Group-selection Cuts Research Articles

Increasing the intensity of regeneration treatments decreased beta diversity of temperate hardwood forest understory 20 years after disturbance

ContextIn temperate hardwood forests, increased intensity of soil and canopy disturbances tends to increase species richness due to the establishment of numerous early-successional plant species. However, while competitive pioneer species from early stages of succession can become recalcitrant and alter patterns of natural regeneration, very few studies have examined longer-term effects of these treatments on plant biodiversity.AimsIn this study, we investigated mid-term (ca. 20 years) effects of different regeneration treatments with varying soil and canopy disturbance intensities. We compared understory plant communities in temperate hardwood forests from all the South of Quebec (Canada).MethodsUsing circular experimental plots of 1962.5 m2 (radius = 25 m), we measured taxonomic and functional diversity indices and soil properties using four levels of disturbance intensity in six temperate hardwood forests of Quebec distributed along a longitudinal gradient. Reference forests, i.e. control forests with no silvicultural treatment known for ≥ 80 years, were compared to 20-year-old single-tree selection cuts, group-selection cuts and group-selection cuts with soil scarification.ResultsSpecies richness in both group-selection treatments was higher than that in reference forests. Plant equitability and beta diversity among sites in both group-selection treatments were lower than in single-tree selection cuts and control forests. More intense treatments contributed to the mid-term persistence of recalcitrant competitor species (e.g. Rubus idaeus L., Prunus pensylvanica L.f.) whereas soil scarification appears to have negative sustained effects on species known to be sensitive to regeneration treatments (e.g. Monotropa uniflora L., Dryopteris spinulosa Kuhn).ConclusionsIn temperate hardwood forests of Southern Quebec, silvicultural treatments of higher intensities resulted in detrimental effects on soil properties, especially in the surface horizon, 20 years after disturbance. This legacy, in turn, affected the composition and diversity of understory plant communities. The more intense silvicultural treatments contributed to the persistence of pioneer species better adapted to a wider range of environmental conditions and resulted in a decrease in understory plant community heterogeneity among sites. Conversely, single-tree selection cutting appeared to be the most appropriate silvicultural treatment for maintaining soil functions and heterogeneity of understory plant communities after 20 years; composition and structure being similar to long-undisturbed forests.

Timber harvest interacts with broad-scale forest mortality to affect site occupancy dynamics of a vertebrate seed predator

Extensive ecological disturbances can interact with spatial heterogeneity produced by previous disturbances, influencing responses of vertebrates to environmental change. Recent and ongoing outbreaks of bark beetles (including Dendroctonus spp. and Dryocoetes confuses) in the Rocky Mountains produced an opportunity to investigate effects of broad-scale tree mortality on an important seed predator in Nearctic coniferous forests, the red squirrel (Tamiasciurus hudsonicus), and to evaluate whether those effects interact with forest heterogeneity produced by previous timber harvest. Our study characterized site occupancy dynamics for red squirrels in relation to patch-cutting, a type of group-selection cut, and the bark-beetle outbreak, and evaluated whether patch cutting influenced subsequent effects of bark beetles on these squirrels. We used multi-season occupancy models and covariates for harvest- and outbreak-related habitat characteristics to describe extinction and colonization rates of red squirrels over a 27-yr period in Wyoming, USA. We observed effects of year, patch-cutting, and the bark beetle outbreak on the probability of detecting a red squirrel. We observed a negative association between local extinction rate and increasing snag density, but only to a threshold of 5 snags/0.04ha. Local colonization rate was positively associated with the basal area of live trees. Annual site occupancy varied across years (range pre-harvest: 0.76–0.89; post-harvest: 0.84–0.99), and was lowest (0.70–0.72) during the two years sampling occurred approximately 14years after the bark beetle outbreaks began. Tree mortality was lowest near patch cuts; this pattern was especially pronounced for mature trees (>30cm diameter at breast height), which tend to produce the most cones and would likely contribute the most to red squirrel survival. Strong habitat effects on occupancy dynamics suggest that previously-harvested areas may provide refugia for red squirrels in post-outbreak forests. Our results support managing for uneven-aged stands of mixed species composition in subalpine forests of the Rocky Mountains.

Effects of timber harvests and silvicultural edges on terrestrial salamanders.

