European Beech Forests in Austria—Current Distribution and Possible Future Habitat

: A change in tree species composition in Central Europe to increase the resilience of forests when coping with climate change effects is imminent. We evaluated the present and expected future role of the European beech, ( Fagus sylvatica L.), with respect to the expansion of its habitat and its stem. We assessed the current relevance of beech from data of the Austrian Forest Inventory 2007/09, and analyzed forest policies promoting the establishment of beech forests. We simulated forest growth with the model CALDIS, linked with the timber-market model FOHOW2. We used a business-as-usual (BAU) forest management strategy under moderate (RCP 4.5 BAU) or extreme (RCP 8.5 BAU) climate change. We also simulated an extreme climate change scenario with a forced change in the tree species composition (RCP 8.5 Change Species). Beech occurs in Austrian forests over the elevational gradient of 250 to 1600 m a.s.l. In low elevation, it forms beech-dominated forests, often for the supply of the domestic fuelwood demand. In mountain regions, beech enriches the diversity of Norway spruce, ( Picea abies (L.) H. Karst.)-dominated forests. In a BAU setting, the habitat of beech increases only slightly in both climate scenarios. The scenario ’RCP 8.5 Change Species’ increases the habitat of beech in the next 60 years considerably. With progressing warming, other broadleaved tree species gain relevance. The vulnerability to drought and pathogens are limiting factors for Austrian beech forests. The future habitat depends on many factors such as the ability of forests to cope with climate change, the conﬁdence to arising market opportunities of beech timber in the wake of technological progress, and ﬁnancial and non-ﬁnancial incentives for the implementation of adaptive forest management.


