Single-tree Selection Harvesting Research Articles

Six year efficacy of silvicultural treatments to control American beech regeneration in stands affected by beech bark disease in Ontario, Canada

High beech regeneration density is a concern in northern shade tolerant hardwood forests. High densities of beech ( Fagus grandifolia Ehrh) regeneration can crowd out other desirable species, such as sugar maple ( Acer saccharum Marsh.), and jeopardize long-term sustainability since beech is under threat from beech bark disease ( Cryptococcus fagisuga/Neonectria spp. Complex). We examined the efficacy of three tending (no tending, brush saw, and basal bark herbicide) and two timing and harvesting (deferred 5 years post-single tree selection harvest, concurrent with uniform shelterwood harvest) treatments on reducing beech regeneration density and promoting sugar maple regeneration density over 6 years. Six years after tending, we found that large beech regeneration density was reduced, medium beech regeneration density had recovered to pre-tending levels in most treatments, and small beech regeneration density remained unaffected. Tending treatments had no effect on any size class of sugar maple regeneration density but the uniform shelterwood harvest promoted medium sugar maple density more than the single-tree selection harvest. Despite this increase, in all treatment combinations sugar maple regeneration densities remained below stocking targets. Our results suggest that while tending treatments can temporarily reduce beech regeneration densities, sugar maple is unable to take advantage of the increased growing space.

Residual Stand Structure and Topography Predict Initial Survival and Animal Browsing of Redwood and Douglas-Fir Seedlings Planted in Coastal Forests of Northern California

Successful regeneration of commercial species is central to the long-term sustainability of forests managed for wood production. We studied two species of tree seedlings planted after group selection and single-tree selection harvesting in a 20 ha replicated silviculture experiment in stands dominated by coast redwood (Sequoia sempervirens (D.Don) Endl.). Treatments consisted of complete harvest in 1 ha group selection opening (GS), low-density dispersed retention (LD), aggregated high-density retention (HA), and dispersed high-density retention (HD). One year after planting, seedlings planted on a southwest aspect had the lowest survival rate, while northeast aspects had nearly complete survival rates. As expected, redwood had a higher survival rate than coast Douglas-fir (Pseudotsuga menziesii var menziesii (Mirb.) Franco). Survival rates exhibited a rise-peak-fall pattern with stand density, most notably on southwest-facing slopes, ranking LD > HA ≈ HD > GS treatments. Deer browsing of planted seedlings was a pervasive problem where Douglas-fir were preferentially browsed over redwood. In treatments with higher retention densities, browsing was less likely, ranking GS > LD > HA > HD treatments. Further from watercourses at higher elevation, the probability of browsing diminished. Overall, dispersed treatments outperformed aggregated and GS treatments by simultaneously maximizing survival and minimizing browsing of planted seedlings. We did not perform site preparation or herbicide treatment of re-sprouting hardwoods following harvest, and therefore recommend testing the effectiveness of understory vegetation management to enhance seedling survival. Consideration could also be given to planting more seedlings in anticipation of lower survival rates, and/or implementing seedling protection measures when and where heavy browsing is expected.

Influence of silvicultural practices in northern hardwood forests on a long-lived perennial herb, Trillium cernuum L.

