Silvicultural Alternatives Research Articles

Post-harvest nitrogen cycling in clearcut and alternative silvicultural systems in a montane forest in coastal British Columbia

The MASS (Montane Alternative Silvicultural Systems) trial was established in the coastal mountains of British Columbia to compare clearcut, patch cut, green tree and shelterwood systems. A number of studies were carried out at the MASS trial to determine the extent to which these variable levels of stand retention retained old-growth attributes of N cycling and associated ecological processes. Harvesting led to increases in N mineralization in the forest floor (2×) and mineral soil (10×), and fluxes of N through the upper 25 cm of mineral soil (2× to 3×). However, fluxes of N were not large (< 0.35 kg ha-1per growing season). Nitrogen mineralized was predominantly ammonium and not nitrate in the forest floor (> 95% in all but clearcut, > 75% in clearcut) and upper mineral soil horizon (42–86%). The nitrate component came from heterotrophic decomposition of organic matter, not conversion of ammonium to nitrate by autotrophs, and nitrate increases resulted from decreased gross nitrate consumption with harvesting, rather than increased nitrate production. The increases in soil N availability resulting from harvesting were reflected in only slight increases in seedling foliar N concentrations for two to four years after logging (peak of ~ 2% for western hemlock and ~ 1.6% for amabilis fir) before decreasing to below deficiency thresholds for both species. Overall, estimated losses of N from the rooting zone after harvesting (1 kg ha-1 yr-1) were minimal in comparison to estimated N inputs (4 kg ha-1 yr-1), N exports in logs at harvesting (250 kg ha-1) and soil reserves (11 400 kg ha-1). Although unlikely to affect future site productivity, losses of N could be reduced somewhat through the use of shelterwood harvesting. Key words: alternative silvicultural systems, variable retention harvesting, nitrogen cycling, litterfall, decomposition, nitrification, N mineralization, microbial ecology, leaching, foliar N, Abies amabilis, Tsuga heterophylla, Thuja plicata

Temporal variations and distribution of carbon stocks in aboveground biomass of radiata pine and maritime pine pure stands under different silvicultural alternatives

In recent years there has been considerable interest in evaluating carbon budgets in forests because of the importance of these ecosystems as carbon sources and sinks. Quantifying forest net primary production (NPP) is critical to understanding the global carbon cycle because forests are responsible for a large portion of the total terrestrial NPP. The present study provides information about the temporal and spatial dynamics of carbon (C) stored in aboveground tree biomass in even-aged, pure stands of maritime pine and radiata pine managed under different silvicultural regimes in northwest Spain. Carbon budgets (storage calculations) for tree biomass provide useful information for characterizing forests as important C sinks and allow assessment of the potential effects of harvesting and logging residue management on forest C status. Stand dynamic growth models were used to estimate the amount of C accumulated in the remaining stand and the amount removed in thinning treatments throughout the whole rotation. For radiata pine, carbon sequestration in total aboveground tree biomass at stand level in the whole rotation (thinnings and clear-cutting at 30 years) ranged from 3.4 Mg ha −1 per year (the lowest initial stocking density, the worst site quality and 35% of thinning intensity) to 5.9 Mg ha −1 per year (the highest initial stocking density, the best site quality and 15% of thinning intensity). For maritime pine, the amount of tree biomass at stand level was significantly lower than in radiata pine stands, and mean annual carbon storage ranged from 2.3 to 4.6 Mg ha −1 per year for the same rotation length. The total aboveground and stem wood biomass C pools in these stands can be increased by increasing the rotation age and site quality and decreasing thinning intensity. Selection of the best site qualities, reduction of the thinning intensity and perhaps extension of the rotation length are therefore possible strategies for sustainable management of pine stands in Spain when the main objective is biomass production and C sequestration.

