Source: UNIVERSITY OF NEBRASKA submitted to NRP
PONDEROSA PINE ON THE EDGE: FIRE, ECOLOGICAL RESILIENCE AND THE FUTURE OF NEBRASKAS PINE LANDSCAPES
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
COMPLETE
Funding Source
MCINTIRE-STENNIS
Reporting Frequency
Annual
Accession No.
1008861
Grant No.
(N/A)
Cumulative Award Amt.
(N/A)
Proposal No.
(N/A)
Multistate No.
(N/A)
Project Start Date
Jan 11, 2016
Project End Date
Sep 30, 2020
Grant Year
(N/A)
Program Code
[(N/A)]- (N/A)
Recipient Organization
UNIVERSITY OF NEBRASKA
(N/A)
LINCOLN,NE 68583
Performing Department
Agronomy & Horticulture
Non Technical Summary
Ponderosa pine reaches the eastern most edge of its distribution in Nebraska. Nebraska's three native ponderosa pine regions (Pine Ridge, Wildcat Hills and Middle Niobrara Valley) are important for timber, habitat, recreation, and historical significance. Prior to settlement, Nebraska's ponderosa pine occurred in savannas and open woodlands, with low tree densities restricted to rough terrain on the edge of grasslands. However, Nebraska's pine woodlands have changed dramatically since the mid-1800's because of logging, grazing, fire prevention, and invasive plants. The resilience of our current pine woodlands is low when faced with 21st century threats including catastrophic wildfire, drought, pine beetles, and invasive species. Given current trends, Nebraska may lose its pine woodlands in the 21st century. In this project, we will partner with the Nebraska Forest Serve, the Nebraska Game and Parks Commission, the US Forest Service and the Nature Conservancy to assess the status of Nebraska's three pine regions. This assessment includes the timber resource, but also fuels, invasive species, habitat diversity, and their landscape arrangement. We will characterize the resilience of these pine woodlands at both the stand and landscape scale to the threat of severe wildfire, and study how fire interacts with the threats of drought, invasive species, and pine beetles. If we can quantify factors determining the ecological resilience of Nebraska's pine woodlands in the 21st century, the limited resources of our partners can be prioritized more effectively in managing and conserving our unique ponderosa pine regions.
Animal Health Component
50%
Research Effort Categories
Basic
50%
Applied
50%
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
1230199107050%
1220199107050%
Knowledge Area
122 - Management and Control of Forest and Range Fires; 123 - Management and Sustainability of Forest Resources;

Subject Of Investigation
0199 - Soil and land, general;

Field Of Science
1070 - Ecology;
Goals / Objectives
Goals: (1) Determine the current status of ponderosa pine in Nebraska's three core ponderosa landscapes (Pine Ridge, Middle Niobrara and Wildcat Hills); (2) develop fire models specific to Nebraska's ponderosa landscapes (3) model relative differences in the resilience of Nebraska's ponderosa pine ecosystems to wildfire and interacting factors; (4) integrate fuels management, fire models, and climate to create scenarios for the future of ponderosa pine in Nebraska. Although our long-term goals appear ambitious, much of the spatial data we need already exists as GIS layers from state and federal agencies and both NFS and NGPC have strong GIS / mapping capabilities.Objectives: (1.1) Establish permanent plots (400-800 per region) to quantify timber resources, invasive species, and habitat diversity. (1.2) In cooperation with NFS and NGPC, use plot-based data to validate existing high spatial resolution maps (e.g. GIS layers of forest structure and plant communities). (2.1) Collect data on surface fuel loading, ladder fuels and vertical fuel structure. (2.2) Customize fire science models, which are parameterized for western U.S. forests, to more accurately characterize fire dynamics in Nebraska's ponderosa pine landscapes. (3.1) Use plot data and remote sensing coverage from historical wildfires and/or experimental prescribed fires to measure pine survival and regeneration across a broad gradient of fire severities. (4.1) Assess the impact of recent forest thinning and fuels reduction management on pine recruitment, invasive species, and soil health. (4.2) Conduct sensitivity analyses on our revised fire models to determine how fire behavior, tree damage and crown combustion respond to manipulation of fuels via forest management and the potential for these activities to increase stand resilience.
Project Methods
Methods - Although considerable resources have already been invested into assessing and conserving Nebraska's ponderosa pine resources, these efforts have been fragmented and often focused on a single question such as timber production, invasive plants, or fuels reduction. They have rarely addressed all three landscapes simultaneously. A central goal of this project is to build off these diverse efforts and integrate them to develop a standardized, rigorous protocol. In cooperation with our partners, 400-800 permanent plots will be established in each landscape. Large plots will be used to measure forest structure using accepted forestry protocols and smaller nested plots will be used to measure pine recruitment (seedlings and saplings), fuel loading (herbaceous, shrub and dead wood components), and plant species composition (with a focus on invasive species and species of conservation concern).Plot locations will be stratified across variability in key factors, such as vegetative cover, topography, and land use history.During the summer of 2016 we will develop protocols and conduct trial surveys.Extensive surveys in the three study regions will occur in the summers of 2017-2020. Once complete, we will use our data to validate our partners' GIS layers and remote sensing classifications of forest structure and plant communities. The survey will allow direct comparison of different burn severities, thinned, and unmanaged stands across our three ecoregions, as well as the ability to track the impacts of climate (e.g. drought) and disturbance (e.g. fire, beetle infestations) over future decades.Fire science models have been developed to characterize fuels, fire behavior, and fire severity relationships. We will use our sampling data to parameterize these models and determine the potential for differences in fireline intensity, crown scorch and crown fire initiation and spread across our three focal landscapes. Fireline intensity is the rate of energy output from the flaming fire front and is a primary driver of crown scorch in pine species. The factors causing variation in fire intensity can be described by linking Rothermel's (1983) fire spread model and Byram's (1959) simple fireline intensity model. Twidwell et al. (2013) used these models previously to characterize thresholds in Juniperus mortality, and we will extend this approach to determine factors driving fire intensity in each landscape. Identifying differences in fire intensity are important because they control two processes critical for understanding tree damage from wildfire - crown scorch and crown combustion. Crown scorch is the portion of tree foliage killed, but not consumed, by the fire and has been widely described as a function of fireline intensity in Van Wagner's (1977) two-thirds power function. The initiation of crown combustion is more complex and depends on the properties of surface fuels and their availability for flaming combustion, vertical continuity of fuels (i.e. ladder fuels) to tree crowns, and wind speed. The Crown Fire Initiation Spread model (CFIS; Alexander et al. 2006, Baker 2009) provides output on the likelihood of crown fire initiation or occurrence, the type of crown fire, and rate of fire spread given differences in fuel stratum gaps (distance from top of surface fuels to lowest height of tree crown), wind speed and surface fuel properties. Not only are these models useful for future fire scenarios, we can validate the models by applying fire severity and field measurements from past wildfires. For example, while many trees died in the Pine Ridge 2012 wildfires, fire severity was highly variable and many pines suffered canopy scorch but not combustion. In contrast, canopy combustion was nearly complete in our study area at the 2012 Niobrara wildfire, indicating removal of the fuel stratum gap by redcedar ladder fuels and a much more severe fire.We will use our field data to parameterize the above fire models using a Bounded Ranges of Variation (BRV) framework (Moritz et al. 2013). The BRV framework specifies boundaries that correspond to the upper and lower scenarios for a given ecological process (e.g. fire behavior) and identifies thresholds of potential concern (e.g. high mortality levels, high probability of crown fire initiation) by quantifying abrupt changes in response dynamics. Our fire modeling output and recruitment data provide indicators of relative differences in the resilience and vulnerability of Nebraska's ponderosa regions to wildfire. Relatively higher crown scorch potential and likelihood of combustion initiation signals a more vulnerable landscape to fire and a higher probability of greater fire severities. Measures of tree regeneration across these landscapes provide an indication of the long-term capacity of the system to recover following wildfire and return to a ponderosa state.

