Leader Browsing by Red and Roe Deer on Young Sitka Spruce Trees in Western Scotland. II. Effects on Growth and Tree Form

Some 2000 trees at 14 main sites in Glenbranter Forest, Argyll,were monitored during 1978–1990 for damage. Tree state(whether leaderless or with single or multiple leaders or trunks)and tree size were regularly recorded. Browsing of leaders depressed height increment by 5–10cm in the year of ocurrence compared with undamaged trees; therapid development of new leaders minimized the check in growth.Trees initially leaderless had equal height increment over ayear to trees initially with leaders if no damage occurred inthe year. At a subsidiary site where some trees were planted in smallexclosures, the trees protected from deer reached a safe heightafter five seasons of growth, unprotected trees reaching equalheight 1 year later. The girths attained when trees were 10–15 years old wereon average only slightly depressed by earlier browsing damageto leaders, reductions at most equalling one year's increment. Many trees became multi-trunked, there being a significant relationshipbetween the percentage incidence of multi-trunking and the numberof occurrences of leader damage. Unbrowsed trees mostly becamesingle-trunked. We judge that the present high incidence ofmulti-trunking (45 per cent in our 9–15 year-old stands)results largely from deer browsing.     

Plant diversity, population structure, and regeneration status in disturbed tropical forests in Assam, northeast India

We investigated the plant population structure and the phy-tosociological and regeneration status in two disturbed tropical forests in Assam Province, the Hojai Reserve Forest and Kumorakata Reserve Fo...     

Retention of aspen (Populus tremulae) at final cuttings - The effect of dead wood characteristics on saproxylic beetles

To preserve biodiversity in managed forest landscapes dead and living trees are retained at final cuttings. In the present study we evaluated the effect of these practices for saproxylic (wood-dependent) beetles inhabiting dead aspen trees (Populus tremulae). For saproxylic beetles, tree retention at final cuttings can be expected to be especially valuable for species adapted to sun-exposed dead wood, a substrate that only rarely occurs in well managed forest stands. Therefore, the current evaluation was conducted as a comparison of species richness, species density (number of species per sample), assemblage composition and occurrence of individual species between clear-cuts, where aspen trees were retained, and closed forest stands with aspen trees. The study was conducted in central Sweden and the beetles were sampled by sieving of bark from CWD (coarse woody debris) of aspen. There was no significant difference in rarefied species richness between forest and clear-cut sites. Species composition differed significantly between the two stand types. Generalized linear mixed-effects models predicted the species density to be 34% lower in CWD objects in forest sites than on clear-cuts. This pattern could partly be explained by differences in CWD diameter, decay class and bark types between the two stand types (clear-cut/forest). Stand type was a significant predictor of occurrence in individual CWD objects for 30% of analysed individual beetle species. For all species except one, the variable stand type predicted higher occurrence on clear-cuts than in forest stands. To conclude, our results demonstrate that retention of aspen on clear-cuts contributes to population recruitment of a different assemblage of species than CWD within stands.     

Micropropagation of adult birch trees: production and field performance

We compared the growth of trees produced by micropropagation from nodal stem sections or callus tissue of a 20-year-old silver birch (Betula pendula Roth) tree with that of seedlings; growth was monitored for 17 months in pots followed by six years in the field. Micropropagated trees from both nodal stem sections and callus tissue grew at a similar rate to seedling trees and no obvious mutant types were observed. However, micropropagated trees were more uniform in height and trunk girth than seedling trees and more than 80% flowered within three years of field planting, whereas only 39% of seedling trees flowered within this time. Micropropagated trees had less bark fissuring, a mature characteristic, than seedling trees.     

Incidence of Root and Butt Rot in Consecutive Rotations of Picea abies

The incidence of butt rot in two consecutive rotations of Norway spruce [Picea abies (L.) Karst.] in 28 permanent sample plots at four different sites in Denmark was evaluated. Incidence of butt rot was estimated by visual examination of stumps at final felling of the previous rotation and by examination of bore cores taken at the butt from a random sample of trees before first thinning of the subsequent rotation. There was no correlation between the incidence of butt rot at final felling of the previous rotation of Norway spruce and the incidence of butt rot at first thinning of the subsequent rotation of Norway spruce. The incidence of butt rot at final felling was between 19 and 100%, and at first thinning between 0 and 20%. The S-form of Heterobasidion annosum (Fr.) Bref. was the most commonly found decay-causing organism at all sites. Root systems of 28 trees without decay at stump height in the present rotation were excavated to estimate the incidence of root rot. Heterobasidion annosum was found in only one root. Resinicium bicolor (Alb. & Schw. ex Fr.) Parm. was found in 25% of the excavated root systems. The result of the study shows that the incidence of butt rot at first thinning of Norway spruce is not necessarily higher on sites where the previous rotation was heavily infected than on sites where infection in the previous rotation was low.     

