河岸带不同植被格局对表层土壤养分分布和迁移特征的影响

河流周边的人类活动干扰使得河岸带的植被类型和结构发生了巨大变化。研究选取了北京市温榆河的3个类型河岸带植被结构,从河漫滩到河道上依次为：（I）杨树林-农田、（II）火炬树林-荒草、（III）农田-荒草。通过土壤采样分析和对比研究,发现河岸带的植被格局可以显著影响土壤养分的空间分布特征和流失风险。从河漫滩到河道的方向上,河岸带植被组合I的土壤全氮、全磷、有效氮、有效磷和有机质含量均呈现降低的趋势,而土壤容重则逐渐增加。对于植被结构类型II,土壤的全氮、有效氮和有机质呈现出波动的变化;而土壤的全磷和有效磷都呈现比较平缓的变化趋势。对于植被组合III,土壤养分含量均呈现增加的趋势,土壤容重呈现降低的趋势。河岸植被模式III的下坡位荒草区域的土壤养分和有机质含量都要显著高于其上坡位的农田区域,但农田区域的土壤容重则大于荒草区域。植被结构的异质性还可以影响到河岸样带的土壤平均养分含量和容重大小。研究结果可以为退化河岸带的植被恢复和植被格局的优化设计提供参考。

Effects of Riparian Vegetation Patterns on the Distribution and Migration Characteristics of Surface Soil Nutrients

The types and patterns of riparian vegetation have changed greatly due to human activities along the Wenyu River. Three riparian vegetation patterns from the upland to the river channel along Wenyu River were chosen as the focus of this study. These vegetation patterns are (I) Populus simonii forestland-Cropland, (II) Rhus typhina forestland-Grassland and (III) Cropland-Grassland, respectively. The distributions of soil nutrients along these vegetation patterns were observed and compared. Results show that the heterogeneity of riparian vegetation structure can significantly affect the distribution characteristics of soil nutrients and the risk of soil nutrients loss. From the upland toward the river channel, the contents of soil TN (total nitrogen), TP (total phosphorus), AN (available nitrogen), AP (available phosphorus), and the content of SOM (soil organic matter) exhibit the declining trend in riparian vegetation structure I, whereas the soil bulk density (BD) shows an increase trend. The contents of TN, AN, SOM in riparian vegetation structure II fluctuate, while the contents of TP and AP are relatively stable. Soil nutrients in riparian vegetation structure III show the increase trend from the upland toward the river channel, however, the soil BD decreases in the same direction. For the vegetation structure III, the grassland soil in the lower slope has more nutrients and OM but lower BD than the cropland soil in the upper slope. The riparian vegetation structure also can affect the average contents of soil nutrients in riparian transect. A scientific reference can be provided by this paper for optimization and restoration design of riparian vegetation.