Soil phosphorus compared to nitrogen limitation increases the uncertainty of subsoil organic carbon sequestration in Pinus massoniana mixed forests

Fenghua Tang; Yunchao Zhou; Piaoyun Deng; Jirong Feng; Yuexiong Mao; Yaoxiong Wang; Qianbin Cao; Zhengui Han; Lulu Meng; Yunxing Bai

doi:10.1016/j.jenvman.2024.123418

Soil phosphorus compared to nitrogen limitation increases the uncertainty of subsoil organic carbon sequestration in Pinus massoniana mixed forests

J Environ Manage. 2024 Nov 21:372:123418. doi: 10.1016/j.jenvman.2024.123418. Online ahead of print.

Authors

Affiliations

¹ Institute for Forest Resources & Environment of Guizhou, Key Laboratory of Forest Cultivation in Plateau Mountain of Guizhou Province, College of Forestry, Guizhou University, Guiyang, China.
² Institute for Forest Resources & Environment of Guizhou, Key Laboratory of Forest Cultivation in Plateau Mountain of Guizhou Province, College of Forestry, Guizhou University, Guiyang, China. Electronic address: yczhou@gzu.edu.cn.
³ Guizhou Provincial State-owned Longli Forest Farm, China.

PMID: 39577193
DOI: 10.1016/j.jenvman.2024.123418

Abstract

Limited nitrogen (N) and phosphorus (P) availability will constrain terrestrial carbon sinks in the 21st century. Mixed forests improve the plant community composition and productivity of pure coniferous forests. Nevertheless, it is uncertain whether and to what extent changes in soil N and P dynamics caused by mixed forests can affect forest soil organic carbon (SOC) stocks. The research purpose is to demonstrate and evaluate the effects of soil N and P on SOC stocks in Pinus massoniana mixed forests. Our meta-analysis, which included 616 paired observations, revealed that the coupling of soil N, P, and plant species richness (PSR) contributed 22.6%, 28.8%, and 28.4%, respectively, to SOC stock accumulation in the topsoil (0-20 cm), subsoil (20-100 cm), and whole profile (0-100 cm). The interactions between soil total N and P concentrations (TN:TP ratios) dominated the increase in SOC stocks in the mixed forest topsoil and whole profile, explaining 35.6% and 20.3% of the variation, respectively. Conversely, independent TN and TP concentrations were the primary contributors (explained by 17.5% and 12.3%, respectively) to subsoil SOC stocks increase. The TN and TP concentrations limit SOC stock accumulation in mixed forests for the next 60 years (2025-2085), with the TP concentration and TN:TP ratio having a greater effect in subsoil. Fortunately, the TN and TP limitations on SOC stock increase in mixed forests can be mitigated and balanced by altering soil TN:TP ratio by increasing or decreasing the PSR (PSR thresholds for topsoil, subsoil, and whole profile were 15, 8, and 8, respectively). Overall, plant mixing fails to enhance plant availability of pure forest soil N and P. Accelerated N cycling and increased P reabsorption efficiency are optimal strategies for balancing N and P supply in mixed forests, promoting biomass accumulation, and ensuring SOC stocks increase.

Keywords: Carbon sequestration; Mixed forests; Nutrient limitation; Plant diversity; Soil stoichiometry.