Temporal contribution of the predictor variables. The model (Supplementary Information, section 2.1.4) suggested that increasing CO2 is the main contributor to the observed increases in LAI. The difference between the modelled contributions and the observed trends has been considered as an unknown contribution to the temporal variation LAI. The temporal variations of the predictors are shown in square brackets. Error bars indicate standard errors. Units are ppm for CO2, kg ha−1 yr−1 for S and N deposition, °C for temperature and standard deviations for SPEI. Error bars indicate standard errors. See Methods for information about the methodology used to calculate the contributions. Significance levels: (*)
P < 0.1; *P < 0.05; **P < 0.01; ***P < 0.001.