Balancing timber production and conservation in forest management requires an understanding of how timber harvests affect wildlife species. Terrestrial salamanders are useful indicators of mature forest ecosystem health due to their importance to ecosystem processes and sensitivity to environmental change. However, the effects of timber harvests on salamanders, though often researched, are still not well understood. To further this understanding, we used artificial cover objects to monitor the relative abundance of terrestrial salamanders for two seasons (fall and spring) pre-harvest and five seasons post-harvest in six forest management treatments, and for three seasons post-harvest across the edge gradients of six recent clearcuts. In total, we recorded 19,048 encounters representing nine species of salamanders. We observed declines in mean encounters of eastern red-backed salamanders (Plethodon cinereus) and northern slimy salamanders (P. glutinosus) from pre- to post-harvest in group selection cuts and in clearcuts. However, we found no evidence of salamander declines at shelterwoods and forested sites adjacent to harvests. Edge effects induced by recent clearcuts influenced salamanders for approximately 20 m into the forest, but edge influence varied by slope orientation. Temperature, soil moisture, and canopy cover were all correlated with salamander counts. Our results suggest silvicultural techniques that remove the forest canopy negatively affect salamander relative abundance on the local scale during the years immediately following harvest, and that the depth of edge influence of clearcuts on terrestrial salamanders is relatively shallow (<20 m). Small harvests (<4 ha) and techniques that leave the forest canopy intact may be compatible with maintaining terrestrial salamander populations across a forested landscape. Our results demonstrate the importance of examining species-specific responses and monitoring salamanders across multiple seasons and years. Long-term monitoring will be necessary to understand the full impacts of forest management on terrestrial salamanders.

Tree mortality after synchronized forest insect outbreaks: Effects of tree species, bole diameter, and cutting history

A recent series of bark beetle outbreaks in the Rocky Mountain region of the U.S. is the largest and most intense ever recorded. Factors contributing to tree mortality from bark beetles are complex, but include aspects of forest stand condition. Because stand conditions respond to forest management, evaluating bark beetle-caused tree mortality and changes in forest structural attributes in areas previously subjected to management not only improves mechanistic understanding of beetle-caused changes in forests, but also improves prediction of future bark beetle responses to management regimes. We retrospectively assessed mortality of lodgepole pine (Pinus contorta), Engelmann spruce (Picea engelmannii), and subalpine fir (Abies lasiocarpa), and stand structure in two watersheds in south-central Wyoming, U.S.A. following outbreaks of mountain pine beetle (Dendroctonus ponderosae), spruce beetle (Dendroctonus rufipennis), and western balsam beetle (Dryocoetes confusus). One watershed received 240 patch cuts (mean area 1.5ha), a type of group selection cut, six years before the beetle outbreaks began; the other watershed received no active management (control). We conducted surveys of forest vegetation attributes over 27yrs, during pre-harvest, post-harvest, and post-outbreak periods. After the outbreak, lodgepole pine and Engelmann spruce mortality increased with increasing bole diameters and basal area of each species, but patterns of mortality were influenced by patch-cutting. Large-diameter trees in or near patch cuts tended to escape attack by bark beetles. Away from patch cuts (⩾15m), mortality of smaller lodgepole pine was higher compared to the control watershed. Based on our observed patterns of tree mortality, we hypothesize a changing pattern of host selection (i.e., selection for smaller trees) was influenced by stand conditions that created more suitable conditions for bark beetles in areas between patch cuts in the treated watershed. Snag density increased from pre-harvest to post-outbreak periods, but log density was similar, suggesting most dead trees remained standing at the time of data collection. Canopy cover did not decrease as expected, and ground cover did not change substantially from pre-harvest to post-outbreak periods. Patch-cutting improved survival probability of large-diameter lodgepole pine and Engelmann spruce during outbreaks of multiple species of bark beetle, although reduced losses were only realized for trees in or near (⩽15m) patch cuts. However, during intense, broad-scale tree mortality events, these benefits may be important in reducing the loss of mature trees to bark beetles and promoting retention of a larger cohort of mature trees post-outbreak.

