基于最小数据集的典型黑土区不同林龄小黑杨土壤质量差异

东北作为我国重要农产品基地,其黑土有机质含量可达普通土壤的十倍。近年来由于过度的开发与利用,导致黑土质量下降,因此研究农田防护林对土壤质量的改善具有战略意义。为探讨农田防护林对黑土质量的改善效果,以不同林龄(Y1:林龄是1 a的小黑杨;Y5:林龄是5 a的小黑杨;Y6:林龄是6 a的小黑杨;Y8:林龄是8 a的小黑杨)小黑杨林下土壤为研究对象,通过测定小黑杨防护林样地的土壤理化性质,分析不同林龄小黑杨林下土壤理化性质的差异,并通过最小数据集方法对林下土壤质量进行评价。结果显示:(1)不同林龄土壤质地为:Y1:砂质土壤;Y5:壤土;Y6:粉砂质土壤;Y8:粉砂质土壤。(2)土壤透气保水性随林龄增长向良性方向演化,表层土壤容重由1.33 g/cm³减小到1.17 g/cm³,不同土层间差异不显著,且土壤物理指标与树木生长量及其他土壤因子具有较强的相关性。(3)土壤pH随林龄减小,随土层呈波动性变化,范围在6.19-6.58之间。土壤养分随林龄呈波动性变化,垂直变化差异显著,除速效钾外均富集在表层,各土壤养分元素之间相关性较弱。(4)土壤微量元素有效态含量在不同林龄及土层均差异显著,且各元素之间相关性较强。(5)基于最小数据集的构建发现,影响不同林龄小黑杨土壤质量的最小数据集指标包括全氮、全钾、饱和持水量、速效磷、钙、锰,经总数据集验证所构建的最小数据集可体现小黑杨林下土壤质量有效信息。(6)小黑杨不同林龄土壤质量指数介于0.358-0.667,土壤质量综合得分排名为Y8 ＞ Y6 ＞ Y5 ＞ Y1。基于以上发现,小黑杨作为农田防护林对黑土区土壤质量改善效果明显,土壤保水透气性显著提升,土壤化学养分及微量元素含量部分提高,且不同林龄小黑杨对养分的循环利用效果差异显著。为实现黑土资源的合理利用,本研究建议随防护林林龄增加,更改林下套种作物以提高土壤质量及作物产量,为幼龄防护林对黑土区耕地的可持续利用提供科学依据。

Evaluation of differences in soil quality of Populus simonii×P. nigra (P. xiaohei) of different stand ages in typical black soil areas based on a minimum data set

As an essential base for agricultural products in China, the black soil in the Northeast region has an organic matter content of up to ten times that of ordinary soil. However, over-exploitation and utilization in recent years have led to a decline in the quality of black soil. Therefore, it is of strategic significance to study the improvement of soil quality by shelter-belts. In order to explore the effects of shelter-belts on the improvement of black soil quality, the soil under the Populus simonii×P. nibra (P. xiaohei) stands of different ages (Y1: 1-year-old P. xiaohei; Y5: 5-year-old; Y6: 6-year-old; Y8: 8-year-old) was used as the research object in this paper. The differences were analyzed by determining the soil physicochemical properties in the sample plots of P. xiaohei stands of different forest ages, and the under-story soil quality was evaluated by using the minimum data set method. The results showed that: (1) the soil texture of different forest ages was as follows: Y1: sandy soil; Y5: loamy soil; Y6: chalky soil; and Y8: chalky soil. (2) Soil permeability and water retention evolved in a benign direction with forest age, and the top soil bulk density decreased from 1.33 g/cm³ to 1.17 g/cm³, with non-significant differences between different soil layers, and the soil physical indexes had a strong correlation with tree growth and other soil factors. (3) Soil pH decreased with forest age and fluctuated with soil layers, ranging from 6.19 to 6.58. Soil nutrients fluctuated with forest age, with significant vertical variation, except for fast-acting potassium, which was enriched in the surface layer, and the correlation between soil nutrients was weak. (4) The effective state content of soil micro-nutrients varied significantly in different forest ages and soil layers, and the correlation between the elements was strong. (5) Based on the construction of the minimum data set, it was found that the minimum data set indicators affecting the soil quality of P. xiaohei at different forest ages included total nitrogen, total potassium, saturated water holding capacity, quick-acting phosphorus, calcium and manganese, and the minimum data set constructed by the total data set could reflect the effective information on the soil quality of the P. xiaohei forest. (6) The soil quality indices of different forest ages of P. xiaohei ranged from 0.358 to 0.667, and the comprehensive score of soil quality was ranked as Y8 ＞ Y6 ＞ Y5 ＞ Y1. Based on the above findings, P. xiaohei as shelter-belt has obvious effect on the improvement of soil quality in the black soil area, soil water retention and permeability is significantly improved, soil chemical nutrient and trace element content is partially increased, and the recycling effect of nutrients was better with the increase of forest age. In order to realize the rational use of black soil resources, this study suggests to change the under-story set crops to improve the soil quality and crop yield according to the age of shelter-belts, which can provide a scientific basis for the sustainable use of young shelter-belts on cropland in the black soil area.