Jari Kouki

Retention Forestry to Maintain Multifunctional Forests: A World Perspective

The majority of the worlds forests are used for multiple purposes, which often include the potentially conflicting goals of timber production and biodiversity conservation. A scientifically validated management approach that can reduce such conflicts is retention forestry, an approach modeled on natural processes, which emerged in the last 25 years as an alternative to clearcutting. A portion of the original stand is left unlogged to maintain the continuity of structural and compositional diversity. We detail retention forestrys ecological role, review its current practices, and summarize the large research base on the subject. Retention forestry is applicable to all forest biomes, complements conservation in reserves, and represents bottom-up conservation through forest manager involvement. A research challenge is to identify thresholds for retention amounts to achieve desired outcomes. We define key issues for future development and link retention forestry with land-zoning allocation at various scales, expanding its uses to forest restoration and the management of uneven—age forests.

Forest Fragmentation in Fennoscandia: Linking Habitat Requirements of Wood-associated Threatened Species to Landscape and Habitat Changes

Fragmentation may occur simultaneously in different spatial and temporal scales. The ecological importance of fragmentation depends both on the scale of fragmentation and on the habitat requirements of the species. The fragmentation of old-growth forests is regarded as one of the most important causes for the recent decline of several forest-dwelling species in Fennoscandia. In Fennoscandia landscape-level fragmentation has proceeded differently in various areas. For example, in eastern Finland mature forest fragmentation was evident very early. By the 1800s, only one third of the landscape was covered by 150 yr old forests. This early fragmentation resulted mostly from the slash-and-burn cultivation practised widely in these areas. In the northern Fennoscandia, however, no such landscape changes have been found before the 1900s. During the 1900s fragmentation has accelerated. Recent results suggest that biological impacts of current landscape-level fragmentation of mature forests may have been overestimated, especially among invertebrate species. Specific habitat requirements of these groups are still poorly known. Instead of requiring mature forests, several wood-associated threatened species may require only dead wood that can occur in any successional stage, in both managed and protected areas. Such variability in the habitat requirements allows good opportunities for preservation of the threatened species. Results from current research indicate the need to restore and recreate natural fire-originated early successional stages where the amount of coarse woody debris is high. Promotion of coarse woody debris in young managed forests is potentially a very effective way to sustain populations of several threatened wood-associated species.

Saproxylic beetles in managed and seminatural Scots pine forests: quality of dead wood matters

Habitats of saproxylic species (species that are dependent on decaying wood) have been greatly changed during the last few decades. Due to intensive forest management, volume of dead wood has decreased and its quality is less diverse in managed than in naturally disturbed forests. There is an urgent need to develop and apply guidelines for forest management so that they also facilitate the survival of saproxylic species and mimic the natural dynamics of forests. This requires detailed information about how the differences in forest structure between managed and natural forests affect the occurrence of species and what are the real habitat requirements of species. Thus, we explored the richness of saproxylic beetles, composition of species assemblages and relationship between saproxylic beetles and their substrate in managed and seminatural pine dominated forests. Richness of saproxylic species tended to be higher in seminatural than in managed forests but the difference was not statistically significant. However, species assemblages in managed forests had differentiated from those on seminatural sites. Our results suggest that for the survival of saproxylic beetles, increasing the total volume of dead wood is an important task but more important one is to improve the diversity and continuity of dead wood in managed forests. This requires that the continuous production of dead wood is allowed also in managed forests to improve the continuity of dead wood and availability of recently dead wood. In green tree retention the main stress should be laid on the trees of large diameter to maintain the potential for large decaying wood.

Tree retention as a conservation measure in clear-cut forests of northern Europe: a review of ecological consequences

Abstract Since the mid-1990s, it has been common practice to leave trees for biodiversity purposes when clear-cutting in Finland, Norway and Sweden, and regulations for such tree retention are today included in national legislation and certification standards. Peer-reviewed research publications on tree retention from studies performed in the three countries were analyzed and about 50 relevant biodiversity studies were found, with the first published in 1994. Most studies were directed towards beetles and dead wood, especially high stumps. General conclusions were that retention trees (1) provide some of the substrate types required by early-successional species, (2) alleviate the most serious consequences of clear-cutting on biota, and (3) cannot maintain characteristics of intact mature forests. Larger volumes and more trees tend to maintain diversity better. There is a particular lack of studies on dispersal, landscape effects and long-term dynamics. There is a need to study further the relationship between the biota and the amount of trees, as well as their spatial arrangement. Retention trees should preferably be evaluated in relation to other components in multiscaled conservation, including woodland key habitats and larger protected areas.

