流域湿地景观空间梯度格局及其影响因素分析

Spatial gradients of wetland landscape and their influential factors in watershed

景观空间格局研究是景观生态学的核心研究内容之一。吸取一般景观生态学的空间思想和实际工作积累,从流域尺度,研究湿地景观基本空间梯度格局及其影响因素。研究表明,流域中湿地景观具有特殊的纵向梯度、横向梯度和景观内部结构特征,它们构成了流域湿地景观空间结构的主体,在维护流域整体景观结构和生态功能方面发挥重要作用。自然和人为因素都会影响流域湿地景观的空间梯度格局,但自然因素主要影响湿地景观内部结构的复杂性,而人为因素对流域湿地景观纵向梯度、横向梯度的连续性和内部结构的多样性均产生重要影响。

Landscape spatial pattern is an important focus of research in landscape ecology. Much attention has been paid to research on patch and corridor structure for certain land use types at the local or regional scale as opposed to the spatial gradient for one natural land cover type at the watershed scale. In particular spatial gradients for wetland landscape at the watershed scale have not yet been studied. Wetlands are unique among watershed environments because they are terrestrial habitats with strong effects on and strongly affected by aquatic environments. This paper primarily addresses the particular spatial gradients of the wetland landscape within a whole watershed, based on the common spatial principles of landscape ecology and some recent practical research. Results show that the landscape pattern of wetland types within a watershed is controlled by the gradient in topography and hydrological regime. It exhibits gradient features in three aspects： the longitudinal gradient from the headwaters to the mouth of rivers, the transverse gradient considered as a cross section of the floodplain, and the internal structure as species assimilation or heterization within a patch, or the ecosystem composition in patches of landscape. The complexity and continuity of the wetland landscape in the longitudinal gradient, the transverse gradient and the internal structure within the watershed play a significant role in reducing downstream flooding, preventing erosion, maintaining channel stability and water quality, as well as providing corridors for species movement and habitats for some endangered and threatened species. However, both natural factors and human activities can affect the overall pattern of wetland gradient in a watershed. The rate of changes are determined largely by more recent human impacts such as land reclamation, river channelization, and dam construction, which have significant impacts on the longitudinal and transverse gradients and the internal structure of wetlands landscape within a watershed whereas natural factors such as dynamic channel changes and flooding only affect the internal structure of the wetland landscape.