Progress 10/01/99 to 09/30/05
Outputs
This research has produced the longest continuous data-set on spring-fed wetland responses to controlled grazing. Two experiments on grazing intensity effects on spring-fed wetlands have been applied. Grazing treatments on the long-term study (1991-2006) include grazing removal from the spring and resultant creek, light grazing as defined by leaving 1000-1200 lbs/acre RDM in the annual grass uplands, and moderate grazing defined by leaving 600-700 lbs/acre RDM in the uplands. Nine springs enclosed in ~2.5 ha pastures continue to be treated as part of the long-term study. A shorter term study took place on marshy springs between 1999-2002, where 2 grazing treatments were applied to test their effects on soil-water nitrate levels, and greenhouse gas emissions. The treatments on these 6 springs were removal of cattle and moderate grazing. Plant species composition on the original 9 springs has fluctuated over time, but community composition has remained the same over the
study, indicating a high degree of resilience at the community scale to changes in grazing. Herbaceous diversity did not change relative to pre-treatment levels in any of the original 9 springs. There were no changes in the relative amounts of native and nonnative species over time under any grazing treatment. Lightly grazed wetlands maintained greater species eveness and diversity relative to pretreatment values than either ungrazed or moderately grazed plots. At creeks, moderately grazed plots maintained greater relative total species, eveness and diversity than lightly grazed and ungrazed plots, which were not significantly different from each other. On marshy springs, results indicate that light grazing on spring-fed wetlands and moderate grazing on down-slope creeks maintain current plant diversity. Channel morphology did change under the 3 grazing treatments after 5 years. Ungrazed springs and creeks exhibited more year-to-year variability than grazed springs and creeks,
although the differences were not significant. On the short-term study, we found that methane fluxes (the amount released to the air) was reduced with the removal of grazing from the springs. Air temperature and soil water content were the most important variables affecting the overall flux of methane from the spring systems, but removal of grazing reduced the amount of methane emissions by more than 80%. In the marshy wetlands, nitrate was intercepted and retained as it moved along its hydrologic path from upland soils to emergent spring waters. The removal of cattle grazing from these wetlands impaired the ability of the springs to retain nitrate. Grazing removal allowed dead plant material to accumulate, thereby inhibiting plant production and hence, plant nitrogen demand, resulting in stream water nitrate concentrations that far exceeded the US EPA surface-water maximum standard of 714 micromoles.
Impacts
Results indicate that there are specific management trade-offs based on ecosystem responses to variables of interest. Range and livestock managers can use this information to weigh potential outcomes and meet specific conservation objectives. Removal of cattle grazing from these systems results in increased nitrate levels in the spring waters (bad from a water quality point of view) and decreased methane flux (good from a greenhouse gas point of view). Plant cover and plant diversity decreases under moderate grazing treatments, while light grazing and removal of grazing results in higher plant cover. Plant biodiversity is maximized under light grazing treatments.
Publications
- Allen-Diaz, B.H. and R.D. Jackson. 2000. Grazing effects on spring ecosystem vegetation of Californias hardwood rangelands. J. Range Management 53:215-220.
- Jackson, R. and B. Allen-Diaz. 2003. Livestock grazing on spring-fed riparian areas of Californias foothill oak woodlands. In: Proc.California Riparian Systems: Processes and Floodplains Management, Ecology, and Restoration. P.M. Faber (Ed.), Riparian Habitat Joint Venture , Sacramento, CA. March 12-15, 2001. 557 p.
- Jackson, R.D. and B. Allen-Diaz. 2002. Nitrogen dynamics of spring-fed wetland ecosystems of the Sierra Nevada foothills oak woodland. In: Proc. 5th Oak Symposium: Oaks in Californias Changing Landscape. San Diego, CA.Gen. Tech. Rep. PSW-GTR-184:119-130.
- Jackson, Randall D. and B. Allen-Diaz. 2001. Spring-fed plant communities of Californias east bay hills oak woodlands. Abstracts: Society for Range Management meeting. Poster Session 1-196. Kona, Hawaii. February 17-23,2001.
- Allen-Diaz, B., R. Jackson, J. Bartolome, K. Tate, and G. Oates. 2004. Grazing management of spring-fed wetlands in Californian oak woodlands: summary of results of a long term study. California Agriculture 58: 144-148.