Managing the forest for more than the trees: effects of experimental timber harvest on forest Lepidoptera

Studies of the effects of timber harvest on forest insect communities have rarely considered how disturbance from a range of harvest levels interacts with temporal variation in species diversity to affect community resistance to change. Here I report the results of a landscape-scale, before-and-after, treatment-control experiment designed to test how communities of forest Lepidoptera experience (1) changes in species richness and composition and (2) shifts in species dominance one year after logging. I sampled Lepidoptera from 20 forest stands allocated to three harvest treatments (control, even-aged shelterwood or clearcuts, and uneven-aged group selection cuts) within three watersheds at Morgan-Monroe State Forest, Indiana, USA. Moths were sampled from all forest stands one year prior to harvest in 2007 and immediately post-harvest in 2009. Species composition was most significantly affected by temporal variation between years, although uneven-aged management also caused significant changes in lepidopteran community structure. Furthermore, species richness of Lepidoptera was higher in 2007 compared to 2009 across all watersheds and forest stands. The decrease in species richness between years, however, was much larger in even-aged and uneven-aged management units compared to the control. Furthermore, matrix stands within the even-aged management unit demonstrated the highest resistance to species loss within any management unit. Species dominance was highly resistant to effects of timber harvest, with pre- and post-harvest values for Simpson diversity nearly invariant. Counter to prediction, however, the suite of dominant taxa differed dramatically among the three management units post-harvest. My results suggest that temporal variation may have strong interactions with timber harvest, precipitating loss of nearly 50% species richness from managed stands regardless of harvest level. Even-aged management, however, appeared to leave the smallest "footprint" on moth communities. Timber harvest also created greater heterogeneity in species dominance among management units, suggesting that forest watersheds may diverge in post-harvest recovery transients relative to unlogged watersheds in Morgan-Monroe State Forest. Because moth communities appear to be highly sensitive to group-selection cuts, shelterwood cuts, and clearcuts, it will be important to retain unlogged concessions within management units to resist landscape-level loss of Lepidoptera.

Reprint of: Lessons from long-term studies of harvest methods in southwestern ponderosa pine–Gambel oak forests on the Fort Valley Experimental Forest, Arizona, U.S.A.

The Fort Valley Experiment Station (now Fort Valley Experimental Forest) has contributed many long-term studies to forest research. This paper focuses on a “Methods of Cutting” study initiated in 1913 on the Coulter Ranch Unit of Fort Valley and how that long-term study yielded important ecological and management lessons. We quantified the historical and contemporary forest patterns at this ponderosa pine–Gambel oak site, which was harvested using three different harvesting systems in 1913 (seed tree, group selection, and light selection) and was partially excluded from livestock browsing in 1919. Using nine historically stem-mapped permanent plots for the following three stand structural scenarios: 1913 pre-harvest (modeled), post-harvest (actual), and 2003–2006 (actual) conditions, we examined the short- and long-term consequences of harvest and livestock grazing land-use and stand dynamics. We assessed changes in spatial pattern under each harvesting system and in each structural scenario, and lastly, we examined spatial and temporal tree recruitment patterns as observed in the contemporary (2003–2006) conditions. The seed tree harvests effectively converted the spatial patterns from aggregated to random and left few trees, while the group selection and light selection had varying effects, but consistently exaggerated the spatial patchiness of the stand. By 2003–2006, all plots were aggregated at all scales and were one large patch of predominately small trees. Sites that were harvested, but excluded from livestock browsing had 40% more trees in 2003–2006. Contemporary recruitment patterns were significantly aggregated under all harvesting systems, but were most strongly aggregated if the site received a group selection or light selection cut. For group and light selection, pine seedlings initially established in stump patches created by harvesting and then proceeded to fill-in the remaining area, with recruitment rarely found under the residual pine or oak trees. Long-term data sets, such as these established by the Fort Valley Experimental Forest in 1913, are essential for quantifying the impact of historical land-use practices on contemporary forest composition and structure. Ignoring land-use legacies may lead to the misinterpretation of stand dynamics and development, and therefore should be explicitly quantified and incorporated into future management and restoration activities.

Lessons from long-term studies of harvest methods in southwestern ponderosa pine–Gambel oak forests on the Fort Valley Experimental Forest, Arizona, U.S.A.

