东部沙区表土有机质和速效养分与风沙环境关系初探

Relationship between the surface soil nutrients and aeolian environment in the eastern desert regions of China

东部沙区表土有机质、速效养分含量普遍较低。按照库布齐沙漠、毛乌素沙地、浑善达克沙地、科尔沁沙地和呼伦贝尔沙地的次序,有机质和速效K含量逐渐增大,这种分布格局与区域风沙环境性质、风沙活动方式密切相关;各沙漠/沙地内部,表土有机质和速效K含量分别与植被盖度、颗粒平均粒径、分选系数之间存在较好的相关性。速效N和速效P含量未表现出上述变化规律。可见有机质和速效K含量对风沙环境的变化较为敏感,因而其在表土中的再分配可以在一定程度上反映局地风沙环境的变化,而速效N和速效P对风沙环境的指示意义不明显。东部沙区表土有机质、速效N及速效P含量普遍高于西部沙区,而速效K含量明显偏低。

The main objective of the research is to determine the relationship between soil nutrients distribution of surface sediments and the aeolian environment in the eastern desert regions of China. Sediment samples of sand dunes with different mobility at the five deserts in theses area are collected,including Hobq Desert,Mu Us Sandy Land,Otindag Sandy Land,Horqin Sandy Land and the Hulunbuir Sandy Land. The contents of organic matter and available nutrients were tested. Analysis of their spatial characteristics and the correlation between soil nutrients and mean grain size,sorting coefficient,vegetation coverage,regional wind force and dune activity index shows that contents of organic matter and available nutrients are generally very low for all five deserts. From the west to the east,in the order of Hobq Desert,Mu Us Sandy Land,Otindag Sandy Land,Horqin Sandy Land and Hulunbuir Sandy Land,contents of organic matter and available potassium increase gradually. The low contents of organic matter and nutrients in Hobq Desert are closely associated with aeolian activities characterized by frequently alternated occurrence of wind erosion,particle transportation and deposition. Such an aeolian environment is favorable for particle sorting but unfavorable for accumulation of soil nutrients. In Hulunbuir Sandy Land,precipitation is relatively sufficient and the vegetation coverage and the background of soil nutrients are better than those of the other deserts,the strongest regional wind force results in a wind erosion process that dominates aeolian environment. Therefore,physic-chemical properties of the surface sediments are mainly determined by the regional background with high content of soil nutrients. In Mu Us,Otindag and Horqin Sandy Lands,the interlace distribution of wind erosion dominated areas with sparse vegetation and the aeolian deposition dominated areas with good vegetation cover produce a more complex regional aeolian environment than the Hobq and Hulunbuir Sandy Lands,which reduces the loss of soil nutrients. In each desert,contents of organic matter and available potassium of surface sediments are statistically correlated to local vegetation coverage,particle sorting coefficient and mean grain size to different degrees. However,available nitrogen and phosphorus contents do not exhibit correlations to local vegetation coverage,mean grain size or particle sorting coefficient. This suggests that the grain size,organic matter and available potassium content of surface sediments are sensitive to the change of aeolian environment,while available nitrogen and phosphorus cannot index the aeolian environment.