Ten Years of Adaptive Silviculture for Climate Change: An Applied, Coproduced Experimental Framework

With 207 million ha of forest covering 22% of its land area, China ranks fifth in the world in forest area. Rapid economic growth, climate change, and forest disturbances pose new, complex challenges for forest research and management. Progress in meeting these challenges is relevant beyond China, because China's forests represent 34% of Asia's forests and 5% of the worlds' forests. To provide a broader understanding of these management challenges and of research and policies that address them, we organized this special issue on contemporary forest research and management issues in China. At the national level, papers review major forest types and the evolution of sustainable forestry, the development of China's forest-certification efforts, the establishment of a forest inventory system, and achievements and challenges in insect pest control in China. Papers focused on Northern China address historical, social, and political factors that have shaped the region's forests; the use of forest landscape models to assess how forest management can achieve multiple objectives; and analysis and modeling of fuels and fire behavior. Papers addressing Central and South China describe the "Grain for Green" program, which converts low productivity cropland to grassland and woodland to address erosion and soil carbon sequestration; the potential effects of climate change on CO(2) efflux and soil respiration; and relationships between climate and net primary productivity. China shares many forest management and research issues with other countries, but in other cases China's capacity to respond to forest management challenges is unique and bears watching by the rest of the world.

Anthropogenic global warming is creating new challenges for forest management in many parts of the world. One vital aspect is the choice of tree species and whether to cultivate monospecific or mixed timber plantations. Because Central Germany applies close-to-nature forest management, each piece of land needs to fulfil multiple services, including timber production and biodiversity conservation. However, scientific understanding of the effect of forest type on ecosystem functioning, especially decomposer communities, is still limited. To better understand the linkages between forest types and decomposer communities, I investigated decomposer communities in pure and mixed forests of native European beech, range-expanding Norway spruce, and non-native Douglas fir across a range of environmental conditions. Based on a review of previous work (Chapter 1). I developed the overarching hypothesis that, compared to native European beech, Douglas fir detrimentally affects the community structure of decomposers. Further, available data suggest that mixed forests may mitigate the adverse effects of pure coniferous forests. To test these hypotheses, I first investigated the structure and functioning of microbial communities using microbial respiration and phospholipid-derived fatty acid analyses (Chapter 2). The response of microbial community structure and functional indicators depends strongly on soil nutrient concentrations in the study site. Douglas fir and Norway spruce adversely affected soil microbial communities and compromised their functioning, particularly in unfavorable environments. These findings, published in Lu and Scheu 2021, call for caution when deciding whether to plant pure Douglas fir under less-favorable site conditions and overall contribute to a context-wise understanding of tree–soil interactions. Building on the concept of microbial communities as basal resources connecting trees and soil animals, I next investigated collembolans and oribatid mites in association with biotic and abiotic environmental variables (Chapter 3). Species composition of Oribatida, but not of Collembola, sensitively responded to forest type, differing most between Douglas-fir and European-beech forests. Although microarthropod richness and diversity did not differ among forest types, the abundance of both euedaphic Collembola and predatory Oribatida were lower in Douglas fir than in European beech, presumably due to lower provisioning of root-associated resources in Douglas-fir forests. The results suggest that non-native Douglas fir generally does not affect the diversity of soil microarthropods, but the limitation of root-derived resources may restrict the population development of some microarthropods in Douglas-fir forests. To further understand the intraspecific variation in food resources of oribatid mites, stable isotope ratios of 15N/14N and 13C/12C were quantified for 40 Oribatida species that occur in both litter and soil (Chapter 4). Across five forest types, Oribatida species were found to occupy virtually identical trophic niches irrespective of the soil depth at which they were recovered. Such low intraspecific variability may facilitate Oribatida niche differentiation and species coexistence. These findings are an important contribution to the understanding of the trophic ecology of oribatid mites in temperate forest ecosystems. Although basal resources of Oribatida vary between coniferous and deciduous forests, basal resources and trophic positions of Oribatida species in mixed forests are similar to those in European beech, supporting the use of mixed forests in mitigating adverse impacts of coniferous trees. Taken together, my results suggest that tree identity is an important driver for microbial and microarthropod communities. In mixed forests, microbial and microarthropod responses are intermediate compared to respective pure stands, suggesting that tree species are singular, that is, loss or addition of tree species causes detectable changes. Furthermore, the microbial response also depends on site conditions and mixture types, reflecting different responses of the tree species to environmental conditions. This also supports the idea that mixed forests provide better insurance against the changing climate (Chapter 5). Overall, mixed forests help to maintain soil microbial and microarthropod communities close to the state of native European-beech forests and mitigate the adverse impacts of coniferous forests. As a whole, this dissertation contributes to a better understanding of the structure and resource utilization of soil decomposer communities and serves as a stepping stone for the next phase of the research training group.

