关键词: 桂西北, 喀斯特, 石灰土, 红壤, 肥力, 鱼类,  , 网目规格, 物种组成, 体长分布, 刀鲚

Abstract: Taking the soils developed on limestone and sandstone and with typical land use patterns in Karst region of Northwest Guangxi as test objects, this paper studied their soil fertility  under effects of parent rock and land use pattern. A total of eleven soil fertility variables were selected for factor analysis, and the component score for each sampling site was assessed by using principal component analysis (PCA) sequencing and clustering diagram. The factor analysis indicated that the eleven variables could be reduced to four components, i.e., overall soil fertility, soil pH and total phosphorus, soil available phosphorus, and soil total potassium. The PCA sequencing and clustering analysis showed that the overall soil fertility  was mainly affected by land use pattern, being the highest in abandoned farmland. Soil pH and total phosphorus content were mainly affected by parent rock. The pH value and total phosphorus content in the red soil developed on sandstone were much lower than those in the calcareous soil developed on limestone. Soil available phosphorus and total potassium contents were significantly affected by fertilization. The available phosphorus and total potassium contents in Karst calcareous soil and red soil were lower than the average level of China soils. Therefore, the Karst calcareous soil should be fertilized with ammonium nitrogen fertilizer to improve its phosphorus availability, while the Karst red soil should be amended with lime to increase its available phosphorus content. In addition, potassium fertilizer should be applied to the two soil types to improve their soil fertility.

Key words: Northwest Guangxi, Karst, calcareous soil, red soil, fertility, fish,   , mesh size, species composition, total length distribution, Coilia nasus.