Interannual and spatial variability of net ecosystem production in forests explained by an integrated physiological indicator in summer oleh Ying Liu, Chaoyang Wu, Lin Liu, Chengyan Gu, T. Andrew Black, Rachhpal S. Jassal, Lukas Hörtnagl, Leonardo Montagnani, Fernando Moyano, Andrej Varlagin, M. Altaf Arain, Ajit Govind