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Soil fertility characteristics under different land use patterns in depressions between karst hills.

LIU Yan1,2,3,4, SONG Tong-qing2,3, CAI De-suo1, ZENG Fu-ping2,3, PENG Wan-xia2, DU Hu2   

  1. (1College of Civil Engineering and Architecture, Guangxi University, Nanning 530004, China; 2Key Laboratory of Agroecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China; 3Huanjiang Observation and Research Station for Karst Ecosystems, Chinese Academy of Sciences, Huanjiang 547100, Guangxi, China; 4Guangxi Soil and Water Conservation Monitoring Station, Nanning 530023, China)
  • Online:2014-06-18 Published:2014-06-18

Abstract: Soil samples were collected from the depressions between karst hills by grid sampling method (5 m × 5 m), soil pH, soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), total potassium (TK), available nitrogen (AN), available phosphorus (AP), and available potassium (AK) in surface layer (0-20 cm) under different land use patterns (burning, cutting, cutting plus root removal, enclosure, maize plantation, and pasture plantation) were measured, the main factors of influencing the soil fertility was identified by principal component analysis (PCA), and the relationships between soil nutrients and microorganisms were demonstrated by canonical correlation analysis (CCA). The results showed that the soil was slightly alkaline (pH 7.83-7.98), and the soil fertility differed under the different land use patterns, with 76.78-116.05 g·kg-1 of SOC, 4.29-6.23 g·kg-1 of TN, 1.15-1.47 g·kg-1 of TP, 3.59-6.05 g·kg-1 of TK, 331.49-505.49 mg·kg-1 of AN), 3.92-10.91 mg·kg-1 of AP, and 136.28-198.10 mg·kg-1 of AK. These soil indexes except pH showed moderate or strong variation. Different land use patterns had various impacts on soil fertility: Soil nutrients such as SOC, TN, TP, and AN were most significantly influenced by land use patterns in the depressions between karst hills; Followed by soil microorganisms, especially soil actinomycetes, and the effect decreased with the increasing gradient of human disturbance from enclosure, burning, cutting, cutting plus root removal, pasture plantation, and maize plantation. CCA elucidated that considerable interactions existed in soil TP with MBP (microbial biomass phosphorus), TK with MBC (microbial biomass carbon), TN with actinomycetes in the burned area, while TN and MBC in the cutting treatment, AP and MBN (microbial biomass nitrogen) in the treatment of cutting plus root removal, pH with MBC and fungus in the enclosure treatment, TN and TK with MBP in the maize plantation, pH with fungi and actinomycetes in the pasture plantation. Land use patterns changed the soil fertility in the depressions between karst hills; therefore, in the ecological restoration and reconstruction of karst region with fragmented landforms and shallow soil, rational land use patterns should be adopted to improve the soil quality of degraded ecosystems.