Recipient Organization
UNIVERSITY OF NEVADA
(N/A)
RENO,NV 89557
Performing Department
Ag Nutrition and Vet Sciences
Non Technical Summary
As of September, 8.7 million acres have burned in the western United States in 2012, one third or 2.6 million acres were in the Great Basin (NIFC 2012). Wildfires burning in plant communities invaded or dominated by cheatgrass and other annual invasive weeds can be difficult and costly to control, making fuels management desirable. Much of the acres burned in 2012 were federally managed by the Bureau of Land Management (BLM) or Forest Service (FS). The permittees that graze livestock on these public lands will likely lose their ability to graze for at least the next two years, under the premise that bunchgrasses need rest from grazing to survive and recover after fire. Rangelands that have been invaded by cheatgrass may have marginal perennial bunchgrass response due to subsequent competition with annual invasive weeds. However, cheatgrass will continue to grow each year and increase the fine fuel load; which after two years could easily prime these burned and rested lands for another catastrophic wildfire. The proposed project directly relates to the NAES research priority of natural resource management and environmental sciences in the Great Basin ecosystems. This project will test the vegetative response of post-burn plant communities to different grazing treatments at the disturbance response group (DRG) level. A DRG is a group of ecological sites that respond similarly to disturbance, although the rate of change or recovery may vary between sites. DRGs bring ecologically based management to a scale relevant for land managers. This project will also parameterize the state-and-transition model developed for each selected DRG. Results from this project will enhance ecologically based understanding of the effects burning and post-fire grazing on perennial bunchgrasses and fine fuel loading, especially in the Great Basin. Project results will help land managers stratify post-fire management decisions across large landscapes based on pre-fire condition, measured plant community response and quantified ecological thresholds. Additionally, project results will help land managers make effective post-fire restoration decisions by providing the information needed to define at-risk landscapes and trigger events. Additionally, if managers understand the impacts of grazing to these vulnerable yet dynamic landscapes, they can use grazing as a fuels management tool to reduce the potential for future catastrophic wildfire events while promoting commuity recovery post-fire.
Animal Health Component
100%
Research Effort Categories
Basic
(N/A)
Applied
100%
Developmental
(N/A)
Goals / Objectives
1. Provide a discussion platform for university and federal scientists working on the development and interpretation of ecological site descriptions (ESDs) and state-and-transition models (STMs) with special emphasis of describing thresholds and ecosystem services. 2. Encourage research toward the definition and quantification of ecological thresholds as well as the evaluation of ecosystem services lost or gained with different transitions. 3. Introduce the concepts of ESDs and STMs to diverse rangeland audiences and how ecosystem services can be integrated into the process to determine value of management outcomes guided by STMs.
Project Methods
RESEARCH METHODOLOGY Study locations will be limited to areas that have not burned within 10 years of the current wildfire. Within a wildfire burned pasture or allotment, two disturbance response groups (DRGs) will be identified. Since pre-fire sampling is not possible for wildfires, study locations will be determined post-burn utilizing soil map units and correlated ecological sites, followed by on-site verification (landform, aspect, elevation). Site verification will eliminate sampling of minor components within soil map units. Targeted DRGs will include those with ecological sites dominated by Wyoming big sagebrush, mountain big sagebrush or low sagebrush in Major Land Resource Areas (MLRA) 23, 24 and/or 25 (Table 1). DRGs have been defined for MLRA 24 and 25 in Nevada (Stringham 2011; Stringham et al. 2011a; Stringham et al. 2012) and MLRA 23 and 24 in Oregon (Stringham 2009). Currently, each DRG has a modal site, typically the ecological site with the most mapped acres (e.g., MLRA 24, Loamy 8-10). A state-and-transition model (STM) has been created for the modal site from multiple site visits and expert professional knowledge. The DRG assumption is that the other ecological sites within the group will have a similar STM, although the resilience or rate of change may differ from the modal site. Within each of the two identified DRGs, five, one hectare blocks (exclosures) will be randomly located. Each block will have one replication of the three treatments applied (see below), for a total of 30 plots at each location (wildfire). Treatments will be randomly assigned to plots within each block. Small plot defoliation