Managing the forest-water nexus for climate change adaptation

Potential climate change impacts on water resources have been extensively assessed in Norway due to substantial changes in climate in the recent decades. However, the combined and isolated effects of forest and forest management have been rarely considered in the climate impact studies in Norway although about 38% of the land area is covered by forest. This study aims to improve hydrological impact projections in forest dominant catchments by considering the effects of forest growth and management and to attribute hydrological changes to climate and forest changes. The eco-hydrological model SWIM (Soil and Water Integrated Model) was applied to simulate hydrological processes and extremes for two micro-scale, two meso-scale and two macro-scale catchments, accounting for the effects of spatial scale. The climate projections were generated by three EURO-CORDEX (Coordinated Downscaling Experiment for the European domain) regional climate models (RCMs) for two RCPs (Representative Concentration Pathways, RCP2.6 and RCP4.5) and were bias corrected using the quantile-mapping method. Forest development over time was simulated as a function of climate determining growth and SSP-dependent harvest levels determining wood outtake. The simulations were initialized with the forest status of the year 2020 and different forest types are distinguished according to structural characteristics represented by three key parameters: leaf area index, mean tree height and surface albedo. Preliminary simulation results show that there are minor changes (within ±5%) in hydrological processes under the combinations of the climate and forest scenarios for these catchments. Climate change is the major driver of hydrological change at the catchment scale whereas forest development mainly influences the spatial distribution of the hydrological fluxes. The results further indicate that forest growth under a warming climate helps to reduce the risk of the floods and drought slightly by reducing surface runoff in wet periods and increasing base flow in dry periods, respectively.

Standing deadwood is an important structural component of forest ecosystems. Its occurrence and dynamics influence both carbon fluxes and the availability of habitats for many species. However, deadwood is greatly reduced in managed, and even in many currently unmanaged temperate forests in Europe. To date, few studies have examined how environmental factors, forest management and changing climate affect the availability of standing deadwood and its dynamics.Data from five periods of the Austrian National Forest Inventory (1981-2009) were used to (I) analyse standing deadwood volume in relation to living volume stock, elevation, eco-region, forest type, ownership and management intensity, (II) investigate the influence of forest ownership and management intensity on snag persistence and (III) define drivers of standing deadwood volume loss for seven tree genera (Abies, Alnus, Fagus, Larix, Picea, Pinus and Quercus) using tree-related, site-related and climate-related variables, and predict volume loss under two climate change scenarios.Standing deadwood volume was mainly determined by living volume stock and elevation, resulting in different distributions between eco-regions. While forest type and management intensity influenced standing deadwood volume only slightly, the latter exhibited a significant effect on persistence. Snag persistence was shorter in intensively managed forests than in extensively managed forests and shorter in private than in public forests.Standing deadwood volume loss was driven by a combination of diameter at breast height, elevation, as well as temperature, precipitation and relative humidity. Volume loss under climate change predictions revealed constant rates for moderate climate change (RCP2.6) by the end of the 21st century. Under severe climate change conditions (RCP8.5), volume loss increased for most tree genera, with Quercus, Alnus and Picea showing different predictions depending on the model used as the baseline scenario. We observed trends towards faster volume loss at higher temperatures and lower elevations and slower volume loss at high precipitation levels. The tree genera most susceptible to climate change were Pinus and Fagus, while Abies was least susceptible. Synthesis and applications. We recommend to protect standing dead trees from regular harvesting to ensure the full decomposition process. The consequences for decomposition-dependent species must be taken into account to evaluate the influences of management and climate change on standing deadwood dynamics.

