Forest fragment spatial distribution matters for tropical tree conservation

- Forest fragments are spatially and environmentally non-randomly distributed.
- The environment explains most patterns in fragment tree diversity and composition.
- Fragment edge, size, shape and isolation affected tree maintenance minimally.
- Fragment location is the main driver of tree species maintenance within landscapes.
- Small fragments are important as they generally represent over-exploited habitats.

Deforestation and associated forest fragmentation are main drivers of species loss across the tropics. Many studies have focused on how fragment edge effect, size, isolation and shape, affect species persistence within landscapes. Little attention has been paid to the impact of the distribution of the fragments itself on the preservation of local species pools. Here we test the importance of the spatial distribution of remaining forest fragments, relative to other fragmentation effects, on tree species diversity, composition and rarity patterns within a tropical landscape converted to rubber plantations in southern Yunnan, China. We find that the remaining forest fragments are non-randomly distributed in the landscape, with most fragments located at higher elevations, steeper slopes and shade aspects. At the same time we find that most of the observed patterns in tree diversity, composition and rarity are explained by the location of the fragments within the landscape, with very little additional impact of other fragmentation effects, even though fragmentation started more than two decades ago. We conclude that during the initial stages of land use change, the protection of forest areas along the entire environmental gradient should be a prime focus for conservation efforts as it is at this stage that most tree species can be preserved in the landscape. We also stress the importance of small forest fragments for the conservation of tree species, especially because such fragments are usually located in sites with the highest deforestation rates.