Abstract ID: 3.11650 | Accepted as Talk | Talk/Oral | TBA | TBA

Experiments that manipulate global change factors in situ are useful for studying realistic responses to future climate scenarios. While single factor studies investigating warming or drought are common, factorial experiments of warming and drought are comparatively rare and often yield varying results. Furthermore, these factors may interact in ways that are not obvious simply from the sum of their parts (additive or synergistic/antagonistic interactions). Grasslands account for a significant proportion of the world’s terrestrial ecosystems and act as a major sink of carbon. Both uptake of carbon (accumulation of biomass through photosynthesis) and emission (soil respiration) from grassland ecosystems are, in large part, governed by temperature and moisture. Thus, changes in climate are likely to have profound implications for grassland carbon dynamics. Here, we performed a systematic review and meta-analysis that aimed to synthesise the data from 34 in situ field manipulative studies that investigated the effects of warming and drought factorially, in grassland ecosystems across the globe. Our results suggest that drought as a main effect causes significant reductions in soil respiration, above ground biomass, and below ground biomass, while warming alone does not. Drought in combination with warming appears to have more significant impacts at higher elevations (> 1000 m) than lower elevations (< 1000 m). There were, however, no significant interactive effects of warming and drought on biomass or respiration; that is, the effect of warming is additive with drought. There was evidence of high levels of heterogeneity in soil respiration and despite copious research on warming and drought as individual factors, there are far fewer multi-factor types of studies worldwide, particularly in continents outside of Asia, Europe, and North America. Overall, our findings emphasise the importance of drought effects when considering the impacts of future climate conditions, as drought appears to be more impactful than warming, though at higher elevations, drought in combination with warming is of more importance.