Cyperus Papyrus - Ecology

Ecology

Papyrus ranges from subtropical to tropical desert to wet forests, tolerating annual temperatures of 20 °C (68 °F) to 30 °C (86 °F) and a pH of 6.0 to 8.5. Papyrus flowers in late summer, and prefers full sun to partly shady conditions. Like most tropical plants, it is sensitive to frost. In the United States it has become invasive in Florida and has escaped from cultivation in Louisiana, California and Hawaii.

Papyrus sedge forms vast stands in swamps, shallow lakes, and along stream banks throughout the wetter parts of Africa, but it has become rare in the Nile Delta. In deeper waters it is the chief constituent of the floating, tangled masses of vegetation known as sudd. It also occurs in Madagascar, and some Mediterranean countries such as Sicily and the Levant.

The "feather-duster" flowering heads make ideal nesting sites for many social species of birds. As in most sedges, pollination is by wind, not insects, and the mature fruits after release are distributed by water.

In recent years papyrus has been the subject of intense ecological studies centered around its prodigious growth rate and ability to recycle nutrients. Much of this research was begun at Makerere University in Uganda in the early 1970s in the swamps on the edge of Lake Victoria and continued in Kenya (University of Nairobi) on Lake Naivasha. John Gaudet's work in Africa, supported by a National Geographic Society grant, appeared in various scientific journals over the period 1975-1991. In addition, other pioneer researchers of papyrus at Makerere in the 1970s were: Keith Thompson, T. R. Milburn, and Mike Jones. Thompson's studies of papyrus swamp development throughout Africa (1976–1985) later formed the basis for management and conservation at national levels.

Extensive research on the productive physiology of papyrus were carried out by Jones from the 1980s onward. He started his work in Uganda and later continued his research on Lake Naivasha in Kenya where he was joined by a new generation of African researchers including Frank Muthuri. Jones's latest research (2002) found that papyrus is a C4 sedge that forms highly productive monotypic stands over large areas of wetland in Africa. Jones and others measured eddy covariance from a stand of Cyperus papyrus, which formed a fringing swamp on the north-west shore of Lake Naivasha, Kenya. They determined that fluxes of CO₂ and H₂O vapor between the papyrus swamp and the atmosphere were large but variable, depending on the hydrology of the wetland system and the condition of the vegetation. These measurements, combined with simulation modeling of annual fluxes of CO₂, showed that papyrus swamps have the potential to sequester large amounts of carbon (1.6 kg C m-2 y-1) when detritus accumulates under water in anaerobic conditions, but they are a net source of carbon release to the atmosphere (1.0 kg C m-2 y-1) when water levels fall to expose detritus and rhizomes to aerobic conditions. Evapotranspiration from papyrus swamps was frequently lower than evaporation from open water surfaces and plant factors have a strong influence on the flux of water to the atmosphere.

Research on the papyrus swamp habitat has in recent years attracted the attention of many more African biologists, such as A. O. Owino, K. M. Mavuti, S. M. Muchiri and S. Njuguna. Increasingly, the value of papyrus to other species is being recognized. Papyrus swamps provide hypoxic and structural refugia for cichlids from the large predatory Nile Perch and are an important habitat for several endangered bird species.(Chapman et al. 1996; 2003; Maclean et al. 2003a; 2006).

The late 1990s also saw the rise in research on the papyrus swamps of Lake Naivasha in Kenya by teams from the English Universities of Leicester and East Anglia, notably led by David Harper. Harper's extensive recent studies on the swamps and lakes have led to a worldwide awareness of the problems facing papyrus swamps in Africa today.