Influence of nitrogen deposition on soil iron and aluminum oxides in a subtropical Castanopsis carlesii natural forest

• 1、School of Geographical Sciences，Fujian Normal University，Fuzhou 350007
• 2、 Key Laboratory for Subtropical Mountain Ecology（Ministry of Science and Technology and Fujian Province Funded )，Fuzhou 350007

Abstract：Iron (Fe) and aluminum (Al) oxides, essential components of soil marines, are key factors in maintaining acid buffer capacity. High nitrogen (N) deposition will profoundly affects the minerals composition in subtropical forest ecosystems, however research in the field is precious few. To investigate how soil Fe and Al oxides and physicochemical property responds to nitrogen deposition, we imitated nitrogen deposition in a Castanopsis carlesii natural forest in Sanming Fujian Province in China during the period from 2012 to 2018. Soils were collected from control plots (CT), low-nitrogen addition plots (LN) and high-addition plots (HN). We measure the physicochemical properties of the soil and concentrations of three different forms of Fe and Al oxides in the soil. The results showed that N deposition decreased pH in the soil compared with control treatment, however it had little effect on soil organic matter (SOC), total nitrogen content (TN) and total phosphorus content. The concentration of free Fe and Al (Fed and Ald) and organic-bound Fe and Al (Fep and Alp) in the soil fell significantly after N deposition. By the contrast, amorphous Fe and Al (Feo and Alo) were remarkably enhanced under the HN treatment. The results suggest that N deposition can cause decreases of concentrations of Fe and Al oxides, which means long-term nitrogen deposition may weaken acidification buffer capacity of subtropical forest soils and influence functions of forest ecosystems in the region.

Keywords： natural Castanopsis carlesii forest soil acidification free Fe and Al organic-bound Fe and Al amorphous Fe and Al