Planted Conifer Seedlings Research Articles

Trap catch data are poor predictors of damage caused by pine weevil (Hylobius abietis) to conifer seedlings

Damage to planted conifer seedlings caused by the pine weevil Hylobius abietis (L.) is a severe and persistent threat to successful forest regeneration in Europe. Various countermeasures are available, which vary in effectiveness, costs and environmental impact, but none are ideal for all situations. Therefore, there is strong interest in robust assessments of damage risks, as they would enable more cost-effective and environmentally friendly forest pest management. It has been suggested that numbers of adult pine weevils caught in host-odour baited traps placed in regeneration sites may be valuable in such risk assessments. However, published studies provide at most weak support for the hypothesis that trap catch data provide adequate predictions of damage. Therefore, we conducted a two-year field study, designed to determine the relationship between weevil trap catch and subsequent damage at 10 regeneration sites in central Sweden. Site factors that might influence pine weevil feeding on seedlings were recorded and used as explanatory variables in the analysis. Stoniness was the only site factor identified as having a significant effect; damage mainly increased with increases in stoniness. No significant correlation was detected between damage to planted conifer seedlings and numbers of pine weevils trapped in the same locations. We suggest that this lack of correlation between weevil numbers and damage is due to planted seedlings only constituting a minor part of the weeviĺs food intake and considerable between-site variation in availability of food sources other than seedlings. Therefore, assessment of pine weevil numbers appears unlikely to be useful for predicting damage risk at specific regeneration sites.

Planted seedling survival in a post-wildfire landscape: From experimental planting to predictive probabilistic surfaces

Across the southwestern United States, high-severity wildfire is causing increasingly large areas of tree mortality and removing the seed sources required for the natural regeneration of these formerly conifer-dominated landscapes. Planting tree seedlings can accelerate reforestation, but in the semi-arid southwestern US, the survival of planted conifer seedlings is typically low. Our research examined how post-fire planting success is influenced by climate, topographic, biotic, and microclimate factors. We present data on a seedling planting experiment within the footprint of the 2011 Las Conchas Fire in northern New Mexico. We planted 768 tree seedlings of four species: ponderosa pine (Pinus ponderosa), piñon (P. edulis), southwestern white pine (P. strobiformis), and Douglas-fir (Pseudotsuga menziesii) in an area burned at high-severity and densely populated by New Mexico locust (Robinia neomexicana) and other shrub species. We established experimental plots stratified by aspect, either northerly or southerly, and cover, either planted under New Mexico locust or in the open, and collected topographical and microclimate measurements over three years. Mean survival over the 3-year period for all species in all treatments was 20%. Using microclimate variables and site-level topographical indices in a piecewise exponential model, we first determined how these factors influenced seedling survival of four conifer tree species, finding that topographical indices describing incoming solar radiation, variables related to vapor pressure deficit, i.e., seasonal maximums, and presence of New Mexico locust increased hazard for all species while variables related to shade, moisture availability, and slope reduced hazard. Following our planting experiment, an additional 1145 ponderosa pine seedlings, planted by USFS, were surveyed for survival and the topographical indices at their locations were recorded. Adding these seedlings' survival data to our experimentally planted ponderosa pine seedlings, we used boosted regression tree models to determine survival probability for ponderosa pine as a product of topographical indices, then extrapolated these findings to the wider landscape, producing a spatial projection of probabilistic seedling survival as a function of readily available topographical data, with a mean AUC value of 0.63. Both sets of analyses highlight the importance of landscape heterogeneity in shaping microclimatic environments and affecting seedling survival in a predictable manner, with areas receiving less solar radiation and more moisture promoting seedling survival. Our results demonstrate that by using fine-scale microtopography that shapes microclimatic environments, future plantings can increase conifer tree seedling survival in high-severity post-wildfire landscapes.

