Rain Exclusion Sensitivity in High Altitude Plants and Ecosystems: Upscaling Perspectives
Climate change is having a strong impact on Arctic and alpine tundra ecosystems. Although warming has been extensively studied in these environments, there has been little research into the effects of precipitation regime shifts, triggering extreme drought events (EDEs) on cold ecosystems. Field experiments have often investigated the impact of changes in the amount of precipitation, while neglecting the consequences of magnitude and distribution of precipitation events over time. In particular, the timing of dry spells is regarded as a crucial driver of ecosystems responses, such as net primary production (NPP) and CO2 fluxes; for example, herbaceous ecosystems have been found to be more negatively affected by early summer drought respect to dry spells occurring in mid and late season. Ecosystem changes represent the final response of a community, which is chiefly shaped by the multiple eco-physiological and growth responses of species in relation to the amount of water available. Linking species' responses to ecosystem functions is an intriguing ecological challenge, which can be faced by a functional trait-based approach. However, the high variability at population level, due individual phenotypic plasticity, could lead to inconsistencies when individual or population responses are applied to community- or ecosystem-level processes. Upscaling the response of plant communities to ecosystem and landscape level is pivotal to depict future scenarios of alpine vegetation, constituting baseline for the understanding of plausible mitigation actions. Remote sensing tools (e.g., satellite and UAV images) have been proved to be powerful tools to extend the response of local communities to higher ecological scales for gross ecosystem traits (e.g., NPP), but the mechanistic responses of plants (e.g. growth traits, physiological response) remain unexplored and promising.
The current project aims to detect ecosystem-level responses to EDEs, occurring at different times during the growing season, on plant species in two main alpine grassland communities occurring above the timberline. It will follow an upscaling approach from species to community- and ecosystem-level, in order to better understand the detailed mechanisms underlying general observations on ecosystem processes. The project will rely on field experimental manipulations, coupled with a functional trait-based approach. The main aims of the project are: 1) to identify the effects of EDEs on plant performance, considering cross-scale interactions ranging from species’ physiological responses to those at ecosystem level; 2) to identify ecological thresholds beyond which species’ performance and community stability may be impacted; 3) to quantify the resistance and resilience of plant species and ecosystem functions to different timings of summer drought episodes; and 4) to scale up the experiment results in the Alps by using remote sensing tools.