During the last years, scientists published a large amount of papers and books on the ecology and functioning mixed forests. This has certainly contributed to advance our understanding of how a mixed species forest work, develop, function. Many studies focused on adapting management strategies under climate change to deliver important recommendations to practitioners (and I put myself into this bucket too, with my PhD thesis). But what are the main concerns of forest managers nowadays? Are they indeed worried about climate change and natural disturbance or do they just want to know how their forest will grow and when it will be ready to cut? A consortium of scientists took this time a different perspective to get answers (or better, to get questions!).
Here we are, talking again about mixed forests. In one of my latest posts I described what are the most important factors that can influence whether trees compete or complement each other. Yes, I am aware of it: this was very much a scientist perspective. Getting to know where a mixed forest can grow better than a monospecific forest under different site conditions can be quite interesting in the context of management but, frankly, I believe that results discussed only in ecological journal will hardly be put into practice by forest managers. We, scientists, often try to deliver useful recommendations and to transfer new knowledge to practical applications. Many project were initiated, carried out and concluded within the academic world but unfortunately, in many of them, forest managers, people who indeed cut, plant and manage forests that shapes our landscapes, were not involved.
In the context of the EuMIXFOR research network, scientists from 30 different countries decided to take a different perspective. They asked directly to forest managers of different countries what do they think about research on mixed forests in Europe (i.e., on what should scientists focus their research to better help them to manage mixed forests for the future). This turned out to be useful not only to bring closer practitioners to the research community, but also to help scientists to better identify research challenges and design future projects with practical outcomes.
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The methods used by the researchers was very simple. It did not involve ecological models and statistical analysis. They simply asked a total of 53 forest managers from 15 different European countries – 3 to 5 experts per country selected in the public and private sector – to provide a list of the 5-10 key questions about mixed species forests that according to their view require more efforts from the research sector. This resulted in a total of almost 300 questions. Then a group of forest researchers classified and merged these questions into eleven broad themes (1. Climate change; 2. Timber production; 3. Functional ecology, interactions; 4. Spatial patterns and stand structure; 5. Resistance and resilience to hazards; 6. Forest management; 7. Forest dynamics; 8. Ecosystem services; 9. Economy; 10. Site factors; 11. Policy, planning and tools) that helped to reduce the amount of questions to a total of 30. In a second step, the researchers contacted an independent sample of forestry professionals on 22 countries (5 to 15 forest managers per country) who, with the aid of an internet-based survey platform, ranked the questions according to their preference. At the end of this process it was possible to obtain the ten “hottest” questions selected by forest managers.
The 10 most highly ranked questions from forest managers
Among the most influential questions, the two highest in the ranking were related to resistance and resilience to climate change. Three questions were related to management and silvicultural interventions while five other questions to the provision of ecosystem services. As shown in the table below, the authors also evaluated what is the current status of the scientific knowledge related to the question to identify further research that would be needed in the future.
It was quite surprising for me to see that forest managers are very concerns about climate change and natural disturbances. In particular they seems to be interested to know what mixtures of species can provide the best resistance and stability to climate change stressors. I have read several papers in the last months dealing with the diversity-stability relationship in forest ecosystems, and most of them concluded that forests with higher species richness are better able to cope with environmental change than monocultures. This is nice to hear but – in my opinion – not of great help for managers. Particularly the role of species diversity to resist severe abiotic disturbances in still quite unclear because it largely depends on structure and species combinations than simply the number of species. I think what managers want to hear is what assemblage of species (or at least functional groups) are more suitable to cope with disturbances and how can they effectively increase complexity at multiple scales to enhance the forest natural capacity to adapt and recover after extreme events.
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This certainly connects to the questions about management and silvicultural interventions (e.g., what treatments shall be applied to maintain the desired species composition?). Here I fully agree with the authors: there are not many other alternatives than models of forest dynamics for evaluating possible future interventions. Yes, growth-and-yield, long-term experimental plots can be of great help but there are not many mixed experimental plots out there that we could use for assessing specific management interventions in multiple mixture types. So, in this case I believe there are not many other alternatives: managers should start believing more in models but scientists should give their best to deliver handy decision-support tools to practitioners. We cannot expect foresters to parameterize and run complex models without the aid of a practical user interface. What we also need is probably a better integration between ecological and economic evaluation. In this context, researchers with different background should join efforts to deliver comprehensive evaluations to forest managers in specific case study regions. Another point in which I strongly agree is the need to develop process-based models specifically targeted to simulate mixed stands (see this review paper on the topic).
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The remaining five questions were all related to the provision of ecosystem services. It is nice to hear that forest managers are not only concerned about wood production (question #5) but also to other services such as biodiversity, stability, carbon sequestration (questions #4, #6 and #9). A lot has been studied in the past years to understand if mixed forests deliver higher levels of ecosystem services, and probably even more to identify if mixed forests are more efficient in exploiting resources. Nevertheless, the authors underlined that there is quite a lot of work to do to translate from ecosystem functions to a quantification of ecosystem services (i.e., we still need to develop reliable indicators for assessing ecosystem service provision).
Science towards practice – and vice versa
I asked to one of the authors of the study, Aitor Ameztegui from the Forest Sciences Centre of Catalonia, to comment on their results: “We found that the issues of greatest concern to managers are precisely those that are being most studied by researchers. For example, there is great concern among European managers about how species mixtures can help to address climate change and disturbances”. The researcher continued saying that “Beyond the effect of mixtures, forest managers are interested in knowing the effects of certain species combinations and how to manage mixed forests. In this sense, we observed the need of generating additional knowledge to provide forest managers with evidence-based silvicultural guidelines allowing the establishment and maintenance of mixtures over time under different environmental conditions“.
Well, now we know what practitioners want to know to better manage mixed species forests. Can now science provide more answers?
Read the full paper: Coll, L., Ameztegui, A., Collet, C., Löf, M., Mason, B., Pach, M. et al. (2018) Knowledge gaps about mixed forests: What do European forest managers want to know and what answers can science provide? Forest Ecology and Management, 407, 106-115.
Main photo: Mixed pine-oak forest in La Granja (Spain) in which we can see the importance of mixture with the presence of an old oak. Author of the photo: Aitor Ameztegui.