Forest Succession Model Research Articles

Evaluating the impacts of slope aspect on forest dynamic succession in Northwest China based on FAREAST model

Mountain forests provide the main water resources and lumber for Northwest China. The understanding of the differences in forests growing among individual slope aspects in mountainous regions is of great significance to the wise management and planning of these natural systems. The aim of this study was to investigate the impacts of slope aspect on forest dynamic succession in Northwest China by using the dynamic forest succession model (FAREAST).First, the simulated forest composition and vertical forest zonation produced by the model were compared against recorded data in three sub-regions of the Altai Mountains. The FAREAST model accurately reproduced the vertical zonation, forest composition, growth curves of the dominant species (Larix sibirica), and forest biomass in the Altai Mountains. Transitions along the forest zones of the Altai Mountains averaged about a 400 m difference between the northern and southern sites. Biomass for forests on north-facing slopes were 11.0, 15.3 and 55.9 t C ha−1 higher than for south-facing slopes in the Northeast, Central and Southeast sub-regions, respectively.Second, our analyses showed that the FAREAST model can be used to predict dynamic forest succession in Northwest China under the influence of slope and aspect. In the Altai Mountains, the north-facing slopes supported the best forest growth, followed by the west- and east-facing slopes. South-facing slopes consistently exhibited the lowest growth, biomass storage and forest diversity.

Dating the Cooloola coastal dunes of South-Eastern Queensland, Australia

The Cooloola sand dunes are part of a series of aeolian parabolic dunes that stretch along the east coast of Australia. They form a chronosequence showing increasing weathering, soil formation and water erosion across six geomorphically recognized soil landscapes. These landscapes were recognized from air photographs and further refined on the basis of some 150 auger holes across the dunes. Data about the structure and floristics of the vegetation were collected at the same time. There is a significant body of literature about the Cooloola dunes but there are two areas that have not been satisfactorily considered. First the previous dating which gave inconsistent results has been superseded by single grain OSL dates and second Cooloola has not been considered in a regional context. Here we report the results of single grain optically stimulated luminescence (OSL) analyses for 31 samples for 21 sites across the geomorphic landscapes. The sites were selected near the apex of each dune as this represents the last depositional date and the least disturbed by sand movement.We recognized 10 units across the dunes on the basis of the dates available. The dune ages ranged from recent to 725 ka. The largest dunes at some 320 m high were dated at around 140 ka and these dunes carry the maximum vegetation biomass of this dunefield. Beyond this vegetation maximum the dunes had lost their parabolic shape due to prolonged weathering and erosion and the vegetation is greatly reduced in height and biomass. The depth to the soil B horizon gradually deepens with age to form giant podzols in the older dunes. The depth to the B horizon was remarkably consistent within the geomorphic landscapes across the length and breadth of the dunes.These studies place the Cooloola dunes in a unique position as the chronosequence is intact. The possible processes that lead to the formation of the dunes and the regional implications are discussed. Secondly, it shows the buildup and decline of the dune ecosystems and acts as a model for all ecosystems. Forest succession models which place less emphasis on soil development miss this important process.

Modelling moose-forest interactions under different predation scenarios at Isle Royale National Park, USA.

Loss of top predators may contribute to high ungulate population densities and chronic over-browsing of forest ecosystems. However, spatial and temporal variability in the strength of interactions between predators and ungulates occurs over scales that are much shorter than the scales over which forest communities change, making it difficult to characterize trophic cascades in forest ecosystems. We applied the LANDIS-II forest succession model and a recently developed ungulate browsing extension to model how the moose population could interact with the forest ecosystem of Isle Royale National Park, USA, under three different wolf predation scenarios. We contrasted a 100-yr future without wolves (no predation) with two predation scenarios (weak, long-term average predation rates and strong,higher than average rates). Increasing predation rates led to lower peak moose population densities, lower biomass removal rates, and higher estimates of forage availability and landscape carrying capacity, especially during the first 40 yr of simulations. Thereafter, moose population density was similar for all predation scenarios, but available forage biomass and the carrying capacity of the landscape continued to diverge among predation scenarios. Changes in total aboveground live biomass and species composition were most pronounced in the no predation and weak predation scenarios. Consistent with smaller-scale studies, high browsing rates led to reductions in the biomass of heavily browsed Populus tremuloides, Betula papyrifera, and Abies balsamea, and increases in the biomass of unbrowsed Picea glauca and Piceamariana, especially after the simulation year 2050, when existing boreal hardwood stands at Isle Royale are projected to senesce. As a consequence, lower predation rates corresponded with a landscape that progressively shifted toward dominance by Piceaglauca and Piceamariana, and lacking available forage biomass. Consistencies with previously documented small-scale successional shifts, and population estimates and trends that approximate those from this and other boreal forests that support moose provide some confidence that these dynamics represent a trophic cascade and therefore provide an important baseline against which to evaluate long-term and large-scale effects of alternative predator management strategies on ungulate populations and forest succession.

