Homogenization of Temperate Mixed Deciduous Forests in Białowieża Forest: Similar Communities Are Becoming More Similar

Many studies show the significant impact of direct and indirect human activity on the functioning of terrestrial ecosystems, including forests. The increase in the number of invasive species, changes caused by climate change, or eutrophication of habitats resulting from air pollution can irrevocably affect biodiversity, species composition, or species interactions. Many of these effects cannot be seen in commercial forests due to the significant impact of direct human use of the forest and the high degree of transformation of forest ecosystems. In this work, we ask: how have forest communities changed over the past 70 years? What was the reason for these changes? To answer the above questions, we conducted research on repeated observations in the core area of the Białowieża National Park, which is characterized by one of the highest degrees of naturalness in Europe, where ecological processes have occurred without direct human intervention since the last glaciation. Studies have shown directional changes in species composition and biotic homogenization of three forest communities. Directional changes were found to be associated with both eutrophication of habitats as well as with changes in humidity and temperature. However, the observed changes in species composition were opposite to the hypotheses based on the observed global change. In contrast, changes in the species composition of the stand and the ability to shade and buffer the temperature and humidity under the canopy caused changes in the species composition of forest communities. In the mixed deciduous forest, homogenization occurred along with the simultaneous change of species composition of forest communities. This was caused by an increase in fertility caused by increased nitrogen deposition and changes in environmental conditions prevailing under the canopy of trees, which, however, were caused by changes in the species composition of the stand

Species Identity of Large Trees Affects the Composition and the Spatial Structure of Adjacent Trees

Large trees are keystone structures for the functioning and maintenance of the biological diversity of wooded landscapes. Thus, we need a better understanding of large-tree–other-tree interactions and their effects on the diversity and spatial structure of the surrounding trees. We studied these interactions in the core of the Białowieża Primeval Forest—Europe’s best-preserved temperate forest ecosystem, characterized by high abundance of ancient trees. We measured diameter and bark thickness of the monumental trees of Acer platanoides L., Carpinus betulus L., Picea abies L. H. Karst, Quercus robur L., and Tilia cordata Mill., as well as the diameter and distance to the monumental tree of five nearest neighbor trees. The effects of the monumental tree on arrangements of the surrounding trees were studied with the help of linear models. We revealed that the species identity of a large tree had, in the case of C. betulus and T. cordata, a significant impact on the diversity of adjacent tree groupings, their distance to the central tree, and frequency of the neighboring trees. The distance between the neighbor and the large trees increased with the increasing diameter of the central tree. Our findings reinforce the call for the protection of large old trees, regardless of their species and where they grow from the geographical or ecosystem point of view

Ecology versus society: Impacts of bark beetle infestations on biodiversity and restorativeness in protected areas of Central Europe

Protected areas worldwide are important to maintaining biodiversity and providing recreational opportunities to society. However, many protected areas are affected by unprecedented, large and severe natural disturbances, like bark beetle outbreaks. Due to the contrasting responses of different taxonomic groups to disturbance events and largely negative human perceptions of disturbed landscapes, there are conflicting opinions about the appropriate way of managing affected stands. Aligning these different objectives and understanding the responses of biodiversity and visitors' perceptions to different disturbance severities is a prerequisite for disturbance management in protected areas. We conducted multi-taxon biodiversity surveys – including meta-barcoding hyperdiverse groups such as insects and fungi – and analysed the restorativeness (i.e. the landscape's ability to renew personal cognitive capacities for forest visitors) using visitor surveys in five national parks throughout Europe. Response curves of biodiversity and restorativeness were analysed along a continuous gradient of bark beetle infestation severities in Norway spruce forests on the same study plots. Arthropod biomass and the diversity of primary producers and pollinators increased linearly with increasing disturbance severity, while overall multi-diversity (an index of the average scaled species richness per taxonomic group) did not change. Restorativeness decreased linearly with increasing disturbance severity; however, even heavily disturbed forests still had high restorativeness. In spite of the ongoing debates about disturbance management, the high biodiversity and restorativeness that accompany disturbance suggest that major goals of protected areas are not threatened by bark beetle disturbances