Epidemiology of Armillaria root disease in Douglas‐fir plantations in the cedar‐hemlock zone of the southern interior of British Columbia

Results are presented from several studies on the epidemiology of Armillaria ostoyae in Douglas‐fir plantations in the interior cedar‐hemlock (ICH) biogeoclimatic zone of British Columbia. Two plantations were monitored for mortality by A. ostoyae and other agents for 35 years after establishment. In these and other plantations ranging in age from 7 to 32 years, one or more of the following factors were determined: source of inoculum, mode of spread and characteristics of lesions on roots of excavated trees; symptom expression in relation to tree age and damage to the root system and years from initial infection to death on trees killed by the fungus. Mortality from A. ostoyae began in both plantations about 5 years after planting, reaching 30% in one and 11% in the other after 35 years. The spatial pattern of mortality was similar to that reported from New Zealand, France and South Africa; however, the temporal pattern differed, beginning later and, instead of declining, continuing at a nearly constant rate to the present. To age 10, nearly all infections were initiated by rhizomorphs; as plantations aged, the proportion of infections occurring at root–root contacts increased. In seven plantations, in moist and wet subzones of the ICH, from 23 to 52% of Douglas‐firs had root lesions, with the higher incidences occurring on moist sites. The occurrence of aboveground symptoms, reduced leader growth and basal resinosis, was related to the percentage of root length colonized by A. ostoyae on trees with more than 30% of root length killed. Average time from infection to death increased from 1 to 2 years at age 6 to 22 years at age 33. The outlook for timber yield from Douglas‐fir plantations in the cedar‐hemlock zone is discussed. Management alternatives for reducing damage from A. ostoyae when regenerating sites are reviewed.     

Change of allometry between coarse root and shoot of Lodgepole pine (Pinus contorta DOUGL. ex. LOUD) along a stress gradient in the sub-boreal forest zone of British Columbia

Abstract

This transect study in 41–178 year-old stands of Lodgepole pine (Pinus contorta DOUGL. ex. LOUD.) in the southern boreal forest of British Columbia, Canada, analyses how site conditions modify the coarse root–shoot dynamics of trees. The allometric relationship between diameter growth of coarse roots and trunk is scrutinised for long-term site dependence, and short-term reactions to periodic climate conditions. Along a gradient from poor to rich sites, we analysed 54 trees. The sampling scheme provided two increment cores each from the three main roots and the shoot at breast height per tree. From the year-ring series, we calculated diameter time series for each shoot and each root. With these data, we show (1) that the trees’ coarse root diameter and shoot diameter are linearly related in a double-logarithmic coordinate system, thus representing constant allometry on the long run. Statistical analysis of these long-term trajectories reveals that (2) the relative allocation to coarse roots versus shoot is much higher on poor sites compared to rich sites. A closer look at the short-term reaction to stress events in the period from 1995 to 2000, where several dry years occurred, underpins that (3) a lack of water supply triggers biomass allocation in favour of coarse roots at the expense of shoot growth most pronouncedly on poor sites. Implications of this morphological plasticity for allometric theory, method development, tree and stand dynamics and carbon storage assessment are discussed.     

设施栽培条件下大石早生李授粉树配置距离初步研究

以日光温室内栽植的 4a生大石早生李为试材 ,分析了大石早生李结实能力与枝径、冠径、干径、树高、分枝数、离授粉树的距离的相关关系。结果表明 ,授粉树距离是影响结果数量的主要因素。根据回归方程可得出授粉品种配置的最佳距离。为大石早生李保护地栽培授粉品种的配置提供了参考依据     

Trees on farms in Bangladesh: 5. Growth of top- and root-pruned trees in wetland rice fields and yields of understory crops

