Scramble competition in the southern pine beetle, Dendroctonus frontalis

Abstract .1. The nature of intraspecific competition was investigated in the southern pine beetle, Dendroctonus frontalis , a highly destructive pest of pine forests in the southern U.S.A. Data were analysed from an observational study of naturally-attacked trees, and from field experiments where attack density was manipulated by adding different numbers of beetles to caged trees.
2. The effect of attack density on gallery construction, oviposition, brood survival, and the overall rate of increase was examined, and a flexible model of intraspecific competition used to classify the type of competition (contest or scramble) at different points in the life cycle.
3. The results of these analyses suggest that contest competition occurs during gallery construction and oviposition, in accord with previous work on D. frontalis . Strong scramble competition occurs later on in development, however, and the overall competitive process is better characterized as scramble competition, similar to other bark beetles. Trees with attack densities sufficiently high to produce significant competition are common in the field.     

Bird population in the pine and birch forests of Kungurskii Raion (Perm’; Krai) under anthropogenic load of various levels

In 1995—2006, the birds inhabiting the pine and birch forests as well as pine plantations were studied in and near the town of Kungur (Perm’ krai). The greatest faunal and biocenotic similarity of the bird populations was revealed in the pine forests in the town and raion, the lowest, in the birch forests. It was found that anthropogenic impact is the highest in the town birch forests, where it is seen in all studied parameters of ornitocenosis—density of bird population, species diversity and domination.     

Response of maritime pine (Pinus?pinaster Ait.) recruitment to fire severity and post-fire management in a coastal burned area in Galicia (NW Spain)

The short-term effects of fire severity and post-fire management on maritime pine recruitment were evaluated in a mature serotinous pine stand in a coastal area of Galicia (NW Spain) burned by a wildfire occurred in the summer of 2001. Two levels of fire severity estimated by the levels of tree crown damage—scorched and unaffected crown—were compared. Seed dispersal and first cohort pine (November 2001) seedling density, before salvage logging, were significantly and positively affected by fire severity. Between November and January, a fungal attack caused a noticeable decrease in seedling density in both levels of fire severity. The first cohort survival was significantly reduced by harvesting and slash treatments carried out in February 2002. However, slash chopping favoured a new pine cohort, particularly in the unaffected crown plots, in which seedling density was significantly higher than in the scorched crown plots between July 2002 and February 2003. First cohort seedling survival and height were positively related. Fire severity levels, combined with post fire management, did not appear to determine final pine seedling density and height. Finally, reduction in seedling density caused by post-fire management did not threaten pine establishment and may reduce the need for subsequent thinning operations.     

Post-dispersed pine seed removal and its effect on seedling establishment in a Mexican Temperate Forest

In order to assess the impact of seed removal and seedling establishment for four species of pines, we designed experiments with and without the exclusion of seed removers in three vegetation types (pine forest, oak-alder forest, and subalpine grassland). Seed removal was significantly different between species of pines (P < 0.01), as was the interaction between the vegetation types and category of exclusion (remover) (P < 0.0001). The significant difference in terms of seed removal was between P. patula and P. montezumae (33.0 and 17.9%, respectively). Seed removal was significant between pine forest—without exclusion (20.0%) versus oak-alder forest—without exclusion (7.0%). There was significant interaction between seedling establishment of the pine species and vegetation type (P < 0.0001). Highlighting differences between the pine forest—P. teocote (84.1%) versus oak-alder forest—P. patula (19.0%), oak-alder forest—P. pseudostrobus (45.0%), pine forest—P. patula (20.2%), pine forest—P. pseudostrobus (45.6%), subalpine grassland—P. montezumae (24.3%), subalpine grassland—P. patula (27.9%), and subalpine grassland—P. pseudostrobus (17.5%). The impact of the food preferences of rodents and other granivores for P. patula and P. pseudostrobus seeds, as well as the poor survival of seedlings of these species in the pine and oak-alder forest are both factors which may explain the dominance of P. teocote in the study region.     