Progress 01/11/16 to 09/30/20

Outputs
Target Audience:During this 5 year project, we have presented our results at state, regional and internation meetings, as well as publishing 10 scientific papers. Our audience includes both scientists and stakeholders. Throughout the project, we met with stakeholders in all three ponderosa pine regions of Nebraska: the Pine Ridge, the Wildcat Hills, and the Niobrara Valley. Each regions is designated as a Biologically Unique Landscapes (BUL) by the Nebraska Game & Parks Commission, which has facilitated stateholder meetings. We have also assisted with written reports and presentations for conservation groups (TNC, PRBE). the Nebraska Forest Service, the US Forest Service, and the Nebraska Prescribed Fire Council. Throughout the project, we have placed concerns regarding management and conservation of Nebraska's ponderosa pine in the regional (Great Plains), national and global context of unprecedented global change and altered fire regimes. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?This project supported 2 masters students, 2 doctoral students, 5 undergrads, and 2 post-doctoral researchers. The team's 4 graduate students took the lead in organizing and running field campaigns, including supervising undergraduate field assistants, across Nebraska's ponderosa pine landscapes. In addition, several other graduate students incorporated data from this project into their research (see publications from Z.Adane, D.Fogarty, H.Hefner and A.Mazis). These graduate and undergraduate students (S.Nodskov, E. Keele) were lead authors on 25 publications and conference presentations during the project. How have the results been disseminated to communities of interest?As discussed under "Target Audience", Nebraska's ponderosa pine woodlands have diverse stakeholders, including private landowners, state and federal agencies, and conservation groups. The project has shared results, and more importantly, held discussions with all of these groups through Nebraska and regional conferences and meetings. The project's cumulative "Products" list 14 conference presesentations as well as popular press articles and agency reports. The team is particularly proud of its 4 MS and PhD theses/dissertations and 12 peer-reviewed scientific articles. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? 1.1 Establish permanent plots: This was completed in the project's first 3 years. Data on stand structure, regeneration, fuel loads and understory vegetation was collected in all three of Nebraska's native pine landscapes, although the details of data collection varied across the three landscapes because each region had different graduate students, as well as agency partners. We documented large differences among the pine woodlands of these three regions. For example: the Wildcat Hills landscape has <10% dense woodland stands and >55% open savanna, while the Niobrara Valley has >60% dense stands and < 15% oven savanna. The Pine Ridge, in contrast, has >65% intermediate density stands. Regarding woodland species composition, inventories in the Pine Ridge find >95% ponderosa pine, compared to 75% pine in the Wildcat Hills, and <30% pine in the Niobrara Valley, where junipers are the most abundant species. As a consequence, the role of fire has differed across these three regions in recent decades, and diverse strategies for future woodland management and conservation may be needed. Communicating this message has been key in our publications and stakeholder meetings. 1.2 Validate existing high spatial resolution maps: We compared stand-level survey data with various regional and national land classification based on remote sensing. One conclusion was that neither the National Land Cover Database (NLCD) nor LANDFIRE land cover classes are good at distinguishing between open (e.g. <70 trees per hectare) and savanna (e.g. < 450 trees per hectare) vegetation in our study sites. Several of our publications have used national MTBS data bases as well as BAER data from specific fire events to test both local and regional hypotheses regarding fire behavior and its ecological consequences in the Great Plains. Our PhD students C. Roberts and V. Donovan have proposed alternative statistical and concepual approaches to define resilience and detect critical changes using spatial data from Great Plains woodlands. 2.1 Collect forest fuels data: This was done as part of the field work for 1.1. Data collected include hebaceous and forest floor biomass or thickness, coarse woody debris and recruitment of pine and juniper seedlings and saplings. As discussed in 1.1, there were large differences across Nebraska's three pine regions. 2.2 Run fire science models: We have parameterized our three study regions using standard US federal fire behavior models (e.g. BehavePlus, FlamMap, CIFS). In particular, we are testing whether the spatial distribution of stand structure, which differs sharply across the three regions, creates critical thresholds for fire behavior. These spatial patterns interact with climate and weather patterns, which differ sharply from east to west across Nebraska. This ongoing research is led by V .Donovan, who finished her PhD with our project in 2019. 3.1 Measure pine survival and regeneration: As part of 1.1, we collected data on the size structure, age structure and density of pines in the three pine regions. This included tree ring analyses in the Wildcat Hills and the Niobrara Valley Preserve. We found a few trees between 150 and 200 years old, but stands in both landscapes were dominated by trees dating from 1890-1920. This was a relatively cool, wet period in all three regions, but also a period of dramatic post-settlement disturbance by grazing and logging. While all three regions showed pine regeneration in the last 30 years, rates varied regionally. Many of the small (<10cm) pines found in open habitats in the Wildcat Hills were actually >50 years old. Differences in pine demography across Nebraska's three pine regions was not a major effort for our project, but these results indicate more study is merited. 4.1 Assess fuels reduction and thinning impacts: Several of our studies specifically addressed this issue (e.g. Roberts et al. 2018, Donovan et al. 2019 Forests, Peterson 2020 MS thesis). While there are generally accepted positive impacts for some fuels reduction strategies (e.g. removal of juniper ladder fuels, particularly in the densely wooded Niobrara Valley), we found ecological and economic tradeoffs associated with other fuels management strategies. Removal of snags and coarse woody debris (CWD) in the Pine Ridge increased forage resources for private ranchers, although ranchers noted a several year post-management time lag, but post-fire removal of snags and CWD decreased pine regeneration and plant and bird diversity. Thus public and private land managers in Great Plains woodlands must clarify their management objectives for fuels reduction, and as emphasized in 1.1 and 1.2 above, the response of Nebraska's three pine regions to land management will vary. 4.2 Model fire response to fuels management: As discussed in 4.1, our study has clarified the issues presented by vegetation dynamics, fire behavior and climate variability across Nebraska's three pine landscapes. This has been communicated in conference presentations, publications and stakeholder meetings. As our team and others continue to address 4.2 and model future regional scenarios, the question should be reframed: "fuels management" is inherently complex. It is confounded with habitat management, range management, timber stand improvement, and conservation of soil and water resources. In 2020, V. Donovan (in prepartion) modeled how mechanical fuels reduction, targeted grazing, and their interaction affected the probability of crown fire in Pine Ridge woodlands. Altering the vertical fuel structure of pine stands reduced crown fire probability much more than fine fuels reduction via grazing. Modeling these woodland landscapes requires clear objectives from diverse stakeholders and clear data on woodland structure and key environmental drivers, both of which vary by region.

