不同经营密度对柳杉纯林土壤理化性质的影响

在密度分别为1 450、1 800、2 075、2 700株/hm2的试验样地上,对广西六万林场柳杉纯林的土壤理化性质进行研究,为提高广西柳杉的合理种植水平提供参考依据。在各样地采集土壤样品,于实验室内,对所取样品进行土壤理化性质的分析。结果表明,在土壤物理性质方面,土壤容重随柳杉密度的增加而减少,土壤持水量和孔隙度与土壤容重密切相关;在土壤化学性质方面,0~20 cm土层的土壤各养分均高于20~40 cm土层;上层土壤中的各养分含量变化不规律,土壤有机碳、水解性氮和速效钾含量在密度为2 075株/hm2时均处于较高水平,而下层土壤有机碳与林分密度呈正相关,速效钾呈不规律变化,水解性氮出现先上升后下降的趋势。从林地土壤理化性质的角度,建议将柳杉人工林的林分密度控制在2 075株/hm2,从而有利于该地区柳杉纯林的林木收获量。

Influence of different management densities on soil physical and chemical properties in pure plantation Cryptomeria fortunei

The study on soil physical and chemical properties in pure forest of Cryptonmeria fortunei in Liuwan Forest Farm ofGuangxi was intended to provide scientific reference for the reasonable planting density of Cryptonmeria fortunei in Guangxi. The density of four standard plots were 1 450 plant/hm2, 1 800 plant/hm2, 2 075 plant/hm2 and 2 700 plant/hm2, respectively.The analysis on physical and chemical properties of soil which sampled from each sample plot shows that soil bulk density tended to decrease with increasing density, was closely related with the soil water retaining capacity and soil porosity in soil physical properties aspect. The nutrition contents were higher at 0~20 cm depth than at 20~40 cm depth. Nutrition of upper layer changed irregularly under different stand density. The contents of soil organic carbon, hydrolysable nitrogen and soil available potassium were in the high level under 2 075trees /hm2 stand density. However, in subsoil soil organic carbon was positively correlated with stand density, soil available potassium changed irregularlyand hydrolysable nitrogen increased at first and then decreased. Based on the soil physical and chemical properties, 2 075 plant/hm2 should be the reasonable density to g ncrease the forest yield of Cryptomeria fortunei plantation in this area.