A review of factors affecting the population dynamics of jack pine budworm (Choristoneura pinus pinus Freeman)

Jack pine budworm (Choristoneura pinus pinus Free.) (Lepidoptera: Tortricidae) is a native insect that periodically defoliates areas of jack pine (Pinus banksiana Lamb.) in the subboreal forests of North America east of the Rocky Mountains. Outbreaks of jack pine budworm generally occur at 6- to 12-year intervals and collapse after 2–4 years. Periodicity of outbreaks varies and is associated with site-related factors. Survival of early-instar larvae during spring dispersal is tied to the abundance of pollen cones (microsporangiate strobili), which provide a refuge for larvae until current-year needles expand. Jack pine trees that have been heavily defoliated produce few pollen cones in the following year, often resulting in high mortality of early-stage larvae. A diverse guild of generalist parasitoids attack jack pine budworm, but only a few species account for most mortality in any area. Collapsing jack pine budworm populations are characterized by sharp declines in early instar survival, coupled with an increased rate of parasitism in the late larval and pupal stages. The reciprocal interaction between heavy defoliation and low pollen cone production, and increased parasitism of late-stage larvae or pupae, are consistent with second-order density dependence factors identified in analysis of a long-term population data set. Since the 1950s, several jack pine budworm outbreaks have been roughly synchronous over a large geographic area, suggesting that Moran effect processes, as well as moth dispersal or other factors, may be involved in jack pine budworm dynamics. Although the short duration of outbreaks enables most trees to recover, over time dead trees and top-killed trees accumulate in jack pine stands. Jack pine is well adapted to fire and when fires ignite, the accumulation of dead trees and woody debris often leads to intense wildfires followed by prolific regeneration. The three-way interaction of jack pine, jack pine budworm, and fire ultimately serves to maintain vigorous stands and ensures continued hosts for jack pine budworm. Received: October 1, 1999 / Accepted: September 22, 2000     

Microhabitat selection by Eurasian lynx and its implications for species conservation

We studied microhabitat selection of the Eurasian lynxLynx lynx (Linnaeus, 1758) at 116 hunting and 88 resting sites in Białowieża Primeval Forest (Poland) to describe its characteristics and determine the importance of habitat structure for stalking prey and for security during resting. We identified lynx-used sites by radio-tracking 3 male and 3 female lynx. When hunting, the lynx did not select for any type or age class of forest. During both summer and winter, the lynx selected sites characterized by high complexity (number of structures useful for stalking: fallen logs and branches, root plates, patches of dense bushes) and low visibility. In summer, hunting sites were often located in the vicinity of small forest glades that provided good stalking opportunities for lynx and rich foraging resources for roe deer — the main prey of lynx. The habitat at kill sites was more open than at sites where the prey was cached, with higher visibility, lower density of trees and poorer undergrowth. The most important characteristic of resting sites was very low visibility that resulted mainly from using young pine or spruce thickets in the winter and dense undergrowth of oak-lime-hornbeam and ash-alder forests in the summer. The information provided by this study could have direct implications for Eurasian lynx conservation by guiding forest restructuring to better suit the species’ biological requirements.     

吉林蛟河阔叶红松林物种多度分布模型研究

以吉林蛟河阔叶红松林的木本植物为研究对象,将30hm²的样地面积划分为5m×5m,10m×10m,20m×20m,25m×25m的连续取样单元,在4个不同尺度下分别统计各物种在每个取样单元中的有无,得到每个物种在不同尺度下的取样单元数。利用随机分布模型和负二项分布模型分析物种的多度分布,对比预测多度与观测多度讨论两个模型的科学性与实用性。结果表明：对于阔叶红松林而言,负二项分布模型在所有研究尺度上的预测精度都要优于随机分布模型。随机分布和负二项分布的模型预测误差随着研究尺度的增大而增大,因此选取较小的取样单元可以切实提高物种多度的预测精度。利用随机分布和负二项分布模型对多度较小的物种进行预测的效果要优于多度较大的物种。负二项分布模型适合用来模拟阔叶红松林的物种多度分布格局,并且模型的拟合效果受取样单元大小影响。     