Field performance of sand-coated (Conniflex®) Norway spruce seedlings planted in mounds made by continuously advancing mounder and in undisturbed soil

The pine weevil (Hylobius abietis L.) is among the worst pests of newly planted conifer seedlings in Europe. EU regulations restrict the use of insecticides, the cost of mechanical site preparation (MSP) is high, and it has even been suggested that MSP should be abandoned due to social and environmental causes. The aim of this study was to investigate i) the field performance of Norway spruce (Picea abies (L.) Karst.) seedlings planted in mounds made by a continuously advancing mounder (CAM) and in undisturbed soil in southern Finland, and ii) how well the physical barrier (Conniflex® sand coating) prevented pine weevil damage compared to insecticide-applied and unprotected seedlings. The quality of CAM was generally at an acceptable level. After two growing seasons, mortality, mainly caused by pine weevils, was higher and growth lower in unprotected seedlings than in Conniflex-coated or insecticide-treated seedlings. Mortality was also higher and growth lower in undisturbed soil than in mounds. Even though the quality of soil preparation after CAM was quite good, planting Norway spruce seedlings without any protection could not guarantee a successful planting result (>1500 seedlings ha−1). Conniflex coating and insecticide treatment provided equal protection against serious pine weevil damage.

Post-fire early successional vegetation buffers surface microclimate and increases survival of planted conifer seedlings in the southwestern United States

Climate change and fire exclusion have increased the flammability of western United States forests, leading to forest cover loss when wildfires occur under severe weather conditions. Increasingly large high-severity burn patches limit natural regeneration because of dispersal distance, increasing the chance of conversion to non-forest. Post-fire planting can overcome dispersal limitations, yet warmer and drier post-fire conditions can still reduce survival. We examined how two shrub species with different structures affect below-shrub microclimate and survival rates of planted tree seedlings (Pinus ponderosa Lawson & C. Lawson, Pinus edulis Engelm., Pinus strobiformis Engelm., Pseudotsuga menziesii (Mirb.) Franco) following a high-severity fire in northern New Mexico. We expected that Gambel oak (Querus gambelii Nutt.), with its denser canopy, would buffer below-shrub climate causing higher survival rates of planted seedlings more than the lower canopy density New Mexico locust (Robinia neomexicana A. Gray). Seedlings planted under Gambel oak had survival rates 10% to 35% greater than those planted under New Mexico locust. Higher light availability beneath New Mexico locust corresponded to higher temperatures, lower humidity, and higher vapor pressure deficit, impacting the mortality of planted tree seedlings. These results indicate that by waiting for post-fire shrub establishment, selective use of shrubs can buffer microclimate and increase post-fire planting success in the southwestern United States.

Ground Cover—Biomass Functions for Early-Seral Vegetation

Vegetation biomass is commonly measured through destructive sampling, but this method is time-consuming and is not applicable for certain studies. Therefore, it is necessary to find reliable methods to estimate vegetation biomass indirectly. Quantification of early-seral vegetation biomass in reforested stands in the United States Pacific Northwest (PNW) is important as competition between the vegetation community and planted conifer seedlings can have important consequences on seedling performance. The goal of this study was to develop models to indirectly estimate early-seral vegetation biomass using vegetation cover, height, or a combination of the two for different growth habits (ferns, forbs, graminoids, brambles, and shrubs) and environments (wet and dry) in reforested timber stands in Western Oregon, USA. Six different linear and non-linear regression models were tested using cover or the product of cover and height as the only predicting variable, and two additional models tested the use of cover and height as independent variables. The models were developed for six different growth habits and two different environments. Generalized models tested the combination of all growth habits (total) and sites (pooled data set). Power models were used to estimate early-seral vegetation biomass for most of the growth habits, at both sites, and for the pooled data set. Furthermore, when power models were preferred, most of the growth habits used vegetation cover and height separately as predicting variables. Selecting generalized models for predicting early-seral vegetation biomass across different growth habits and environments is a good option and does not involve an important trade-off by losing accuracy and/or precision. The presented models offer an efficient and non-destructive method for foresters and scientists to estimate vegetation biomass from simple field or aerial measurement of cover and height. Depending on the objectives and availability of input data, users may select which model to apply.

