Managing the future: Post-disturbance forest recovery across management types in Central Europe

FORESTS FOR OPTIMISTS AND SPECIESKüchli, C. (1997) Forests of hope: stories of regeneration. Earthscan Publications Ltd., London. 244 pp., photos. Paperback: Price ú19.99. ISBN 1‐85383‐505‐6. For most parts of the world, the general perception is that forests are under threat and are irreplaceably lost at an ever increasing rate. In this beautifully laid out and illustrated book by Christian Küchli a different and hopeful message is presented. He presents twelve well‐researched and readable case studies from both developed and developing countries. These are personal accounts of individual or collective actions to restore, protect and manage forest resources, with the common message that local initiatives and commitment are crucial. He clearly spells out that social and political change exert powerful forces on the forests of the world. However, the important point that he notes is that these may be either negative or positive, whereby the recovery of forests in Central Europe after sweeping social change serves as a powerful positive example.With this he also attempts to provide a new framework for the future by concentrating on what he sees as the most important forest preserving mechanisms. The first one is that local resistance to the exploitation and destruction of forests is crucial. The second is the important recognition that forests have a great capacity to regenerate naturally, a situation which ‘gloom and doom’ messages often neglect or even deny. Thirdly, he advocates that more attention should be paid to the possibilities of near‐natural forest management as a profitable option which still needs to gain full recognition.Whilst not being naive and whilst recognizing the powerful forces threatening forests, particularly in the developing world, this book provides a ray of sunshine and hope. This book is recommended to people interested in the future of forests. It suits both the more optimistic and the sceptical. For the former the book should help to reinforce their hope, and for the latter it may help convince them that not all is lost. For both it should provide a positive incentive to support the current movement towards greater involvement of local people in forest management.

Boreal Shield forest disturbance and recovery trends using Landsat time series

Effects of forest management on biodiversity in temperate deciduous forests: An overview based on Central European beech forests

In Central Europe, anthropogenic coniferous monocultures have been subject to conversion to more diverse mixed forests since the 1990s, however, they are still abundant across many forest landscapes. Artificial and natural tree regeneration both play a key role during conversion by determining the species composition and structure of the future forests. Many abiotic and biotic factors can potentially influence the regeneration process and its specific combinations or interactions may be different among tree species and its developmental stages. Here, we aimed to identify and quantify the effect of the most important drivers on the density of the most abundant regenerating tree species (i.e., Norway spruce and European beech), as well as on species and structural diversity of the tree regeneration. We studied tree regeneration in four former monospecific coniferous stand types (i.e., Norway spruce, Scots pine, European larch, and Douglas fir) in Southwest Germany that have been under conversion to mixed forests since the 1990s. We sampled tree regeneration in four growth height classes together with a variety of potentially influencing factors on 108 sampling plots and applied multivariate analyses. We identified light availability in the understorey, stand structural attributes, browsing pressure, and diaspore source abundance as the most important factors for the density and diversity of tree regeneration. Particularly, we revealed species-specific differences in drivers of regeneration density. While spruce profited from increasing light availability and decreasing stand basal area, beech benefited either from a minor reduction or more strikingly from an increase in overstorey density. Increasing diaspore source abundance positively and a high browsing pressure negatively affected both species equally. Our results suggest that humus and topsoil properties were modified during conversion, probably due to changes in tree species composition and silvicultural activities. The species and structural diversity of the tree regeneration benefitted from increasing light availability, decreasing stand basal area, and a low to moderate browsing pressure. We conclude that forest managers may carefully equilibrate among the regulation of overstorey cover, stand basal area, and browsing pressure to fulfil the objectives of forest conversion, i.e., establishing and safeguarding a diverse tree regeneration to promote the development of mature mixed forests in the future.

Forest recovery patterns in response to divergent disturbance regimes in the Border Lakes region of Minnesota (USA) and Ontario (Canada)

Recovery from forest disturbances is a pivotal metric of forest resilience. Forests globally are facing unprecedented levels of both natural and anthropogenic disturbances, yet our understanding of their recovery from these disturbances remains incomplete. Remote sensing is an effective tool for understanding post-disturbance recovery, but existing approaches largely rely on spectral recovery indicators that are difficult to interpret and require long time series after disturbance, which limits their applicability to recent disturbance pulses. We here introduce a novel, ecologically informed set of recovery indicators based on fractional cover maps derived from spectral unmixing analysis of Landsat and Sentinel-2 time series. We estimated annual pre- and post-disturbance tree cover and bare ground fractions over the eastern Alps (∼130,000 km2) for the period from 1990 to 2021. From these fraction time series, we derived recovery intervals defined as the time it takes to reach a pre-defined tree cover threshold after disturbance, referred to as canopy recovery. We found mean recovery intervals between 5.5 and 13.4 years, depending on recovery threshold and disturbance severity. Comparing our results to traditional remote sensing-based approaches of mapping forest recovery, we found that spectral unmixing-based recovery indicators give considerably more realistic recovery intervals than approaches based on spectral indices because they effectively distinguish tree regeneration from other post-disturbance vegetation (e.g., shrubs, grasses). Finally, we were able to accurately predict the long-term forest recovery success based on the information available only three years after disturbance, which underlines the high importance of a short window of reorganization post-disturbance, and highlights the utility of remote sensing to inform post-disturbance forest management (e.g., in identifying areas in need of tree planting). Our study thus provides an important step ahead in the remote sensing-based monitoring of forest recovery and resilience, which is urgently needed in a time of rapid forest change.