Introduction
European beech, Fagus sylvatica L. (Fagales: Fagaceae), is an Atlantic tree species growing on a broad range of site conditions over a substantial elevational range.The wood is appreciated for indoor use and musical instruments, as well as for plywood, veneering and pulp.Due to its high energetic potential, beech is coppiced for firewood, and charcoal and is expected to increase its role as a construction material [1,2].Beech favors a humid atmosphere and well-drained soils which its roots easily penetrate.On favorable sites in low elevation, beech out-competes other tree species due to its excellent shade tolerance [3].In the Southern and Northern Alps, it occurs on dry sites and in high elevation.At such sites the productivity and the wood quality are low.
Its current Austrian habitat is strongly influenced by human management.Historically, beech was a major energy source.Medieval salt production, particularly in the provinces Salzburg and Upper Austria, greatly reduced the forest resources.The demand for beech as fuelwood in mining areas (Tyrol) and for domestic use as fuel wood (entire country) was enormous [4].Prior to the wide-scale availability of fossil fuels, growing cities were supplied with energy from wood.An example are the Vienna Woods, where large pure beech stands were established at sites that would naturally be occupied by a mixture of oak, Quercus sp.L. (Fagales: Fagaceae), hornbeam, Carpinus betulus L. (Fagales: Betulaceae), and other broadleaved trees [5].The energy demand of the Austrian capital required floating of timber from the surrounding mountain regions in the south of Vienna, and extended as far as the Bohemian forest in a distance of more than 250 km away [6].
At the end of the 19th century, coal became available, the relevance of beech as energy source declined, and the business model of forestry was fundamentally changed.Stands of highly productive tree species such as spruce gradually replaced mixed-species forests.This tendency continued after World War II, when many forests were harvested in order to provide post-war compensation payments, and the cleared sites were re-forested with 'secondary spruce forests' of Norway spruce, Picea abies (L.) H. Karst (Pinales: Pinaceae).Due to human cultivation, the habitats of silver fir, Abies alba Mill.(Pinales: Pinaceae), and beech were reduced to 30% of their original size [7].Forest managers were aware of risks posed by storm damages and bark beetle to mono-species spruce stands.Yet, the high productivity of spruce and the establishment of a spruce-oriented timber-processing industry were strong incentives [8].
Secondary spruce forests raised concerns of forest ecologists.The resistance of needle litter slowed the decomposition of soil organic matter and led to superficial soil acidification.The process was partially attributed to the chemical quality of spruce needles, and partially to unfavorable environmental conditions in pure spruce stands [9,10].It was recognized that beech roots re-circulate nutrients from deeper soil horizons that were not accessible by the shallow rooting system of spruce [11,12].The pragmatic slogan for Austrian submontane forests to cultivate "as much spruce as possible, and as much beech as necessary" [13] reflected the desire to maintain both a high productivity, and a high soil chemical quality.
Central European forests are affecting the national greenhouse gas emissions budgets.Managed spruce-dominated forests have for decades been a carbon sink.The land use, land-use change, and forestry sector (LULUCF) has compensated for 5% to 30% of the national greenhouse gas emissions of Austria [14].The main reasons were low harvest rates, the fertilizing effect of nitrogen depositions, the elongation of the growing season, and a favorable age-structure of forests.The sequestration of CO 2 in the biomass and in soils is diminishing due to increasing disturbances [15][16][17][18].
The tree species composition in future 'climate-smart forests' is a matter of debate.Abiotic and biotic disturbances are already re-shaping European forests.Foresters agree that mixed-species forests have the benefit of risk distribution because trees have different traits [19].Beech is going to play an important role, together with other coniferous tree species such as European larch, Larix decidua Mill.(Pinales: Pinaceae), and silver fir in mountain forests, and Douglas fir, Pseudotsuga menziesii (Mirbel) Franco (Pinales: Pinaceae), in low elevation.Scots pine, Pinus sylvestris L. (Pinales: Pinaceae), and other pine species will be an option across a wide elevational range.Other broadleaved trees are considered because evidence for the susceptibility of beech to recurring drought events and heat is increasingly provided [20][21][22].
The common European forest policy has identified the climate-change-related challenges [23].Private forest owners are managing a large forest area in Central Europe [24].Their formal education in forestry, participation in the forest policy discourse, and personal preferences towards forest management are heterogeneous [25][26][27].The European forest policy advocates nationally implemented incentives that support the increase in broadleaved forests.We used information from an international survey to evaluate whether European support programs are supporting a wider distribution of beech forests [28].
Modeling is a useful tool for delineating the potential future habitat of tree species.The results need to be aligned with other drivers that are affecting forestry.The main objective of our project is putting the results of scenario analyses on the future potential habitat of beech in the context of emerging trends that are manifest from the Austrian Forest Inventory, the preferences of forest owners towards beech as investigated in earlier projects, and currently implemented forest policies potentially influencing the decisions of forest managers.We assessed the current stem volume of beech in different altitudes, based on data of the Austrian Forest Inventory.The potential habitat of beech was derived from a simulation exercise with different underlying climate scenarios and forest management adaptation strategies.We interpreted the rule-based outcomes of the scenarios with the available information on the attractiveness of beech from earlier projects.The future role of beech is determined by management decisions of predominantly private forest owners who are heterogeneous with respect to their individually managed forest area, their engagement in active forest management and forest policy, their participation in the timber market, and their formal education in forestry issues.The presented text is related to other studies on an analysis of timber market opportunities for beech products, and silvicultural peculiarities (in this Special Issue: [2]).

Austrian Forest Inventory
We used data of the Austrian Forest Inventory of 2007/09, which were the latest available results at the beginning of the project.The characteristics of the Forest Inventory are described in detail in a book chapter [29].A peculiarity of Austrian forests is the differentiation into production and protective forests.Production forests are mainly managed for the provision of timber, while protective forests reduce the risk of natural hazards to lives and infrastructure, and are managed for the maintenance of an appropriate stand structure [30].According to the Austrian Forest Inventory, beech currently contributes 10% to the standing stock of the stem volume of production forests, and 8% to protective forests, respectively, making it the dominant broadleaved tree species (Table 1).Austria has a forest cover of roughly 50%.The forest area is continually increasing since at least 1960, mostly at the expense of agricultural land in mountain areas and, to a smaller degree, by the upwards expansion of the upper timberline (Table 2) [32].Conifer forests are covering more than twice as much area as broadleaved forests.The area of spruce forests is declining and the area of beech is increasing, respectively.Table 2. Area of conifer and broadleaved forests in Austria and the area of mixed-species forests with a coverage of broadleaved trees of more than 80% and 50%, respectively (source: [31]).The Austrian Harvesting Statistics show the dominance of conifers over broadleaved trees (Table 3).The average contribution of timber from broadleaved trees is about 15% of the annual harvest, indicating the accentuated focus of the timber industry on spruce.