- Wenk, R.C., J.B. Battles, R.D. Jackson, J.W. Bartolome, and B.Allen-Diaz. 2006. An accurate and efficient method for sorting biomass extracted from soil cores using point-intercept sampling. Soil. Sci. Soc. Am. J. 70: 851-855.
- Allen-Diaz, Barbara H. 2004. Sierra Nevada Grasslands: Interactions between livestock grazing and ecosystem structure and function. In: Proc. Sierra Nevada Science Symposium. Lake Tahoe, CA. USDA Forest Service Gen. Techn. Rep. PSW-GTR 193. pp. 111-114.
- Allen-Diaz, B. and W.E. Frost. 2004. Water quality key to states prosperity. Editorial. California Agriculture 58: 130.
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Progress 01/01/04 to 12/31/04
Outputs
This research has produced the longest continuous data-set on spring-fed wetland species composition and cover responses to controlled grazing. Two experiments on grazing intensity effects on spring-fed wetlands are ongoing. Response variables include plant species composition and cover. Water quality sampling was initiated again to compare to previous (1992-1997) results under the same continuous grazing treatments.
Impacts
Results indicate that there are specific management trade-offs based on ecosystem responses to variables of interest. Range and livestock managers can use this information to weigh potential outcomes and meet specific conservation objectives. Removal of cattle grazing from these systems results in increased nitrate levels in the spring waters (bad from a water quality point of view) and decreased methane flux (good from a greenhouse gas point of view). Plant cover and plant diversity decreases under moderate grazing treatments, while light grazing and removal of grazing results in higher plant cover. Plant biodiversity is maximized under light grazing treatments.
Publications
- Allen-Diaz, B. and Jackson, R.D. 2004. Long term changes in spring-fed wetlands in the oak woodlands of California. Ecological Society of America Annual Meeting. Portland, OR. August 1-6, 2004. Published Abstract #ALL-1077-816191.
- Oates, L.G., Jackson, R.D. and Allen-Diaz, B. 2004. Grazing effects on methane emissions and ecosystem function of a spring-fed wetland in a California oak savanna. Ecological Society of America Annual Meeting. Portland, OR. August 1-6, 2004. Published Abstract #OAT-1078-179486.
- Lennox, M., Lewis, D., Jackson, R., Harper, J., Katz, R., Larson, S., Allen-Diaz, B. and Tate, K. 2004. In press. Riparian revegetation evaluation in North Coastal California. In: AWRAs Summer Specialty Conference: Riparian Ecosystems and Buffers: Multiscale Structure, Function, and Management. Olympic Valley, CA. June 28-30, 2004.
- Jackson, R.D., Allen-Diaz, B., Oates, L.G. and Tate, K.W. 2004. In press. Spring-water nitrate increased with removal of livestock grazing in a California oak savanna. Ecosystems.
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Progress 01/01/03 to 12/31/03
Outputs
GSY=5. 10-year and 3-year experiments have been summarized. Spring ecosystem response variables included plant composition, diversity, cover, water quality, channel morphology, aquatic insects and greenhouse gases. Our data indicate that wetland vegetation acts as a nutrient filter for waters emerging at the soil surface. High herbaceous plant production is one of the key factors for maintaining ecosystem services, by promoting carbon sequestration and nutrient conservation from the terrestrial landscape. Removal of livestock grazing resulted in increased levels of nitrate in wetland waters and thus higher levels of nitrate pollution. Conversely, removal of livestock grazing, especially during the early summer when temperature and soil water is at an optimal level, reduced the amount of methane emissions. Preliminary data suggests that grazing removal from springs may increase the production of nitrous oxide, another potent greenhouse gas.
Impacts
Spring ecosystems are important in overall landscape structure and function in a way that is disproportionate to their size. Although the wetland functions are complex, these studies indicate that some level of grazing is probably desirable from a species diversity point of view as well as a management tool for influencing nitrate and methane emissions. The results from this study inform grazing managers as to the appropriate timing and intensity of grazing on these systems in order to maximize the health of these wetlands and their benefit to the larger landscape.
Publications
- Bartolome, J.W., Fehmi, J.S., Jackson, R.D. and Allen-Diaz, B. 2003. In press. Response of a native perennial grass stand to disturbance in California's Coast Range grassland. Restoration Ecology.
- Allen-Diaz, B., Jackson, R., Bartolome, J., Tate, K. and Oates, G. 2003. In press. Grazing management of spring-fed wetlands in Californian oak woodlands: summary of results of a long term study. California Agriculture.