Modelling silvicultural and economic alternatives for Scots pine (Pinus sylvestris L.) plantations in north-western Spain

Summary Two silvicultural alternatives for Scots pine ( Pinus sylvestris L.) plantations in north-western Spain were simulated and compared. One corresponded to the current management practice applied in the region and the other was an intensive silvicultural regime. Both alternatives were described by a specifi c combination of plantation density, precommercial treatments, thinning pattern and rotation age. Stand development of each silvicultural alternative was generated using a regional growth and yield model implemented in a simulator called GesMO, for three site qualities that represented poorest, intermediate and best sites found in the region. Different timber grades associated with each alternative were predicted, and estimates of costs and selling prices were used to predict a cash fl ow pattern for each of the simulated alternatives. The alternatives were ranked using the criterion of net present value of an infi nite series of rotations. Sensitivity analysis, in terms of basic prices, discount rate and rotation length, was also carried out. In addition, the effects of risk of fi re on net revenues were evaluated. For the present regional market conditions the results showed that the currently applied alternative is not the best one if the main aim is profi t maximization. For very poor quality sites the proposed schedules are uneconomical for all silvicultural alternatives.

Growth limitations of planted conifers regenerating under Montane Alternative Silviculture Systems (MASS): Seven-year results

As part of the Montane Alternative Silviculture Systems (MASS) project, this study investigates limits on the growth of montane conifers resulting from varying overstory retention under conventional and alternative silvicultural systems. After harvesting treatments were complete in 1993, Abies amabilis (amabilis fir) and Tsuga heterophylla (western hemlock) seedlings were spring planted in replicated blocks of shelterwood (SW), patch cut (PC), green tree retention (GT) and clearcut (CC) systems. In addition, sub-plots were established within each silvicultural system in which fertilization (at planting) and vegetation control post-planting treatments were applied alone and in combination to test the extent to which growth limitations are related to nutrient availability and vegetative competition. The impact of overstory retention was most pronounced in the reduced light environment of the SW where height growth after seven years was 26-30% lower in both species compared to the untreated CC, GT and PC systems. Although the effect on growth of both species in the SW was mitigated somewhat by fertilization and vegetation control treatments, amabilis fir did not attain free-to-grow height (1.3 m) regardless of post-planting treatment. Time to free-to-grow height in the more open silvicultural systems was reduced in both fir and hemlock with fertilization and vegetation control alone and in combination, except in the CC where the initial growth response to fertilization alone was diminished by the end of the seven-year study. In contrast to fertilization, the effects of vegetation control on height growth were not apparent until three to five years and seven years after planting in the CC and GT, PC, SW, respectively. Combining vegetation control and fertilization had an additive effect on growth in amabilis fir but not in western hemlock. The effect of silvicultural systems and post-planting treatments on the two species illustrate that both above- and below-ground resource availability (light and nutrients) availability was potentially limiting to growth, particularly in the shelterwood treatment. Key words: MASS, silviculture systems, regeneration, Tsuga heterophylla, Abies amabilis, shelterwood, patch cut, green tree reten-tion, clearcut, fertilizer, vegetation control

Evaluation of new silvicultural alternatives for Scots pine stands in northern Spain

Les nouveaux objectifs que la societe demande aux systemes forestiers provoquent actuellement de profonds changements dans la gestion de ces derniers. Des aspects tels que la conservation de la biodiversite ou la jouissance recreative requierent des modeles de gestion forestiere non fondes sur la gestion traditionnelle qui est axee sur la maximisation de la production du bois. Ce travail presente cinq alternatives sylvicoles du sylviculture traditionel, qui se caracterisent, dans 4 cas, par la combinaison d'une gestion plus intensive avec la retention d'une partie du peuplement dans la coupe finale et, dans le dernier cas, par l'extension de la rotation afin d'atteindre ces nouveaux objectifs. Les resultats pour un peuplement de Pinus sylvestris L. dans le nord de l'Espagne ont ete evalues en termes de production (volume total, volume de contreplaque) ainsi qu'en termes financiers (Valeur Potentielle du Sol, VPS), et certaines des alternatives ont montre leur viabilite par comparaison avec la gestion traditionnelle.