Modeling Forest Growth and Management
Within the 'CareForParis' project, we simulated the growth of Austrian forests under different climate scenarios with the model CALDIS [34,35].The CALDIS is a distanceindependent, individual-tree stand development model that is based on PROGNAUS [36].It comprises climate sensitive functions for basal area and height increment for the dominant tree species in Austria [37,38].The model uses tree and site information from the Austrian National Forest Inventory.Individual tree growth is driven by site parameters (growth region, elevation, soil type, soil depth, exposition, and climate).Tree mortality in the past, thinning operations, and harvesting activities are reflected in the inventory data.The future rate of abiotic and biotic forest disturbances is based on stochastic modules, depending on site history and stand dimensions.CALDIS generates the dimensions of individual trees in annual time steps, and classifies them into standing stock and mortality.For the use in scenarios, CALDIS uses a mechanistically defined subroutine for storm damages with wind speed, stand height, and stand density as parameters, and a probabilistic module for biotic damage.In the course of each CALDIS simulation run, the individual sample plots were assigned to different harvesting operations, such as final harvest and thinning using site-specific pre-commercial thinning stem number guide curves.CALDIS has been amply used for management scenarios [34,39] and for the forest reference levels according to the requirements of UNFCC (https://redd.unfccc.int/fact-sheets/forest-reference-emissionlevels.html(accessed on 1 January 2023)).The starting point of the presented scenarios was the condition of the Austrian forests as presented in the National Forest Inventory 2007/09.
The growth model interacted with the timber-market model FOHOW2.FOHOW2 uses data on the general economy (gross domestic product, population), data describing the forest industry and forest product markets (demand, supply, prices and trade), and the market participation of three ownership categories (small and large forest enterprises, and Austrian Federal Forests) [39][40][41].The forest resources (growing stock and increment by tree species) were supplied by CALDIS.It was necessary to underlay the forest growth model with a realistic timber extraction rate.The demand for timber was econometrically estimated, based on a time series from 1975 to 2010.It defined the annual harvesting rate that was implemented in CALDIS.The procedure was a handshaking between growth and demand.In 10-year intervals, FOHOW2 defined a timber demand for specific timber assortments.The demand was satisfied from the modeled standing stock of stem biomass.The location of supply sites was chosen by the operator of CALDIS under the consideration of economic, ecological, and legal constraints.
For the analysis of the future distribution of beech, we used the scenario RCP 4.5, that almost but not quite reaches the Paris commitments, and the very pessimistic climate scenario RCP 8.5.RCP stands for 'Representative Concentration Pathways', with anthropogenic radiative forcing of 4.5 and 8.5 W m −2 , respectively.The scenario data were held available at the CCCA data center [42,43].Climate scenarios were available until 2100.The climate data were downscaled to the Forest Inventory grid and extrapolated until 2150.For RCP 4.5 and RCP 8.5, the trend of the temperature increase was extrapolated.The extrapolation was implemented by assessing the trend of temperature and precipitation with a logit function.The noise in the data were generated by randomly drawing values from monthly data of the period 2071 to 2100 that were added to the trend.The potential future habitat of beech was assessed by the comparison of three forest growth scenarios (Table 4).For the change in tree species composition due to climate change, a uniform decision pattern of forest managers was assumed.Whenever a stand reached maturity and was harvested, the choice of the tree species in the scenario 'RCP 8.5 Change Species' was based on the expected mean air temperature 50 years after stand establishment (Table 5).The chosen tree species followed textbook knowledge [13].The selected tree species were entered in the probabilistic submodule 'ingrowth' of CALDIS.It contains parameters for 28 tree species, and was developed from data of the Austrian Forest Inventory [44].The model-based selection process defined the tree species composition of the regenerating forest stand.Further details on reforestation rules have been described previously [35].More complex decisions, such as the frequency and length of drought periods, were not admitted.We limited our scenarios to domestic tree species.Other tree species that do not belong to the autochthonous tree species may or may not play a relevant role in the future [45].Alternatively to 'RCP 8.5 Change Species', the scenario 'RCP 8.5 BAU' favors the harvested tree species for reforestation.A change in tree species is enabled by a stochastic ingrowth model that reflects the current replacement of spruce forests with other tree species based on the results of the Forest Inventory (Table 2) [35].