Contemporary and predicted declines in tree species diversity and forest resilience have prompted renewed interest in even-aged systems and/or site preparation to overcome bottlenecks to tree recruitment or facilitate range expansion of future-adapted species. The impact of this intensification on the herbaceous layer in forests traditionally managed with uneven-aged systems, however, is unclear, especially for uncommon dispersal limited species with heterogenous distributions. We leveraged a large-scale experiment (the Northern Hardwood Silvicultural Experiment to Enhance Diversity) to investigate the response of Trillium cernuum L., a somewhat uncommon and heterogeneously distributed non-clonal herb in our study system, to a gradient of canopy removal and soil disturbance. We monitored 16 small populations from 2015 (the year prior to treatment) to 2019 (3-years post treatment). Our results suggest that initial population size and stage structure were inextricably coupled with T. cernuum response. Independent of treatment, T. cernuum abundance and flowering generally increased over time commensurate with initial population size. Moreover, our study highlights the confounding effect of deer herbivory, which increased significantly following treatment. Collectively, our findings suggest that T. cernuum populations were resilient to canopy disturbance associated with single-tree selection and shelterwood harvests and the levels of scarification applied as part of our study. Higher levels of site impact or other site preparation methods such as herbicides will likely have greater impacts and warrant further investigation. Our results also suggest that directly monitoring populations of interest may be necessary to quantify treatment effects for uncommon and/or heterogenous species that are missed with common plot-based sampling designs or of conservation concern.

Population and Community Responses of Small Mammals to Single-tree Selection Harvest in Laurentian Hardwood Forests

Small mammals are ubiquitous members of vertebrate communities that are sensitive to habitat change. In the Great Lakes region of North America, small mammal communities have changed rapidly, but experimental tests of potential mechanisms are lacking. Using a before-after, control-treatment design, we quantified the response of small mammals to single-tree selection harvest in Laurentian hardwood forests of Wisconsin, United States. We documented changes in forest structure and small mammal abundance, species diversity, and community similarity from silvicultural treatment. Treatment reduced tree density and canopy cover and increased mean tree diameter, woody stem density, variation in woody stem density, and volume of coarse woody debris. Peromyscus and northern short-tailed shrews (Blarina brevicauda) were dominant community members across treatments and years. White-footed mice (P. leucopus) outnumbered woodland deer mice (P. maniculatus gracilis) before treatment, but declined by almost fifty percent after treatment; deer mice and total rodent (i.e., Rodentia) abundances were unchanged. Small mammal species diversity increased twofold following treatment. Our experiment identified species-specific responses within Peromyscus to timber harvest: white-footed mice, the numerically dominant and generalist species, were most sensitive to habitat change, and their response produced cascading effects to small mammal community structure. Future experiments should assess these small mammal responses in a multi-year framework and quantify their effects on the broader vertebrate community.

Sugar maple (Acer saccharum) Seedling Bank Response to Storm Disturbance and Single Tree Selection Harvest in the Southern Keweenaw Peninsula, Michigan

This case study seeks to fill a critical knowledge gap regarding how natural wind disturbance affects stand and seedling bank diversity in mixed northern hardwood forests managed by single tree selection harvest methods. Contemporary timber harvests on state managed lands in Michigan's Upper Peninsula employ single tree selection cutting methods to promote more complex age structure in second growth stands dominated by sugar maple (Acer saccharum). However, concern exists that single tree selection harvest may result in lowered compositional diversity of seedlings as the low light conditions of small dispersed gaps exclude less shade tolerant species from gap regeneration. In July 2016 severe thunderstorms with winds in excess of 145 km/h (90 mph) caused extensive tree fall and canopy gap creation in second growth mixed northern hardwood forests in the southern Keweenaw Peninsula. We measured the species composition of overstory tree mortality and understory seedling regeneration in 14 storm gaps created in stands with and without previous single tree selection harvest. Storm gaps ranged in size from 125 to 1100 m2. American basswood (Tilia americana) was disproportionately wind-thrown. Robust seedling regeneration was released in all storm gaps, with sugar maple comprising more than 75% of mean seedling abundance, regardless of previous single tree selection harvest. Sugar maple and ironwood (Ostrya virginiana) comprised 80% of sapling abundance. Results indicate single tree selection of mixed northern hardwood stands does not exacerbate, but rather emulates, dense sugar maple regeneration found on unmanaged second growth sites.

