Simulating the effects of climate change on the growth and management of uneven-aged Oriental beech (Fagus orientalis L.) in Hyrcanian forests of Iran

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Abstract Adaptive management approaches are needed to maintain and improve forests’ resilience to future climatic changes. Climate sensitive forest increment models are the crucial tools to evaluate the performance of the adaptive strategies in forest management under climate change. Oriental beech (Fagus orientalis L.) is the most dominating and commercially important tree species in Hyrcanian forests of Iran, the main source of timber production, biodiversity conservation, and eco-tourism. Consequently, this study aims to achieve three primary objectives: (1) to develop a climate-sensitive tree increment and yield model for oriental beech forests (2) to predict the increment and yielding of these forests in the future under climate change (IPCC scenarios), and (3) to analyze the resilience of four alternative management strategies including business as usual (BAU) and logging ban. We re-calibrated a single-tree diameter and height increment, and tree survival models using forest measurement data from permanent plots with five-year interval and from 1988 to 2018. By validating the models, three climate change scenarios RCP2.6, RCP4.5 and RCP8.5 as well as four harvest strategies (logging ban, intensified logging (50% above BAU), and decreased logging (50% < BAU), and BAU) were applied for the simulation of increment and survival probability of single trees in a selected site. Our findings indicate that climate change, particularly increased drought stress under the RCP8.5 scenario, significantly reduces the increment and survival probability of beech trees. However, under RCP2.6 and RCP4.5, we observed a slight increase in increment. Implementing a logging ban as a management strategy emerged as the most resilient alternative for these forests, potentially fostering an increase in both diameter (up to 5.93 cm) and height increment (up to 3.12 m) until the final period. These findings lend support to the existing forest policy of enforcing a ten-year logging ban in the Hyrcanian forests of Iran.