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Wednesday, April 11 • 2:00pm - 2:15pm
PROCESSES IN AGRICULTURAL LANDSCAPES: Amphibian Amblings Amid Arid-land Agriculture: Wetland Connectivity and Species Dispersal in the Great Plains Using Least-Cost Path and Landscape Resistance Modelling

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AUTHORS: Lucas J. Heintzman*, Nancy E. McIntyre – Texas Tech University

ABSTRACT: We examined impacts of land-use changes from 2008 to 2016 on functional connectivity among >80,000 wetlands (regionally called playas) of the south-central Great Plains. Playas are critical habitats for amphibians, and changes in surrounding agricultural practices in terms of crop type and irrigation are likely to influence amphibian dispersal across the playa network. We examined potential challenges to amphibian dispersal by determining least-cost paths (LCP) with landscape resistance modelling approaches that incorporated USGS MIrAD-US and USDA NASS CropScape land-cover data coupled with literature-based estimates of species-specific dispersal capabilities. To assess model sensitivity we developed three scenarios that varied in their assigned resistance values among land-cover classes, using Linkage Mapper and Circuitscape software extensions in ArcMap 10.4. We then used FRAGSTATS to calculate 12 metrics to compare dispersal path configurations across years and scenarios. LCPs varied spatially across the landscape, which resulted in topological differences in LCP length and cost-weighted distance allocations by scenario and year. Overall, LCPs occupied ~25% of the landscape, with a trend toward compaction of LCPs in more resistive scenarios. However, despite these differences our study indicated that the playa network as a whole was rather insensitive to assigning different resistance values because 81% of LCP locations overlapped with at least one other scenario, and 57% of LCP locations overlapped among all three scenarios. Our findings support previous graph-based assessments of playa structural connectivity that indicated high levels of path redundancy within the network. However, although LCPs showed extensive overlap among scenarios, the vast majority of these linkages were at distances well beyond the individual lifetime dispersal maxima for regional amphibians. Thus, functional connectivity is achieved in this landscape only by spanning scales from daily movements to inter-generational dispersal.

Wednesday April 11, 2018 2:00pm - 2:15pm CDT
Adams Room