Growth Responses of Abies amabilis Advance Regeneration to Overstory Removal, Nitrogen Fertilization and Release From Vaccinium Competition

Abstract Abies amabilis advance regeneration may take several years to acclimate to overstory removal, and poor performance has been attributed to unfavorable microclimate, nutrient stress, and competition from ericaceous vegetation. Our objective was to examine potential factors limiting growth of advance regeneration of Abies amabilis on a montane site in coastal British Columbia. In 1996, 72 experimental plots were established at the Montane Alternative Silvicultural Systems site, Vancouver Island, to provide a design with 12 plots within each of 2 replicate blocks of 3 overstory removal treatments [clearcut (CC), shelterwood (SW), green tree retention (GT)]. Two plots within each replicate block were randomly allocated to each level of 3 nitrogen (N) treatments (0, 100, 250 kg ha-1, applied as urea) × 2 Vaccinium treatments (shoots present or removed).The three overstory removal treatments differed in the amount of solar radiation received beneath the canopy, in the order CC > GT > SW. Three to five growing seasons after treatment, advance regeneration in the GT and CC treatments exposed to >70% incoming solar radiation had the greatest height, stem diameter, and dry weight. N content, new N uptake (inferred from uptake of applied 15N), and allocation of uptake to new shoots were greatest in the CC followed by the GT and SW treatments. N fertilization had no effect on seedling growth. Removal of Vaccinium shoots increased stem diameter of advance regeneration, and increased new shoot dry weight in the GT treatment. Allocation of N to new shoots was greatest in advance regeneration from plots where Vaccinium was removed.

Above-ground biomass predicts growth limitation in amabilis fir and western hemlock seedlings

Conifer regeneration on clearcut montane sites is frequently affected by post-planting growth stagnation. The ability to predict such stagnation would be a valuable asset to forest managers. In this study, we tested the usefulness of above-ground biomass and photosynthetic efficiency (as estimated by foliar nitrogen concentration) in diagnosing growth limitations in western hemlock (Tsuga heterophylla) and amabilis fir (Abies amabilis). Seedlings were grown under different silvicultural systems (clearcut, patch cut, green tree retention and shelterwood) and post-planting treatments (fertilization, vegetation removal) at the Montane Alternative Silvicultural Systems (MASS) site on Vancouver Island, BC. Foliar nitrogen was found to be a poor predictor of height and stem volume growth. However, above-ground biomass predicted current height and stem volume (year 3 after planting), as well as future stem volume (year 7 after planting), in both species. Above-ground biomass therefore represents a useful measure of likely future growth performance, and may provide early warning of incipient growth stagnation in these species. Key words: amabilis fir, Abies amabilis, biomass, western hemlock, Tsuga heterophylla, growth limitation, photosynthetic capacity, biomass, seedling growth, regeneration

Growth and diversity effects of silvicultural alternatives on an old-growth forest in Finland

Summary The study compares six silvicultural alternatives on an old-growth Norway spruce-dominated stand. Untreated forest was used as a control treatment. The wide stem distribution range was maintained by single tree and group selection. Shelterwood cuttings (pure Norway spruce, pure Scots pine and in mixtures with broadleaved species) transformed the stand into a two-storied structure, whereas diameter cutting narrowed the stem diameter distribution. Pure pine and pure spruce shelterwood cuttings gave the lowest and untreated the highest stand diversity index value and greatest volume growth. In general, there are several useful silvicultural alternatives to clearcutting in old-growth mixed stands of boreal forests.

