with models. Activities that support all 3 Objectives include MU scientists being awarded an EPA-RARE grant from EPA- Region 8 (Denver) to use AGWA for their watershed and management and cumulative impacts assessments, which will result in approximately $100, 000 being transferred to ARS. The large fires in Arizona and New Mexico prompted a request to the MU from an interagency fire science Burn Area Response team to conduct post-fire watershed assessments identifying places of increased flooding risk and targeting on-ground remediation efforts. An OECD travel fellowship was completed to Spain and an MU scientist continues to supervise a Univ. of Arizona Ph.D. student from Spain who matriculated at the UA as a result of a prior OECD travel fellowship to Spain. The unit hosted two colleagues from Kazakhstan who worked collaboratively on a Russian language web site and database which will utilize MU research to explore the effects of climate and soils on vegetation cover over roughly 60,000 square miles of rangeland in Kazakhstan. Significant Activities that Support Special Target Populations In 2010/11, an undergraduate student of African-American descent worked with SWRC in cooperation with the U.S. Arid-Land Agricultural Research Center in Maricopa, AZ as a UA NASA Space Grant Intern to assess the impacts of nitrogen application on early-season wheat growth related to soil water loss. The results from her research provided some guidance for crop nitrogen applications related to the rate of vegetative growth in wheat varieties, potentially reducing the amount of water lost by evaporation in the early growing season. The undergraduate wrote an abstract describing her research results and presented the results (with a powerpoint presentation) at the Annual Space Grant Statewide Symposium. Accomplishments 01 Quantifying the potential for vegetation change in arid and semiarid lan The distribution of post-storm soil moisture in arid lands is critical to understanding the feedback between moisture distribution and vegetati growth. Scientists at the Southwest Watershed Research Center found that root-zone soil moisture was significantly higher between shrubs than und shrubs, due largely to greater root density there. Results contradict th commonly held hypothesis that there is a positive feedback between canop cover and soil moisture that explains the stability of woody vegetation distribution patterns. These findings are key for modeling and managemen practices related to desertification because other mechanisms likely dominate the observed worldwide expansion of woody vegetation into arid and semiarid grasslands. 02 Riparian water use and climate change. Studies on the impacts of climat change on hydrology have focused on how changes in precipitation and temperature affect runoff, with less emphasis on how plant water use (evapotranspiration or ET), which is the dominant water loss from many arid and semiarid watersheds, will change. An ARS scientist at the Southwest Watershed Research Center along with university colleagues analyzed ET and weather data from three riparian sites located in a semiarid watershed in southern Arizona and developed a simple model to estimate future plant water use (ET) rates given climate model projectio Climate predictions for this region indicate that hotter and dryer weather conditions could increase plant water use, but actual ET rates a the studied field sites will remain largely unchanged due to plant mechanisms that constrain the loss of water from their leaves. However, the length of the growing season is projected to increase due to warmer temperatures and this will result in a greater annual riparian plant wat use. These findings of increased riparian water use may lead to greater groundwater deficits and decreased streamflow, further stressing water management institutions in semiarid regions. 03 A new approach for mapping soil moisture at the watershed scale. Satellite imagery can be used for landscape mapping. As part of a team effort, an ARS scientist at Tucson, AZ, merged satellite imagery with a Land Surface Model to increase the reliability of modeled soil moisture predictions at fine spatial resolutions. The approach utilized a method that enables calibrating the land surface models directly to satellite- based measurements in a way which simultaneously accounted for model parameter and measurement induced uncertainty. At resolutions finer than 100m x100m, the proposed algorithm predicted surface level soil mositure to within 4% volumetric water content 95% of the time. This result can a the U.S. Army in planning routes and transporting personnel and supplies to save fuel and avoid unsafe, wet soils. 04 Drought-induced vegetation change affects carbon exchange in semiarid grasslands. Severe drought can lead to a change in plant community structure, which, in turn, may yield differences in how water and carbon dioxide are cycled in ecosystems. Scientists at the Southwest Watershed Research Center studied how the exchange of carbon dioxide between the atmosphere and a grassland in southern Arizona responded to a severe drought. When the drought ended the native grass species were replaced b an invasive African grass. The grassland was a source of carbon dioxide the atmosphere during the drought and then became a sink when the drough ended and the exotic grass moved in. When another dry growing season occurred after the invasion, the grassland still took in more carbon tha was released to the atmosphere. This study shows that invasive species m lead to more carbon sequestration in certain ecosystems and environments 05 Woody encroachment affects soil carbon dioxide releases. Because carbon dioxide (CO2) released from bacterial decomposition in soils is a domina component of ecosystem carbon dynamics, it is important to quantify how temperature, moisture, and plant activity influence this CO2 release or uptake. Scientists at the Southwest Watershed Research Center used automated measurement systems to quantify soil respiration under shrubs, grasses, and bare soil in a semiarid grassland invaded by woody plants a related patterns of CO2 uptake or release to environmental conditions. T condition immediately adjacent to the measurements (microhabitat) dramatically influenced the results. CO2 released under the mesquite tre was much larger than under grasses or bare soil. CO2 release (respiratio was not influenced by temperature in the way predicted by a commonly-use theory. As woody plants continue to expand into former grasslands, the increased carbon uptake by the more productive ecosystems commonly found in these ecosystems may be partially negated or even entirely offset by the increased carbon losses from the soil. 06 Plant/soil interactions in southwestern U.S. savannah. Recent research has suggested that tree cover in savanna systems improves under-canopy soil moisture, sustaining higher biomass in these locations. However, da suggests under-canopy plant communities are dominated by plants with wel developed drought-tolerant traits. By coupling measurements of soil wate with whole-plant carbon and water fluxes, ARS scientists at the Southwes Watershed Research Center were able to show that understory soil water conditions, though less variable than between canopy spaces, were more limiting to plant carbon uptake. This finding suggests higher soil water under savanna tree canopies is very transient, and high plant densities these microhabitats follows a reduction in temperature and light stress due to shading for plants capable of tolerating prolonged dry conditions These findings are important in understanding controls to spatial patter of productivity common to semiarid savanna systems.
Impacts
(N/A)
Publications
- Hamerlynck, E.P., Mcauliffe, J.R. 2010. Growth and foliar d15N of a Mojave desert shrub in relation to soil hydrological dynamics. Journal of Arid Environments. 74:1569-1571.
- Scott, R.L., Hamerlynck, E.P., Jenerette, G.D., Moran, M.S., Barron- Gafford, G.A. 2010. Carbon dioxide exchange in a semidesert grassland responding through drought-induced vegetation change. Journal of Geophysical Research-[Biogeosciences]. 115: G03026.
- Brand, L.A., Stromberg, J.C., Goodrich, D.C., Dixon, M.D., Lansey, K., Kang, D., Brookshire, D.S., Cerasale, D.J. 2010. Projecting avian response to linked changes in groundwater and riparian floodplain vegetation along a dryland river: a scenario analysis. Ecohydrology. p. 1-13. doi: 10. 1002/eco.143.
- Yuan, W., Luo, Y., Liang, S., Yu, G., Niu, S., Stoy, P., Chen, J., Desai, A., Lindroth, A., Gough, C., Ceulemans, R., Arain, A., Bernhofer, C., Cook, B., Cook, D., Dragoni, D., Gielen, B., Janssens, I., Longdoz, B., Liu, H., Lund, M., Matteucci, G., Moors, E., Scott, R.L., Seufert, G., Varner, R. 2011. Thermal adaptation of net ecosystem exchange. Biogeosciences. 8:1453-1463.
- Serrat-Capdevila, A., Scott, R.L., Shuttleworth, W.J., Valdez, J.B. 2011. Estimating evapotranspiration under warmer climates: Insights from a semiarid riparian system. Journal of Hydrology. 399: 1-11.
- Moran, M.S., Hamerlynck, E.P., Scott, R.L., Keefer, T.O., Bryant, R.B., Deyoung, L., Nearing, G.S., Sugg, Z., Hymer, D.C. 2010. Hydrologic response to precipitation pulses under and between shrubs in the Chihuahuan Desert, Arizona. Water Resources Research. 46: W10509. doi:10. 1029/2009WR008842.
