Effect of nitrogen addition on the decomposition and release of compounds from fine roots with different diameters: the importance of initial substrate chemistry

Abstract

Initial substrate chemical characteristics are the most important factor in the regulation of fine root decomposition. However, it remains unclear how nitrogen (N) deposition changes the decomposition process by affecting initial substrate chemical characteristics with different fine root diameter sizes. We compared the root decomposition processes across three diameter sizes (very fine roots, 0.05), but low N addition enhanced the correlation coefficients between initial chemical indexes and decomposition rates. (3) Low N addition increased the release rates of C and cellulose in the very fine roots but not intermediate fine and largest fine roots, while the medium and high N addition decreased the release rates of N, P, cellulose and lignin in the very fine and intermediate fine roots by affecting the initial C, N, P, starch, cellulose and lignin concentrations. (4) Release of compounds from large diameter fine roots is less responsive to N addition than that from the small ones. The initial substrate chemistry plays an important role during the N addition affecting fine root decomposition and release of chemical compounds. Our results suggest that N deposition may change the biogeochemical processes of forest ecosystems by affecting the release of compounds from fine roots.