Mapping forest dynamics under climate change: A matrix model

Global climate change may be affecting forests around the world. However, the impact of climate change on forest population dynamics, especially at the landscape or regional level, has hardly been addressed before. A new methodology was proposed to enable matrix transition models to account for climate impact on forest population dynamics. The first climate-sensitive matrix (CSMatrix) model was developed for the Alaska boreal forest based on observations from over 15 years of forest inventory. The spatially explicit model was used to map climate-induced forest population dynamics across the region. The model predicted that the basal area increment in the region under natural succession would be hindered by global warming, more so for dry upland areas than for moist wetlands. It was suggested that temperature-induced drought stress could more than offset a predicted increase of future precipitation in the region to lower overall forest productivity. At the same time, stand diversity would increase across the region through transient species redistribution. Accounting for climate conditions made the CSMatrix model more accurate than conventional matrix models.     

Determining the optimal selective harvest strategy for mixed-species stands with a transition matrix growth model

An optimization model was developed to determine the optimal harvesting strategy needed for uneven-aged mixed-species stands in the Changbai Mountain region of northeast of China. The model takes into account four variables including residual basal area (RBA), the diameter of the largest tree, harvest cycle and a constant representing the ratio of the number of trees in a given diameter class to those in the next larger diameter class (‘q’). According to model simulations, under the objective of maximizing net revenue, the optimal harvesting strategy is defined when the residual basal area equals to 19 m² ha⁻¹, the diameter of the largest tree equals to 44 cm, q 1.3 and the harvest cycle equals to 20 years. If the objective is to maximize the total volume yield, the optimal harvesting strategy is defined when RBA equals to 13 m² ha⁻¹, the diameter of the largest tree equals to 36 cm and the constant ‘q’ equals to 1.9 and the harvest cycle equals to 15 years.     

Understanding plantation transformation using a size-structured spatial population model

Plantation transformation is a goal of increasing interest to silviculturalists. The target forest state is characterised by high variance in age and size, and an irregular spatial structure, which leads to inhomogeneous interactions between, and consequent development of, trees in the stand. This presents a difficulty for traditional methods such as yield tables, and demands a more careful consideration of stand dynamics. On the other hand, while forestry has a great heritage of simulation, the level of complexity implemented at an individual level generally precludes direct understanding of stand scale behaviours, and leads to difficulties in verification with appropriate data.A promising approach is the application of relatively simple models developed by ecologists. These can be adapted to yield accurate representations of forest stands, while being highly amenable to analysis. Motivated by data from Scots pine (Pinus sylvestris L.) stands, we here apply a simple spatial birth-death-growth model to the comparison and analysis of transformation strategies for plantation stands. The model captures the effects of neighbours in a way which retains the conceptual simplicity of a generic, analytically solvable model, while allowing insights into the driving factors of population dynamics.Timing and intensity of management interventions, as opposed to their specific criteria, are of primary importance: thinnings of a moderate intensity performed over a long period produced the best results. Variation in the strategy applied leads to more subtle effects which transformation strategies must also take into account, such as the development of variation in size of the remaining trees (increased using spatially correlated thinnings), the survival chances of regeneration and “underplanted” trees, and the overall productivity of the stand (increased using spatially homogeneous crown thinning). Finally, we demonstrate the robustness of model predictions to fundamental choices of model formulation.     

Dynamics and management of Alaska boreal forest: An all-aged multi-species matrix growth model