Publications

  • Type: Theses/Dissertations Status: Published Year Published: 2019 Citation: Donovan, V.M. 2019. Applying ecological resilience theory using scale, pattern, and process. PhD Dissertation, University of Nebraska.
  • Type: Theses/Dissertations Status: Published Year Published: 2020 Citation: Peterson, S.M. 2020. Fuel reduction of ponderosa pine in the Pine Ridge: Impacts on forage production. Masters of Applied Science final project. University of Nebraska.
  • Type: Journal Articles Status: Published Year Published: 2020 Citation: Donovan, V.M., D. Twidwell, D.R. Uden, T. Tadesse, B.D. Wardlow, C.H. Bielski, M.O. Jones, B.W. Allred, D.E. Naugle, and C.R. Allen. 2020. Resilience to large, catastrophic wildfires in North Americas grassland biome. Earths Future 8:e2020EF001487.
  • Type: Journal Articles Status: Published Year Published: 2020 Citation: Donovan, V.M., C.L. Wonkka, D.A. Wedin and D. Twidwell. 2020. Land-use type as a driver of large wildfire occurrence in the U.S. Great Plains. Remote Sensing 12:1869.
  • Type: Journal Articles Status: Published Year Published: 2021 Citation: Roberts, C.P., V.M. Donovan, C.R. Allen, D.G. Angeler, C. Helzer, D. Wedin and D. Twidwell. 2021. Monitoring for spatial regimes in rangelands. 74:114-118.
  • Type: Journal Articles Status: Under Review Year Published: 2021 Citation: Mazis, A., J. Fowler, J. Hiller, Y. Zhou, B.D. Wardlow, D. Wedin and T. Awada. Changes in Ecophysio-Optical Traits of Semiarid Grasslands Vegetation as Impacted by Woody Species Encroachment in the Nebraska Sandhills of the Great Plains. Under Review.
  • Type: Theses/Dissertations Status: Published Year Published: 2019 Citation: Roberts, C.P. 2019. Managing for ecosystem resilience in a non-stationary world. PhD Dissertation, University of Nebraska
  • Type: Journal Articles Status: Published Year Published: 2020 Citation: Roberts CP, V.M. Donovan, S. Nodskov, E. Keele, C.R. Allen, D.A. Wedin, and D. Twidwell. 2020. Fire legacies, heterogeneity, and the importance of mixed-severity fire in ponderosa pine savannas. Forest Ecology and Management. 459, 117853.
  • Type: Journal Articles Status: Published Year Published: 2020 Citation: Fogarty D.T., C.P. Roberts, D.R. Uden, V.M. Donovan, C.R. Allen, D.E. Naugle, M.O.Jones, B.W. Allred and D. Twidwell. 2020. Woody plant encroachment and the sustainability of priority conservation landscapes in Nebraska, USA. Sustainability, 12(20), 8321.
  • Type: Journal Articles Status: Under Review Year Published: 2021 Citation: Donovan V.M., C.P. Roberts, C.L. Wonkka, D.A. Wedin, C.R. Allen, D.G. Angeler, R. Drijber and D. Twidwell. Collapse, reorganisation, and regime identity: breaking down past management paradigms in a forest-grassland ecotone. Ecology and Society, In Review
  • Type: Conference Papers and Presentations Status: Published Year Published: 2020 Citation: Donovan, V.M. Fighting fire with fire: how to reduce wildfire risk in rangelands. Nebraska Natural Legacy Conf. October 2020.