Key message Adaptation of forest management to climate change requires an understanding of the effects of climate on forests, industries and communities; prediction of how these effects might change over time; and incorporation of this knowledge into management decisions. This requires multiple forms of knowledge and new approaches to forest management decisions. Partnerships that integrate researchers from multiple disciplines with forest managers and local actors can build a shared understanding of future challenges and facilitate improved decision making in the face of climate change. Context Climate change presents significant potential risks to forests and challenges for forest managers. Adaptation to climate change involves monitoring and anticipating change and undertaking actions to avoid the negative consequences and to take advantage of potential benefits of those changes. Aims This paper aimed to review recent research on climate change impacts and management options for adaptation to climate change and to identify key themes for researchers and for forest managers. Methods The study is based on a review of literature on climate change impacts on forests and adaptation options for forest management identified in the Web of Science database, focusing on papers and reports published between 1945 and 2013. Results One thousand one hundred seventy-two papers were identified in the search, with the vast majority of papers published from 1986 to 2013. Seventy-six percent of papers involved assessment of climate change impacts or the sensitivity or vulnerability of forests to climate change and 11 % (130) considered adaptation. Important themes from the analysis included (i) predicting species and ecosystem responses to future climate, (ii) adaptation actions in forest management, (iii) new approaches and tools for decision making under uncertainty and stronger partnerships between researchers and practitioners and (iv) policy arrangements for adaptation in forest management. Conclusions Research to support adaptation to climate change is still heavily focused on assessing impacts and vulnerability. However, more refined impact assessments are not necessarily leading to better management decisions. Multi-disciplinary research approaches are emerging that integrate traditional forest ecosystem sciences with social, economic and behavioural sciences to improve decision making. Implementing adaptation options is best achieved by building a shared understanding of future challenges among different institutions, agencies, forest owners and stakeholders. Research-policy-practice partnerships that recognise local management needs and indigenous knowledge and integrate these with climate and ecosystem science can facilitate improved decision making.

Sustainability in forest management and a new role for resilience thinking

The combination of climate change and anthropogenic disturbance significantly impacts forest bird assemblages. Assessing the cumulative effects of forest management and climate change on biodiversity and ecosystem services, including carbon sequestration and storage and provisioning of wood products is key to informing forest management and conservation decision making. Specifically, we projected changes in forest composition and structure according to various forest management strategies under a changing climate using LANDIS-II for two case study areas of Quebec (Canada): a hemiboreal (Hereford Forest) and a boreal (Montmorency Forest) area. Then, we assessed projected bird assemblage changes, as well as sensitive and at-risk species. As part of an integrated assessment, we evaluated the best possible management measures aimed at preserving avian diversity and compared them with optimal options for mitigation of carbon emissions to the atmosphere. Forest management and climate change were projected to lead to significant changes in bird assemblages in both types of forest through changes in forest composition. We projected an increase in deciduous vegetation which favored species associated with mixed and deciduous stands to the detriment of species associated with older, coniferous forests. Changes were more pronounced in Hereford Forest than Montmorency Forest. In addition, Hereford’s bird assemblages were mainly affected by climate change, while those in Montmorency Forest were more impacted by forest management. We estimated that 25% of Hereford and 6% of Montmorency species will be sensitive to climate change, with projected abundance changes (positive or negative) exceeding 25%. According to the simulations, a decrease in the level of forest harvesting could benefit bird conservation and contribute to reduction of carbon emissions in the boreal forest area. Conversely, the hemiboreal forest area require trade-offs, as mitigation of carbon emissions is favored by more intensive forest management that stimulates the growth and carbon sequestration of otherwise stagnant stands.