Studies on the dynamics of Alaska boreal forest are sporadic and rare, and forest management in the region has been conducted in the absence of a useful growth model. This paper presents a matrix stand growth model to study the dynamics and management of Alaska's boreal forest, with harvests and artificial regeneration being accounted for. The model was calibrated with data from 446 constantly monitored permanent sample plots distributed across interior and south-central Alaska, and was tested to be accurate on an independent validation sample. The present model was applied on a most frequent commercial stand in interior Alaska to study a forest management regime that is being commonly used in the region. The simulation was for 300 years with a 40-year cutting cycle, and management outcomes under various permafrost levels and site elevations were investigated with sensitivity analysis. Despite the comparatively low financial returns, current management regime may generally benefit wildlife species by maintaining continuous forest cover and decent stand diversity, and properly managed forests had potential for timber production and wood-based energy. It was predicted by the model that both permafrost and site elevation had substantial impact on the management outcomes. Other variables being held constant at sample mean, net present value of harvests increased from $434 to $831 ha⁻¹ and the annual volume of harvest more than tripled from 1.68 to 5.75 m³ ha⁻¹ y⁻¹ as permafrost declined from obvious to unlikely. Managers were also advised to focus on stands on medium elevation (300 m), as stands on lower or higher elevations were expected to produce less harvested volume and net present value. For rural Alaska communities suffering from expensive heating costs, it was suggested that approximately 20 ha of properly managed forest could sustain a household's annual heating requirement, while continuous forest coverage and decent diversity could still be maintained.     

A transition matrix growth model for uneven-aged mixed-species forests in the Changbai Mountains,northeastern China

A transition matrix growth and an ingrowth model were developed and applied to an uneven-aged mixed-species forest in the Changbai Mountains, northeastern of China. Results indicate that the constant-parameter transition probabilities for all species in the mixed uneven-aged forest could be classified into three groups based on the mean upgrowth probabilities of each species. Constant-parameter transition probabilities of all species in each diameter class fluctuate within a narrow range except for diameter classes below 8 cm and greater than 60 cm. Variable-parameter transition probabilities were found to be a function of residual basal area for small diameter classes. For large trees, transition probabilities are not affected by the residual basal area. Based on this study, variable-parameter transition probabilities for large diameter trees can be replaced with constant-parameter transition probabilities. In addition, a new ingrowth model was developed and the new ingrowth model was shown to perform better than existing ingrowth model used in the region.     

林分模拟径阶株数法确定小班蓄积的试验

利用数学模拟方法对小班林木径阶株数分布和小班蓄积量进行了模拟试验，结果表明：模拟法与标准地实测法差异不显著，且模拟法具有实用性强、生产使用方便、能充分发挥计算机的优越性等特点，可以快速模拟出林分的直径分布，为林业调查提供了快捷有效的技术手段。     

Simulation of the vegetation structure and function in a Malaysian tropical rain forest using the individual-based dynamic vegetation model SEIB-DGVM

An individual-based Dynamic Global Vegetation Model, the SEIB-DGVM, was adapted to a Malaysian tropical rain forest by incorporating formulas and parameters from a gap dynamics model, FORMIX3. After calibration, the model reconstructed forest structure (i.e., size structure, leaf area index, and woody biomass) and carbon fluxes (i.e., gross and net primary productivity) of a dipterocarp forest in Pasoh, Peninsular Malaysia. Sensitivity analysis demonstrated that the model was robust; forest structure and ecosystem functions moderately fluctuated due to changes in parameters and climatic environments. Sensitivity analysis also indicated that the success and decay of a dominant species group that monopolized the canopy layer greatly affected those of a less abundant, shade-intolerant group. This result indicates that even if environmental changes do not exhibit clear effects on dominant canopy species and/or whole forest structure, such changes may still substantially impact the biodiversity of subdominant species. In simulations without gap formation, woody biomass was overestimated and a shade-intolerant species group was eliminated. This finding indicates that incorporating gap formation into the individual-based model is essential for the appropriate simulation of forest biomass and biodiversity in this Malaysian tropical rain forest.     

