Modeling silviculture after natural disturbance to sustain biodiversity in the longleaf pine (Pinus palustris) ecosystem: balancing complexity and implementation

Modeling silviculture after natural disturbance to maintain biodiversity is a popular concept, yet its application remains elusive. We discuss difficulties inherent to this idea, and suggest approaches to facilitate implementation, using longleaf pine (Pinus palustris) as an example. Natural disturbance regimes are spatially and temporally variable. Variability leads to a range of structural outcomes, or results in different pathways leading to similar structures. In longleaf pine, lightning, hurricanes, surface fires, and windthrow all lead to similar structures, but at different rates. Consequently, a manager can select among various natural disturbance patterns when searching for an appropriate silvicultural model. This facilitates management by providing flexibility to meet a range of objectives. The outcomes of natural disturbances are inherently different from those of silviculture, for example, harvesting always removes boles. It is instructive to think of silvicultural disturbances along a gradient in structural outcomes, reflecting degree of disparity with natural disturbance. In longleaf pine this might involve managing for two-cohort structure, instead of multi-cohort structure characteristic of old growth stands. While two-cohort structure is a simplification over the old growth condition, it is an improvement over single-cohort management. Reducing structural disparity between managed and unmanaged forests is key to sustaining biodiversity because of linkages that exist between structural elements, forest biota, and ecosystem processes. Finally, interactions of frequency, severity, intensity, seasonality, and spatial pattern define a disturbance regime. These components may not have equal weight in affecting biodiversity. Some are easier to emulate with silviculture than are others. For instance, ecologists consider growing-season fire more reflective of the natural fire regime in longleaf pine and critical for maintenance of biodiversity. However, dormant season fire is easier to use and recent work with native plants suggests that seasonality of fire may be less critical to maintenance of species richness, as one component of biodiversity, than is generally believed. Science can advance the goal of modeling silviculture after natural disturbances by better illustrating cause and effect relationships among components of disturbance regimes and the structure and function of ecosystems. Wide application requires approaches that are adaptable to different operational situations and landowner objectives. A key point for managers to remember is that strict adherence to a silvicultural regime that closely parallels a natural disturbance regime may not always be necessary to maintain biodiversity. We outline examples of silvicultural systems for longleaf pine that demonstrates these ideas.     

Disturbances and structural development of natural forest ecosystems with silvicultural implications,using Douglas-fir forests as an example

Forest managers need a comprehensive scientific understanding of natural stand development processes when designing silvicultural systems that integrate ecological and economic objectives, including a better appreciation of the nature of disturbance regimes and the biological legacies, such as live trees, snags, and logs, that they leave behind. Most conceptual forest development models do not incorporate current knowledge of the: (1) complexity of structures (including spatial patterns) and developmental processes; (2) duration of development in long-lived forests; (3) complex spatial patterns of stands that develop in later stages of seres; and particularly (4) the role of disturbances in creating structural legacies that become key elements of the post-disturbance stands. We elaborate on existing models for stand structural development using natural stand development of the Douglas-fir—western hemlock sere in the Pacific Northwest as our primary example; most of the principles are broadly applicable while some processes (e.g. role of epicormic branches) are related to specific species. We discuss the use of principles from disturbance ecology and natural stand development to create silvicultural approaches that are more aligned with natural processes. Such approaches provide for a greater abundance of standing dead and down wood and large old trees, perhaps reducing short-term commercial productivity but ultimately enhancing wildlife habitat, biodiversity, and ecosystem function, including soil protection and nutrient retention.     

Stand structure of hemiboreal old-growth forests: Characteristic features,variation among site types,and a comparison with FSC-certified mature stands in Estonia