- Nearing, G.S., Moran, M.S., Thorp, K.R., Holifield Collins, C.D., Slack, D. C. 2010. Likelihood parameter estimation for calibrating a soil moisture using radar backscatter. Remote Sensing of Environment. 114: 2564-2574.
- Jackson, T.J., Cosh, M.H., Bindlish, R., Starks, P.J., Bosch, D.D., Seyfried, M.S., Goodrich, D.C., Moran, M.S. 2010. Validation of advanced microwave scanning radiometer soil moisture products. IEEE Transactions on Geoscience and Remote Sensing. 48:4256-4272.
- Hamerlynck, E.P., Scott, R.L., Moran, M.S., Huxman, T.E. 2010. Inter - and under- canopy soil water, leaf-level and whole-plant gas exchange of a semiarid perennial C4 grass. Oecologia. 165: 17-29.
- Nagler, P.L., Shafroth, P.B., Labaugh, J.W., Snyder, K.A., Scott, R.L., Merritt, D.M., Osterberg, J. 2010. The potential for water savings through the control of saltcedar and russian olive. In: Shafroth, P.B., Brown, C.A. , Merritt, D.M., editors. Saltcedar and Russian Olive Control Demonstration Act Science Assessment. USGS Scientific Investigations Report 2009-5247. p. 35-47.
- Fathelrahman, E.M., Ascough II, J.C., Hoag, D.L., Malone, R.W., Heilman, P. , Wiles, L., Kanwar, R.S. 2011. Continuum of risk analysis methods to assess tillage system sustainability at the experimental plot level. Sustainability. 3(7):1035-1063. DOI:10.3390/su3071035.
- Gilmanov, T.G., Aires L., Barcza, Z., Baron, V., Belelli, L., Beringer, J., Billesbach, D., Bonal, D., Bradford, J., Ceschia, E., Cook, D., Corradi, C., Frank, A.T., Gianelle, D., Gimeno, C., Grunwald, T., Gao, H., Hanan, N. , Haszpra, L., Heilman, J., Jacobs, A., Jones, M., Johnson, D., Kiely, G., Li, S., Magliulo, V., Moors, E., Nagy, Z., Nasyrov, M., Owensby, C., Pinter, K., Pio, C., Reichstein, M., Sanz, M., Scott, R.L., Soussana, J., Stoy, P.C., Svejcar, A.J., Tuba, Z., Zhou, G. 2010. Productivity, respiration, and light-response parameters of world grassland and agroecosystems derived from flux-tower measurements. Rangeland Ecology and Management. 63:16-39.
- Xiao, J., Zhuang, Q., Law, B.E., Baldocchi, D.D., Chen, J., Richardson, A. D., Melillo, J.M., Davis, K.J., Hollinger, D.Y., Wharton, S., Oren, R., Noormets, `., Fischer M., L., Verma, S.B., Cook, D.R., Sun, G., Mcnulty, S. , Wofsy, S.C., Bolstad, P.V., Burns, S.P., Curtis, P.S., Drake, B.G., Falk, M., Foster, D.R., Gu, L., Hadley, J.L., Katul, G.G., Litvak, M., Ma, S., Martin, T.A., Matamula, R., Meyers, T.P., Monson, R.K., Munger, J.W., Oechel, W.C., Tha Paw, U.K., Schmid, H.P., Scott, R.L., Starr, G., Suyker, A.E., Torn, M.S. 2010. Assessing net ecosystem carbon exchange of U.S. terrestrial ecosystems by integrating eddy covariance flux measurements and satellite observations. Agricultural and Forest Meteorology. 151: 60- 69.
- Barron-Gafford, G., Scott, R.L., Jenerette, G., Huxman, T. 2011. The relative controls of temperature, soil moisture, and plant functional group on soil CO2 efflux at diel, seasonal, and annual scales. Journal of Geophysical Research. 116:1-16.
|
Progress 10/01/09 to 09/30/10
Outputs
Progress Report Objectives (from AD-416) The existing project objectives (as given below) reflect the redirection towards quantification of climate change effects: 1. Develop methods and techniques for quantifying natural and anthropogenic induced ephemeral-channel runoff and subsequent recharge in cooperation with U.S. Geological Survey Tucson Science Center under current and projected climate scenarios. 2. Develop methods and techniques to quantify and predict water budgets of riparian ecosystems under current and projected climate scenarios through direct measurements of evaporation and plant transpiration and predict water savings by removal of invasive mesquite vegetation. 3. Develop methods and techniques to explicitly quantify the spatial and temporal distribution of vegetation, land use, and infiltration reduction using remotely sensed methods to improve prediction of basin scale semi- arid water budget components. Approach (from AD-416) Methods of investigation include field and laboratory experimentation, as well as the development and use of state-of-the-science watershed models and the use of remote sensing for watershed characterization. Satellite derived rainfall will be evaluated using raingages for large area rainfall estimation, the enhancement of recharge due to urbanization will be examined in adjacent, well instrumented, natural and residentially developed catchments. High-resolution remotely sensing and rainfall simulator experiments will be used to evaluate the capability to remote estimate infiltration rates on compacted and constructed surface common to development at the urban-rural interface. Remote spectral surface responses will be combined with energy balance models and radiative transfer theory to estimate surface water, carbon and energy fluxes based on observations from a network of five eddy-covariance and two Bowen ratio towers. A number of modeling components for the Automated Geospatial Watershed Assessment (AGWA) will be developed or enhanced to enable a more realistic representation of watershed processes and best management practices. AGWA will be migrated to both the internet and ARCGIS platforms to enhance usability and access. In addition we will quantify the physical mechanisms and component fluxes that are responsible for the observed ecosystem-scale water and CO2 fluxes. Scientists will carry out this research at sites located across both a riparian and an upland woody plant encroachment gradient. Continue existing research under objective #3, and add activities to develop methods and techniques to quantify and predict water budgets under current and projected climate scenarios through direct measurements of evaporation and plant transpiration, and predict water savings by removal of invasive mesquite vegetation. A number of important advances were made in quantifying the changes in climate, plant, water, and carbon cycle interactions as a result of invasive species encroachment. In the first case, Lehmann Lovegrass invaded portions of the ARS Walnut Gulch Experimental Watershed due to a long-term drought. Carbon uptake and the ratio of post-storm evaporation to evapotranspiration was significantly altered due to the difference in plant structural form and its ability to more rapidly use seasonal rainfall for growth. In the case of observed worldwide woody plant encroachment into arid and semiarid grasslands, the current paradigm that more ecosystem carbon sequestration would occur was found to be incorrect for two grasslands being invaded by mesquite in southeast Arizona. This ecosystem was a found to be a source of carbon to the atmosphere in which carbon release increased with drought severity. All of these findings will provide critical information on how ecosystems will respond and possibly adapt to climate change and other stresses. Advances were also made in the ability of satellites to provide information about crop type, phenology and water status using a large number of radar images. The MU is taking a leadership role in formulation of the AGAVES (Assessment of Goods And Valuation of Ecosystem Services) interagency program and hosted an AGAVES meeting in January. Work continued on the rangeland portion of the congressionally mandated NRCS Conservation Effects Assessment Project (CEAP) including two briefings to NRCS senior management and input to the NRCS Resource Conservation Assessment (RCA) report. Validation of the nitrogen and phosphorous components of the coupled ARS models (KINEROS2 and OPUS; now K2-O2) was completed and a significant number of presentations, posters, proceedings paper and computer demonstration for K2-O2 and the Automated Geospatial Watershed Assessment (AGWA) tool were presented at the Federal Interagency Hydrologic Modeling Conference. The MU has continued its membership with the Congressionally recognized Upper San Pedro Partnership (USPP) (http://www.usppartnership.com/) to provide it with research and technical assistance. The MU monitored and calculated improved estimates of groundwater recharge from infiltration into flood detention ponds for the USPP. On the international front an OECD travel fellowship was completed to Spain and another was awarded for Spain for FY11. Cooperative work with Kazakhstan was presented at a NASA meeting and will continue as a result of a two year extension of funding for this project. Two new interagency agreements were initiated this fiscal year with the National Park Service and the EPA. Both involve training and use of AGWA for their watershed and management and permitting needs. Significant Activities that Support Special Target Populations In 2009/10, undergraduate student Maxwell Justice (Native American descent) worked with SWRC as a UA NASA Space Grant Internship to aid in assessing the use of computer models for simulating crop growth. The results from Max�s research were a very good contribution to our ongoing research and have influenced the ongoing direction of our work. Max wrote an abstract describing his research results and presented the results (with a powerpoint presentation) at the Annual Space Grant Statewide Symposium. SWRC scientists are heavily involved in the NSF Sustainability of semiArid Hydrology and Riparian Areas (SAHRA) Science and Technology Center. This program has a very active program in outreach and education of Native American communities to increase hydrologic awareness career opportunities in science. Accomplishments 01 Invasive grasses altered the water cycle in semiarid rangeland. This stu investigated a transition from a grassland dominated by native species t a non-native Lehmann lovegrass monoculture at a semiarid grassland site southeastern Arizona. Results from ARS scientists in Tuscon, AZ, showed that the post-storm daily water loss due to soil evaporation (E) [relati to the daily evapotranspiration from plants and soil (ET)] was greater i post-transition years than in pre-transition years. Results indicated that, compared to a native assemblage, Lehmann lovegrass dominance may b associated with an increase in the ratio of ED/ETD after precipitation i the summer growing season. Over the season, this resulted in a doubling of total seasonal ratio of E/ET after the Lehmann lovegrass invasion. These results will contribute to a comprehensive understanding of the impacts of species invasion in semiarid grasslands. 