长白山北坡森林群落交错区优势树种动态

基于28个20mx90m样地的调查数据,利用Lotka-Volterra模型,本文分析了长白山北坡阔叶红松(Pinuskoraiensis)林和云冷杉林(也叫暗针叶林)群落交错区优势树种之间的竞争及动态。结果显示:在自然条件下,群落将向两个方向分化,一是以云杉(PiceajezoensisandP.koraiensis)和冷杉(Abiesnephrolepis)为优势的群落,并在达到平衡时冷杉占绝对优势(相对优势度的77.1%):另一种是以红松或云冷杉和阔叶树占绝对优势的针阔混交林,并在达到平衡时,阔叶树在阔叶红松林中占相对优势度的50%,在云冷杉一阔叶林类型中占66%。同时,本研究说明:(1)阔叶红松林和云冷杉林都是长白山气候顶极群落:(2)交错区具有过渡性质:(3)森林群落的分化结果说明演替的方向受局部生境的影响。图1表3参24。     

Dynamics of dominant tree species in a forest ecotone on the northern slop of Changbai Mountain

The competition and dynamics of dominant trees species in the forest ecotone between the broad-leaved/Korean pine （Pinus koraiensis） mixed forest and the spruce-fir forest （also known as dark conifer forest） in Changbai Mountain, Jilin Province in Northeast China were studied by using Lotka-Volterra model, based on the data from twenty-eight sample plots with area of 20 mx90 m for each one. Results showed that under natural condition, differentiation of communities followed two directions： one would be Spruce （Picea jezoensis and few P. koraiensis） and fir （Abies nephrolepis） co-dominant conifer forest, and at the equilibrium fir was absolutely preponderant （77.1% of relative dominance （RD））; the other would be the conifer and broad-leaved mixed forest, and at equilibrium, the broad-leaved tree species was 50% of RD in the broad-leaved/Korean pine mixed forest and 66% of RD in the broad-leaved and spruce-fir mixed forest. The study demonstrated that both broad-leaved/Korean pine mixed forest and dark conifer forest were climax community, the ecotone had transitional characteristics, and the diversification of the forest communities suggested that the direction of succession was affected by local habitat.     

Adaptation of the LIGNUM model for simulations of growth and light response in Jack pine

LIGNUM is a whole tree model, developed for Pinus sylvestris in Finland, that combines tree metabolism with a realistic spatial distribution of morphological parts. We hypothesize that its general concepts, which include the pipe model, functional balance, yearly carbon budget, and a set of architectural growth rules, are applicable to all trees. Adaptation of the model to Pinus banksiana, a widespread species of economic importance in North America, is demonstrated.

Conversion of the model to Jack pine entailed finding new values for 16 physiological and morphological parameters, and three growth functions. Calibration of the LIGNUM Jack pine model for open grown trees up to 15 years of age was achieved by matching crown appearance and structural parameters (height, foliage biomass, aboveground biomass) with those of real trees. A sensitivity study indicated that uncertainty in the photosynthesis and respiration parameters will primarily cause changes to the net annual carbon gain, which can be corrected through calibration of the growth rate. The effect of a decrease in light level on height, biomass, total tree branch length, and productivity were simulated and compared with field data. Additional studies yielded insight into branch pruning, carbon allocation patterns, crown structure, and carbon stress. We discuss the value of the LIGNUM model as a tool for understanding tree growth and survival dynamics in natural and managed forests.     

Simulation study of the vegetation structure and function in eastern Siberian larch forests using the individual-based vegetation model SEIB-DGVM

The global ecosystem model SEIB-DGVM was adapted for an eastern Siberian larch forest through incorporation of empirical rules of allometry, allocation, and phenology developed for a larch stand at the Spasskaya-pad tower site, Yakutsk, Russia. After calibration, the model reconstructed post-fire successional patterns of forest structure and carbon cycling. It also reconstructed seasonal changes in carbon, water, and energy cycling in a mature larch forest. Sensitivity analysis showed that simulated functional properties of forest (LAI, NPP, carbon pools, and water runoff) are mainly determined by climatic environment, and population dynamic parameters (i.e., parameters for establishment and mortality) plays only minor role on them. Sensitivity analysis also showed that plant productivity and biomass were mainly limited by available water at Spasskaya-pad, where mean annual precipitation is only 257 mm. In the model, higher air temperature increases plant productivity via extension of growing season, and decreases plant productivity via causing drought and higher respiration. We found that the net effect is reduction of productivity, suggesting a possibility that global warming induces decrement of plant productivity in eastern Siberian larch forests.     

