Epsilon Archive for Student Projects

Abstract

As global temperatures rise, arctic and subarctic ecosystems are particularly affected and respond with altered soil nutrient dynamics and plant productivity as well as changes in community compositions of organisms and plant-soil interactions. Although many studies have reported temperature-induced changes in subarctic ecosystems, it remains unclear whether these responses are linear, nonlinear, or reach thresholds at larger temperature gradients. Similarly, little is known about the role of soil microfauna in the responses of plant-soil interactions to increasing temperatures.
This thesis focuses on plant functional trait responses of a subarctic meadow community to temperature increases of up to +9°C, as well as the influence of microfauna on these warming systems. The functional trait responses were studied using a growth chamber experiment with five temperature settings and two inoculum treatments (with/without microfauna). The plants and soil samples were obtained from the study site in Abisko, Sweden, which also served as the basis for the design of the model community. After one growing season, plant above- and belowground functional traits as well as soil abiotic properties were measured and analysed.
Warming increased both above- and belowground biomass and significantly affected most plant traits. Despite the general increase in biomass, the allocation shifted with temperature, with proportionally more resources being invested into roots at temperatures between +4.6 and +6.9°C above ambient temperature. At the highest temperature the plants allocated more into shoots, likely due to a higher competition for light. The plant traits specific root length as well as leaf and root dry matter content showed more conservative functions at higher temperatures which can be related to nutrient limitation due to increased plant productivity and competition. In contrast, plants developed more acquisitive leaf traits in the presence of microfauna, indicating a higher nutrient availability due to, among others, improved nutrient cycling and pathogen regulation.
These results show that subarctic plant communities do not respond linearly to warming, but may experience threshold-like changes in trait responses and resource allocation. Increased temperatures will strongly influence community composition, nutrient cycling and productivity in subarctic ecosystems. Further research is needed to better understand the interactions within the ecosystem as well as future developments, and should focus on long-term studies, the analysis of nutrient pools in soils and plants, and the threshold dynamics of plant responses to the changing environment.