Granens historia

Granen är idag vårt vanligaste trädslag. Men så har det inte alltid varit. Vår miljö har en historia och vårt landskap är i ständig förändring. Granen var vild när den kom till norra Sverige för 4 000 år sedan och trängde in i skogarna som då dominerades av tall och björk. Den var fortfarande delvis vild när den tog över de glesa skogarna och ljunghedarna i södra Sverige för 100–200 år sedan. Men numera är den ”domesticerad” och tillbringar det mesta av sitt liv i monokulturer och i raka rader

Dynamics of Long-lived Foundation Species: The History of Quercus in Southern Scandinavia

(1) The long-term history of Quercus in southern Scandinavia has received little attention despite its important role in modern conservation. In this study the 4000-year dynamics of Quercus, its habitat and other important taxa were analysed with pollen data from 25 small hollows and 6 regional sites across southern Scandinavia. The aim was to provide a context for understanding the species’ current status and managing its future dynamics. (2) The results indicate that Quercus is much less abundant today than at any time during the previous 4000 years and corroborate the rapid decline reported in 18th- and 19th-century historical records. Modern pollen percentages are 45-60% of 17th-century values and only 20-35% of the maximum values reached in the 3rd century. (3) A strong positive correlation exists between the abundance of Quercus and the abundance of Tilia, Corylus and Alnus, which also experienced a steady decline across the region in the last two millennia. Climate change is the broad-scale driver of the observed dynamics, but human activity introduced considerable variation in the regional and temporal details of these changes. In the hemiboreal northern part of the study area the decline of Quercus appears to be controlled largely by competition with other tree species (especially Pinus and Picea), mediated by harvesting. In the temperate south part Quercus forests decreased through deforestation for agriculture. (4) Multivariate analyses indicate that although substantial phytogeographical variation has existed through past millennia the regional vegetation is more homogeneous today than in earlier periods. (5) Synthesis. The long-term decline and recent rapid reductions in Quercus populations throughout southern Scandinavia are striking and indisputable. From the perspective of both the populations of Quercus and its associated species of insects and epiphytes, the recent rate of decline is extremely rapid. Given the former abundance, longevity and capacity for persistence of Quercus, current populations of Quercus and its associated species appear to represent biological legacies in the midst of protracted decline. Based on these results, a reasonable conservation goal is to restore the abundance and distribution of Quercus to levels that preceded the drastic decline in the 18th and 19th centuries.Organismic and Evolutionary Biolog

Oaks retained in production spruce forests help maintain saproxylic beetle diversity in southern Scandinavian landscapes

In Northern Europe, human activities have caused a substantial decrease in the number of old deciduous trees over the last two centuries, leading to a decline in species populations associated with this habitat. One way to mitigate this trend is to increase the abundance of mature and old deciduous trees in commercial forests, such as by tree retention at final harvest. We analysed the biodiversity value of retained mature oaks in the production forests of Norway spruce in southern Sweden, using oaks in pastures as reference. The forest oaks were grown in two different levels of shade. We analysed two categories of saproxylic (i.e. dead wood-dependent) beetles: those utilizing oaks (Group I) and those utilizing oak but not spruce (Group II, which was, therefore, a subcategory of Group I). We found that forest oaks sustained high beetle diversity, in particular, Group I beetles, which were significantly more abundant in forest oaks in heavily thinned patches, as compared with pasture oaks and oaks in moderately thinned patches. For both beetle groups, the composition differed between the forest oaks and pasture oaks, indicating that the forest oaks can be a complementary habitat to that of pasture oaks. There was a positive relationship between oak dead branch diameter and beetle biodiversity, but only for older oaks (∼200 years old). We conclude that retaining oaks in production spruce forests can increase the diversity of oak-associated beetles at the landscape scale. Since many oak associated species depend on relatively high levels of insolation, management of retained oaks in production forests should include periodic removal of encroaching trees

Forest floor bryophyte and lichen diversity in Scots pine and Norway spruce production forests

Bryophytes and lichens are two main components of the forest floor vegetation. They provide essential ecosystem services, including nutrient recycling and water regulation. Here, we contrast the species richness, cover and community composition of forest floor bryophytes and lichens in Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) dominated production forests. The study sites were located in the hemiboreal zone of southern Sweden, and represented early-, mid- and late rotation stands. Our aim was to examine the potential consequences for forest floor biodiversity from the decreasing use of Scots pine production forests in this region.Whereas Scots pine and Norway spruce stands did not differ in bryophyte cover, we found a higher cover of lichens in Scots pine stands, and highest in the intermediate aged stands. Also the species richness of lichens was higher in the Scots pine stands, while bryophyte species richness was higher in the Norway spruce stands. Differences in canopy cover and associated light transmittance to the forest floor appears to be important drivers for distinctive different forest floor communities in the Scots pine and Norway spruce stands, as revealed by NonMetric Multidimensional Scaling (NMDS). Mean Ellenberg indicator values for bryophytes and lichens showed that species associated with Scots pine stands were characterized by their tolerance of brighter conditions, higher insolation, and better adaptation to a continental climate. Norway spruce stands instead had a comparably larger proportion of species tolerating lower light, but also indicators of higher available nutrient levels, humidity, and pH. The outcome of the Ellenberg indicator species analysis, as well as the larger cover of lichens,and adaptations to drought found among some mosses, revealed that forest floor communities are shaped by different environmental factors in Scots pine and Norway spruce production stands. These environmental differences, and the quantified shifts in forest floor communities identified in this study, indicate the large shifts in understory bryophyte and lichen species composition and abundance that is likely to occur if Scots pine stands are converted to Norway spruce