Insights on motor-manual tree felling in Germany, recent developments to ensure efficient operations in singletree selection harvest

Despite an intensive mechanization trend in German forest operations since the early 1990s, many sites restrict the efficient implementation of fully mechanized harvesting systems. Trafficability and singletree selection harvest-based silviculture, focusing on high stem volume broadleaves, such as European beech, are the main limitations. Thus, motor-manual operations are still prevalent but need to be adapted to stay efficient and improve safety in a changing work environment. Recent developments of new felling techniques and aiding tools and advances in training and work organization improved occupational health and safety. Also, these achievements help to avoid log devaluation due to felling damages. The general digitalization trend did not ignore motor-manual operations either. Smartphone applications can already contribute to more efficient bucking, operation planning and fleet management. Yet, motor-manual operations will remain cost-intensive, and expose worker directly to occupational hazards. Therefore, operations should take as much advantage of mechanized systems as possible for feasible and applicable silvicultural objectives.

Gap and stand structural characteristics in a managed and an unmanaged old-growth oriental beech (Fagus orientalisLipsky) forest

AbstractSimplified forest structures following even-age management have been associated with the loss of biodiversity, which may be avoided through disturbance-inspired silviculture. Here, we ask how much do gap characteristics in a managed old-growth differ from those in unmanaged old-growth subject only to natural dynamics? In this study, we compared important characteristics of gaps (e.g. canopy gap fraction, distribution of gap sizes) and gapmakers (e.g. size classes, frequency, decay classes) between a managed and an adjacent unmanaged old-growth Oriental beech (Fagus orientalis Lipsky) compartment in the Keladarsht region of northern Iran 10 years after a single harvest entry using single-tree selection. Canopy openings >100 m2 with visible remnants of gapmakers (i.e. stumps) were included in this study. Gap characteristics of both compartments were within typical ranges for old-growth beech. Nonetheless, small but potentially important differences between the two areas were observed. In the managed compartment, harvesting poor quality trees with structural defects and typical diameters at breast height >52.5 cm plus natural mortality resulted in 102 canopy gaps (1–6 gapmakers, averaging 3.5 gaps/ha, gap fraction 9.8 per cent) compared with 59 natural canopy gaps (1–7 gapmakers, averaging 2.6 gaps/ha, gap fraction 13.7 per cent) in the unmanaged compartment. In both compartments, medium-sized gaps (200–500 m2) were most prevalent. In the managed compartment, 60 per cent of gapmakers were large or very large (typically cut) compared with 39 per cent in the unmanaged compartment where large trees typically snapped and became snags. Uprooting, particularly of small and medium sized gapmakers, was less common in the managed than the unmanaged compartment. Our results indicate that even one single-tree selection harvest may lead to a short-term divergence in stand structure compared with the unmanaged forest. While such managed forests may no longer be considered as old-growth, divergences in canopy gap characteristics indicate that a more nuanced harvesting scheme that includes cutting some larger gaps may more closely mimic the canopy dynamics of this old-growth forest.

Factors influencing endangered bat conservation management by professional foresters

Integration of conservation efforts that benefit endangered species in forest lands of the U.S. are highly dependent on the decisions made by professional foresters. Federal guidelines generally do not require private landowners to search for endangered species before conducting forest management activities. Because private lands make up 85% of Indiana’s forests, recommendations by professional foresters can influence a large proportion of the management decisions made on Indiana bat (Myotis sodalis) habitat in the state. Thus, we wanted to determine what factors lead professional foresters in Indiana to adopt management strategies that benefit bat conservation. We conducted an online survey of Indiana consultant and state foresters to address two main objectives: (1) to assess forester understanding of guidelines for adequate bat habitat, and (2) to identify the factors that influence professional forester intention to manage forests to improve bat habitat quality. For a subset of survey respondents, we also determined whether forester intent to manage for Indiana bat habitat translated to on-the-ground behavior via an assessment of their stands marked for single-tree selection harvest. We found that most respondents knew some of the forest management guidelines for the Indiana bat, but few were familiar with all guidelines. Through structural equation modeling, we determined that intention to manage forests for the Indiana bat was influenced most by whether foresters believed following the guidelines would strongly influence the conservation of the species. We found a difference in the relative strength (path loading) of this factor between government and consultant foresters. We assessed the management decisions of a subsample of our survey respondents and found that respondent’s decisions aligned with their intention to maintain or create Indiana bat habitat. We suggest two strategies can be employed to improve the habitat management occurring on private lands in Indiana: (1) increasing forester knowledge of federal guidelines and (2) providing evidence to foresters that these guidelines directly contribute to Indiana bat conservation.