The Fort Valley Experiment Station (now Fort Valley Experimental Forest) has contributed many long-term studies to forest research. This paper focuses on a “Methods of Cutting” study initiated in 1913 on the Coulter Ranch Unit of Fort Valley and how that long-term study yielded important ecological and management lessons. We quantified the historical and contemporary forest patterns at this ponderosa pine–Gambel oak site, which was harvested using three different harvesting systems in 1913 (seed tree, group selection, and light selection) and was partially excluded from livestock browsing in 1919. Using nine historically stem-mapped permanent plots for the following three stand structural scenarios: 1913 pre-harvest (modeled), post-harvest (actual), and 2003–2006 (actual) conditions, we examined the short- and long-term consequences of harvest and livestock grazing land-use and stand dynamics. We assessed changes in spatial pattern under each harvesting system and in each structural scenario, and lastly, we examined spatial and temporal tree recruitment patterns as observed in the contemporary (2003–2006) conditions. The seed tree harvests effectively converted the spatial patterns from aggregated to random and left few trees, while the group selection and light selection had varying effects, but consistently exaggerated the spatial patchiness of the stand. By 2003–2006, all plots were aggregated at all scales and were one large patch of predominately small trees. Sites that were harvested, but excluded from livestock browsing had 40% more trees in 2003–2006. Contemporary recruitment patterns were significantly aggregated under all harvesting systems, but were most strongly aggregated if the site received a group selection or light selection cut. For group and light selection, pine seedlings initially established in stump patches created by harvesting and then proceeded to fill-in the remaining area, with recruitment rarely found under the residual pine or oak trees. Long-term data sets, such as these established by the Fort Valley Experimental Forest in 1913, are essential for quantifying the impact of historical land-use practices on contemporary forest composition and structure. Ignoring land-use legacies may lead to the misinterpretation of stand dynamics and development, and therefore should be explicitly quantified and incorporated into future management and restoration activities.

Small-mammal response to group-selection silvicultural systems in Engelmann spruce – subalpine fir forests 14 years postharvest

Concerns about the impacts of clear-cut harvesting on ecosystem components in subalpine forests have generated a variety of alternative silvicultural systems in high-elevation forests in western North America. We examined responses of forest-floor small mammals, 14 years posttreatment, in four replicate units, uncut forest, a 1.0 ha group-selection cut, a large (&gt;30 ha) clearcut, and the edge between the group-selection cut and uncut forest, in the Engelmann Spruce ( Picea engelmannii Parry ex Engelm.) – Subalpine Fir ( Abies lasiocarpa (Hook.) Nutt.) biogeoclimatic zone in south-central British Columbia, Canada. Populations of small mammals were livetrapped during five sessions from June to September 2006. The mean abundance of southern red-backed voles ( Myodes gapperi Vigors) was significantly lower on large clearcuts than in uncut old-growth forests, with intermediate numbers in 1 ha cuts. The opposite trend was found for dusky shrews ( Sorex monticolus Merriam), while there was no significant difference in mean abundance of deer mice ( Peromyscus maniculatus Wagner) among treatments. Trappability, proportion of adult females breeding, and rate of survival of red-backed voles and deer mice were similar among treatments. Our results suggest that group-selection silviculture conducted in subalpine forests may have fewer negative impacts on the small-mammal community than large clearcuts.

Short- and long-term implications of clearcut and two-age silviculture for conservation of breeding forest birds in the central Appalachians, USA

Two-age (deferment or leave tree) harvesting is used increasingly in even-aged forest management, but long-term responses of breeding avifauna to retention of residual canopy trees have not been investigated. Breeding bird surveys completed in 1994–1996 in two-age and clearcut harvests in the central Appalachian Mountains of West Virginia, USA allowed us to document long-term changes in these stands. In 2005 and 2006, we conducted point counts in mature unharvested forest stands and in 19–26 year-old clearcut and two-age harvests from the original study and in younger clearcut and two-age stands (6–10 years old). We found differences in breeding bird metrics among these five treatments and temporal differences in the original stands. Although early-successional species are typically absent from group selection cuts, they were almost as common in young two-age stands as clearcuts, supporting two-age harvests as an alternative to clearcutting. Although older harvests had lower species richness and diversity, they were beginning to provide habitat for some species of late-successional forest songbirds that were absent or uncommon in young harvests. Overall, late-successional forest-interior species were more flexible in their use of different seral stages; several species used both age classes and harvest types in addition to mature forest, which may reflect the lack of edges in our heavily-forested landscape. Consequently, two-age management provides habitat for a diverse group of species as these stands mature and may be an ecologically sustainable alternative to clearcutting in landscapes where brown-headed cowbirds ( Molothrus ater) are uncommon.

