Nitrogen storage and allocation in China’s forest ecosystems

Abstract

Forests are important parts of terrestrial ecosystems and play a leading role in regional and global nitrogen (N) cycles. Detailed assessment of N storage and allocation in China’s forests is critical to improve the accuracy of regional or global N estimates and to guide policy-makers in the formulation of scientific and effective N management measures. However, the fore st N storage at national scale remains unclear. Based on 4420 forest field-investigated data, we investigated the N storage allocation in China’s forests, explored the spatial patterns and influence factors. The data included vegetation information on various organs (i.e., leaf, branch, stem, and root) and soil information at different depths (0−30 cm and 0−100 cm). The total N storage in China’s forest ecosystems was 14.45±8.42 t N hm–2; 0.86±0.51 t N hm–2 (5.95%) in vegetation and 13.59±8.40 t N hm–2 (94.05%) in soil (0–100 cm). The storage and allocation of N varied significantly across various regions and forest types. For different ecological regions, N storage varied from 10.34 to 23.11 t N hm–2, and the allocation ratio of N storage between vegetation and soil (0–100 cm) varied from 0.03 to 0.16. For different forest types, the N storage varied from 12.87 to 18.32 t N hm–2, and the allocation ratio of N storage between vegetation and soil (0–100 cm) varied from 0.03 to0.09. The spatial patterns relative to N storage and allocation in forests were different. Climate was the primary factor influencing the spatial variation in fore st N storage, while soil texture was the main factor influencing the spatial variation in N allocation. These first estimates of N storage and allocation ratio in China’s forests are keys for improving the fitting accuracy of regional N cycle models and provide a reference for regional management of fore st N .