Progress 10/01/18 to 09/30/19

Outputs
Target Audience:In FY2019, the project team met with stakeholders in all three regions dominated by ponderosa pine in Nebraska, includingthe Pine Ridge,Wildcat Hills, and Niobrara Valley regions. All of these sites are designated as Biologically Unique Landscapes (BUL) by the Nebraska Game and Parks Commission, which facilitates stakeholder meetings for each BUL. Stakeholders at our meetings included the Nebraska Forest Service, the US Forest Service, the Nebraska Game and Parks Commission, the Nature Conservancy and the Platte River Basins Environment group. Results were presented at national, regional, andstatewideconferences (see Products). Multiple papers have been published and additional products are currently in peer-review (see Products). Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Three graduate students (Allie Schiltmeyer, Seth Peterson, Victoria Donovan), two undergraduates and one postdoctoral research associate worked with this project in FY2019. How have the results been disseminated to communities of interest?Four peer-reviewedpublications resulted from this project in 2019, including one by an undergraduate student. A Schiltmeyer's MS thesis was completed in FY2019. Students distributed results at hree conference presentations were given, including one invited presentation at an international conference. Research findings were also shared with stakeholders at Nebraska's Legacy Conference, agency and NGO workshops, and through personal communications with personnel at the US Forest Service, NE Forest Service, and The Nature Conservancy. What do you plan to do during the next reporting period to accomplish the goals?V Donovan will defend her PhD research in FY2020 and continue publishing results from the project. Additional analyses will be pursued to complete fire modeling objectives (2.2 and 4.2).

Impacts
What was accomplished under these goals? Nebraska's three ponderosa pine regions (Pine Ridge, Wildcat Hills, and Niobrara Valley) are at risk because of severe wildfires combined with drought, pine beetles and invasive species. For the last several years, this project has been assessing the status of these ponderosa pine woodlands, including their timber resources but also their understory vegetation and fuel loads that drive fire behavior. Large numbers of small, recently established junipers (mainly eastern redcedar) are directly contributing to the loss of resilience for these ponderosa pine woodlands, particularly in the Niobrara Valley. The project has also been assessing the post-fire response, including the regeneration of ponderosa pine and junipers, to intense fires in the Pine Ridge and the Niobrara Valley. The Wildcat Hills, to date, have escaped catastrophic wildfires. This project has used these data to model spatial attributes contributing to the resilience of ponderosa pine to wildfire acrossthese landscapes, with implications for management that includesfuels reduction. Accomplishments related to specific objectives 1.1 Establish permanent plots: This specific objective has been successfully completed. Permanent plots had been established across all three landscapes in previous years of the project. This project compiled independently-conducted data inventoriesWildcat Hills, Pine Ridge and Niobrara Valley. This included data used intheWestern Nebraska Timber SupplyStudy Report as well as field sampling initiated in 2016-2017 in the Wildcat Hills and Niobrara Valley as part of this project. 1.2Validate existing high spatial resolution maps: In previous year's work, it was determined that neither the National Land Cover Database (NLCD), nor LANDFIRE land cover classes effectively distinguishedbetween open (e.g. <70 trees per hectare) and savanna (e.g. < 450 trees per hectare) vegetation in our study sites. New spatial monitoring platforms have come available that provide continuous estimates of vegetation cover each year. In 2019,we started exploring the use of these technologies to track changes in tree cover across the three ecoregions. 2.1 Collect forest fuels data: This specific objective has been successfully completed.Data collected include herbaceous and forest floor biomass, coarse woody debris and recruitment of juniper seedlings and saplings. Data have been published as part of ASchiltmeyer's thesis. 2.2Run fire science models: We have initated modeling of ponderosa pine stand collapsefollowing wildfire using spatially-explicit landscape attributes. Initial modelsrevealed that, within burned areas, areas with higher topographic roughness in the Pine Ridge were more likely to experience high severity fires. More connected (larger) standswere also more likely to experience wildfire driven collapse. Additional analyses are being conducted to more thoroughly assess the spatial contex of wildfire-driven collapse and the relationships betweenconnectivity and topographic roughness on stand persistence. 3.1 Measure pine survival and regeneration: Results for all three systems have been reported in FY2017 and FY2018. Data have been published in peer review (see Products) as well as inASchiltmeyer's thesis. 4.1 Assess fuels reduction and thinning impacts: V Donovan's dissertation research assessed trade-offs among post-wildfire fuels treatments for fuels reduction, ponderosa pine regeneration, and habitat conservation and this assessment has been published in peer-review (see Products). Ponderosa pine saplings were more abundant in treated burned sites than untreated burned sites, suggesting increases in tree regeneration following tree planting. However,natural regeneration was evident in both unburned and untreated burned sites. While treated areas greatly reduced snags and coarse woody debris, double the avian richness was observed on untreated sites.In addition, S Peterson (MS student) has been collecting samples to assess fuels reduction treatments and subsequentherbaceous productivity response. Analysis of data will be a goal of future work. 4.2 Model fire response to fuels management: Only preliminary analyses have been conducted to his point.

