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Climate change severely affects mountain forests and their ecosystem services, e.g., by altering disturbance regimes. Increasing timber harvest (INC) via a close-to-nature forestry may offer a mitigation strategy to reduce disturbance predisposition. However, little is known about the efficiency of this strategy at the scale of forest enterprises and potential trade-offs with biodiversity and ecosystem services (BES). We applied a decision support system which accounts for disturbance predisposition and BES indicators to evaluate the effect of different harvest intensities and climate change scenarios on windthrow and bark beetle predisposition in a mountain forest enterprise in Switzerland. Simulations were carried out from 2010 to 2100 under historic climate and climate change scenarios (RCP4.5, RCP8.5). In terms of BES, biodiversity (structural and tree species diversity, deadwood amount) as well as timber production, recreation (visual attractiveness), carbon sequestration, and protection against gravitational hazards (rockfall, avalanche and landslides) were assessed. The INC strategy reduced disturbance predisposition to windthrow and bark beetles. However, the mitigation potential for bark beetle disturbance was relatively small (− 2.4%) compared to the opposite effect of climate change (+ 14% for RCP8.5). Besides, the INC strategy increased the share of broadleaved species and resulted in a synergy with recreation and timber production, and a trade-off with carbon sequestration and protection function. Our approach emphasized the disproportionally higher disturbance predisposition under the RCP8.5 climate change scenario, which may threaten currently unaffected mountain forests. Decision support systems accounting for climate change, disturbance predisposition, and BES can help coping with such complex planning situations.

Dark septate endophytes of the Phialocephala fortinii s.l. – Acephala applanata species complex (PAC) are abundant root colonizers of woody plants in boreal and temperate forest ecosystems where they form complex communities. Community structure was spatially stable for 3 years in a previous experiment, suggesting PAC’s inability to disperse or mutual inhibition of neighboring PAC genotypes. The aim of this study was to test whether changes in PAC community structure occur at all. The community structure originally determined in 2004 was reassessed in 2014 in a Norway-spruce plantation using microsatellite genotyping. Most isolates belonged to Phialocephala turicensis, P. letzii, P. europaea, and P. helvetica in both years. P. uotilensis and Acephala applanata were rare. PAC species were the same at only two grid points in both years. P. europaea was more frequent than P. turicensis in 2004 whereas the situation was opposite in 2014. Only four of the 22 genotypes in 2004 were found in 2014. Interestingly, none of the genotypes was detected at the same grid points in both years. Extended sampling in 2014 led to a significantly higher number of grid points testing positive for the presence of P. turicensis and P. helvetica. More than 3 years are required to detect shifts in PAC community structures. The observed shifts suggest that PAC are able to disperse in soil or via root networks, though very slowly.