Hope for the best, expect the worst: including disturbances in simulations as tree- or stand-wise mortality increases uncertainty for north German Scots pine forestry

Abstract Recent mortality pulses indicate pathways to restore maladapted forests towards more natural, mixed, resilient ecosystems. Under climate change, carbon sequestering forests serve as forces for mitigation but face threats from disturbances. The uncertain development of this duality complicates stakeholder-relevant predictions of timber yield or tree species compositions. We analyzed uncertainty in forest development over 50 years, focusing primarily– but not exclusively– on Scots pine, the most important tree species in northern Germany,. Thereunto, i. future survival was examined on a site- and climate-specific basis. The novelty of the simulations lies in ii. quantifying the influence of irregular die-off on forests under stand-wise (discrete) or tree-wise (diffuse) mortality patterns to iii. investigate yield and harvest potentials. By spanning a scenario funnel from two management and two climate projections on 17,551 National Forest Inventory plots in northern Germany, we assess prospective uncertainties. The transition of forest composition through space and time with conditional hazard rates resembles a Markov process via Monte Carlo sampling. Prospectively, i. mortality doubles depending on the species. Compared to undisturbed development, ii. forest restoration outcomes are uncertain; stand-losses can accelerate restoration by up to 10%, while tree-losses might slow it down. Under disturbances, iii. volume increment and stand age decrease as harvests rise in the medium-term with large dimensioned timber increasing fivefold. Driven by climate change and forest demographics, the decline in yield and the remaining 40% monocultures are critical. Forest development is inert, therefore we suggest more differentiated silvicultural concepts for actively adapting forests to alarming changes.