Optimal Allocation Strategies of Plant Calcium on Qinghai–Tibetan Plateau

Abstract Calcium (Ca) is an essential nutrient for plant growth and development. As Ca plays crucial roles in plant structure and signaling, its allocation strategies among organs can reflect the optimization of plant functions and responses to the environment. However, the allocation strategies and spatial variation of plant Ca at the community level have not been systematically determined on a large scale despite their potential link to ecosystem functions. Here, we mapped community‐level Ca content and density (1 × 1 km) using grid‐investigated data on leaves, branches, trunks, and roots from 680 sampling sites on the Qinghai–Tibetan Plateau (TP). Specifically, the Ca content and density of the leaves, branches, trunks, and roots of TP plants were 10.90, 6.09, 1.85, and 15.62 mg g −1 and 3.29, 17.10, 12.27, and 12.06 g m −2 , respectively. Importantly, plant adopted optimal allocation strategies with allocating more Ca to roots in stressed ecosystems to maintain survival while more Ca to leaves in suitable forests for growth, that is the proposed survival/growth‐driven allocation hypothesis. Furthermore, plants optimally absorbed more nutrients in stressed environments for defense, as demonstrated by the higher Ca content and lower Ca use efficiency in deserts and grasslands than in forests. Furthermore, the strong evidence for the proposed hypothesis was the spatial pattern of plant Ca content decreasing from the northwest to the southeast. Our findings reveal the optimal nutrient allocation strategies and provide data support (Ca content and density) for assessing plant nutrient status in different types of ecosystems.