Seedling, planting site and weather factors affecting the success of autumn plantings in Norway spruce and Scots pine seedlings

Due to the lack of labor and the mechanization of planting work, seedlings should be planted during the entire period of unfrozen soil, from early spring to late autumn. In experimental studies, it is difficult to investigate all the risk factors related to different planting windows. In Finland, the winter of 2015–2016 was harsh for seedlings. First temperatures were above zero, then they suddenly dropped to <−30 °C without any protective snow cover. These conditions offered a good opportunity to study the success of autumn plantings and clarify which factors best predict the field performance of autumn planted conifer seedlings. In the survey, 22 regeneration sites planted with Scots pine (Pinus sylvestris L.) and 71 with Norway spruce (Picea abies (L.) Karst.) seedlings were inventoried in the summer of 2016. Scots pine seedlings were more sensitive, and the regeneration result was good only in a few sites. With Norway spruce, the results were better although both good and poor results were found. For Norway spruce, we modeled the probability of severe damage and leader growth damage separately for summer (July and August), September and October plantings. The most important factors affecting the probability of damage was the quality of the planting and the planting spot as well as the soil type. If a planting hole was open or a seedling was planted in a planting spot other than a mineral-covered mound, the risk of damage was high. In fine and course textured soils, as well as medium coarse soils with a high risk of frost heaving, the probability of damage was also high. Low precipitation after planting and during the following spring also increased the probability of leader growth damage. Planting in the summer and early September exposed seedlings to leader growth damage, especially when the seedlings were planted in sites with a high risk of frost damage in autumn and spring. The results indicate that the planting of Scots pine seedlings in the autumn should be avoided. Norway spruce seedlings can be planted even in October when the work quality is good and suitable sites are selected for plantings.

Comparison of different site preparation techniques: quality of planting spots, seedling growth and pine weevil damage

In northern Europe, there are high risks of severe pine weevil (Hylobius abietis) damage to newly planted conifer seedlings. Site preparation is one of the most important measures for reducing these risks and as several studies have shown the damage is highly dependent on the amount of pure mineral soil around the seedlings. We investigated effects of three site preparation techniques: (1) disc trenching with a conventional Bracke T26, (2) MidiFlex unit and (3) soil inversion with a Karl Oskar unit on characteristics of the planting spots, growth and pine weevil damage and survival rates of untreated and insecticide treated planted Norway spruce (Picea abies) seedlings. All three site preparation techniques reduced pine weevil damage in comparison with no site preparation, and the proportion of spots with pure mineral soil they created was inversely related to the rate of mortality caused by pine weevil. The results indicate that the quality of the planting spots depends on the technique used. In areas where pine weevil is the major threat to seedling survival, the amount of mineral soil in the planting spots is the most important factor in order to protect the seedling from damage. Without site preparation most planting spots consisted of undisturbed humus. Generally, the Karl-Oskar created the most spots with pure mineral soil, but on very stony soils the Bracke T26 created more mineral soil spots than other methods. Site preparation is a valuable tool in order to improve survival in regeneration areas and it is of great importance to make the right choice of technique depending on the particular circumstances on the actual site.

Variable-density Retention Promotes Spatial Heterogeneity and Structural Complexity in a Douglas-fir/Tanoak Stand

1. Abstract After harvesting the merchantable conifers decades ago, many secondary forests in northern California regenerated naturally and are now fully stocked with low value hardwoods intermingled with conifers. Partial harvesting to reduce hardwood densities and release conifers is expected to enhance tree vigor and reduce risk of stand-replacing wildfire. Planting a new cohort of merchantable conifers in the understory would enhance structural complexity and future value. A flexible new forest restoration treatment called variable-density retention (VDR) was designed to achieve these objectives. Desirable trees can be kept regardless of their location while the new cohort of conifers is planted among existing trees or in gaps created by removal of patches of undesirable trees. At our study site in northern California, 20 × 20 m (0.04 ha) squares each received one of five treatments (gap, low-/medium-/high-density retention, and no cut). This created a mosaic of different densities. Planted conifer seedlings exhibited variable growth rates. Different stand variables were associated with growth of seedlings of the native coast Douglas-fir ( Pseudotsugamenziesii var.menziesii ) versus coast redwood ( Sequoia sempervirens ) planted outside its natural range. We found no correlation between point counts of overstory basal area and either leaf area index or understory light at each seedling. The VDR system promoted heterogeneity in the spatial pattern of tree locations, restored conifer dominance, and enhanced structural complexity by introducing a new cohort of trees growing at different rates. 3. Keywords: Forest Restoration; Notholithocarpusdensiflorus ; Pseudotsugamenziesii ; Redwood; Sequoia sempervirens ; Variable-Density Thinning; Variable Retention