Data Evaluation
CALDIS delivers morphological tree characteristics on the standing stock, the harvested trees, and tree mortality on a yearly basis on the grid of the Austrian Forest Inventory.We aggregated the standing stem volume of beech for each grid point in the remaining forest, i.e., after harvesting and mortality, in R [46] and overlaid the grid cells that are used by the Habitats Directive (Council Directive 92/43/EEC on the Conservation of natural habitats and of wild fauna and flora) using QGIS v.23.8 [47].The figures were created with the R packages lattice [48] and ggplot [49].

Results
The applied climate scenarios, averaged over all forest inventory plots, are shown in Figure 1.The extrapolation of scenario RCP 4.5 assumes no further warming trend after the year 2100, whereas temperatures rise unabated in the extrapolated RCP 8.5 scenario.The climate scenarios are less clear on the change in precipitation.The IPCC scenarios do not show a clear trend in annual precipitation rates, although the temporal pattern of rain within years and the intensities of the events are expected to change [50].(Scrophulariales: Oleaceae), and hornbeam are common.With increasing altitude, i.e., above 500 m a.s.l., beech is the dominant broadleaved tree species, together with sycamore maple, Acer pseudoplatanus L. (Sapindales: Sapindaceae).In the high-montane and subalpine region beech is currently scarcely present.
In Figure 3, the future spatial distribution according to the chosen scenarios is shown.In scenario 'RCP 4.5 BAU' the habitat expands at some sites as a consequence of warming until the end of the simulation period.The increase of the habitat is modest.A similar pattern is observed for the scenario 'RCP 8.5 BAU'.Despite a strong warming trend, the timber-market driven forest management strategy is not changed.The increase in habitats in scenarios 'RCP 4.5 BAU' and 'RCP 8.5 BAU' follows the trend that is evident from the data of the Austrian Forest Inventory and is a consequence of the habitat loss of spruce due to climate change related disturbances together with an unaltered high demand for spruce timber (Tables 2 and 3).A different pattern is observed in 'RCP 8.5 Change Species'.In this scenario, beech temporarily gains relevance, but from approximately 2070 onward, no significant further extension of its habitat occurs.We emphasize that the scenario 'RCP 8.5 Change Species' does not represent a maximization of the habitat of beech.Instead, it visualizes the effect if all Austrian forest owners (presently about 150,000 persons) follow the adaptation strategy towards climate change that is defined in Table 5.According to the rule of tree species change (Table 5), beech temporarily extends its habitat, but later falls out of the narrow window (mean annual temperature between 7 and 11 °C) in which it would be the preferred tree species for coping with climate change.The tree species distribution at the end of the simulation period (year 2150) is shown in Figure 4.With moderate warming (RCP 4.5 BAU), the standing stock of stem volume would still be dominated by Norway spruce.Other conifers such as silver fir, Scots pine, and European larch would extend their habitat somewhat.In mountain areas above approximately 1000 m a.s.l., the changes would be rather small; in lower elevations, conifers lose ground against broadleaved trees.With extreme warming, together with concerted efforts towards tree species change (RCP 8.5 Change Species), the forests are fundamentally changed.Only at elevations higher than 1500 m a.s.l.would conifers contribute the larger fraction of the timber volume.In lower elevations, beech and other broadleaved trees would dominate.

