Windstorm effects on herbaceous vegetation in temperate forest ecosystems: Changes in plant functional diversity and species trait values along a disturbance severity gradient

• Published in: Forest ecology and management 2022-02, Vol.505, p.119799, Article 119799
• Main Authors: Cacciatori, Cecilia, Bacaro, Giovanni, Chećko, Ewa, Zaremba, Jakub, Szwagrzyk, Jerzy
• Format: Article
• Language: English
• Subjects: Functional divergence; Functional richness; Habitat type; Life traits; Natural disturbance; Temperate forest ecosystems
• ISSN: 0378-1127; 1872-7042
• DOI: 10.1016/j.foreco.2021.119799

•Response of functional diversity to wind disturbance depends on forest type.•Functional richness increases after wind disturbance in mixed-coniferous forests.•Species richness increases along with wind disturbance.•SLA increases along with wind disturbance, while share of stress-tolerant decreases. Catastrophic wind disturbance affects not only forest structure and regeneration, but also functional and compositional dynamics of the herbaceous layer. However, the issue of changes in functional diversity and functional trait values of the understory layer in response to wind disturbance has not been addressed so far. This study aims at investigating the patterns of variations in functional diversity, trait values and species richness of herbaceous species following wind disturbance. The study was carried out in the Piska Forest, a woodland complex in northern Poland, which was almost completely destroyed by a windstorm in 2002 and part of which was successively set aside to study the effects of natural disturbance on forest ecosystems. Vegetation surveys were conducted at 112 sample plots between 2014 and 2015. Four forest habitat types were identified and individually examined. The degree of disturbance severity was assessed as percentage of dead trees on all trees per surface unit. A set of twelve functional traits was assigned to the recorded species. Three functional diversity metrics (richness, evenness and divergence) were calculated based on the selected functional traits. We assessed the relationship between each of such metric and disturbance severity for each habitat type. The relationship between species richness and disturbance severity was also determined. We then estimated the relative importance of habitat type and disturbance severity on both functional diversity and species richness. Lastly, we examined the response of functional trait values to both disturbance severity and habitat type. Our results showed that wind disturbance effects on functional diversity are not univocal and that they strongly depend on habitat type. In fact, while in coniferous stands disturbance determined a decrease of functional divergence and left functional richness unaltered, in mixed-coniferous habitats it enhanced functional richness and did not affect functional divergence. In mixed-deciduous habitats, both functional richness and divergence decreased. In swamp habitats no major changes in functional diversity were observed. Changes in functional evenness we