不同干扰措施下黄土丘陵区人工刺槐林生长结构及土壤理化性质分析

Soil Physio-Chemical Properties and Growth Structure with Different Interfering Measures in Robinia Pswudoacacia Forests in Loess Hilly Region

为合理经营管理人工刺槐林,提高其稳定性,通过野外调查与室内分析相结合的方法,对不同干扰措施下林龄为30a左右的刺槐×柠条,刺槐×油松,刺槐×连翘等3种混交林中刺槐与33龄刺槐纯林的生长指标、土壤理化性质及林下植物多样性进行了分析。结果表明,不同的抚育管理方式对混交林和纯林中刺槐乔木的密度影响较小,刺槐通过无性繁殖自我修复,密度均维持在1 000～1 500株/hm2;纯林中乔木蓄积量显著高于3种混交林;纯林径阶主要分布在8～16cm,占样地内刺槐的79.31%,混交林主要分布在2～12cm,占样地内刺槐的82.58%左右;纯林内刺槐胸径与其树冠的投影面积相关系数r=0.385,混交林内的刺槐为r=0.735,混交林内刺槐树形结构好于纯林;纯林对土壤容重、有机质的改善作用差于混交林,混交林中以刺槐×柠条林改善土壤容重作用最显著,纯林和混交林在0—5cm土层的有机质含量平均值分别为15.50,15.19g/kg,5—60cm土层有机质含量平均值混交林较纯林高70.6%;纯林林下草本层多样性指数高于混交林,但丰富度指数、均匀度指数均低于混交林。

The major goal of this study is to develop reasonable operation and management practices of Robinia pswudoacacia plantation and improve its stability.Different interfering measures,including Robinia with Caragana,Robinia with pine and Robinia with Forsythia,and Robinia pure forest were investigated through field survey and labortory analysis to analysis and compare the physical and chemical properties,the growth status,and understory species diversity of artificial pure and mixed Robinia.The result showed that different management methods have low influence on population density for the both mixed and pure Robinia;the density of Robina remained 1 000~1 500 plant/hm2 through self-propagation and repair.However,the volume of the pure forest was significant higher than the mixed forests.The stem diameter of pure forest ranged from 8 cm to 16 cm,accounting for 79.31% of Robinia in sample plot,while stem diameter of the mixed varied from 2 cm to 12 cm for 82.58% of the Robinia.The coefficient of correlation between diameter and the projection area of Robinia was 0.385 in pure forest,and 0.735 in the mixed forests.The structure and tree shape of mixed forests was better than that of the pure forest.The pure forest showed less effectiveness in improving soil bulk density and organic matter than the mixed forests;specifically,the Robinia and Caragana mixed forest exhibited the highest effectiveness.Soil organic matter contents of the pure and mixed forests in 0 to 5 cm soil layer were 15.50 g/kg and 15.19 g/kg,respectively.The average organic matter in 5 cm to 60 cm soil layer under the mixed forest was 70.6% higher than that under the pure forest.Diversity index of understory herb layer in pure forest was higher than the mixed,however,the richness and evenness index were lower.