Thảm thực vật thủy sản ngập nước (SAV) hình thành một thành phần quan trọng của hệ sinh thái sông hồ cạn và. Này chất dinh dưỡng chu kỳ, ổn định dòng chảy, tăng cường sự rõ ràng nước, ảnh hưởng đến sản xuất ban đầu, và bảo vệ bờ biển từ xói mòn (Carr et al 1997, Văn Nes et al. 2003). Hơn nữa, nó cung cấp một nguồn lương thực quan trọng cho các loài chim di cư. Thiên nga Bewick của (Cygnus columbianus bewickii), ví dụ, thức ăn các loại củ Potamogeton pectinatus vào mùa thu ở. | 16 A Conceptual Framework for Integrating a Simulation Model of Plant Biomass for Vallisneria spiralis L. with Remote Sensing and a Geographical Information System Guofeng Wu Jan de Leeuw Elly P. H. Best Jeb Barzen Valentijn Venus James Burnham Yaolin Liu and Weitao Ji INTRODUCTION Submerged aquatic vegetation SAV forms a significant component of shallow lake and river ecosystems. This cycles nutrients stabilizes flow enhances water clarity influences primary production and protects the shores from erosion Carr et al. 1997 Van Nes et al. 2003 . Moreover it provides an important food source for migratory birds. Bewick s swans Cygnus columbianus bewickii for instance feed on the tubers of Potamogeton pectinatus in autumn in the Netherlands Jonzen et al. 2002 while in Canada Trumpeter swans Cygnus buccinator forage on the tubers of Potamogeton pectinatus during spring LaMontagne et al. 2003 . Migratory North American waterfowl species in the tribe Athyini depend heavily upon tubers produced by a variety of SAV species Korschgen 1989 and Siberian cranes Grus leucogeranus rely on the tubers of Vallisneria spiralis L. throughout the winter at Poyang Lake China Wu and Ji 2002 . Careful management of lake and river systems with SAV are therefore indispensable not only from the perspective of ecosystem health but also for the conservation of migratory bird species. Protected lake areas and backwater areas of rivers are not isolated water bodies but are parts of larger watersheds. Natural or anthropogenic changes may influence these water bodies and in turn impact the growing conditions of SAV along with the availability of food for waterfowl. These changes can often be subtle. Van Vierssen et al. 1994 for example described that SAV declined during the 1960s and 1970s in Lake Veluwe the Netherlands due to eutrophication caused by wastewater and 187 2008 by Taylor Francis Group LLC 188 Wetland and Water Resource Modeling and Assessment FIGURE Landsat TM images of .
