Assessing community and ecosystem sensitivity to climate change – toward a more comparative approach

Abstract

Plant communities can vary widely in their sensitivity to changing precipitation regimes, as reported by Byrne et al., Mulhouse et al. and Sternberg et al. in this issue of Journal of Vegetation Science. But to understand why communities differ in their sensitivity, we argue that clearly defined metrics of sensitivity and coordinated research approaches are needed to elucidate mechanisms.One of the most daunting tasks facing ecologists is the need to increase understanding of how ecological systems will respond to a changing climate. At present, we know a great deal about how climate has changed in the past, and forecasts for future change carry a high degree of confidence (IPCC 2013). However, forecasting ecological responses to these climate changes remains a challenge, in part because of differences in the sensitivity of ecological processes and systems to changing temperature and precipitation regimes (Smith et al. 2009;Dillon et al. 2010). Indeed, our understanding of how ecological systems, particularly communities and ecosystems, vary in their sensitivity to climate change and the mechanisms underlying such differential sensitivity lags far behind our ability to forecast climatic changes.In this issue, three papers report results of research designed to increase our understanding of the sensitivity of arid and semi-arid plant communities to changing precipitation regimes. The papers use very different approaches -ranging from long-term observations to short-term experiments -to address this issue. Mulhouse et al. (2017) use long-term monitoring of plant communities to assess community dynamics in response to precipitation patterns. Sternberg et al. (2017) evaluate results from long-term grazing experiments within the context of variability in precipitation to determine how inter-annual precipitation legacy effects may influence plant diversity and biomass production. Finally, Byrne et al. (2017) directly manipulated precipitation amount in a short-term, multisite experiment to examine plant community responses and sensitivity. Despite differences in approach, these three studies are linked by their conclusions that plant communities in some ecosystems are likely to be relatively insensitive to expected changes in precipitation, whereas others may be highly sensitive and respond dramatically to precipitation change.While the results of these studies -that communities are expected to differ in their sensitivity to forecast changes in precipitation -are interesting, in aggregate they are limited by the binary (resistant vs responsive) and qualitative (more vs less sensitive) nature of their conclusions. This highlights the need to quantify 'sensitivity' as (1) a continuous variable and (2) in ways that more readily allow comparisons across studies if we are to advance our understanding of how and to what extent communities and ecosystems will respond to future climate change. A 'systems' definition of sensitivity (change in output per unit change in input) may be most appropriate for ecology. Such a...

Critical transitions in rainfall manipulation experiments on grasslands

“…In rainfall manipulation experiments conducted to date, resilience has often been assessed by measuring how close the system is from its initial state (Ingrisch & Bahn, 2018;Kéfi et al, 2019;Smith, Wilcox, Power, Tissue, & Knapp, 2017). This is usually done by comparing ANPP values obtained before drought (ANPP1), immediately after drought cessation (ANPP2) and after the recovery period (ANPP3; Figure 5a,b; Matos et al, 2019).…”

Shifts in the dynamics of productivity signal ecosystem state transitions at the biome‐scale

“…; Smith et al . ). For example IAV of productivity has been studied at regional and global scales to quantify ecosystem responses to climatic variability (Knapp et al .…”

Semi‐arid savanna herbaceous production and diversity responses to interactive effects of drought, nitrogen deposition, and fire

“…This novel pattern resulted in slightly above‐average annual precipitation in 2018 (586.49 mm) and likely affected our observed results. However, these results are presented as an aspect of a larger interaction that merits further investigation (Smith, Wilcox, Power, Tissue, & Knapp, ). In the spring of 2019, the mean cover by annual plants was 61% compared with 11% in the winter of 2018.…”