湿地边界确定的理论、方法与案例

在分析目前关于湿地边界标准的主观规定性及其原因的基础上,认为:在湿地形成过程中的一些机理问题还没有弄清楚的情况下,可用黑箱方法来确定湿地的边界。在分析陆地系统与水体系统结构差异的基础上,确定湿地下界应为有根植物分布的下限。基于土壤诊断层是各种自然地理要素长期综合作用结果这一地理学论断,将土壤诊断层在湿地边界处的尖灭现象与系统论的“黑箱”方法相结合,论述了利用土壤诊断层尖灭点作为湿地上界在理论上的科学性。案例研究表明,利用这两个标准来确定湿地的上、下边界在实践上是可行的,研究区陆地土壤诊断层尖灭线海拔高程为55.74m,最大水平误差小于1m,最大垂直误差小于4cm。基于湿地边界标准的湿地的定义应为:湿地是陆地和水体之间的过渡带,是由于地表淹水/土壤水饱和而形成的一种隐域性自然综合体,其上界位于陆地土壤诊断层的尖灭点处,其下界是有根植物下界。

Theory, Method and Case of Wetland Boundary Determination

It is suggested that the black box method could be applied to wetland boundary determination under the condition that the mechanisms of wetland formation have not been fully understood based on the analysis on the subjectivity of current criteria for wetland boundary and its causes. The lower hmit of the distribution of rooted plants was regarded as the lower boundary criteria of wetlands in terms of the differences in system construction of aquatic habitats, wetlands and uplands. The scientific significance to use the thinning-out point of soil diagnostic horizon as the wetland upper boundary was discussed in theory according to the fact that soil diagnostic horizon results from long-term integrated interaction of all envimmnental elements. Case study indicated that it is feasible to use the lower limit of rooted plants and the thinning-out point of soft diagnostic horizon to identify wetland lower and upper boundaries. In the study area, the thinning-out line of albic horizon is coincident with the 55.74 m contour line, and the maximum horizon error was less than lm and the maximum vertical error less than 0.04 m. Therefore, the wetland boundary can be redefined, namely, wetland is a transition zone between uplands and deepwater habitats, it is a kind of azonal complex resulted from inundated/saturated by water, its lower boundary lies at the lower limit of rooted plants, and the upper boundary lies at the thinning-out line of upland soil diagnostic horizon.