Bending the carbon curve: fire management for carbon resilience under climate change

Forest landscapes are increasingly managed for fire resilience, particularly in the western US which has recently experienced drought and widespread, high-severity wildfires. Fuel reduction treatments have been effective where fires coincide with treated areas. Fuel treatments also have the potential to reduce drought-mortality if tree density is uncharacteristically high, and to increase long-term carbon storage by reducing high-severity fire probability. Assess whether fuel treatments reduce fire intensity and spread and increase carbon storage under climate change. We used a simulation modeling approach that couples a landscape model of forest disturbance and succession with an ecosystem model of carbon dynamics (Century), to quantify the interacting effects of climate change, fuel treatments and wildfire for carbon storage potential in a mixed-conifer forest in the western USA. Our results suggest that fuel treatments have the potential to ‘bend the C curve’, maintaining carbon resilience despite climate change and climate-related changes to the fire regime. Simulated fuel treatments resulted in reduced fire spread and severity. There was partial compensation of C lost during fuel treatments with increased growth of residual stock due to greater available soil water, as well as a shift in species composition to more drought- and fire-tolerant Pinus jeffreyi at the expense of shade-tolerant, fire-susceptible Abies concolor. Forest resilience to global change can be achieved through management that reduces drought stress and supports the establishment and dominance of tree species that are more fire- and drought-resistant, however, achieving a net C gain from fuel treatments may take decades.

Empfindlichkeit typischer Schweizer Waldbestände auf den Klimawandel

Sensitivity of typical Swiss forest stands to climate change In Switzerland, first climate-induced changes of forest ecosystems can be observed. However, it is widely unknown how and to what extent the typical (widespread) forest stands will respond to future climate change. With the data of the third National forest inventory and the forest succession model ForClim we examined the development 71 typical stands under current and future climatic conditions (A2 emission scenario) with and without management, respectively. The simulations show a weak response until the middle of the century. In contrast, an increased sensitivity towards the end of the century becomes apparent, expressed by declines of basal area at lower elevations, respectively increases at higher elevations. The responses of forest stands are depending on site-specific characteristics. For example, Norway spruce is expected to decline up to higher elevations. Our results show an increase of deciduous tree species in higher elevation zones, particularly if management is applied. The impacts of climate change on important forest ecosystems services vary along a bioclimatic elevation gradient. Thereby, current forest management shows approaches how to at least partly counteract adverse effects of climate change. However, target- and site-specific strategies are needed and, particularly with regard to lower elevations, more knowledge on the potential of tree species to adapt is required.

The simulated effects of timber harvest on suitable habitat for Indiana and northern long‐eared bats

Bat conservation in the eastern United States following the onset of white‐nose syndrome necessitates the conservation and production of important summer habitat required by bats for both diurnal roosting and nocturnal foraging and commuting. Forest management via silvicultural applications can purposely direct forest succession so important habitat features are retained and developed. The effects of timber harvest on habitat at large spatiotemporal scales for a species are not always readily apparent but can be investigated with spatially explicit forest dynamic modeling. Here we used a forest succession model (LANDIS‐II) to simulate future forest conditions under different harvest regimes. We simulated nine harvest scenarios on Indiana State Forests that ranged from a complete cessation of timber harvest to intensive timber extraction. We then applied previously created models of nocturnal and diurnal habitat occupancy for both Indiana and northern long‐eared bats. We found that suitable nocturnal habitat was maximized for Indiana bats but minimized for northern long‐eared bats under low intensity timber harvest scenarios. Among moderate intensity timber harvest scenarios, both species exhibited the greatest amount of suitable nocturnal habitat when timber harvest applications focused on regenerative openings. The quantity of suitable diurnal habitat trended in the opposite direction of nocturnal habitat with selection harvests favoring suitable roosting habitat. Finally, both species displayed a trend in which overall suitable habitat was primarily driven by the degree of suitable diurnal habitat rather than nocturnal habitat. These results highlight the complex nature of managing multiple habitat needs for more than one species. Furthermore, our research illustrates the importance of understanding the distinct habitat requirements associated with different life history needs that can occur within a single species. Despite such complexities, our results can help guide forest management to preserve and encourage suitable habitat for multiple imperiled bat species.

