Intraspecific trait variability mediates the response of subalpine grassland communities to extreme drought events

Abstract

Summary1. Climate change is expected to increase the magnitude and the frequency of extreme climatic events such as droughts. Better understanding how plant communities will respond to these droughts is a major challenge. We expect the response to be a shift in functional trait values resulting from both species turnover and intraspecific trait variability, but little research has addressed the relative contribution of both components. 2. We analysed the short-term functional response of subalpine grassland communities to a simulated drought by focusing on four leaf traits (LDMC: leaf dry matter content, SLA: specific leaf area, LNC: leaf nitrogen concentration and LCC: leaf carbon concentration). After evaluating species turnover and intraspecific variability separately, we determined their relative contribution in the community functional response to drought, reflected by changes in community-weighted mean traits. 3. We found significant species turnover and intraspecific variability, as well as significant changes in community-weighted mean for most of the traits. The relative contribution of intraspecific variability to the changes in community mean traits was more important (42-99%) than the relative contribution of species turnover (1-58%). Intraspecific variability either amplified (for LDMC, SLA and LCC) or dampened (for LNC) the community functional response mediated by species turnover. We demonstrated that the small contribution of species turnover to the changes in community mean LDMC and LCC was explained by a lack of covariation between species turnover and interspecific trait differences. 4. Synthesis. These results highlight the need for a better consideration of intraspecific variability to understand and predict the effect of climate change on plant communities. While both species turnover and intraspecific variability can be expected following an extreme drought, we report new evidence that intraspecific variability can be a more important driver of the short-term functional response of plant communities.

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

“…High intraspecific variability may be influenced by ecotypic and genetic variation within a species ( [37,52,53], but see [54]). High intraspecific trait variation has thus been posited to contribute to post-extreme shifts in community-weighted trait means irrespective of gains or losses of species from the community [55]. As a consequence, the impacts to individuals may not necessarily provide a single pathway for detecting impacts to population dynamics [33], and thus changes in community composition resulting from a climate extreme.…”

Trait-based plant ecology: moving towards a unifying species coexistence theory

“…Volf et al (2016) evaluated these two components as a response to disturbances of different intensity in meadows. Shifting environmental conditions lead to either changing species-presence/absence dichotomy-or modulating traits by adjusting, in turn, the relative abundance of some species, which is key to understanding how communities can respond to ongoing environmental change (Jung et al 2014). An important source of intraspecific trait variability that can significantly contribute to this balance is phenotypic plasticity (Valladares et al 2014).…”

Drought-induced shifts in plants traits, yields and nutritive value under realistic grazing and mowing managements in a mountain grassland

“…Plant functional traits can be simple measurements that depict the stature, the leaf economics spectrum or the root properties of plants (Violle et al, 2007), directly linked to the functions of plant growth, development and resource acquisition (Weiher et al, 1999;Wright et al, 2004). Variations in key plant traits such as specific leaf area (SLA) and leaf nitrogen concentration (LNC), linked to water conservation functions during photosynthesis , have been documented in response to water stress (Jung et al, 2014). At the community scale, trait values are averaged across all species and weighted by species abundance (e.g.…”

“…Variations in community plant traits in response to drought can therefore be due to both modification of species composition and intraspecific variability in traits, i.e. plasticity in plant morphology and physiology (Jung et al, 2014;Lepš et al, 2011). Drought-induced shifts in species composition are however likely to occur on a long-time scale, with potential lasting effect on the community properties, whereas intraspecific trait variations can occur rapidly but with potential effects of short (e.g.…”

“…Drought-induced shifts in species composition are however likely to occur on a long-time scale, with potential lasting effect on the community properties, whereas intraspecific trait variations can occur rapidly but with potential effects of short (e.g. seasonal) duration (Jung et al, 2014;Lloret et al, 2012;Suding et al, 2008). Such changes in community plant traits can ultimately influence agronomic services such as forage yields and its nutritive value (Gardarin et al, 2014;Quétier et al, 2007).…”