A management planning system for even-aged and uneven-aged forests in northeast China

The most common scientific approach to numerical landscape-level forest management planning is combinatorial optimization aimed at finding the optimal combination of the treatment alternatives of stands. The selected combination of treatments depends on the conditions of the forest, and the objectives of the forest landowners. A two-step procedure is commonly used to derive the plan. First, treatment alternatives are generated for the stands using an automated simulation tool. Second,the optimal combination of the simulated treatment schedules is found by using mathematical programming or various heuristics. Simulation of treatment schedules requires models for stand dynamics and volume for all important tree species and stand types present in the forest.A forest planning system was described for Northeast China. The necessary models for stand dynamics and tree volume were presented for the main tree species of the region. The developed models were integrated into the simulation tool of the planning system. The simulation and the optimization tools of the planning system were described. The optimization tool was used with heuristic methods, making it possible to easily solve also spatial forest planning problems, for instance aggregate cuttings.Finally, the use of the system is illustrated with a case study, in which nonspatial and spatial management plans are developed for the Mengjiagang Forest District.     

Inventory and modelling for forests in transition from even-aged to uneven-aged management

In plantation forestry, as well as in forests managed according to the single tree selection system (Plenter forest), there are well established methods available to control sustainable management in terms of timber resources. If a shift from even-aged to uneven-aged management is intended, there is usually a lack of a clear, numerically defined aim. Then individual tree growth models help to (i) check if certain aims can be achieved at all and (ii) to define these aims more clearly and numerically, e.g. in terms of structural indices. Regular inventories, based on permanent sample plots, help to determine deviations from these aims. As a feedback of these results, management may be changed or aims may be adjusted. Two forest management districts in Austria were investigated. In one of them, continuous cover forestry was intended where, as soon as regeneration has reached a certain height, the upper layer was removed. In the other case, individual tree harvesting has been performed for 30 years, and a single tree selection system is intended. In both cases, permanent inventories based on angle-count sampling have been installed and re-measured at least once after 10 years. Using the individual tree simulator PrognAus it is shown, that the intended management strategy for the single tree selection system leads to an equilibrium of harvests and growth after about 80 years, accompanied by the intended high structural diversity of the stands, while species diversity and between-stand variation cannot be enhanced by much. In the natural regeneration system without single tree selection, species diversity, structural diversity and between-stand variation is enhanced, but during the 100 years simulated no equilibrium between harvests can be reached. Periods where there is a lack of large timber to be harvested occur regularly. From these examples it is concluded that inventories with permanent sample plots, together with individual tree growth simulators are appropriate tools to evaluate forest management changes.     

Dynamics of seedling establishment and survival in uneven-aged boreal forests

The aim of this study was to describe the dynamics of seedling establishment and development in spruce-dominated uneven-aged boreal forests. The study was based on empirical data from 15 stands with permanent plots, which had been intensively monitored for 10 years in southern Finland. All trees (height > 1.3 m) were measured every fifth year. Regeneration was measured on 64 permanent sample plots (4 m²) in each stand. The establishment of first-year seedlings was analysed on a yearly basis. The survival and development of older Norway spruce (Picea abies (L.) H. Karst.) seedlings were analysed based on observations made every five years. The establishment of spruce seedlings was closely correlated with the abundance of seed crops. Seedling cohorts originating from abundant seed crops were clearly detectable in the development of seedling height distributions over time. It took about 15 years for spruce seedlings to reach a height level of 15-30 cm. Local basal area had hardly any effect on the emergence or survival of small spruce seedlings, while the number of higher spruce seedlings decreased with increasing local basal area.     

Spatial distribution of regeneration in West-Carpathian uneven-aged silver fir forests

The objective of our study was to examine whether distribution of regeneration in uneven-aged fir (Abies alba Mill.) forests is related to the spatial pattern of trees. In 12 sample plots of size 0.45–1.00 ha (in total 8.65 ha, with stand basal areas ranging from 27.6 m² ha^–1 to 39.5 m² ha^–1), all live and dead trees above 5 cm in d_1.3 were mapped and their diameters measured. In eight plots, all live and dead fir saplings were mapped. In three plots, the number of live fir saplings and seedlings was registered on small systematically distributed circular plots. The values of an analytically developed index of stand influence were compared in patches occupied and unoccupied by live or dead fir regeneration. Contrary to preliminary assumptions, only in a few cases did saplings and trees 5–15 cm in d_1.3 appear more often in gaps and looser stand patches. Rather, in many plots, the opposite tendency was observed. The seedling density showed a weak but positive correlation with the index of influence. If the spatial pattern of regeneration reflects the spatially varying mortality of juvenile trees, then no evidence was found that stand competition was the most important factor inducing this mortality. On the contrary, on the basis of the results obtained, we can presume that the survival rate of juvenile firs was higher in patches with a relatively higher local basal area. Thus, it was hypothesised that, first, dispersion of regeneration in uneven-aged fir forests is controlled by easy-to-change edaphic factors such as humus form and acidity of the upper soil horizons, and second, that these soil features are linked with the spatial pattern of trees.     

