雅鲁藏布江山南宽谷风沙化土地土壤养分和粒度特征

Abstract

在雅鲁藏布江山南宽谷区,选择流动沙地、平缓沙砾地、半固定沙地、固定沙地和覆沙河滩地等类型样地,研究了不同深度(0-10 cm、10-20 cm和20-40 cm)土壤层的养分状况和粒度特征,探讨了风沙运动对土壤粒度组成和养分含量的影响。结果表明: 1) 风沙化土地土壤pH值呈中性、碱性和强碱性,土壤有机质和全氮含量均很低,但全磷和全钾均很高。土壤粒度组成表现为砂粒含量(53.83%-95.93%)> 粉粒(3.3%-40.5%)> 粘粒(0.77%-5.68%)。2) 粘粒和粉粒含量均以覆沙河滩地(分别为4.02%和27.95%)最大、半固定沙地(分别为1.35%和5.27%)最小。粘粒含量表现为覆沙河滩地> 固定沙地(2.98%)> 河滩流动沙地(2.89%)> 平缓沙砾地(1.69%)> 河岸流动沙地(1.54%)> 山坡流动沙地(1.49%)> 半固定沙地。不同类型沙地粉粒含量的大小顺序与粘粒含量相似,仅在山坡流动沙地和河岸流动沙地的大小顺序有所差别。砂粒含量以半固定沙地(为93.40%)最大、覆沙河滩地最小(68.05%)。不同类型沙地的砂粒含量与粉粒含量的大小顺序正好相反。3) 土壤养分含量与粘粒、粉粒、极细砂粒和细砂粒等细沙物质的相关性较强,与中砂粒、粗砂粒和极粗砂粒等粗沙物质呈负相关或相关性较弱。其中,粘粒和极细砂粒含量的增加对土壤养分的增加贡献较大。流动沙丘随风沙运动而不断往复摆动的现象和土壤细颗粒的迁移和损失,对不同类型沙地和沙丘部位的土壤养分状况及其再分配过程产生较大影响。;We conducted a case study to examine the soil nutrients content and grain size fraction of different aeolian sandy land types in the Shannan wide valley area, middle reaches of the Yarlung Zangbo River by choosing moving sandy land, flat sandy gravel land, semi-fixed sandy land, fixed sandy land and sandy land on flood plain as sample plots. The mechanism how aeolian sand movement affects soil grain size fraction and nutrients content of aeolian sandy land was discussed based on field sand movement observation and wind velocity and direction data from 1980 to 2006 from the Lhasa Airport meteorological station. The results showed that 1) The soil pH value of aeolian sandy land in the study area was neutral, alkaline or strong alkaline, and soil organic matter (SOM) and total nitrogen (TN) content were rather low, whereas total phosphorus (TP) and total potassium (TK) were very high. The soil grain size fraction followed the order of sand content (53.83%-95.93%)> silt content (3.3%-40.5%)> clay content (0.77%-5.68%), and the clay and silt content both presented rather low. 2) The clay and silt content was highest in sandy land on flood plain (4.02% and 27.95%, respectively), whereas that was lowest in semi-fixed sandy land (1.35% and 5.27%, respectively). The clay content in different aeolian sandy land types followed the order of sandy land on flood plain> fixed sandy land (2.98%) > moving sandy land on flood plain (2.89%)> flat sandy gravel land (1.69%)> moving sandy land on river bank (1.54%) > moving sandy land on hill-slope (1.49%) > semi-fixed sandy land. The order of silt content in different aeolian sandy land types was similar with that of clay content except for moving sandy land on river bank and moving sandy land on hill-slope. The sand content was highest in semi-fixed sandy land (93.40%), whereas it was lowest in sandy land on flood plain (68.05%), and the order of sand content in different aeolian sandy land types was just in contrast to that of silt content. 3) The correlation between different soil nutrients and the content of clay, silt, very fine sand, fine sand was strong, whereas the correlation was negative or weak between different soil nutrients and the content of medium sand, coarse sand, very coarse sand. The clay and fine sand content made larger contribution to the soil nutrients content. The aeolian sand movement, which caused the continuous swing of moving sand dunes and the migration and loss of the finer sand particles, affected the soil nutrients content and their redistribution process for different aeolian sandy land types greatly. The purpose of this study is to characterize the soil nutrients content and grain size fraction of different aeolian sandy land types, and to provide a scientific basis for the ongoing vegetation restoration that is being carried out for aeolian sandy land control.