USE OF GROUP-SELECTION AND SEED-TREE CUTS BY THREE EARLY-SUCCESSIONAL MIGRATORY SPECIES IN ARKANSAS

Silviculture in the Ouachita National Forest in Arkansas and Oklahoma has shifted in recent years from mostly even-aged management to a mix of even- and uneven-aged regeneration systems, including group-selection. Researchers have described presence/absence of early-successional bird species in forest openings created by even- and uneven-aged silviculture, but few have examined nest success. We examined occupancy and nest success of three early-successional species—Indigo Bunting (Passerina cyanea), Yellow-breasted Chat (Icteria virens), and Prairie Warbler (Dendroica discolor)—within 6- and 7-year-old openings created by group-selection (uneven-aged, ≤0.8 ha) and seed-tree (even-aged, 11–16 ha) cuts in Arkansas. We found 54 Indigo Bunting nests in openings created by seed-tree cuts and 28 in openings created by group-selection cuts (hereafter “seed-tree stands” and “group-selection stands,” respectively). We found 50 Yellow-breasted Chat nests in seed-tree stands, but only 2 were found in group-selection stands. We found 14 Prairie Warbler nests in seed-tree and none in group-selection stands. Mayfield nest success for Indigo Bunting was 30.9% in seed-tree stands and 41.9% in group-selection openings, but there was no difference in daily nest survival (0.952 ± 0.009 and 0.964 ± 0.010, respectively; χ2 = 0.792, P = 0.37). Our data suggest that Indigo Buntings can nest successfully in both regenerating seed-tree and group-selection stands; however, group-selection openings may be too small to support nesting Yellow-breasted Chats and Prairie Warblers. Public concerns about clear-cutting have resulted in increased use of uneven-aged management by the USDA Forest Service. However, before widespread implementation of group-selection cutting, additional research should be conducted to evaluate the effects of this management strategy on Neotropical migratory bird communities.

SNAGS, CAVITY-NESTING BIRDS, AND SILVICULTURAL TREATMENTS IN WESTERN OREGON

We examined cavity-nesting bird use of natural snags (n = 221) and 10- to 12-year-old snags (n = 836) created by topping mature conifers in 3 silvicultural treatments (group-selection cuts, 2-story regeneration harvests, clearcuts with retained trees) and 2 snag arrangements (clustered, scattered) in 30 Douglas-fir (Pseudotsuga menziesii) stands in the Oregon Coast Range. Eight bird species nested in created snags. Open-canopy stands (2-story and clearcut treatments) had higher levels of avian nesting, species richness, and species diversity compared to closed-canopy, group-selection stands. We did not find a difference in nesting levels between clustered and scattered snags. In created snags, most active nests were in the top 25% of the bole, cavity entrances typically faced northeast, and the presence of dead branches did not alter use of snags for nesting. Topped conifers that remained alive (n = 102) were rarely used for nesting or foraging. Since the last survey 6 years prior to our survey, the number of cavities per created snag per silvicultural treatment increased 3.3- to 6-fold, and we observed 4 additional avian species nesting; 3 were secondary cavity nesters. Total cavities per snag averaged 5.1, 4.3, and 2.5 for created snags, natural snags >12 years old, and natural snags <12 years old, respectively. Only 1 created snag fell in the decade since topping. Natural new snag recruitment resulting from residual green tree mortality was highest in 2-story stands (0.76 snag/ha) and lowest in clearcuts (0.20 snag/ha). Snags created by topping large conifers provided nesting and foraging structures for cavity-nesting birds under a range of silvicultural conditions, and use was influenced more by residual green tree density than snag arrangement. In addition, created snags increased in value for birds through their first decade (88% had cavities). Because snags created by topping last long and are readily used by birds, they should be considered a management option to improve avian habitat in managed forests.

The effects of three regeneration harvest methods on plant diversity and soil characteristics in the southern Appalachians