Antifeedants Produced by Bacteria Associated with the Gut of the Pine Weevil Hylobius abietis

The pine weevil, Hylobius abietis, is a severe forest pest insect as it feeds on newly planted conifer seedlings. To identify and develop an antifeedant could be one step towards the protection of seedlings from feeding damage by the pine weevil. With the aim to trace the origin of the antifeedants previously found in feces of the pine weevil, we investigated the culturable bacteria associated with the gut and identified the volatiles they produced. Bacterial isolates were identified by 16S ribosomal RNA gene analysis. The volatile emissions of selected bacteria, cultivated on NB media or on the grated phloem of Scots pine twigs dispersed in water, were collected and analyzed by solid-phase microextraction gas chromatography-mass spectrometry. The bacterial isolates released a variety of compounds, among others 2-methoxyphenol, 2-phenylethanol, 3-methyl-1-butanol, 1-octen-3-ol, 3-octanone, dimethyl disulfide, and dimethyl trisulfide. A strong antifeedant effect was observed by 2-phenylethanol, which could thus be a good candidate for use to protect planted conifer seedlings against feeding damage caused by H. abietis.

Effects of planting time on pine weevil (Hylobius abietis) damage to Norway spruce seedlings

ABSTRACTFeeding by pine weevil (Hylobius abietis L.) causes severe damage to newly planted conifer seedlings in most parts of Scandinavia. We investigated the effect of planting time and insecticide treatment on pine weevil damage and seedling growth. The main objective was to study if planting in early autumn on fresh clear-cuts would promote seedling establishment and reduce the amount of damage caused by pine weevil the following season. The experiment was conducted in southern Sweden and in south-eastern Norway with an identical experimental design at three sites in each country. On each site, Norway spruce seedlings with or without insecticide treatment were planted at four different planting times: August, September, November and May the following year. In Sweden, the proportion of untreated seedlings that were killed by pine weevils was reduced when seedlings were planted at the earliest time (August/September) compared to late planting in November, or May the following year. This pattern was not found in Norway. The average length of leading shoot, diameter growth and biomass were clearly benefited by planting in August in both countries. Insecticide treatment decreased the number of seedlings killed or severely damaged in both Norway and Sweden.

Chemodiversity and biodiversity of fungi associated with the pine weevil Hylobius abietis

The pine weevil Hylobius abietis is a severe pest of conifer seedlings in reforestation areas. Weevils lay eggs in the root bark or in the soil near roots of recently dead trees and cover the eggs with frass (feces combined with chewed bark), possibly to avoid conspecific egg predation. The aim of the present investigation focused on isolation, identification, and volatile production of fungi from pine-weevil feces and frass. Fungi were isolated from weevil frass and feces separately, followed by identification based on ITS sequencing. Fifty-nine isolates belonging to the genera Penicillium, Ophiostoma, Mucor, Leptographium, Eucasphaeria, Rhizosphaera, Debaryomyces, and Candida were identified. Volatile organic compounds (VOCs) produced by the fungal community and fungal isolates cultured on weevil-frass broth were identified by SPME-GCMS. Major VOCs emitted from the fungal community and pure isolates were species- and strain specific and included isopentylalcohol, styrene, 3-octanone, 6-protoilludene, methyl salicylate, 3-methylanisole, 2-methoxyphenol, and phenol. Some of these are known to influence the orientation of pine weevils when tested among highly attractive newly planted conifer seedlings.

The structure of feeding behavior in a phytophagous insect (Hylobius abietis)