Silvicultural systems for southern bottomland hardwood forests

Silvicultural systems integrate both regeneration and intermediate operations in an orderly process for managing forest stands. The clearcutting method of regeneration favors the development of species that are moderately intolerant to intolerant of shade. In fact, clearcutting is the most proven and widely used method of successfully regenerating bottomland oak species in the South. The seed-tree method of regeneration favors the establishment of light-seeded species. Mechanical soil scarification may be necessary if the desired species requires bare mineral soil for establishment. The shelterwood method of regeneration can provide for the development of heavy-seeded species, but has produced highly variable results with southern bottomland oaks. The single-tree selection method of regeneration favors the development of shade-tolerant species. When single-tree selection is applied repeatedly to stands containing commercially valuable shade-intolerant species, composition will gradually shift to less-valuable, more-tolerant species. Consequently, the single-tree selection method of regeneration is not recommended for any commercially valuable bottomland hardwood tree species. Group selection, in its strictest application, creates only small openings that usually fail to allow sufficient light to the forest floor for satisfactory establishment and development of shade-intolerant bottomland species. Patch cutting, a combination of uneven-aged (group selection) and even-aged (clearcutting) silviculture, designed to create larger openings, has been successfully used to produce an uneven-aged stand that consists of many small, irregularly shaped, even-aged groups. Silvicultural systems should include a planned program of intermediate operations designed to enhance the growth and development of those species favored during the regeneration process. Improvement cutting and commercial thinning are increasingly common in southern bottomland hardwood forests. Other partial cuttings employed today in bottomland hardwood forests typically involve some form of crop-tree release. Specific recommendations for the selection of silvicultural systems are presented for the eight most important species groups found in southern bottomland hardwood forests.     

Forecasting development of understory American beech after partial cutting in uneven-aged northern hardwood stands

American beech (Fagus grandifolia Ehrh.) in the understory of northern hardwood stands can interfere with the development of more desirable species such as sugar maple (Acer saccharum Marsh.). Yet, managers have had only limited methods for identifying stands where beech might dominate a new cohort. We examined five uneven-aged stands in New York State to determine the degree of influence that understory beech has on species development after a cutting treatment. No significant differences between stands were found, allowing us to develop a single model for evaluation. Understory beech was assessed using a species index value (SIV), which measures the proportion of stems, weighted by height, for a species on a milacre plot. We used a 5×5 transition matrix to compare pre- and post-cut beech importance levels. Stand-level trends showed an overall increase in the proportion of sample plots with higher levels of understory beech after cutting, with the likelihood of change on individual plots dependent on their pre-cut status. Plots with either no beech or very high levels of beech changed little after cutting, while beech was more likely to reach critical levels of dominance when pre-cut SIV was medium or higher. The transition matrix gives forest managers a means to forecast the probable level of future beech importance following cutting, based upon precursor conditions.     

Optimal management of uneven-aged Norway spruce stands

An optimization model is specified to analyze forest management without any restrictions on the forest management system. The data on forest growth comes from unique field experiments and is used to estimate a nonlinear transition matrix or size-structured model for Norway spruce. The objective function includes detailed harvesting cost specifications and the optimization problem is solved in its most general dynamic form. In optimal uneven-aged management, stand density is shown to be dominated by limitations in natural regeneration. If the goal is volume maximization, even-aged management with artificial regeneration (and thinnings from above) is superior to uneven-aged management. After including regeneration and harvesting costs, the interest rate, and the price differential between saw timber and pulpwood, uneven-aged management becomes superior to even-aged management. However, in the short term the superiority is conditional on the initial stand state.     