To improve the silvicultural targets for ecologically sustainable forestry, we quantified functionally important structural features for the first time in a representative set of old-growth forests in hemiboreal Europe. Altogether, 23 old-growth stands of four site-type groups were compared with mature commercial stands nearby in the Estonian state forests that hold the Forest Stewardship Council (FSC) certificate of sustainable forestry. These two treatments did not differ significantly in terms of tree-species diversity, volumes of woody debris of <20 cm diameter (including fine woody debris) and its decay-stage composition. However, mature stands had many more early-successional trees and lacked late-successional deciduous species; they also had a higher overall density and volume of live trees, due to abundant individuals of 10–39 cm diameter at breast height. Old-growth stands had at least twice as many live trees ≥40 cm, standing dead trees ≥30 cm and lying wood ≥20 cm in diameter, any freshly fallen debris, and regeneration. For lying wood ≥20 cm in diameter, the treatment effect depended on site type: both treatments of Vaccinium-type dry boreal forests were remarkably deadwood-poor (indicating historical management of the old-growth stands), while mature eutrophic stands of Aegopodium-type were most impoverished relative to old-growth levels. We conclude that many functional characteristics of old growth were present in the FSC-certified, mostly naturally regenerated, commercial stands. The main problem is the lack of very large trees, particularly of late-successional deciduous species, which should be addressed by their well-planned retention in cut areas and reconsideration of salvage logging strategies. A dense regeneration in old-growth stands also indicated the potential of selection cuttings. The study highlighted the need for region- and site-type specific numerical targets for sustainable forest management, which in the hemiboreal region should address the characteristic occurrence of late-successional deciduous trees on fertile soils and higher natural deadwood volumes than in typical boreal forests. For certification, the issues of structural impoverishment revealed both the inadequacy of some silvicultural practices and some indicators set by the national FSC-standard in Estonia.     

Emulating natural disturbances: the role of silviculture in creating even-aged and complex structures in the black spruce boreal forest of eastern North America

Ecosystem-based forest management is based on the principle of emulating regional natural disturbance regimes with forest management. An interesting area for a case study of the potential of ecosystem-based forest management is the boreal forest of north-western Québec and north-eastern Ontario, where the disturbance regime creates a mosaic of stands with both complex and simple structures. Old-growth stands of this region have multi-storied, open structures, thick soil organic layers, and are unproductive, while young post-fire stands established following severe fires that consumed most of the organic soil show dense and even-sized/aged structures and are more productive. Current forest management emulates the effects of low severity fires, which only partially consume the organic layers, and could lead to unproductive even-aged stands. The natural disturbance and forest management regimes differ in such a way that both young productive and old-growth forests could ultimately be under-represented on the landscape under a fully regulated forest management regime. Two major challenges for ecosystem-based forest management of this region are thus to: (1) maintain complex structures associated with old-growth forests, and (2) promote the establishment of productive post-harvest stands, while at the same time maintaining harvested volume. We discuss different silvicultural approaches that offer solutions to these challenges, namely the use of (1) partial harvesting to create or maintain complex structures typical of old-growth stands, and (2) site preparation techniques to emulate severe soil burns and create productive post-harvest stands. A similar approach could be applied to any region where the natural disturbance regime creates a landscape where both even-aged stands established after stand-replacing disturbances and irregular old-growth stands created by smaller scale disturbances are significant.     

A simulation of the development and restoration of old-growth structural features in northern hardwoods

Thinning treatments in second-growth forest may be a practical means of accelerating the development of certain old-growth structural features in regions where old stands are presently uncommon. We used CANOPY, an individual-tree model calibrated with data from thinned and unthinned stands, to simulate effects of thinning on growth rates and development of old-growth structural features in second-growth northern hardwoods. Three simulated, moderately heavy thinnings over a period of 45 years nearly doubled the predicted mean radial increment of canopy trees, percent of stand basal area in large trees, and area of canopy gaps. Compared to untreated stands, thinned stands had fewer dead trees per ha, but the dead trees were larger in size and the overall volume of snags and logs was little affected. In a 77-year old even-aged stand, moderately heavy thinning was predicted to reduce the time needed to attain the minimum structural features of an old-growth forest from 79 to 36 years. Simulated treatments in an older, uneven-aged stand gave mixed results; the moderately heavy treatment stimulated individual tree growth, but the removal of some medium-sized canopy trees in conjunction with natural mortality delayed the development of old-growth structure. Total volume of dead wood may still be deficient under the thinning regimes investigated in this study, but predicted live-tree structure 45 years after moderately heavy thinning was typical of stands in the advanced transition and steady-state stages of old-growth development. Results suggest that thinning can substantially accelerate the development of old-growth structure in pole and mature northern hardwoods, but response in older, uneven-aged stands is more modest, and treatments in these stands may need to be more conservative to achieve restoration goals.     