AbstractAnalysis of the feeding behavior of animals using such a high temporal resolution that meals can be defined may improve our understanding of the mechanisms regulating feeding. Meals can be distinguished in an ethologically meaningful manner by using the ‘meal criterion’, the shortest non‐feeding interval between feeding bouts recognized as meals. However, such a criterion has only been determined for a few insect species. Applying a recent method developed for assessing meal criteria for vertebrates, we determined the meal criterion for Hylobius abietis (L.) (Coleoptera: Curculionidae) based on data from video recordings of single individuals feeding on seedlings of Norway spruce, Picea abies (L.) Karst. (Pinaceae). The pine weevil is an economically important pest insect, because it feeds on the stem bark of planted conifer seedlings. Weevils had 4–5 meals per day. Each meal lasted about 24 min during which about 13 mm2 of bark per meal were removed. Females had longer total meal durations and longer non‐feeding intervals within meals than males. Girdling seedlings did not affect the weevils' feeding properties. The size of meals was significantly correlated with the duration of non‐feeding intervals before and after them. This study is one of few describing the feeding behavior of an insect at a temporal resolution that allows individual meals to be distinguished. With more meal‐related data from insects available, differences in meal properties may be interpreted based on phylogeny, ecology, and physiology. Our results may also assist in the setup and interpretation of studies of plant‐insect interactions, and facilitate the evaluation and development of methods to protect plants against herbivores.

Potential impact of the leaf-cutting ant Acromyrmex lobicornis on conifer plantations in northern Patagonia, Argentina

1 The economic losses associated with crop damage by invasive pests can be minimized by recognizing their potential impact before they spread into new areas or crops. 2 We experimentally evaluated the preferences of the leaf-cutting ant Acromyrmex lobicornis (Hymenoptera: Formicidae) for the most common conifer species commercially planted in northern Patagonia, Argentina. The areas of potential forest interest in this region and the geographical range of this ant overlap. We performed field preference tests and monitored the level of ant herbivory on planted conifer seedlings next to nests. 3 Acromyrmex lobicornis preferred some conifer species and avoided foraging on others. Pseudotsuga menziesii and Austrocedrus chilensis were the less preferred species, Pinus ponderosa and Pinus contorta were the most preferred by A. lobicornis. 4 The item mostly selected by ants was young needles from P. contorta. This species was also the pine mostly defoliated. Seedlings without ant-exclusion showed a mean±SE of 60±5% defoliation during the sampling period. Pinus ponderosa was less defoliated; control seedlings showed a mean±SE of 8.5±1% of leaf damage in the sampling period. 5 The present study shows how the use of simple field tests of leaf-cutting ant preferences could allow an improved selection of appropriate conifer species for future plantations in areas where leaf-cutting ants are present.

Cues For Shelter Use in a Phytophagous Insect

Many insects spend a large proportion of their life inactive, often hiding in shelters. The presence of shelters may, therefore, influence where insects feed. This study examines stimuli affecting the use of shelters by adults of the pine weevil, Hylobius abietis (L.) (Coleoptera, Curculionidae). This species is an economically important forest pest in Europe since the adults feed on the stem bark of newly planted conifer seedlings. When there are hiding or burrowing places present in close proximity to a seedling, pine weevils may hide there and repeatedly return to feed on the same seedling. Experiments were conducted in a laboratory arena with above-ground or below-ground shelters and in the presence or absence of wind. Pine weevils were highly attracted to shelters both above and below ground. Weevils in shelters were often observed assuming a characteristic resting posture. Experiments with opaque and transparent shelters showed that visual stimuli are used for orientation towards shelters and also increase the probability of an individual remaining in a shelter. The presence of wind increased the weevils' propensity to use shelters both above and below ground. The present study indicates that shelters have a major influence on the behavior of the pine weevil and possible implications of the results are discussed.

Structure–Activity Relationships of Benzoic Acid Derivatives as Antifeedants for the Pine Weevil, Hylobius abietis

Aromatic organic compounds found in the feces of the pine weevil, Hylobius abietis (L.) (Coleoptera: Curculionidae), have been shown to deter feeding behavior in this species, which is a serious pest of planted conifer seedlings in Europe. We evaluated 55 benzoic acid derivatives and a few homologs as antifeedants for H. abietis. Structure-activity relationships were identified by bioassaying related compounds obtained by rational syntheses of functional group analogs and structural isomers. We identified five main criteria of efficiency as antifeedants among the benzoic acid derivatives. By predicting optimal structures for H. abietis antifeedants, we attempted to find a commercial antifeedant to protect conifer seedlings against damage by H. abietis in regenerating forests. New, highly effective antifeedants are methyl 2,4-dimethoxybenzoate, isopropyl 2,4-dimethoxybenzoate, methyl 2-hydroxy-3-methoxybenzoate, methyl (3,5-dimethoxyphenyl)acetate, and methyl (2,5-dimethoxyphenyl)acetate. Of these, methyl 2,4-dimethoxybenzoate and isopropyl 2,4-dimethoxybenzoate have the highest antifeedant indices of all substances tested and are the best candidates for practical applications in order to protect planted seedlings in the field.