Can retention forestry help conserve biodiversity? A meta-analysis

Industrial forestry typically leads to a simplified forest structure and altered species composition. Retention of trees at harvest was introduced about 25 years ago to mitigate negative impacts on biodiversity, mainly from clearcutting, and is now widely practiced in boreal and temperate regions. Despite numerous studies on response of flora and fauna to retention, no comprehensive review has summarized its effects on biodiversity in comparison to clearcuts as well as un-harvested forests. Using a systematic review protocol, we completed a meta-analysis of 78 studies including 944 comparisons of biodiversity between retention cuts and either clearcuts or un-harvested forests, with the main objective of assessing whether retention forestry helps, at least in the short term, to moderate the negative effects of clearcutting on flora and fauna. Retention cuts supported higher richness and a greater abundance of forest species than clearcuts as well as higher richness and abundance of open-habitat species than un-harvested forests. For all species taken together (i.e. forest species, open-habitat species, generalist species and unclassified species), richness was higher in retention cuts than in clearcuts. Retention cuts had negative impacts on some species compared to un-harvested forest, indicating that certain forest-interior species may not survive in retention cuts. Similarly, retention cuts were less suitable for some open-habitat species compared with clearcuts. Positive effects of retention cuts on richness of forest species increased with proportion of retained trees and time since harvest, but there were not enough data to analyse possible threshold effects, that is, levels at which effects on biodiversity diminish. Spatial arrangement of the trees (aggregated vs. dispersed) had no effect on either forest species or open-habitat species, although limited data may have hindered our capacity to identify responses. Results for different comparisons were largely consistent among taxonomic groups for forest and open-habitat species, respectively. Synthesis and applications. Our meta-analysis provides support for wider use of retention forestry since it moderates negative harvesting impacts on biodiversity. Hence, it is a promising approach for integrating biodiversity conservation and production forestry, although identifying optimal solutions between these two goals may need further attention. Nevertheless, retention forestry will not substitute for conservation actions targeting certain highly specialized species associated with forest-interior or open-habitat conditions. Our meta-analysis provides support for wider use of retention forestry since it moderates negative harvesting impacts on biodiversity. Hence, it is a promising approach for integrating biodiversity conservation and production forestry, although identifying optimal solutions between these two goals may need further attention. Nevertheless, retention forestry will not substitute for conservation actions targeting certain highly specialized species associated with forest-interior or open-habitat conditions.

Assessing the naturalness of boreal forests in eastern Fennoscandia

Abstract This study aims to define the level of naturalness in the protected forests of eastern Fennoscandia, i.e. to determine how natural or semi-natural are the currently protected and unmanaged forests, and the extent to which the past human influence has affected the current forest structure. The plots used in the study represent both currently unmanaged and managed forests. The unmanaged forests are located in nature protection areas. We have used data from earlier forest inventories, determined by the visual estimation of compartments, together with the measured stand variables. The data cover detailed analysis of 79 forest sites or stands in both in mesic and sub-xeric forests. The whole successional gradient is included in the data. In unmanaged forests, fellings have occurred on 39% of the sample plots in sub-xeric areas, and on 28% of the sample plots in mesic areas. According to the historical records 33% of all the unmanaged forests have definitely been (selectively) felled, 21% possibly, and 46% show no signs of fellings. In general, the unmanaged forests in eastern Finland bear ample evidence of light selection felling. Thus, these stands could better be regarded as semi-natural rather than natural forests. Mesic old-growth stands are less affected (73% are completely untouched), but the tree volume data, number of tree storeys and the signs of slash-and-burn cultivation are nevertheless clear evidence of the impact of human activities. The growing intensity of human activities since the 1950s can also be seen in semi-natural succession forests as the presence of cut stumps and the probability of felling in young stages. Real natural/semi-natural sapling and young forests are very rare and occur only in Russia. The diameter distribution in semi-natural sapling and young forests with reverse J-shaped distributions showed considerably greater variation. Also the mature and old-growth, semi-natural forests were characterised by the decrease in reverse J-shaped distributions. The timber volume in stands was generally lower at the beginning of the 20th century. Overall, the forests in nature reserves are structurally rather different to those growing at the beginning of the 20th century, and show patterns not typical of natural forests. The slash-and-burn agriculture practised during the 1800s and earlier has profoundly affected the natural spatial and temporal disturbance regimes, with clear consequences for the current tree species and age composition. More recent deviations from the natural forest structures are, however, largely due to the absence of natural and anthropogenic forest fires during the 1900s.

