BayCEER Workshop 2019

Examining the mechanisms underlying mountain plant community responses to increased temperature: a translocation experiment

P 1.1 in Plant and soil responses to drought: Interdisciplinary approaches and views

Introduction

Climate change will lead to uncertainty for future biodiversity and productivity of montane grasslands. Increasing temperature may favor increased biomass when water is not limiting directly or indirectly by increasing soil activity. These changes in biomass allocation may also change interspecific competition of species within communities. We examined yearly changes in productivity and diversity in grasslands exposed to warmer climates following permanent downslope translocation of plant-soil monoliths.  We expected to see increasing temperature leading to i) increased aboveground biomass in sites where precipitation was similar to the home environment and ii) subsequent decreases in richness as competitive hierarchies shifted.

Material and Methods

 We addressed these hypotheses by translocating 126 plant-soil monoliths of three different montane grasslands in the German Alps to lower sites with elevational changes ranging from 300 m - 1000 m, in order to simulate possible future climate scenarios. In July 2019, a subset of mesocosms were destroyed in order to thoroughly measure soil variables to connect to observed plant community changes.

Results

In 2017, following one year of exposure, plant communities in warmer areas increased aboveground biomass increases as long as precipitation regime was not severely altered. Changes relative to controls ranged from 52% increase to a -23% decrease where precipitation also decreased. Species richness declined consistently with warming, ranging from 13% to 46% species loss. In 2018, a severe drought occurred in Central Europe, leading to experiment wide decreases in biomass and species richness.

Conclusions

We show at small spatial scales a loss of species in montane environments with future climate change, while changes in aboveground biomass were conditional on concurrent precipitation changes. Soon we will be able to more mechanistically show how these vegetation changes are linked to changes in soil processes.

Keywords: Global warming, mountain grasslands, plant-soil processes, community ecology