02 Monetary Valuation of Riparian Ecosystem Services: Conservation of freshwater systems is critical in the semi-arid Southwest where these systems are in high demand for competing human and environments uses. To address this conflict, natural scientists must evaluate how human associated changes to hydrologic regimes alter ecological systems. In th study the ARS scientists in Tuscon, AZ, and a multi-institutional team have developed a hydro-bio-economic framework for the San Pedro River Region in Arizona, and the Middle Rio Grande of New Mexico. Studies are being conducted for each site to examine how well values established at one site can be transferred to the other site. This system will transla management decisions into changes in ecosystem attributes which can be monetized providing a scientifically defensible management methodology housed within a easy to use Decision Support System. This will provide resource managers and decision makers with a suite of monetized ecosyste services values that heretofore have not been available for use in assessing trade-offs against costs for management and planning. 03 Drought Effects on Water and Carbon Cycling in a Desert Grassland Invade by Mesquite. The increase in the amount of woody plants (shrubs and tree enroaching into grassland ecosystems is one of the most wide-spread changes to ecosystems in the Southwestern U.S. This will affect water an nutrient cycling of these ecosystems. ARS scientists in Tuscon, AZ, measured water and carbon dioxide exchange between a woody-plant- encroached grassland and the atmosphere over a four-year period and determined how the amount of precipitation influenced these exchanges. W found that seasonal drought during this period strongly impacted these exchanges. In contrast to the current model that woody plant encroachme might result in more ecosystem carbon sequestration, we found that this ecosystem was a source of carbon to the atmosphere which increased with drought severity. These results highlight a complex relationship between vegetation change and climatic variation in precipitation that likely influences the carbon sequestration potential of these water-limited landscapes. 04 Invasive grass and grassland function. The invasive success of the Sout African grass, Lehmann lovegrass has been associated with a dramatic decrease in the diversity of native plant and animal populations, and is of considerable concern to land-managers across the arid and semi-arid Southwest. In co-operation with University of Arizona colleagues, ARS scientists in Tuscon, AZ, showed plots dominated by Lehmann lovegrass ha higher soil water contents across the summer monsoon growing season, whi resulted in higher seasonal evapotranspiration and greater carbon uptake activity compared to native grasses. These differences followed more rapid canopy development and allocation to leaf area display, indicating the invasive success of this exotic grass is due to rapid use of seasona rains, thereby altering the tempo of basic ecosystem functioning in semiarid rangelands. Understanding these functional characteristics is important in efforts to control and manage the ecosystem-service consequences of this grass in important rangeland systems 05 Woody Shrubs in Western U.S. alter the spatial distribution of moisture the soil. Because water is vital to life on this planet, knowing the amount of moisture in the soil is important for predicting the response plants in natural ecosystems to global warming, increases in atmospheric carbon dioxide, and changing land-use patterns. Dry lands worldwide are currently experiencing an increase in the density and cover of woody plants, which in turn influence the availability of soil moisture, with potentially important effects on local and regional water cycles. ARS scientists in Tuscon, AZ, monitored soil moisture at a semiarid savanna near Tucson, AZ to determine the effect that the trees had on the amount of soil moisture in the soil. We found that the tree canopy reduced the amount of precipitation input into the soil, but also that the shade of the canopy had the tendency to reduce evaporative losses so that the soi dried less quickly than soil out in the open. These findings are consistent with, and may help to explain, the results of other investigations that have examined the role of woody plants in enhancing nutrient cycling and altering carbon cycling in arid ecosystems. 06 The accuracy of evaporation measurements. Measurements of evaporation ov land are critical for determining local, regional and global hydrologica budgets, model testing, and understanding ecosystem processes. This stu conducted by ARS scientists in Tuscon, AZ, evaluated the accuracy of evaporation measurements made using a very common, state-of-the-art meteorological technique by comparing them with evaporation estimates derived from a seasonal or annual water balance over nearly twelve years and at three sites in Arizona, USA. Results indicate that the widely use technique resulted in estimates that were highly accurate, giving confidence to the accuracy of this type of data collected at sites worldwide. 07 Satellites provide information about crop type, seasonal changes in plan structure and water status. A time-series of 57 radar images of irrigat agriculture in La Mancha, SE Spain acquired by ARS scientists in Tuscon, AZ, in 2009 was used to assess the sensitivity of radar backscatter to crop and soil conditions for large fields of corn, barley, wheat, onion, alfalfa and oats. Preliminary results showed that radar backscatter detected by the satellite sensor was sensitive to 1) crop type, 2) crop seasonal growth and harvest date, 3) crop furrow size and orientation, a 4) soil moisture due to precipitation or irrigation. The multiple radar configurations and multi-date imagery were essential to discriminating this interrelated information. This information, derived from satellite images, provides distributed input for crop growth models for day-to-day crop management. 08 Riparian ecosystem carbon cycling. Identifying the dynamics of carbon dioxide cycling in ecosystems in semiarid regions will lead to the abili to better assess the ecological responses to future changes in climate. To make reliable predictions to change, scientists need to construct models that adequately represent and characterize how carbon dioxide exchange is influenced by weather, plant type and activity, and water availability. ARS scientists in Tuscon, AZ, developed a relatively simpl computer model that is based on established theory and then applied this model at two sites in southern Arizona where measurements of carbon dioxide exchange have been made. We demonstrate that this model adequate reproduces the measurements, and we found that ecosystem carbon cycling was equal to or even more affected by the ecosystem composition than climate variation. This indicates a need to consider an ecosystem�s uniq plant composition when determining the carbon sequestration potential of riparian landscapes. 09 Regional drought effects. The Southwest U.S. has experienced record drought intensity from 1999 to 2005. Prolonged droughts such as these a important ecological disturbances in deserts, resulting in widespread plant mortality that alters plant community structure and ecosystem functioning that can persist over very long time scales. Using continuously recorded monthly precipitation totals across 35 years and 6 weather stations, ARS scientists in Tuscon, AZ, found that higher whole- plant mortality and more extensive canopy die back in Sonoran Desert shr populations was due to repeated failures of cool-season precipitation; these did not occur to as great an extent in the Mojave Desert, where rainfall accumulations are typically much lower than across the Sonoran. The biological diversity of Southwest U.S. deserts is of considerable aesthetic and commercial economic importance, and this research is important in that it shows which plant species are susceptible to severe drought-induced mortality, and establishes the mechanisms and long-term consequences of these community shifts across the region. 10 Improved forest carbon modeling. Changing global climate conditions hav been predicted to increase the frequency and severity of disturbances su as hurricanes, ice-storms and insect outbreaks capable of dramatically altering forest canopy structure. Despite the importance of these disturbances, few forest carbon models directly incorporate canopy microclimate and structure into their operating parameters. In co- operation with a USDA Forest Service scientist, ARS scientists in Tuscon AZ, compared the carbon balance of an oak/pine forest estimated with a canopy-constrained carbon assimilation model (the 4C-A model) to whole ecosystem net carbon exchange (NEE) measured directly with instrumentati prior to and following severe defoliation by gypsy moth. 4C-A carbon balance estimates were 10% of directly measured NEE, and successfully captured the switch in the forest functioning as a carbon sink to being carbon source following defoliation. Thus, the 4C-A model provides a valuable tool to assess short- and long-term consequences of canopy disturbance to forest carbon balance dynamics, allowing for better prediction of novel, climate-induced disturbance regimes to the carbon sequestration ability of forested systems. 11 Carbon and Water Use for Tropical Deciduous Forest. The North American Monsoon (NAM) dominates summer climate and is responsible for providing the majority of rainfall over a large portion of western North America. Knowing how ecosystems respond to these seasonal rains is critical to understanding how surface vegetation may affect monsoon intensity. To better understand the effects and relationship between precipitation, carbon sequestration and evaporation, ARS scientists in Tuscon, AZ, made measurements of these exchanges over a little studied tropical dry fores in northwest Mexico. Three markedly defined periods were found during th six-month study period: 1) A pre-rainy season period, where carbon and water exchange was close to zero; 2) A monsoon period characterized by relatively large evaporation losses and large carbon uptake; and, 3) A post-rainy season where the ecosystem returned to dormancy. Because of t strength of the monsoon in this type of ecosystem these forests can take up a large amount of carbon dioxide from the atmosphere in a relatively short period of time.