Long-term influence of fire and harvesting on boreal forest age structure and forest composition in eastern Québec

In boreal forests, historical variations in the area disturbed by natural disturbances or harvesting have rarely been compared. We measured temporal and spatial variations in areas affected by severe fires and clearcutting throughout the 20th century in a 57, 332 km² section of the eastern Canadian boreal forest. We examined the effects of these disturbances on spatio-temporal variations in the abundance of forests >60 years. Natural variability for the abundance of forests >60 years was estimated from simulations of natural disturbance regimes. We also measured compositional and structural differences between three categories of stands originating from relatively recent disturbances (∼50 years; clearcutting, fires, and clearcutting followed by fires), and one category of stands that were undisturbed for at least 200 years. At the regional level, we observed that forests >60 years gradually became scarcer throughout the 20th century due to a gradual expansion of harvested areas, an effect most pronounced in the southern part of the region, where mature and old forest abundance was clearly outside the range of natural variability at the end of the studied period. At the stand level, forest composition and structure differed between stand-origin categories: clearcutting-origin stands contained more balsam fir (Abies balsamea), fire-origin stands more black spruce (Picea mariana), and fire/clearcutting-origin stands more hardwoods (Betula papyrifera and Populus tremuloides). Overall, we estimate that strict forest management targets based on natural disturbance regimes will be difficult to achieve in eastern North-American boreal forests, most notably because contemporary disturbance rates, including both clearcutting and fire, have gradually become higher than the fire rates observed during the preindustrial period.     

匈牙利刺槐((Robinia pseudoacacia L.)林的经营研究(英文)

匈牙利刺槐((RobiniapseudoacaciaL.)是在17世纪初从北美引入到欧洲的第一个森林树种。在匈牙利,刺槐是非常重要的速生树种,为经济和生态目的,可以成功营造刺槐人工林。结合该树种的生长特点选择营林措施,可以最大限度的提高刺槐人工林的成活率和生产力。本文根据林分结构和森林产量长期实验林的研究成果,提出了刺槐林的抚育作业次序。制定好的营林计划和模式将会培育出效益刺槐林,并能使土地经营者更好地接受该树种。同时,刺槐也是一个非常有用的能源生产树种,本文展示了对这方面的研究成果。图2表1参8。     

Response of old-growth conifers to reduction in stand density in western Oregon forests

The positive growth response of healthy young trees to density reduction is well known. In contrast, large old trees are usually thought to be intrinsically limited in their ability to respond to increased growing space; therefore, density reduction is seldom used in stands of old-growth trees. We tested the null hypothesis that old-growth trees are incapable of responding with increased growth following density reduction. The diameter growth response of 271 Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), ponderosa pine (Pinus ponderosa Dougl. ex Laws) and sugar pine (Pinus lambertiana Dougl.) trees ranging in age from 158 to 650 years was examined 20 to 50 years after density reduction. Density reduction involved either light thinning with removal of less vigorous trees, or shelterwood treatments in which overstory trees were not removed. Ratios of basal area growth after treatment to basal area growth before treatment, and several other measures of growth, all indicated that the old trees sometimes benefited and were not harmed by density reduction. Growth increased by 10% or more for 68% of the trees in treated stands, and nearly 30% of trees increased growth by over 50%. This growth response persisted for at least 20 years. During this 20-year period, only three trees in treated stands (1.5%) exhibited a rapid decrease in growth, whereas growth decreased in 64% of trees in untreated stands. The length of time before a growth response to density reduction occurred varied from 5 to 25 years, with the greatest growth response often occurring 20 to 25 years after treatment. These results have important implications both for the basic biology of aging in woody plants as well as for silvicultural practices in forests with old-growth trees.     

Trade-offs between seedling growth,thinning and stand stability in Sitka spruce stands: a modelling analysis

The forest industry is increasingly adopting alternative silvicultural systems, involving regeneration beneath an existing forest canopy, rather than clear-felling and replanting. To apply these silvicultural systems in windy regions such as Britain and Ireland, it is essential that the interactions between thinning intensity, stand stability and seedling growth are properly understood. Here, we present a modelling analysis of the three key relationships between: (i) stand density and the proportion of incident radiation transmitted through a forest canopy as a stand is thinned; (ii) transmitted radiation and seedling growth, and (iii) stand density and stand stability. These relationships were examined using separate models of radiative transfer (MAESTRO), seedling growth, and stand stability/wind risk (ForestGALES). Output from the three models was synthesised to calculate whether a given stand thinned to a pre-defined stability limit would allow sufficient light to penetrate the canopy for seedling growth. A minimum transmittance of 20% was identified as a requirement for seedling growth, which corresponds to removing 45% of stand basal area. A thinning of this intensity left some stands susceptible to unacceptable wind damage, especially in old or previously thinned stands on soils where rooting is impeded. The results emphasised the fact that rooting conditions, thinning history and age of intervention are major constraints on the silvicultural options. In general, older stands are not suitable for conversion to continuous cover forestry (CCF) systems, and the transformation process should begin at pole stage, when heavy thinning does not leave the stand unstable. The analysis approach used here illustrates the potential for combining models to address complex forest management issues.     

