Title：
Global patterns of C3/C4 grass biomass allocation: how aridity mediates nitrogen-induced divergent strategies
Authors：
Corresponding
Author：
Man Hu, Yujuan Zheng, Hang Shi, Rui He, Jie Gao*, Quanfa Zhang, Haishan Dang*
Pubyear：
2026
Title of
Journal：
New Phytologist
Paper
Code：
Volume：
251
Number：
Page：
2446-2458
Others：
Classification：
Source：
Abstract：
Plant biomass allocation is dynamically shaped by drought and nitrogen (N) availability, yet how aridity modulates N effects and whether this interplay is conserved across major photosynthetic pathways (C3 vs C4) remain mechanistically unresolved. Using a global dataset of 2747 root-to-shoot ratio (RSR) observations from 631 herbaceous species, we applied a multi-model framework (Random Forest, linear mixed-effects models, and Bayesian structural equation modeling) to investigate: how aridity modulates the effect of soil N on the root-to-shoot ratio (RSR); and whether this modulatory effect differs between C3 and C4 plants. Increasing aridity promoted a convergent rise in RSR in both C3 and C4 grasses. However, soil N directly increased RSR in C3 plants, but it enhanced net primary productivity in C4 plants, which indirectly reduced RSR. This decoupling between drought-response mechanisms and N-acquisition strategies reveals that while the two functional types followed a shared hydraulic rule, they adhere to distinct N economies. Our results reveal that increased soil N availability will trigger divergent carbon storage responses in C3 and C4 grasslands, potentially exacerbating this functional divergence as atmospheric N deposition continues to rise.
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