天然常绿阔叶林改造为板栗林对土壤有机碳库的影响

天然林改造为人工林后,由于植被覆盖类型和经营管理措施发生改变,从而显著影响土壤有机碳库的特征.测定浙江省临安市相邻的天然常绿阔叶林和板栗林(板栗林由常绿阔叶林改造而来,集约经营10年)表层(0～20 cm)和亚表层(20～40 cm)土壤有机碳储量和不同形态活性有机碳库,用固态核磁共振方法分析土壤有机碳的化学结构特征,研究天然常绿阔叶林改造为板栗林对土壤有机碳库的影响.结果表明: 常绿阔叶林改造为板栗林后,土壤表层有机碳储量、水溶性有机碳、热水溶性有机碳、微生物生物量碳和易氧化碳含量分别下降19.7%、34.4%、25.8%、30.4%和25.2%,土壤亚表层的各指标分别下降13.5%、38.4%、19.8%、34.1%和22.2%.土壤表层烷氧碳含量、芳香碳含量以及芳香度显著降低,而烷基碳含量、羰基碳含量以及A/O-A值均显著增加;土壤亚表层烷氧碳含量显著降低,而烷基碳含量和A/O-A值显著增加,而芳香碳含量、羰基碳含量以及芳香度无显著变化.天然常绿阔叶林改造为板栗林并长期集约经营后,土壤有机碳储量和活性有机碳库均显著下降,有机碳的化学结构发生显著变化.

Effects of conversion of evergreen broad-leaved forest to Chinese chestnut plantation on soil organic carbon pools.

Converting natural forests to plantations significantly affects the characteristics of soil organic carbon (C) pools, due to the changes of vegetation cover and management practices. In this paper, to investigate the effects of conversion from evergreen broad-leaved forest (EBF) to Chinese chestnut plantation (CP) on soil organic C pool, the soils from surface (0-20 cm) and subsurface (20-40 cm) layers were sampled from the above two forests (the CP was converted from the EBF and had been intensively managed for 10 years) in Lin’an City, Zhejiang Province. The soil orga-nic C storage, labile organic C pools, and other basic soil properties were determined. The chemical composition of soil organic C was determined by nuclear magnetic resonance (NMR) technique. Results showed that the soil organic C storage, water soluble organic C (WSOC), hot water soluble organic C (HWSOC), microbial biomass C (MBC) and readily oxidizable C (ROC) concentrations in the surface layer decreased by 19.7%, 34.4%, 25.8%, 30.4% and 25.2%, respectively, after the conversion from EBF to CP. Such values for the subsurface layers decreased by 13.5%, 38.4%, 19.8%, 34.1% and 22.2%, respectively. The O-alkyl C content, aromatic C content and aromaticity of soil organic C in the surface layer decreased signi-ficantly by the land-use conversion, while alkyl C content, carbonyl C content and alkyl C to O-alkyl C (A/O-A) ratio increased signi-ficantly. The O-alkyl C content of soil organic C in the subsurface layer decreased significantly by the land-use conversion, alkyl C content and A/O-A ratio increased significantly, and aromatic C content, carbonyl C content and aromaticity of soil organic C were not changed. In conclusion, conve-rting EBF to CP and subsequent intensive management significantly decreased the soil organic C sto-rage and labile C pool contents and altered the chemical composition of soil organic C.