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Progress 01/01/02 to 12/31/02
Outputs
GSY = 3. This research to study the effects of various grazing treatments on spring-fed wetlands of the Sierra Nevada foothills has found that in some cases plant composition can be manipulated with grazing where lightly grazed sites maintained a greater diversity and evenness of species. Total plant cover did not differ among the sites after 7 years, but after 10, moderately grazed sites showed significant decreases in cover (indicating the importance of long-term monitoring). The effect on water quality varied, but in certain wetlands the removal of grazing resulted in increased nitrate concentrations in waters flowing out of the spring. On the other hand, removal of grazing also resulted in lesser emissions of methane, a potent greenhouse gas. Channel morphology did not vary with treatment, but the species richness of aquatic insects tended to decrease with increasing grazing.
Impacts
The effect of grazing on spring-fed wetlands is complex, but in a broad sense, these studies indicate that some level of grazing is probably desirable, particularly from the standpoint of species diversity. In addition, removal of grazing can have a negative impact on water quality by increasing the concentration of nitrates that are released into the springs. However the results also suggest that high levels of grazing can damage these systems and that grazing in general may increase greenhouse gas emissions. Therefore, appropriate management, including adjustments to the timing and intensity of the grazing, should be used to maximize the health of these wetlands and their benefit to the larger landscape. In general, these studies have, and will continue, to inform how we manage these important systems in the years ahead.
Publications
- Jackson, R.D., and Allen-Diaz, B. 2002. Nitrogen dynamics of spring-fed wetland ecosystems of the Sierra Nevada foothills oak woodland. In: Proc. 5th Oak Symposium: Oaks in California's Changing Landscape. San Diego, CA.Gen. Tech. Rep. PSW-GTR-184:119-130.
- Bartolome, J.W., M.P. McClaran, B. Allen-Diaz, J.Dunne, L.Ford, R. Standiford, N. McDougald, and L. Forero. 2002. Effects of fire and browsing on regeneration of blue oak. . In: Proc. 5th Oak Symposium: Oaks in California's Changing Landscape. San Diego, CA.Gen. Tech. Rep. PSW-GTR-184:281-286.
- Allen-Diaz, B. and R. Jackson. 2002. Grazing California's oak woodlands: ecological effects and the potential for conservation management. In: Planning for Biodiversity: Bringing research and management together. Feb 29-March 2, 2000. California Polytechnic University, Pomona, CA. USDA Forest Service/USGS Western Ecological Research Center.
- Jackson, R., J.W. Bartolome, and B. Allen-Diaz. 2002. State and Transition Models; Response to an ESA symposium. Bull. Ecol. Soc. Amer. 83(3): 194-196. Merenlender, A.M., K.L. Heise, J.W. Bartolome, and B.H. Allen-Diaz. 2001. Monitoring shows vegetation change at multiple scales. California Agriculture 55(6): 42-46.
- Allen-Diaz, B. and R.D. Jackson. 2003. Grazing California's oak woodlands: ecological effects and the potential for conservation management. IN: Planning for Biodiversity: Bringing research and management together. A Symposium for the California Southcoast Ecoregion. USDA Forest Service and USDI Geological Survey. Kellogg West Conference Center, February 29-March 2, 2000.
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Progress 01/01/01 to 12/31/01
Outputs
GSY = 3. Surface waters within wetlands showed a general pattern of relatively constant nitrate concentrations through the summer and early autumn (0.20 ppm nitrate-N) with marked increase during winter months and a peak for the period representing late January through early February (0.69 ppm nitrate-N). Ammonium and nitrate pool sizes covaried inversely with nitrate dominating in autumn/winter during plant dormancy (3 ug g dry soil-1) and ammonium dominance in spring/summer (6 ug gds-1) when wetland plants were beginning yearly production cycles. Past work has shown that nitrate, which is highly mobile in the vadose zone, accumulates in the absence of plant growth during dry summer months in the annual grassland matrix that surrounds these wetland systems. Much of this nitrate may be flushed down-slope to spring systems with the onset of autumn rains. The large nitrate concentrations observed at springs for autumn coupled with relatively low net nitrate production
within springs for the same period show that springs may be sinks for upland-derived nitrate. Microbial biomass exhibited little seasonal variability and no response to grazing removal illustrating the high availability of resources in these systems.
Impacts
Impact: Spring-fed wetlands provide important ecosystem services at the terrestrial-aquatic interface by sequestering and/or transforming exogenous N. Grazing at the springs may encourage terrestrial conservation (acting as a transformer and/or sink) of N that would otherwise be lost to the atmosphere (source) with grazing removal. Wetland biodiversity generally declines with removal of grazing from these systems.
