How does species rarity influence the functional diversity and resilience along the successional pathway in heterogeneous karst forests?

Global climate change and human activities have increased the risk of rare
species loss due to their sensitivity to disturbances. Considering their
dominance in hyper-diverse communities, the contribution pathways and
extent of rare species loss to functional diversity and resilience should
be clarified. Therefore, we established 30 forest dynamic plots in
heterogeneous degraded karst forests and measured the plant functional
traits along the successional pathway. The correlations between trait
uniqueness and species rarity were quantified, and the effects of rare and
common species losses on functional diversity and trait networks were
simulated. The correlations between trait uniqueness and species rarity
showed rare species tended to occupy marginal functional space positions
in the mid and late successional stages. In addition, rare species mainly
supported functional redundancy in the early successional stage and
significantly impacted functional resilience. In contrast, the unique
traits supported by rare species increased along the successional pathway,
thus increasing functional diversity and resilience in the late
successional stage. This study highlights the crucial role of rare species
in the functional diversity and resilience of degraded karst forests,
warranting increased attention to rare species during biodiversity
conservation and ecological management in heterogeneous, vulnerable
ecosystems.