Growth of trees and seasonal yields of understory crops were measured over a 5-year period for 4 crops grown under 17 tree species at 8 × 8 m spacing in wetland rice fields. All tree species grew well in rice fields, at rates comparable to their growth in forest plantations. Top and root pruning reduced average tree girths by up to 19% and average tree volumes by up to 41%, depending on intensity of pruning. The crops monitored were Oryza sativa, Triticum aestivum, Corchorus olotorius, and Lens culinaris. Crop yields under the trees averaged 93% of the corresponding yields outside the tree canopy. The most important factor affecting the yields of undercrops was tree size (height and/or girth). Differences among tree species and the interaction with species of undercrops were not significant after controlling for tree size. Pruning of roots and branches significantly improved crop yields under trees by amounts proportional to the intensity of root or top pruning. This revised version was published online in June 2006 with corrections to the Cover Date.     

What loggers leave behind: Impacts on big-leaf mahogany (Swietenia macrophylla) commercial populations and potential for post-logging recovery in the Brazilian Amazon

The sustainability of current harvest practices for high-value Meliaceae can be assessed by quantifying logging intensity and projecting growth and survival by post-logging populations over anticipated intervals between harvests. From 100%-area inventories of big-leaf mahogany (Swietenia macrophylla) covering 204 ha or more at eight logged and unlogged forest sites across southern Brazilian Amazonia, we report generally higher landscape-scale densities and smaller population-level mean diameters in eastern forests compared to western forests, where most commercial stocks survive. Density of trees ≥20 cm diameter varied by two orders of magnitude and peaked at 1.17 ha⁻¹. Size class frequency distributions appeared unimodal at two high-density sites, but were essentially amodal or flat elsewhere; diameter increment patterns indicate that populations were multi- or all-aged. At two high-density sites, conventional logging removed 93–95% of commercial trees (≥45 cm diameter at the time of logging), illegally eliminated 31–47% of sub-merchantable trees, and targeted trees as small as 20 cm diameter. Projected recovery by commercial stems during 30 years after conventional logging represented 9.9–37.5% of initial densities and was highly dependent on initial logging intensity and size class frequency distributions of commercial trees. We simulated post-logging recovery over the same period at all sites according to the 2003 regulatory framework for mahogany in Brazil, which raised the minimum diameter cutting limit to 60 cm and requires retention during the first harvest of 20% of commercial-sized trees. Recovery during 30 years ranged from approximately 0 to 31% over 20% retention densities at seven of eight sites. At only one site where sub-merchantable trees dominated the population did the simulated density of harvestable stems after 30 years exceed initial commercial densities. These results indicate that 80% harvest intensity will not be sustainable over multiple cutting cycles for most populations without silvicultural interventions ensuring establishment and long-term growth of artificial regeneration to augment depleted natural stocks, including repeated tending of outplanted seedlings. Without improved harvest protocols for mahogany in Brazil as explored in this paper, future commercial supplies of this species as well as other high-value tropical timbers are endangered. Rapid changes in the timber industry and land-use in the Amazon are also significant challenges to sustainable management of mahogany.     

Evaluation of unconstrained and constrained mathematical functions to model girth growth of rubber trees (Hevea brasiliensis) using young age measurements

No attempt has been made to date to model growth in girth of rubber tree (Hevea brasiliansis). We evaluated the few widely used growth functions to identify the most parsimonious and biologically reasonable model for describing the girth growth of young rubber trees based on an incomplete set of young age measurements. Monthly data for girth of immature trees (age 2 to 12 years) from two locations were subjected to modelling. Reparameterized, unconstrained and constrained growth functions of Richards (RM), Gompertz (GM) and the monomolecular model (MM) were fitted to data. Duration of growth was the constraint introduced. In the first stage, we attempted a population average (PA) model to capture the trend in growth. The best PA model wasfitted as a subject specific (SS) model. We used appropriate error variance-covariance structure to account for correlation due to repeated measurements over time. Unconstrained functions underestimated the asymptotic maximum that did not reflect the carrying capacity of the locations. Underestimations were attributed to the partial set of measurements made during the early growth phase of the trees. MM proved superior to RM and GM. In the random coefficient models, both Gf and G0 appeared to be influenced by tree level effects. Inclusion of diagonal definite positive matrix removed the correlation between random effects.The results were similar at both locations. In the overall assessment MM appeared as the candidate model for studying the girth-age relationships in Hevea trees. Based on the fitted model we conclude that, in Hevea trees, growth rate is maintained at maximum value at t0, then decreases until the final state at dG/dt ≥ 0, resulting in yield curve with no period of accelerating growth. One physiological explanation is that photosynthetic activity in Hevea trees decreases as girth increases and constructive metabolism is larger than destructive metabolism.     

