Composition And Variation Of Soil Delta N-15 Stable Isotope In Natural Ecosystems

The natural abundance of delta N-15 in soils is a simple tool for understanding ecosystem nitrogen cycling. However, the main drivers for soil delta N-15 in different natural land use types are not clear enough. To investigate the main drivers for soil delta N-15 in different land uses, we measured delta N-15 in the top 10 cm of the soil along a precipitation gradient with various land uses on the Loess Plateau of China, which covers a total area of 620,000 km(2) and is one of the most erodible area in the world, to determine effects of climatic, soil and vegetation factors on soil delta N-15 and the relationships between them using the partial least squares regression (PLSR) method. Soil delta N-15 ranged from 1 parts per thousand to 9 parts per thousand on the Loess Plateau with an average of 5.8 parts per thousand in forest lands, 5.6 parts per thousand in shrub lands, and 4.8 parts per thousand in grasslands. Calculated variable influence on projection by PLSR showed that both soil properties (including soil organic carbon content, total nitrogen content and soil texture) and mean annual precipitation influenced soil delta N-15 strongly. In addition, site elevation also influenced soil delta N-15 strongly in forest lands. The dominant controls of soil delta N-15 varied among three land use types on the Chinese Loess Plateau, and PLSR would be a reasonable tool to predict soil delta N-15.