In recent years, a certain re-evaluation of previous functions performed by forests has been observed in many countries.
Forests traditionally used as a source of timber are increasingly serving as recreational areas. They are places for various forms of leisure activities, for example: walking, running, riding, biking, picking berries and mushrooms, hunting, and fishing. Recreational use of forests dramatically increased as a result of increased leisure time and urban infrastructure developments.
The non-productive, social functions of the forest enrich the labor market, provide a significant economic contribution to the local economy, are important for cultural development and environmental education of the public, and create profitable health and recreational conditions for the public. Contact with nature is extremely important for humans.
Recreational outdoor activity in nature contributes to the renewal and preservation of mental health as well as stress reduction.
Research showed that people’s moods and positive feelings are increasing in natural areas. Son and Ha found that increasing contact with nature serves to improve social and emotional interactions in modern society.
As our knowledge about the positive impact of the natural environment on humans grows, there are also reports that the intensity of this impact may be determined by specific features of the space. Some scientists believe that the concept of ‘natural environment is therapeutic’ cannot be accepted without some criticism.
Wyles et al. points out that elements such as garbage appear in the natural environment, the presence of which may weaken the benefits of contact with nature. It seems that there may be more such elements.
The results of the study of preferences regarding the aesthetics of forest landscape may be helpful in negative elements in nature. The research on forest landscape preferences is extensive. One of the elements of the forest landscape analysed in this type of research was dead wood. Pastorella et al. note, however, that people’s opinions about the presence of dead wood in forests are little studied.
Special Functions of Dead Wood
The term dead wood refers to all non-living woody biomass not contained in the litter, either standing, lying on the ground, or in the soil. Dead wood includes wood lying on the surface, dead roots, and stumps larger than or equal to 10 cm in diameter.
Merganičová et al presented a broad definition of dead wood and its components. Overall, the dead wood can be subdivided into two main components: standing dead trees (snags) and lying dead wood (logs). Standing dead wood consists of standing dead trees, snags, and stumps, and lying dead wood includes downed dead trees, and lying dead wood pieces, which are often called logs.
Forest dead wood is an important indicator of the biodiversity level because it provides a habitat for many species. A wide range of plants and animals is strongly associated with standing and lying dead wood.
Dying and dead trees, either standing or fallen and at different stages of decay, are valuable habitats (providing food, shelter and breeding conditions, etc.) for a large number of rare and threatened species: saproxylic insects, invertebrates, lichens, bryophytes, birds and mammals.
Dead wood is also a fundamental component of nutrient cycles, regulates water flows, prevents soil erosion, and contributes to carbon storage in the forest. However, on the other side, dead wood is considered to be the cause of biotic and abiotic disturbances, an obstacle to forest management activities (i.e., reforestation, logging), and a threat to public safety (visitors and forest workers).
For this reason, in Europe, dead wood in forest ecosystems is traditionally perceived negatively by forest managers, because it may indicate ‘mismanagement, negligence, and wastefulness’ of the applied forest management.
Dead wood is claimed to be disliked also by the public because it reduces the scenic beauty and recreational values of forests. On the other hand, dead wood is the second most photographed element of the forest, which highlights its important role in forest perception.
Public perception of natural dead wood may vary considerably according to the size and amount of the debris, the level of decay, the stand’s age, and whether additional information explained the debris’ value to biodiversity.
For example, research by Karjalainen shows that if dead wood elements are sparsely distributed, they can serve as landmarks and increase a person’s ability to understand or read the landscape around them, and thus contribute to positive aesthetic perceptions. Dead wood enhancing the wilderness character of a forest stand and is also associated with sceneries of untouched natural forests or wilderness areas, where visitors can indulge in a sensation of being far away from a stressful daily life.
Schroeder and Daniel found that people seem to like downed wood caused by natural events better than logging debris. Sheppard and Picard proved that pests have a significant negative impact on the visual appeal of a landscape and thus potentially on the visitor experience.
However, reductions in visual quality due to pest (especially beetles or gypsy moth) attacks may be outweighed by the high visual quality of the overall scene. Low levels of beetle damage may even enhance the visual quality of a landscape temporarily.
In turn, Hauru et al. proved that sites with fresh logs were considered more aesthetically appealing than sites with old or no logs.
As the analysis of the literature shows, much is known about preferences regarding landscapes with dead wood, but there is little information about how such a landscape influences a person’s mental relaxation, improves mood, increases positive feelings, the level of vitality, etc.
Research into landscape preferences indicates that that the attractiveness of a forest with dead wood may be determined by the variants of dead wood.