Broadleaf retention benefits to bird diversity in mid-rotation conifer production stands

Retention forestry involves saving important forest structures for flora and fauna during the final felling of a stand, including dead wood and variable amounts of living trees, i.e. green tree retention (GTR). Here we evaluate the long-term effects on avian diversity from GTR by surveying forest birds in 32 mid-rotation stands in southern Sweden, in which broadleaf GTR was present or absent. Complementing the many studies that have assessed GTR in clear-cuts, our results indicated that bird assemblages can also benefit from broadleaf GTR several decades after final felling in conifer dominated production stands. The GTR stands harboured a higher bird abundance and species richness than the control stands without GTR, and also appears to have benefited several important guilds, such as broadleaf-associated birds and cavity nesters. However, variation in the number trees retained, the species composition of retained trees, and their environmental context within the stand (e.g. density and proximity of surrounding production trees), limited our capacity to detect threshold requirements for GTR. In summary, our study provides a "glimpse into the future" as mid-rotation production stands with such old and large retained trees are unusual in today's landscape, but are expected to become more common in the decades to come, in Sweden and many other nations. Our study thereby provides provisional support for the continued and future use of this practice, and indicates that the biodiversity contribution of retention trees continues to occur several decades into the stand's rotation

Thinning around old oaks in spruce production forests: current practices show no positive effect on oak growth rates and need fine tuning

The expansion of spruce-dominated forestry in Southern Sweden during the twentieth century has led to a considerable amount of oak (Quercus robur L.) woodlands being converted into stands dominated by planted spruce. The thinning of spruces around oak trees is currently done in Sweden to improve local diversity of insects, oak growing conditions and eventually decrease their mortality. To evaluate the effect of these treatments, we dendrochronologically studied growth of old (100–200 years old) oaks subjected to thinning of different intensity at nine locations in southern Sweden, and compared them to oaks located in nearby pastures. The overall pattern suggests that commonly adopted thinning intensities do not significantly affect oak growth. Oak growth was positively related to oak age and negatively to the amount of dead oak crown. Analyses of correlations between oak growth and summer drought conditions, as reflected by location-specific chronologies of the Monthly Drought Code (MDC), indicated that older trees exhibited generally negative correlations, whereas the correlation remained generally positive for the younger trees, both inside and outside forest stands. We propose that removal of spruces should be primarily done around older and healthier-looking trees

From mixtures to monocultures: Bird assemblage responses along a production forest conifer-broadleaf gradient

Increasing the prevalence of broadleaf trees in conifer-dominated production forests is a recommended means of improving habitat availability for broadleaf and mixed-forest species. The implications for biodiversity are often measured by contrasting broadleaf-conifer mixtures with conifer-dominated stands. However, few studies include broadleaf-dominated stands in these assessments. Here we contrasted the bird assemblages of even-aged production forests along a mixture gradient from Norway spruce (Picea abies) dominated, to birch (Betula spp.) dominated stands in southern Sweden. We conducted point count surveys of bird individuals exhibiting breeding behaviour within 30 stands varying from <0.5% to over 98.5% broadleaf by basal area. A total of 355 birds were detected, comprising 36 bird species, seven of which are classified as near threatened by the Swedish Red-list. Our results indicate i) a distinct shift in bird community composition linked to the percentage of broadleaf trees at stand and landscape scales, ii) significantly higher bird species richness, evenness, and abundance in stands with a higher proportion of birch, iii) higher bird abundance in birch-dominated stands than in mixtures, and iv) shifts in bird species guilds as related to stand basal area, the amount of shrubs in the understory, and quantities of dead wood. All of these results have implications for the ways in which production forest management could be altered to enhance avian diversity, and we discuss these with respect to the use of broadleaf versus mixed-species stands

