As part of research on the biodiversity of forest communities, researchers of the ELKH Centre for Ecological Research (CER) have sought answers to the question of how to preserve forest life as much as possible, even when forests are used for commercial purposes. The researchers examined 35 forest stands in the Őrség National Park, where data were collected from 11 groups of organisms simultaneously, and detailed surveys were conducted on the structure and species composition of the selected forest stands. A study summarizing the latest research findings was published in the international multidisciplinary journal Science of the Total Environment.

What makes a forest rich in wildlife? Are the same factors important for different groups of plants, animals, and fungi? To what extent does a forest manager have an impact on the biodiversity in their forest? Is it possible to ‘please’ many kinds of living things at once? ÖK staff looked for the answers to these questions as part of research aimed at using the findings to help conserve the biodiversity of forest communities.

The biodiversity of the Earth’s terrestrial areas is largely due to the presence of forest biocenoses, or ecological communities (organisms interacting in living habitats). According to a 2018 study on biodiversity by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services, just as in other parts of the world, the biodiversity of Europe’s forests is declining rapidly and progressively, making it an urgent task to stop the trend. The idea has formed to significantly increase the amount of forest withdrawn from farming purposes in order to protect forest communities. There is a genuine need for forest reserves that are left alone, as only in these places can the natural processes of forests truly prevail. However, in parallel, the demand for timber – firewood and building timber – is growing, which means it is not feasible to abandon commercial forestry in the vast majority of forests.

“The question to be solved is how to preserve the wildlife of forests as much as possible, even if the forests are being used for economic purposes,” says Flóra Tinya, a researcher at the Centre for Ecological Research. “To do this and as a first step, we need to explore what the key factors are in forests whose preservation is vital for various living things. The next step is to develop sustainable silvicultural systems that are able to ensure that sustainability requirements are met and that natural structures are maintained at all stages of the economic process.”

The forests of the Őrség National Park provided an ideal location for the research, as the traditional land use means that the national park contains forests with a very diverse structure and tree species composition within a relatively small area, i.e. under similar climatic conditions. Of these areas, the researchers selected 35 forest stands where they assessed a wide range of forest features and collected data on forest life. Though the environmental needs of a group of organisms – such as birds or forest undergrowth – have already been observed in a number of different studies, these have been very limited in terms of the possibility to generalize to entire forest communities. The novelty of the present work lies in the fact that – with the involvement of several specialist researchers – data were collected simultaneously from 11 groups of organisms, from herbaceous undergrowth to tree regeneration, mosses, lichens, fungi, various arthropod groups and birds. To explore what affects the species richness and composition of these groups of organisms, the researchers conducted detailed surveys of the tree structure and species composition of the designated forests. They also examined the microclimatic conditions on the forest floor – light, temperature, humidity – in terms of the physical and chemical characteristics of the dry grass and soil, and the landscape environment and past land use of forest stands.

The researchers found that, although it was not possible to identify any two groups of organisms with exactly the same needs, some key factors could be identified that can help ensure the survival of many forest organisms simultaneously with different ways and means. In the course of the research, the ecologists found that the most decisive factor for forest biodiversity is the presence of certain structural elements of the forest stand, such as shrub level and deadwood. While in conventional forest management, shrubs and dead trees are often removed from the forest, the scientific findings show that not doing so significantly increases the diversity of forest communities. For birds, for example, the shrub layer serves as a hiding place, nesting and feeding ground, while for spiders it increases the number of structural elements suitable for the construction of webs, and the cool-humid environment it provides also offers a favorable habitat for various fungi, mosses and lichens. Dead trees are associated with very rich degrading fungal communities and provide a habitat and feeding ground for a multitude of beetles and other insects. These arthropods living in the dead tree then provide food for other living things – insects, birds, small mammals. The ridges of dead trees also provide hiding places and breeding grounds for numerous birds and bats. In the same way, the preservation of trees that are particularly large and irregular in shape is also key in providing a variety of habitats. For many living things, the existence of a spatially varied, but mostly cool, humid, balanced forest microclimate with smaller, bright spots breaking the closed canopy here and there proved to be decisive. This means that not only closed forest species, but also plants and animals needing light and heat find suitable living conditions in these ‘light gaps’.

In addition to these structures, the species of trees that make up the forest also proved to be of paramount importance in the research. In forest types rich in tree species, many groups of organisms occur with higher species richness, as each tree species can feed different specialist herbivores, different fungal species are attached to their roots, and they provide different microhabitats for forest organisms due to their different size, structure and translucence.

The research also found that forests with different structures and tree species compositions were home to communities with different compositions, i.e., not all species could be conserved within a single forest type. This means that ensuring diversity is not only important within a single forest stand, but it is also necessary to preserve diverse forests on a larger scale.

“Based on our results, all the factors that forest managers can do a lot to preserve have proved to be key to forest communities,” says Flóra Tinya. “Mixed tree species, shrubs, dead trees and large or irregular trees can be left behind in conventional forest management in some parts of the forest. This enables them to provide local shelter for many living things. However, the so-called perennial forest mode, which maintains continuous forest cover, may be the most suitable for the long-term provision of a cool and humid and subtly varied forest microclimate. In this process, the trees are always removed in small areas and patches at a time, and no large, woodless cutting area is created. In this way, forest conditions are maintained throughout the management cycle and the preservation of forest communities can be ensured in addition to timber production.”