Hence, the aim of this work is to investigate the restorative effects of short 15 min exposures to a natural forest and managed forest with dead wood. The aim is also to check if there is a difference in the remedial effects related to the variant of dead wood
Hypothesis, Participants and Study Sites
In order to figure out the influence of forest landscape with dead wood on human psyche, the study was conducted and the options and hypothesis were listed as below:
Option A: forest reserve with dead wood subject to natural decomposition processes;
Option B: managed forest with visible cut wood and stumps;
Option C: managed forest with standing dead trees from bark beetle outbreak. The following hypotheses were adopted in the study:
Hypothesis 1: All analyzed forest areas with different variants of dead wood have a restorative effect on people (increase in perceived restorative results, subjective vitality and positive emotions, and a decrease in negative emotions).
Hypothesis 2: There are differences between the restorative effects of the forest reserve, the managed forest with traces of maintenance and harvest cuts, and the forest with standing dead trees infested by the bark beetle.
There are forty-one young people participated in the study. Volunteers who agreed to participate in the research were informed about the study goals as well as the procedure of its conduct before the beginning of the experiment.
Participants in the research were young adults aged 19–20. The volunteers we recruited were both women and men, residents of rural areas, mainly in Białowieża community (inhabited by slightly more than two thousand people) and its surroundings.
The vast majority of participants (except two people) have lived in the area since birth. We sent email invitation letters to several tourist guides and distributed the invitation through various social media channels.
The invitation contained information about the date and place of the meeting, its purpose, and the expected duration of the experiment. Tourist restrictions due to the pandemic caused by the Covid-19 virus meant that there were no tourists or occasional visitors to Białowieża in our study.
Only healthy people without mental or physical diseases or metabolic syndromes participated in the study. The participants did receive some incentives for participating in the study. These were small gifts in the form of notebooks and albums promoting tourism in Poland.
All operations undertaken in the research were in accordance with the ethical standards of the Polish Committee for Ethics in Science and the Declaration of Helsinki from 1964 with further amendments.
The research was conducted in the northeastern part of Poland, in the forests of the Białowieża Primeval Forest. The forest is a unique area, with fragments of primeval forests preserved, there are also tree stands transformed by humans to a different extent. This element was very important for the achievement of the goal of our work.
As it made it possible to find, in close range, both a fragment of a forest “untouched” by human hands, a reserve forest in which natural processes leading to tree dieback occur and their effect is a large amount of dead wood at various stages decay (location A) and the forest in which typical management is carried out, related to, among others, selective tree cutting (location B).
In the managed forest, due to biodiversity, some of the cut-down wood remains in place, so there are visible traces of cuts in the form of lying logs or cut stumps.
We also chose the Białowieża Primeval Forest because it has recently been the subject of social discourse, both national and international, in connection with its control by the bark beetle, which caused significant havoc in forest stands, including stands managed for timber production ones, outside the reserves or the Białowieża National Park.
Therefore, to compare the restorative effect of a forest with dead wood, we also took into account the stand with dead trees infested by pests (location C).
The psychological condition of the participants was measured in rooms, before the experiment (pre-test) and just after its end (post-test). The experiment was carried out in two days. The respondents were randomly divided into groups. Each group visited all three sites in one day. Partial counterbalancing was used in the experiment.
For example, for the first group it was a reserve forest, then a managed forest with lying dead wood, and then the forest stand infested by bark beetles with standing dead trees.
The order of the exhibitions was dictated by logistical considerations, and efforts were made to maintain a similar travel time between consecutive exhibitions.
Each participant viewed the forest landscape for approximately 15 min, sitting or standing a few meters distance from the others to have the chance to relax and act according to the researcher’s instructions.
The stand was viewed from the nearby road. The participants were not allowed to use mobile phones during the study, neither could they talk to each other, drink energy drinks, or smoke cigarettes.
Four psychological questionnaires were used to measure the effects of viewing of dead wood in the forest environment on psychological responses on the participants.
Raw data retrieved from psychological questionnaires were used for statistical analysis purposes. A parametric, one-factor repeated measure ANOVA was conducted to analyse the effects of different expositions.
Forest Contribution to Human Mental Strength
Our research provides further evidence that the forest significantly contributes to the regeneration of human mental strength. It turns out that with the current decline in biodiversity in the world, people derive their energy from landscapes that embody not only recreational functions, but also beneficial ecological functions (forest reserve).
According to the results of our research, the total change of mood was highest in the forest reserve (A), where the natural, slow decay processes were visible. Our research shows that greater environmental diversity is conducive to mood improvement and has greater restorative properties.
This is confirmed by the results not only on the POMS scale, but also on the other three scales (PANAS positive, ROS, and SVS). Additionally, Watson et al. found that environmental diversity is positively related to human well-being.
There is no conflict between biodiversity and the restorative properties of the forest. Our research results are not reflected in the studies by Martens et al., Simkin et al. or Herzog et al., which showed that a managed forest, in contrast to the natural one, has greater restorative values. Perhaps this is because we compared forest environments (also managed and natural) with different variants of dead wood in every one of them.