异龄林经营决策优化

从林分密度、树种组成、林分直径分布、转换决策 (包括择伐周期与转换期长度 )等方面对异龄林经营决策优化进行了研究。     

Effects of forest management on structural features important for biodiversity in mixed-age hardwood forests in Australia's subtropics

The contiguous forest landscapes of the Brigalow Belt Bioregion in Australia's subtropics, known as ‘the western hardwood forests’ are thought to be important for biodiversity conservation through the provision of continuous habitat features in an otherwise extensively cleared region. However, these forests have a long management history, as they are also important for timber production and stock grazing. Knowledge of the effect of these and other disturbances on the distribution and abundance of key structural or habitat features are limited and forest management activities thus continue uninformed. To address this knowledge gap, we investigated the effects of prescribed and non-prescribed disturbances on the distribution and abundance of six key habitat features (live and dead trees with hollows, large mature live trees, shrub abundance, downed coarse woody debris and litter cover) at 120 sites located in spotted gum Corymbia citriodora dominant forests within the western hardwoods.     

Determination of optimal rotation period for management of lumbering forests in Kenya

This study estimates the optimal rotation period of various tree species in Kenya and applies it in the management of lumbering forests through optimal synchronization of forest plantations to achieve a steady supply to lumbering firms. The optimal rotation period of three tree species, pine, cypress, and eucalyptus, was estimated using data from Kenya Forest Service. A combined application of Chang simple production model and ? Faustmann? model? reveals the optimal biological harvest age is 25 years for pine, 25 years for cypress, and 14 years for eucalyptus. However, introducing the prices and using the Faustmann optimal rotation model at the current market interest rate of 10.5%, the Faustmann rotation age for pine stand will be maximized at 12.67 years, cypress at 23.5 years, and eucalyptus at 38.4 years. The research further indicates significant variability in land expectation value and soil rent of various species and proposes an inclusion of “species” as a variable in forest land valuation. In the conclusion, nonmarket factors affecting the optimal yield were further explained and recommendations on sustainable yield production were suggested.     

Restoration of bottomland hardwood forests across a treatment intensity gradient

Large-scale restoration of bottomland hardwood forests in the Lower Mississippi Alluvial Valley (USA) under federal incentive programs, begun in the 1990s, initially achieved mixed results. We report here on a comparison of four restoration techniques in terms of survival, accretion of vertical structure, and woody species diversity. The range of treatment intensity allowed us to compare native recolonization to direct seeding and planting of Quercus nuttallii Palmer, and to an intensive treatment of interplanting two species that differed in successional status (early successional Populus deltoides Bartram ex Marsh. ssp. deltoides, with the mid-successional Q. nuttallii). Native recolonization varied in effectiveness by block but overall provided few woody plants. All active restoration methods (planting and direct seeding) were successful in terms of stocking. Populus grew larger than Quercus, reaching canopy closure after 2 years and heights after 2 and 5 years of 6 and 12.7 m, respectively. Planted Quercus were significantly larger than direct seeded Quercus in all years, but only averaged 1.4 m in height after 5 years. Interplanting did not seem to facilitate development of the Quercus seedlings. The early success of the interplanting technique demonstrated that environmental benefits can be obtained quickly by more intensive efforts. Native recolonization can augment active interventions if limitations to dispersal distance are recognized. These results should provide landowners and managers with the confidence to use techniques of varying intensity to restore ecosystem functions.     

城市生态风景林——中山陵景区异龄复层景观林抑菌功能研究

对中山陵景区异龄复层混交景观林抑菌功能研究结果表明,供试复层林群落均有较好的抑菌效果.与对照相比,上午9:30～10:00空气中细菌菌落数(简称含菌量)减少1 428～9 331 cfu/m3.生长期内4～9月,抑菌率达52.37%～95.62%,抑菌效果以秃杉 松阔、阔瓣含笑 杂阔、乳源木莲 杂阔、香樟 杂阔、香樟 松阔、深山含笑 杂阔、乐昌含笑 杂阔群落较好.苦槠 杂阔、青冈 杂阔群落也有一定的抑菌功能.而桂花 松树(马尾松)、桂花 杂阔等群落抑菌功能则较低.抗菌活性测定结果表明,阔瓣含笑、乳源木莲、深山含笑、乐昌含笑、香樟,以及金叶含笑叶挥发油对空气中革兰氏阳性细菌--金黄色葡萄球菌有较强抗菌活性.同时对供试群落抑菌功能的日变化、季节变化也作了测定分析.     

Individual-tree diameter growth model for sugar maple trees in uneven-aged northern hardwood stands under selection system

An individual-tree diameter model was developed for sugar maple (Acer saccharum Marsh.) in northern hardwood stands managed under selection system. We fitted long-term remeasurement data to a linear mixed model to account for the temporal autocorrelation of the remeasurements. The model was evaluated using independent data from two physiographic regions and representing a range of tree diameter classes, residual basal areas and years since cut. We compared our model to several individual-tree models based on data from stands with varied management histories. Several competition indices were also tested for an improvement in model fitting and prediction. Our model had lower bias and prediction error when compared to two previous models, as it better accounted for the increased diameter growth that occurred in trees from appropriately managed stands. The addition of a tree-specific competition index failed to improve model fit and predictive ability over stand-level basal area.     