Dynamics of pine forest state at changing emission loads

The dynamics of pine stands (Pinus sylvestris L.) polluted by fluorine-containing emissions has been studied for several decades—from the moment of emission source appearance to present. Condition of the pine stands was estimated on the complex of parameters: accumulation of toxicants in the needle and changing physiological, biochemical and morphometrical parameters of trees. On the basis of the available data several scenarios of situation development were predicted for the following years.     

Evaluation of genetic variation of attack and resistance in lodgepole pine in the early stages of a mountain pine beetle outbreak

We examined variation of attack by mountain pine beetle (MPB) (Dendroctonus ponderosae) (Coleoptera: Scolytidae) in a 20-year-old lodgepole pine open-pollinated (OP) family trial composed of 165 OP parent-trees originating from local and nonlocal provenances. Trees were assessed in the summer of 2005 for traits relating to attack, survival, gallery formation, and infection from the fungi associated with MPB, Ophiostoma sp. Successful initial attack was determined by the presence of dead (i.e., red or gray foliage) crowns and the presence of entrance holes from MPB. Eighty-seven percent of the trees still had green crowns in the fall of 2005 (GC05), with family mean differences ranging from 46 to 100%. The mean number of pitch tubes per tree (PT#05) (in a sampling area of 225 cm² at breast height) was 1.5 with a range from 0 to 14 per tree. However, for pitch tubes indicating presence or absence (PTP05) of MPB on each tree, 63% of the trees had pitch tubes and family means ranged from 7 to 100%. Significant levels of genetic variation were found for GC05 and PTP05 with narrow-sense heritabilities of 0.20 (SE = 0.11) and 0.26 (SE = 0.07), respectively. Provenance differences were also significant, indicating that some population structure is present for these “resistance” attributes. The family breeding value correlations between 10-year height growth and PTP05 was 0.22, indicating that at the population level faster growing families may be slightly more subject to attack. An intensive survey of a subsample of 442 trees in the test (selected from 50 families with a range of attack levels) was conducted, and trees were reassessed for the presence of attack, presence of blue stain in the wood, and presence of galleries and egg chambers/eggs in the gallery. Family means ranged from 0 to 57% for blue stain, 11 to 63% for galleries, and 0 to 57% for egg chambers/eggs; however, due to the relatively small sample sizes and the nature of the binary data, family differences were not highly statistically significant. Further research is underway to improve the quantitative genetic parameters and determine the actual mechanisms at work; however, it is clear the MPB does react differently to host genotypes in terms of initial attack.     

Temperature extremes, density dependence, and southern pine beetle (Coleoptera: Curculionidae) population dynamics in east Texas

Previous studies of the southern pine beetle, Dendroctonus frontalis Zimm., established that its population in east Texas responds to a delayed density-dependent process, whereas no clear role of climate has been determined. We tested two biological hypotheses for the influence of extreme temperatures on annual southern pine beetle population growth in the context of four alternative hypotheses for density-dependent population regulation. The significance of climate variables and their interaction with population regulation depended on the model of density dependence. The best model included both direct and delayed density dependence of a cubic rather than linear form. Population growth declined with the number of days exceeding 32 degrees C, temperatures previously reported to reduce brood survival. Density dependence also changed with the number of hot days. Growth was highest in years with average minimum winter temperatures. Severely cold winters may reduce survival, whereas warm winters may reduce the efficiency of spring infestation formation. Whereas most previous studies have incorporated climate as an additive effect on growth, we found that the form of delayed density dependence changed with the number of days >32 degrees C. The interaction between temperature and regulation, a potentially common phenomenon in ecology, may explain why southern pine beetle outbreaks do not occur at perfectly regular intervals. Factors other than climate, such as forest management and direct suppression, may have contributed significantly to the timing, severity, and eventual cessation of outbreaks since the mid-1950s.     

