2021/08/23 by Eskander, Mena, Hughes, Gavin, Michel, Roberto +1
#Cushion plants #climatic stress #edaphic stress #facilitation #stress-gradient hypothesis
paper · doi:10.21973/n3v952
The stress-gradient hypothesis is an ecological theory which aims to describe patterns of species interaction under conditions of adversity. High-elevation montane environments are among the most stressful habitats for plants; organisms found in these regions are well-adapted to a variety of environmental stressors, and their interactions range from competitive to facilitative across stress gradients. We examined the effects of edaphic and climatic stressors on facilitation in subalpine cushion-forming plants in the White Mountains of California, a semi-arid mountain range. Greater association between these cushion plants and neighboring plant species was observed on more nutrient-rich granitic soils, and no trend was observed across north and south aspects. Nitrogen-fixing species of cushion plants contained more associated plants than non-nitrogen-fixers, and all cushions demonstrated an ability to thermoregulate when compared to their surroundings. While these potential mechanisms for facilitation were not observed as expected across stress gradients, these effects may have been masked by the severity of the macroclimate in the White Mountains; facilitation in subalpine cushion plants remains an important potential ecosystem service, and their conservation may therefore become a higher priority in the face of climate change, habitat loss, and species migration.