Code to support 'Contrasting age-dependent leaf adaptation and acclimation strategies driving vegetation greening across global deciduous broadleaved forests'

This repository contains the code used to perform the analyses described in the following paper: Wang, F., Xue, M., Ciais, P., Doughty, C., Zhou, L., Shang, J., Chen, L., Liu, J., Reich, P., Green, J., Hao, D., Tao, S., Su, D., Liu, L., Xia, J., Wang, H., Yu, K., Zhu, Z., Zhu, P., Li, X., Liu, H., Zeng, Y., Yan, K., Liu, L., Lafortezza, R., Su, Y., Pan, Y., Yang, X., He, J., Yuan, W., Fu, Y. & Chen, X.*, (2024). Contrasting age-dependent leaf adaptation and acclimation strategies driving vegetation greening across global deciduous broadleaved forests. Nature Plants. Submitted. Abstract: Global greening in deciduous broadleaved forests (DBFs) suggests two primary leaf adaptation and acclimation strategies of plants: an increase in maximal leaf area (LAImax) driven by elevated CO2 levels and an extended length of growing season (LOS) in response to climate warming. However, it remains unclear which of these response offers an optimal strategy for DBFs facing ongoing climate change. Here, we examined multiple satellite-based datasets and field measurements to explore temporal changes in LAImax (∆〖LAI〗_max) and LOS (∆LOS) across global DBFs from 2002 to 2021. Our analysis revealed a negative correlation between ∆〖LAI〗_max and ∆LOS, which were previously thought to change coordinatively. Notably, the trade-offs between ∆〖LAI〗_max and ∆LOS varied by stand age. Younger DBFs with fewer initial green leaves, predominantly in eastern Asia, were more responsive to CO2 fertilization and displayed an increase in LAImax with small changes in LOS. This acquisitive strategy facilitated younger DBFs to grow more but thinner, drier leaves, thereby enhancing the light-use efficiency. Conversely, older DBFs with abundant green foliage, primarily located in eastern North America and Europe, are more sensitive to climate warming; and markedly extended their LOS with increased leaf mass per area and moisture content. This relatively conservative strategy led older DBFs to produce denser and wetter, but less-photosynthetically efficient leaves, resulting in decreased light-use efficiency. Our findings provide valuable insights into the trade-off between changes in green leaf area and growing season length and their implications for ecosystem functioning.