Post-volcanic-eruption Forest Landscape Recovery And Its Impact Factors In Changbai Mountain

The Changbai Mountain in northeast China experienced a destructive volcanic eruption in 946 AD.This event is recorded as one of the largest volcanic eruptions globally during the last 2000 years.Hot lava,forest fire,and volcanic ash destroyed almost all vegetation within a radius of approximately 50 km surrounding the eruption.Forests beyond the 50 km radius became the matrix seed sources during the recovery,whereas a few refugia that survived the eruption were remnant seed sources.Driven by seed sources and seed dispersal,forest succession restarted.To date,forests have returned to a wide range of elevations on Changbai Mountain.Specially,forest zonation has developed on the north side of Changbai Mountain,with temperate,boreal,and dwarf forests growing along elevational zones that correspond to their climate zones,and forest landscape reached a quasi-equilibrium state.However,such vertical forest zones have not developed on the west and south sides of the mountain,where mosaics of mature and early-successional forests typify the landscape.One hypothesis to explain this phenomenon is disturbance caused by winds.The strong prevailing winds on the southwestern aspect of the mountain periodically strengthen into typhoons which resulted in forest landscape fragmentation.Several other potential factors can be ruled out: human impacts have been very low due to the remoteness and elevation of the site;disturbances caused by wildfire have been rare due to high precipitation and long winter seasons.Thus,the post-eruption recovery of the forest landscape of Changbai Mountain has probably been driven by a combination of natural succession associated with seed dispersal,disturbances caused by typhoons,and environment condition.The posteruption forest dynamics of Changbai Mountain provide an ideal dataset for identifying the long-term effects of seed sources,typhoon disturbance,and in situ environment on shaping the forest landscape.In this study,we reconstructed the historic(1710-2010)forest landscape and typhoon disturbance in Changbai Mountain using a spatially explicit,raster-based forest landscape model(FLM),LANDIS PRO.We designed factorial experiments to quantify the individual effects of the matrix and remnant seed sources and evaluate the relative importance of in situ environment(realistic heterogeneous vs.hypothetical homogenous)and typhoon(presence vs.absence).Additionally,we examined the roles of typhoon in shaping forest landscapes over a long timespan through comparing forest dynamics and pattern of northern Changbai Mt.with southern and western Changbai Mt.Our conclusions as follows:(1)Our work to present a forest landscape modeling framework for reconstructing a historic forest landscape and its disturbance regime is among few such attempts.Comparsion between simulated results by LANDIS PRO with current forest inventory and patterns,suggested that the composition,structure and spatial patterns of the reconstructed forest reasonably represented current forest conditions after a 300-year simulation.The simulated trajectories of post-eruption forest recovery followed the established theories of forest stand development.All these suggested that the LANDIS PRO forest landscape model can be an effective tool in modeling spatial and temporal reconstruction of the post-eruption historical forest landscape and disturbance regime.Spatiotemporal historic landscape reconstruction provides a platform to quantify the roles of driving factors in post-eruption forest landscape recovery from 1710 to 2010.(2)Remnant seed sources have relatively small effects in the early stage of postvolcanic eruption forest landscape recovery,and the effects increased with recovery.Remnant seed sources facilitate late-successional species recovery,advance forest succession,and alter species composition.Spatiotemporal historic landscape reconstruction provides a platform to simulate seed dispersal and quantify the roles of remnant seed sources on post disturbance landscape recovery.(3)Early forest development tends to be a deterministic community-assembly process governed by in situ environment suggesting that niche differences among species shape forest patterns.However,the impact of environmental conditions decreased over time,with disturbance becoming dominant in the late recovery stages.Thus,short-term studies may limit the understanding of the cumulative effects of disturbance,whereas historic landscape reconstruction reveals the full spectrum of interplays of environment,disturbance,and forest succession.(4)Typhoon had minimum effects on forest recovery at the early successional stage,and the effects gradually increased over time for each forest biome.Typhoon decreased the importance of late-successional/climax species in the mixed Korean pine and broadleaf forest and alpine forest but increased the importance of the evergreen coniferous species.The post-volcanic eruption landscapes without typhoon would ultimately reach a quasi-equilibrium state after 280 years of landscape recovery,while landscapes with typhoon never reached an equilibrium over 300 years.However,the effect of typhoon on landscape pattern gradually became stabilized after 250 years of landscape recovery.This suggested landscapes with typhoon evolved towards stabilization and maybe reach an equilibrium after 300 years.Our study suggested that infrequent,large disturbances have long lasting effects that require longer timeframe of investigation.