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.

中文翻译：

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青藏高原植物钙的优化配置策略

钙（Ca）是植物生长发育必需的营养素。由于Ca在植物结构和信号传导中发挥着至关重要的作用，其在器官之间的分配策略可以反映植物功能的优化和对环境的响应。然而，尽管植物钙与生态系统功能存在潜在联系，但群落水平上植物钙的分配策略和空间变化尚未在大范围内得到系统确定。在这里，我们利用青藏高原 (TP) 680 个采样点的叶子、树枝、树干和根的网格调查数据绘制了群落水平的钙含量和密度 (1 × 1 km)。具体而言，TP植物的叶、枝、树干和根的Ca含量和密度分别为10.90、6.09、1.85和15.62 mg g ^-1和3.29、17.10、12.27和12.06 g m ^-2。重要的是，植物采取了最优分配策略，将更多的Ca分配给受压生态系统中的根部以维持生存，同时将更多的Ca分配给适合森林中的叶子以促进生长，这就是提出的生存/生长驱动分配假设。此外，沙漠和草原的钙含量高于森林，但钙的利用效率较低，这表明植物在应激环境下可以吸收更多的养分进行防御。此外，所提出的假设的有力证据是植物钙含量从西北到东南递减的空间格局。我们的研究结果揭示了最佳养分分配策略，并为评估不同类型生态系统中的植物养分状况提供数据支持（钙含量和密度）。