Felicitas Suckow

Climate change and European forests: What do we know, what are the uncertainties, and what are the implications for forest management?

The knowledge about potential climate change impacts on forests is continuously expanding and some changes in growth, drought induced mortality and species distribution have been observed. However despite a significant body of research, a knowledge and communication gap exists between scientists and non-scientists as to how climate change impact scenarios can be interpreted and what they imply for European forests. It is still challenging to advise forest decision makers on how best to plan for climate change as many uncertainties and unknowns remain and it is difficult to communicate these to practitioners and other decision makers while retaining emphasis on the importance of planning for adaptation. In this paper, recent developments in climate change observations and projections, observed and projected impacts on European forests and the associated uncertainties are reviewed and synthesised with a view to understanding the implications for forest management. Current impact assessments with simulation models contain several simplifications, which explain the discrepancy between results of many simulation studies and the rapidly increasing body of evidence about already observed changes in forest productivity and species distribution. In simulation models uncertainties tend to cascade onto one another; from estimating what future societies will be like and general circulation models (GCMs) at the global level, down to forest models and forest management at the local level. Individual climate change impact studies should not be uncritically used for decision-making without reflection on possible shortcomings in system understanding, model accuracy and other assumptions made. It is important for decision makers in forest management to realise that they have to take long-lasting management decisions while uncertainty about climate change impacts are still large. We discuss how to communicate about uncertainty - which is imperative for decision making - without diluting the overall message. Considering the range of possible trends and uncertainties in adaptive forest management requires expert knowledge and enhanced efforts for providing science-based decision support.

Projections of regional changes in forest net primary productivity for different tree species in Europe driven by climate change and carbon dioxide

Abstract• ContextProjecting changes in forest productivity in Europe is crucial for adapting forest management to changing environmental conditions.• AimsThe objective of this paper is to project forest productivity changes under different climate change scenarios at a large number of sites in Europe with a stand-scale process-based model.• MethodsWe applied the process-based forest growth model 4C at 132 typical forest sites of important European tree species in ten environmental zones using climate change scenarios from three different climate models and two different assumptions about CO2 effects on productivity.• ResultsThis paper shows that future forest productivity will be affected by climate change and that these effects depend strongly on the climate scenario used and the persistence of CO2 effects. We find that productivity increases in Northern Europe, increases or decreases in Central Europe, and decreases in Southern Europe. This geographical pattern is mirrored by the responses of the individual tree species. The productivity of Scots pine and Norway spruce, mostly located in central and northern Europe, increases while the productivity of Common beech and oak in southern regions decreases. It is important to note that we consider the physiological response to climate change excluding disturbances or management.• ConclusionsDifferent climate change scenarios and assumptions about the persistence of CO2 effects lead to uncertain projections of future forest productivity. These uncertainties need to be integrated into forest management planning and adaptation of forest management to climate change using adaptive management frameworks.

Multiple-use forest management in consideration of climate change and the interests of stakeholder groups

In this study, the overall utility of forest management alternatives at the forest management unit level is evaluated with regard to multi-purpose and multi-user settings by a multi-criteria analysis (MCA) method. The MCA is based on an additive utility model. The relative importance of partial objectives of forest management (carbon sequestration, ground water recharge, biodiversity, and timber production) is defined in cooperation with stakeholders. The forest growth model 4C (Forest Ecosystems in a Changing Environment) is used to simulate the impact of six forest management strategies and climate on forest functions. Two climate change scenarios represent uncertainties with regard to future climatic conditions. The study is based on actual forest conditions in the Kleinsee management unit in east Germany, which is dominated by Scots pine (Pinus sylvestris L.) and oak (Quercus robur L. and Quercus petraea Liebl.) stands. First, there is an analysis of the impact of climate and forest management on forest functions. Climate change increases carbon sequestration and income from timber production due to increased stand productivity. Secondly, the overall utility of the management strategies is compared under the priority settings of different stakeholder groups. From an ecological perspective, a conservation strategy would be preferable under all climate scenarios, but the business as usual management would also fit the expectations under the current climate due to high biodiversity and carbon sequestration in the forest ecosystem. In contrast, a forest manager in public-owned forests or a private forest owner would prefer a management strategy with an intermediate thinning intensity and a high share of pine stands to enhance income from timber production while maintaining the other forest functions.

