The School of Natural Resources Graduate Student Research Seminar series in the Spring Semester 2024 are Wednesdays from noon to 1 pm in 163 North Hardin Hall.

This week’s presentations are
Tanessa Morris:
Effect of Biomass Water Dynamics in Cosmic-Ray Neutron Sensor Observations: A Long-Term Analysis of Maize-Soybean Rotation in Nebraska

The precise measurement of soil water content (SWC) is crucial for effective water resource management. This study utilizes the Cosmic Ray Neutron Sensor (CRNS) as a novel technique for area-averaged SWC measurements at an intermediate scale. However, accurate SWC measurements from CRNS require consideration of all hydrogen sources, including time-variable ones like plant biomass and plant water. Near Mead, Nebraska, three field sites (CSP1, CSP2, and CSP3) growing a maize-soybean rotation have been monitored for 5 (CSP1 and CSP2) and 13 years (CSP3), collecting data on biomass water equivalent (BWE) biweekly with destructive sampling, epithermal neutron counts, atmospheric variables, and point-scale SWC from a sparse Time Domain Reflectometry (TDR) network (4 locations and 5 depths). In 2023, dense gravimetric SWC surveys were collected a minimum of 8 times in each field over the growing season. The N0 parameter, derived from the Desilets Equation, exhibits a strong linear relationship with BWE, suggesting a straightforward vegetation correction factor (fb). Results from both the 2023 gravimetric surveys and long-term TDR data indicate a count rate reduction of 1% (+/- 0.5%) for every 1 kg/m2 (or mm of water) increase in biomass for all 3 sites and 2 crop types. This reduction factor aligns well with existing but shorter-term studies in croplands and forests. The higher count rate detector model #CRS 2000B model at CSP1 and CSP2 significantly reduced the uncertainty in the results (R2 of 0.8 vs. 0.3) compared to the CRS 1000B model at CSP3. This research strongly supports the idea that an fb correction should be applied for cropland sites. It is also likely the same fb correction can be applied to forest sites, but a long-term study is still needed. This long-term study contributes valuable insights into the vegetation correction factor for CRNS, helping resolve a long-standing issue within the CRNS community.

Jake Harvey:
The Influence of Stalking Cover, Habitat Productivity, and Human Disturbance on Mountain Lion Resource Selection at Foraging Sites

Understanding the landscape features that facilitate successful predation by large carnivores has been limited because of the difficulty of accounting for variation in structural and functional characteristics within the broad vegetation classes typically included in resource selection models. This variation is particularly important for stalk and ambush predators occupying anthropogenic landscapes that rely on specific habitat features to kill prey because human landscape alteration may impact predation success. We quantified resource selection by 21 mountain lions (Puma concolor) at 492 black-tailed deer (Odocoileus hemionus columbianus) feeding sites along the urban edge in California’s San Francisco North Bay, USA. Mountain lions did not select higher primary productivity at feeding sites overall, but their selection of primary productivity increased as a function of increasing tree and shrub ground cover. This indicates that mountain lions prioritize structural habitat features that promote successfully killing prey, rather than productive areas that maximize encounters with prey. Density of cover influenced the probability of predation more strongly than the presence of forested areas alone and may also provide cover from human disturbance. Mountain lions did not strongly avoid buildings and fed on deer in close proximity to buildings (mean = 328m). Interestingly, mountain lions selected parcel boundaries lined with fencing at feeding sites, which could allow them to corner prey and highlight that humans can both negatively and positively influence mountain lion predation. Our results advance understanding of structural characteristics of natural and anthropogenic habitat features used by top predators to kill prey in fragmented, human-dominated landscapes.