Lines reflect linear regressions of the effects of summer water availability (x axis, 30 year mean AET summer minus 30-year MAP summer) on the relationship between summer air temperature and NEE. Standardized slopes reflect the effect of 1 s.d. (z-score) of summer temperature on 1 s.d. of summer C flux. Positive x-axis values indicate sites where summer water use regularly exceeds precipitation inputs and near-surface soil water may be especially important. Points above the dashed zero line on the y axis represent sites where higher-than-average summer temperatures lead to higher-than-average NEE. Larger points indicate greater confidence in the slope for each site and reflect model weights. Error bands represent 95% confidence intervals.