Parameter and input data uncertainty estimation for the assessment of long-term soil organic carbon dynamics

The use of integrated soil organic matter (SOM) models to assess SOM dynamics under climate change, land use change and different land management practices require a quantification of uncertainties and key sensitive factors related to the respective modelling framework. Most uncertainty studies hereby focus on model parameter uncertainty, neglecting other sources like input data derived uncertainties, and spatial and temporal properties of uncertainty. Sources of uncertainties assessed in this study stem from uncertainties in model parameterisation and from uncertainties in model input data (climate, soil data, and land management assumptions). Thereby, Monte Carlo based global sensitivity and uncertainty analysis using a latin hypercube stratified sampling technique was applied to derive plot scale (focusing on temporal propagation) and river basin scale propagation of uncertainty for long-term soil organic carbon (SOC) dynamics. The model used is the eco-hydrological river basin model SWIM (Soil and Water Integrated Model), which has been extended by a process-based multi-compartment model for SOM turnover. Results obtained by this study can be transferred and used in other simulation models of this kind. Uncertainties resulting from all input factors used (model parameters+model input data) show a coefficient of variation between 5.1 and 6.7% and accounted for+/-0.065 to+/-0.3% soil carbon content (0.06-0.15t Cha^-^1yr^-^1). Parameter derived uncertainty contributed most to overall uncertainty. Concerning input data contributions, uncertainties stemming from soil and climate input data variations are striking. At the river basin scale, cropland and forest ecosystems, loess and gleyic soils possess the highest degree of uncertainty. Quantified magnitudes of uncertainty stemming from the examined sources vary temporally and spatially due to specific natural settings (e.g. climate, land use and soil properties) and deliver useful information for interpreting simulation results on long-term soil organic carbon dynamics under environmental change. Derived from this analysis, key sensitive model parameters and interactions between them were identified: the mineralization rate coefficient, the carbon use efficiency parameter (synthesis coefficient) along with parameters determining the soil temperature influence on SOM turnover (mainly Q10 value) and the soil input related data (soil bulk density and initial soil C content) introduced the highest degree of model uncertainty. The here gained information can be transferred to other process-based SOM turnover models to consider stronger most crucial parameters introducing highest uncertainty contribution to soil C storage assessment under changing environmental conditions.

A New Forest Gap Model to Study the Effects of Environmental Change on Forest Structure and Functioning

Current forest gap models suffer from a number of deficiencies, as outlined in the literature. In this paper we present a new forest gap model that is constructed based on recent ecological and evolutionary theories about the functioning of plant communities. The model contains improved formulations of (1) water and nutrient availability in the soil; (2) the annual course of net photosynthesis; (3) carbon allocation patterns, (4) establishment and mortality rates, and (5) incorporation of management and natural disturbances at the scale of the individual tree and at the landscape scale. Preliminary simulation results for an individual tree and a single-species stand are presented and discussed.

Regional impact analysis of climate change on natural and managed forests in the Federal State of Brandenburg, Germany

A methodology for regional application of forest simulation models has been developed as part of an assessment of possible climate change impacts in the Federal state of Brandenburg (Germany). Here we report on the application of a forest gap model to analyse the impacts of climate change on species composition and productivity of natural and managed forests in Brandenburg using a statistical method for the development of climate scenarios. The forest model was linked to a GIS that includes soil and groundwater table maps, as well as gridded climate data with a resolution of 10 × 10 km and simulated a steady-state species composition which was classified into forest types based on the biomass distribution between species. Different climate scenarios were used to assess the sensitivity of species composition to climate change. The simulated forest distribution patterns for current climate were compared with a map of Potential Natural Vegetation (PNV) of Brandenburg.In order to analyse the possible consequences of climate change on forest management, we used forest inventory data to initialize the model with representative forest stands. Simulation experiments with two different management strategies indicated how forest management could respond to the projected impacts of climate change. The combination of regional analysis of natural forest dynamics under climate change with simulation experiments for managed forests outlines possible trends for the forest resources. The implications of the results are discussed, emphasizing the regional differences in environmental risks and the adaptation potentials of forestry in Brandenburg.

Integrating dynamic morphological properties into forest growth modelling I. Effects on water balance and gas exchange

Abstract A physiologically-based forest growth model is used to investigate the sensitivity of the water balance and photosynthesis of Scots pine ( Pinus sylvestris L.) plantations in eastern Germany to changes in leaf area, vertical fine root distribution and ground vegetation competition. Simulation results suggest that these changes can have distinct effects on stand development. When the annual maximum leaf area index (LAI) is varied between 2.5 and 4.5, annual evapotranspiration and net primary production increases by 20–50% in the investigated stands, depending on the weather in the individual years. The contribution of ground vegetation to total evapotranspiration was found to be approximately 30% and thus should not be neglected in water balance calculations. Sapwood water storage determines peak transpiration, and vertical fine root distribution has been shown to affect the length of drought periods. Both factors can have a considerable effect on water availability to trees. As an example for a long-term assessment, the annual water balance of a managed pine forest is calculated under realistic weather and deposition conditions through a 27-year period, including the simulation of changes in stand density, LAI and ground vegetation. The importance of stand dynamics is discussed with respect to water balance calculations in the context of forest damage and climatic warming.

