As a result of the impact of human activities, including deforestation, fragmentation and overexploitation, a few “winner” species are able to increase their population densities and/or geographical ranges, while many “loser” species suffer reduced densities and ranges and may even become extinct .Accumulating evidence shows that the “few winners and many losers” paradigm has become the emerging prospect for tropical forest biodiversity. Researchers from Center for Integrative Conservation of Xishuangbanna Tropical Botanical Garden (XTBG) conducted a study to assess why some tree species are winners and some losers in Xishuangbanna.

The researchers attempted to find the winners of native tree species in Xishuangbanna. They also wanted to see if the winner species differ from losers in four key functional traits (specific leaf area, wood density, seed mass and maximum height) and whether the differences persist when the effects of phylogeny were removed.

They researchers defined a winner tree species as one that is common in human-disturbed habitats and has therefore benefitted by the land-use changes of the last few decades. A loser, in contrast, is a plant species that grows only in habitats that have not been seriously disturbed by people and has consequently declined as such habitats have become restricted in recent decades. They selected 15 winner species that were not only common in their samples but also widespread in disturbed habitats in Xishuangbanna. They then selected 12 loser species from the 69 tree species classified as Endangered or Critically Endangered in a recent (2012–2014) assessment of the status of all angiosperms in Xishuangbanna.

The study showed that human activities in recent decades in Xishuangbanna have favored a few tree species and harmed many, in agreement with the “few winners and many losers paradigm.” The comparison of functional traits showed that the winners had higher specific leaf area and lower wood density than the losers, while differences in seed mass and maximum height were not significant. Winners tend to have large, soft foliage and lower woody density so that they can have high photosynthetic and respiratory rates allowing rapid growth. Many of the winners in the Xishuangbanna area are in the family Euphorbiaceae. The losers mostly grow in closed-canopy forests, and must germinate and establish under canopy shade.

The removal of phylogenetic effects to assure statistical independence had little effect on the differences between winners and losers. The difference in specifici leaf area became marginally insignificant, but the absolute change was small.

The study entitled “Winners and losers among tree species in Xishuangbanna: which traits are most important” has been published online in Science Bulletin.