Understory light predicts stump sprout growth in mixed multiaged stands in north coastal California

Regeneration of commercial species is central to long-term success of multiaged management for wood production. We examined relationships between understory light, varying overstory tree retention, and growth of coast redwood (Sequoia sempervirens; commercial species) and tanoak (Notholithocarpus densiflorus) stump sprouts initiated by group selection and single-tree selection harvesting in 80–100 year old mixed stands at four sites. Treatments included a complete harvest in 1-ha group selection openings, low-density dispersed retention, and either aggregated or dispersed high-density retention. Post-harvest stand density index and basal area were useful predictors of understory light. Mean and maximum understory light did not differ significantly between treatments with the same density where residual trees were retained in aggregated versus dispersed spatial patterns. However, the dispersed retention had lower minimum light levels when compared to the aggregated retention treatment. Aspect appeared to influence understory light more in dispersed treatments. At all light levels, the dominant sprout within clumps of redwood stump sprouts generally grew faster than dominant tanoak sprouts within tanoak sprout clumps. Differences in sprout height growth between aggregated and dispersed treatments were minimal. Stump size had a significant effect on redwood stump sprout height growth, with sprouts on the largest stumps growing approximately twice as quickly as sprouts on the smallest stumps. In the low density dispersed treatment, redwood sprouts outperformed tanoak sprouts by the greatest margin. Regeneration of redwood and tanoak was most rapid within group selection openings.

Long-term effects of single-tree selection on the frequency and population structure of root and butt rot in uneven-sized Norway spruce stands

Abstract The goal of this study was to assess the long-term effects of partial harvesting and supplementary soil scarification on the frequency of root and butt rot in managed uneven-sized Norway spruce stands. Frequency of rot and the population structure of the rot fungi were assessed on 1353 stumps after clear-cutting 21 years after a selection harvesting experiment. The initial experiment was comprised of three harvest strength (low, intermediate and high) of single-tree selection, removing approximately 25, 45 and 65% of the stand basal area. Uncut control plots were established at the same time. Supplementary soil scarification was applied in subplots within the single-tree selection plots, using a medium-sized excavator. After clear-cutting the stumps were analyzed with respect to rot caused by Heterobasidion parviporum, Armillaria spp., Stereum sanguinolentum as well as other rot fungi. Rot caused by Armillaria spp. was most common (8.6% of the stumps), while infection by H. parviporum (2.9%) or S. sanguinolentum (3.0%) was less frequent. The group “other rot” (5.4%) comprised 21 identified taxa, each occurring in 1–15 stumps. Significantly lower rot frequencies were found for the uncut control (16.3%) and intermediate harvest strength (15.7%), compared with low harvest strength (23.6%). A rot frequency of 21.0% was found in the high harvest strength. In two of three harvest strengths, the rot frequency was higher than for the uncut control. As the observed rot frequencies did not increase consistently with increasing harvest strength, the results do not completely support the initial expectations of increased rot after single-tree selection compared with the uncut control. However, since the probability of rot in individual stumps on plots treated with single-tree selection was significantly affected by the distance to the nearest strip road (H. parviporum) as well as dependent on the size of and distance to the nearest stump of trees cut during the experimental harvest (H. parviporum, S. sanguinolentum and total rot), it is evident that the single-tree selection harvesting was partially responsible for some of the observed rot. One of the selection criteria in the initial harvest was a sanitary removal of trees of poor vitality. Varying degrees of sanitation felling may therefore have offset the effects of new infections in wounds or spread of rot fungi through adjacent stumps. Supplementary soil scarification in small gaps of the residual stand had no significant effect on the frequency of rot, suggesting that such treatment may be used to facilitate regeneration in uneven-sized spruce stands on similar sites.