Conservation of beetles in boreal pine forests: the effects of forest age and naturalness on species assemblages

The effort of boreal forest conservation has emphasised the preservation of old-growth forests while the role of young successional stages in maintaining biodiversity has remained largely unstudied. We compared the richness of beetle species and composition of species assemblages between managed and seminatural forests in five stages of forest succession. The sites were in boreal sub-xeric pine-dominated forests in eastern Finland. Seminatural study sites, especially the recently burned sites, were important habitats for threatened and near-threatened species. We propose that young stages of natural succession should be included in the network of protected forest areas. On the other hand, the composition of saproxylic species assemblages in seminatural forests differed from the assemblages in managed forests, indicating also the need to improve the forest management guidelines so that they better address the requirements of species protection. Regeneration methods applied should resemble or mimic the natural disturbances more closely.

Sampling the rarest: threatened beetles in boreal forest biodiversity inventories

Presence or absence of threatened species in samples is information that is widely used in designing and implementing conservation actions. We explored the effectiveness of beetle (Coleoptera) inventories and contribution of different sampling methods in revealing occurrences of threatened and near threatened species in boreal forests. The number of species caught using traps in a particular area proved to be a useful indicator of the representativeness of data, the relationship between total number of species and the number of threatened and near threatened species being almost exponential. Samples containing less than 200 trapped species (or 2000 individuals) are almost useless in surveying threatened and near threatened species. The probability of finding such species increases considerably when the number of trapped species exceeds 400. Window traps attached directly on the trunks of dead trees proved to be the most efficient sampling method in trapping threatened beetles, whereas many other standard methods gave relatively poor results. We suggest that the best alternative in surveying threatened species in boreal forests is a combination of intensive direct searching and trunk window traps. Finding threatened beetles with rigorous probability requires very large sample sizes, even if the most effective sampling methods are used. For example, ranking 10 boreal forest areas to be protected according to the occurrence of threatened species with some reliability may require trapping of over 100000 beetle individuals. Collecting and identifying these large samples routinely in conservation actions is not feasible, which means that shortcuts (indicators etc.) are necessary. However, a lot of good-quality inventories with appropriate sampling efforts are needed before these shortcuts can be identified and elaborated. Such inventories are also crucial for the improvement of the classification of threatened species and full assessment on how past forest management has eventually affected the biota.

Fifty Years of Landscape Transformation in Managed Forests of Southern Finland

Intensive forest management has changed both local and regional characteristics of Fennoscandian forest. However, quantitative documentation of landscape transformations is rare. In this study, five forest landscapes were examined in order to define and quantify forest landscape transformation in southern Finland from the 1940s to the 1970s and 1990s. These areas of 140-200 km2 contained both private and state-owned forests. Digital aerial photographs of each area were classified into no-canopy forest (clear-cut and seedling stands, open mires) and closed-canopy forest (young and mature stands). Patch density, mean patch size, largest patch index and edge density calculated for closed-canopy patches indicated fragmentation from the 1940s to the 1970s and recovery from the 1970s to the 1990s. Trends were very similar in both ownership groups. Thus, fragmentation of closed-canopy forests has not progressed continuously in southern Finland, but shows different patterns depending on the period. However, the recovery observed between the 1970s and 1990s does not necessarily mean an increased abundance of the natural old-growth areas that are needed to host many of the currently threatened species.

Biomass offsets little or none of permafrost carbon release from soils, streams, and wildfire: an expert assessment

As the permafrost region warms, its large organic carbon pool will be increasingly vulnerable to decomposition, combustion, and hydrologic export. Models predict that some portion of this release w ...