Estimating biomass production and carbon storage for a fast-growing makino bamboo (Phyllostachys makinoi) plant based on the diameter distribution model

The purpose of this study was to estimate biomass and carbon storage for a fast-growing makino bamboo (Phyllostachys makinoi). The study site was located in central Taiwan and the makino bamboo plantation had a stand density of 21191 ± 4107 culms ha⁻¹. A diameter distribution model based on the Weibull distribution function and an allometric model was used to predict aboveground biomass and carbon storage. For an accurate estimation of carbon storage, the percent carbon content (PCC) in different sections of bamboo was determined by an elemental analyzer. The results showed that bamboos of all ages shared a similar trend, where culms displayed a carbon storage of 47.49–47.82%, branches 45.66–46.23%, and foliage 38.12–44.78%. In spite of the high density of the stand, the diameter distribution of makino bamboo approached a normal distribution and aboveground biomass and carbon storage were 105.33 and 49.81 Mg ha⁻¹, respectively. Moreover, one-fifth of older culms from the entire stand were removed by selective cutting. If the distribution of the yield of older culms per year was similar to the current stand, the yields of biomass and carbon per year would be 21.07 and 9.89 Mg ha⁻¹ year⁻¹. An astonishing productivity was observed, where every 5 years the yield of biomass and carbon was equal to the current status of stockings. Thus, makino bamboo has a high potential as a species used for carbon storage.     

Simulating restoration strategies for a southern boreal forest landscape with complex land ownership patterns

Restoring altered forest landscapes toward their ranges of natural variability (RNV) may enhance ecosystem sustainability and resiliency, but such efforts can be hampered by complex land ownership and management patterns. We evaluated restoration potential for southern-boreal forests in the ∼2.1 million ha Border Lakes Region of northern Minnesota (U.S.A.) and Ontario (Canada), where spatially distinct timber harvest and fire suppression histories have differentially altered forest conditions (composition, age–class distribution, and landscape structure) among major management areas, effectively resulting in forest landscape “bifurcation.” We used a forest landscape simulation model to evaluate potential for four hypothetical management and two natural disturbance scenarios to restore forest conditions and reduce bifurcation, including: (1) a current management scenario that simulated timber harvest and fire suppression practices among major landowners; (2) three restoration scenarios that simulated combinations of wildland fire use and cross-boundary timber harvest designed to emulate natural disturbance patterns; (3) a historical natural disturbance scenario that simulated pre-EuroAmerican settlement fire regimes and windthrow; and (4) a contemporary fire regime that simulated fire suppression, but no timber harvest. Forest composition and landscape structure for a 200-year model period were compared among scenarios, among major land management regions within scenarios, and to six RNV benchmarks. The current management scenario met only one RNV benchmark and did not move forest composition, age–class distribution, or landscape structures toward the RNV, and it increased forest landscape bifurcation between primarily timber-managed and wilderness areas. The historical natural disturbance scenario met five RNV benchmarks and the restoration scenarios as many as five, by generally restoring forest composition, age–class distributions, and landscape structures, and reducing bifurcation of forest conditions. The contemporary natural disturbance scenario met only one benchmark and generally created a forest landscape dominated by large patches of late-successional, fire-prone forests. Some forest types (e.g., white and red pine) declined in all scenarios, despite simulated restoration strategies. It may not be possible to achieve all objectives under a single management scenario, and complications, such as fire-risk, may limit strategies. However, our model suggests that timber harvest and fire regimes that emulate natural disturbance patterns can move forest landscapes toward the RNV.     