Antifeedants in the Feces of the Pine Weevil Hylobius abietis: Identification and Biological Activity

Egg-laying females of the pine weevil, Hylobius abietis (L.), regularly deposit feces adjacent to each egg. Egg cavities are gnawed in the bark of roots of recently dead conifer trees. After egg deposition, the cavity is sealed by feces and a plug of bark fragments. Root bark containing egg cavities with feces is avoided as food by pine weevils, which indicates the presence of natural antifeedants. Here we present the first results of the isolation and chemical analyses of antifeedant compounds in the feces of H. abietis. In feeding bioassays, methanol extracts of the feces revealed strong antifeedant properties. Methanol extracts were fractionated by medium-pressure liquid chromatography and the antifeedant effects were mainly found in the fractions of highest polarity. Volatile compounds in the active fractions were identified by gas chromatography-mass spectrometry (GC-MS) and the nonvolatile compounds were characterized by pyrolysis-GC-MS. Based on mass spectra, a number of compounds with various chemical structures were selected to be tested for their antifeedant properties. Antifeedant effects were found among compounds apparently originating from lignin: e.g., a methylanisol, guaiacol, veratrol, dihydroxybenzenes, and dihydroconiferyl alcohol. A weak effect by fatty acid derivatives was found. The types of naturally occurring antifeedant compounds identified in this study may become useful for the protection of planted conifer seedlings against damage by H. abietis.

Height growth of planted conifer seedlings in relation to solar radiation and position in Scots pine shelterwood

Seedlings of different provenances of Scots pine ( Pinus sylvestris L.), lodgepole pine ( Pinus contorta Dougl., var. latifolia Engelm.) and Norway spruce ( Picea abies (L.) Karst.) were planted in three Scots pine shelterwoods (125, 65 and 43 stems ha −1) and a clear-cut, all in northern Sweden. The sites were mounded and planting took place during 2 consecutive years (1988 and 1989). The solar radiation experienced by the individual seedlings was determined using a simulation model. Height development of the seedlings was examined during their first 6 years after planting. During the final 3 years of the study, height growth of Norway spruce was relatively poor, both in the shelterwoods and the clear-cut area. Height growth of lodgepole pine was significantly greater than that of Scots pine, both in the shelterwoods and the clear-cut. In contrast to Norway spruce, Scots pine and lodgepole pine displayed significantly greater height growth in the clear-cut than in the shelterwoods. For all three species in the shelterwoods, regression analyses showed that height growth was more strongly correlated with the distance to the nearest tree than with the amount of radiation reaching the ground, i.e. growth was reduced in the vicinity of shelter trees. Therefore, we conclude that the significant reduction in height growth of seedlings of Scots pine and lodgepole pine in Scots pine shelterwoods was partially caused by factors associated with the distance to the nearest shelter tree. Because the substrate was a nitrogen-poor sandy soil, we suggest that root competition for mineral nutrients, especially nitrogen, accounts for the reduction in height growth.

Extra Food Supply Decreases Damage by the Pine Weevil Hylobius abietis

It has been suggested that reduced damage by the pine weevil ( Hylobius abietis ) under shelter trees might result from more food being available under shelter trees than on clear-cuttings. The shelter trees provide an extra supply of bark on branches and roots. Moreover, shelter trees favour some species in the ground vegetation (e.g. bilberry, Vaccinium myrtillus ) that could be used as food by the weevil. Two similarly designed field experiments, studied whether the amount of pine weevil feeding on planted conifer seedlings was affected by the availability of other food sources. In the first experiment, fresh pine branches were placed weekly on the ground for 6 weeks on a fresh clear-cutting in southern Sweden. This significantly reduced the amount of feeding on seedlings in treated 20 2 20 m plots. In the second experiment, damage tended to increase after mechanical removal of field vegetation (mainly bilberry), but the effect was not statistically significant. In conclusion, extra food in the form of coniferous bark could relieve seedlings from pine weevil damage; however, any effect of this kind due to the presence of field-layer vegetation remains to be demonstrated. Finally, there may be long-term population effects because of the extra food that the shelter trees provide for the reproductive weevils.