Norway spruce cone crops in uneven-aged stands in southern Finland: A case study

Norway spruce cone crops in individual trees from two seed ripening years 2012 and 2014 were studied. Data were collected from five stands in southern Finland, managed by single-tree selection harvests since the 1980s. The upper third of living crown of each individual tree was photographed for digital cone counting with image analysis. The average number of cones per tree for trees bearing any cones was 92 in 2014 and 66 in 2012. Highest cone numbers found per individual tree were 526 in the year 2014 and 364 in the year 2012. Of all trees studied, 55.5% produced cones during both years, 9.6% produced cones once and 34.9% did not produce cones in 2012 or 2014. The number of cones per tree in 2014 was positively correlated with tree diameter at breast height and the presence of cones (at least twenty) in that particular individual two years earlier and negatively correlated with local basal area. The quality of the seed crop in 2014 as determined in two of the stands was poor. Based on X-ray analyses, 44% of seeds were empty, 29% were damaged by insects feeding on seeds (Plemeliella abietina or Megastigmus strobilobius) and only 25% were full and capable of germination. The results have implications for management practices in uneven-aged Norway spruce stands. It is suggested that at each harvest entry, some large, prolific trees should be retained in order to increase the total number of seeds produced in a stand to enhance regeneration and the recruitment of new seedlings.

Silvicultural Prescriptions Influence the Proportion of High-Quality Hardwood Butt Logs Harvested over a Half-Century of Management

A long-term study on the Fernow Experimental Forest (FEF) in West Virginia provided an opportunity to test for differences in the timber quality of trees harvested from three silvicultural practices (HarvestType): diameter-limit, patch cutting, and single-tree selection. The effects of HarvestType and site index (SI) over time on the harvested proportion of trees with grade 1 butt logs within a compartment were tested using a repeated-measures linear mixed model. HarvestType*Time was a significant interaction (P = 0.0018) and SI had a slight positive effect (P = 0.0036). When examining the harvested proportion of grade 1 butt logs on a volume basis, the two terms were again significant (P = 0.0003 and P = 0.0208, respectively). The diameter-limit proportion of grade 1 butt logs consistently decreased while patch cutting and single-tree selection proportions consistently increase over time. Recent preharvest cruise data show a significantly greater residual proportion of grade 1 butt logs for single-tree selection compartments versus diameter-limit compartments on a per-tree and per-volume basis (P = 0.0013 and P < 0.0001, respectively). Results indicate that the production of grade 1 trees in diameter-limit harvests is not sustainable productivity wise whereas the single-tree selection harvests are. The sustainability of the production of grade 1 logs from patch cutting remains inconclusive.

Individual-level analysis of damage to residual trees after single-tree selection harvesting in northern Japanese mixedwood stands

Quantifying tree damage and mortality caused by single-tree selection harvesting is critical to understanding postharvest forest dynamics and management. In this study, we quantified the effects of tree size and species and the distance from residual trees to felled trees and skid trails on damage to residual trees and mortality in mixed coniferous–broadleaved stands of Hokkaido, northern Japan. Among the 4,961 trees that we studied, 373 (7.5 %) were damaged, and 148 of these trees (3.0 %) died during or immediately after logging. Hierarchical Bayesian modeling showed that the risk of damage to residual trees increased with increasing size of the felled trees and with increasing proximity to felled trees and skid trails. Smaller residual trees had the greatest risk of damage. Species differed in their susceptibility to damage; Abies sachalinensis (Fr. Schm.) Masters and Picea jezoensis (Sieb. et Zucc.) Carr. were the most susceptible species in our sample plots. Smaller damaged trees had the highest risk of mortality. The damaged trees that did not die at the time of logging had a higher risk of postharvest mortality than undamaged trees. Our results indicate that, to minimize logging-induced damage and mortality: (1) the spatial arrangement of skid trails should be optimized and fixed, (2) the risk of skidding damage should be considered before marking the trees to be harvested and choosing the felling direction, and (3) logging operators should be instructed to avoid damaging small trees, especially those of the species that are most susceptible to damage.

