Forest management faces a climate induced shift in growth potential and increasing current and emerging new risks. Vulnerability analysis provides decision support based on projections of natural resources taking risks and uncertainties into account. In this paper we (1) characterize differences in forest dynamics under three management scenarios, (2) analyse the effects of the three scenarios on two risk factors, windthrow and drought stress, and (3) quantify the effects and the amount of uncertainty arising from climate projections on height increment and drought stress.

Rapid climate change leads to significant shifts in the site-productivity relationship of tree species and alters abiotic and biotic risks well beyond classical rotation ages on many forest sites worldwide. Forest conversion may be an adequate measure to counter possible negative effects of climate change. Unfortunately, climate-driven changes in abiotic and biotic risks bear a significant source of intrinsic uncertainty inherent in climate projections. It is our goal to appraise uncertainty in species selection under drought stress, one of the most important risk factors for many forests. We derive a method to assess drought restrictions and demonstrate the uncertainty in the process of species selection by applying three climate scenarios. Furthermore, we interpret the consequences of climate uncertainty in the light of different management goals, i.e., a business-as-usual silviculture, a climate protection strategy favoring CO₂ sequestration and a biodiversity strategy increasing diversity. The methods are applied to two representative regions in the North German Plain. The results clearly show the strong need for adaptive planning when drought restrictions are considered. However, different silvicultural management objectives may alter the extent of adaptive planning. The uncertainty in the planning process arising from different underlying climate projections strongly depends on the regional site characteristics and on forest management strategy. In conclusion, it is most important in forest planning to clearly state the management goals and to carefully explore if the goals can be met under climate change and if the uncertainty due to climate projections significantly affects the results of species selection.

Forest management decisions are based on expectations of future developments. For sound decisions it is essential to accurately predict the expected values in future developments and to account for their inherent uncertainty, for example the impact of climate change on forests. Changing climatic conditions affect forest productivity and alter the risk profile of forests and forest enterprises. Intensifying drought stress is seen as one major risk factor threatening forest management in the north German lowlands. Drought stress reduces tree growth and vitality and might even trigger mortality. But so far, it is not possible to quantify effects of a persistent dryer climate on forest productivity at a level suitable for forest management. We apply a well-established single-tree forest growth simulator to quantify the effect of persistent dryer climates on future forest productivity. We analyse the growth of Scots pine (Pinus sylvestris L.), European beech (Fagus sylvatica L.) and oak (Quercus robur L. and Quercus petraea (Matt.) Liebl.) in two forest regions in the north German lowlands for a time interval of 60 years until 2070. The growth response under three different climate projections is compared to a baseline scenario. The results show clear differences in volume increment to persistent dryer climates between tree species. The findings exhibit regional differences and temporal trends. While mean annual increment at biological rotation age of Scots pine and oak predominantly benefits from the projected climate conditions until 2070, beech might suffer losses of up to 3 m³·ha^–1·yr^–1 depending on climate scenario and region. However, in the projection period 2051 to 2070 the uncertainty ranges comprise positive as well as negative climatic effects for all species. The projected changes in forest growth serve as quantitative contributions to provide decision support in the evaluation of, for example, species future site suitability and timber supply assessments. The analysis of productivity changes under persistent dryer climate complements the drought vulnerability assessment which is applied in practical forestry in northwestern Germany today. The projected species’ productivity has strong implications for forest management and the inherent uncertainty needs to be accounted for.

The North German Lowland is a region with locally high nitrate (NO₃⁻) concentrations in seepage water, inducing an increased susceptibility to the effects of climate change. The future risk of rising NO₃⁻ concentrations in seepage water from forests was quantified for four regions in the North German Lowland using climate projections and a modelling system comprising submodels for forest stand development (WaldPlaner), water budgets (WaSiM-ETH), and biogeochemical element cycles (VSD+). The simulations for the period from 1990 to 2070 included three different forest management scenarios (reference, biodiversity, and climate protection) and showed a general decrease in groundwater recharge which could hardly be influenced by any of the management options. The simulated soil organic matter stocks adequately represented their past increase as expected from the National Forest Soil Inventory (NFSI), but also showed a future decline under climate change conditions which leads to higher organic matter decomposition and a long-lasting increase of NO₃⁻ leaching from forest soils. While the climate protection oriented scenario shows the highest increase in NO₃⁻ concentrations during the projection period until 2070, the biodiversity scenario kept NO₃⁻ concentrations in seepage water below the legal thresholds in three of four selected model regions.

Enriching tree species–poor and less productive forests by introducing economically valuable species is a strategy proposed for achieving multipurpose forest management. However, empirical evidence from managed and mature forests on the impact of this enrichment on ecological (multidiversity and ecosystem multifunctionality) and economic dimensions remains scarce, particularly when nonnative species are used. Here, we propose and test a framework that integrates economic multifunctionality, encompassing timber production–oriented goals and resistance against disturbances, with multidiversity and ecosystem multifunctionality in European beech forest stands enriched with conifers. Our results show that enriched beech forest stands (~80 years old) can provide high levels of economic multifunctionality without compromising multidiversity and ecosystem multifunctionality. In comparison to pure beech stands, enriched stands with Douglas-fir supported win-win-win situations for these three dimensions. Our findings contribute to the discussion of integrating biodiversity, ecosystem, and economic functions, providing empirical evidence for future forest management.