Fire modulates climate change response of simulated aspen distribution across topoclimatic gradients in a semi-arid montane landscape

Changing aspen distribution in response to climate change and fire is a major focus of biodiversity conservation, yet little is known about the potential response of aspen to these two driving forces along topoclimatic gradients. This study is set to evaluate how aspen distribution might shift in response to different climate-fire scenarios in a semi-arid montane landscape, and quantify the influence of fire regime along topoclimatic gradients. We used a novel integration of a forest landscape succession and disturbance model (LANDIS-II) with a fine-scale climatic water deficit approach to simulate dynamics of aspen and associated conifer and shrub species over the next 150 years under various climate-fire scenarios. Simulations suggest that many aspen stands could persist without fire for centuries under current climate conditions. However, a simulated 2–5 °C increase in temperature caused a substantial reduction of aspen coverage at lower elevations and a modest increase at upper elevations, leading to an overall reduction of aspen range at the landscape level. Increasing fire activity may favor aspen increase at its upper elevation limits adjacent to coniferous forest, but may also favor reduction of aspen at lower elevation limits adjacent to xeric shrubland. Our study highlights the importance of incorporating fine-scale terrain effects on climatic water deficit and ecohydrology when modeling species distribution response to climate change. This modeling study suggests that climate mitigation and adaptation strategies that use fire would benefit from consideration of spatial context at landscape scales.

The altitudinal belts of subalpine virgin forest on Mt. Gongga simulated by a succession model

How to accurately simulate the distribution of forest species based upon their biological attributes has been a traditional biogeographical issue. Forest gap models are very useful tools for examining the dynamics of forest succession and revealing the species structure of vegetation. In the present study, the GFSM (Gongga Forest Succession Model) was developed and applied to simulate the distribution, composition and succession process of forests in 100 m elevation intervals. The results indicate that the simulated results of the tree species, quantities of the different types of trees, tree age and differences in DBH (diameter at breast height) composition were in line with the actual situation from 1400 to 3700 MASL (meters above sea level) on the eastern slope of Mt. Gongga. Moreover, the dominant species in the simulated results were the same as those in the surveyed database. Thus, the GFSM model can best simulate the features of forest dynamics and structure in the natural conditions of Mt. Gongga. The work provides a new approach to studying the structure and distribution characteristics of mountain ecosystems in varied elevations. Moreover, the results of this study suggest that the biogeochemistry mechanism model should be combined with the forest succession model to facilitate the ecological model in simulating the physical and chemical processes involved.

Predicted effects of gypsy moth defoliation and climate change on forest carbon dynamics in the New Jersey pine barrens.

Disturbance regimes within temperate forests can significantly impact carbon cycling. Additionally, projected climate change in combination with multiple, interacting disturbance effects may disrupt the capacity of forests to act as carbon sinks at large spatial and temporal scales. We used a spatially explicit forest succession and disturbance model, LANDIS-II, to model the effects of climate change, gypsy moth (Lymantria dispar L.) defoliation, and wildfire on the C dynamics of the forests of the New Jersey Pine Barrens over the next century. Climate scenarios were simulated using current climate conditions (baseline), as well as a high emissions scenario (HadCM3 A2 emissions scenario). Our results suggest that long-term changes in C cycling will be driven more by climate change than by fire or gypsy moths over the next century. We also found that simulated disturbances will affect species composition more than tree growth or C sequestration rates at the landscape level. Projected changes in tree species biomass indicate a potential increase in oaks with climate change and gypsy moth defoliation over the course of the 100-year simulation, exacerbating current successional trends towards increased oak abundance. Our research suggests that defoliation under climate change may play a critical role in increasing the variability of tree growth rates and in determining landscape species composition over the next 100 years.

Slow lifelong growth predisposes Populus tremuloides trees to mortality.

