Effects of mountaintop removal mining and valley filling on the occupancy and abundance of stream salamanders

摘要

Human-induced land-use changes are among the primary causes of ecosystem degradation and biodiversity loss. Across central Appalachia (USA), mountaintop removal mining and valley filling (MTR/VF) is the prevailing form of land-use change and represents a stressor to stream ecosystems. Salamanders are the dominant vertebrate in Appalachian headwater streams. Thus, we addressed the question: Is salamander occupancy and conditional abundance reduced in streams impacted by MTR/VF? We conducted repeated counts of adult and larval salamanders within 10-m reaches in 11 valley-filled streams and 12 reference streams in south-eastern Kentucky. Relationships between occupancy, conditional abundance, and site type (MTR/VF vs. reference) were modelled using the hurdle model (Ecology, 94, 2013 and 1472), where occupancy is modelled separately from abundance while accounting for differences in per-individual detection probabilities among groups. We found mean occupancy probabilities were >085 for all groups in reference reaches, whereas mean occupancy probabilities were relatively lower in MTR/VF reaches (ranging from 023 to 066). Posterior means of the difference in occupancy between site types were negative across all groups, although MTR/VF stream reaches were at least 95% less likely to be occupied by spring salamander Gyrinophilus porphyriticus, adult southern two-lined salamander Eurycea cirrigera and larval dusky salamanders Desmognathus compared to reference reaches. Posterior means of the difference in conditional abundance between MTR/VF and reference stream reaches were negative across all groups; 95% credible interval for difference in conditional abundance covered zero for only one species (red salamander Pseudotriton ruber). After adjusting for goodness-of-fit, point estimates of differences in occupancy and conditional abundance still remained below zero for most species. Additionally, MTR/VF reaches had higher ion concentrations, total organic carbon and specific conductance compared to reference reaches.Synthesis and applications. Our study concludes that mountaintop removal mining and valley filling (MTR/VF) reduces salamander occupancy and conditional abundance. Although the potential mechanisms responsible for reduction are numerous, our findings suggest a change in the current regulatory framework is needed to offset the impacts of MTR/VF on stream ecosystems and biota. Reclamation techniques that enhance conditions for vegetative succession within catchments may improve habitat on reclaimed surface mines.