| Autor: |
Lee SR; U. S. Geological Survey, Western Ecological Research Center, Yosemite Field Station, Oakhurst, California, United States of America., Berlow EL; Vibrant Data Labs, San Francisco, California, United States of America., Ostoja SM; U. S. D. A. California Climate Hub, Agricultural Research Service, John Muir Institute of the Environment, University of California Davis, Davis, California, United States of America., Brooks ML; U. S. Geological Survey, Western Ecological Research Center, Yosemite Field Station, Oakhurst, California, United States of America., Génin A; Institut des Sciences de l'Evolution, CNRS, Université de Montpellier II, Montpellier, France., Matchett JR; U. S. Geological Survey, Western Ecological Research Center, Yosemite Field Station, Oakhurst, California, United States of America., Hart SC; Life and Environmental Sciences and Sierra Nevada Research Institute, University of California, Merced, California, United States of America. |
| Abstrakt: |
We evaluated the influence of pack stock (i.e., horse and mule) use on meadow plant communities in Sequoia and Yosemite National Parks in the Sierra Nevada of California. Meadows were sampled to account for inherent variability across multiple scales by: 1) controlling for among-meadow variability by using remotely sensed hydro-climatic and geospatial data to pair stock use meadows with similar non-stock (reference) sites, 2) accounting for within-meadow variation in the local hydrology using in-situ soil moisture readings, and 3) incorporating variation in stock use intensity by sampling across the entire available gradient of pack stock use. Increased cover of bare ground was detected only within "dry" meadow areas at the two most heavily used pack stock meadows (maximum animals per night per hectare). There was no difference in plant community composition for any level of soil moisture or pack stock use. Increased local-scale spatial variability in plant community composition (species dispersion) was detected in "wet" meadow areas at the two most heavily used meadows. These results suggest that at the meadow scale, plant communities are generally resistant to the contemporary levels of recreational pack stock use. However, finer-scale within-meadow responses such as increased bare ground or spatial variability in the plant community can be a function of local-scale hydrological conditions. Wilderness managers can improve monitoring of disturbance in Sierra Nevada meadows by adopting multiple plant community indices while simultaneously considering local moisture regimes. |