Radiation use efficiency in adjacent hardwood and pine forests in the southern Appalachians

The efficiency with which trees convert photosynthetically active radiation (PAR) to biomass has been shown to be consistent within stands of an individual species, which is useful for estimating biomass production and carbon accumulation. However, radiation use efficiency (?) has rarely been measured in mixed-species forests, and it is unclear how species diversity may affect the consistency of ?, particularly across environmental gradients. We compared aboveground net primary productivity (ANPP), intercepted photosynthetically active solar radiation (IPAR), and radiation use efficiency (? = ANPP/IPAR) between a mixed deciduous forest and a 50-year-old white pine (Pinus strobus L.) plantation in the southern Appalachian Mountains. Average ANPP was similar in the deciduous forest (11.5 Mg ha⁻¹ y⁻¹) and pine plantation (10.2 Mg ha⁻¹ y⁻¹), while ? was significantly greater in the deciduous forest (1.25 g MJ⁻¹) than in the white pine plantation (0.63 g MJ⁻¹). Our results demonstrate that late-secondary hardwood forests can attain similar ANPP as mature P. strobus plantations in the southern Appalachians, despite substantially less annual IPAR and mineral-nitrogen availability, suggesting greater resource-use efficiency and potential for long-term carbon accumulation in biomass. Along a 260 m elevation gradient within each forest there was not significant variation in ?. Radiation use efficiency may be stable for specific forest types across a range of environmental conditions in the southern Appalachian Mountains, and thus useful for generating estimates of ANPP at the scale of individual watersheds.     

Stand development after different thinnings in two uneven-aged Picea abies forests in Sweden

Two field experiments, located in Central and Northern Sweden, were used to study the influence of standing volume on volume increment and ingrowth in uneven-aged Norway spruce (Picea abies (L.) Karst.) stands subjected to different thinnings. Each experiment had a 3 × 2 factorial block design with two replications. Treatments were thinning grade, removing about 45, 65, and 85% of pre-thinning basal area, and thinning type, removing the larger or the smaller trees, respectively. Each site also had two untreated control plots. Plot size was 0.25 ha. Volume increment was 0.5–6.8 m³ ha⁻¹ year⁻¹ for the plots, and significantly positively (p < 0.01) correlated with standing volume. Within treatment pairs, plots thinned from Above had consistently higher volume increment than plots thinned from Below. Ingrowth ranged from 3 to 33 stems ha⁻¹ year⁻¹, with an average of 14 and 21 stems ha⁻¹ year⁻¹ at the northern and southern site, respectively. At the southern site ingrowth was significantly negatively (p < 0.01) correlated with standing volume, but not at the northern site. Mean annual mortality after thinning was 2 and 7 stems ha⁻¹ year⁻¹at the northern and southern site, respectively.     

Trade-offs and synergies between ecosystem services in uneven-aged mountain forests: evidences using Pareto fronts

Uneven-aged mountain forests are considered favourable for the continuous provisioning of multiple ecosystem services (ES). These ES may however exhibit trade-offs or synergies that can be modulated by forest management. Yet, our knowledge remains poor on both the relationships between ES and the way management practices can optimise and reconcile them. In this study, we aimed at (1) characterising trade-offs and synergies between timber production, biodiversity conservation and protection against natural hazards; (2) identifying efficient (i.e. Pareto-optimal) management scenarios for the joint provisioning of these ES; and (3) comparing them to “reference” management scenarios. Using a simulation framework that couples a forest dynamics model, a silviculture algorithm and linker functions relating ES indicators to stand structure, we predicted the response of different ES indicators to various uneven-aged management practices in the Western Alps. With a metamodeling approach and Pareto front techniques, we intensively explored and analysed relationships between ES indicators and found trade-offs between timber production and other ES, but synergies between protection and biodiversity. “Pareto-optimal” management scenarios were characterised by low thinning and harvesting intensities but exhibited gradients of total removals and deadwood and large tree retention along the Pareto front. They greatly differed from our set of production and biodiversity oriented reference scenarios, thus emphasising the strong impact of considering additional ES in scenario optimisation processes. This study highlighted the strengths and weaknesses of Pareto front techniques for both the analysis of trade-offs and synergies between ES and the identification of efficient management practices.