Variation in the nitrogen concentration of the leaf, branch, trunk, and root in vegetation in China

Nitrogen (N) is an essential nutrient that is important for plant growth and productivity. How plants distribute N in different plant organs is aligned to the N use strategy of plants, and, in turn, provides an accurate way of assessing N storage in vegetation at the regional scale. Here, we analyzed variation in N concentrations across different organs and at different spatial scales. Specifically, we obtained 13,526 observations of plant N in China from consistent field measurements and from the published literature. The results showed that N concentration was significantly different across different plant organs (leaf, branch, trunk, and root), with more active organs having higher N. For forests, N concentration was ordered as: leaf (17.35 g kg−1) > root (6.66 g kg-1) > branch (6.47 g kg-1) > trunk (2.79 g kg-1). Similar trends were observed in grasslands, deserts, and wetlands. The N concentration of different plant organs significantly differed among different vegetation types [e.g., leaf N was ordered as: grassland (19.20 g kg-1) > desert (17.91 g kg-1) > forest (17.35 g kg-1) > wetland (14.58 g kg-1)]. Furthermore, N concentration in different plant organs significantly differed across various regions. With increasing latitude and decreasing mean annual temperature, the N concentration of different plant organs increased, to some extent. Our findings provide new insights about the differences in the N use strategy of plants across plant organs and at different spatial scales. In conclusion, the data assimilated here provide a systematic reference point for estimating vegetation N storage at different scales.