Quantifying drylands' drought resistance and recovery: the importance of drought intensity, dominant life history and grazing regime

Abstract

Projected global change will increase the level of land-use and environmental stressors such as drought and grazing, particularly in drylands. Still, combined effects of drought and grazing on plant production are poorly understood, thus hampering adequate projections and development of mitigation strategies. We used a large, cross-continental database consisting of 174 long-term datasets from >30 dryland regions to quantify ecosystem responses to drought and grazing with the ultimate goal to increase functional understanding in these responses. Two key aspects of ecosystem stability, resistance to and recovery after a drought, were evaluated based on standardized and normalized aboveground net primary production (ANPP) data. Drought intensity was quantified using the standardized precipitation index. We tested effects of drought intensity, grazing regime (grazed, ungrazed), biome (grassland, shrubland, savanna) or dominant life history (annual, perennial) of the herbaceous layer to assess the relative importance of these factors for ecosystem stability, and to identify predictable relationships between drought intensity and ecosystem resistance and recovery. We found that both components of ecosystem stability were better explained by dominant herbaceous life history than by biome. Increasing drought intensity (quasi-) linearly reduced ecosystem resistance. Even though annual and perennial systems showed the same response rate to increasing drought intensity, they differed in their general magnitude of resistance, with annual systems being ca. 27% less resistant. In contrast, systems with an herbaceous layer dominated by annuals had substantially higher postdrought recovery, particularly when grazed. Combined effects of drought and grazing were not merely additive but modulated by dominant life history of the herbaceous layer. To the best of our knowledge, our study established the first predictive, cross-continental model between drought intensity and drought-related relative losses in ANPP, and suggests that systems with an herbaceous layer dominated by annuals are more prone to ecosystem degradation under future global change regimes.

How to avoid unsustainable side effects of managing climate risk in drylands — The supplementary feeding controversy

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Estimation and uncertainty analyses of grassland biomass in Northern China: Comparison of multiple remote sensing data sources and modeling approaches

“…There are various studies focused on grassland biomass estimation on regional to global scale with different data and methods (Fan et al, 2007;Hsu et al, 2012;Jiang et al, 2014;Luo et al, 2002;Ni, 2002;Ruppert et al, 2015;Scurlock et al, 2002). Compared with field measurement, which is the most basic, direct and authentic method, remote sensing provides an efficient and nondestructive way for grassland biomass estimation especially for regional scale research (i.e.…”

Life stage influences the resistance and resilience of black mangrove forests to winter climate extremes

“…Potential ecosystem responses to climate extremes are diverse, ranging from abrupt state changes that produce major alterations in ecosystem structure and function to minor events with negligible ecological implications (Smith 2011). Research that improves our understanding of the resistance and resilience of ecosystems to climate extremes plays an especially important role in helping future-focused environmental managers better gauge and plan for potential climate change impacts (Lloret et al 2012, Hoover et al 2014, Ruppert et al 2015. In this study, we examine the life-stage dependent effects of winter climate extremes upon the resistance and resilience of an important coastal wetland foundation species.…”