Large-scale management experiments in the moist maritime forests of the Pacific Northwest

Several large, integrated forest management experiments have been initiated in the Pacific Northwest this past decade, partially in response to contentious resource management debates. Their goal is to use alternative silviculture treatments to enhance wildlife habitat, biodiversity, or the conservation of aquatic resources in a manner that is socially acceptable. Seven of these large-scale multi-resource silvicultural experiments are examined and evaluated, in light of previous experience with large-scale experiments. All seven employ randomized block designs with replicated treatment units large and practical enough to be commercially operational (most treatment units are 13–20 ha). Because the large-scale context is designed into these experiments, results can be directly interpreted at the scale of management that produced the manipulation, eliminating a change-of-scale bias common in smaller management experiments. The considerable advantages of large, operational treatments are accompanied by their own problems, however. Because of the great expense (∼US$ 10 6/block) and size (50–200 ha) of the experimental blocks, sample size is small ( n<7 blocks) on all but one experiment. This means that statistical power (the probability of correctly rejecting the null hypothesis) will be weak across blocks. With few replicates and high variability both within and among these large-scale treatments, investigators face the possibility that differences might only be detectable at untraditionally high significance levels. A second problem with large-scale experiments is pseudoreplication (lack of independence across replicates), which results in the strength of the experimental evidence being overstated. This is a concern for three of the experiments because their blocks are located in relatively small geographic areas. Meta-analysis (a joint hypothesis test across experiments) is proposed as an effective way to increase sample size—and, therefore, power—while accounting for the different degrees of variation across studies. Looking for commonality, all seven studies are examining the effect of alternative silvicultural on both wildlife habitat and biodiversity. A test of a common hypothesis about ecosystem management would greatly increase not only the power of the test but the return on investment from these rather expensive experiments. In addition to small sample sizes, large variability, and pseudoreplication, other problems common to large-scale experiments are evident. Forest growth experiments are inherently long-term because they are dominated by slow processes with strong transient dynamics. Investigators are faced with institutional and academic demands for short-term results that not only are publishable but also can justify the large investments. The realities of the timber-sale process delayed or eliminated several blocks on at least three of the experiments. Randomization becomes a serious concern for the forest manager, because a clearcut or heavy removal treatment could be assigned to a highly visible location that might be socially unacceptable.

EFFECTS OF GROUP-SELECTION OPENING SIZE ON BREEDING BIRD HABITAT USE IN A BOTTOMLAND FOREST

An increase in timber removals from southern bottomland forests of the United States has been predicted, warranting investigations of the effects of silvicultural alternatives on avian breeding habitat. We studied the effects of creating group-selection openings (man-made canopy gaps) of various sizes on breeding bird habitat use in a bottomland hardwood forest in the Upper Coastal Plain of South Carolina, USA. We used spot mapping and mist netting to estimate bird abundance at 0.06-, 0.13-, 0.26-, and 0.5-ha gaps and at uncut control areas during the 1996, 1997, and 1998 breeding seasons (1 May–1 August). There were significant increases in the number of species mapped (P = 0.0001) and netted (P = 0.0001) with successive increases in gap size. The greatest number of total spot-map detections (P = 0.0002) and mist net captures (P = 0.0004) also occurred in and around the large gaps. These patterns were the result of increased use of larger gaps by field-edge species, primarily Brown-headed Cowbird (Molothrus ater), Common Yellowthroat (Geothlypis trichas), and Indigo Bunting (Passerina cyanea), and some forest-edge species, such as White-eyed Vireo (Vireo griseus) and Northern Parula (Parula americana). Conversely, Acadian Flycatcher (Empidonax virescens) was less abundant in and adjacent to gaps. Because there were few differences in vegetation among gaps of different sizes, it is likely that birds that were detected more frequently in and adjacent to larger gaps selected those gaps based on other factors correlated with size. Creation of 0.5-ha group-selection openings in southern bottomland forests should provide breeding habitat for some field-edge species in gaps and habitat for forest-interior species and canopy-dwelling forest-edge species between gaps, provided that sufficient mature forest is maintained.

