PARENT SESSION
Wednesday, August 9, 8:00-11:30 am
COS 48 - Biodiversity IV: grasslands, soil communities, and tools
Ballroom E, Ballroom Level, Cook Convention Center
Presiders: H Reynolds
Compensatory responses to loss of warming-sensitive plant species in a montane meadow ecosystem.
Smith Cross, Molly*,1, Harte, John1, 1 University of California, Berkeley, Berkeley, CA
ABSTRACT- Climate warming-induced plant species loss is likely to be non-random and based on species-specific susceptibility to changing climate conditions. We examined the ecological consequences of losing shallow-rooted forbs, a group of species we predict to be adversely affected by climate change based on their response to experimental warming. After three years of experimental species removal, tap-rooted forbs and grasses were able to compensate for the loss of shallow-rooted forbs with increased growth. Moreover, the removal of shallow-rooted forbs yielded a larger positive biomass response to nitrogen addition, possibly because removal led to increased soil moisture. The removal of shallow-rooted forbs had no effect on plant nitrogen uptake, shallow soil [NO3-] and [NH4+], and net nitrogen mineralization and nitrification rates. The removal of shallow-rooted forbs increased the amount of [NO3-] extracted from ion exchange resin bags at 30 cm depth, but we cannot distinguish between the effects of losing species vs. losing biomass on the movement of NO3- down through the soil profile. We conclude that although shallow-rooted forbs all responded negatively to warming, their loss did not have a significantly negative impact on biomass production and nitrogen cycling over the short duration of this study. However, our experiment suggests that the future loss of shallow-rooted forbs could result in an increased sensitivity to perturbations. While our study does not encompass a full gradient of species and functional group richness, it is interesting to note that our results do not follow the general pattern of decreased productivity, decreased nitrogen retention and a dampened response to nitrogen addition with species loss that is observed in many randomly-assembled gradient experiments. Further examinations of non-random species loss in other ecosystems are needed to improve our understanding of the consequences of human-driven declines in diversity.
Key words: plant diversity, montane meadow, ecosystem ecology