Open AccessWeak growth response to nitrogen deposition in an old‐growth boreal forest
Author(s) -
Du Enzai,
Fang Jingyun
Publication year - 2014
Publication title -
ecosphere
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.255
H-Index - 57
ISSN - 2150-8925
DOI - 10.1890/es14-00109.1
Subject(s) - nitrogen , taiga , deposition (geology) , biomass (ecology) , agronomy , phosphorus , boreal , ecosystem , nutrient , zoology , environmental chemistry , chemistry , environmental science , biology , ecology , paleontology , organic chemistry , sediment
Nitrogen (N) deposition has been enhanced globally due to the dramatic increase in anthropogenic N emissions, but the effects of N deposition on the growth of old‐growth forests remain poorly understood. A three‐year N enrichment experiment (0, 20, 50 and 100 kg N ha −1 yr −1 ) was conducted in an old‐growth boreal forest in Northeast China to explore its growth response to enhanced N deposition. Nitrogen enrichment significantly increased N availability but caused only a very weak stimulation of growth (<3 kg C/kg N), indicating a minor N limitation. Nitrogen enrichment did not significantly influence the mass production of needle‐leaves but increased the production of woody biomass, leading to a slight improvement in growth efficiency. Nitrogen content increased and phosphorus (P) content decreased in freshly fallen needle‐leaves, leading to an increase of N:P ratios. The failure of P acquisition to match the increased N uptake suggests a limitation of soil P availability. Our results support the hypothesis of progressive N saturation and indicate that N deposition may cause a very weak stimulation of carbon sequestration in old‐growth forests.