Calibrating and testing a gap model for simulating forest management in the Oregon Coast Range

The complex mix of economic and ecological objectives facing today's forest managers necessitates the development of growth models with a capacity for simulating a wide range of forest conditions while producing outputs useful for economic analyses. We calibrated the gap model ZELIG to simulate stand-level forest development in the Oregon Coast Range as part of a landscape-scale assessment of different forest management strategies. Our goal was to incorporate the predictive ability of an empirical model with the flexibility of a forest succession model. We emphasized the development of commercial-aged stands of Douglas-fir, the dominant tree species in the study area and primary source of timber. In addition, we judged that the ecological approach of ZELIG would be robust to the variety of other forest conditions and practices encountered in the Coast Range, including mixed-species stands, small-scale gap formation, innovative silvicultural methods, and reserve areas where forests grow unmanaged for long periods of time. We parameterized the model to distinguish forest development among two ecoregions, three forest types and two site productivity classes using three data sources: chronosequences of forest inventory data, long-term research data, and simulations from an empirical growth-and-yield model. The calibrated model was tested with independent, long-term measurements from 11 Douglas-fir plots (6 unthinned, 5 thinned), 3 spruce-hemlock plots, and 1 red alder plot. ZELIG closely approximated developmental trajectories of basal area and large trees in the Douglas-fir plots. Differences between simulated and observed conifer basal area for these plots ranged from −2.6 to 2.4 m²/ha; differences in the number of trees/ha ≥50 cm dbh ranged from −8.8 to 7.3 tph. Achieving these results required the use of a diameter-growth multiplier, suggesting some underlying constraints on tree growth such as the temperature response function. ZELIG also tended to overestimate regeneration of shade-tolerant trees and underestimate total tree density (i.e., higher rates of tree mortality). However, comparisons with the chronosequences of forest inventory data indicated that the simulated data are within the range of variability observed in the Coast Range. Further exploration and improvement of ZELIG is warranted in three key areas: (1) modeling rapid rates of conifer tree growth without the need for a diameter-growth multiplier; (2) understanding and remedying rates of tree mortality that were higher than those observed in the independent data; and (3) improving the tree regeneration module to account for competition with understory vegetation.     

A forest planning model for continuous employment in a forested village with primarily young stands in Korea

This paper presents a practical forest planning approach for continuous forest-based employment in a forested village with primarily young stands. The model is designed to find the practice level for continuous forest employment which embraces both the goal of maximizing the total forest employment and the constraint of maintaining its annual balance, considering forest size and condition, and budget available for forest practice. Through controlling the practice level with the help of a desired employment effect that contributes to allocating forest practices equally to each plan year, a marginal practice level can be found under which any practice level fulfills the goal and constraints. The potential practice area, which is determined by forest area, stand age, and practice schedule, contributes to determining the area silviculturally available for forest practice. Our forest planning model is focused on the planning of young forests which are not expected to yield merchantable products in the near term. The model can also be characterized by landscape-level forest planning in which stand-level practices are planned for achieving a forest-level goal of continuous forest employment. Thus, the model can serve as a basic planning tool for maintaining healthy forests as well as continuous forest employment in young forest areas, where forest-level goals are predicated on stand level practices.     

Individual tree diameter increment model for managed even-aged stands of ponderosa pine throughout the western United States using a multilevel linear mixed effects model

A diameter increment model is developed and evaluated for individual trees of ponderosa pine throughout the species range in the United States using a multilevel linear mixed model. Stochastic variability is broken down among period, locale, plot, tree and within-tree components. Covariates acting at tree and stand level, as breast height diameter, density, site index, and competition indices are included in the model as fixed effects in order to explain residual variability. The data set used in this study came from long-term permanent research plots in even-aged, pure stands both planted and of natural origin. The data base consists of six levels-of-growing stock studies supplemented by initial spacing and other permanent-plot thinning studies for a total of 310 plots, 34,263 trees and 153,854 observations. Regression analysis is the preferred technique used in growth and yield modeling in forestry. We choose the mixed effects models instead of the regression analysis approach because it allows for proper treatment of error terms in a repeated measures analysis framework. Regional growth and yield models exist for ponderosa pine. However, data collection and analysis procedures differ. As a result, comparisons of growth responses that may be due to geographic variation of the species are not possible. Our goal is to present a single distance-independent diameter increment model applicable throughout the geographic range of ponderosa pine in the United States and by using only data from long-term permanent plots on sites capable of the productivity estimated by Meyer [Meyer, W.H., 1938. Yield of Even-Aged Stands of Ponderosa Pine. US Department of Agriculture Technical Bulletin 630].     