Context Climate change is increasing the frequency and severity of droughts worldwide, with profound consequences for forest ecosystems. Although previous studies suggest that taller forests are more vulnerable during drought, their capacity to recover following drought remains poorly understood, creating substantial uncertainty for forest management. Objectives This study aimed to quantify how canopy height influences post-drought forest recovery at a regional scale. Methods We investigated evergreen broad-leaved forests in southwest China following a severe drought in 2010. We used the MODIS Enhanced Vegetation Index (EVI) to derive forest recovery metrics, the Standardized Precipitation Evapotranspiration Index (SPEI) to classify drought severity, and a LiDAR-derived canopy height map. We then used linear regression and ANOVA to evaluate relationships between forest recovery and canopy height. Results Short-term (1 year) recovery increased with the intensity of the preceding drought. Under severe and extreme drought conditions, recovery increased significantly with canopy height ( p < 0.001). In contrast, long-term (3 years) recovery did not differ significantly among canopy height classes. Conclusions Our results indicated that although tall forests may experience greater drought impacts, they exhibit stronger short-term recovery, resulting in comparable long-term resilience across canopy-height classes. This size-dependent recovery dynamic is a previously underappreciated mechanism that should be incorporated into forest dynamics models and climate-adaptive management strategies.

Increasingly frequent and severe forest fires, exacerbated by warmer and drier conditions, significantly affect forest ecosystems. Understanding the dynamics of post-fire forest recovery is crucial for assessing forest resilience and guiding forest management. However, most post-fire recovery studies focus primarily on spatial variation, while recovery changes over time are relatively less studied. In this study, we examined the patterns, trends and drivers of spectral recovery from forest fires that burned between 2002 and 2018 in boreal and temperate forests. We used relative recovery indicators (RRIs) developed from three spectral indices-the normalized burn ratio, normalized difference vegetation index and near-infrared reflectance of vegetation-to capture post-fire spectral recovery. Our results showed that post-fire spectral recovery rates in temperate forests are faster than those in boreal forests, with quicker recovery in regions with higher percentages of broad-leaved species, less severe fires, higher temperature and precipitation. The decline in spectral forest recovery rates of boreal forests indicates that boreal forest post-fire recovery is becoming increasingly challenging. Our work provides valuable insights into forest management and conservation in the face of increasing fire frequency and intensity.This article is part of the theme issue 'Novel fire regimes under climate changes and human influences: impacts, ecosystem responses and feedbacks'.

<title>Abstract</title> Context Globally, climate change is increasing the frequency and severity of droughts, significantly impacting forest ecosystems. While previous studies suggest taller forests are more vulnerable during drought, their capacity to recover following drought remains poorly understood, creating uncertainty for forest management. Objectives This study aimed to quantify the role of canopy height in post-drought forest recovery and determine how its importance changes with drought severity at a regional scale. Methods We focused on evergreen broad-leaved forests in southwest China following a severe drought in 2010. We used MODIS EVI to define a forest recovery index, SPEI to classify drought severity, and a LiDAR-derived canopy height map. We then used linear regression and Random Forest models to analyze the relationships and the relative importance of contributing factors. Results Forest recovery was positively correlated with the intensity of the preceding drought. Under severe and extreme drought conditions, forest recovery increased significantly with canopy height (p &lt; 0.001). The relative importance of canopy height as a predictor of recovery also grew with drought intensity, increasing from 18.03% under normal conditions to 20.08% under extreme drought. Conclusions Our findings reveal that while tall forests may suffer more during severe droughts, they exhibit heightened recovery and resilience afterward. This size-dependent recovery dynamic is a critical and previously overlooked factor that should be incorporated into forest dynamic models and climate-adaptive resource management strategies.

