基于分形维数的黄土丘陵沟壑区不同人工林对土壤结构和养分的影响

Effects of Different Plantations on Soil Structure and Nutrients in Loess Hilly and Gully Region Based on Fractal Dimension

研究黄土丘陵沟壑区不同人工林土壤颗粒的分形特征及其与土壤结构和养分的关系,以土壤体积分形维数来比较清水河县不同人工林对土壤结构和养分的影响,以期了解不同人工林土壤的结构和养分状况,为人工林的林种选取和合理化经营提供参考。以研究区9种人工林为研究对象,以无林地地作为对照,利用激光粒度仪测定土壤粒径分布并计算分形维数,用单项指标评价养分状况,将土壤分形维数与养分进行相关分析。研究区人工林土壤体积分形维数值介于2.1785~2.3192之间,土壤体积分形维数表现为油松×落叶松>落叶松、油松×山杏(P>0.5)>沙棘×柠条、山杏×柠条、沙棘(P>0.5)>油松、柠条、山杏(P>0.5)>裸地。土壤体积分形维数与黏粒、碱解氮、速效钾、速效磷呈显著正相关(P<0.5),与砂粒呈显著负相关(P<0.5),与粉粒、有机质无明显相关性。不同人工林养分评价结果与分形维数差异不显著。研究区人工林对土壤结构和养分改良效果显著,油松×落叶松、油松×山杏混交林及落叶松纯林对于土壤结构和养分影响较大,改良效果最佳。

The fractal characteristics of soil particles of different plantations and their relationship with soil structure and nutrients in loess hilly and gully region of Qingshuihe county were studied, and the effects of different plantations on soil structure and nutrients in Qingshuihe county were compared with the fractal dimension of soil volume, so as to understand the soil structure and nutrient status of different plantations and provide reference for the selection of local artificial forests and rational management. Nine kinds of plantations in the study area were selected as the research objects, and the woodland free land was used as the control. The particle size distribution of soil was measured by laser particle size analyzer and the fractal dimension was calculated. The nutrient status was evaluated by single index, and the correlation between the fractal dimension of soil and nutrient was analyzed. The fractal dimension of soil volume of plantations in the study area was between 2.1785-2.3192, and the fractal dimension of soil volume was as follows:Pinus tabuliformis Carr.×Larix gmelinii(Rupr.) Kuzen. > Larix gmelinii(Rupr.) Kuzen. and PinPinus tabuliformis Carr. × Armeniaca sibirica(L.) Lam.(P>0.5) > Hippophae rhamnoides Linn. × Caragana korshinskii Kom., Armeniaca sibirica(L.) Lam. × Caragana korshinskii Kom., Hippophae rhamnoides Linn.(P>0.5) > Pinus tabuliformis Carr.,Caragana korshinskii Kom., Armeniaca sibirica(L.) Lam.(P>0.5) > bare land. The fractal dimension of soil volume was positively correlated with clay, alkali-hydrolyzable nitrogen, available potassium and available phosphorus(P<0.5),and negatively correlated with sand(P<0.5), but not significantly correlated with silt and organic matter. There was no significant difference between nutrient evaluation results and fractal dimension of different plantations. The plantations in the study area had remarkable effects for improving soil structure and nutrients, and Pinus tabuliformis Carr.×Larix gmelinii(Rupr.) Kuzen., PinPinus tabuliformis Carr. × Armeniaca sibirica(L.) Lam. mixed forest and Larix gmelinii(Rupr.) Kuzen. pure forest had great impacts on soil structure and nutrients, and the improvement effect was the best.