Widespread dieback of aspen forests, sometimes called sudden aspen decline, has been observed throughout much of western North America, with the highest mortality rates in the southwestern United States. Recent aspen mortality has been linked to drought stress and elevated temperatures characteristic of conditions expected under climate change, but the role of individual aspen tree growth patterns in contributing to recent tree mortality is less well known. We used tree-ring data to investigate the relationship between an individual aspen tree's lifetime growth patterns and mortality. Surviving aspen trees had consistently higher average growth rates for at least 100 years than dead trees. Contrary to observations from late successional species, slow initial growth rates were not associated with a longer lifespan in aspen. Aspen trees that died had slower lifetime growth and slower growth at various stages of their lives than those that survived. Differences in average diameter growth between live and dead trees were significant (α = 0.05) across all time periods tested. Our best logistical model of aspen mortality indicates that younger aspen trees with lower recent growth rates and higher frequencies of abrupt growth declines had an increased risk of mortality. Our findings highlight the need for species-specific mortality functions in forest succession models. Size-dependent mortality functions suitable for late successional species may not be appropriate for species with different life history strategies. For some early successional species, like aspen, slow growth at various stages of the tree's life is associated with increased mortality risk.

Predicting impacts of climate change on the aboveground carbon sequestration rate of a temperate forest in northeastern China.

The aboveground carbon sequestration rate (ACSR) reflects the influence of climate change on forest dynamics. To reveal the long-term effects of climate change on forest succession and carbon sequestration, a forest landscape succession and disturbance model (LANDIS Pro7.0) was used to simulate the ACSR of a temperate forest at the community and species levels in northeastern China based on both current and predicted climatic data. On the community level, the ACSR of mixed Korean pine hardwood forests and mixed larch hardwood forests, fluctuated during the entire simulation, while a large decline of ACSR emerged in interim of simulation in spruce-fir forest and aspen-white birch forests, respectively. On the species level, the ACSR of all conifers declined greatly around 2070s except for Korean pine. The ACSR of dominant hardwoods in the Lesser Khingan Mountains area, such as Manchurian ash, Amur cork, black elm, and ribbed birch fluctuated with broad ranges, respectively. Pioneer species experienced a sharp decline around 2080s, and they would finally disappear in the simulation. The differences of the ACSR among various climates were mainly identified in mixed Korean pine hardwood forests, in all conifers, and in a few hardwoods in the last quarter of simulation. These results indicate that climate warming can influence the ACSR in the Lesser Khingan Mountains area, and the largest impact commonly emerged in the A2 scenario. The ACSR of coniferous species experienced higher impact by climate change than that of deciduous species.

Forschung zu Wald und Klimawandel in Mitteleuropa: eine Werkschau

Research on forests and climate change in Central Europe: state of the art How are trees in Central European forests affected by climate change, yesterday, today and tomorrow? To answer this question, 250 researchers met for the international conference “ClimTree 2013” that took place in Zurich in September 2013. The answers are manifold and confirm that knowledge on this subject is not fully consolidated yet. Nevertheless, there is agreement on the two most important factors causing marked changes: aggravated water shortage during the growing season leading to growth and regeneration changes and inducing mortality, and rising temperatures that accelerate both biotic and abiotic processes, in particular pest outbreaks and forest fires. The question which tree species will dominate under future climatic conditions is lively debated due to novel results from experiments and dendroecological studies that have only partially been considered in forest succession models to date. Thus, the discussion on a next generation of such models has started. The present conference report summarizes the state of the art as well as new research questions in this field.

Carbon dynamics in the future forest: the importance of long‐term successional legacy and climate–fire interactions

Understanding how climate change may influence forest carbon (C) budgets requires knowledge of forest growth relationships with regional climate, long-term forest succession, and past and future disturbances, such as wildfires and timber harvesting events. We used a landscape-scale model of forest succession, wildfire, and C dynamics (LANDIS-II) to evaluate the effects of a changing climate (A2 and B1 IPCC emissions; Geophysical Fluid Dynamics Laboratory General Circulation Models) on total forest C, tree species composition, and wildfire dynamics in the Lake Tahoe Basin, California, and Nevada. The independent effects of temperature and precipitation were assessed within and among climate models. Results highlight the importance of modeling forest succession and stand development processes at the landscape scale for understanding the C cycle. Due primarily to landscape legacy effects of historic logging of the Comstock Era in the late 1880s, C sequestration may continue throughout the current century, and the forest will remain a C sink (Net Ecosystem Carbon Balance>0), regardless of climate regime. Climate change caused increases in temperatures limited simulated C sequestration potential because of augmented fire activity and reduced establishment ability of subalpine and upper montane trees. Higher temperatures influenced forest response more than reduced precipitation. As the forest reached its potential steady state, the forest could become C neutral or a C source, and climate change could accelerate this transition. The future of forest ecosystem C cycling in many forested systems worldwide may depend more on major disturbances and landscape legacies related to land use than on projected climate change alone.