We evaluated the effects of three regeneration harvest methods on plant diversity and soil resource availability in mixed-hardwood ecosystems. The study area is in the Wine Spring Creek watershed on the Nantahala National Forest of the Southern Appalachian Mountains in western North Carolina. The regeneration treatments were: an irregular, two-aged shelterwood cut (2A), with 5.0 m 2/ha residual basal area; a shelterwood cut (SW), with 9.0 m 2/ha residual basal area; a group selection cut (GS), with 0.10–0.20 ha openings and 25% overstory removal on area basis at first entry; fourth, the control, consisted of two uncut sites (UC). Each harvest treatment was replicated three times across the landscape in similar plant community types. Within each treatment area, permanent plots were marked and inventoried for overstory, midstory, and herbaceous layer plants. In each permanent plot, we collected soil samples in winter (December–March) to reduce temporal variation due to vegetation phenological stage and rainfall events. We analyzed soil samples for extractable calcium (Ca), magnesium (Mg), potassium (K), cation exchange capacity (CEC), pH, bulk density, A-horizon depth, total carbon (C), and nitrogen (N). Species diversity of overstory, understory, and herbaceous layer species was evaluated using species richness ( S), Shannon–Wiener's index of diversity ( H′), and Pielou's evenness index ( E). We used direct gradient analysis (non-metric multidimensional scaling, NMS) to explore the changes in vegetation–site relationships among herbaceous layer abundance, and soil characteristics and overstory basal area between pre-harvest (1994) and post-harvest (2000). Twelve minor overstory species were cut from the 2A treatments and nine species were cut from the SW treatments. Thus, it is not surprising that S and H′ were reduced in the overstory on the heavily cut sites. However, most of these species sprouted from cut stumps and were substantially more abundant in the midstory layer after harvest than before. For the midstory, we found higher S and H′ on the harvested treatments than the control; however, H′ did not differ significantly among the harvest treatments. We measured an increase in herbaceous layer H′ on the more heavily cut treatments (2A and SW) after harvest. We found an increase in average distance in the NMS ordination among sites in 2000 compared to 1994, which suggests greater herbaceous species diversity after harvest. However, we did not see a clear separation among harvest treatments in the NMS ordination.

Conifer response to three silvicultural treatments in the Oregon Coast Range foothills

This study assessed growth, condition, and mortality of residual trees one decade after harvest across three silvicultural treatments in thirty 85- to 125-year-old Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) stands in the Oregon Coast Range foothills. Group-selection cuts had 33% of the entire stand volume extracted as patches approximately 0.2–0.8 ha in size; two-story regeneration harvests had 75% of the volume extracted, and 20–30 residual trees/ha were left; clearcuts had all trees removed, except for 1.2 trees/ha. One decade after harvest, tree basal area, diameter, and height growth, and crown width and fullness did not differ between silvicultural treatments. In contrast, live crown ratio was largest in clearcuts (0.74), and the proportion of trees with epicormic branching was highest in two-story stands (35%). Overall, 45% of trees had more basal area growth in the decade after harvest than in the previous decade. Residual green trees in clearcuts and group-selection stands experienced the highest and lowest percentage mortality, respectively (30.6% vs. 0.2%). Our results reflect little differentiation in the characteristics of trees growing under three silvicultural conditions one decade after harvest. However, percent residual green tree mortality increased with increasing harvest intensity.

Options for managing early-successional forest and shrubland bird habitats in the northeastern United States

Historically, forests in the northeastern United States were disturbed by fire, wind, Native American agriculture, flooding, and beavers ( Castor canadensis). Of these, wind and beavers are now the only sources of natural disturbance. Most disturbance-dependent species, especially birds, are declining throughout the region whereas species affiliated with mature forests are generally increasing or maintaining populations. Disturbance must be simulated for conservation of early-successional species, many of which are habitat specialists compared to those associated with mature forests. Both the maintenance of old fields and forest regeneration are needed to conserve brushland species. Regenerating forest habitats are more ephemeral than other woody early-successional habitats. The types and amounts of early-successional habitats created depend on the silvicultural system used, patch size selected, time between regeneration cuts, and rotation age. We recommend that group selection and patch cuts should be at least 0.8 ha, and patches should be generated approximately every 10–15 years depending on site quality. Regeneration of intolerant and mid-tolerant tree species should be increased or maintained in managed stands. Also, frost pockets, unstocked, or poorly-stocked stands can provide opportunities to increase the proportion of early-successional habitats in managed forests.

Short-term impacts of partial cutting on lichen retention and canopy microclimate in an Engelmann spruce – subalpine fir forest in north-central British Columbia

