黄土丘陵区坡面林-草边界土壤水分特征

Soil moisture characteristics at the boundary of forestland-grassland in hilly area of Loess Plateau.

研究了黄土高原丘陵区林-草边界上旱季和雨季土壤水分的空间分布变化特征.结果表明,旱季林地土壤水分的变异系数都小于草地,林地内各个层次土壤含水量差异不大,草地内各个层次土壤含水量差别较大;雨季林地土壤水分的变异系数都大于草地,林地内各个层次土壤含水量差别较大,而草地内各个层次土壤含水量差异不显著;林-草边界各个层次土壤水分的变异程度为弱变异或中等变异.林-草边界在旱季和雨季具有不同的影响域,旱季边界影响域为从林外0·4倍树高距离到林内0·4倍树高距离;雨季边界影响域为从林外0·4倍树高距离到林内0·8倍树高距离.因此,可将林-草景观划分为3个区草地区,即由距林缘0·4倍树高距离处向草地方向延伸;林缘区,即由林外0·4倍树高距离到林内0·4倍树高距离(旱季)或0·8倍树高距离(雨季);林地区,即由林内0·4倍树高距离(旱季)或0·8倍树高距离(雨季)处向林内方向延伸.林-草边界水平方向上3个分区的土壤水分垂直分布呈现出不同的变化规律,而且旱季的规律特征与雨季相反.

In this paper, the spatial distribution pattern of soil moisture at the boundary of forestland - grassland in hilly area of Loess Plateau was studied in dry season of June and rainy season of August 2004. The results showed that the variance coefficient of soil moisture content was smaller, and the difference of moisture content between soil layers was less significant in foresfland than in grassland in June while reversed in August. There was a weak or medium differentiation of moisture content in different soil layers at the boundary of forestland - grassland. The edge effect area at the boundary was from 2 m （0. 4 of tree height） outside forestland to 2 m inside forestland in June, and from 2 m outside forestland to 4 m （0. 8 of tree height） inside forestland in August. The forestland - grassland landscape could be divided into 3 parts, i. e., grassland area, forest edge area, and forestland area, and the vertical distribution of soil moisture in these three parts showed different traits. In June, soil moisture content increased with increasing soil depth, with a smaller increment in grassland than in forestland, but in August, it was reversed. The vertical distribution of soil moisture at forest edge area showed an in-between feature.