Forest ecological heterogeneity determines contrasting relationships between crown defoliation and tree diversity

编号 010019205

推送时间 20190624

研究领域 森林生态 

年份 2019 

类型 期刊 

语种 英语

标题 Forest ecological heterogeneity determines contrasting relationships between crown defoliation and tree diversity

来源期刊 Forest Ecology and Management

期 第192期

发表时间 20190915

关键词 Cluster analysis;  Defoliation;  Fagus sylvatica;  ICP Forests;  Level I survey;  Picea abies;  Random forest analysis;  Resilience;  Quercus ilex;  Tree diversity; 

摘要 Tree diversity is found to enhance ecosystem functions in forests and increase the resistance and resilience of trees subjected to environmental stress, including climate change. This effect, however, can be different depending on tree species assemblages and ecological contexts. The pan-European programme for monitoring forest health (ICP Forests) considers crown defoliation as an indicator of tree vitality. Only a few studies have analysed the role of tree diversity in crown defoliation, with contrasting results. This paper analyses the relationships between defoliation and forest diversity in a country (Italy) characterised by heterogeneous bioclimatic and edaphic characteristics (from Mediterranean to Alpine) and with a wide range of forest tree species and functional groups. National-scale results show that defoliation increased in more diverse forest stands. This result can be explained by the fact that the tree mixtures reflect varying ecological conditions in heterogeneous environments. The most relevant factors that explain tree defoliation at the national level, investigated through random forest analysis, were the geographic position, tree species identity and forest stand age and structure. Cluster analysis was applied to identify homogeneous groups of plots based on their ecological and vegetation features. Four clusters were selected. Within each homogeneous cluster, the crown defoliation of the tree species showed different and contrasting patterns, changing their relationships with diversity over time. A beneficial role of diversity on defoliation (i.e. decrease of defoliation) has been observed in Quercus ilex, growing in Mediterranean conditions, and Picea abies in Alpine areas after dry periods. In the latter species, drought led to a greater increase in defoliation in monospecific than in mixed stands, suggesting the stabilising role of tree diversity.

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