Impacts
(N/A)
Publications
- Shuttleworth, W.J., Serrat-Capdevila, A., Roderick, M.L., Scott, R.L. 2009. ON THE THEORY RELATING CHANGES IN AREA-AVERAGE AND PAN EVAPORATION. Quarterly Journal Royal Meteorological Society. 135: 1230-1247. doi: 10. 1002/qj.434
- Scott, R.L., Jenerette, G., Potts, D., Huxman, T. 2009. Effects of seasonal drought on net carbon dioxide exchange. JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 114: 1-13. G04004.
- Schaffner, M., Unkrich, C.L., Goodrich, D.C. 2010. Application of The KINEROS2 Site Specific Model to South-Central NY and Northeast PA: Forecasting Gaged and Ungaged Fast Responding Watersheds. NWS Eastern Region Technical Attachment No. 2010-01. (http://www.erh.noaa. gov/er/hq/ssd/erps/ta/ta2010-01.pdf). . Popular Publication.
- Hamerlynck, E.P., Scott, R.L., Moran, M.S., Keefer, T.O., Huxman, T.E. 2010. Growing season ecosystem and leaf-level gas exchange of an exotic and native semiarid bunchgrass. Oecologia. 163:561�570.
- Moran, M.S., Scott, R.L., Hamerlynck, E.P., Green, K.N., Emmerich, W.E., Holifield Collins, C.D. 2009. Soil Evaporation Response to Lehmann Lovegrass (Eragrostis lehmanniana) Invasion in a Semiarid Watershed. Agricultural and Forest Meteorology. 149:2133-2142.
- Mcauliffe, J.R., Hamerlynck, E.P. 2010. Perennial plant mortality in the Sonoran and Mojave Deserts in response to severe, multi-year drought. Journal of Arid Environments. 74:885-896.
- Entekhabi, D., Njoku, E.G., O'Neill, P.E., Kellogg, K.H., Crow, W.T., Edelstein, W.N., Entin, J.K., Goodman, S.D., Jackson, T.J., Johnson, J., Kimball, J., Peipmeier, J.R., Koster, R.D., McDonald, K.C., Moghaddam, M., Moran, M.S., Reichle, R., Shi, J.C., Spencer, M.W., Thurman, S.W. 2009. The Soil Moisture Active and Passive (SMAP) Mission. Proceedings of the IEEE. 98(5):704-716.
- Jenerette, G.D., Scott, R.L., Barron-Gafford, G.A., Huxman, T.E. 2009. Gross primary production variability associated with meteorology, physiology, leaf area, and water supply in contrasting woodland and grassland semiarid riparian ecosystems. Journal of Geophysical Research. 114: G04010. doi:10.1029/2009JG001074.
- Xiao, J., Zhuang, Q., Law, B.E., Chen, J., Baldocchi, D.D., Cook, D.R., Oren, R., Richardson, A., Wharton, S., Ma, S., Martin, T., Verma, S., Suyker, A., Scott, R.L., Monson, R., Litvak, M., Hollinger, D., Sun, G., Bolstad, P., Burns, S., Curtis, P., Drake, B., Falk, M., Fischer, M., Foster, D., Gu, L., Hadley, J., Katul, G., Matamala, R., Mcnulty, S., Meyers, T., Munger, J.W., Noormets, A., Oechel, W., Paw U, K., Schmid, H.P. , Starr, G., Torn, M., Wofsy, S. 2010. A Continuous Measure of Gross Primary Production for the Conterminous U.S. Derived from MODIS and AmeriFlux Data. Remote Sensing of Environment. 114:576-591.
- Potts, D.L., Scott, R.L., Bayram, S., Carbonara, J. 2010. Woody plants modulate the temporal dynamics of soil moisture in a semi-arid mesquite savanna. Ecohydrology. 3:20-27.
- Jenerette, G.D., Scott, R.L., Huete, A.R. 2010. Functional differences between summer and winter season rain assessed with MODIS derived phenology in a semi-arid region. Journal of Vegetation Science. 21:16-30.
- Schafer, K.V., Clark, K.L., Skowronski, N., Hamerlynck, E.P. 2010. Impact of insect defoliation on forest carbon balance as assessed with a canopy assimilation model. Global Change Biology. 16:546-560.
- Scott, R.L. 2010. Using watershed water balance to evaluate the accuracy of eddy covariance evaporation measurements for three semiarid ecosystems. Agricultural and Forest Meteorology. 150:219-225.
- Lizarraga-Celaya, C., Watt, C., Rodriguez, J., Garatiza-Payan, J., Scott, R.L., Saiz-Hernandez, J. 2010. Spatio-temporal variations in surface characteristics over the North American Monsoon region. Journal of Arid Environments. 74:540-548.
- Perez-Ruiz, E., Garatuza-Payan, J., Watt, C., Rodriguez, J., Yepez, E., Scott, R.L. 2010. Carbon dioxide and water vapour exchange in a tropical dry forest as influenced by the North American Monsoon System (NAMS). Journal of Arid Environments. 74: 556-563.
