Abstract
Plant functional traits underlie vegetation responses to environmental changes such as global warming, and consequently influence ecosystem processes. While most of the existing studies focus on the effect of warming only on species diversity and productivity, we further investigated (i) how the structure of community plant functional traits in temperate grasslands respond to experimental warming, and (ii) whether species and functional diversity contribute to a greater stability of grasslands, in terms of vegetation composition and productivity. Intact vegetation turves were extracted from temperate subalpine grassland (highland) in the Eastern Pyrenees and transplanted into a warm continental, experimental site in Lleida, in Western Catalonia (lowland). The impacts of simulated warming on plant production and diversity, functional trait structure, and vegetation compositional stability were assessed. We observed an increase in biomass and a reduction in species and functional diversity under short-term warming. The functional structure of the grassland communities changed significantly, in terms of functional diversity and community-weighted means (CWM) for several traits. Acquisitive and fast-growing species with higher SLA, early flowering, erect growth habit, and rhizomatous strategy became dominant in the lowland. Productivity was significantly positively related to species, and to a lower extent, functional diversity, but productivity and stability after warming were more dependent on trait composition (CWM) than on diversity. The turves with more acquisitive species before warming changed less in composition after warming. Results suggest that (i) the short-term warming can lead to the dominance of acquisitive fast growing species over conservative species, thus reducing species richness, and (ii) the functional traits structure in grassland communities had a greater influence on the productivity and stability of the community under short-term warming, compared to diversity effects. In summary, short-term climate warming can greatly alter vegetation functional structure and its relation to productivity.
Highlights
High mountain ecosystems are considered to be vulnerable to global warming [1,2]
Few weeks after the transplant, the community weighted mean (CWM) of SLA, start of first flowering and proportion of rhizomatous and prostrate species started to diverge from the lowland to the highland
We found that short-term climate warming can have a great impact on the functional structure of grassland communities, both in terms of community-weighted means (CWM) of traits (Fig 1; Table 1) and functional diversity (Fig 2; Table 1)
Summary
High mountain ecosystems are considered to be vulnerable to global warming [1,2]. The increase in biomass productivity has been attributed to the enhanced plant growth as a transient result of increased soil organic matter mineralization [12,13] and nutrient availability with warming [6,8]. These resource enriched environmental conditions are considered favorable to species characterized by fast growth and high returns on resources investment [14,15]. Either increase or reduce diversity depending on the relationship between productivity and diversity [18,19]
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