Publications

  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Arterburn J, D Twidwell, CL Wonkka, WH Schacht, DA Wedin. 2019. Restoring fire-grazer interactions to pursue heterogeneity in Sandhills grassland. Frontiers in Ecology and Evolution 7: 365.
  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Roberts CP, VM Donovan, CL Wonkka, LA Powell, CR Allen, DG Angeler, DA Wedin, D Twidwell. 2019. Fire legacies in eastern ponderosa pine forests. Ecology and Evolution 9:1869-1879.
  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Donovan VM, CP Roberts, CL Wonkka, DA Wedin, D Twidwell. 2019. Ponderosa pine regeneration, wildland fuels management, and habitat conservation: Identifying trade-offs following wildfire. Forests 10:286.
  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Keele EC, VM Donovan, CP Roberts, S Nodskov, CL Wonkka, CR Allen, L Powell, D Wedin, DG Angeler, D Twidwell. 2019. Relationships between burn severity, cavity-dwelling birds, and habitat in Ponderosa Pine forest. American Midland Naturalist 181:1-18.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: Roberts CP, Donovan VM, Wonkka CL, Powell LA, Allen CR, Angeler DG, Wedin D, Twidwell D. 2019. Fire legacies drive complexity in eastern ponderosa pine stand structure and biodiversity. North American Forest Ecology Workshop. Flagstaff, AZ.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: Donovan VM, and Twidwell D. 2019. Tracking wildfire driven regime shifts across a biome: implications for ecosystem restoration. Society for Ecological Restoration World Conference, Cape Town, South Africa. **featured in invited symposium titled Advancing resilience theory for restoration science.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: Donovan VM, Roberts CP, Wonkka CL, Uden DR, Angeler DG, Allen CR, Wedin D, Drijber RA, Twidwell D. 2019. Collapse, reorganization, and regime identity. North American Forest Ecology Workshop. Flagstaff, AZ.
  • Type: Theses/Dissertations Status: Published Year Published: 2018 Citation: Schiltmeyer AV. 2018. Assessment of the Ponderosa Pine Woodlands in Nebraska's Wildcat Hills: Implications for Juniperus Encroachment and Management. University of Nebraska-Lincoln.


Progress 10/01/17 to 09/30/18

Outputs
Target Audience:In FY18, we presented our results at state (Nebraska Natural Legacy Conference and Nebraska Prescribed Fire Council), regional (Great Plains Fire Science Consortium), and international (Canadian Institute of Forestry) meetings. These groups include both scientists and stakeholders. We also published two scientific papers, have two in press, and several in review (as of December 2018). Locally, both Wedin and Twidwell participated in discussions and writing resulting in a Strategic Plan for Forestry Research at the University of Nebraska. UNL's current and recent portfolio of McIntire-Stennis projects were a key part of this document. Changes/Problems:In FY2018, we reversed the roles of David Wedin as Project Director and Dirac Twidwell as co-project director. Twidwell will be Project Director for the remainder of this project and Wedin will be co-project director. What opportunities for training and professional development has the project provided?Four graduate students (Allie Schiltmeyer, Seth Peterson, Victoria Donovan and Caleb Roberts) and one undergraduate worked with this project in FY2018. While only Allie's stipend was funded by this grant, Victoria and Caleb presented at conferences and submitted manuscripts for research associated with this projecct. Undergraduate Emma Keele has a manuscript in press (2019) related to her work on this project. How have the results been disseminated to communities of interest?Our team had two journal articles published in FY18, two manuscripts in press (FY19), and made 4 conference publications in FY18. Two of the presentations were made at the annual meeting of Nebraska's Natural Legacy Project, which brings together diverse stakeholders, state agencies and federal agencies. Our results were also shared with the Nebraska Invasive Species Council and the Nebraska Prescribed Fire Council. What do you plan to do during the next reporting period to accomplish the goals?A. Schiltmeyer will finish her MS thesis on the Wildcat Hills (Dec 2019), while research continues for V. Donovan, C. Roberts and S. Peterson. We will also focus on comparing stand structure, landscape configuration, fuel loading and potential fire behavior across Nebraska's three ponderosa pine regions. In addition to these analyses, V. Donvan's PhD dissertation will scale up to regional (Great Plains) and national scales to look at the interaction of changing land cover, climate and wildland fire.

Impacts
What was accomplished under these goals? Nebraska's three ponderosa pine regions (Pine Ridge, Wildcat Hills, and Niobrara Valley) are at risk because of severe wildfires combined with drought, pine beetles and invasive species. For the last several years, this project has assessed the status of these ponderosa pine woodlands, including their timber resources but also their understory vegetation and fuel loads that drive fire behavior. Large numbers of small, recently established junipers (mainly eastern redcedar) are directly contributing to the loss of resilience for these ponderosa pine woodlands, particularly in the Niobrara Valley. The project has also been assessing the post-fire response, including the regeneration of ponderosa pine and junipers, to intense fires in the Pine Ridge and the Niobrara Valley. The Wildcat Hills, to date, have escaped catastrophic wildfires. In future years, this project will use this data to model potential fire behavior across these three landscapes, including the potential benefits of management such as fuels reduction. Accomplishments related to specific objectives 1.1 Establish permanent plots: In May 2018, the Nebraska Forest Service released the "Western Nebraska Timber Supply Study Report" (86 pages), which was designed, funded and implemented in cooperation with this McIntire Stennis project. When combined with our data from research projects in the Wildcat Hills, Pine Ridge and Niobrara Valley, we now have data on both woodland structure and distribution in all of Nebraska's ponderosa pine regions. These results highlight the large differences among the pine woodlands of Nebraska's three Great Plains ponderosa pine regions. For example: the Wildcat Hills landscape has less <10% dense woodland stands and >55% open savanna, while the Niobrara Valley has >60% dense stands and < 15% oven savanna. The Pine Ridge, in contrast, has >65% intermediate density stands. Regarding woodland species composition, inventories in the Pine Ridge find >95% ponderosa pine, compared to 75% pine in the Wildcat Hills, and <30% pine in the Niobrara Valley, where junipers are the most abundant species. 1.2 Validate existing high spatial resolution maps: We continue to compare stand-level survey data with various regional and national land classification based on remote sensing. One conclusion from A. Schiltmeyer's research was that neither the National Land Cover Database (NLCD) nor LANDFIRE land cover classes are good at distinguishing between open (e.g. <70 trees per hectare) and savanna (e.g. < 450 trees per hectare) vegetation in our study sites. 2.1 Collect forest fuels data: This has been done as part of the field work discussed in Objective 1.1. Data collected include herbaceous and forest floor biomass, coarse woody debris and recruitment of juniper seedlings and saplings. As discussed in 1.1., we are finding large differences across the three ponderosa pine regions. 2.2 Run fire science models:In preliminary analyses we have parameterized our three study regions using standard US federal fire behavior models (e.g. BehavePlus, FlamMap, CIFS). In particular, we are testing whether the spatial distribution of stand structure, which differs sharply across the three regions, creates critical thresholds for fire behavior. This is ongoing research with no accomplishments to report for FY2018. 3.1 Measure pine survival and regeneration: Extensive results for the PIne Ridge and Niobrara Valley were reported for FY2017. A fascinating conclusion from our Wildcat Hills research was that many of the small pines (<10 cm diamer) found in open grasslands and savannas are over 50 years old, in contrast to small pines in denser stands, which averaged less than 30 years old. Tree ring analyses of open and dense pine populations in the Wildcat Hills indicate that open pines are more resilient than dense pines in response to three dramatic drought cycles between 2000 and 2016.In a related effort, we continue to collaborate with the Nebraska Forest Service on a study of survivorship and performance of transplanted ponderosa pine seedlings that contrasts bare root and different types of container stock. 4.1 Assess fuels reduction and thinning impacts: A new study of past fuels reduction projects in the Pine Ridge was begun by MS student Seth Peterson in FY2018, but there are no results to report yet. 4.2 Model fire response to fuels management: No accomplishments yet for this objective.

