湿地“淹埋深-历时-频率”阈值研究的理论和方法

针对"淹埋深-历时-频率"(S, D, F)阈值研究存在的问题,根据土壤学、植物生态学、系统论、地理系统学说以及反演理论等的相关原理,系统分析了湿地(S, D, F)阈值确定的理论和方法。结果表明:在正常情况下,水饱和至地表的最大地下水埋深、湿地植物主要根系分布层下限和沉水植物分布下界淹水深分别是湿地土壤上界、湿地植被上界和湿地下界的S阈值;D阈值只能通过湿地土壤或湿地植被边界界定在水位过程线上反演,稳定湿地边界的D阈值应取与50%频率值对应的D值或D值的多年平均值,波动湿地边界的D阈值是常数;"非正常情况下"湿地的D阈值应参照湿地水文地貌分类的同一区域子类中"正常情况下"的湿地的D阈值;检验D阈值科学性的标准是利用D阈值确定的湿地水文边界必须与湿地土壤边界或湿地植被边界耦合。

Study on the theory and method for determining wetland “water stage-duration-frequency” thresholds

Aimed to get scientific "water stage-duration-frequency" (S, D, F) thresholds for wetland formation, the theory and method to determine wetland (S, D, F) thresholds were analyzed based on the related principles of pedology, plant ecology, system theory, geographic system theory, and inversion theory, etc. The result suggested that: ① Under normal circumstances, the S threshold for hydric soil formation and hydrophyte development should be determined in terms of the thickness of capillary fringe and the depth of the major portion of hydrophyte root zone in upper wetland boundary respectively; in lower wetland boundary, the S threshold should be determined at the maximum depth to which submerged plants normally grow; in a given year, the D threshold could only be inverted in stage hydrograph in terms of the altitude of wetland soil boundary or vegetation boundary; for stable wetland soil boundary or stable wetland vegetation boundary, the D threshold should only take the average value of the years, but for fluctuant wetland vegetation boundary, its D threshold is a constant. ② Under abnormal circumstances, the (S, D, F) thresholds of wetlands should refer to the (S, D, F) thresholds of wetlands "under normal circumstances" which belong to the same HGM regional subclass. ③ To test whether (S, D, F) thresholds is scientific, wetland hydrological boundary determined by the (S, D, F) thresholds must be coupled with wetland soil boundary or wetland vegetation boundary. The construction of the theory and method makes it possible for wetland scientists to study (S, D, F) thresholds of different wetland types in different regions.