Factors affecting nitrogen concentration of fine roots in forest communities: Regression analysis of literature data

Literature data on nitrogen concentration of live fine roots (≤10 mm in diameter) in forest communities were analyzed by multiple linear regression. After appropriate transformations, root diameter, minimum monthly mean temperature, forest origin, and forest type together accounted for 93.2% of variation in N concentration. We suggest the following possible ecological bases: fine-root N concentration (1) was negatively related to root diameter because of increased percent old tissue and structural material with root size, (2) was negatively related to minimum monthly mean temperature because of a combined effect of soil available N, root absorption capacity, and carbon production, and/or because of selection pressure of cold winter on the genetic trait of higher N in fine roots, (3) was higher in plantations than in natural stands because of species and site selections and management history, and (4) was higher in broad-leaved than needle-leaved forests because of different N cycling rates.