Chin J Plan Ecolo ›› 2004, Vol. 28 ›› Issue (5): 623-629.DOI: 10.17521/cjpe.2004.0083

• Research Articles • Previous Articles     Next Articles

SPECTROSCOPIC CHARACTERISTICS OF SOIL ORGANIC MATTER IN DIFFERENT

YANG Jing-Cheng1,2, HUANG Jian-Hui1, PAN Qing-Min1, and HAN Xing-Guo1*   

  1. (1 Laboratory of Quantitative Vegetation Ecology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China) (2 Beijing Museum, Beijing 100050, China)
  • Published:2015-11-03
  • Contact: YANG Jing-Cheng

Abstract:

Previous studies have suggested that land use changes affect not only the content of soil organic matter (SOM), but also the chemical composition of SOM. The objective of this study was to confirm this finding at a site in tropical China. To understand the effect of land use changes on the quantity and quality of SOM, spectroscopic characteristics of humic acids from the topsoil (0-5 cm and 5-20 cm) and subsoil (20-40 cm) from a secondary tropical forest, a cropland, and a rubber tree plantation were investigated in Xishuangbanna, southwest China. The cropland had been cultivated for six years following the clearing of a secondary forest, and the 3-year old rubber tree plantation had been established on land that had been cultivated for 3 years following clearing of a secondary forest. Humic acids were extracted using an alkaline solution (0.1 M NaOH), and the extractions analyzed using Ultraviolet-visible spectroscopy (UV-VIS) and Fourier-Transform infrared spectroscopy (FT-IR). Six years after the conversion of secondary forest to cropland, SOM content in the 0-5 cm and 5-20 cm topsoil samples were reduced by 33.6% and 23.7%, respectively. Conversion of secondary forests to rubber tree plantations also greatly reduced SOM content by 28.6% in the top horizon (0-5 cm) and 27.6% at 5-20 cm depth. Comparison of UV-VIS spectra showed that E4/E6 ratios of humic acids from 0-5 cm and 5-20 cm depths in the secondary forest were higher than in the cropland and the rubber tree plantation soils, which indicated that the proportion of aromaticity in humic acids in the secondary forest was lower than the other two ecosystems. FT-IR spectra also indicated that land use change influenced the chemical composition of SOM. The proportion of carboxylic and phenolic groups in the humic acid was higher and the aliphatic and aromatic groups and polysaccharide-like substances were lower in the secondary forest than in the soils from the cropland and rubber tree plantation.