Eighteen-year nitrogen addition does not increase plant phosphorus demand in a nitrogen-saturated tropical forest

Guangcan Yu, Jing Chen, Mengxiao Yu, Andi Li, Ying Ping Wang, Xinhua He, Xuli Tang, Hui Liu, Jun Jiang, Jiangming Mo, Shuo Zhang, Junhua Yan, Mianhai Zheng

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)

Abstract

Nitrogen (N) deposition usually increases plant tissue N concentrations and thus phosphorus (P) demand in young and/or N-limited forests, but the N deposition effect on plant P demand has rarely been assessed in N-saturated forests. Impacts of 18-year external N additions (Control: 0, Low N: 50, Moderate N:100 and High N: 150 kg N ha−1 year−1) on leaf P of four plant life-forms (tree, shrub, herb and liana), P fractions of bulk and rhizosphere soils were examined in a N-saturated mature tropical forest in southern China. Leaf N, P and N: P ratios of all plant life-forms remained stable under three N additions. Among soil P fractions, moderate labile organic P increased by 25%–33% across three N additions; and soil total P was increased by 11.76% under Low N, and 8.87% under High N, compared with the control. The PLS-PM results showed that path coefficient of microbial community to available P significantly increased and of inorganic P to available P significantly decreased under N additions than control. N additions improved soil P availability through microbe-mediated P transformation: Low N significantly increased soil microbial taxonomic diversity, and a higher microbial diversity could enlarge the sources of nutrient acquisition and stimulate decomposition of recalcitrant organic matters; while High N significantly decreased soil microbial taxonomic diversity, the remaining microorganisms that were screened by N-rich environments had the characteristics of resisting the N addition effects and maintained efficient P acquisition. Synthesis. Our findings provide a novel line of evidence that long-term N deposition did not increase plant P demand in a N-saturated mature tropical forest. The underlying mechanism is that plants did not increase N uptakes therefore nor increase P uptakes (a stable leaf N: P stoichiometry) in an already N-saturated ecosystem. Different N addition rates regulated soil P transformation via microbial community transition. These findings help improve the understanding of plant P acquisition and modelling of biogeochemical N–P cycling and vegetation productivity in N-rich forest ecosystems, particularly considering the fact that chronic N deposition may likely lead to soil N richness and even saturation of many forests in the future.

Original languageEnglish
Pages (from-to)1545-1560
Number of pages16
JournalJournal of Ecology
Volume111
Issue number7
DOIs
Publication statusPublished - Jul 2023

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