Natural versus National boundaries

Applying biogeographical insights to the regulation of production forestry and the determination of forest reserve strategies is expected to increase the effectiveness of biodiversity conservation actions. Here, we assess the extent to which such applications take place. By using Sweden as a case study, we demonstrate fundamental differences among biogeographical regions in natural patterns and processes, past land-use, and anthropogenic impacts that need to be better incorporated into strategic conservation planning and decisions. Furthermore, assessment of specific forestry regulations and biogeographical variation in a number of other countries/provinces embracing boreal and temperate biomes also indicate that natural boundaries are insufficiently considered in forest management policies. We suggest that a substantial potential exists to better align conservation priorities with biogeographical characteristics. To illustrate the application of such an approach, we present a decision support model on how forest conservation policies that rest on natural boundaries and ecological processes can be developed

Forest biodiversity, carbon sequestration, and wood production: modeling synergies and trade-offs for ten forest landscapes across Europe

Original ResearchEurope’s forests provide vital habitat for biodiversity and essential ecosystem services whose provision must be sustained or enhanced over the coming century. However, the potential to secure or increase forest ecosystem services, while securing the habitat requirements of taxa remains unclear, especially within the context of uncertain climate and socio-economic developments. To tease out the associated trade-offs and synergies, we used 10 case study landscapes within nine countries throughout Europe. Starting with the current status of the forests in the case study landscapes, we simulated forest development 100 years into the future. Simulations were embedded in three combined climate and socio-economic frame scenarios based on global and European policies which varied in their climate change mitigation efficiency. Scenarios were translated into country specific projections of climate variables, and resultant demands for wood products. Forest management regimes were projected to vary in response to these scenarios at local scales. The specific combinations of alternative forest management practices were based on parallel research and input from local forest stakeholders. For each case study, a specific forest growth simulator was used. In general, the climate scenarios applied did not cause fundamentally different ecosystem service outputs at the case study level. Our results revealed almost no reduction in outcomes for biodiversity indicators with an increase in wood production, and in some cases synergistic results occurred when diversity was actively promoted as part of the management concept. Net carbon uptake was not strongly correlated with biodiversity, indicating that biodiversity-friendly forest management doesn’t need to curtail carbon sequestration. Notably, we obtained heterogeneous results for the relation between sustainable wood production and net carbon uptake. Most scenarios resulted in a more or less reduced net carbon uptake over the long term, often due to stand age class distribution shifts. Levels of sustainable wood production varied widely during the simulation period, from significant increases (Sweden, Lithuania) to minor changes (Slovakia, Turkey) and slight decreases (Ireland, Netherlands). We place our results within the larger context of European forest policy and the challenges of simulating and contrasting forest biodiversity and the ecosystem services that societies depend on outcomes for biodiversity indicators with an increase in wood production, and in some cases synergistic results occurred when diversity was actively promoted as part of the management concept. Net carbon uptake was not strongly correlated with biodiversity, indicating that biodiversity-friendly forest management doesn’t need to curtail carbon sequestration. Notably, we obtained heterogeneous results for the relation between sustainable wood production and net carbon uptake. Most scenarios resulted in a more or less reduced net carbon uptake over the long term, often due to stand age class distribution shifts. Levels of sustainable wood production varied widely during the simulation period, from significant increases (Sweden, Lithuania) to minor changes (Slovakia, Turkey) and slight decreases (Ireland, Netherlands). We place our results within the larger context of European forest policy and the challenges of simulating and contrasting forest biodiversity and the ecosystem services that societies depend oninfo:eu-repo/semantics/publishedVersio

Palaeoecological data indicates land-use changes across Europe linked to spatial heterogeneity in mortality during the Black Death pandemic

Historical accounts of the mortality outcomes of the Black Death plague pandemic are variable across Europe, with much higher death tolls suggested in some areas than others. Here the authors use a 'big data palaeoecology' approach to show that land use change following the pandemic was spatially variable across Europe, confirming heterogeneous responses with empirical data.The Black Death (1347-1352 ce) is the most renowned pandemic in human history, believed by many to have killed half of Europe's population. However, despite advances in ancient DNA research that conclusively identified the pandemic's causative agent (bacterium Yersinia pestis), our knowledge of the Black Death remains limited, based primarily on qualitative remarks in medieval written sources available for some areas of Western Europe. Here, we remedy this situation by applying a pioneering new approach, 'big data palaeoecology', which, starting from palynological data, evaluates the scale of the Black Death's mortality on a regional scale across Europe. We collected pollen data on landscape change from 261 radiocarbon-dated coring sites (lakes and wetlands) located across 19 modern-day European countries. We used two independent methods of analysis to evaluate whether the changes we see in the landscape at the time of the Black Death agree with the hypothesis that a large portion of the population, upwards of half, died within a few years in the 21 historical regions we studied. While we can confirm that the Black Death had a devastating impact in some regions, we found that it had negligible or no impact in others. These inter-regional differences in the Black Death's mortality across Europe demonstrate the significance of cultural, ecological, economic, societal and climatic factors that mediated the dissemination and impact of the disease. The complex interplay of these factors, along with the historical ecology of plague, should be a focus of future research on historical pandemics