using four heat-flux plates and four temperature probes. Evapotranspiration and CO 2 flux were measured using the eddy-covariance method with an Applied Technologies sonic anemometer and LI-COR 6262 infrared gas analyser mounted on 2-m towers 25 . The mean and standard error for energy flux, gross primary production and evapotranspiration at sites 3 and 4 were calculated on the basis of 30-min averages. CO 2 fluxes at sites 11, 17 and 21 were determined using eddycovariance methods and 2.5-m towers 26 . Mean values and standard errors at these sites were calculated using the daily mean CO 2 fluxes. The daily methane fluxes were integrated over the thaw period to obtain annual emission. Winter methane fluxes were assumed to be zero. CH 4 flux was measured during the thaw season, Jun-Aug, at 27 MNT and MAT sites along the Dalton Highway in 1996 using a static chamber method 30 . Air samples were taken over periods of 30-45 min and were analysed on a gas chromatograph equipped with a flame ionization detector.

Uganda is one of the most biologically diverse countries in Africa, with much of its biodiversity represented in a system of 10 national parks, 10 wildlife reserves, and 710 forest reserves, covering 33,000 km2 (14%) of the country's area. We focus on the role of the forest reserves in biodiversity conservation and describe a procedure we developed to design a national system of forest nature reserves. In the late 1980s a policy was instituted to dedicate half the area of forest reserves to sustainable timber production and the other half to environmental protection (with 20% as nature reserves). To select suitable sites, a 5‐year, US$1‐million program of biodiversity and resource assessment was undertaken, focusing on five biological indicator species groups and covering all the major forest reserves. Based on data generated by the field studies, we ranked each forest in terms of various criteria—(species richness, rarity, value for nonconsumptive uses, timber production, and importance to local communities)—and used an iterative site selection procedure to choose the most suitable combination of forests for nature reserve establishment. Our procedure maximized complementarity in representing species and habitats in reserves across the whole protected‐area system. We initially selected sites using purely biological criteria but later modified our procedure to ensure that opportunity costs and potential land‐use conflicts were minimized. Our preferred network of sites included 14 forests that, in combination with the existing national parks, would account for 96% of species represented in the country's protected areas. These 14 forests were classified as “prime” and “core” sites and were selected for the establishment of large nature reserves (averaging 100 km2). The addition of 25 smaller “secondary” forest nature reserves (averaging 32 km2) would protect more than 99% of the indicator species.

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In the late 1980s the Ugandan Government decided to dedicate a fifth (3000 sq km) of the country's 15,000‐sq‐km forest estate to management as Strict Nature Reserves (SNRs) for the protection of biodiversity. The Forest Department subsequently undertook a 5‐year programme of biological inventory and socio‐economic evaluation to select appropriate areas for designation. Sixty‐five of the country's principal forests (including five now designated as National Parks) were systematically evaluated for biodiversity, focusing on five ‘indicator’ taxa (woody plants, birds, small mammals, butterflies and large moths). A scoring system was developed to compare and rank sites according to their suitability for nature reserve establishment and 11 key sites were identified, which, when combined with the country's 10 national parks, account for more than 95 per cent of Uganda's species. In order to satisfy multiple‐use management objectives, the Man and the Biosphere model of reserve design is being applied at each forest, by designating a centrally located core area as SNR, with increasingly intensive resource use permitted towards the periphery of each reserve and adjacent rural communities.

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