Long-term responses of disturbance-associated birds after different timber harvests

Timber harvest provides favorable habitat for many species of shrub-dependent birds. Because of historical dominance, effect of clearcutting on early successional birds has been widely studied, but less information is available on alternatives such as shelterwood and group selection, which have become a more dominant means of regenerating pines (Pinus spp.) on federal lands of the southeastern US. We compared detection of 12 species of early successional forest birds prior to harvest and at various intervals for 16years after harvest in stands subjected to clearcutting, shelterwood, single-tree selection, and group-selection harvests. We also compared detection rates of these species between harvested and unharvested control stands. Detection rate for all early successional species combined peaked 5years after harvest and was greatest in clearcuts 5–12years after harvest. Clearcuts retained some species for longer periods than other treatments. Hooded warbler (Setophaga citrine) and Kentucky warbler (Oporornis formosus) benefitted more from partial harvesting than clearcutting; partially harvested areas had increased understory shrub abundance but retained overstory trees. Detections of many species were lower in group selection stands than other harvested treatments, likely because openings were too small for area-sensitive species. Due to the level of overstory removal, shelterwoods likely provided the closest alternative to clearcutting and retained all the species found in clearcuts; shelterwoods also provided habitat to species rare in clearcuts, including hooded and Kentucky warbler. In terms of presence and absence, regeneration methods other than clearcutting provided habitat for most early successional species, but densities of birds are likely lower. Thus, greater expanses of harvesting may be needed to sustain populations of some early successional birds at levels similar to those under even-aged systems that use clearcutting as the primary regeneration method.

Estimating catchment-scale annual soil loss in managed native eucalypt forests, Australia

Conservation of soil and water resources is one of the key criteria underpinning sustainable forest management. While soil and water resources are important determinants of forest productivity, without appropriate assessment of soil erosion risk and the application of best management practices (BMPs), some forest management activities can adversely affect hillslope erosion rates with detrimental consequences for aquatic environments and downstream water users. In the multiple-use native eucalypt forests of New South Wales (NSW), Australia, hazard matrix tables are currently used to identify soil erosion risk based upon rainfall erosivity, soil regolith stability and slope classes at the compartment scale prior to undertaking forestry activities. Resultant “inherent hazard levels” (IHLs) direct the BMPs to be used, such as riparian buffer widths, during harvesting and roading operations. The IHL model, being an ordinal classification system, only provides a relative indication of erosion potential without any quantitative estimate of possible post-harvest erosion rates. To potentially better identify erosion risk and quantify likely soil erosion under a range of forest management and climatic scenarios at the hillslope and/or catchment scale, in this paper we utilised an alternative approach by modelling soil erosion using the empirically-derived Revised Universal Soil Loss Equation in combination with a GIS-based spatially distributed raster analysis. In four case study catchments in Kangaroo River State forest, two of which were subjected to single-tree selection harvesting operations, mean annual changes in soil loss were estimated at a grid cell level. Potential differences in soil loss estimates were assessed before, during and after selective logging. Vegetation cover and soil samples were recorded in a 500×1000m rectangular network laid out across the catchments. Slope gradient was found to contribute substantially to the spatial variability of soil loss estimation across the catchments. However, between-year differences demonstrate that the highest estimated annual rates of soil loss occurred on steep hillslopes when high levels of rainfall were recorded, while the values on those same areas remained considerably lower during low rainfall periods. The major effect of the rainfall component in generating soil erosion overshadows the modest impacts of selective logging operations.