- Brookshire, D.S., Goodrich, D.C., Dixon, M.D., Brand, A., Benedict, K., Lansey, K., Thacher, J., Broadbent, J., Stewart, S., Mcintosh, M., Doosun, K. 2010. Ecosystem Services and Reallocation Choices: A Framework for Preserving Semi-Arid Regions in the Southwest. Journal of Contemporary Water Research and Education. 144:60-74.
|
Progress 10/01/08 to 09/30/09
Outputs
Progress Report Objectives (from AD-416) 1. Quantify, and provide tools to estimate the impacts of urban development on the urban-rural interface as it affects surface runoff and groundwater recharge. 2. Develop improved watershed model components and decision support systems that more fully utilize and assimilate economic and remotely sensed data for parameterization, calibration, and model state adjustment. 3. Quantify primary semiarid water and energy balance components with emphasis on determining how surface processes and states influence water fluxes over a range of primary semi-arid ecosystem types. Improve the ability to manage watersheds for reliable water supply, water quality, and ecosystem health by improving the ability to quantify semiarid water budget components. Approach (from AD-416) Methods of investigation include field and laboratory experimentation, as well as the development and use of state-of-the-science watershed models and the use of remote sensing for watershed characterization. Satellite derived rainfall will be evaluated using raingages for large area rainfall estimation, the enhancement of recharge due to urbanization will be examined in adjacent, well instrumented, natural and residentially developed catchments. High-resolution remotely sensing and rainfall simulator experiments will be used to evaluate the capability to remote estimate infiltration rates on compacted and constructed surface common to development at the urban-rural interface. Remote spectral surface responses will be combined with energy balance models and radiative transfer theory to estimate surface water, carbon and energy fluxes based on observations from a network of five eddy-covariance and two Bowen ratio towers. A number of modeling components for the Automated Geospatial Watershed Assessment (AGWA) will be developed or enhanced to enable a more realistic representation of watershed processes and best management practices. AGWA will be migrated to both the internet and ARCGIS platforms to enhance usability and access. In addition we will quantify the physical mechanisms and component fluxes that are responsible for the observed ecosystem-scale water and CO2 fluxes. Scientists will carry out this research at sites located across both a riparian and an upland woody plant encroachment gradient. Continue existing research and add activities to develop methods and techniques to quantify and predict water budgets under current and projected climate scenarios through direct measurements of evaporation and plant transpiration, and predict water savings by removal of invasive mesquite vegetation. FY09 Program Increase $228,600. Significant Activities that Support Special Target Populations A number of important advances were made in plant water use and its interaction with carbon cycling which have important implications for plant response to global climate change. As noted last year, portions of our Walnut Gulch Experimental Watershed were overtaken by invasive Lehmann Lovegrass due to a long-term drought. In the transitional year between native and lovegrass-dominated plant communities, extensive ephemeral forb cover resulted in higher runoff velocities and the first measureable erosion in over 20 years. Subsequent spread by lovegrass has more than doubled soil water evaporation over the growing season, likely due to differences in lovegrass structure, which has dramatically lower basal area compared to the native grasses it replaced. Data from our ecosystem water and carbon flux monitoring stations was used to better understand the response from a variety of semiarid ecosystems to monsoon rainfall. Advances were also made in a multi-institutional research effort to assess the market value of ecosystem services. Work continued on the rangeland portion of the NRCS Conservation Effects Assessment Project (CEAP). Substantial progress was made within the MU in planning and conducting field experiments and research for this effort. Initial coupling of two well known ARS models (KINEROS2 and OPUS) was completed and testing is currently underway. The resulting couple model will be able to address a wider range of water quality, agriculture and land management practices, and nutrient cycling, including carbon. The coupled model will then be incorporated into the Automated Geospatial Watershed Assessment (AGWA) tool to facilitate its ease of use and application. The climate assessment tool developed under the companion Erosion project within the MU was also incorporated into AGWA enabling assessments of watershed impacts from generalized global climatic changes (AGWA was awarded a 2008 ARS Technology Award). Other significant technology transfer undertaken involved development of a major review of the importance of ephemeral and intermittent streams at the request of EPA in response to recent Supreme Court decisions as to whether these streams constitute �waters of the United States� under the Clean Water Act. The MU has continued its membership with the Congressionally recognized Upper San Pedro Partnership (USPP) (http://www.usppartnership. com/) to provide it with research and technical assistance. Research results from the MU supplied improved estimates of runoff increases resulting from urbanization. The USPP and all of its member agencies were awarded the 2008 U.S. Dept. of Interior�s Cooperative Conservation Award. On the international front an OECD travel fellowship was completed in New Zealand and another was awarded for Spain for FY10. Cooperative work with Kazakhstan continued. The MU was also quite successful in obtaining extramural grants either directly to the MU or to university collaborators in which MU scientists are Co-Investigators. Two awards were received from NASA, one from the NOAA COMET program; and one from the DOD Strategic Environmental Research and Development Program (SERDP). Significant Activities that Support Special Target Populations SWRC scientists are actively participating in a mentoring program through collaboration with the University of Arizona/NASA Space Grant Program. The program matches outstanding undergraduate students from underrepresented groups with mentors from the SWRC to work together on projects developed by mentors. The ultimate goal of the program is to "grow our own" scientists from underrepresented groups. Over the last five years, twelve students (Hispanic, African-American, women) have come through the program. ARS researcher completed her Masters of Science in the School of Natural Resources at the University of Arizona. SWRC scientist served as a co- advisor for her research. SWRC scientists and another researcher mentored two female undergraduates in environmental research during the summer of 2009. The undergraduates were recipients of a National Science Foundation�s Research Experience for Undergraduates fellowships through the University of Arizona. SWRC scientists are heavily involved in the NSF Sustainability of semiArid Hydrology and Riparian Areas (SAHRA) Science and Technology Center. This program has a very active program in outreach and education of Native American communities to increase hydrologic awareness career opportunities in science. Technology Transfer Number of Web Sites managed: 4 Number of Other Technology Transfer: 3
Impacts
(N/A)
Publications
- Vivoni, E.R., Moreno, H.A., Mascaro, G., Rodriguez, J.C., Watts, C.J., Garatuza-Payan, J., Scott, R.L. 2008. Observed relation between evapotranspiration and soil moisture in the North American monsoon region. Geophysical Research Letters. 35, L22403. doi:10.1029/ 2008GL036001.
- Zreda, M., Desilets, D., Ferre, T., Scott, R.L. 2008. Measuring soil moisture content non-invasively at intermediate spatial scale using cosmic- ray neutrons. Geophysical Research Letters, 35, L21402. doi:10. 1029/2008GL035655.
- Jennerette, G.D., Scott, R.L., Huxman, T.E. 2008. Whole ecosystem metabolic pulses following precipitation events. Functional Ecology. 22:924-930. doi: 10.1111/j.1365-2435.2008.01450.x
- Moran, M.S., Scott, R.L., Keefer, T.O., Emmerich, W.E., Hernandez, M., Nearing, G.S., Paige, G.B., Cosh, M.H., O'Neill, P.E. 2009. Partitioning evapotranspiration in semiarid grassland and shrubland ecosystems using time series of soil surface temperature. Agricultural and Forest Meteorology. 149:59-72.
- Hamerlynck, E.P., Huxman, T.E. 2009. Ecophysiology of two Sonoran Desert evergreen shrubs during extreme drought. Journal of Arid Environments. 73: 582-585.
- Xiao, J., Zhuang, Q., Baldocchi, D., Law, B., Richardson, A., Chen, J., Oren, R., Starr, G., Noormets, A., Ma, S., Verma, S., Wharton, S., Wofsy, S., Bolstad, P., Burns, S., Cook, D., Curtis, P., Drake, B., Falk, M., Fishcer, M., Foster, D., Gu, L., Hadley, J., Hollinger, D., Katul, G., Litvak, M., Martin, T., Matamala, R., Mcnulty, S., Meyers, T., Monson, R., Munger, J., Oechel, W., Paw U, K., Schmid, H., Scott, R.L., Sun, G., Suyker, A., Torn, M. 2008. Estimation of Net Ecosystem Carbon Exchange for the Conterminous United States by Combining MODIS and AmeriFlux Data. Agricultural and Forest Meteorology. 148:1827-1847.
- Potts, D.L., Scott, R.L., Cable, J.M., Huxman, T.E., Williams, D.G. 2008. Sensitivity of mesquite shrubland CO2 exchange to precipitation in contrasting physiographic settings. Ecology. 89(10):2900�2910.
- Williams, D., Scott, R.L. 2009. VEGETATION-HYDROLOGY INTERACTIONS: DYNAMICS OF RIPARIAN PLANT WATER USE. In: Ecology and Conservation of the San Pedro River. Ed. by J. C. Stromberg and B. J. Tellman. Tucson: University of Arizona Press. p. 37-56.
- Stromberg, J., Dixon, M.D., Scott, R.L., Maddock, T., Baird, K., Tellman, B. 2009. Status of the Upper San Pedro River (United States) Riparian Ecosystem. In: Ecology and Conservation of the San Pedro River. Ed. by J. C. Stromberg and B. J. Tellman. Tucson: University of Arizona Press. p.371- 387.