Increasing rubber planting density to shade Imperata: a bioeconomic modelling approach

The profitability to smallholders of rubber production in Imperata infested areas of Indonesia was assessed using an existing bioeconomic model. An Imperata groundcover component was incorporated within the model as follows: tree girth = f(Imperata groundcover) = f(relative shading) = f(crown height, canopy width, tree spacing) = f(tree girth). The first two relationships represent extensions to the original model.Cumulative tree girth was predicted for rubber planting densities from 400 to 1000 stems/ha. At low tree planting rates, competition from Imperata restricts tree growth. At high tree planting rates, Imperata is controlled, but there are negative consequences from inter-tree competition. These two effects of higher planting rates counterbalanced, such that tree girth was approximately constant across the range of tree densities.Tree girth is a driving force in determining latex yield. Latex yield was translated into present value net economic returns within the model, by reference to prices and costs associated with rubber production in South Sumatra, Indonesia in 1995. Economic returns from planting 400 to 1000 trees/ha were calculated. Rubber growing by smallholders on Imperata infested land, was found to be profitable. Maximum profitability was obtained at 600 trees/ha. However, the sensitivity of net economic returns, with respect to tree density, was not great. This was due to the counterbalancing effects of changes in tree density.     

Observations on bark-stripping by red deer in a Picea sitchensis forest in Western Scotland over a 35-year period

The impact of bark-stripping by red deer on an 1825?ha plantation of Picea sitchensis is reported. Monitoring began in 1978 with initially 6500 trees at 37 sites; by 2014, only 10 sites remained due to felling. Sites became vulnerable to bark-stripping once the trees reached 7 years’ age, and from then until felling at age c. 45 years, incidence rates averaged 1% of the trees damaged yearly. Intense damage at a site in a year (>2% trees damaged) was often followed by intense damage next year, but, on average, 53% of sites were undamaged in a year. Many trees suffered repeat wounding, which reduced final impact by c. 30% compared to the theoretical impact calculated from annual damage and damage duration. The trees bark-stripped were on average smaller than plot mean girths once these means exceeded 20?cm; this had only a minor effect on the final impact since bark-stripped small trees had similar mortality to undamaged small trees. Most wounds (>90%) were small (<180?cm²) and healed quickly, so were unlikely to develop decay. Larger wounds never healed in less than 8 years, but the proportion healed increased progressively from 10 to 20 years after wounding.     

A thirteen‐year study on the impact of a severe canker disease of Corymbia calophylla,a keystone tree in Mediterranean‐type forests

Worldwide, forests and woodlands have shown progressive declines in health as a result of global environmental changes in combination with local anthropogenic drivers. This study examined the incidence and progression of a canker disease of marri (Corymbia calophylla) caused by the endemic fungal pathogen Quambalaria coyrecup at three paired forest and anthropogenically disturbed sites in the southwest of Western Australia over 13 years. At the time of plot establishment in 2001, cankers were present on trees at all six sites with 22.7% of the assessed trees cankered. By 2014, cankers had led to the death of 6.7% of the trees, and an additional 10.0% of the trees developed cankers during this time. A further 2.3% of trees died due to causes other than canker, resulting in a final figure of 65.0% of trees remaining alive and free of cankers for the duration of the survey period. Canker incidence was significantly greater on trees present at anthropogenically disturbed sites (along roadsides and in paddocks) than forest trees (35.3% increasing to 50.7%, 10.0% increasing to 14.7%, respectively). Trunk diameter at breast height, tree height and crown ratings were not correlated with canker presence. This long‐term study provides evidence of the increasing severity of this canker pathogen and the impact it is having on the survival of marri.     