Publications

  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Adane, Z., P. Nasta, V. Zlotnik, & D. Wedin. 2018. Impact of grassland conversion to forest on groundwater recharge in the Nebraska Sand Hills. Journal of Hydrology: Regional Studies 15:171-183.
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Arterburn, J., D. Twidwell, W.H. Schacht, C.L. Wonkka, & D.A. Wedin. 2018. Resilience of Sandhills grassland to wildfire during drought. Rangeland Ecology and Management, 71:53-57.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2017 Citation: Post-fire management legacy effects in severely burned ponderosa pine savanna. Nebraska Natural Legacy Conference, Oct 2017. (VM Donovan, CP Roberts, CL Wonkka, D Wedin, D Twidwell)
  • Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Post-fire management alters structural and community characteristics of eastern ponderosa pine forest. Canadian Institute of Forestry, Grande Prairie, Alberta, September 2018 (V.M. Donovan, C.P. Roberts, C. Wonkka, D. Wedin, D. Twidwell)
  • Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: The status and future of Nebraska⿿s Pinus ponderosa landscapes: the Wildcat Hills. International Assoc. for Landscape Ecology (US-IALE), Chicago, Illlinois, April 2018 (A.V. Schiltmeyer, D.A. Wedin, D. Twidwell)
  • Type: Conference Papers and Presentations Status: Published Year Published: 2017 Citation: A stand scale assessment of Nebraska Wildcat Hills forests, woodlands and mixed-grass prairie. Nebraska Natural Legacy Conference, Oct 2017. (A.V. Schiltmeyer & D.A. Wedin)


Progress 10/01/16 to 09/30/17

Outputs
Target Audience:In FY2017, the project team met with stakeholders in both the Pine Ridge and Wildcat Hills regions of Nebraska. Both of these sites are designated as Biologically Unique Landscapes (BUL) by the Nebraska Game and Parks Commission, which facilitates stakeholder meetings for each BUL. Stakeholders at our meetings included from the Nebraska Forest Service, the US Forest Service, the Nebraska Game and Parks Commission, the Nature Conservancy and the Platte River Basins Environment group. We also presented our results at statewide and regional conferences (see Products). Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Three graduate students (Allie Schiltmeyer, Victoria Donovan, and Caleb Roberts) and three undergraduates worked with this project in FY2017. While only Allie's stipend was funded by this grant, all three graduate students continued their field work, presented at conferences, and submitted manuscripts for their research associated with this project. Our undergraduate student Emma Keele was also lead author on a research manuscript submitted for review. How have the results been disseminated to communities of interest?Two manuscripts have been submitted to peer-reviewed journals for publication (in review), and the team made several presentations to the Nebraska Natural Legacy Conference (statewide audience) and the Midwest Fish and Wildlife Conference (regional conference). In addition, we submitted a final report on a two-year study of severe wildfires in Nebraska's Pine Ridge region. This report was presented to Nebraska's Natural Legacy Project, a diverse group of agencies, stakeholders and private citizens brought together by the Nebraska Game and Parks Commission as part of Nebraska's state wildlife plan. What do you plan to do during the next reporting period to accomplish the goals?Research by our projects' three graduate students will continue, with thesis completion anticipated for A. Schiltmeyer (MSc) and V. Donovan (PhD). We also plan to begin comparison of stand structure, landscape configuration and fuel loading for Nebraska's three eastern ponderosa pine regions. This will integrate our timber inventories collected in the Wildcat Hills with a 130,000 acre inventory conducted, with our cooperation, by the Nebraska Forest Service in the Pine Ridge and Niobrara Valleys. This will allow preliminary modeling of fuel and fire scenarios across these three regions.

