腾格里沙漠草方格固沙林土壤颗粒组成、分形维数及其对土壤性质的影响

Soil particle composition,fractal dimension and their effects on soil properties following sand-binding revegetation within straw checkerboard in Tengger Desert,China

为了明确草方格人工固沙造林植被恢复过程中土壤颗粒组成、分形维数及对土壤理化性质的影响,以腾格里沙漠东南缘2016年(1 a)、2013年(4 a)和1987年(30 a)草方格固沙林为研究样地,以周围流动沙地为对照(CK),研究了草方格固沙造林后植被恢复过程中土壤颗粒组成、分形维数及与土壤理化性质的作用关系.结果表明:100～250、250～500μm土壤颗粒含量较高,分别为42.5%～80.1%、12.5%～42.2%; 50～100μm土壤颗粒含量居中,为0.2%～20.8%;<2和2～50μm的土壤颗粒含量次之,分别在0～1. 3%和0～22. 7%;而500～1000μm的土壤颗粒含量较低,在0.3%以下.<2和2～50μm土壤颗粒仅在30 a固沙林有分布; 50～100μm土壤颗粒分布为30 a最高,4 a和1 a居中,而CK最低; 100～250μm土壤颗粒分布依次为4 a>1 a>CK>30 a; 250～500μm土壤颗粒分布为CK>1 a>4 a>30 a;但500～1000μm土壤颗粒在各样地分布均较少,且不同样地之间无显著差异.研究区土壤颗粒分形维数为0.54～2.59,并且不同样地间存在显著差异,表现为30 a最高,4 a与1 a居中,而CK最低.土壤颗粒分形维数与土壤黏粒、粉粒、极细砂粒含量呈极显著正相关,而与土壤中砂粒呈极显著负相关.土壤颗粒分形维数与土壤电导率、有机碳、全氮和碳氮比均呈极显著正相关,而与土壤p H和含水量无相关性.土壤中<2、2～50、50～100μm颗粒与土壤电导率、有机碳、全氮和碳氮比均呈极显著正相关,而250～500μm土壤颗粒与上述4个土壤指标和土壤含水量呈显著负相关.500～1000μm土壤颗粒与土壤含水量亦呈极显著负相关.在腾格里沙漠东南缘地区利用草方格进行人工固沙植被建设,可有效促进土壤颗粒细粒化,长期演变导致土壤黏粒和粉粒及土壤分形维数显著增加,促使土壤有机碳和全氮含量提高,有利于土壤理化性质改善和促进沙漠化治理.

This study aims to elucidate the effects of soil particle composition and fractal dimension on soil physical and chemical properties following sand-binding revegetation within straw checkerboard in south-eastern Tengger Desert. Three afforested plantations in the year of 2016( i. e.,1year),2013( i.e.,4 years) and 1987( i.e.,30 years) were selected as study sites,with the adjacent mobile sand land as control( CK). We measured soil particle composition,soil fractal dimension,and the changes of soil physical and chemical properties. The relationship between soil particle composition,soil fractal dimension,and soil properties was analyzed. The results showed that contents of soil particle with the size of both 100-250 μm and 250-500 μm were greater than that of 50-100 μm,ranging from 42.5% to 80.1% and from 12.5% to 42.2% relative to that ranging from 0.2% to 20.8%. Contents of soil particle with the size of <2 μm and 2-50 μm were remarkably lower than that of 100-250 μm,250-500 μm and 50-100 μm,ranging from 0 to 1.3% and from 0 to 22.7%,respectively. However,contents of soil particle at the size of 500-1000 μm was the lowest occupying <0.3% of soil particle composition. Soil particle with the size of < 2 μm and2-50 μm were found in the 30-year sites only. Soil particle distribution at the size of 50-100 μm,100-250 μm,and 250-500 μm followed the order of 30 a>1 a>4 a>CK,4 a>1 a>CK>30 a,and CK>1 a>4 a> 30 a,respectively. Soil particle with the size of 500-1000 μm occupied little of soil particle composition,with no significant difference between each site. The fractal dimension of soil particles ranged from 0.54 to 2.59. There was significantly greater soil fractal dimension in 30 a in comparison to 4 a,1 a and CK,with the intermediate values in 4 a and 1 a,and the lowest values in CK. There was a significantly positive correlation of fractal dimension of soil particles with soil particle content of clay,silt,very fine sand,and a significantly negative correlation of fractal dimension of soil particles with soil particle content of medium sand. Fractal dimension of soil particles was positively correlated with soil electrical conductivity,organic carbon,total nitrogen,and carbon-nitrogen ratio,but with no correlation with soil p H and soil water content. Soil particle content at the size of <2 μm,2-50 μm,and 50-100 μm had a significant positive correlation with soil electrical conductivity,organic carbon,total nitrogen,and carbon-nitrogen ratio,whereas soil particle content at the size of 250-500 μm had a negative correlation with the former four soil indices and soil water content. In addition,there was a significant negative correlation of soil particle content at the size of 500-1000 μm with soil water content. It was concluded that the sand-binding revegetation within straw checkerboard in Tengger Desert could facilitate the fine soil particles by ameliorating stressful soil conditions. Long-term succession of revegetation on mobile sand land could enhance soil clay and silt content as well as soil fractal dimension,thus be beneficial for the improvement of soil physical and chemical properties and desertification control.