Climate extremes initiate ecosystem‐regulating functions while maintaining productivity

Abstract

Summary1. Studying the effects of climate or weather extremes such as drought and heat waves on biodiversity and ecosystem functions is one of the most important facets of climate change research. In particular, primary production is amounting to the common currency in field experiments world-wide. Rarely, however, are multiple ecosystem functions measured in a single study in order to address general patterns across different categories of responses and to analyse effects of climate extremes on various ecosystem functions. 2. We set up a long-term field experiment, where we applied recurrent severe drought events annually for five consecutive years to constructed grassland communities in central Europe. The 32 response parameters studied were closely related to ecosystem functions such as primary production, nutrient cycling, carbon fixation, water regulation and community stability. 3. Surprisingly, in the face of severe drought, above-and below-ground primary production of plants remained stable across all years of the drought manipulation.4. Yet, severe drought significantly reduced below-ground performance of microbes in soil indicated by reduced soil respiration, microbial biomass and cellulose decomposition rates as well as mycorrhization rates. Furthermore, drought reduced leaf water potential, leaf gas exchange and leaf protein content, while increasing maximum uptake capacity, leaf carbon isotope signature and leaf carbohydrate content. With regard to community stability, drought induced complementary plantplant interactions and shifts in flower phenology, and decreased invasibility of plant communities and primary consumer abundance. 5. Synthesis. Our results provide the first field-based experimental evidence that climate extremes initiate plant physiological processes, which may serve to regulate ecosystem productivity. Journal of Ecology 2011Ecology , 99, 689-702 doi: 10.1111Ecology /j.1365Ecology -2745Ecology .2011 of synergisms or decoupling of biogeochemical processes, and of fundamental response dynamics to drought at the ecosystem level including potential tipping points and thresholds of regime shift. Future work is needed to elucidate the role of biodiversity and of biotic interactions in modulating ecosystem response to climate extremes.

Integrating plant ecological responses to climate extremes from individual to ecosystem levels

“…As alluded to earlier, stability in ecosystem productivity may also be driven by reduced stability at lower ecological levels, such as with species population dynamics [46,47]. Thus, the high variability that is evident at the individual or population level may provide a pathway to stabilize community composition [86] or ecosystem productivity [14] with respect to increases in climatic extremity and variability.…”

“…Although functional resistance to climate extremes is often low, rapid recovery and thus stability in ecosystem function is evident across systems ( [4,82], but see [25]). The paucity in large compositional or functional changes appears to be often driven, in part, by context-dependent community-level processes that act to stabilize plant community structure and/or function in response to, or recovery from climate extremes [4,14,94]. The composition of interacting plant species within a community can greatly modify the response of both individual organisms and ecosystem productivity to a climate extreme [49,[95][96][97][98].…”

“…Studies that employ multi-scale approaches are valuable in demonstrating the importance of a holistic understanding of ecosystem responses to changing climatic variability [128] and extremity [4,14,129]. The magnitude of response to a climate extreme will likely vary with the ecological level of organization (e.g.…”

“…These notions apply equally to ecosystem responses to climate extremes. For example, high sensitivity or alterations at fine scales, such as in plant physiology, can underlie and buffer impacts to broad scale processes, such as in net primary production [4,14]. Therefore, an understanding of the cross-scale interactions between different levels of ecological organization (e.g.…”

A study of soil-dynamics based on a simulated drought in an alpine meadow on the Tibetan Plateau

“…Some studies have revealed the stability of soil processes underground in a drought experiment, semiarid soil microbiological parameters including microbial biomass and extracellular enzyme activities showing a sufficient resistance and a rapid recovery after soil rewetting (Hueso et al 2011). So far, most studies that simulated drought events have been done in semiarid and Mediterranean region (De Boeck et al 2011;Godfree et al 2011;Jentsch et al 2011;Jimenez et al 2011;Penuelas et al 2007;Rich et al 2008), but not on the Tibetan Plateau , where the unique geography yields relatively high vegetation growth with concentrated rainfall during the growing season, but overall very slow soil organic matter decomposition rates during dry cold winters (Kato et al 2006;Zhao et al 2006).…”