Spatial distribution of dead wood and the occurrence of five saproxylic fungi in old-growth timberline spruce forests in northern Finland

Abstract

Adequate understanding of the factors that determine the establishment and survival of dead-wood-dependent species in natural forests is a prerequisite to the successful maintenance of these species in managed forests. This study investigated the factors affecting the occurrence of five wood-inhabiting polypores in old-growth timberline spruce forests in northern Finland, including the substrate availability and the spatial arrangement of large-diameter logs. The volume of coarse woody debris (CWD) varied significantly between the sites (range 15–30 m³ ha^?1), large-diameter logs comprising on average 35% of the total CWD volume. However, the within-site variation in CWD volume was 10–15 times larger than the between-site variation. The spatial distribution of large-diameter logs was aggregated or initially aggregated on four sites and random on one site, creating local patches of high CWD volume. An individual target species occurred on average on 8% of all large-diameter logs, and on 11% of optimal logs (as determined by the decay stage). The characteristics of the logs and stand variables explained partly the occurrence of the target species; furthermore, the mortality pattern of trees (stem breakage versus uprooting) and the presence of primary decomposers also significantly affected the occurrence of the target species. The results indicate that besides substrate availability and quality, local habitat factors and species interactions also play a role in the occurrence of wood-inhabiting fungi in boreal timberline forests.     

Tree-rings reflect the impact of climate change on Quercus ilex L. along a temperature gradient in Spain over the last 100 years

We analyzed tree rings over the past 100 years to understand the response of Quercus ilex L. to climate change at four different sites along a temperature gradient in a highly anthropogenically transformed ecosystem. To test the hypothesis of a climate change related decrease in productivity at warmer sites, we discuss the effect of historical management on the growth of forest stands and the spatio-temporal variability of growth in response to climate, analyzing departures from linearity in that relationship. We reconstructed stand history and investigated past growth trends using tree-rings. Then we used a dendroecological approach to study the regional, local and age-dependent response to climate, analyzing the relationship between precipitation and tree growth using non-linear mixed models. Tree rings reflected the origin of the studied landscape, mainly a simplification of an original closed forest and progressive canopy opening for agrosilvopastoral purposes after the mid 1800s. As expected, trees were principally responding to water availability, and regional growth (as expressed by the first principal component from the matrix of chronologies) was highly responsive to hydrological year precipitation (r = 0.7). In this water limited ecosystem, the response of growth to precipitation was asymptotic and independent of age, but variable in time. Maximum growth was variable at the different sites and the non-linear function of growth saturated (i.e. reached an asymptote) at temperature dependent site specific precipitation levels within the range considered in the region to lead a shift towards deciduous species dominated woodlands (around 600 mm, variable with mean temperature). Only trees at warmer sites showed symptoms of growth decline, most likely explained by water stress increase in the last decades affecting the highly transformed open (i.e. low competition) tree structure. Stands at colder locations did not show any negative growth trend and may benefit from the current increase in winter temperatures. Coinciding with the decrease in productivity, trees at warmer sites responded more to moisture availability, exhibited a slower response to precipitation and reached maximum growth at higher precipitation levels than trees at colder sites. This suggests that warmer stands are threatened by climate change. The non-linear response of growth to precipitation described is meaningful for different ecological applications and provides new insights in the way trees respond to climate.     

Should unthinned oak stands of advanced age (≥ 60 yr) be thinned?

ABSTRACT

Oaks (Quercus sp.) account for nearly one-third of the sawtimber harvest in Wisconsin. As trees age, their ability to respond to thinning is reduced; therefore, the objective of this study was to determine whether thinning previously unthinned oak stands of advanced age (≥ 60 yr) would achieve biological, financial, and operational objectives. During 2014, we conducted an inventory of 25 oak stands in northern Wisconsin. Fifteen received their first thinning 8–14 yr ago at ages 60–78 yr and 10 had never been thinned. Stand-level volume growth, logging costs, and net present values were estimated for each site. The age and site index of the thinned and unthinned sites were not significantly different (p > .10). Thinned and unthinned sites grew comparable net volumes per ha (5.09 and 5.90 m³, respectively); however, because this growth was concentrated on fewer trees, the trees on the thinned sites responded vigorously to thinning. As age at first thinning increased, growth response was reduced (p = .067); however, thinning still increased the growth of residual trees. Thinned sites had higher net present values compared to unthinned sites (p < .01) and logging costs were 10.6% lower (p = 0.06). Overall, for stands between 60 and 78 years old, thinning was beneficial financially, operationally, and biologically.     