Environmental heterogeneity on landslide slopes affects the long-term recoveries of forest ecosystem components

Introduction.- Dynamics in natural mixed-beech forest of the Upper Vosges D. Closset-Kopp et al.- The effects of climate change on the long-term conservation of Fagus grandifolia var. mexicana, an important species of the Cloud Forest in Eastern Mexico O. Tellez-Valdes et al.- Genetic diversity of Dalbergia monticola (Fabaceae) an endangered tree species in the fragmented oriental forest of Madagascar O. Andrianoelina et al.- Forest management and plant species diversity in chestnut stands of three Mediterranean areas H. Gonard et al.- Spatial diversity of dry savanna woodlands: Assessing the spatial diversity of a dry savanna woodland stand in northern Namibia using neighbourhood-based measures F.P. Graz.- Assessment of threat status and management effectiveness in Kakamega Forest, Kenya B. Bleher et al.- Influence of forest types and effects of forestry activities on species richness and composition of Chrysomelidae in the central mountainous region of Japan M. Ohsawa, T. Nagaike.- The banana forests of Kilimanjaro: biodiversity and conservation of the Chagga homegardens A. Hemp.- Biodiversity hotspots and conservation priorities in the Campo-Ma'an rain forests, Cameroon M.G.P. Tchouto et al.- Tree diversity in western Kenya: using profiles to characterise richness and evenness R. Kindt et al.- Vascular plant species inventory of a Philippine lowland rain forest and its conservation value G. Langenberger et al.- Status and conservation of Trigonobalanus doichangensis (Fagaceae) W. Sun et al.- Ghyll woodlands of the Weald: characterisation and conservation N.G. Burnside et al.- Effects of fragmentation of evergreen broad-leaved forests on genetic diversity of Ardisia crenata var. bicolor (Myrsinaceae) A.-L. Zhao et al.- Diversity patterns in theflora of the Campo-Ma'an rain forest, Cameroon: do tree species tell it all? M.G.P. Tchouto et al.- Impacts of selective logging and agricultural clearing on forest structure, floristic composition and diversity, and timber tree regeneration in the Ituri Forest, Democratic Republic of Congo J.-R. Makana, S.C. Thomas.- Forest management considerations for conservation of Black Woodpecker Dryocopus martius and White-backed Woodpecker Dendrocopos leucotos populations in Quinto Real (Spanish Western Pyrenees) A. Garmendia et al.- A reconsideration of the reproductive biology of the Atlantic forest in the Volta Velha Reserve S.M. Vamosi.- Patterns of rodent species diversity and abundance in a Kenyan relict tropical rainforest A. Mortelliti, L. Boitani.- The role of landscape patterns of habitat types on plant species diversity of a tropical forest in Mexico J.L. Hernandez-Stefanoni.-Distribution, habitat and Red List status of the New Caledonian endemic tree Canacomyrica monticola (Myricaceae) J. Herbert.- Composition of woody species in a dynamic forest-woodland-savannah mosaic in Uganda: implications for conservation and management G. Nangendo et al.- Do Orthoptera need human land use in Central Europe? The role of habitat patch size and linear corridors in the Bialowieza Forest, Poland J. Theuerkauf, S. Rouys.- Species composition, diversity and local uses of tropical dry deciduous and gallery forests in Nicaragua B. Gonzalez-Rivas et al.- Identifying conservation priority zones for effective management of tropical forests in Eastern Ghats of India B. Balaguru et al.- Comparison of bird communities in primary vs. young secondary tropical montane cloud forest in Guatemala S.C. Renner et al.- Effects of habitat structure and adjacent habitats on birds in tropical rainforest fragments and shaded

Natural dynamics of temperate mountain beech-dominated primary forests in Central Europe

Early natural tree regeneration after wildfire in a Central European Scots pine forest: Forest management, fire severity and distance matters

Key messageWe applied a modified forest gap model (ForClim) to depict changes in stand water transpiration via density reduction as a forest adaptation strategy. This approach is the key to analyzing the ecological resilience to drought, stress-induced mortality, and economic efficiency of managed mixed forest stands in Central Europe. The results show that specific geographic conditions and forest composition define the optimal stand density of drought-resilient forests.ContextReducing stand density has been recognized as a valid strategy to increase forest resilience to drought. Moreover, to develop adaptive management strategies (AMS) under climate change, it is crucial to consider not only drought resilience but also the economic efficiency of alternative AMS proposed to alleviate drought effects.AimsTo analyze how decreased inter-tree competition among overstorey trees affects stand vulnerability to drought and its expected yield.MethodsWe integrated experimental thinning data and historical responses to drought years in a climate-sensitive forest gap model, ForClim. We tested a business as usual (BAU) and three alternative AMS (“do-nothing,” low- and high-intensity overstorey removal) in mixed stands of Norway spruce (Picea abies), silver fir (Abies alba), and European beech (Fagus sylvatica) along an elevational gradient of 520–1020 m a.s.l. in Central Europe.ResultsHigh-intensity overstorey removal in mixed stands of all three species considerably increased forest volume growth resilience to drought and decreased stress-induced mortality by two-thirds vis à vis a “do-nothing” strategy. In sites including only conifer species, forest resilience was equally improved by high- and low-intensity overstorey removal compared to that in the BAU strategy. Regarding the timber economy, high-intensity overstorey removal resulted in a higher economic revenue of mixed stands (~ 22% higher net present value than other strategies) on the high-elevation sites (> 1000 m a.s.l.).ConclusionModifying forest density and structure by overstorey removal is principally suitable to increase forest resilience to drought and improve its economic efficiency. The magnitude of the effect however depends on the geographical setting and forest composition.