Changes in biodiversity indicators in managed and unmanaged forests in NE Spain

Major changes in Mediterranean forests have occurred in recent decades, mainly as a result of the abandonment of traditional activities and population decline in rural areas. In this study, we analyzed the short-term (11-year) evolution of forests in the region of Catalonia (NE Spain) and the role of management, by comparing seven biodiversity indicators estimated from 7,664 plots from the Second and Third Spanish National Forest Inventory. We evaluated the changes in unmanaged and managed stands with different silvicultural treatments, and considered the effect of stand density and land ownership on these dynamics. We found a general naturalization and maturation of forests and an increase in all of the biodiversity indicators investigated during the study period, with the increments being greater in unmanaged than in managed plots. Some types of silvicultural treatments, such as selection cutting or thinning, were shown to be compatible with an increase in the analyzed indicators, and thus were more adequate for a multifunctional management that considers forest production together with the maintenance or improvement of the diversity of forest communities. The increases in shrub species richness and in the number of large-diameter trees after silvicultural treatments were more prominent in dense stands. Private lands presented greater short-term increases than public forests in all biodiversity indicators, except for large-diameter trees. From these results, we concluded that the application of silvicultural treatments can be a key tool to shape and maintain diverse and healthy forest structures in the context of socioeconomic and environmental changes in the Mediterranean region, which may induce potentially excessive densification and homogenization of some forest stands and landscapes.     

Influence of fire intensity on structure and composition of jack pine stands in the boreal forest of Quebec: Live trees,understory vegetation and dead wood dynamics

North American jack pine (Pinus banksiana Lamb.) stands are generally characterized by an even-aged structure resulting from high intensity fires (HIF). However, non-lethal fires of moderate intensity (MIF), which leave behind surviving trees, have also been reported. The objectives of this study were two-fold: (1) assess the concurrent dynamics of live trees, understory vegetation and different types of coarse woody debris (CWD) during succession after HIF; and (2) document how MIF affects stand structure component dynamics compared to HIF. Stands affected by both HIF and MIF were selected. Tree characteristics and age structure, understory biomass, and CWD volume were assessed. Our results suggest that the structural succession of jack pine stands following HIF comprises three stages: young stands (<48 years), premature and mature stands (58–100 years) and old stands (>118 years). Canopy openness and jack pine density significantly decreased with time since HIF, while black spruce density and CWD volume significantly increased. The highest structural diversity was measured in the premature and mature stands. Compared to HIF, MIF increased mean jack pine basal area, decreased average stand density, delayed the replacement of jack pine by black spruce replacement in the canopy, decreased CWD volume, and significantly increased bryophytes mass. MIF increased the diversity of live trees and generally decreased CWD structural diversity. The study confirms the diversity of natural disturbance magnitude and successional processes thereby initiated. Thereafter, it appeared to be relevant for adjustment of disturbance emulating forest-management systems.     

Mitigating fire risk to late-successional forest reserves on the east slope of the Washington Cascade Range, USA

A fire-risk model was developed using a stand-structure approach for the forests of the eastern slopes of the Washington Cascade Range, USA. The model was used to evaluate effects of seven landscape-scale silvicultural regimes on fire risk at two spatial scales: (1) the risk to the entire landscape; and (2) the risk to three reserve stands with stand structures associated with high conservation priorities (layered canopy, large trees, multiple species). A 1000 ha landscape was projected five decades for each management regime using an individual tree, distance-independent growth model. Results suggest that a variety of silvicultural approaches will reduce landscape fire risk; however, reserve stand fire risk is minimally decreased by thinning treatments to neighboring stands. Intensive fuel reduction through prescribed burning and selection of reserve stands in favorable topographic positions provide substantial fire risk reductions.     