The retention of canopy lichens (Alectoria, Bryoria, and foliose) in group selection (GS) and single-tree selection (STS) partial cuts (30% removal) was studied within a subalpine spruce–fir forest (Picea englemannii Parry ex Engelm. – Abies lasiocarpa (Hook.) Nutt.) in north-central British Columbia. Baseline canopy lichen loading (preharvest and immediate postharvest) was compared with lichen loading 2 years after harvesting, using both ground- and canopy-based sampling techniques. Additionally, canopy microclimate was compared between GS and adjacent stand areas with no harvest treatment (NT). Partial cutting did not have a significant effect on lichen loading in residual trees, although a trend of declining lichen abundance was observed in each of the GS, STS, and NT areas. Partitioning of lichen abundance data showed significant postharvest declines for upper canopy STS Bryoria and smaller, but significant, changes in foliose lichen abundance in the NT and STS areas. No significant changes in canopy microclimate were observed between treatments, with the exception of south-facing aspects in GS trees, which showed reduced duration of lichen hydration. Taken together, these factors suggest that although the placement of Bryoria in residual trees may shift towards lower canopy exposures, partial-cut harvest treatments can maintain short-term lichen loading and associated ecosystem values (e.g., caribou forage) in subalpine spruce–fir stands.

Do Shade and Shrubs Enhance Natural Regeneration of Douglas-Fir in South-Central Idaho?

Abstract Shade duration and shrub composition in microsites with naturally regenerated Douglas-fir seedlings (Pseudotsuga menziesii var. glauca) were compared to randomly located control plots without seedlings in hot, dry group selection cuts in the southernmost Boise National Forest. Shade duration was estimated using a sighting device which allowed quantification of the degrees of the sun's arc intercepted by timber, shrubs, or other obstructions. Measurements were standardized for the median date for summer high temperatures. Seedlings received more whole-day (P&lt;0.001) and afternoon (P&lt;0.001) shade than control plots, and seedlings on southern exposures received more shade than those on other aspects. Seedling plots had more shrub cover than control plots (P&lt;0.007). However, of nine shrub species examined, only buckbrush exhibited a significantly positive association with seedlings. Soil surface temperatures under buckbrush were reduced more than under other species, and unshaded surfaces remained above 50°C for extended time periods. These results suggest that natural regeneration of Douglas-fir may be enhanced by harvest practices and site preparation methods which provide shade during critical stages of germination and early seedling establishment. West. J. Appl. For. 10(1):24-28.

Impact of Group Selection Silviculture on Timber Harvesting Productivity and Cost in Appalachian Hardwood Timber Stands

Abstract Group selection is a regeneration harvest method that is being promoted by the USDA Forest Service as an alternative to clearcutting. In a group selection cut, "groups" of trees are marked and harvested in small patches dispersed in a mosaic pattern throughout the timber stand. Group selection has the potential to increase harvesting cost as compared to traditional clearcutting. Three logging systems, a skyline yarder system, a feller-buncher/cable skidder system, and a chainsaw felling/cable skidder system were studied while logging group selection timber sales in the Jefferson National Forest in Virginia. Time study data on the felling and skidding functions were recorded, as well as weekly production and cost data for each operation. Historic clearcutting production was obtained from the study loggers' records for comparison purposes. Group selection unit costs were $39.72, $14.13, and $15.33 per ton for the three systems, respectively. The study systems experienced decreases in production ranging front 17% to 52%. Most of the production decrease was due to an excessive amount of unproductive time directly resulting from the impact of the small, dispersed, multiple-harvest areas on the loggers' normal operating procedure and work flow. North. J. Appl. For. 10(4): 170-174.

Effects of logging on capercaillie (Tetrao urogallus) leks

Display activity and population size of 2 experimentally logged leks were compared with 7 untreated control leks in a coniferous area in southcentral Norway, during 1974–87. Leks were treated by thinnings and small‐scale seed‐tree‐ and clearcuttings. Number of displaying cocks increased on all leks, but the experimental lek populations increased more than the controls. Displaying cocks were either indifferent to or preferred the logged areas, and recruiting cocks established display sites at newly created group selection cuts and at the edge of seed‐tree and clearcuts. The findings indicate that moderate thinnings, leaving >500 stems/ha, and clearcuts <50 m in diameter, are acceptable cutting methods within T. urogallus leks, with the reservations that lek populations should not be smaller than 5 displaying cocks, and that surrounding habitats should contain >50% old forest.

An Evaluation of Four Uneven-age Cutting Practices in Central Appalachian Hardwoods

Abstract Uneven-age cutting practices discussed include individual tree selection, group selection, diameter limit, and financial maturity. Of these, only the individual selection practice has the necessary guidelines to regulate stand composition in the uneven-age management system. Group-selection, diameter-limit, and financial-maturity cuts are regeneration methods used to produce uneven-aged stands. Strengths, weaknesses, and methods of application of each cutting practice are described as they relate to central Appalachian hardwoods.