Kyle Bradford, MS, is a 2023 graduate of the MS Program in Environmental Studies at Antioch University New England
- Michael Akresh, PhD, Committee Chair
- Aaron Ellison, PhD, Committee Member
Heathlands and pitch pine-scrub oak (PPSO) barrens are globally-imperiled natural communities threatened by human development and disruption of natural disturbance regimes. To restore these habitats in the northeastern United States, many sites are managed by mechanical tree harvesting, mowing, selective herbicide, and prescribed fire. Restored PPSO barrens and heathlands are important habitat for rare and threatened biota; barrens habitat has been shown to support high ant diversity including rare and threatened species. Ants are important providers of ecosystem services and functions, yet their ecology and response to management in inland Massachusetts barrens are not well known. I used hand-sampling to collect ants and count nests in 82 plots from 18 barrens and heathlands, on rocky and sandy-soil sites mostly in inland Massachusetts. In total, I identified 64 species in 22 genera from 3,908 individuals. I used linear mixed models to analyze how ant nest abundance, richness, and Shannon’s Diversity Index responded to restoration treatments and environmental variables such as vegetation structure and amount of deadwood (coarse woody debris [CWD] and stumps). Treatment group (1-2 years since first treatment [YSFT], 3-6 YSFT, >9 YSFT, power line corridor, sandy soil no treatment, rocky soil no treatment), was an important predictor for all three response variables. Treatment group influenced ant abundance, richness, and diversity differently, but across all three variables, newly treated sites (1-2 years since initial tree harvesting) had the lowest numbers of ant nests, richness, and diversity. Increased understory vegetation structure had significant positive relationships with nest abundance and richness. Amount of deadwood had significantly negative relationships with richness, diversity, and nest abundance (although deadwood was highly correlated with YSFT), and more decayed CWD had positive effects on nest abundance. I also used Non-metric Multidimensional Scaling (NMDS) to assess differences in ant communities among treatment groups. Ant communities differed among the treatment/habitats, and power line corridors had the most unique ant community. I collected six regionally rare and/or barrens specialist species, with four of these found on power line corridors and two on rocky-ridge barrens. My results provide evidence that heterogeneous habitat in barrens, including closed-canopy forest and a variety of early successional habitat, supports high ant diversity (e.g., 54 species currently known from Montague Plains WMA, which is 48% of the total known Massachusetts ant fauna). My results suggest that shrublands (higher understory vegetation structure and density) at barrens sites supports the highest ant richness. However, power line corridors were most important for rare and/or barrens-specialist species. More frequent management on power line corridors (e.g., every 4-5 years) and the use of herbicide may create unique habitat (more forbs/ferns, patchy, low vegetation) compared to silvicultural tree harvests and mowing. Time since initial tree harvesting (generally much longer in power line corridors) is likely a contributing factor to rare, and specialist species occupancy. Landscape context, including connectedness to high-quality habitat to facilitate dispersal, and management type are also likely contributing factors. Overall, my work can help managers understand how to best sustain high ant richness and rare species in these managed habitats and contributes continued evidence that these habitats are important for ant conservation in the region.
Bradford, K. (2023). Effects of Management and Environmental Variables on Ant Richness, Diversity, and Nest Abundance in Pitch Pine-Scrub Oak Barrens, Heathlands, and Dry Rocky-ridge Communities in Inland Massachusetts, USA. https://aura.antioch.edu/etds/992