Predation on Pinus sylvestris seeds and juvenile seedlings in Swedish boreal forest in relation to stand disturbance by logging

Summary 1. Forest management involving live tree retention and natural regeneration after cutting is currently increasing in boreal areas. This calls for further analysis of the optimal conditions for seedling establishment from seed following stand disturbances due to logging. 2. We studied post‐dispersal predation on seeds and juvenile seedlings of Pinus sylvestris over 3 years in 32 north Swedish boreal forest stands with different levels of stand disturbance by logging. The aims were to identify the most important predator species and to quantify the damage inflicted upon seeds and seedlings in relation to disturbance. 3. In most stands and years, seed predation resulted in &lt; 20% seed mortality, although occasionally it reached 60%. Predation on juvenile seedlings ranged from 5% to 100%, with &gt; 70% mortality in 10 cases and &lt; 30% in 44 cases (of a total of 79 observations). 4. The most important seed predators were the carabids Pterostichus oblongopunctatus and Calathus micropterus, and seed predation was correlated with the number of seed‐eating carabids caught in pitfall traps. Microtine rodents caused high damage levels only on a single occasion. 5. Logging affected both catches of carabids and seed predation levels, but the relationship between tree stand density and predation was not linear and, generally, seed predation decreased in the order shelterwood &gt; unlogged forest &gt; clear‐cut. 6. The most important predator on juvenile seedlings was the slug Arion subfuscus, which attacked seedlings during the first weeks after germination. Pitfall trap catches of Hylobius abietis, which commonly damage planted (1–3‐year‐old) conifer seedlings, were not related to the levels of seedling predation. 7. Seedling predation was negatively related to stand disturbance, with the highest predation levels by slugs in unlogged forests and the lowest in clear‐cuts. Seedling predation was higher in wet than in dry summers, probably because slugs are moisture‐limited. 8. There was a large between‐site variation in both seed and seedling predation, but predation was not strongly related to forest site types. The fact that predation was strongly affected by logging operations indicates that there may be opportunities to reduce damage through modification of the silvicultural practices.

Root-zone soil temperature variation associated with microsite characteristics in high-elevation forest openings in the interior of British Columbia

Low soil temperatures have been suggested as a factor contributing to poor rooting of planted conifer seedlings and hence a cause for failure of some high-elevation reforestation efforts. Few studies have attempted to document soil temperature variation and its causal factors in post-logged, high-elevation openings during the growing season. A field survey of afternoon soil temperature (at a depth of −10 cm from the mineral soil surface) was conducted in six high-elevation clear-cuts located in the Engelmann Spruce-Subalpine Fir (ESSF) biogeoclimatic zone in central British Columbia, Canada. On a clear summer day, a difference of 8°C in afternoon soil temperatures was measured between the warmest microsites (bare mineral soil, 17.6 ± 2.5°C) and the coolest microsites (covered by forest floor and vegetation, 9.3 ± 0.7°C). Heavily covered microsites showed little diurnal or spot-to-spot (microsite) variation in soil temperature. Conversely, microsites with little surface cover exhibited the greatest spatial and temporal variability in soil temperature. Variation in afternoon root-zone soil temperature ( T) was most strongly associated with the combination of thickness of duff (forest floor) ( D), cumulative % vegetation cover ( C), and % soil moisture ( M). Comprised of these three microsite attributes, a multiple regression model, T = 24.06 − [1.05(ln( C) + 1.64(ln( D)) + 1.38(ln( M))] ( R 2 + 0.73) was created which predicts high-elevation afternoon soil temperatures to within ±2.0°C. Multiple regression models including relative surface irradiance (as a percentage of above canopy light), cumulative % vegetation height, micro-slope and micro-aspect were less predictive. The relationship between afternoon soil temperature and each microsite attribute generally showed a strongly negative curvilinear pattern, described by double exponential decay functions. Microsites associated with suboptimally low afternoon soil temperatures (< 12°C) during the growing season were widespread (70 to 80% of the sampled areas) in the surveyed high-elevation openings.