北京八达岭不同密度油松土壤团聚体特征研究

为研究林分密度对土壤团聚体稳定性的影响，以北京市八达岭林场3种不同密度（低密度500~800株/hm2,中密度1000~1200株/hm2,高密度1400~1600株/hm2）油松人工林为研究对象，通过野外调查采样和室内测定，系统分析了各林分分形维数、不同粒级团聚体保存率和团聚体稳定性指数。结果表明：林分密度显著影响土壤团聚体分形维数，3种不同密度油松人工林土壤团聚体分形维数（干筛）介于262~276，低密度林地分形维数最小，高密度林地分形维数最大；土壤水稳性团聚体分形维数（湿筛）与林分密度呈正相关，变化范围是264-279；低密度林分0~10cm土层分形维数最小，高密度林分20~30cm土层分形维数最大；各粒级团聚体保存率均大于05，其中05~025mm粒级团聚体保存率最大，水稳性最强，1~05mm粒级团聚体保存率最小，水稳性最弱；团聚体稳定性指数介于362~455，林分密度增加团聚体稳定性指数逐渐减小。低密度林分土壤团聚体稳定性更好，更有利于水土保持，建议将该区域油松人工林密度控制在500~800株/hm2。

Effect of Stand Density on Characteristics of Soil Aggregates in Pinus tabuliformis Plantation in Badaling Area,Beijing

To identify the effect of stand density on soil structure, fractal dimension, soil aggregate saving probability and aggregate stability index were analyzed based on field survey and sampling in three Pinus tabuliformis plantation with stand density of 500-800trees/ hm2 (Low density, LD), 1000 -1200 trees/ hm2 (Middle density, MD) and 1400-1600 trees/hm2 (High density, HD) respectively in Badaling area of Beijing. The results showed that stand density had a significant influence on fractal dimension of soil aggregate (dry sieving), it was ranged from 262 to 276 with the largest in the HD Pinus tabuliformis plantations and the smallest in the LD plantations. The fractal dimension of water stable aggregate (wet sieving) was between 264 and 279 and positively correlated with stand density. The smallest fractal dimension was found at the 0-10cm layer in LD plantation and the largest one was found at the 20-30cm depth in HD plantation. All the aggregate saving probability of the forest soil was >05, the soil aggregate of 05-025 mm had the highest stability for the largest saving probability and soil aggregate of 1-05 mm was the most unstable as it was the smallest saving probability. The aggregate stability index ranged from 362 to 455, and decreased with the increasing of stand density. In general, Soil aggregate in the LD Pinus tabuliformis plantation was the most stable and was good for soil and water conservation. Therefore, we suggested stand density of 500-800 trees/hm2 of the Pinus tabuliformis plantation in the research area for improving soil aggregate structure.