Interpretation of the Modeled Future Habitat of European Beech
The present habitat of beech in Austria across altitude is shown in Figure 2, and its spatial distribution in yellow shades in Figure 3. Moderate climate change (Scenario 'RCP 45 BAU') shows a modest expansion of the habitat of European beech, mostly at the edges of the already occupied habitat.The increase in the potential habitat is a gradual process until 2050 (Figure 3a).In the case of a strong warming trend with business-as-usual forest management, the expansion of the beech habitat is also confined to few sites only (Figure 3b).The scenario reflects a situation where forest managers are willing to accept the risk of more climate-related disturbances.Under the assumption that forest managers respond to the science-based call for a change in tree species (Scenario 'RCP 8.5 Change Species'), beech expands its potential habitat extensively until 2050.Mostly sites that are presently occupied by secondary spruce forests in low-elevation areas and forests in the lower mountain range will be enriched with beech.A major part of the Austrian forest area will be potentially suitable for beech (Figure 3c).After several decades of persistent warming, beech will not be the preferred tree species and would not expand its habitat significantly further.The reason for this intermittent 'beech peak' is that climate scenarios of the RCP 8.5 group reflect a particular strong warming trend for the time after the year 2080.Applying the rules of tree species selection as given in Table 5, beech would only have a small window of opportunity in time.After 2080, other tree species such as sycamore maple and different oak species would be selected when harvested spruce-dominated stands are reforested.Thereby, beech maintains its potential habitat, but is not necessarily the primarily preferred tree species.An intermediate high relevance of beech in European forests, followed by a decline in relevance in the distant future, has been simulated in other experiments as well.The decline in the relevance of beech forests towards the second half of the century has already been found in a niche modeling exercise and in species distribution models [51][52][53].Yet, Figure 4 shows the simulated accentuated change in the timber supply until the year 2150.With moderate climate change (Scenario RCP 4.5 BAU), beech will gain habitats along a wide elevational range.The extreme scenario 'RCP 8.5 Change Species' shows that in the submontane and montane range, that currently hold highly productive spruce-dominated forests, can develop into a region that is shaped by different broadleaved-dominated forests, thereby altering the timber supply fundamentally.

Incentives for Establishing Beech in Mixed-Species Forests
Forests play an important role in the European Green Deal as part of the emerging bioeconomy, the long-term maintenance and increase of the forest carbon sink, and the maintenance of a high level of biodiversity.Multiple interests of players necessarily lead to both synergies and trade-offs [54][55][56].In order to fulfill multiple expectations, resilient and productive forests are required that are providing habitats for a variety of forest types.Forest policy offers incentives, both as subsidies and non-monetary support, to forest owners in order to achieve desired ecological and economic goals.In Austria, subsidies are granted from the European Agricultural Fund for Rural Development (EAFRD) [57].Beech is not explicitly recommended, but is addressed when the program calls for 'improved resilience of forests', 'improved viability of forests', or 'increased ecological value'.These terms can be interpreted broadly and give forest owners a lot of flexibility in the choice of measures to reach societal, personal, and political objectives.
About 50% of the Austrian area forest belongs to small-holder foresters with property sizes of commonly 20 ha or less.They have a high appreciation for their responsibility for environmental and social services provided by their properties, and implement often rather extensive forms of multi-functional forest management that do not necessarily optimize timber production.Many are open for increasing the proportion of beech in their forests [25,27,58].They are targeted by information campaigns on recommended measures for climate change adaptation [59,60].Their participation in EAFRD calls is disproportionately low because the expected monetary gain is unattractive when accounting for administrative needs upon the implementation of EAFRD projects [28].Yet, many political objectives are reached due to voluntary activities.Beech wood is held in high esteem for the fulfillment of the domestic fuelwood demand, particularly in rural areas where agriculture and forestry are tightly intertwined.
Forests in mountain areas are often managed by large forest enterprises, with a focus on timber production.Several tree species can compensate for a climate-change induced habitat reduction of the currently dominant spruce.Softwoods, such as European larch and silver fir, together with broadleaved trees such as sycamore maple, can replace spruce [61].With other economic priorities than small-holder foresters and lower expected annual temperatures in high elevation forests, owners of large forest enterprises may opt for other tree species besides beech (Table 5).Subsidies for forest improvements from EAFRD projects can be secured by many activities and do not necessarily increase the share of beech.
Presently, beech has a marginal role in protective forests (Table 1).Traditionally, preference was given to spruce due to its high interception of precipitation and the stabilization of the snow cover on steep slopes [62].Due to the high vulnerability of spruce in a future climate, the potential role of beech in protective forests is currently re-evaluated.The protection against rockfalls by sturdy beech stems is effective, and an adequate stand density can stabilize the snowpack [63].It is expected that beech is increasingly used in protective forests.