treatments will be accomplished through mechanical means, such as mowing. Each block will be fenced to prevent livestock and wildlife grazing. Landscape level treatments at the DRG scale will be applied according to scheduled grazing management plans, and will be accomplished by livestock. The same DRGs used for small plot treatments will be measured at the larger scale. Two different wildfire locations will be used for this project. Small Plot Treatments: 1. One growing season of rest after fire followed by defoliation during three dormant seasons (after perennial bunchgrasses have set seed), 2. One year rest after fire followed by three years of defoliation during the growing season (prior to perennial bunchgrass seed set), 3. Control: three years of rest post-fire. Landscape Treatment per Disturbance Response Group: 1. Grazing management within the pasture or allotment where the blocks are located will mimic one of the three small plot treatments. Pre-burn condition/plant community will be determined using one or more of the following methods, depending on availability: 1) adjacent unburned areas, 2) BLM monitoring data, 3) National Resource Inventory data, 3) local/professional knowledge, 4) private land owner monitoring, and 5) National Agriculture Imagery Program (NAIP) imagery. All measurements (below) will be collected within each plot once per year at the end of the growing season. Each plot will have five, 30 m transects for collection of the plant and soil measurements. Sample size calculations will be used to determine sampling intensity. Please refer to the timeline (next section) for dates of treatment application and data collection. Herbaceous community measurements will include canopy and basal cover using the line-point intercept method (Elzinga et al. 1998), plant composition, and basal gap (Herrick et al. 2005). Vegetation height, an important factor for wildlife habitat, will be measured by functional group. If present, shrub cover will be measured by the line intercept method and shrub density will be measured using a belt transect (Elzinga et al. 1998). A timed plant census will be conducted within each plot. Standing crop will be collected and separated by live and dead material to get a measure of total annual production by functional group and total fuel loads. To elucidate the effect of grazing/defoliation treatments, plant height and standing crop will be collected preand post-treatment application each year. These herbaceous measurements are related to risk of weed invasion or increase in weeds, wind and water soil erosion, runoff and energy capture. Additionally, soil aggregate stability will be measured , which directly relates to soil resistance to erosion (Herrick et al. 2005). The plant measurements and soil aggregate stability relate to the temporal and spatial capture of energy and nutrient cycling, or site processes. Hydrologic function will be tested by measuring infiltration rate with the double ring infiltrometer test (Bouwer 1986). In total, these measurements are how biotic and abiotic thresholds, at-risk communities, and ecological resilience are assessed and measured. Therefore, all measurements will be used to assess thresholds and parameterize the state-and-transition models associated with each disturbance response group. Additional environmental measurements will be collected within each DRG at each location (4 collection areas). Theseenvironmental variables may include soil texture, soil pH, soil moisture, growing season precipitation, number of growing days, slope, aspect, elevation, etc. These variables will further define DRG characteristics and inherent DRG differences. These variables become the environmental matrix which is used for multivariate analyses. For the large scale management application assessment, within each pasture or allotment, several transects will be randomly located within each of the two selected DRGs. All of the above mentioned plant and soil measurements will occur on these transects once per year at the end of the growing season. At this time, it is unknown what the treatment will be to these larger areas and will depend on ownership and current ranch management plans or allotment permits. If livestock grazing occurs within the large scale areas, pre- and post-grazing measurements of plant height and standing crop will be collected. Disturbance response group and treatment differences will be tested using analysis of variance (ANOVA) with F-protected least significant difference (LSD) for mean comparisons. Multivariate statistical techniques (e.g., non-metric multidimensional scaling, hierarchical cluster analysis, indicator species, etc.) will be utilized to assess threshold values and community response at the disturbance response group level. These multivariate techniques are more robust and appropriate for understanding community response rather than single species response (McCune and Grace 2002). Additional statistical analyses may be conducted to better answer the research questions.