Variations in foliar stable carbon isotopes among functional groups and along environmental gradients in China – a meta‐analysis

Variations in foliar stable carbon isotope signatures (δ¹³C) of different plant functional groups (PFGs) and their relationships with environmental factors in China were investigated in this meta‐analysis. There were some significant, but small differences in δ¹³C among PFGs categorised by life form (<1‰). Trees (?26.78‰) and shrubs (?26.89‰) had similar mean δ¹³C that were significantly higher than those of herbs (?27.49‰). Evergreen shrubs (?25.82‰) had significantly higher mean δ¹³C than deciduous shrubs (?26.92‰). Perennial herbs (?26.83‰) had significantly higher mean δ¹³C than annual herbs (?27.10‰). Grasses (?26.46‰) had significantly higher mean δ¹³C than forbs (?26.96‰). For pooled data, δ¹³C was significantly and negatively correlated with mean annual precipitation (MAP) and mean annual temperature (MAT), while it was significantly and positively correlated with latitude and altitude. There was a threshold value of MAP along the gradients, and δ¹³C did not change significantly with higher rainfall. The δ¹³C of PFGs changed with altitude, suggesting that increases in δ¹³C with altitude cannot be generalised. Differences in δ¹³C between PFGs were generally much <1‰ and therefore insignificant. In contrast, MAP and MAT had relatively large effects on δ¹³C (more than 4‰ between extremes). The δ¹³C of some PFGs responded to environmental gradients in the same manner, while their ‘rates’ of change were significantly different in some cases. This information could help predict potential changes in the distribution of PFGs in response to future climate change.