Effects of mixing pine and broadleaved tree/shrub litter on decomposition and N dynamics in laboratory microcosms

This study was carried out to compare the ecological function of exotic pine (Pinus radiata—Pr) and native pine (Pinus tabulaeformis—Pt) in terms of litter decomposition and its related N dynamics and to evaluate if the presence of broad-leaved tree species (Cercidiphyllum japonicum—Cj) or shrub species (Ostryopsis davidiana—Od) litter would promote the decomposition of pine needles and N cycling. Mass remaining, N release of the four single-species litters and mixed-species (Pt + Cj; Pr + Cj; Pt + Od; Pr + Od) litters and soil N dynamics were measured at microcosm scale during an 84-day incubation period. The Pt and Pr litter, with poorer substrate quality, indicated slower decomposition rates than did the Cj and Od litter. Due to their high C/N ratios, the N mass of Pt and Pr litter continuously increased during the early stage of decomposition, which showed that Pt and Pr litter immobilized exogenous N by microbes. No significant differences of soil inorganic, dissolved organic and microbial biomass N were found between the Pt and Pr microcosm at each sampling. The results showed that the exotic Pr performed similar ecological function to the native Pt in terms of litter decomposition and N dynamics during the early stage. The presence of Cj or Od litter increased the decomposition rates of pine needle litter and also dramatically increased soil N availability. So it is feasible for plantation managers to consider the use of Cj as an ameliorative species or to retain Od in pine plantations to promote the decomposition of pine litter and increase nutrient circulation. The results also suggested that different species litters induced different soil dissolved organic nitrogen (DON). As a major soluble N pool in soil, DON developed a different changing tendency over time compared with inorganic N, and should be included into soil N dynamic under the condition of our study.     

Lodgepole pine forest age class dynamics and susceptibility to mountain pine beetle attack

Because mountain pine beetle attack mature pine stands, an understanding of forest age class dynamics is important to managing forests within the distribution of the beetle. The assumed theoretical negative exponential forest age distribution provides an estimate when ecosystem dynamics are in equilibrium. This study investigates the dynamics of forest age distribution for non-equilibrium ecosystem dynamics, which result primarily from large and irregular stand-replacement fire disturbances that alter the forest age distribution. A model experiment using the SEM-LAND model on a 1 million ha lodgepole pine forest landscape was conducted to estimate how the proportion of susceptible area could be influenced by different fire regimes. The results of the simulation suggest that the temporal dynamics of the area susceptible to mountain pine beetle attack are complex and depend on the fire history of the study area, if the area is experiencing large and irregular stand-replacement fires. The age range of the lodgepole pine forest stands susceptible to mountain pine beetle attack might significantly affect the estimate of the area susceptible to attack.     

Mitochondrial haplotypic diversity of pine cone beetles (Scolytinae: Conophthorus) collected on food sources

Conophthorus Hopkins attack, oviposit, and feed in immature cones of many pine (Pinus) species. They are a serious pest of pine seed orchards and can destroy up to 100% of the cone crop. Beetles can plague orchards over many years because emerging beetles tend to attack cones of the same or a nearby tree. However, fluctuating pine cone production suggests that beetles may disperse from their natal tree stand to find second-year cones for oviposition. These dispersal behaviors may influence population level genetic diversity, that is, populations may exhibit low or high diversity. In this study, we assess the mitochondrial haplotypic diversity among 10 populations of Conophthorus representing four species. Furthermore, the haplotypic diversities are compared with published haplotypic diversities of other scolytine species to assess the influence of fluctuating food resources on Conophthorus haplotype diversity. Conophthorus haplotypic diversity ranged between 13 and 70%, which was similar to population level haplotypic diversities of other scolytines. The tendency of the emerging brood to reinfest the same tree has little influence on haplotype composition of populations and haplotype diversity is likely more influenced by beetles in search of pine cones.     

