Caution Is Needed in Quantifying Terrestrial Biomass Responses to Elevated Temperature: Meta-Analyses of Field-Based Experimental Warming Across China

Certainty over warming-induced biomass accumulation is essential for addressing climate change. However, no previous meta-analysis has investigated this accumulation across the whole of China; also unclear are the differences between herbaceous and woody species and across plant phylogeny, which are critical for corresponding re-vegetation. We extracted data from 90 field-based experiments to reveal general patterns and driving factors of biomass responses all over China. Based on traditional meta-analyses, a warmer temperature significantly increased above- (10.8%) and below-ground (14.2%) biomass accumulation. With increasing warming duration (Warm(D)) and plant clade age, both above-ground and below-ground biomass showed significant increases. However, for herbaceous versus woody plants, and the whole community versus its dominant species, responses were not always constant; the combined synergies would affect accumulative response patterns. When considering Warm(D) as a weight, decreases in total above-ground biomass response magnitude were presented, and the increase in below-ground biomass was no longer significant; notably, significant positive responses remained in tree species. However, if phylogenetic information was included in the calculations, all warming-induced plant biomass increases were not significant. Thus, it is still premature to speculate whether warming induces biomass increases in China; further long-term experiments are needed regarding phylogeny-based responses and interspecies relations, especially regarding woody plants and forests.