The relative importance of climatic and edaphic factors as drivers of
plant (L.chinensis) 15N in China’s temperate grasslands
Abstract
Many studies have showed that climatic and edaphic variables influence
the variations of nitrogen isotopes in terrestrial ecosystems. However,
the relative importance of climate and soil variables on plant 15N
remains unclear, which limits the understanding mechanism of plant 15N
variation. In this study, the 15N values of Leymus chinensis (a
widespread species) and the corresponding climate and soil variables
were investigated from 40 sampling sites in temperate grasslands of
northern China. We disentangled and estimated the influences of climatic
and edaphic variables on plant 15N through the variable importance in
projection (VIP) technology based on partial least squares-regression
(PLS) analysis. Results showed that the 8 variables can explain
69%~87% of the variance of plant 15N along the
transect, and climatic factors contributed more than edaphic factors
(41% vs. 37%). Among the climatic variables, MAP was the most
important control variable, which explained approximately 25% of the
variation in plant 15N, followed by MAT. As for edaphic factors, soil N
had the most significant effect on plant 15N abundance, and its relative
contribution was about 15%, followed by SWC and soil δ15N. The relative
influences of other variables such as MARH, soil pH and C/N ratios were
less important in determining plant δ15N. In addition, a
high-performance model for predicting plant δ15N was built by the VIP
screening method. Further research should focus on the interaction of
climate and soil variables on different scale patterns of nitrogen
isotope.