Atmospheric nitrogen deposition changes silicon cycle in subtropical forest

Silicon (Si) is the second−most−abundant element in the earth's crust, which facilitates plant growth and defense and is closely associated with the carbon (C) cycle of terrestrial ecosystems. The absorption and utilization of Si by plants affect the biogeochemical cycle of Si and its coupling with C cycle. However, potential mechanisms by which atmospheric nitrogen (N) deposition affects Si cycle in subtropical forests are not clear. Investigating Si dynamics in the plant-soil systems under N deposition and its driving factors are beneficial to reveal the response pathways and mechanisms of Si− and C−cycling processes in forest ecosystems under global changes.

Based on the nine−years of canopy and understory N addition experiment at Shimentai, our results showed that: 1) under high N addition (50 kg N ha-1 y-1), plant available Si (mobile Si, H2O2−Si ) significantly increased, while amorphous Si significantly decreased, in surface soils; 2) N addition significantly enhanced the rates of carboxylate exudation and leaf phytolith concentrations, but decreased soil pH; 3) rhizosheath organic acids, soil pH and CaCl2−Si dominating phytolith concentrations in tree leaves. Our results imply that long−term atmospheric N deposition may promote the bioavailability of soil Si and plant Si accumulation in subtropical forests. Given that Si and C are interactively coupled, changes in Si biogeochemical cycling will inevitably affect C dynamics and their responses to atmospheric N deposition.

The study titled " Atmospheric nitrogen deposition: what are the impacts of silicon dynamics in a subtropical forest? " was published online in Plant and Soil. Heng Yu and Zhangfen Qin were considered joint first author of this paper and Professor Yuanwen Kuang is the corresponding author. This study was supported by Key−Area Research and Development Program of Guangdong Province, Guangdong Flagship Project of Basic and Applied Basic Research, Guangdong Science and Technology Plan Project. The article link is: https://doi.org/10.1007/s11104-024-06872-8.

First author information: Heng Yu: Ph.D., Research Center for Ecology and Environmental Sciences, South China Botanical Garden, Chinese Academy of Science, Research field: Forest ecology and Si cycle, E-mail: yuheng@scbg.ac.cn.

Fig 1. Effects of nitrogen addition on different forms of soil silicon in subtropical forests

Fig 2. Dominant factors affecting leaf phytoliths in subtropical forests