Mycorrhizal associations in the rain forest of South Cameroon

Mycorrhizal associations of important tree species were investigated within the research area of the Tropenbos Cameroon Programme (TCP), situated on the western portion of the Atlantic Biafrean forest of south Cameroon. Ninety-seven tree species of economic, social, and ecological importance, and three lianas were selected in three sites that differed in altitude, soil clay content, and soil pH. In each site plots were laid out in undisturbed forest. In each plot, seedlings, saplings, juvenile, and mature trees were identified to species level and counted; girth at breast height measured and basal area calculated; root samples were taken and examined for mycorrhizal type and extent of mycorrhizal colonization.

All 100 species investigated were mycorrhizal. Tree of 74 species formed exclusively arbuscular mycorrhizas (AM); 23 trees and three Gnetum species formed ectomycorrhizas (ECM). Five of these ECM plants also harbored AM structures. Extent of mycorrhizal root colonization showed large differences for various AM trees; however, colonization of more than half of these trees was less than 25%. Colonization of ECM trees was often higher than 75%. The contribution of ECM trees to basal area varied between 19 and 35%. ECM trees often occurred in small to large clumps. In sustainable forest management plans, existing ECM forest clumps should be given special conservation value.     

Effect of tapping activity on the dynamics of radial growth of Hevea brasiliensis trees

Rubber tree (Hevea brasiliensis Müll. Arg.) radial growth dynamics were monitored with displacement sensors, together with latex production, to investigate three aspects of the dual production of latex and wood: (1) the usefulness of fine-scale dendrometric measurements as a physiological tool to detect water shortage through radial growth; (2) the dynamic aspects, both at the seasonal and at the multi-year scale, of the competition between latex and wood production; and (3) the spatial distribution of radial growth rates around the tapping cut. Radial growth of untapped control trees started with the onset of the rainy season and lasted until the onset of the dry season, ceasing completely during the driest period. Displacement sensors provided a sensitive means of detecting water shortage, with a clear correlation between diameter variations and changes in water availability (both daily evapotranspiration and monthly rainfall) over the whole annual cycle. However, the correlation was significantly disturbed in tapped trees. After resumption of tapping, the radial growth rate dropped sharply within two weeks and the effect persisted throughout the whole season, so that the cumulative growth of tapped trees was about half that of untapped trees, with the cumulative growth deficit reaching 80% for the period from mid-June to November. This long-known negative impact of tapping on growth was much stronger in the second year of tapping than in the first, whereas latex production increased significantly between the first and second year of tapping. The increased latex production, which could not be ascribed to climatic conditions, shows that the establishment of an artificial latex sink is a progressive, long-term process likely involving many aspects of metabolism. As expected, ethylene significantly increased latex production in both years; however, ethylene had no effect on the growth rates of tapped trees. Radial growth was differentially affected at different locations around the tapping cut, with growth rates significantly lower in the tapped panel than in the untapped panel, and higher above the cut than below the cut. Thus, caution is needed when deriving whole stem wood production from girth measurements at one location on the stem, especially from girth measurements made close to the tapping cut. This also provides new evidence for the location of the latex regeneration area in the tapped panel, below the cut.     

Damage by pine weevil Hylobius abietis to conifer seedlings after shelterwood removal

Abstract

Pine weevil (Hylobius abietis L.) damage to seedlings after overstorey removal was investigated in a survey study in six shelterwoods in the south–central part of Sweden. The shelterwoods predominantly consisted of Scots pine, except at one site where the shelter trees mainly consisted of Norway spruce. Before final cutting, 10 plots were laid out at each site and measurements of shelter trees and marked seedlings were taken. The seedlings were examined during the 2 years after final cutting. The study showed that removal of shelter trees increases the risk of severe damage by pine weevil and the variable that was most strongly correlated with the risk was the seedling root collar diameter. Both Scots pine and Norway spruce seedlings were severely damaged by pine weevil, and most of the feeding occurred during the first year after cutting. The amount of debarked area was significantly larger for Scots pine than for Norway spruce seedlings. Vitality (growth of the leading shoot before final cutting) of the seedlings also affected the probability of damage. Seedlings with high vitality were less damaged by pine weevil than seedlings with low vitality. For Scots pine the shelterwood density before final cutting was correlated to the intensity of pine weevil feeding after cutting. In conclusion, after the final cutting of a pine or spruce shelterwood, pine weevils will probably invade the area. To avoid serious damage, Norway spruce and Scots pine seedlings should have reached a diameter of at least 10–12 mm.