华蓥市山区侧柏人工林土壤特性及水源涵养能力对林分密度的响应

为研究林分密度对侧柏人工林土壤特性及水源涵养能力的影响,以华蓥市7种林分密度侧柏林为研究对象,通过固定样地调查及取样分析方法,测定土壤理化性质、枯落物持水量并计算林地贮水能力,并采用方差分析、相关分析等研究了其对林分密度的响应,探讨林分最适留存密度,以期为当地侧柏人工林的可持续经营提供依据。结果显示:侧柏人工林枯落物最大持水率随林分密度增加先变大再减小,有效拦蓄量对林分密度的响应差异显著,中等密度(3 975株/hm~2)侧柏林拦蓄能力最优;林分密度对土壤团聚体分形维数、平均质量直径、平均几何直径都有显著影响,随着林分密度的增加均表现为先增加后减小的趋势,土壤团聚体有机质对林分密度响应差异显著,含量最高的为4 250株/hm~2;林分密度对土壤最大持水量和毛管持水量的影响差异显著,但较浅层土壤在675～5 300株/hm~2密度下土壤持水能力随林分密度变大而增强;综合来看,林下枯落物层是该地区侧柏人工林水源涵养功能的主体,林地有效拦蓄量按林分密度排序为3 975株/hm~21 475株/hm~24 250株/hm~25 775株/hm~25 300株/hm~22 675株/hm~2675株/hm~2,中等林分密度的涵养水源功能最佳。

Responses of Soil Characteristics and Water Conservation Capacity to Stand Densities of Planted Platycladus Orientalis in Mountainous Areas of the Huaying City

In order to study effects of different stand densities of planted Platycladus orientalis on soil characteristics and water conservation capacity, fixed plot investigations and sampling analyses for seven levels of stand density were carried out in mountainous areas in the Huaying city, and water holding capacities of litters and physicochemical properties of soils were measured for calculating water storage capacities of forests. Variance and correlation analyses of stand densities were conducted in this study to explore the optimal stand retention density and to provide a basis for the sustainable management of local plantation. The results showed that the maximum water holding capacity of planted Platycladus orientalis litters increased and then became decreasing as the forest density increasing. The effective interception capacity varied significantly with the forest density, and the optimal interception capability was found at the medium density (3 975 individuals/hm²). The stand density had significant effects on the fractal dimension, mean weight diameter and average geometric mean diameter of soil aggregates, as the stand density increasing, all of them showed a trend of increasing first and then decreasing. The organic matter contents of soil aggregates were affected by the stand density significantly, the highest organic matter content of soil aggregate was found at the stand density of 4 250 individuals/hm². The stand density also significantly affected the maximum water holding capacity and the capillary water holding capacity of soils, especially, the soil water holding capacity of shallow soil increased in the stand density range of from 675 individuals/hm² to 5 300 individuals/hm². In summary, the litter in the planted Platycladus orientalis forest played the major role in the water conservation. The effective interception capacity varied with forest land densities in an order of 3 975 individuals/hm² > 1 475 individuals/hm² > 4 250 individuals/hm² > 5 775 individuals/hm² > 5 300 individuals/hm² > 2 675 individuals/hm² > 675 individuals/hm², and the forest with medium stand density had the best ability in water conservation.