- Hamerlynck, E.P., Mcauliffe, J.R. 2008. Soil-dependent canopy-die back and plant mortality in two Mojave Desert shrubs. Journal of Arid Environments. 72:1793� 1802. . Journal of Arid Environments.
- Cosh, M.H., Jackson, T.J., Moran, M.S., Bindlish, R. 2008. Temporal persistence and stability of surface soil moisture in a semi-arid watershed. Remote Sensing of Environment. 112:304-313.
- Scott, R.L., Huxman, T.E., Williams, D.G., Hultine, K.R., Goodrich, D.C. 2008. Quantifying Riparian Evapotranspiration. Southwest Hydrology. 7(1): 26-27.
- Richter, H., Goodrich, D.C., Browning-Aiken, A., Varady, R. 2009. CHAPTER 9: INTEGRATING SCIENCE AND POLICY FOR WATER MANAGEMENT. In: Ecology and Conservation of the San Pedro River. Ed. by J. C. Stromberg and B. J. Tellman. Tucson: University of Arizona Press. p. 388-408.
- Semmens, D.J., Goodrich, D.C., Unkrich, C.L., Smith, R.E., Woolhiser, D.A., Miller, S.N. 2008. KINEROS2 and the AGWA Modeling Framework. Chapter 5: In Hydrological Modelling in Arid and Semi-Arid Areas (H. Wheater, S. Sorooshian, and K. D. Sharma, Eds.). Cambridge University Press, London. Pp. 49-69.
|
Progress 10/01/07 to 09/30/08
Outputs
Progress Report Objectives (from AD-416) Quantify primary semiarid water and energy balance components with emphasis on rainfall, storm water recharge, and evapotranspiration. Develop improved watershed model components and decision support systems that more fully utilize and assimilate economic and remotely sensed data for parameterization, calibration, and model state adjustment. Quantify ecosystem influence and feedbacks on water fluxes and states over a selected range of arid and semiarid primary vegetation types. Approach (from AD-416) Methods of investigation include field and laboratory experimentation, as well as the development and use of state-of-the-science watershed models and the use of remote sensing for watershed characterization. Satellite derived rainfall will be evaluated using raingages for large area rainfall estimation, the enhancement of recharge due to urbanization will be examined in adjacent, well instrumented, natural and residentially developed catchments. High-resolution remotely sensing and rainfall simulator experiments will be used to evaluate the capability to remote estimate infiltration rates on compacted and constructed surface common to development at the urban-rural interface. Remote spectral surface responses will be combined with energy balance models and radiative transfer theory to estimate surface water, carbon and energy fluxes based on observations from a network of five eddy-covariance and two Bowen ratio towers. A number of modeling components for the Automated Geospatial Watershed Assessment (AGWA) will be developed or enhanced to enable a more realistic representation of watershed processes and best management practices. AGWA will be migrated to both the internet and ARCGIS platforms to enhance usability and access. In addition we will quantify the physical mechanisms and component fluxes that are responsible for the observed ecosystem-scale water and CO2 fluxes. Scientists will carry out this research at sites located across both a riparian and an upland woody plant encroachment gradient. Formerly 5342- 13610-007-00D (12/06). Significant Activities that Support Special Target Populations FY2008 was a banner year for the MU as the culmination of a multi-year effort was realized with the publication of a special section of 20 papers in Water Resources Research, one of the premier journals in hydrology, describing and analyzing over 50 years of data (precipitation, runoff, sediment, weather, soil moisture, vegetation, carbon and water flux, remote sensing, and geographic data) collected at the USDA-ARS Walnut Gulch Experimental Watershed (WGEW). Substantial progress has also been made within the MU in planning and conducting research for the rangeland portion of the congressionally mandated NRCS Conservation Effects Assessment Project (CEAP) in cooperation with multiple ARS labs, NRCS locations and NASA Ames. The MU was heavily involved in organizing the annual international conference of the Soil and Water Conservation Society held in Tucson in late July. The effects of a long-term drought on plant mortality and subsequent replacement by an invasive species within the WGEW on the watershed runoff and erosion response has been observed. This provides an unparalleled opportunity to assess the hydro- ecological impacts associated with this extreme climatic event as the MU can contrast this to the long, and well documented, watershed records, observations, and research knowledge base accumulated over the prior 50 years. Fortuitously, the MU successfully recruited a rangeland plant physiologist/ecologist, Dr. Erik Hamerlynck, who started this FY. Dr. Hamerlynck and several other scientists of the MU are actively conducting research on this front and a number of important results are anticipated in the coming year(s). The MU joined an informal user group of public land managers across Arizona that was established to evaluate both a time series of remotely sensed estimates of canopy cover across the state and tools for web access to the cover estimates for improved management. In cooperation with the EPA and the University of Arizona the MU released version 2.0 of the Automated Geospatial Watershed Assessment (AGWA) tool (www.tucson.ars.ag.gov/agwa) and the web-based WEPPCAT tool (http://typhoon.tucson.ars.ag.gov/weppcat/index.php). Both are tools that make ARS technology more accessible and usable for watershed management. The MU has continued is close association and membership with the Congressionally recognized Upper San Pedro Partnership (http://www.usppartnership.com/) to provide research and technical assistance for the Partnership to meet it objective for sufficient water, now and in the future, for residents of the Sierra-Vista subwatershed of the San Pedro and the San Pedro National Riparian Conservation area. Research results from the MU supplied new and improved estimates of riparian water use for basin water balance calculations. In addition, new methods employing remote sensing techniques were developed which will markedly simplify future estimates for riparian water use. Remote sensing methods were also developed to provide large area estimates of soil moisture, CO2 fluxes and leaf area indices that will greatly enhance our ability to characterize watershed states and fluxes. NP 211, Problem 5. Significant Activities that Support Special Target Populations 5. Significant Activities that Support Special Target Programs SWRC scientists are actively participating in a mentoring program through collaboration with the University of Arizona/NASA Space Grant Program. The program matches outstanding undergraduate students from underrepresented groups with mentors from the SWRC to work together on projects developed by mentors. The ultimate goal of the program is to "grow our own" scientists from underrepresented groups. Over the last five years, twelve students (Hispanic, African-American, women) have come through the program. This year two women completed the program under this project. SWRC scientists are heavily involved in the NSF Sustainability of semiArid Hydrology and Riparian Areas (SAHRA) Science and Technology Center. This program has a very active program in outreach and education of Native American communities to increase hydrologic awareness career opportunities in science. Technology Transfer Number of Web Sites managed: 3 Number of Other Technology Transfer: 2
Impacts
(N/A)
Publications
- Goodrich, D.C., Unkrich, C.L., Keefer, T.O., Nichols, M.H., Stone, J.J., Levick, L., Scott, R.L. 2008. Event to multidecadal persistence in rainfall and runoff in southeast Arizona. Water Resour. Res., 44, W05S14, doi:10.1029/2007WR006222.
- Scott, R.L., Cable, W.L., Hultine, K.R. 2008. The ecohydrologic significance of hydraulic redistribution in a semiarid savanna. Water Resources Research. Vol. 44, W02440, doi:10.1029/2007WR006149.
- Keefer, T.O., Unkrich, C.L., Smith, J.R., Goodrich, D.C., Moran, M.S., Simanton, J.R. 2008. An event-based comparison of two types of automated- recording, weighing bucket rain gauges. Water Resources Research, Vol. 44, W05S12, doi:10.1029/2006WR005841.
- Stone, J.J., Nichols, M.H., Goodrich, D.C., Buono, J. 2008. Long-term runoff database, Walnut Gulch Experimental Watershed, Arizona, United States. Water Resources Research, Vol. 44, W05S05, doi:10. 1029/2006WR005733.
- Garcia, M., Peters-Lidard, C.D., Goodrich, D.C. 2008. Spatial interpolation of precipitation in a dense gauge network for monsoon storm events in the southwestern United States. Water Resources Research, Vol. 44, W05S13, doi:10.1029/2006WR005788.
