黄土丘陵沟壑区景观格局对流域侵蚀产沙过程的影响——斑块类型水平

在黄土丘陵沟壑区,景观格局对侵蚀产沙过程有着复杂的影响,且与尺度密切相关。选取河口-龙门区间内42个水文站控制流域为研究对象,以侵蚀模数、输沙模数和泥沙输移比作为表征各流域单元内土壤侵蚀、产沙及泥沙输移过程的特征指标,运用景观指数和CCA排序,系统分析了斑块类型水平上景观格局对流域侵蚀产沙过程的影响。结果表明:流域侵蚀产沙及泥沙输移过程中,空间分异特征随景观类型不同而异;对于不同用地类型,影响"过程"空间分异的景观格局指标不同,显著影响流域侵蚀产沙及泥沙输移过程的景观指数有草地平均斑块面积(AREA_MN3)、居民建设用地景观面积百分比(PLAND5)、居民建设用地和其它类型用地景观的斑块密度(PD5和PD6),其中斑块密度(PD)是影响流域侵蚀产沙及泥沙输移过程的共性指标;草地、居民建设用地、其它类型用地的景观格局特征对"过程"变化的解释程度要高于其它景观类型。开展景观格局与生态过程关系研究时,不仅需要考虑景观格局的整体效应,更应关注单一景观类型及其格局特征对一些生态过程的指示意义。

Effects of landscape pattern on watershed soil erosion and sediment delivery in hilly and gully region of the Loess Plateau of China: patch class-level

Landscape pattern has a significant and complex effect on soil erosion and sediment delivery in the loess hilly and gully region. This scale dependent effect is a central problem to be solved in landscape ecology. In this study, the watersheds from Hekou to Longmen(Helong section), where 42 hydrological stations located, were selceted as the study area in the loess hilly and gully region. Specially, soil erosion modulus, sediment transport modulus and sediment delivery ratio were used as the indices to represent features of soil erosion and sediment delivery process in each watershed. Effects of landscape pattern on soil erosion and sediment delivery process were systematically analyzed based on landscape metrics and canonical correspondence analysis (CCA) at patch-class level. The results indicated that the spatial variation of soil erosion and sediment process has a close relationship with patch classes. Landscape metrics affecting the spatial variation of soil erosion and sediment processes varies with land use categories. The landscape metrics, which had significant influences on soil erosion and sediment delivery, include mean patch area of grassland (AREA_MN3), percentage of landscape area of residential land (PLAND5), patch density of residential land (PD5) and patch density of other land use types (PD6). Futhermore, patch density is a landscape metrics that could impact on both soil erosion and sediment delivery. Landscape pattern characteristics of grassland, residential land, and other land use types have more significant influences on soil erosion and sediment delivery than the remaining landscape classes. This study suggested that on exploring the relationship between landscape pattern and ecological process, not only the impacts of the whole landscape pattern on ecological process should be examined, but also the effects of each single class and their patterns in the landscape on eological process should be considered.