Integrated assessment of cropland soil carbon sensitivity to recent and future climate in the Elbe River basin

Abstract Carbon storage in soils is sensitive to changing climatic conditions, potentially increasing C fluxes from soils to the atmosphere. This study provides an assessment of recent climate variability (1951–2000) and potential future (2001–2055) climate change impacts on soil C storage for croplands in the German part of the Elbe River basin. Results indicate that recently (1991–2000) croplands are a net source of carbon (net annual flux of 10.8 g C m−2 year−1 to the atmosphere). The recent temperature trend for the years 1951–2000 (+0.8 K in summer and +1.4 K in winter mean temperature) alone have already caused a significant net flux of 1.8 g C m−2 year−1 to the atmosphere. Future climate change (2001–2055) derived from regionalised meteorological properties driven by the IPCC-SRES A1 scenario results in an increased net C flux of an additional 4 g C m−2 year−1 in comparison to the reference period (1951–2000). Uncertainties attached to C flux results are estimated with a standard error of 6%. Besides climate-induced alteration of net C fluxes, considerable impacts on groundwater recharge (–45.7%), river flow (–43.2%) and crop yield (–11% to −15% as a basin-wide average for different cereals) were obtained. Recent past and expected temperature changes within the Elbe basin predominantly contribute to the increase of net C fluxes to the atmosphere. However, decreased crop growth (crop yields) and decreased expected water availability counteract even higher net C losses as soil C turnover is reduced through less C input (less crop growth) and drier soil conditions (decrease in water availability). Based on this study, present-day and potential future development of net C fluxes, water components and crop yields were quantified. This allows integrated assessment of different ecosystem services (C storage, water availability and crop yield) under climate change in river basins.

Realizing Mitigation Efficiency of European Commercial Forests by Climate Smart Forestry

European temperate and boreal forests sequester up to 12% of Europe’s annual carbon emissions. Forest carbon density can be manipulated through management to maximize its climate mitigation potential, and fast-growing tree species may contribute the most to Climate Smart Forestry (CSF) compared to slow-growing hardwoods. This type of CSF takes into account not only forest resource potentials in sequestering carbon, but also the economic impact of regional forest products and discounts both variables over time. We used the process-based forest model 4 C to simulate European commercial forests’ growth conditions and coupled it with an optimization algorithm to simulate the implementation of CSF for 18 European countries encompassing 68.3 million ha of forest (42.4% of total EU-28 forest area). We found a European CSF policy that could sequester 7.3–11.1 billion tons of carbon, projected to be worth 103 to 141 billion euros in the 21st century. An efficient CSF policy would allocate carbon sequestration to European countries with a lower wood price, lower labor costs, high harvest costs, or a mixture thereof to increase its economic efficiency. This policy prioritized the allocation of mitigation efforts to northern, eastern and central European countries and favored fast growing conifers Picea abies and Pinus sylvestris to broadleaves Fagus sylvatica and Quercus species.

Mistletoe-induced growth reductions at the forest stand scale

The hemiparasite European mistletoe (Viscum album L.) adversely affects growth and reproduction of the host Scots pine (Pinus sylvestris L.) and in consequence may lead to tree death. Here, we aimed to estimate mistletoe-induced losses in timber yield applying the process-based forest growth model 4C. The parasite was implemented into the eco-physiological forest growth model 4C using (literature-derived) established impacts of the parasite on the trees water and carbon cycle. The amended model was validated simulating a sample forest stand in the Berlin area (Germany) comprising trees with and without mistletoe infection. At the same forest stand, tree core measurements were taken to evaluate simulated and observed growth. A subsample of trees were harvested to quantify biomass compartments of the tree canopy and to derive a growth function of the mistletoe population. The process-based simulations of the forest stand revealed 27% reduction in basal area increment (BAI) during the last 9 years of heavy infection, which was confirmed by the measurements (29% mean growth reduction). The long-term simulations of the forest stand before and during the parasite infection showed that the amended forest growth model 4C depicts well the BAI growth pattern during >100 years and also quantifies well the mistletoe-induced growth reductions in Scots pine stands.