Effects of single-tree selection harvesting on hymenopteran and saproxylic insect assemblages in the canopy and understory of northern temperate forests

Insects respond to changes in microhabitat caused by canopy disturbance, and thus can be used to examine the ecological impacts of harvesting. Single-tree selection harvesting is the most common silvicultural system used to emulate local small-scale natural disturbance and maintain uneven-aged forest structure in temperate forests. Here, we test for differences in richness, abundance, and composition of hymenopteran and saproxylic insect assemblages at four different taxon levels (selected insect orders; and all hymenopteran families, and braconid subfamilies and morphospecies) between the canopy and understory of unharvested and single-tree selection harvested sites in a northern temperate forest from central Canada. Harvesting had no effect on insect assemblage richness, composition or abundance at the three highest taxon levels (order, family and subfamily). Similarly, richness and abundance at the lowest-taxon level (braconid morphospecies) were similar, although composition differed slightly between unharvested and harvested stands. Insect assemblages were vertically stratified, with generally higher abundance (for Diptera, Hymenoptera, some hymenopteran families and braconid subfamilies) and richness (for braconid morphospecies) in the understory than the canopy. In particular, composition of the braconid morphospecies assemblage showed relatively low similarity between the understory and canopy. Single-tree selection harvesting appears to influence wood-associated insect taxa only subtly through small changes in community composition at the lowest taxon level, and thus is recommended as a conservative approach for managing these northern temperate forests.

Effects of single-tree selection harvesting on Rose-breasted Grosbeak (Pheucticus leudovicianus) demography in a northern hardwood forest

Single-tree selection harvesting is frequently used in the tolerant hardwood forests of North America, but little is known about how it affects the reproductive success of migratory songbirds. Many songbirds that breed in tolerant hardwoods, including the Rose-breasted Grosbeak (Pheucticus leudovicianus) are experiencing population declines across their breeding ranges. We studied habitat characteristics and reproductive success of Rose-breasted Grosbeaks in stands harvested 0–5, 16–20, and 21–25years previously and in reference stands (un-harvested for >50years) in Algonquin Provincial Park, Ontario, Canada (n=3 per age class). Recently harvested stands had higher cover from regenerative growth and lower sapling, understory, and canopy cover than other treatments, whereas reference stands had higher basal area and sapling cover. Pairing success was significantly lower in the reference stands than in all other post-harvest treatments, and the number of fledglings per successful nest was significantly lower in the reference stands than in the 0–5years post-harvest stands. Density and population growth rate were significantly positively correlated, suggesting that density may be an adequate indicator of habitat quality for Rose-breasted Grosbeaks in forested landscapes. Older males were present at higher densities, initiated their nests earlier, and produced significantly more fledglings per nest than younger males in all treatments. Habitat characteristics did not differ significantly between nests with second-year and after-second-year males, suggesting greater reproductive output of older males was likely due to experience rather than monopolization of better quality territories. We concluded that single-tree selection harvesting was beneficial to Rose-breasted Grosbeaks in our predominantly forested study area. Population growth rates were below replacement levels in the 21–25 years post-harvest and reference treatments, but populations were stable in the younger regenerating stands. Thus, in a continuously forested landscape this species’ declines are probably not attributable to single-tree selection harvesting.