Publications
- Allen-Diaz, B. and Jackson, Randall D. 2000. Grazing effects on spring ecosystem vegetation of California's hardwood rangelands. J. Range Manage. 53(2): 215-220.
- Jackson, Randall D., Allen-Diaz, B., and Bartolome, J.W. 2001. State-transition models of rangeland vegetation dynamics. Oral session N-#197. Kona, Hawaii. February 17-23, 2001.
- Jackson, R. and Allen-Diaz, B. 2001. Livestock grazing on spring-fed riparian areas of California's foothill oak woodlands. Abstract. Riparian Habitat and Floodplains Conference. March 12-15, 2001. Sacramento, CA.
- Fernandez-Gimenez, M. and Allen-Diaz, B. 2001. Vegetation change along gradients from water sources in three grazed Mongolian ecosystems. Plant Ecology 157: 101-118.
- Allen-Diaz, B.H., Jackson, R.D., and Phillips, C. 2001. Spring communities of the East Bay Hills oak woodland, Contra Costa and Alameda Counties, California. Madrono 48(2): 98-111.
- Jackson, R. and Allen-Diaz, B. (in press). Livestock grazing on spring-fed riparian areas of California's foothill oak woodlands. Proc. Riparian Habitat and Floodplains Conference. March 12-15, 2001. Sacramento, CA.
- Jackson, R. and Allen-Diaz, B. (in press). Nitrogen dynamics of spring-fed wetland ecosystems of the Sierra Nevada foothills oak woodland. Proc. 5th Symposium on Oak Woodlands: Oaks in California's Changing Landscape. October 22-25, 2001 in San Diego, CA.
- Allen-Diaz, B. and Shlisky, Ayn. 2001. Application of state-transition models in Sierra Nevada meadows. Abstracts: Society for Range Management meeting. Oral session N-#6. Kona, Hawaii. February 17-23, 2001.
- Jackson, Randall D. and Allen-Diaz, B. 2001. Spring-fed plant communities of California's east bay hills oak woodlands. Abstracts: Society for Range Management meeting. Poster Session 1-#196. Kona, Hawaii. February 17-23, 2001.
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Progress 01/01/00 to 12/31/00
Outputs
GSY = 3. The objectives of the study are to 1. test vegetation cover effects on spring ecosystem water quality, 2. determine cattle grazing effects on vegetation structure, 3. assess cattle grazing effects on spring-ecosystem function by estimating energy flow and nutrient cycling among plant, litter, and soil pools, and 4. assess spring-ecosystem nitrate interception and transformation potential. Plant, litter, and soil samples were collected and analyzed for C and N. Tensiometers were installed and sampled to detect water flow pattern and to collect sub-surface water quality samples. Vegetation structure results have shown these systems to be resilient to grazing. Water quality analyses from the springs also show no treatment effects.
Impacts
Results will guide management decisions concerning timing and intensity of livestock grazing on oak woodland dominated rangelands. Documentation of nitrate movement at the terrestrial-aquatic interface will help determine the relative importance of spring ecosystems to the oak woodland matrix and downstream aquatic ecosystems.
Publications
- Tate, K.W., Dahlgren, R.A., Singer, M.J., Allen-Diaz, B., and Atwill, E.R. 1999. Monitoring water quality on California rangeland watershed; Timing is everything. California Agriculture 53(6): 44-48.
- Allen-Diaz, B., and Tate, K.W. 2000. Science, dogma or fact: Grazing in the Sierra Nevada. Abstracts 53rd Annual Meeting, Soc. Range Manage. Boise, ID, February 13-18, 2000.
- Allen-Diaz, B. 2000. Effects of grazing in oak woodland habitats. Abstracts Planning for Biodiversity: Bringing research and management together. A Symposium for the California Southcoast Ecoregion. USDA Forest Service and USDI Geological Survey. Kellogg West Conference Center, February 29-March 2, 2000. Page 27.
- Vayssieres, Marc P., Plant, R.E., and Allen-Diaz, B. 2000. Classification trees: An alternative non-parametric approach for predicting species distributions. J. Vegetation Science 11: 679-694.
- Salve, Rohit, and Allen-Diaz, B. 2000. Variations in soil moisture content in a rangeland catchment. J. Range Manage. 54(1): 44-51.
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