[Community traits of soil fauna in forestlands converted from cultivated lands in limestone red soil region of Ruichang, Jiangxi Province of China].

This paper studied the variations of the community composition and individuals' number of soil fauna in limestone red soil region of Ruichang, Jiangxi Province after six years of converting cultivated lands into forestlands. Three converted forestlands, including the lands of mixed multiple-species forest, bamboo-broadleaved forest, and tree-seedling integration, were selected as test objects, with cultivated lands as the comparison. A total of 34 orders, 17 classes, and 6 phyla of soil fauna were observed in the converted forestlands. The dominant group was Nematoda, accounting for 86.7% of the total, whereas Acarina, Enchytraeidae, and Collembola were the common groups. In the cultivated lands, soil fauna had 21 orders, 10 classes, and 5 phyla. The dominant group was also Nematoda, accounting 86.7% of the total, and Acarina and Enchytraeidae were the common groups. In the converted forestlands, the group number of rare species was greater than that in the cultivated lands (30 vs. 18), and, except in winter, the group number and average density were significantly higher than those in the cultivated lands (P < 0.05). The vertical distribution of soil fauna in the soil profiles showed an obvious surface accumulation, which was more apparent in converted forestlands than in cultivated lands, and the individuals' number had significant differences between the surface (0-5 cm) layer and the 5-10 cm and 10-15 cm layers (P < 0.01) for both the converted forestlands and the cultivated lands. The group number of soil fauna in the converted forestlands had a seasonal variation ranked in the order of summer > autumn > spring > winter, and there was a significant difference between summer-autumn and spring-winter. The average density of the soil fauna also had a seasonal variation but ranked as autumn > summer > spring > winter, and the differences among the seasons were significant (P < 0.05). The biodiversity index of soil fauna was significantly higher in converted forestlands than in cultivated lands, and was the highest in mixed multiple-species forestland and the least in tree-seedling integration land.

[Effects of converting cultivated land into forest land on the characteristics of soil organic carbon in limestone mountain area in Ruichang, Jiangxi].

Taking the forest lands having been converted from cultivated land for 5 years in Ruichang City of Jiangxi Province as test objects, this paper studied the characteristics of soil organic carbon (SOC) under 4 different conversion models (forest-seedling integration, pure medicinal forest, bamboo-broadleaved mixed forest, and multi-species mixed forest). After the conversion from cultivated land into forestlands, the contents of SOC, microbial biomass carbon (MBC), and mineralizable carbon (PMC) in 0-20 cm soil layer increased by 24.4%, 29%, and 18.4%, respectively, compared with those under the conversion from cultivated land into wasteland (P < 0.05), which indicated that the conversion from cultivated land into forest lands significantly increased the SOC content and SOC storage. The SOC, MBC, and PMC contents in 0-10 cm soil layer were significantly higher than those in 10-20 cm soil layer (P < 0.01), and the differences between the soil layers of the four forest lands were higher than those of the wasteland. Among the 4 conversion models, forest-seedling integration had more obvious effects on SOC.