生态修复区植物群落土壤粒径的分维特征

Fractal dimension characteristics of soil particle size under different plant communities in ecological restoration area

土壤粒径分布及其分维特征是反映土壤质地与肥力的重要指标。本文采用土壤分形学理论与方法,研究了多伦县防风固沙区生态修复植物群落下土壤颗粒的分形维数及其在土壤剖面上的变化规律。结果表明:(1)生态修复区不同植物群落下的土壤粒径分布特征不同,其分形维数在1.962~2.260,依次为:荒草地<柠条林<白桦林<杨树林<樟子松林<黄柳和旱柳混交林<榆树林<山杏林。(2)分形维数与不同粒级含量的相关性具有明显差异,其中分形维数与<0.002、0.002~0.1 mm粒径含量呈显著正相关,与0.25~0.5 mm粒径含量呈显著负相关,与0.1~0.25、0.5~2 mm的粒径含量相关性不明显。(3)研究区0~20 cm土壤的分形维数较大,浅层土壤得到较好的改善,20 cm以下深层土壤改良的效果并不明显。本研究说明,多伦县防风固沙区经过十几年的生态修复,不同生态修复植物群落下土壤粒径分布具有不同特点,与未修复的荒草地相比分形维数偏大,土壤质地有所改善。

Soil particle size distribution and fractal dimension characteristics are important indicators of soil texture and fertility. This paper applied soil fractal theory and method to study fractal dimension of soil particles in the restored plant communities in a windprevention and sandfixation area in Duolun County, Inner Mongolia, as well as change patterns of soil particles in soil profile. Results showed that： （1） Soils under different plant communities had different particle size distribution characteristics, with fractal dimension ranging between 1.962-2.260. The fractal dimensions were in an ascending order in plant communities as unused grassland, Caragana microphylla forest, Betula platyphylla forest, poplar forest, Pinus sylvestris var. mongolica forest, mixed forest of Salix gordejevii and Salix matsudana, elm forest and Prunus sibirica forest. （2） The correlation between fractal dimension and the contents of different particle sizes showed significant difference. Fractal dimension had a significant positive correlation with the content of particle size 〈0.002 and 0.002-0.1 mm, a significant negative correlation with the content of particle size 0.25-0.5 mm, and no significant correlation with the content of particle size 0.1-0.25 and 0.5-2 mm. （3） Soil at depth of 0-20 cm in the study area had large fractal dimension, indicating that shallow soil texture had greatly improved; however, deep soil below 20 cm didn’t show obvious improvement. The study suggested that after a dozen years of ecological restoration in Duolun County’s windprevention and sandfixation area, the soil under different plant communities had different particle size distribution characteristics and larger fractal dimension compared to the unrestored grassland, indicating slight improvement in soil texture.