Tree Migration-Rates: Narrowing the Gap between Inferred Post-Glacial Rates and Projected Rates

Faster-than-expected post-glacial migration rates of trees have puzzled ecologists for a long time. In Europe, post-glacial migration is assumed to have started from the three southern European peninsulas (southern refugia), where large areas remained free of permafrost and ice at the peak of the last glaciation. However, increasing palaeobotanical evidence for the presence of isolated tree populations in more northerly microrefugia has started to change this perception. Here we use the Northern Eurasian Plant Macrofossil Database and palaeoecological literature to show that post-glacial migration rates for trees may have been substantially lower (60–260 m yr–1) than those estimated by assuming migration from southern refugia only (115–550 m yr–1), and that early-successional trees migrated faster than mid- and late-successional trees. Post-glacial migration rates are in good agreement with those recently projected for the future with a population dynamical forest succession and dispersal model, mainly for early-successional trees and under optimal conditions. Although migration estimates presented here may be conservative because of our assumption of uniform dispersal, tree migration-rates clearly need reconsideration. We suggest that small outlier populations may be a key factor in understanding past migration rates and in predicting potential future range-shifts. The importance of outlier populations in the past may have an analogy in the future, as many tree species have been planted beyond their natural ranges, with a more beneficial microclimate than their regional surroundings. Therefore, climate-change-induced range-shifts in the future might well be influenced by such microrefugia.

Modeling Soil and Biomass Carbon Responses to Declining Water Table in a Wetland-Rich Landscape

Peatlands and forested wetlands can cover a large fraction of the land area and contain a majority of the regional carbon pool in wet northern temperate landscapes. We used the LANDIS-II forest landscape succession model coupled with a model of plant community and soil carbon responses to water table changes to explore the impacts of declining water table on regional carbon pools in a peatland- and wetland-rich landscape in northern Wisconsin, USA. Simulations indicated that both biomass accumulation and soil decomposition would increase as a consequence of drying. In peatlands, simulated water table declines of 100 cm led to large increases in biomass as well as short-term increases in soil carbon, whereas declines of 40 cm led to continuous declines in soil carbon and smaller increases in biomass, with the net result being a loss of total carbon. In non-peat wetlands, biomass accumulation outweighed soil carbon loss for both scenarios. Long-term carbon cycle responses were not significantly affected by the time scale of water table decline. In general, peatland carbon storage over the first 50–150 years following drainage was neutral or increasing due to increased plant growth, whereas carbon storage over longer time scales decreased due to soil carbon loss. Although the simplicity of the model limits quantitative interpretation, the results show that plant community responses are essential to understanding the full impact of hydrological change on carbon storage in peatland-rich landscapes, and that measurements over long time scales are necessary to adequately constrain landscape carbon pool responses to declining water table.

Modeling Forest Mortality Caused by Drought Stress: Implications for Climate Change

Climate change is expected to affect forest landscape dynamics in many ways, but it is possible that the most important direct impact of climate change will be drought stress. We combined data from weather stations and forest inventory plots (FIA) across the upper Great Lakes region (USA) to study the relationship between measures of drought stress and mortality for four drought sensitivity species groups using a weight-of-evidence approach. For all groups, the model that predicted mortality as a function of mean drought length had the greatest plausibility. Model tests confirmed that the models for all groups except the most drought tolerant had predictive value. We assumed that no relationship exists between drought and mortality for the drought-tolerant group. We used these empirical models to develop a drought extension for the forest landscape disturbance and succession model LANDIS-II, and applied the model in Oconto county, Wisconsin (USA) to assess the influence of drought on forest dynamics relative to other factors such as stand-replacing disturbance and site characteristics. The simulations showed that drought stress does affect species composition and total biomass, but effects on age classes, spatial pattern, and productivity were insignificant. We conclude that (for the upper Midwest) (1) a drought-induced tree mortality signal can be detected using FIA data, (2) tree species respond primarily to the length of drought events rather than their severity, (3) the differences in drought tolerance of tree species can be quantified, (4) future increases in drought can potentially change forest composition, and (5) drought is a potentially important factor to include in forest dynamics simulations because it affects forest composition and carbon storage.