Climate change is altering disturbance regimes and recovery rates of forests globally. The future of these forests will depend on how climate change interacts with management activities. Forest managers are in critical need of strategies to manage the effects of climate change. We co‐designed forest management scenarios with forest managers and stakeholders in the Klamath ecoregion of Oregon and California, a seasonally dry forest in the Western US subject to fire disturbances. The resultant scenarios span a broad range of forest and fire management strategies. Using a mechanistic forest landscape model, we simulated the scenarios as they interacted with forest growth, succession, wildfire disturbances and climate change. We analysed the simulations to (a) understand how scenarios affected the fire regime and (b) estimate how each scenario altered potential forest composition. Within the simulation timeframe (85 years), the scenarios had a large influence on fire regimes, with fire rotation periods ranging from 60 years in a minimal management scenario to 180 years with an industrial forestry style management scenario. Regardless of management strategy, mega‐fires (>100,000 ha) are expected to increase in frequency, driven by stronger climate forcing and extreme fire weather. High elevation conifers declined across all climate and management scenarios, reflecting an imbalance between forest types, climate and disturbance. At lower elevations (<1,800 m), most scenarios maintained forest cover levels; however, the minimal intervention scenario triggered 5 × 105 ha of mixed conifer loss by the end of the century in favour of shrublands, whereas the maximal intervention scenario added an equivalent amount of mixed conifer. Policy implications. Forest management scenarios that expand beyond current policies—including privatization and aggressive climate adaptation—can strongly influence forest trajectories despite a climate‐enhanced fire regime. Forest management can alter forest trajectories by increasing the pace and scale of actions taken, such as fuel reduction treatments, or by limiting other actions, such as fire suppression.

Besides offering numerous important ecosystem services, sustainably managed forests can help reduce atmospheric CO2 concentrations and thus mitigate climate change. Forest-based mitigation occurs through the carbon sink in the forest itself, the carbon sink in wood products, and through substitution effects when wood products replace carbon-intensive materials and fuels.The relative importance of each of these three mitigation dimensions depends on a multitude of factors. First, forest type and structure, site conditions, and climate change and associated disturbances determine the amount of carbon that may be sequestered over the next decades at a given site. Second, the type and intensity of management determines the trade-off between on-site carbon sequestration and carbon storage in wood products. Third, management, wood usage patterns, and the carbon-intensity of the economy determine the amount of avoided emissions via substitution effects.To assess their impact on the total forest mitigation potential, we conducted a factorial modeling experiment by varying all of the aforementioned factors. Specifically, we looked at the forest type (needle-leaved vs broad-leaved) and age (young vs mature), increased and decreased harvest intensities, increased material wood usage and cascading, decarbonization rates, climate change and disturbance scenarios, and salvage logging practices after disturbance.Under an assumed "closer-to-nature forest management" our results show a higher mitigation potential of young forests compared to mature forests, whereas the forest type does not have a clear effect. The importance of substitution effects outweighs the importance of the forest and product carbon sink on shorter time scales. This changes towards the end of the century, assuming that substitution effects decrease because the substituted materials can be produced in a less carbon-intensive way. Increases in harvest intensity consequently are also only beneficial for climate change mitigation on these shorter time scales, though they likely have adverse effects on other ecosystem services. Our results also show that increased material usage (as opposed to energy usage) of wood can be an important lever for mitigation. Finally, changes in disturbances strongly affect the mitigation potential, though the mitigation impact of a subsequent salvaging operation heavily depends on the forest type and the product portfolio created from the salvaged wood.In conclusion, our results quantify the impacts and interactions of the different factors that govern forest-based mitigation, while highlighting the complexity of the topic and the importance of the considered time-scales.