Global change is altering the state of forest ecosystems, threatening their integrity. A number of studies have reported declines in aboveground arthropod diversity over the last decade and indicated management practices or climate as the main drivers. However, belowground communities have rarely been studied in this context, and the extent to which patterns and associated drivers observed aboveground also apply to belowground communities remains unknown. Therefore, research is urgently needed to disentangle the drivers and potential threats that shape soil animal communities, which contribute significantly to the functioning of terrestrial ecosystems by providing key ecosystem functions such as decomposition and nutrient cycling. Here, we studied soil animal communities across forest types of different management intensity, including unmanaged beech forests, managed age-class beech forests and spruce monoculture plantations across three regions located in southern, central, and northern Germany, i.e., Swabian Alb, Hainich-Dün, and Schorfheide-Chorin. We first investigated the spatiotemporal dynamics of oribatid mites (Acari: Oribatida), sampled in three-year intervals from 2008 – 2020 (Chapter 2). In contrast to the linear decline in diversity observed aboveground, oribatid mite density and diversity decreased after years with low preceding winter precipitation and recovered after years with higher precipitation. This correlation differed between regional soil types and was only found in the Swabian Alb and Schorfheide-Chorin, where soil fauna is more susceptible to periodic droughts due to the shallow Rendzinas and sandy soils, respectively. Temporal dynamics were similar between managed and unmanaged forests, suggesting that forestry has little effect on the viability of oribatid mite populations in Central European forests. To gain a more mechanistic understanding of the effects of extensive forest management, we then examined oribatid mite communities one year after two key characteristics of forest management; namely forest gap formation and deadwood availability were manipulated in a full factorial experiment (Chapter 3). We found that both deadwood and forest gap formation significantly affected oribatid mite density and community composition, although the magnitude of these effects differed between regions. One year after deadwood addition, oribatid mite density approximately doubled in the Hainich-Dün, mainly due to a few fast-reproducing species. Presumably, they benefitted from additional microbial resources near deadwood, particularly fungi, which are the prime resource of oribatid mites as shown in Chapter 4. By contrast, forest gap formation reduced the density and diversity of oribatid mites but only in the Swabian Alb and Schorfheide-Chorin. Given the strong correlation between oribatid mite density and precipitation found in these two regions in Chapter 2, it is likely that periodic droughts were aggravated in forest gaps, adversely affecting oribatid mite communities. Notably, negative effects of forest gap formation were not mitigated by the addition of deadwood, indicating that harsh environmental conditions override the positive effects of additional resources. Finally, we linked the dynamics of soil animal communities to their function in the soil food web by analyzing trophic niches of detritivores (Oribatida, Collembola, Diplopoda, Isopoda, Lumbricidae) and predators (Mesostigmata, Chilopoda) across forest types and regions. Trophic niches were derived by analyzing the relative contribution of plants, fungi, and bacteria used as basal resources and estimating trophic positions, using community-level compound-specific stable isotope analysis of amino acids (Chapter 4). Results showed that soil animal detritivores in forests mainly feed on fungi, followed by plants and to a lesser extent on bacteria. Relative proportions of basal resources were consistent across forest types and regions for all taxa. Notably, Chilopoda obtained more essential amino acids from bacteria than other investigated taxa, suggesting that they prey on soil animals not included in the study. Enchytraeidae are known to serve as prey for Chilopoda and have recently been shown to feed on bacteria. Trophic positions were higher in the Schorfheide-Chorin for Oribatida and Collembola but decreased for Lumbricidae. This may in part be related to regional differences in community composition, as shown for oribatid mites in Chapters 2 & 3. Also, increasing trophic positions suggest longer trophic chains, which may be explained by the integration of more root-derived resources and/or rhizosphere prey, due to higher root density in the organic layers of sandy soils. The results of this thesis show that the dynamics of oribatid mite communities are little affected by forest management and are mostly determined by abiotic conditions at regional scales. However, more extensive forest management events, such as the formation of forest gaps, may interact with regional abiotic stressors, leading to aggravated effects on oribatid mites. The thesis also provides the first evidence that fungi are the main resource for mesofauna and macrofauna detritivores and that trophic niches in soil are conserved between forest types of different management intensity. Future studies need to assess the generality of these findings and further explore the complex interactions between forest management practices and regional abiotic factors.