Impacts
What was accomplished under these goals? Nebraska's three ponderosa pine regions (Pine Ridge, Wildcat Hills, and Niobrara Valley) are at risk because of severe wildfires combined with drought, pine beetles and invasive species. The loss of these woodlands has accelerated in recent decades. These losses impact recreation, timber, water and soils resources, and habitat for a broad range of plant and animal species. For the last several years, this project has been assessing the status of these ponderosa pine woodlands, including their timber resources but also their understory vegetation and fuel loads that drive fire behavior. Large numbers of small, recently established junipers (mainly eastern redcedar) are directly contributing to the loss of resilience for these ponderosa pine woodlands, particularly in the Niobrara Valley. The project has also been assessing the post-fire response, including the regeneration of ponderosa pine and junipers, to intense fires in the Pine Ridge and the Niobrara Valley. In severely burned sites, the establishment of new pine seedlings is rare. The Wildcat Hills, to date, have escaped catastrophic wildfires. In future years, this project will use this data to model potential fire behavior across these three landscapes, including the potential benefits of management including fuels reduction. Accomplishments related to specific objectives 1.1 Establish permanent plots: As of October 2017, we have established vegetation inventory plots in all three research landscapes (Pine Ridge, Wildcat Hills, Niobrara Valley). In the Niobrara Valley and the Pine Ridge, the Nebraska Forest Service (in cooperation with our project) completed an extensive (130,000 acre) forest inventory in 2017. Those data are being analyzed. In 2016-2017, we established 60 permanent plots in the Wildcat Hills to assess the density and size structure of ponderosa pine and juniper populations, as well as fuel loading and understory vegetation. Tree ring results from 2017 the Wildcat Hills are similar to our tree ring analyses from the Niobrara Valley. At both sites, ponderosa pine has a broad age distribution, with a median age of approximately 60 years in the Niobrara Valley and 90 years in the Wildcat Hills. In contrast, junipers in both landscapes are overwhelmingly small (mean diameters <6cm) and young. Our graduate students have presented analyses of vegetation structure from all three research landscapes at state and national meetings, but to date, those analyses have not directly compared and contrasted the three landscapes, a long-term goal of this project. 1.2 Validate existing high spatial resolution maps: To date we have used existing high spatial resolution land cover classifications (USGS/NLCD), fire severity maps (MTBS), and unsupervised land cover classifications (LANDSAT) to choose inventory plots randomly stratified by land cover. Our research landscapes differ in land cover. For example, the Niobrara Valley's pine woodlands have approximately 40% open grassland (30m x 30m pixels), while much of the Wildcat Hills landscape is approximately 70% open grassland and only 30% wooded. However, these preexisting land cover classifications discriminate poorly between low and high-density pine woodlands in our data set. For example, our Wildcat Hills data indicate that plots with 100 to 500 trees per hectare have significantly lower juniper encroachment and forest floor biomass (e.g. pine needles, cones) than higher density plots. This suggests a threshold above which fire intensity increases dramatically, compromising the resilience of the pine stand. Identifying such thresholds in our data and incorporating them into alternative land cover classifications using remote sensing imagery is a key step toward our long-term goal of modeling fire risk at the landscape scale (Objective 4.2). 2.1 Collect forest fuels data: Because our team has different graduate student projects in our three research landscapes, our vegetation inventory methods vary. However, in 2017 we collected data from all sites on stand density, basal area, height, coarse woody debris, canopy fuel stratum gap, and surface fine fuels. These data will be analyzed during 2018 and used for preliminary modeling of stand-level fire behavior models (Objective 2.2) 2.2 Run fire science models: No accomplishments to date for this objective 3.1 Measure pine survival and regeneration: After using remote sensing imagery to choose randomized plots, we conducted post-fire vegetation surveys after the 2012 Niobrara Valley Fire (surveys in 2014-2017) and the 2006 Dawes Fire in the Pine Ridge (surveys in 2015-2017). Data collected include pine and juniper recruitment, recovery of herbaceous and shrub vegetation, and coarse woody debris. While the Pine Ridge post-fire landscape is a mosaic of high severity and low severity sites, the Niobrara valley post-fire landscape contained large (>1000 acres) continuous patches of severely burned woodland with >95% pine and juniper mortality. Recruitment of pine and juniper seedlings within severely burned areas in either landscape is very low. In the Niobrara Valley, many of the plots are revegetating as grassland or oak woodland from resprouting oak stumps. These results were presented at national and state conferences by graduate students in 2016 and 2017, and are in preparation or review for publication. A final report on the impact of severe wildfires on vegetation in the Pine Ridge was presented to the Nebraska Game and Parks Commission's Natural Legacy Project in July 2017. The low rate of post-fire juniper recruitment is good news for Nebraska land managers, who struggle with juniper encroachment into rangeland and woodlands. These results confirmed earlier reports of poor post-fire pine regeneration and poor survivorship for planted pine seedlings in western Nebraska post-fire locations. To address this ponderosa pine regeneration challenge, we partnered with the Nebraska Forest Service on a new experiment comparing bare-root and three types of containerized ponderosa pine seedlings at multiple sites across Nebraska. Our team is responsible for the replicate planted at UNL's Agroforestry Research Farm. 4.1 Assess fuels reduction and thinning impacts: No accomplishments to date for this objective. 4.2 Model fire response to fuels management: No accomplishments to date for this objective.

Publications

  • Type: Conference Papers and Presentations Status: Published Year Published: 2017 Citation: Influences of mixed severity and time since fire on diversity in ponderosa habitats. Nodskov, S. D.P. Roberts, V.M. Donovan, E.Keele, D.Wedin, C.R. Allen, L. Powell, C.L. Wonkka, D.G. Angeler and D. Twidwell. Midwest Fish and Wildlife Conference (Lincoln, NE, February 2017)
  • Type: Conference Papers and Presentations Status: Published Year Published: 2016 Citation: The influence of fire severity on community structure in Nebraska's Pine Ridge. Donovan, V.P., C.P. Roberts, C.L. Wonkka and D. Twidwell. Nebraska Natural Legacy Conference (October 2016)
  • Type: Conference Papers and Presentations Status: Published Year Published: 2017 Citation: Long-term legacy effects of a mixed-severity wildfire in eastern ponderosa pine. Roberts, C.P., V.M. Donovan, D. Wedin, C.R. Allen, L. Powell, C.L. Wonkka, D.g. Angeler, and D. Twidwell. Midwest Fish and Wildlife Conference (Lincoln, NE, February 2017)
  • Type: Other Status: Published Year Published: 2017 Citation: Final Report: Impact of severe wildfires on the pine forest and mixed-grass prairie vegetation of the Pine Ridge Biologically Unique Landscape (Nebraska Natural Legacy Project W-125-R-1). Twidwell, D., C. Wonkka, V. Donovan and C. Roberts.


