Wildland Resources Faculty Publications
Wildland Resources Faculty Publications Recent documents in Wildland Resources Faculty Publications
- Winter Feeding of Elk in the Greater Yellowstone Ecosystem and its Effects on Disease Dynamicsby Gavin Coterill et al. on November 18, 2020 at 10:09 pm
Providing food to wildlife during periods when natural food is limited results in aggregations that may facilitate disease transmission. This is exemplified in western Wyoming where institutional feeding over the past century has aimed to mitigate wildlife–livestock conflict and minimize winter mortality of elk (Cervus canadensis). Here we review research across 23 winter feedgrounds where the most studied disease is brucellosis, caused by the bacterium Brucella abortus. Traditional veterinary practices (vaccination, test-and-slaughter) have thus far been unable to control this disease in elk, which can spill over to cattle. Current disease-reduction efforts are being guided by ecological research on elk movement and density, reproduction, stress, co-infections and scavengers. Given the right tools, feedgrounds could provide opportunities for adaptive management of brucellosis through regular animal testing and population-level manipulations. Our analyses of several such manipulations highlight the value of a research–management partnership guided by hypothesis testing, despite the constraints of the sociopolitical environment. However, brucellosis is now spreading in unfed elk herds, while other diseases (e.g. chronic wasting disease) are of increasing concern at feedgrounds. Therefore experimental closures of feedgrounds, reduced feeding and lower elk populations merit consideration.
- Do Plant Secondary Metabolite‐Containing Forages Influence Soil Processes in Pasture Systems?by Andrea K. Clemensen et al. on September 9, 2020 at 8:31 pm
Grazed pastures are susceptible to N loss from urine/manure additions, which increases eutrophication, affecting the global N cycle. Plant secondary metabolites (PSM), such as condensed tannins (CT) and terpenes, influence silviculture soil dynamics by generally decreasing N mineralization. We investigated whether cattle‐grazed pastures of non‐traditional grass and legume forage monoculture strips including CT‐containing sainfoin (Onobrychis viciifolia Scop.) and tall fescue (TF) [Schedonorus arundinaceus (Schreb.) Dumort.] influenced soil dynamics compared with traditional grass and legume forage monoculture strips of alfalfa (Medicago sativa L.), without tannins, and TF. Throughout the study, CT in sainfoin averaged 58.9 g kg−1 whereas alfalfa saponins averaged 5.7 g kg−1. We observed greater soil microbial respiration (p = .01) in TF strips than legume strips, indicating greater microbial activity, and between legumes we found greater soil NO3 (p = .01) in alfalfa than in sainfoin, although aboveground biomass and N differences were negligible. We also conducted a laboratory soil‐feces incubation study to determine if feces from cattle foraging diets of legumes with or without CT influenced soil dynamics. Both feces treatments showed lower NO3 (p p = .03) in sainfoin than alfalfa feces, suggesting CT from sainfoin inhibit DHEA. To our knowledge this study is the first considering whether CT‐containing sainfoin and saponin‐containing alfalfa influence soil dynamics by assessing general differences in soil parameters. More research is needed to determine whether specific PSM mitigate N loss in pasture systems by slowing N mineralization.
- Large-Diameter Trees Dominate Snag and Surface Biomass Following Reintroduced Fireby James A. Lutz et al. on August 5, 2020 at 8:37 pm
The reintroduction of fire to landscapes where it was once common is considered a priority to restore historical forest dynamics, including reducing tree density and decreasing levels of woody biomass on the forest floor. However, reintroducing fire causes tree mortality that can have unintended ecological outcomes related to woody biomass, with potential impacts to fuel accumulation, carbon sequestration, subsequent fire severity, and forest management. In this study, we examine the interplay between fire and carbon dynamics by asking how reintroduced fire impacts fuel accumulation, carbon sequestration, and subsequent fire severity potential. Beginning pre-fire, and continuing 6 years post-fire, we tracked all live, dead, and fallen trees ≥ 1 cm in diameter and mapped all pieces of deadwood (downed woody debris) originating from tree boles ≥ 10 cm diameter and ≥ 1 m in length in 25.6 ha of an Abies concolor/Pinus lambertiana forest in the central Sierra Nevada, California, USA. We also tracked surface fuels along 2240 m of planar transects pre-fire, immediately post-fire, and 6 years post-fire. Six years after moderate-severity fire, deadwood ≥ 10 cm diameter was 73 Mg ha−1, comprised of 32 Mg ha−1 that persisted through fire and 41 Mg ha−1 of newly fallen wood (compared to 72 Mg ha−1 pre-fire). Woody surface fuel loading was spatially heterogeneous, with mass varying almost four orders of magnitude at the scale of 20 m × 20 m quadrats (minimum, 0.1 Mg ha−1; mean, 73 Mg ha−1; maximum, 497 Mg ha−1). Wood from large-diameter trees (≥ 60 cm diameter) comprised 57% of surface fuel in 2019, but was 75% of snag biomass, indicating high contributions to current and future fuel loading. Reintroduction of fire does not consume all large-diameter fuel and generates high levels of surface fuels ≥ 10 cm diameter within 6 years. Repeated fires are needed to reduce surface fuel loading.