The impact of SFM-certification on forest product markets in Western Europe — an analysis using a forest sector simulation model

In the international discussion on labels for sustainably produced wood products based on the certification of sustainable forest management (SFM), little attention has been paid to what is probably the most crucial part of any market-based instrument: the potential impact on forest products markets. This paper analyses the potential impact of SFM-certification on forest products markets using a simulation model of the Western European forest sector. Two scenarios with assumptions regarding certification (chain-of-custody costs, timber supply reduction from certified forests) are projected for the period 1995–2015 and tested against the results of a base scenario (‘business as usual’). In general, the results show that rather modest changes are to be expected from SFM-certification in forest products markets. The market impact of a timber supply reduction from certified forest would be more distinct than the impacts of chain-of-custody costs. Industry gross profits would decrease more than production. Due to the large share of roundwood costs in total costs, the sawmill industry would be affected more by even small changes in raw-material prices than the panel and paper industry.     

Improving the establishment submodel of a forest patch model to assess the long-term protective effect of mountain forests

Simulation models such as forest patch models can be used to forecast the development of forest structural attributes over time. However, predictions of such models with respect to the impact of forest dynamics on the long-term protective effect of mountain forests may be of limited accuracy where tree regeneration is simulated with little detail. For this reason, we improved the establishment submodel of the ForClim forest patch model by implementing a more detailed representation of tree regeneration. Our refined submodel included canopy shading and ungulate browsing, two important constraints to sapling growth in mountain forests. To compare the old and the new establishment submodel of ForClim, we simulated the successional dynamics of the Stotzigwald protection forest in the Swiss Alps over a 60-year period. This forest provides protection for an important traffic route, but currently contains an alarmingly low density of tree regeneration. The comparison yielded a significantly longer regeneration period for the new model version, bringing the simulations into closer agreement with the known slow stand dynamics of mountain forests. In addition, the new model version was applied to forecast the future ability of the Stotzigwald forest to buffer the valley below from rockfall disturbance. Two scenarios were simulated: (1) canopy shading but no browsing impact, and (2) canopy shading and high browsing impact. The simulated stand structures were then compared to stand structure targets for rockfall protection, in order to assess their long-term protective effects. Under both scenarios, the initial sparse level of tree regeneration affected the long-term protective effect of the forest, which considerably declined during the first 40 years. In the complete absence of browsing, the density of small trees increased slightly after 60 years, raising hope for an eventual recovery of the protective effect. In the scenario that included browsing, however, the density of small trees remained at very low levels. With our improved establishment submodel, we provide an enhanced tool for studying the impacts of structural dynamics on the long-term protective effect of mountain forests. For certain purposes, it is important that predictive models of forest dynamics adequately represent critical processes for tree regeneration, such as sapling responses to low light levels and high browsing pressure.     

Gentan probability analysis with a state-dependent discrete forest growth model

The previous stochastic models applied for Gentan probability estimation utilized either a stationary or nonstationary Poisson process to describe the forest owners’ harvesting behavior by means of the counting process. A nonstationary Poisson process has the advantage over a stationary Poisson process of capturing a time-dependent change of harvesting events. However, a nonstationary Poisson process can lack one preferred characteristic of the probability theory when utilizing an average growth function with an asymptotic nature of growth. That is, the sum of the derived Gentan probabilities over time does not always become unity. In this paper, we introduce a state-dependent discrete forest growth model with an asymptotic nature of growth to overcome the problem, then propose a stochastic model applied for Gentan probability estimation. The Mitscherlich type growth function is utilized. The derived probability law to capture the harvesting behavior is shown to be the binomial probability law. The derived probabilities prove to sum up to unity over time.