Decomposing small-scale structural complexity in even- and uneven-sized Norway spruce-dominated forests in southern Finland

Summary Management targeting increased structural complexity requires not only targets but also mechanisms by which to create those target structures. We identified the most influential structural attributes and spatially explicit metrics for small-scale structural complexity using multiple linear regression at the beginning, end and over a 15-year period in two Norway spruce-dominated stands in southern Finland. Both stands had plots that exhibited an even-sized (ES) structure created through low thinnings and plots that exhibited an uneven-sized (UES) structure perpetuated through single-tree selection harvests. For both structure types, best models for structural complexity used a combination of non-spatial structural and/or compositional attributes and spatially explicit metrics that included the variation in tree size, tree size differentiation, tree density, stand basal area and spatial aggregation. Structural complexity in the ES structure type was mostly a function of tree size differentiation, whereas stand basal area and tree size differentiation were the most influential in the UES structure type. A conceptual model is presented to illustrate how spatial heterogeneity relates differently to small-scale structural complexity, which could be enhanced in ES structure types by increasing variation in size differentiation and in UES structure types by increasing variation in tree abundance.

Age‐specific response of a migratory bird to an experimental alteration of its habitat

1. Recruitment, i.e. the influx of new breeding individuals into a population, is an important demographic parameter, especially in species with a short life span. Few studies have measured this parameter in solitary-breeding animal populations even though it may yield critical information on habitat suitability and functional connectivity. 2. Using a before-after, control-impact pairs (BACIP) experimental design, we measured: (i) the return rate and apparent survival rate of individually marked territorial males of a neotropical migrant bird species, the Ovenbird Seiurus aurocapilla Linnaeus and (ii) the age-specific recruitment rate. Study plots (n = 10) were paired: one was treated through single-tree selection harvesting (30-40% basal area removal) and the other acted as a control. We hypothesized that experienced males would out-compete inexperienced ones and tend to avoid settling in lower-quality, treated stands. 3. In the first year post-harvest, the mean density of territorial males was significantly lower in treated plots (-41%) than in controls and the difference remained relatively stable thereafter. This lower density mainly reflected a lower recruitment rate compared to controls (17.9 vs. 49.0% of males present), itself driven by a lower recruitment rate of experienced males (2.8 vs. 22.8%). Return rate was similar between controls and treated plots in the first year post-harvest (59 vs. 55%, respectively) but it decreased in treated plots during the second (-15.8% relative to controls) and third (-12.7%) year post-harvest. The trend was even stronger when considering only experienced males. The treatment was followed by a major expansion in mean territory size in treated plots (+49% relative to controls, 3rd year post-treatment). 4. Neither apparent survival rate nor recruitment rate varied as predicted. There was a strong year effect but no treatment effect on apparent survival rate, whereas male recruitment patterns were both year- and age-specific. Three years post-harvest, recruitment rate was sufficient to fill most territory vacancies in treated plots, due mainly to first-time breeders. 5. To our knowledge, this is the first study documenting the effects of experimental habitat alteration on recruitment rate in a songbird species using a BACI design. The response of this male subpopulation highlights the influence of recruitment on the density of open populations of solitary-nesting birds and age-specific patterns in the response of individuals to habitat alterations.

Short-term demographic response of an old forest specialist to experimental selection harvesting

The brown creeper (Certhia americana) was recently identified as one of the forest bird species most sensitive to partial harvesting in North America. However, the processes underlying this sensitivity are poorly known. In this study, we quantified the immediate, post-treatment demographic response of this species to experimental selection harvesting in plots of northern hardwood forest in northwestern New Brunswick, Canada. We mapped individual detections and nest locations in 5 pairs (1 control and 1 treatment) of 25-ha plots in the first 2 y after single-tree selection harvesting. Linear mixed models with site and landscape context as random effects showed a significant negative effect of treatment on nest density and seasonal reproductive success. The density of large-diameter trees (≥ 30 cm dbh) was significantly lower in treated plots than in controls (mean: 77 versus 112 stems-ha−1), whereas the density of potential nesting substrates (snags with peeling bark) did not decrease significantly following treatment. Hence, the density of suitable foraging substrates may represent a limiting factor for both nest density and reproductive success, and partial harvesting may not be compatible with the persistence of breeding populations of brown creeper. Patches of untreated forest should be maintained in managed forest landscapes at all times for this and other taxa requiring old forest conditions.