Alpine plant communities are limited by nitrogen (N) because they have evolved in ecosystems with naturally low levels of reactive N. They have evolved adaptations such as fixed growth rates, slow but steady nutrient uptake and short growing seasons. Plants including conifers, grasses/sedges, and forest understory plants that use N more rapidly and have faster growth rates may outcompete unique alpine and subalpine species under increased N deposition.
Increased N deposition is projected to alter plant communities, soil processes, and soil carbon (C) and N storage. Anna Simpson, a PhD Candidate at University of Washington, is studying the effects of N on alpine ecosystems. Anna is identifying the critical load of N in alpine ecosystems. A critical load is defined as the threshold of deposition below which specified harmful ecological effects do not occur.