南亚热带不同林龄杉木针阔混交林土壤理化性质分析

Physical and Chemical Characteristics of Soil of Cunninghamia lanceolata Conifer-broadleaved Mixed Forest with Different Age

森林发育对土壤理化性质有着重要的影响。在南亚热带，以杉木皆伐改造林地3个林龄段（3～5 a、7～9 a和10～11 a）的针阔混交林为研究对象，研究了土壤理化性质的变化特征以及不同理化性质指标之间的相关性。结果表明，土壤容重、总孔隙度、毛管孔隙度随林龄的增加呈上升趋势，而非毛管孔隙度和土壤通气度表现为先升高后降低。土壤pH值、有机质、全N、全P、全K、水解N、速效K随林龄的增加呈现出先降低后升高的趋势，而有效P处于下降的趋势。相关分析表明，不同林龄段针阔混交林的土壤容重主要取决于土壤有机质含量，自然含水量主要取决于毛管孔隙度；土壤有机质含量与全N和水解N相关性最高，土壤中绝大部分N素以有机态存在；而土壤有效P含量主要取决于土壤有机质含量，同时受土壤pH值影响也较大。

Forest development has great influence on physical and chemical characteristics of soil.A study was conducted on variation of soil physical and chemical characteristics and correlations between these indicators in conifer-broadleaved mixed plantations in southern subtropical region.These conifer-broadleaved mixed plantations which developed from clearcutting Cunninghamia lanceolata plantation were in different age group （3-5 ,7-9 and 1 0-1 1 years old）.The results were as following：soil bulk density,total porosities and capillary porosities in-creased,while non-capillary porosities and soil aeration capacity first increased and then decreased with increasing forest age.The pH of soil,soil organic matter,total N,total P,total K,hydrolysable N,available K first de-creased and then increased,while available P decreased with increasing forest age.The correlation analysis showed that soil bulk density depended on soil organic matter content for conifer-broadleaved mixed forest in southern sub-tropical region,while soil natural water content mainly depended on capillary porosities.Soil organic matter content was highly correlated with total N and hydrolysable N content,indicating that N in the soil organic matter existed mainly in the form of organic nitrogen.The available P content mainly depended on soil organic matter content,and was influenced by soil pH value.