Piper aduncum fallows in the lowlands of Papua New Guinea

Abstract

rimary forest covers about 75% of Papua New Guinea. Every year about 200,000 ha are cleared for commercial operations, including logging, plantations, and subsistence agriculture. The latter mainly takes the form of shifting cultivation. In many parts of the humid lowlands, secondary fallow vegetation is dominated by the shrub Piper aduncum L (see color plate 20). It is not known exactly when and how P. aduncum invaded Papua New Guinea from its native Central America, but it was first recorded in the mid 1930s (Hartemink 2001). The invasion has been aggressive and it has spread in a similar fashion to Chromolaena odorata, which was introduced to Asia in the late 19th century. P. aduncum was first described by Linnaeus in 1753. It is common throughout Central America and is also found in Suriname, Cuba, Trinidad and Tobago, southern Florida, and Jamaica. It was introduced in 1860 to the botanical garden of Bogor, in Indonesia, and has naturalized in many parts of Malaysia (Chew 1972). In the Pacific, P. aduncum can be found in Fiji, but not in Hawaii. Australia has listed it as an unwanted weed species (Waterhouse and Mitchell 1998). P. aduncum is a monoecious shrub or slender tree that grows up to eight meters tall. It has ovate and petioled leaves up to 16 cm long, and its flowers are arranged in a dense spiral (see Figure 16-1). It is commonly found along roadsides and in cleared forest areas on well-drained soils, but is never found in mature vegetation. P. aduncum has very small seeds that are dispersed by the wind, birds, and fruit bats. It withstands coppicing, but burning seems to be detrimental. It can be effectively controlled by hand cutting (Henty and Pritchard 1988). Throughout the neotropics, P. aduncum extracts are used as folk medicine; and it is mentioned in several ethnopharmalogical databases. It is avoided by livestock (Waterhouse and Mitchell 1998). It is possible that seeds of P. aduncum were deliberately imported to Papua New Guinea, or that it hopped across the border from West Papua (Irian Jaya) (Rogers and Hartemink 2000). Whatever its means of arrival, P. aduncum can now be found in many parts of the humid lowlands of Papua New Guinea, whereas 20 or 30 years ago, it was absent (Bourke 1997). It is widespread in the Morobe and Madang provinces at altitudes up to 600 m above sea level (asl), and it is also found in the highlands up to altitudes of 1,800 m asl. It often grows in monospecific stands on steep hill slopes (Kidd 1997). The stems of P. aduncum are used for firewood, fence posts, or supporting sticks for yams (Dioscorea sp.). In some areas it is even used for building material, but the wood rots quickly. In some coastal villages of Papua New Guinea, the bark or leaves