Figure 4.

Path analysis effect of climatic variables on GPP during the summer of 2018 (a) and 2016 (b) across all of sites under δSWC ≤ −10% (i.e. Group 1) except the wetland site. Direct, indirect and total effects of Ta, VPD, SWC and PPFD on GPP from path analysis and the paths for driving GPP in 2018 (c) and 2016 (d). Red and blue arrows represent the positive and negative effects in a fitted structural equation model, respectively. The widths of the arrows indicate the strength of the causal relationship. Percentages (R²) underneath GPP values indicate the variance explained by climatic factors during the summer. The standardized total effect of each climate factor on GPP is equal to the sum of direct and indirect effects (n.s., not significant). (Online version in colour.)