We noted statistically significant differences with two of the six POMS scales, namely tension and fatigue. As for tension, its highest average value was associated with the exposure of the economic forest with dead standing trees infested by the bark beetle (C).
It seems that in this case the forest could have been perceived as less safe, threatening human health and life. Although the participants of the experiment were at a safe distance from the infested trees, they could subconsciously feel the threat of the presence of dead trees, which will fall eventually.
The forest reserve, with dead pieces of wood lying naturally with ongoing decay processes, may have seemed safer, so its exposure caused the most significant decrease in tension compared to the pre-test.
On the other hand, the forest reserve (A) decreased the level of fatigue to a lesser extent than the managed forest (B). Perhaps it is related to the fact that the forest reserve has a greater number of stimuli, a greater number of landscape components, greater species diversity, which may affect the speed of reduction of fatigue.
Interestingly, we expected that exposure to forest landscape involving dead wood could have a particular impact on the Depression scale as dead wood could be an indicator for a ‘dying’ forest and as Sreetheran and van den Bosch point out, it can be associated with sad or scary thoughts.
Previous studies showed that a stronger decrease in the “negative impact”, including depression and anger, in a cultivated forest may be because of a lower amount of dead wood, which may be sad. However, the results obtained by us did not show any statistical correlation in this case.
Our research confirms that the forest environment has a restorative effect also by changing emotions, in particular increasing positive emotions.
In previous studies, we observed that a visit to the forest also favours the reduction of negative emotions, this time we found statistically significant differences only in relation to the increase in positive feelings.
Other studies also showed that recreation in the forest reduces negative emotions. However, in general, these studies compared extremely different environments (forest vs. city). Our research focused on differences within the same forest environment with a specific variant of dead wood.
Going to the forest evoked positive feelings among the participants, it was connected with something pleasant. However, exposure to a landscape with dead wood did not reduce negative feelings. This proves that not every forest environment is equally reconstructing.
The greatest increase in positive feelings was recorded in the case of the forest reserve (A). Among the two variants of the managed forest, the growth of positive feelings was caused by a forest with traces of human harvesting activity (B) than a forest with dead standing trees, infested by the bark beetle (C). It seems that in this case, human activity in the forest evokes greater understanding, is more acceptable, and evokes more positive emotions than the damage caused by natural processes, caused by the beetle outbreak.
Importance of Forest Management and Forest Restoration
Considering the results of the ROS and SVS scales, we found that each of the forest variants included in the experiment had a restorative effect on the psyche of the participants and contributed to an increase in the subjective feeling of vitality.
The results of many studies show that the ROS and SVS scale values increased because of recreation in the forest environment. We observed that this increase was the strongest as a result of exposure to the reserve forest, then the commercial forest with standing dead trees infested by bark beetles, and the weakest in the managed forest with traces of harvesting work.
Additionally, as previously noted by Martens et al. and Simkin et al., this last observation leads us to conclude that preferences for a particular environment do not necessarily mean that it is restorative.
Preference studies conducted in coniferous forests infested by the bark beetle showed high social sensitivity to beetle activity. The greener and more buoyant the forest was, the more it was appreciated for vitality.
Conversely, dead and dying material (e.g., dead trees, felling residues) negatively affected preferences regardless of their genesis. These aesthetic effects are especially felt when beetle damage is observed nearby compared to intermediate or background zones.
Our research has shown that a forest with dead wood and standing trees has better restorative properties in virtually all the scales considered (except the tension scale) than the economic stand with traces of harvesting work.
The results of our research indicate which forest model provides people with greater health benefits. Research findings support forest managers and policymakers at both national and regional levels interested in more effective environmental and health education.
Understanding the impact of the forest management model on people’s well-being is valuable in developing effective forest management strategies, but also important for the benefit of society (e.g., reduced spending on health systems, increased labor productivity, reduced absenteeism).
Our research shows that recommendations for forest management to leave a certain amount of dead wood in the forests due to the need to increase biodiversity are also important from a social point of view.
Dead wood in forests, especially that which is associated with natural processes, should be a permanent component of the forest landscape. National parks and forest reserves, where dead wood is more abundant, might be suitable places for restorative purposes.
However, managed forests, in which the amount of dead wood is increasing in recent years, are also worth consideration for that matter.
Contact with the forest, despite dead wood, is more restorative than no contact: the values of all scales were higher in the pre-test stage than after. The restorative value of a managed forest is lower than that of a forest reserve.
Exposure to a stand infested by the bark beetle caused greater tension in the participants of the study than exposure to a managed forest with fallen logs. The greater value of fatigue was recorded in the case of the forest reserve, and the lowest in the case of the managed forest with traces of intentional cuts.
Before the experiment, the level of positive feelings was lower. There was an increase in positive feelings as a result of exposure. The forest reserve has the best effect, the forest infested with bark beetles is the least effective among tested ones.