[Fine root morphology and chemistry characteristics in different branch orders of Castanopsis platyacantha and their responses to nitrogen addition].

Fine root morphology and chemistry characteristics of dominant species Castanopsis platya-cantha in an evergreen broad-leaved forest in subtropical China and their response to nitrogen (N) addition were determined in order 1st to 5th. With the increase of root order, C. platyacantha root diameter, tissue density (RTD), and K content increased, and specific root length (SRL), speci-fic surface area (SRA) and contents of N, P and Mg decreased. Nitrogen addition significant increased N content and decreased Mg content and C/N of fine roots. Root tissue Ca content had a decrease trend under N addition treatments. There were neither significant effects on the contents of C, P, K, Na, Al, Mn, Fe of fine roots, nor on fine root diameter, SRL, SRA and RTD. Root P content had a significant liner relationship with root morphology in the all treatments. Nitrogen addition changed the linear relationships between tissue Mg content and root morphology from no significant relationship to significant relationship, and linear relationships between tissue N content and root morphology from significant relationship to no significant relationship. N addition would affect the root tissue nutrient contents and could enhance P and Mg requirement of plants.