Five-year nitrogen addition affects fine root exudation and its correlation with root respiration in a dominant species, Quercus crispula, of a cool temperate forest, Japan. (24th January 2020)

• Record Type: Journal Article
• Authors: Ataka, Mioko; Sun, Lijuan; Nakaji, Tatsuro; Katayama, Ayumi; Hiura, Tsutom
• Editors: Ryan, Michael
• Is Part Of: Tree physiology. Volume 40:Number 3(2020)
• Page Start: 367
• Page End: 376
• Publication Date: 2020-01-24
• Subjects: belowground C allocation strategy -- fine roots -- nitrogen addition -- respiration–exudation relation; Trees -- Physiology -- Periodicals; 582.16
• DOI: 10.1093/treephys/tpz143
• Languages: English
• ISSNs: 0829-318X

Abstract

Abstract: In forest ecosystems, fine root respiration directly contributes to belowground carbon (C) cycling. Exudation from fine roots indirectly affects C cycling via enhanced microbial decomposition of soil organic matter. Although these root-derived C fluxes are essential components of belowground C cycling, how nitrogen (N) addition affects these fluxes and their correlations remains unclear. In this study, fine root exudation, respiration and chemical/morphological traits were measured in a dominant canopy species, Quercus crispula Blume, found in a cool temperate forest, the Tomakomai Experimental Forest, Hokkaido University, which has undergone 5-year N addition. Soil-dissolved organic carbon (DOC) was also measured in both bulk and rhizosphere soils to evaluate the impact of fine root exudation on soil C cycling. Compared with a control plot with no N treatment, fine roots in the N addition plot exhibited larger diameters and higher N concentrations, but lower specific root lengths and areas. On a root-weight basis, respiration was not different between plots, but exudation was slightly higher under N addition. On a root-area basis, exudation was significantly higher in the N addition plot. Additionally, differences in DOC between rhizosphere and bulk soils were two times higher in the N addition plot than the control plot. Although fine root respiration was positively correlated with exudation in both the control and N addition plots, the ratio of exudation C to respiration C decreased after 5-year N addition. Nitrogen addition also affected absolute C allocation to fine root exudation and changed the C allocation strategy between exudation and respiration fluxes. These findings will help enhance predictions of belowground C allocation and C cycling under N-rich conditions in the future.