Browsing by Subject "vertical vegetation structure"

Rapid changes in the environment due to human actions have highlighted the need to better understand the functioning of ecosystems and the underlying mechanisms. Biodiversity and ecosystem functioning (hereafter, BEF) research has mainly concentrated on studying the effects of biodiversity on ecosystem functioning in experiments using grassland species. Moreover, the focus of these studies has been in determining how a single ecosystem process (e.g. productivity) is affected by the changes of biodiversity. Evaluating how the forest ecosystems’ successional gradient and species functional traits are related to each other still remains a major challenge for ecologists. The aim of this study was to find out the relations between different forest successional stages and plant species functional traits and if there were traits that were favoured along the successional gradient. This was investigated by using a direct plant species trait approach called the fourth-corner method. Also, the vertical vegetation structure of the successional stages was studied. The field measurements were conducted in 31 study sites in the southern boeal vegetation zone during summer 2011. The study sites were divided into three groups according to their successional stage and time since last management activities. Ten of the sites were young forests stands with normal management activities; eleven were mature stands that have had silvicultural activities (e.g. thinnings) within the last 25 years and the rest were also mature forest stands but without management activities since 1985. From these sites the understory vegetation was inventoried and general stand characteristics (e.g. mean height or the DBH of the living trees) were measured. Clear patterns of trait associations with the successional stages emerged from the analysis. The young stands were characterized with species that are shade intolerant, able to expand extensively also but also have abundant production of small seeds. These traits are typical for so-called pioneer species. Species traits associated with the mature, recently managed forests were chameaphytes with erect leafy stems and had a scarce seed production. For the mature nonrecently managed stands, a positive correlation was found for shade tolerant species. Species abundant in these stands had significantly longer seeds that were mainly dispersed by ants. Species occurring in these stands had also a semi-abundant seed production. The vertical vegetation structure showed, that the vegetation structure of both mature stands was similar and that the management activities could affect the natural successional trajectories. The results showed that the fourth-corner method could indeed give insight on which plant species functional traits are affected by environmental factors (such as forest succession or management activities). With this method it is possible for example to identify traits associated with valuable forest stands and practice forest management activities targeted in preserving the ecosystems’ key functions.