- Investigating the Dynamics of Elk Population Size and Body Mass in a Seasonal Environment Using a Mechanistic Integral Projection Modelby Shelly Lachish et al. on July 30, 2020 at 10:51 pm
Environmentally mediated changes in body size often underlie population responses to environmental change, yet this is not a universal phenomenon. Understanding when phenotypic change underlies population responses to environmental change is important for obtaining insights and robust predictions of population dynamics in a changing world. We develop a dynamic integral projection model that mechanistically links environmental conditions to demographic rates and phenotypic traits (body size) via changes in resource availability and individual energetics. We apply the model to the northern Yellowstone elk population and explore population responses to changing patterns of seasonality, incorporating the interdependence of growth, demography, and density-dependent processes operating through population feedback on available resources. We found that small changes in body size distributions can have large impacts on population dynamics but need not cause population responses to environmental change. Environmental changes that altered demographic rates directly, via increasing or decreasing resource availability, led to large population impacts in the absence of substantial changes to body size distributions. In contrast, environmentally driven shifts in body size distributions could occur with little consequence for population dynamics when the effect of environmental change on resource availability was small and seasonally restricted and when strong density-dependent processes counteracted expected population responses. These findings highlight that a robust understanding of how associations between body size and demography influence population responses to environmental change will require knowledge of the shape of the relationship between phenotypic distributions and vital rates, the population status with regard to its carrying capacity, and importantly the nature of the environmentally driven change in body size and carrying capacity.
- Effects of Pyric Herbivory on Prairie-Chicken (Tympanuchus spp) Habitatby Heath D. Starns et al. on July 8, 2020 at 10:14 pm
The reduction and simplification of grasslands has led to the decline of numerous species of grassland fauna, particularly grassland-obligate birds. Prairie-chickens (Tympanuchus spp.) are an example of obligate grassland birds that have declined throughout most of their distribution and are species of conservation concern. Pyric herbivory has been suggested as a land management strategy for enhancing prairie-chicken habitat and stabilizing declining population trends. We assessed differences in vegetation structure created by pyric herbivory compared to fire-only treatments to determine whether pyric herbivory increased habitat heterogeneity for prairie-chickens, spatially or temporally. Our study was performed at four sites in the southern Great Plains, all within the current or historic distribution of either lesser (T. pallidicinctus), greater (T. cupido), or Attwater’s (T. cupido attwateri) prairie-chickens. Key vegetation characteristics of grass cover and vegetation height in pyric herbivory and fire-only treatments were within the recommended range of values for prairie-chickens during their distinct life history stages. However, patches managed via pyric herbivory provided approximately 5% more forb cover than fire-only treatments for almost 30 months post-fire. Additionally, pyric herbivory extended the length of time bare ground was present after fires. Pyric herbivory also reduced vegetation height and biomass, with mean vegetation height in pyric herbivory treatments lagging behind fire-only treatments by approximately 15 months. Canopy cover in fire-only treatments exceeded levels recommended for prairie-chicken young within 12 months post-fire. However, canopy cover in pyric herbivory treatments never exceeded the maximum recommended levels. Overall, it appears that pyric herbivory improves vegetation characteristics reported as critical to prairie-chicken reproduction. Based on our results, we suggest pyric herbivory as a viable management technique to promote prairie-chicken habitat in the southern Great Plains, while still accommodating livestock production.
Dpt. Fisheries & Wildlife
Oregon State University
Corvallis, OR 97330
GB Rangelands Research
USDA Ag. Res. Service
Reno, NV 89512
(775) 784-6057 ext. 233