Abundance and attributes of wildlife trees and coarse woody debris at three silvicultural systems study areas in the Interior Cedar-Hemlock Zone,British Columbia

Unmanaged cedar (Thuja plicata)-hemlock (Tsuga heterophylla) forests of the northern Interior Wetbelt of British Columbia support standing and dead trees with a variety of structural features that provide habitat for wildlife. We describe the pre-harvest abundance and characteristics of wildlife trees (standing trees with special characteristics that provide habitat for wildlife) and coarse woody debris (CWD) at three silvicultural systems trials in cedar-dominated stands, and the short-term effects of forest harvesting on the abundance and attributes of CWD. The treatments were clearcut, group retention (70% volume removal), group selection (30% volume removal), and unlogged control. We measured standing trees in 75 0.125-ha plots and CWD along 225 24-m transects, using a functional classification system to characterize habitat attributes of trees and logs. CWD assessments were repeated on the same transects after the harvest. The relationship between tree size and occurrence of habitat features was strong for both standing trees and logs. Each of the four major tree species in the study area was associated with specific habitat features that occurred more often in that species than in any other. Large concealed spaces at the bases of trees, providing den sites and escape cover, were associated with hybrid white spruce (Picea engelmannii × glauca). We suggest that these trees had originated on nurse logs that subsequently rotted away; if that supposition is correct, there may be shortages of these structures in future stands that originate from plantations. Forest harvesting had little effect on the volume of CWD, but did affect the decay class distribution, reduce the proportion of pieces having structural habitat attributes, and reduce piece lengths; these effects were generally proportional to the level of harvest removal. Partial-cut silvicultural systems have the potential to mitigate anticipated deficits in large wildlife trees and logs in managed stands, if components of the stand are managed on longer rotations than those planned for timber production alone.     

The increasing scarcity of red oaks in Mississippi River floodplain forests: Influence of the residual overstory

Red oaks – cherrybark oak (Quercus pagoda Raf.), willow oak (Quercus phellos L.), water oak (Quercus nigra L.), and Nuttall oak (Quercus texana Buckley; aka: Quercus nuttallii Palmer) – are not regrowing in Mississippi Delta river floodplain forests in the southeastern United States in sufficient numbers to sustain the former species composition and timber and wildlife values. Even if vigorous red oak reproduction becomes established, partial harvesting that does not remove the taller trees will suppress understory red oak height growth more than it will suppress height growth of such other species as sugarberry (Celtis laevigata Willd.), American elm (Ulmus americana L.), cedar elm (Ulmus crassifolia Nutt.), swamp dogwood (Cornus foemina Mill.), green ash (Fraxinus pennsylvanica Marshall), and sweetgum (Liquidambar styraciflua L.). Consequently, the red oaks in these partially harvested stands become increasingly suppressed and probably die; and there is a shift in species composition to the other species. In addition to ensuring vigorous oak reproduction, silvicultural clearcutting or rapid removal of the residual trees following shelterwood or seed tree harvesting to provide full sunlight is needed to ensure red oaks become a dominant part of these future river floodplain stands.     

Silviculture for old-growth attributes

Silviculture to maintain old-growth forest attributes appears to be an oxymoron since the late developmental phases of forest dynamics, described by the term old-growth, represent forests that have not experienced human intervention or timber removal for a long time. In the past, silvicultural systems applied to old-growth aimed to convert it into simplified, more productive regrowth forests substantially different in structure and composition. Now it is recognised that the maintenance of biodiversity associated with structural and functional complexity of late forest development successional stages cannot rely solely on old-growth forests in reserves. Therefore, in managed forests, silvicultural systems able to develop or maintain old-growth forest attributes are being sought. The degree to which old-growth attributes are maintained or developed is called “old-growthness”. In this paper, we discuss silvicultural approaches that promote or maintain structural attributes of old-growth forests at the forest stand level in (a) current old-growth forests managed for timber production to retain structural elements, (b) current old-growth forests requiring regular, minor disturbances to maintain their structure, and (c) regrowth and secondary forests to restore old-growth structural attributes. While the functions of different elements of forest structure, such as coarse woody debris, large veteran trees, etc., have been described in principle, our knowledge about the quantity and distribution, in time and space, of these elements required to meet certain management objectives is rather limited for most ecosystems. The risks and operational constraints associated with managing for structural attributes create further complexity, which cannot be addressed adequately through the use of traditional silvicultural approaches. Silvicultural systems used in the retention and restoration of old-growthness can, and need, to employ a variety of approaches for managing spatial and temporal structural complexity. We present examples of silvicultural options that have been applied in creative experiments and forestry practice over the last two decades. However, these largely comprise only short-term responses, which are often accompanied by increased risks and disturbance. Much research and monitoring is required still to develop and optimise new silvicultural systems for old-growthness for a wide variety of forest ecosystem types.     