Growth limitations for conifer regeneration under alternative silvicultural systems in a coastal montane forest in British Columbia, Canada

In coastal montane British Columbia (BC), Canada, alternative silvicultural systems that retain varying levels of overstorey structure and employ different gap sizes may provide means to promote regeneration of shade-tolerant conifers. In this study, part of an operational trial of Montane Alternative Silvicultural Systems (MASS), foliage morphology and physiology of planted Abies amabilis and Tsuga heterophylla were measured in conjunction with shade, soil and tree water status, and soil temperature to compare above- and below-ground growth limitations under Clearcut (CC), Green Tree (GT), Patch Cut (PC) and Shelterwood (SW) systems. Three years after planting, both A. amabilis and T. heterophylla seedlings in the SW had smaller height increments (mm) than in any of the other treatments. Acclimation of specific leaf area (SLA, cm 2 g −1) indicated that there were above-ground limitations on foliage growth and development in T. heterophylla in the SW. In A. amabilis, despite an increase in photochemical efficiency ( F v/ F m), above-ground growth limitations in the SW were not alleviated. There was no differential acclimation in the maximum light saturated rate of photosynthesis ( A max) or in foliage nitrogen concentrations (%N) in either A. amabilis or T. heterophylla among the silviculture systems. This, combined with the lack of differences in soil water or soil temperature, may indicate that nutrient availability was not different among the silvicultural systems. Foliar morphological and physiological acclimation showed that the source of seedling height growth limitations in the SW system 3 years after planting was above- and not below-ground. Therefore, retention of 25% of the pre-harvest overstorey stand structure in a dispersed pattern can limit the early growth of regenerating montane conifer seedlings presumably as a result of a 47% reduction in available light and not as a result of reduced nutrient availability.

Simulation and comparison of silvicultural alternatives for even-aged Pinus pinaster Ait stands in Galicia (Northwestern Spain)

Trois alternatives de sylviculture pour peuplements purs et reguliers de pin maritime (Pinus pinaster Ait) en Galicie (NO de l'Espagne) sont simulees et comparees. Chaque alternative est formulee comme une combinaison specifique de densite initiale, depressages, regime d'eclaircies et duree de la revolution. Le developpement du peuplement a chaque alternative est simule avec un modele regional de projection de la croissance et production, base sur un des modeles dynamiques de croissance en surface terriere et sur des modeles de distribution des classes de diametres. Pour chaque alternative on a obtenu la production totale de bois par categories de dimension, les couts de gestion, les prix de vente et un bilan economique complet. Les alternatives sont classees en employant le benefice actualise sur une infinite de revolutions identiques et le taux interne de rentabilite. Dans les conditions actuelles, l'alternative la plus intensive est interessante si l'objectif de l'amenagement forestier est la maximalisation du revenu economique direct.

50 years of low thinning in second growth Douglas-fir

This paper presents the Port Blakely XT series, established in western Washington in the period 1948–1958. XT-1, 2 and 3 were designed to evaluate effects of repeated low thinning and extended harvest rotations. XT-7 compares the effects of different levels of removal on standing volume and wood quality.Periodic and mean annual increment trends have been examined for all four trials. Results from these trials indicate the extension of culmination of mean annual increment due to low thinning combined with extended rotations. Volume yield is reported for XT-1 and XT-2. The thinned plots reveal an increase in bole size and an increase in total harvested volume. Wood quality characteristics were measured in XT-1 and 7, evaluated for differences between thinned and non-thinned and compared to stands harvested at younger ages. Results indicate that extended rotations and low thinning increase the quantity of structural log grades when compared to stands harvested on shorter rotations.Such regimes should reduce conflicts between timber production and other values such as watershed, wildlife, and aesthetics and are particularly applicable to public ownership. Key words: growth and yield, mean annual increment, wood quality, alternative silviculture, extended rotations, low thinning