Progress 01/11/16 to 09/30/16

Outputs
Target Audience:The project met with stakeholders in our three Nebraska target research areas (Pine Ridge, Niobrara Valley, and Wildcat Hills) in 2016. In the Niobrara Valley, this included on-going collaboration and data collection with Nature Conservancy (TNC) staff at the Niobrara Valley Preserve. In the Pine Ridge, this included a June planning session with Nebraska Forest Staff in Chadron, a June meeting with approximately 15 diverse agency staff in Chadron, on-going collaboration with our graduate students Caleb Roberts and Tori Donovan with US Forest Service staff to address prescribed fire and coarse woody debris. To plan our new Wildcat Hills research, we met in Spring 2016 with staff from Nebraska Game and Parks Commission (NGPC), Platte River Basin Environments (PRBE), and TNC. Our new graduate student Allie Schiltmeyer collected data on both PRBE and NGPC properties during the summer and fall of 2016. Graduate student Caleb Roberts and co-PI Twidwell presented to state wide audiences of natural resource professionals at the Nebraska Natural Legacy Conference and the Nebraska Prescribed Fire Conference. Finally, we published an article on Pine Ridge Wildfire Research in the NGPC magazine NebraskaLand (monthly readership of 100,000). Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Three graduate students (Allie Schiltmeyer, Caleb Roberts and Tori Donovan) and two undergraduates worked with this project during 2016. While only Allie was fully funded by the project, but all three grad students supervised our two undergrads for field work in our three research areas. Both Caleb and Tori prepared and presented at scientific meetings (see products). How have the results been disseminated to communities of interest?The project met with stakeholders in our three Nebraska target research areas (Pine Ridge, Niobrara Valley, and Wildcat Hills) in 2016. In the Niobrara Valley, this included on-going collaboration and data collection with Nature Conservancy (TNC) staff at the Niobrara Valley Preserve. In the Pine Ridge, this included a June planning session with Nebraska Forest Staff in Chadron, a June meeting with approximately 15 diverse agency staff in Chadron, on-going collaboration with our graduate students Caleb Roberts and Tori Donovan with US Forest Service staff to address prescribed fire and coarse woody debris. To plan our new Wildcat Hills research, we met in Spring 2016 with staff from Nebraska Game and Parks Commission (NGPC), Platte River Basin Environments (PRBE), and TNC. Our new graduate student Allie Schiltmeyer collected data on both PRBE and NGPC properties during the summer and fall of 2016. Graduate student Caleb Roberts and co-PI Twidwell presented to state wide audiences of natural resource professionals at the Nebraska Natural Legacy Conference and the Nebraska Prescribed Fire Conference. Finally, we published an article on Pine Ridge Wildfire Research in the NGPC magazine NebraskaLand (monthly readership of 100,000). What do you plan to do during the next reporting period to accomplish the goals?During 2017, we will emphasize further field work on stand structure and woodland distribution in the Wildcat Hills and Pine Ridge, as well as annual resampling in the post-fire study area in the Niobrara Valley (objective 1.1 and 2.1). With basic georeferenced stand data from all three areas, we can begin calibration of remote sensed land cover classifications (GIS) for the study areas (objective 1.2). This will allow preliminary modeling of fuel and fire scenarios at the landscape scale (objective 2.2). Our discussions with project partners and stakeholders in 2016 made clear that better data is needed on grassland/rangeland response to woodland management or fire. Because cattle grazing is a dominant land use, forage quality and quantity in these landscapes drives many of the private landowners decisions on management, including cost-share programs for fuels reduction. We will begin to address this topic in the Pine Ridge in 2017, but details are to be determined.

Impacts
What was accomplished under these goals? A) Following planning meetings with stakeholders (state and local agencies and NGO's), we designed and initiated field work in the Wildcat Hills region of Nebraska. The field crew, let by grad student Allie Schiltmeyer, collected data on stand structure (tree dbh, height), seedling density, understory vegetation and dead wood at 41 sites randomly chosen in two areas. The data base of over 400 individual ponderosa pine and juniper trees indicates that size distributions for pine was comparable between the Wildcat Hills and the Niobrara Valley, but average juniper size was larger in the Wildcat Hills. In contrast, juniper density in Wildcat Hills woodland areas was lower (200 trees/ha) than in the Niobrara Valley (500 trees/ha), while pine density was higher for the Wildcat Hills than the Niobrara Valley (320 vs 100 trees/ha). The dense juniper understory is, in effects, ladder fuel, which aggravated wildfire behavior in the Niobrara Valley in 2012. B) We had several new and old projects in the Pine Ridge region: 1) completed post-wildlife sampling of stand structure in 2012 wildfires; 2) completed surveys of herbaceous invaders on public lands in the Pine Ridge; 3) developed a map showing current status of herbaceous invaders in the Pine Ridge; 4) implemented community sampling for beetles and birds across different fire severities; 5) initiated data analysis on the differences in herbaceous plant communities across a fire severity gradient. C) Our field crew spent one week resampling points within the 2012 post-fire study area at the Niobrara Valley Preserve. This provides us with a data time series on tree seedling recruitment, herbaceous vegetation recovery, and shifts in the post-fire coarse woody debris load.

Publications

  • Type: Conference Papers and Presentations Status: Published Year Published: 2016 Citation: Roberts, C.P., V.M.Donovan, L.Powell, C.R.Allen, C.Wonkka, D.Wedin and D.Twidwell. 2016. Long-term legacy effects of a mixed-severity wildfire in eastern ponderosa pine. Nebraska Prescribed Fire Conference (Kearney, NE, Dec 2, 2016).
  • Type: Other Status: Published Year Published: 2016 Citation: Wonkka, C., D.Twidwell, and D.A.Wedin. 2016. Pine Ridge Wildfire Research. Nebraskaland (July, Page 41).
  • Type: Conference Papers and Presentations Status: Published Year Published: 2016 Citation: Hefner, A.M., and D.A.Wedin. 2016. Regeneration of ponderosa pine woodland following severe wildfire in the Niobrara River Valley. Society for Range Management (Corpus Cristi TX, Jan31-Feb4 2016)
  • Type: Conference Papers and Presentations Status: Published Year Published: 2016 Citation: Roberts, C.P., V.M.Donovan, L.Powell, C.R.Allen, C.Wonkka, D.Wedin and D.Twidwell. 2016. Long-term legacy effects of a severe wildfire in eastern ponderosa pine. Nebraska Natural Legacy Conference (Broken Bow, NE, Sept 21-22, 2016).