Winners and losers among tree species in Xishuangbanna: which traits are most important?

Abstract

Massive human interference in natural ecosystems is resulting in a few “winners” and many “losers”. However, the drivers of this winner–loser replacement pattern remain poorly understood. The aim of the study reported here was to identify winners among the tree flora of Xishuangbanna and compare their functional traits, specific leaf area (SLA), wood density (WD), seed mass (SM) and maximum height (MH) with previously identified losers (i.e., endangered species). Fifteen native tree species were identified as winners from expert opinion, plot-based surveys of secondary forests and plotless surveys along roads. Twelve endangered tree species for which trait information could be obtained were used for comparison. Traits were compared with a Wilcoxon rank-sum test. Winners had significantly higher SLA, but lower WD. SM and MH did not differ significantly between groups. When the effects of phylogeny were removed by using phylogenetic generalized least squares, the difference in SLA became marginally insignificant. Principal component analysis resulted in two overlapping groups, showing that the selected traits were insufficient to distinguish winners and losers. Our results suggest that the “few winners, many losers” paradigm applies to trees in Xishuangbanna, with 15 species accounting for most trees in the disturbed habitats sampled.