A silvicultural experiment to mitigate pest damage

An optimal impact design experiment was established in 1997 to investigate silvicultural alternatives for reducing vulnerability of white spruce (Picea glauca (Moench) Voss) stands to spruce budworm (Choristoneura fumiferana (Clem.)) damage. Ecosystem and insect population responses are being assessed in stands, thinned using a cut-to-length harvest system that removed 25% or 50% of standing volume in three patterns: uniform shelterwood cuts, standard strip cuts, and strips with "feathered" edges. Clear-cuts and untreated checks support comparisons among the undisturbed state, conventional practice, and thinning regimes. Subplots in the uniform shelterwood cuts and untreated checks were fertilized with 200 kg N/ha in early spring of 1998. The experimental approach permits strong inferences to be made about treatment effects but requires several years to obtain the final results from the research program. Keywords: spruce budworm, thinning, project design

Montane Alternative Silvicultural Systems (MASS): Establishing and managing a multi-disciplinary, multi-partner research site

The Montane Alternative Silvicultural Systems (MASS) study was established on Vancouver Island, B.C. to develop operationally feasible and ecologically sustainable silvicultural systems in old-growth forests. The project addresses regeneration, biodiversity and aesthetic concerns over clearcutting at high elevations. Over twenty integrated studies are examining the biological and economic consequences of shelterwood, small patch clearcut, dispersed green tree retention and clearcut alternatives. Planning and pre-harvest studies began two years before the 1993 harvesting. The Forest Engineering Research Institute of Canada (FERIC) documented the cost and feasibility of harvesting. Post-harvest studies have been underway for five years with funding by the Canada-B.C. Forest Resource Development Agreement (ERDA II), Forest Renewal BC (FRBC), Industry Canada and project cooperators. There are numerous challenges associated with establishing and managing a multi-disciplinary, long-term research site with multiple partners. This paper discusses the administrative aspects of integrated research based on our experience with the MASS project. Key words: research cooperative, silvicultural systems, old-growth forests

BREEDING BIRD RESPONSES TO THREE SILVICULTURAL TREATMENTS IN THE OREGON COAST RANGE

Silvicultural alternatives to clear-cutting have been suggested to promote development, retention, or creation of late-successional features such as large trees, mul- tilayered canopies, snags, and logs. We assessed bird response to three silvicultural alter- natives to clear-cutting that retained structural features found in old Douglas-fir (Pseudo- tsuga menziesii) forests and that imitated natural disturbance regimes more closely than did traditional clear-cutting: (1) small-patch group selection treatment representing a low- intensity disturbance; (2) two-story treatment, representing a moderate to high-intensity disturbance; and (3) modified clear-cut treatment, representing a high-intensity disturbance. We counted diurnal breeding birds 1 yr prior to and 2 yr after harvest to estimate effects of the silvicultural treatments on bird communities compared with uncut controls. The small-patch group selection treatment was most similar in species composition to control stands. The two-story treatment was more similar to the modified clear-cut treatment. Ten bird species remained abundant following the small-patch group selection treatment. They declined in abundance in modified clearcuts and two-story stands. These species included four neotropical migratory species and five species with restricted geographic ranges and habitat associations. Nine species increased in response to moderate and/or high-intensity disturbances. This group included a larger proportion of species that were habitat generalists. Silvicultural treatments imitating low-intensity disturbances were most effective in retaining bird communities associated with mature forest; high-intensity disturbances such as the two-story and modified clear-cut treatments greatly altered bird community composition. Bird responses to the silvicultural treatments that we studied indicate that a variety of stand types is needed to meet needs of all species.

