Distribution characteristics of soil organic carbon, nitrogen and phosphorus in densely populated village landscapes of different hilly regions of China
JIAO Jia-guo1,2, YANG Lin-zhang2, WU Jun-xi3, LI Hui-xin1, E. C. Ellis4 (1College of Resources & Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China; 2Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China; 3College of Agronomy & Agrcecology, China Agricultural University, Beijing 100094, China; 4Department of Geography and Environmental Systems, University of Maryland, Baltimore County 21250, Maryland, USA).
Based on high spatial resolution remote sensing map (1 m) and sampling with a stratified design on different site types, the effects of fine-scale land use patterns in villages on top soil (0-30 cm) organic carbon (OC), total nitrogen (TN) and total phosphorus (TP) within and across the densely populated hilly landscapes, i.e., Sichuan Hilly Region (SIHR; Jintang County, Sichuan Province), Subtropical Hilly Region (SUHR; Yiyang County, Hunan Province), and Tropical Hilly Region (THR; Dianbai County, Guangdong Province), were investigated. The results showed that soil OC density was decreased in the order of SUHR (2.72±0.76 kg·m-2)THR (2.65±0.73 kg·m-2) SIHR (2.15±0.57 kg·m-2), TN density was in the order of SUHR (0.28±0.06 kg·m-2)SIHR (0.27±0.06 kg·m-2)THR (0.21±0.06 kg·m-2), and TP density was in the order of SIHR (0.19±0.04 kg·m-2) SUHR (0.11±0.03 kg·m-2) THR (0.08±0.04 kg·m-2). The fine-scale landscape units (ecotopes) with the highest soil OC, TN and/or TP stocks were rainfed annual crops in SIHR, paddy rice in SUHR, and open canopy trees and brush in THR, respectively. In all hilly regions, paddy and forest land use classes had the highest soil OC and TN density, while mined areas had the lowest soil OC and TN density, with the distribution of TP density showing a more complicated pattern than that of OC and TN. Ecotope level analysis could reflect the soil organic carbon, nitrogen and phosphorus distribution in densely populated village landscape of hilly regions more comprehensively than land use or land cover analysis.