Productivity, Carbon Sequestration and Climate Change Mitigation by European Beech
The productivity of beech is lower than the productivity of spruce under most site conditions.Ideally, in mixed-species stands, resource sharing due to different root architectures can lead to overyielding and can buffer, but not completely mitigate, financial losses [64][65][66].The lower productivity is compensated for by risk reduction.However, at water-limited sites, the admixture of beech in spruce forests may reduce the resilience of the forest due to competition for water [67,68].The prospects for many autochthonous tree species, including beech in the case of severe climate change (RCP 8.5), are not favorable.Its productivity will very likely decline due to future droughts and heat that are expected for Austria and other places within the habitat of beech [20,22,50,[69][70][71][72].Recurring droughts may affect forests much sooner than predicted in models, exacerbating the need for flexible adaptation measures.In an economic optimization, a 'risk-averse forester' would likely opt for a spruce-dominated forest over a beech-dominated forest due to the expected revenue, despite clear indications of emerging challenges for spruce [67,73,74].On dry sites, oak can be the species of choice.
Beech has a large capacity for storage of organic carbon in the above-ground biomass, due to the stability of beech stands even at stand ages of more than 100 years and the high density of beech wood [75].Evidence is given for Central European mountain areas where beech is resilient towards disturbances, and the stands are highly productive [76].Yet, the carbon sequestration rate of beech-dominated forests is smaller than the capacity of sprucedominated forests [77].Soils of beech forests hold higher organic carbon stocks in deeper soil horizons than spruce forests.The translocation of organic carbon into the subsoil is partially compensated by smaller stocks in the biologically active surface layer.Therefore, soil organic carbon stocks of beech forests are often lower than of spruce stands [11,[78][79][80].
The relevance of beech for climate change mitigation also depends on the future wood products that are manufactured of beech.Currently, spruce timber is the dominant tree species on the Austrian market (Table 3).Whereas the major share of timber from conifers is converted to industrial roundwood, 75% of the harvested beech timber in Austria is presently used as fuelwood.A climate smart timber economy favors long-lasting wood products, with energy production being the final step in the value chain.Therefore, research programs are underway, aimed at improving the share of beech timber that is used for durable beech wood products instead of producing primarily fuel wood.Due to its high weight, and the possible distortion upon wetting, beech can currently not fully replace spruce timber as a construction material.Our simulation experiment does not account for innovations in timber processing.Research programs are underway to optimize the use of beech in wood products in a wide variety of fields in order to enhance the opportunities for a sustainable forest-based bioeconomy [2,81,82].Notable inventions are glued crosslaminated timber that overcomes technological challenges and the use of beech wood fibers for textiles [83].

