Soil physical and chemical characteristics of Castanopsis hystrix mature forests in Guangxi

Investigation of soil physical and chemical characteristics of Castanopsis hystrix mature forests in different regions of Guangxi was studied to evaluate comprehensively the forests soil quality, and may provide insights for sustainable management of C. Hystrix forests.

Mature C. hystrix forests in 10 regions of Guangxi were selected as research materials, the soil characteristics were analyzed, and soil quality was evaluated by principal component analysis.

1) Soil physical properties were significantly different among regions. Soil depth significantly affected soil bulk density, maximum water holding capacity, capillary water holding capacity and capillary porosity. The bulk density increased along with the deepening of the soil layer, while the other 3 indexes mostly decreased, natural water content, non-capillary porosity and total porosity varied irregularly. Interaction effect of region and soil depth significantly influenced soil bulk density, maximum water holding capacity, capillary water holding capacity, non-capillary porosity, and total porosity. Coefficient variation (CV) analysis of soil physical properties showed that the variation was moderate; 2) Regions had extremely significant effects on soil chemical indexes. Soil depth significantly affected the contents of soil organic matter, total nitrogen, available potassium, available nitrogen and available phosphorus. As soil depth increased, the soil organic matter, total nitrogen, available phosphorus and available potassium decreased in most regions. The total potassium, total phosphorus, available nitrogen and pH values changed irregularly. CV of soil pH value was weak, CV of available nitrogen was strong, and CVs of other soil nutrients were moderate. Except for soil TN, all the other nutrients were in a state of deficiency; 3) Comprehensive evaluation of soil quality of the forests showed that 50% of the tested sites had soil evaluated at medium level, 20% at good level, and 30% at poor level.

In general, soil of mature C. hystrix forests in the regions had relatively appropriate permeability, aeration and water holding capacity. The soil was acidic and the soil nutrients varied moderately. The soil quality index increased from eastern Guangxi to southern Guangxi, and the soil quality of C. hystrix mature forest was mostly at a medium level. Soil quality and soil fertility could be maintained by planting C. hystrix in Guangxi.