No abstract

Large tracts of tropical rainforests are being converted into intensive agricultural lands. Such anthropogenic disturbances are known to reduce species turnover across horizontal distances. But it is not known if they can also reduce species turnover across vertical distances (elevation), which have steeper climatic differences. We measured turnover in birds across horizontal and vertical sampling transects in three land-use types of Sri Lanka: protected forest, reserve buffer and intensive-agriculture, from 90 to 2100 m a.s.l. Bird turnover rates across horizontal distances were similar across all habitats, and much less than vertical turnover rates. Vertical turnover rates were not similar across habitats. Forest had higher turnover rates than the other two habitats for all bird species. Buffer and intensive-agriculture had similar turnover rates, even though buffer habitats were situated at the forest edge. Therefore, our results demonstrate the crucial importance of conserving primary forest across the full elevational range available.

1. The conversion of rainforests into agriculture resulted in massive changes in species diversity and community structure. Although the conservation of the remaining rainforests is of utmost importance, identifying and creating a biodiversity-friendly agriculture landscape is vital for preserving biodiversity and their functions.2. Biodiversity studies in agriculture have often been conducted at low elevations.In this study, we compared the functional diversity (FD), phylogenetic diversity (PD) and community structure of birds along an interacting gradient of land use (protected rainforest, reserve buffer and agriculture) and elevation (low, middle and high) in Sri Lanka. Then, we measured the compositional change by identifying how ecological traits (dietary guild, vertical strata, body mass and dispersal ability) and conservation characteristics (forest dependence and threatened status) responded to land use types.3. Elevation and land use interacted with each other to shape bird FD. Depending on the elevation, FD in agriculture was either higher or similar to forest. However, PD was similar across all elevation and land use types. Bird community structure in forest was functionally and phylogenetically clustered in comparison to agriculture.Insectivorous birds declined from forest to agriculture, and so did understorey and middle-storey birds. But frugivorous and canopy birds did not change across land use types, while nectarivores, granivores and carnivores proliferated in agriculture.Forests were dominated by birds with low dispersal abilities, but birds in agriculture had more evenly distributed dispersal abilities. About half of all the individuals in agriculture were composed of forest species, several of which were threatened. 4. Synthesis and applications. Most farmers in Sri Lanka practice agriculture on small farms (c. 2 ha) and rely on services (e.g. pest control and pollination) provided by | 1739