Enhancing gap model accuracy by modeling dynamic height growth and dynamic maximum tree height

Gap models are flexible tools for the simulation of forest dynamics under different climatic conditions. An important area, however, has not yet received the attention it deserves: the formulation of height growth and maximum tree height. In most gap models, every tree approaches a fixed maximum height regardless of site conditions, and tree height as such is approximated via stem diameter. To address these issues, we converted maximum height from a parameter to a variable that depends on site-specific climatic conditions. We also established tree height as a separate state variable besides diameter, to allow for competition effects to influence the ratio between height and diameter growth. The new model formulations were tested against data from the Swiss National Forest Inventory (NFI) and from a forest growth and yield research plot. Lastly the new model version was applied to study productivity changes due to climate change along an environmental gradient.The new model formulations increased the accuracy of simulations of stand characteristics without negatively influencing the general applicability of the model. The height/diameter relationship of a Douglas-fir stand in Switzerland simulated with the new model version resembled measurements closely, and biomass simulated along an environmental gradient agreed better with measurements (NFI) when using the new model version. Simulations with site-specific maximum height showed that the maximum heights of the dominant species on the gradient did not differ significantly from NFI data, whereas static maximum heights did.The application of the old and new model versions to simulate productivity under climatic change along the same environmental gradient showed that the conversion of a static parameter such as maximum height to a site-specific variable is not only a desirable, but a crucial feature to incorporate, since climate-induced changes in productivity are simulated to be more pronounced with the new model formulation. We conclude that dynamic height growth and site-specific maximum tree height can significantly improve simulation results of forest succession models, especially with regard to forest management under climate change.

模拟分类经营对小兴安岭林区森林生物量的影响

运用空间直观景观模型LANDIS 7.0 PRO,模拟了在当前采伐模式和无采伐两个预案下,小兴安岭林区森林生物量及主要树种生物量在2000-2200年间的动态。模拟结果如下:(1)无采伐预案下,森林生物量由最初的93.6 t/hm²逐渐升高,90a后达到最大值258 t/hm²,之后森林生物量在245 t/hm²上下小幅波动;(2)前100a采伐预案会明显降低森林生物量,与无采伐预案相比森林生物量最大可降低21.4 t/hm²,平均减少14.7 t/hm²;后100a采伐对森林生物量的影响逐渐减弱,森林生物量平均减少2.6 t/hm²;(3)当前采伐模式促进保护树种红松和紫椴生长,其生物量分别最大可提高9.0 t/hm²和0.53 t/hm²,占到无采伐预案生物量的56%和15%;(4)采伐预案对云冷杉生物量影响较小,主要降低先锋树种(白桦、山杨)和一些阔叶树种(枫桦、春榆)的生物量。研究结果表明现行采伐模式在未来100 a内会显著影响森林生物量,之后其影响逐渐减小,并且保护政策能提高所保护树种(红松、紫椴)的生物量,但要保持较高的总生物量,仍需要降低目前的采伐强度。;Forest biomass is the largest carbon pool among terrestrial ecosystems, which plays an important role in mitigating global climate change through sequestrating carbon dioxide and increasing forested area and biomass. However, the disturbances such as climate change, timber harvesting and fire would affect forest biomass, therefore recently, an increasing attention rises on research of a wide range of disturbances that alter forest biomass and species composition. The forested area of China undergone intensive over-logging until 1998, to recover the forest structure and biomass from the past over-logged state, the government implemented forestry classified management. To reveal the effects of the forest management strategy, especially the timber harvesting on the forest and species biomass, the forest and main tree species biomass were simulated by LANDIS 7.0 PRO in the Xiao Xing' an Mountains in northeastern China, which is one of the three largest forested areas in China and the ecotone between temperate and boreal forest. LANDIS 7.0 PRO is the latest version of LANDIS (a spatially explicit model of forest landscape disturbance, management, and succession), which could simulate the dynamics of forest biomass at landscape scale. The study area covers 1.476×10⁵hm²of forested landscape, and its forest dynamic and biomass were simulated over 200 years with the current forest management and no-harvesting scenarios. The main results show that:(1) The forest biomass in the no-harvesting scenario would increase with the simulation years from 93.6 t/hm², and reach a maximum 258 t/hm² approximately at next 90 year, and then fluctuate with an average 245 t/hm², and the potential biomass for this region is about 258 t/hm²; (2) In next 100 years, with the comparison of no-harvesting scenario, the current harvesting scenario significantly decreases the forest biomass, and the maximum and mean forest biomass decline by 21.4 t/hm²and 14.7 t/hm², respectively. But after the next 100 years, current harvesting does not significantly decrease the forest biomass, anyhow the forest biomass trend to decreasing by 2.6 t/hm² averagely; (3) The current harvesting scenario increases the percentages of Korean pine and Amur linden, their biomass increases by 9.0 t/hm²(56%) and 0.53 t/hm²(15%), respectively under the comparison of no-harvesting scenario; (4) The current harvesting scenario affects highly the biomass of deciduous trees including ribbed birch, Black elm, white birch and wild poplar than the coniferous species including the spruces and Kingan fir which are allowed to be logged; (5)The forestry classified management can maintain the original forest structure like species composition, and promote the protected tree species growth and biomass. In addition, our results would be a good evaluation of current forest management strategy and a valuable guide for establishing a new forest management strategy in future.