This chapter presents an overview on historical and current forestry and forest management in China. Although China’s natural forests had greatly reduced over the past several centuries due mainly to agricultural development, over-exploration and wars, there has been a sustained growth in total forest area and volume for several decades partly because of the implementation of several national key forestry programs aiming at biodiversity conservation and sustainable forestry development. China’s forest resource today is still insufficient because of low quality and productivity, and inadequate forest management. The major problems of forest management in China include deficiency in linking forest management with end usage, inadequate forest health management, lack of integrated forest landscape management, and unbalanced consideration on economy over environment. Forest management must address increasing concerns on challenges and emerging global issues, of which climate change is identified as the most severe threat. To tackle the existing problems and cope with uncertainties in changing environmental conditions with climate change, landscape ecology can play a major role in facilitating sustainable forest management (SFM) by providing theories and management tools for forest restoration, biodiversity conservation, land and water resource management and forest landscape planning. Forest management practices that consider spatial heterogeneity, pattern-process, disturbance regime, scale and spatial-temporal context of forest landscapes beyond forest boundary are increasingly adopted by forest researchers and managers in China. However, more research is needed to enhance long-term forest ecosystem monitoring, develop cross-scale and multiple-purpose forest management guidelines, improve landscape decision support systems, and formulate integrated ecosystem management policies and practices so that forest landscape management can be adapted to climate change and landscape sustainability can be strengthened.

Synchronised disturbances in spruce- and beech-dominated forests across the largest primary mountain forest landscape in temperate Europe

Forest stressors and roadside vegetation management in an exurban landscape

The ability of forests to continuously provide ecosystem services (ES) is threatened by rapid changes in climate and disturbance regimes. Consequently, these changes present a considerable challenge for forest managers. Management of forests often focuses on maximizing the level of ES provisioning over extended time frames (i.e., rotation periods of more than 100 yr). However, temporal stability is also crucial for many ES, for example, in the context of a steady provisioning of resources to the industry, or the protection of human infrastructure against natural hazards. How temporal stability and the level of ES provisioning are related is of increasing interest, particularly since changing climate and disturbance regimes amplify temporal variability in forest ecosystems. In this simulation study, we investigated whether forest management can simultaneously achieve high levels and temporal stability of ES provisioning. Specifically, we quantified (1) trade‐offs between ES stability and level of ES provisioning, and (2) the effect of tree species diversity on ES stability. Simulating a wide range of future climate scenarios and management strategies, we found a negative relationship between temporal stability and level of ES provisioning for timber production, carbon cycling, and site protection in a landscape in the Austrian Alps. Tree species diversity had a predominantly positive effect on ES stability. We conclude that attempts to maximize the level of ES provisioning may increase its temporal variability, and thus threaten the continuity of ES supply. Consequently, considerations of stability need to be more explicitly included in forest management planning under increasingly variable future conditions.

It is critical to study how different forest management practices affect forest carbon sequestration under global climate change regime. Previous researches focused on the stand-level forest carbon sequestration with rare investigation of forest carbon stocks influenced by forest management practices and climate change at regional scale. In this study, a general integrative approach was used to simulate spatial and temporal variations of woody biomass and harvested biomass of forest in China during the 21st century under different scenarios of climate and CO2 concentration changes and management tasks by coupling Integrated Terrestrial Ecosystem Carbon budget (InTEC) model with Global Forest Model (G4M). The results showed that forest management practices have more predominant effects on forest stem stocking biomass than climate and CO2 concentration change. Meanwhile, the concurrent future changes in climate and CO2 concentration will enhance the amounts of stem stocking biomass in forests of China by 12%–23% during 2001–2100 relative to that with climate change only. The task for maximizing stem stocking biomass will dramatically enhance the stem stocking biomass from 2001–2100, while the task for maximum average increment will result in an increment of stem stocking biomass before 2050 then decline. The difference of woody biomass responding to forest management tasks was owing to the current age structure of forests in China. Meanwhile, the sensitivity of long-term woody biomass to management practices for different forest types (coniferous forest, mixed forest and deciduous forest) under changing climate and CO2 concentration was also analyzed. In addition, longer rotation length under future climate change and rising CO2 concentration scenario will dramatically increase the woody biomass of China during 2001–2100. Therefore, our estimation indicated that taking the role of forest management in the carbon cycle into the consideration at regional or national level is very important to project the forest carbon sequestration under future climate change and rising atmospheric CO2 concentration.