- Goodrich, D.C., Keefer, T.O., Unkrich, C.L., Nichols, M.H., Osborn, H.B., Stone, J.J., Smith, J.R. 2008. Long-term precipitation database, Walnut Gulch Experimental Watershed, Arizona, United States. Water Resources Research, Vol. 44, W05S04, doi:10.1029/2006WR005782.
- Yatheendradas, S., Wagener, T., Gupta, H., Unkrich, C.L., Goodrich, D.C., Schaffner, M., Stewart, A. 2008. Understanding uncertainty in distributed flash flood forecasting for semiarid regions. Water Resources Research, Vol. 44, W05S19, doi:10.1029/2007WR005940.
- Emmerich, W.E., Verdugo, C.L. 2008. Long-term carbon dioxide and water flux database, Walnut Gulch Experimental Watershed, Arizona, USA. Water Resources Research. 44, W05S09, doi: 10.1029/2006/WR05693.
- Emmerich, W.E., Verdugo, C.L. 2008. Precipitation thresholds for CO2 uptake in grass and shrub plant communities on Walnut Gulch Experimental Watershed. Water Resources Research. 44, W05S16, doi:10.1029/2006WR005690.
- Scott, R.L., Cable, W.L., Huxman, T.E., Nagler, P.L., Hernandez, M., Goodrich, D.C. 2008. Multiyear riparian evapotranspiration and groundwater use for a semiarid watershed. J. of Arid Environments. 72:1232-1246. doi:10.1016/j.jaridenv.2008.01.001
- Keefer, T.O., Moran, M.S., Paige, G.B. 2008. Long-term meteorological and soil hydrology database, Walnut Gulch Experimental Watershed, Arizona, United States. Water Resources Research, Vol. 44, W05S07, doi:10. 1029/2006WR005702.
- Paige, G.P., Keefer, T.O. 2008. Comparison of field performance of multiple soil moisture sensors in a semi-arid rangeland. Journal of the American Water Resources Association (JAWRA) 44(1):121-135. DOI: 10.1111/j. 1752-1688.2007.00142.x
- Thoma, D., Moran, M.S., Bryant, R., Rahman, M., Holifield Collins, C.D., Keefer, T.O., Noriega, R., Osman, I., Skirvin, S., Tischler, M., Bosch, D. D., Starks, P.J., Peters-Lidard, C. 2008. Appropriate scale of soil moisture retrieval from high-resolution radar imagery for bare and minimally vegetated soils. Remote Sensing of Environment. 112:403-414.
- Holifield Collins, C.D., Emmerich, W.E., Moran, M.S., Hernandez, M., Scott, R.L., Bryant, R., King, D., Verdugo, C.L. 2008. A remote sensing approach for estimating distributed daily net carbon dioxide flux in semiarid grasslands. Water Resources Research, Vol. 44, W05S17, doi:10. 1029/2006WR005699.
- Rodriguez, L., Cello, P., Vionnet, C., Goodrich, D.C. 2008. Fully conservative coupling of HEC-1 RAS with MODFLOW to simulate stream-aquifer interactions in a drainage basin. Journal of Hydrology. 353:129-142.
- Jackson, T.J., Moran, M.S., O'Neill, P.E. 2008. Introduction to Soil Moisture Experiments 2007 (SMEX04). Remote Sensing of Environment. 112:301- 303.
- Miller, S.N., Guertin, D.P., Goodrich, D.C. 2007. Hydrologic modeling uncertainty resulting from land cover misclassification. Journal of the American Water Resources Association 43(4):1065-1075.
- Houberg, R., Henrik, S., Emmerich, W.E., Moran, M.S. 2007. Inferences of all-sky solar irradiance using Terra and Agua MODIS satellite data. International J. of Remote Sensing. 28(20): 4509-4535.
- Wagener, T., Gupta, H., Yatheendradas, S., Goodrich, D.C., Unkrich, C.L., Schaffner, M. 2007. Understanding sources of uncertainty in flash-flood forecasting for semi-arid regions. International Association of Hydrological Science. 313:204-212.
- Emmerich, W.E. 2007. Ecosystem water use efficiency in a semiarid shrubland and grassland community. Rangeland Ecology and Management. 60:464-470.
- Bloschl, G., Ardoin, S., Bonell, M., Dorninger, M., Goodrich, D.C., Gutknecht, D., Matamoros, D., Merz, B., Shand, P., Szolgay, J. 2007. At what scales do climate variability and land cover change impact on flooding and low flows? Hydrological Processes. 21:1241-1247.
- Mcvay, K.A., Budde, J.A., Fabrizzi, K., Mikha, M.M., Rice, C.W., Schlegel, A.J., Peterson, D.E., Sweeney, D.W., Thompson, C. 2006. Management effects on soil physical properties in long-term tillage studies in Kansas. Soil Science Society of America Journal. 70:434-438. Doi:10.2136/sssaj2005.0249.
- Yepez, E.A., Scott, R.L., Cable, W.L., Williams, D.G. 2007. Intraseasonal variation in water and carbon dioxide flux components in a semiarid riparian woodland. Ecosystems. 10:1100-1115.
|
Progress 10/01/06 to 09/30/07
Outputs
Progress Report Objectives (from AD-416) Quantify primary semiarid water and energy balance components with emphasis on rainfall, storm water recharge, and evapotranspiration. Develop improved watershed model components and decision support systems that more fully utilize and assimilate economic and remotely sensed data for parameterization, calibration, and model state adjustment. Quantify ecosystem influence and feedbacks on water fluxes and states over a selected range of arid and semiarid primary vegetation types. Approach (from AD-416) Methods of investigation include field and laboratory experimentation, as well as the development and use of state-of-the-science watershed models and the use of remote sensing for watershed characterization. Satellite derived rainfall will be evaluated using raingages for large area rainfall estimation, the enhancement of recharge due to urbanization will be examined in adjacent, well instrumented, natural and residentially developed catchments. High-resolution remotely sensing and rainfall simulator experiments will be used to evaluate the capability to remote estimate infiltration rates on compacted and constructed surface common to development at the urban-rural interface. Remote spectral surface responses will be combined with energy balance models and radiative transfer theory to estimate surface water, carbon and energy fluxes based on observations from a network of five eddy-covariance and two Bowen ratio towers. A number of modeling components for the Automated Geospatial Watershed Assessment (AGWA) will be developed or enhanced to enable a more realistic representation of watershed processes and best management practices. AGWA will be migrated to both the internet and ARCGIS platforms to enhance usability and access. In addition we will quantify the physical mechanisms and component fluxes that are responsible for the observed ecosystem-scale water and CO2 fluxes. Scientists will carry out this research at sites located across both a riparian and an upland woody plant encroachment gradient. Formerly 5342- 13610-007-00D (12/06). Significant Activities that Support Special Target Populations During FY07 a transition was made from the prior research plan to the current plan starting Jan. 31, 2007. The prior project was entitled �Hydrologic Processes, Scale, Water Resources, and Global Change for Semiarid Watershed Management� (Project Number: 5342-13610-007-00D; Project Period: 05/01/2002 to 01/30/2007). In addition to beginning research on the new project and addressing the milestones noted above, a major coordinated effort by the entire MU was carried out during FY07. This effort was the development of a set of papers describing and analyzing over 50 years of data (precipitation, runoff, sediment, weather, soil moisture, vegetation, carbon and water flux, remote sensing, and geographic data) collected at the U.S.D.A. Walnut Gulch Experimental Watershed (WGEW). These papers have been submitted for an upcoming special issue of Water Resources Research and are in various stages of review. The MU has also been heavily involved in gearing up for the Conservation Effects Assessment Project (CEAP) move to the western United States. The Tucson MU and the ARS Northwest Watershed Research Center in Boise are leading development of the Rangeland Hydrology and Erosion Model (RHEM) both for CEAP and NRCS use in the west. Several planning meetings have been held and model development for the event based model is well underway. The following subordinate ARS projects are being conducted under the auspices of this project to assist in achieving the milestone and research objectives of this project and its predecessor. 