Spatial variation of sulfur in terrestrial ecosystems in China: Content, density, and storage

Sulfur (S) is an important macronutrient that is widely distributed in nature. Understanding the patterns and mechanisms of S dynamics is of great significance for accurately predicting the geophysical and chemical cycles of S and formulating policies for S emission and management. We systematically investigated and integrated 17,618 natural plots in China's terrestrial ecosystems and built a S density database of vegetation (including leaves, branches, stems, and roots) and surface soil (0-30 cm depth). The biogeographic patterns and environmental drivers of the S content, density, and storage in the vegetation and soil of terrestrial ecosystems were explored. Vegetation and soil were the major components of terrestrial ecosystems, storing a total of 2228.77 ± 121.72 Tg S, with mean S densities of 4.32 ± 0.04 × 10^-2, and 267.93 ± 14.94 × 10^-2 t hm^-2, respectively. The forest was the most important vegetation S pool and their S storage accounted for about 55.28 % of the total vegetation S storage, whereas soil S pools of croplands and other vegetation types (e.g., deserts and wetlands) accounted for about 63.18 % of the total soil S storage. The mean S density (2.18 ± 0.02 × 10^-2 t hm^-2) and S storage (12.45 ± 0.31 Tg) of plant roots were significantly higher than those of other organs. The spatial variation in the S density was mainly regulated by climate and soil properties, reflecting the physiological adaptation mechanisms of plants by adjusting the S uptake and distribution to cope with climate change. In this study, the spatial patterns of S density and storage in vegetation and soil in terrestrial ecosystems of China and their response to environmental factors on a national scale were systematically studied. The results provide insights into the biological functions of S and its role in plant-environment interactions.