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Agricultural enterprises often include forest land supplying fuelwood (beech) and roundwood (conifers) for the domestic use.This tradition has led to the abundance of beech at low elevation in rural areas;

Figure 1 .
Figure 1.Climate scenarios for Austria, chosen from the dataset of ÖKS 15 for a moderate warming trend (RCP 4.5, blue lines) and an extreme warming trend (RCP 8.5, red lines).(a) Mean annual temperature, (b) annual precipitation.Site-specific data have been used for the scenario calculations.The dashed vertical line shows the limit of the official IPCC climate scenarios (ÖKS 15) and the extrapolation of the scenarios.

Figure 2
Figure2shows that beech is present over a large altitudinal range.In the planar and colline region, other broadleaved trees such as oak, willow, Salix sp.L. (Salicales: Salicaceae), poplar, Populus sp.L. (Salicales: Salicaceae), ash, Fraxinus excelsior L. (Scrophulariales: Oleaceae), and hornbeam are common.With increasing altitude, i.e., above 500 m a.s.l., beech is the dominant broadleaved tree species, together with sycamore maple, Acer pseudoplatanus L. (Sapindales: Sapindaceae).In the high-montane and subalpine region beech is currently scarcely present.In Figure3, the future spatial distribution according to the chosen scenarios is shown.In scenario 'RCP 4.5 BAU' the habitat expands at some sites as a consequence of warming until the end of the simulation period.The increase of the habitat is modest.A similar pattern is observed for the scenario 'RCP 8.5 BAU'.Despite a strong warming trend, the timber-market driven forest management strategy is not changed.The increase in habitats

Figure 2 .
Figure 2. Current standing stock of stem wood in Austria with beech shown in dark green shades in different elevational zones.The data are obtained from the Austrian National Forest Inventory of 2007/09 [31].

Figure 3 .
Figure 3. Expected areal increase in the distribution of European beech in Austria.The upper graph (a) represents the climate scenario RCP 4.5, with modest warming and continuation of forest management practices in a business-as-usual setting ('RCP 4.5 BAU'); (b) represents the climate scenario RCP 8.5 with business-as-usual forest management ('RCP 8.5 Change Species').The lower graph (c) shows the potential habitat according to the climate scenario RCP 8.5, under the assumption that all forest owners implement the suggested tree species selection strategy ('RCP 8.5 Change Species').

Figure 4 .
Figure 4. Simulated standing stock of stem wood in Austria in the year 2150, with beech shown in dark green shades in different elevational zones.(a) Stem volume according to a RCP 4.5 climate change scenario with forest management following a 'business-as-usual' concept, (b) Stem volume according to RCP 8.5 with a concerted change in tree species as adaptation strategy (RCP 8.5 Change Species).The starting point of the simulation are data obtained from the Austrian National Forest Inventory of 2007/09.

Table 1 .
[31]ding stock of stem volume in Austria in production and protective forests.Stem volume of European beech in Austrian forests (source:[31]).

Table 4 .
Climate scenarios and the simulated response of forest owners.
• European beech is a desired admixed species in forests dominated by Norway spruce for ecological reasons.It enriches the stand diversity and has the ability to recycle nutrients from deeper soil horizons; • Climate change is an important driver for the expansion of the beech habitat, because beech can thrive in high elevation forests where it is presently of minor relevance.Active forest management decisions have a stronger and instantaneous impact on the habitat of beech than climate change effects; • Our scenarios represent extreme cases of climate change.They are by no means predictions, because future market conditions are not factored in, nor is the actual extent of climate change known.Also, a uniform foreward looking approach towards adaptation strategies in forest management by the highly heterogeneous group of forest owners is unlikely; • The future relevance of beech is potentially high when conifer forests are gradually enriched with broadleaved trees as an adaptation to climate change.Yet, several broadleaved tree species will gain in relevance and may outcompete beech in the case of extreme warming, particularly when they can tolerate drought and heat; • European beech has a dual role in the mitigation of climate change.Beech forests are less productive than spruce forests, yet they are less vulnerable to some biotic damage and storms.Due to the high density of beech timber, the carbon sequestration potential of beech is high.