5342-13610-007-14S - Remote Sensing and GIS for Improved Characterization of Landscapes for Hydrologic Modeling and Estimation of Soil Moisture 5342-13610-010-01R - Spatially Integrated Environmental Modeling 5342-13610-010-02R � Prediction of Seasonal to Inter-Annual Hydro- Climatology including the Effects of Vegetation Dynamics and Topography over Large River Basins 5342-13610-010-03R - Forecasting Water Quality and Quantity Hazards Using Spatially Distributed Watershed Models and Biophysical Data 5342-13610-010-05S - San Pedro Riparian National Conservation Area (SPRNCA) Riparian Water Needs Study 5342-13610-010-06S � Geospatial Watershed Modeling for Improved Water Management Accomplishments Understanding the consequences of woody plant encroachment in Western rangelands. Encroachment by woody plants into former grasslands has been a widely reported phenomenon across many semiarid landscapes around the world, yet we do not understand how this pervasive on-going change in vegetation will affect water and nutrient cycling on rangelands. Scientists at the SWRC, Tucson, AZ investigated how the water and carbon dioxide are cycled in a Chihuahuan Desert shrubland in southeastern Arizona. Results suggest that the ecosystem lost the most carbon at the start of the summer rainy season when the shrubs were still dormant, but once the shrubs became active they were able to efficiently acquire both water and carbon dioxide throughout the growing season. The dataset collected in this study is one of the longest of its kind and will be an important benchmark for future studies on woody plant encroachment. NP 201/211, Problem Area 5, Problem Statement: More accurate quantitative components of basin water budgets that consider ecosystem feedbacks affecting watershed states and fluxes and enhanced instrumentation (in- situ soil moisture, eddy-covariance, etc.) applications coordinated with ecosystem and biogeochemical observations. The effect of rainfall events on riparian ecosystems in semiarid environments. The influence of different hydrological processes on the structure and functioning of riparian vegetation in semiarid basins is not well understood and this information is critical to the management of these important and ecologically diverse ecosystems, which are threatened by human groundwater use in the western U.S. The results of many studies along the San Pedro River conducted in southeastern Arizona were synthesized to show that rooting depth and access to groundwater are key factors that control the vegetations water use and carbon dioxide exchange. Depth to groundwater, which varies substantially across the riparian landscape, is a key factor controlling the sensitivity of cottonwood transpiration, leaf photosynthetic metabolism, and plant water sources to pulsed inputs of growing season moisture. Because mesquite accesses groundwater in these habitats, ET and gross ecosystem production are decoupled from precipitation, but ecosystem respiration remains highly coupled to rainfall due to the dominant contribution of litter and bulk soil organic matter decomposition. Responses of net ecosystem exchange of carbon dioxide to rainfall variability in riparian floodplain is therefore not simple, but depends on vegetation structure and the connection of dominant plants to the water table. The complex vegetation patterns, hydrologic setting and disturbance dynamics in the riparian landscape offer unparalleled opportunities to investigate fundamental processes linking water and carbon exchange. NP 201/211, Problem Area 5, Problem Statement: More accurate quantitative components of basin water budgets that consider ecosystem feedbacks affecting watershed states and fluxes and enhanced instrumentation (in-situ soil moisture, eddy- covariance, etc.) applications coordinated with ecosystem and biogeochemical observations. A space-based approach for mapping regional surface roughness. When runoff occurs on a watershed, the roughness of the surface of the watershed plays an important role in how rapidly water moves on the watershed, which in turn is very important determining the magnitude of flooding and erosion. Surface roughness, as it affects water flow and erosion, is typically estimated is a relatively subjective manner and is very difficult to do consistently over large areas. Often empirical methods are used or gross extrapolations are made from laboratory studies. In this study, ARS and Univ. of Arizona scientists developed a new approach to derive roughness data from satellite-based radar images. The result is a quantitative, and consistently derived, roughness map applicable to large drainage areas. This estimates can be directly input into hydrologic models to improve estimates of erosion and runoff. NP 201/211, Problem Area 5, Problem Statement: Improved watershed simulation, plant growth, and weather generation model components and data assimilation tools for water budget, water quality assessment, and flood and drought risk and impact assessment. Estimating soil texture and hydraulic properties from remote sensing data and modeling. Soil texture and hydraulic properties are critical components of energy and water balance studies, but are not easily determined over heterogeneous regions. This study conducted by NASA, ARS scientists in Tucson, AZ and the U.S. Army used estimates of soil moisture derived from satellite imagery to infer soil texture and hydraulic properties from a land surface model. This operational approach is useful for mapping soil information using available technology for a better understanding of water availability in semiarid watersheds. Research is useful for farmers and managers of semiarid watersheds. NP 201/211, Problem Area 5, Problem Statement: Improved watershed simulation, plant growth, and weather generation model components and data assimilation tools for water budget, water quality assessment, and flood and drought risk and impact assessment. (Also addresses Obj. 1 in Coordinated Plan of Work (CPW) entitled �Remote Sensing for Parameters and States of Watershed Models for Improved Watershed Management." Significant Activities that Support Special Target Populations Significant activities that support special target populations. SWRC scientists are actively participating in a mentoring program through collaboration with the University of Arizona/NASA Space Grant Program. The program matches outstanding undergraduate students from underrepresented groups with mentors from the SWRC to work together on projects developed by mentors. The ultimate goal of the program is to "grow our own" scientists from underrepresented groups. Over the last four years, twelve students (Hispanic, African-American, women) have come through the program. This year two women completed the program under this project. SWRC scientists are heavily involved in the NSF Sustainability of semiArid Hydrology and Riparian Areas (SAHRA) Science and Technology Center. This program has a very active program in outreach and education of Native American communities to increase hydrologic awareness career opportunities in science. Technology Transfer Number of Web Sites managed: 4 Number of Non-Peer Reviewed Presentations and Proceedings: 7 Number of Newspaper Articles,Presentations for NonScience Audiences: 13
Impacts
(N/A)
Publications
- Bryant, R., Moran, M.S., Thoma, D., Holifield Collins, C.D., Skirvin, S.M., Rahman, M., Slocum, K., Starks, P.J., Bosch, D.D., Gonzalez-Dugo, M.P. 2007. Measuring surface roughness height to parameterize radar backscatter models for retrieval of surface soil moisture. IEEE Geosci. and Rem. Sens. Letters 4(1): 137-141.
- Nagler, P.L., Glenn, E., Kim, H., Emmerich, W.E., Scott, R.L., Huxman, T., Huete, A. 2007. Relationship between evapotranspiration and precipitation pulses in a semiarid rangeland estimated by moisture flux towers and modis vegetation indices. Journal of Arid Environments. 70:443-462.
- Nichols, M.H. 2007. The walnut gulch experimental watershed - 50 years of watershed monitoring and research. In: Monitoring and Evaluation of Soil Conservation and Watershed Development Projects. de Graaff, J, Cameron, J., Sombatpanit, S., Pieri, C., Woodhill, J.(eds.). World Association of Soil and Water Conservation, Bangkok. 496 p.
- Potts, D.L., Huxman, T.E., Scott, R.L., Williams, D.G., Goodrich, D.C. 2006. The sensitivity of ecosystem carbon exchange to seasonal precipitation and woody plant encroachment. Oecologia 150(3): 453-463.
- Santanello, Jr., J.A., Peters-Lidard, C.D., Garcia, M.E., Mocko, D.M., Tischler, M.A., Moran, M.S., Thoma, D.P. 2007. Using Remotely-Sensed Estimates of Soil Moisture to Infer Soil Texture and Hydraulic Properties across a Semi-arid Watershed. Remote Sensing of Environment. 110:79-97. doi:10.1016/j.rse.2007.02.007.
- Tischler, M., Garcia, M., Peters-Lidard, C., Moran, M.S., Miller, S., Thoma, D., Kumar, S., Geiger, J. 2007. A GIS framework for surface-layer soil moisture estimation combining satellite radar measurements and land surface modeling with soil physical property estimation. J. of Environmental Modeling and Software 22:891-898.
|
|