The effect of harvesting and flooding on nutrient cycling and retention in Cyperus papyrus wetlands

Abstract

Cyperus papryus L. is a fast-growing sedge that can grow to lengths of 5 meter and dominates the vegetation in many wetlands from the Middle East, through eastern and central Africa to the south of that continent. Papyrus wetlands traditionally have provided important ecosystem services to millions of people through provisioning of water, fish, other foods and medicines, and materials for a wide range of uses such as construction, utensils and others. Papyrus wetlands are also important because of their regulating and cultural ecosystem services and their biodiversity. In the landscape they are buffers for water and nutrients, provide habitat for fish, birds and other wildlife, and have been an integral part of the livelihoods and culture of African wetland communities for ages. African wetlands are under pressure from human activities and economic development. As a result, the total area of these ecosystems is declining. With a growing African population and demand for food production, protecting wetlands and combining increased agricultural production with conservation of the ecological integrity of wetlands is urgent. Eutrophication is of growing concern in the region and papyrus wetlands are known to reduce nitrogen (N) and phosphorus (P) loads to downstream water bodies. An increased ability to quantify the role of wetlands in N and P retention and a better understanding of the role of the different processes contributing to N and P retention is needed. To improve understanding of the processes contributing to N and P retention in papyrus wetlands and to evaluate the effects of different management regimes (particularly changes in water regime, and vegetation harvesting), the main objective of this thesis is to develop a dynamic simulation model for nutrient cycling and retention in rooted papyrus wetlands. Chapter 1 of this thesis presents the background on papyrus wetlands in Africa and their ecosystem services, and briefly introduces the thesis chapters and their objectives.