Using stochastic simulation to evaluate competing risks of wildfires and fuels management on an isolated forest carnivore

Natural resource managers are often challenged with balancing requirements to maintain wildlife populations and to reduce risks of catastrophic or dangerous wildfires. This challenge is exemplified in the Sierra Nevada of California, where proposals to thin vegetation to reduce wildfire risks have been highly controversial, in part because vegetation treatments could adversely affect an imperiled population of the fisher (Martes pennanti) located in the southern Sierra Nevada. The fisher is an uncommon forest carnivore associated with the types of dense, structurally complex forests often targeted for fuel reduction treatments. Vegetation thinning and removal of dead-wood structures would reduce fisher habitat value and remove essential habitat elements used by fishers for resting and denning. However, crown-replacing wildfires also threaten the population’s habitat, potentially over much broader areas than the treatments intended to reduce wildfire risks. To investigate the potential relative risks of wildfires and fuels treatments on this isolated fisher population, we coupled three spatial models to simulate the stochastic and interacting effects of wildfires and fuels management on fisher habitat and population size: a spatially dynamic forest succession and disturbance model, a fisher habitat model, and a fisher metapopulation model, which assumed that fisher fecundity and survivorship correlate with habitat quality. We systematically varied fuel treatment rate, treatment intensity, and fire regime, and assessed their relative effects on the modeled fisher population over 60 years. After estimating the number of adult female fishers remaining at the end of each simulation scenario, we compared the immediate negative effects of fuel treatments to the longer-term positive effect of fuel treatment (via reduction of fire hazard) using structural equation modeling. Our simulations suggest that the direct, negative effects of fuel treatments on fisher population size are generally smaller than the indirect, positive effects of fuel treatments, because fuels treatments reduced the probability of large wildfires that can damage and fragment habitat over larger areas. The benefits of fuel treatments varied by elevation and treatment location with the highest net benefits to fisher found at higher elevations and within higher quality fisher habitat. Simulated fire regime also had a large effect with the largest net benefit of fuel treatments occurring when a more severe fire regime was simulated. However, there was large uncertainty in our projections due to stochastic spatial and temporal wildfires dynamic and fisher population dynamics. Our results demonstrate the difficulty of projecting future populations in systems characterized by large, infrequent, stochastic disturbances. Nevertheless, these coupled models offer a useful decision-support system for evaluating the relative effects of alternative management scenarios; and uncertainties can be reduced as additional data accumulate to refine and validate the models.

Tree species richness promotes productivity in temperate forests through strong complementarity between species

Understanding the link between biodiversity and ecosystem functioning (BEF) is pivotal in the context of global biodiversity loss. Yet, long-term effects have been explored only weakly, especially for forests, and no clear evidence has been found regarding the underlying mechanisms. We explore the long-term relationship between diversity and productivity using a forest succession model. Extensive simulations show that tree species richness promotes productivity in European temperate forests across a large climatic gradient, mostly through strong complementarity between species. We show that this biodiversity effect emerges because increasing species richness promotes higher diversity in shade tolerance and growth ability, which results in forests responding faster to small-scale mortality events. Our study generalises results from short-term experiments in grasslands to forest ecosystems and demonstrates that competition for light alone induces a positive effect of biodiversity on productivity, thus providing a new angle for explaining BEF relationships.