CFIRP: What we learned in the first ten years

In response to public dissatisfaction with forest management methods, we initiated the College of Forestry Integrated Research Project (CFIRP) to test alternative silvicultural systems in Douglas-fir (Pseudotsuga menziesii) stands in western Oregon. We compared costs and biological and human responses among a control and three replicated silvicultural alternatives to clearcutting that retained structural features found in old Douglas-fir forests. Treatments were applied within 8- to 15-ha stands and attempted to mimic crown fires (modified clearcut), windthrow (green tree retention), and small-scale impacts such as root rot diseases (small patch group selection). We also compared costs in three unreplicated treatments (large patch group selection, wedge cut, and strip cut). Each treatment included differences in the pattern of retained dead trees (snags), as either scattered individuals or as clumps. Good communication among researchers and managers, a long-term commitment to the project, and careful documentation of research sites and data are important to the success of long-term silvicultural research projects. To date, over 30 publications have resulted from the project. Key words: alternative silviculture, data management, Douglas-fir, green tree retention, harvesting costs, human dimensions, Oregon, Pseudotsuga menziesii, recreation, wildlife

Uneven-Aged Management in the Pacific Northwest

Abstract Naturally occurring uneven-aged stands are uncommon in the productive Douglas-fir region west of the Cascade crest. Eastside, unmanaged interior forests are multistoried with multiple species but overstocked to the point of instability. Lacking both good natural models and reliable experience with uneven-aged forests, regional silviculturists will need many decades to develop and maintain productive uneven-aged stands. With interest in silvicultural alternatives to even-aged management of Pacific Northwest forests increasing dramatically, better how-to information is badly needed.

Silvicultural alternatives, competition regime and sensitivity to climate in a European beech forest

Growth variability, expressed by ring width sequences, was examined in an even-aged beech ( Fagus sylvatica L.) forest in relation to stand structure, tree competition and climate. A competition-based growth model was developed to simulate stand dynamics and to calculate the yearly growth index series as a ratio between observed and predicted increments. Dendroclimatological analyses were used to evaluate the interactions between intraspecific competition and tree response to climate. For trees living at different competition levels, simple correlation coefficients were calculated between environmental variables (seasonal values of precipitation, temperature, water deficit and surplus) and the growth index series. Results show that beech response to temperature regime and water availability is significantly affected by competition level. When competition is strong, trees are highly sensitivity to water balance; whereas, at a low competition level, trees react positively to high temperatures. Considering that competition may affect tree sensitivity to climate and that thinnings can modify competition regimes it seems possible to influence the climate response of single trees and whole stands through silvicultural treatments and, consequently, to conduct forest management under a hypothesis of climate change. For this purpose, twenty thinning regimes were simulated with a single-tree growth model, varying the treatment intensity and frequency. Four representative regimes were analysed in detail, by examining the predicted yield and the distribution of trees in competition classes, and by evaluating stand sensitivity to climate change.

Alternatives to clearcutting in BC Coastal Montane Forests

The Montane Alternative Silvicultural Systems (MASS) partnership was formed in 1992 to test new approaches to harvesting high-elevation old-growth forests of Vancouver Island, British Columbia. Uniform Shelterwood (SW), Green Tree Retention (GT) and Patch Cuttings (PC) were tested as alternatives to Clearcutting (CC). All systems were compared to an Old Growth (OG) control. Harvesting was completed in 1993. This paper summarizes the conclusions from the operational aspects of the study and reviews some early results from studies of the biological impacts. Harvesting costs to roadside were about 12% greater for the PC and GT and 49% greater for the SW. Cumulative losses to windthrow after three years were 25% in the GT and 5% in the SW. Site disturbance, soil compaction and rates of organic matter decomposition were low across all harvested treatments. Rates of organic matter decomposition and N mineralization on SW, GT and PC were intermediate between CC and OG. Nutrient loss in soil solution was reduced with partial harvesting but lack of available nitrogen is limiting the early growth of coniferous regeneration among all systems. During spring and summer, SW and CC treatments were generally cooler than PC or GT. Damage to understory vegetation and advanced conifer regeneration was least in the SW, which also provided the greatest amounts of seedfall among all harvested treatments. Key words: Abies amabilis, Tsuga heterophylla, Thuja plicata, Chamaecyparis nootkatensis, harvesting costs, site impacts, silvicultural systems, shelterwood