不同人工林对奈曼沙区土壤团聚体的影响

Effects of different plantations on soil aggregates in the Nayman sand region

为分析奈曼沙区不同人工林土壤团聚体组成及其稳定性变化,从中筛选最佳水土保持与防风固沙林型。以奈曼沙区杨树、油松和樟子松人工纯林林下土壤为研究对象,通过干筛和湿筛的方法,研究0~20 cm、20~40 cm、40~60 cm土层土壤团聚体的组成,以土壤稳定性指标来评价土壤状况。结果表明:(1)3块人工林林下土壤大团聚体的含量在干筛和湿筛的结果中差异较大,其土壤结构体破碎率(PAD)值进一步说明水稳定性团聚体在反映奈曼沙区人工林土壤团聚体稳定性中更具有代表性,且2种筛分条件下,0~20 cm土层土壤>0.25 mm团聚体的含量(R_(>0.25))显著高于40~60 cm土层。(2)结合不同人工林对土壤团聚体R_(>0.25)、平均重量直径(MWD)、几何平均直径(GMD)、分形维数(D)值的表现,樟子松土壤结构性最好,其水稳定性最高,D值相对较低。(3)土壤团聚体直径值和分形维数D值与各粒径含量呈明显的线性关系,但是相关系数正负临界点不同,2 mm与0.25 mm粒级是土壤团聚化过程中的分界线,可分别作为表征土壤机械稳定性、水稳定性的直观参数。综合试验结果表明,对于生态脆弱的奈曼沙区种植樟子松可以有效改善土壤结构,适宜在该地固沙工作中推广。

To analyze the composition of soil aggregates and their stability changes in different plantation forests in the Nayman sand region and to select the best forest type for soil and water conservation as well as wind and sand stabilization,the soil in the understorey of poplar,oil and camphor pine plantation forests in the Nayman sand region was used as the research object,and the composition of soil aggregates in the 0-20 cm,20-40 cm,and 40-60 cm soil layers was investigated using dry and wet sieving methods,and the soil stability evaluation index was used to evaluate soil condition.The results showed that:(1)the content of large agglomerates in the three plantation sites differed significantly between the dry and wet sieve results.Their PAD values further indicated that water-stable agglomerates were more representative in reflecting agglomerate stabilty in plantation forests in the Nayman sand region,and the number of large agglomerates with R_(>0.25)was significantly higher in the 0-20 cm soil layer than in the 40-60 cm under the two sieving conditions.(2)Combining the effects of different plantation forests on soil agglomerates MWD,GMD,D,and R_(>0.25)values showed the best structural properties of camphor pine soils,which had the highest water stability and relatively low D values.(3)The soil agglomerate diameter index and the fractal dimension D are clearly linearly related to the content of each grain size,but the positive and negative thresholds of the correlation coefficients differ,indicating that the 2 mm and 0.25 mm grain classes are particularly important dividing lines in the soil agglomeration process,which can be used as intuitive parameters to characterize soil mechanical and water stability,respectively.The combined experimental results indicate that the planting of camphor pine in the ecologically fragile Nayman sand area can effectively improve the soil structure and is suitable for the extension in the sand consolidation work in this area.