Management of pine wilt disease in Korea through preventative silvicultural control

Pine wilt disease (PWD) represents a major threat to forest ecosystems worldwide. Although PWD is now better understood, effective control measures for this disease have still not been devised. Here, we report several years of field studies on preventative silvicultural control of PWD. Silvicultural control through preventative clear-cutting and the manual removal of logs was implemented between 2005 and 2009 in 16 Korean districts that had newly PWD-infected stands. Preventative clear-cutting of neighboring asymptomatic pine trees (within a 10-50-m radius of wilt trees) and the removal of felled logs or branches suppressed spread of PWD. Occurrences of PWD wilt pines in districts (city or county) subjected to this silvicultural control method were significantly reduced compared with those in districts using conventional controls (physical or chemical treatment of wilt pine trees). Through silvicultural control, PWD was successfully suppressed in 11 of 16 districts investigated. In contrast, successful control was achieved in only 1 among 18 districts subjected to conventional control. Our results will be of considerable interest to those engaged in the very difficult battle against the global spread of PWD.     

Does reverse growth dominance develop in old plantations of Eucalyptus saligna?

Patterns of stand growth and dominance among individual trees change through stand development. We tested a prediction that large, old plantations of Eucalyptus saligna (Sm.) in Hawaii and Brazil would show a pattern of “reverse” growth dominance, with the largest trees contributing more to stand biomass than to current stand increment. This pattern might develop if the largest trees accounted for a large portion of the total resource use of the stand, but were less efficient at utilizing resources to produce stemwood. The 70-year-old plantation in Hawaii had a stem mass of 610 Mg/ha, compared with 325 Mg/ha in the 66-year-old Brazil plantation. Cumulative frequency plots for both sites showed that dominant trees comprised a very large proportion of total stand mass; the largest 20% of the trees accounted for 50% and 30% of the total stand mass in Hawaii and Brazil, respectively. Contrary to expectations, the largest trees continued to produce a disproportionately large amount of total stand growth, with the largest 20% of trees accounting for 60% (Hawaii) and 40% (Brazil) of stand growth. The frequency distributions resulted in positive growth dominance coefficients (similar to Gini coefficients) of 0.14 for Hawaii and 0.09 for Brazil, rather than negative values that would indicate that reverse growth dominance. The failure of these monoculture Eucalyptus stands to develop reverse growth dominance contrasts starkly with a variety of studies with pine species, which tend to show neutral-to-reverse growth dominance. Indeed, continued dominance of large trees suggests the trees might respond well to silvicultural treatments such as thinning or fertilization. Future work that contrasts patterns of growth dominance among species will be important as a foundation for developing generalizations about trends in growth dominance with stand development.     

Evaluation of growth response,stand value and financial return for pre-commercially thinned jack pine stands in Northwestern Ontario

This study examined the impact of pre-commercial thinning (PCT) on tree growth, product recovery, stand value and financial return in jack pine stands in Northwestern Ontario. Ten sites composed of both control and PCT stands representing various stand densities (2000–6000 trees/ha) and stand ages (26–36 years old) were selected for this study. Three thousand and eighty-two trees were measured for DBH and total height, and were reconstructed in 3-D using a taper equation for jack pine. The reconstructed virtual trees were then “sawn” using the software package Optitek to obtain optimal lumber value recovery, which was then used to determine total product value per tree and financial return. The quadratic mean DBHs of trees from the PCT stands were significantly larger than those from the control stands for all 10 sites. Six of ten PCT stands had significantly taller trees than did the controls of the same sites. With increasing stand density, tree DBH decreased in the control stands while no consistent pattern could be recognized for the DBH of the PCT stands. The increment in average DBH due to PCT increased with increasing thinning intensity. PCT reduced total tree volume per hectare, benefited merchantable stem volume per hectare, and improved the total lumber volume and value recovery per hectare. On average, the PCT stands produced approximately $2760 and $1770/ha (or 19.6 and 16.1%) more product value per hectare for the dimension mill and stud mill, respectively. PCT also significantly reduced logging and lumber conversion costs. Higher total product values and lower total costs resulted in higher benefit/cost (B/C) ratios in the PCT stands than did in the control stands. The increased financial return due to PCT is associated with the magnitude of difference in quadratic mean DBH resulting from PCT. The B/C ratio difference between control and PCT stands increased with increasing thinning intensity. Overall, this study indicates that PCT appears to be an economically viable silvicultural investment for jack pine stands in Northwestern Ontario.