Estimation of population density of European pine marten in central Italy using camera trapping

Evaluating presence and abundance of small carnivores is essential for their conservation. In Italy, there is scarce information on European pine marten distribution, and no data are published on its abundance. Camera traps have been widely used to estimate population density applying capture–recapture models for species in which individual recognition is possible. Here we estimate the abundance of European pine martens in central Italy using camera trapping and a model that allows the estimation of population density without the need for individual recognition Rowcliffe et al. (Anim Conserv 11:185–186, 2008). Camera trapping was also used to evaluate habitat use patterns by martens. Fifteen camera traps were deployed in 90 placements for 15 days each, for a total of 1,334 camera days. Pine martens were captured in 24% of camera trap placements with a mean trap success rate of 0.33 photographs per camera placement. Estimated pine marten population density in the study area was 0.34 individuals km⁻². Marten trap rate was not strongly associated with any habitat type, although there were trends towards lower probability of records at locations with high coverage of cultivated fields and higher probability of records at locations with high coverage of human-made woodland. The results suggest that pine martens in this area are not confined to wooded habitat. To our knowledge, this study is the first application of the Rowcliffe et al. (Anim Conserv 11:185–186, 2008) method to a wild carnivore population and, furthermore, the first estimation of population density of pine martens in Italy.     

Attack dynamics of the pine shoot beetle, Tomicus piniperda (Col.; Scolytinae) in Scots pine stands defoliated by Bupalus piniaria (Lep.; Geometridae)

Abstract 1 After a 1‐year, extensive pine looper (Bupalus piniaria) outbreak, plots were laid out to study tree susceptibility to attack, and performance of Tomicus piniperda in pine trees suffering from varying levels of defoliation. 2 Tomicus piniperda was the dominating stem‐attacking species among the primary stem colonizers, and 82% of all trees that died had been colonized by T. piniperda. 3 Beetle attacks primarily struck severely defoliated trees, i.e. trees that suffered from 90% to 100% defoliation. 4 Beetle attacks peaked in the second year after cessation of the outbreak, and suppressed trees were both more frequently attacked and more susceptible to beetle attack than intermediate and dominant trees. 5 Trees surviving beetle attacks carried more foliage than trees that did not survive the attacks. 6 A single year of severe defoliation is enough to render pine trees susceptible to secondary pests, such as T. piniperda.     

Modeling the dynamics of mountain pine beetle aggregation in a lodgepole pine stand

Summary At least once a year the mountain pine beetle searches for lodgepole pines that provide a suitable habitat for a new brood. After attacking females feed, they produce an attractant pheromone that causes beetles to aggregate and, during outbreaks, to usually mass attack the focus tree. Near the completion of mass attack, incoming beetles are repelled and initiate attacks on adjacent recipient trees. An understanding of this switching process is useful for prescribing measures that minimize beetle damage.A mathematical model was developed to (1) describe beetle aggregation, (2) predict the relation of tree susceptibility and switching to changes in beetle density, (3) provide a structure for current knowledge, and (4) pose questions for further research. The model indicates that a high population density ensures mass aggregation and consequently successful tree colonization and switching. The model also indicates that the number of beetles attracted per attacking beetle differs from tree to tree, possibly depending on resin quality and production and/or the local flying density of beetles. Field and model results indicate that tree size appears to affect the repellence of beetles, suggesting that the attack density or the visual attractiveness of large trees is a factor. Further research could be directed at our assumptions on host resistance, repellence, pheromone emission rates, threshold concentrations, navigation, and pheromone dispersion. Return Address: Center for Quantitative Sciences, University of Washington, Seattle, Washington, 98195, USA     

Seasonal changes in antioxidant level of scots pine (Pinus sylvestris L.) needles exposed to industrial pollution. I. ascorbate and thiol content

Current and previous year needles from three 16 years-old populations of Scots pine (Pinus sylvestris L.) trees were seasonally collected at the three experimental areas: Luboń- close to the phosphate fertiliser factory, Głogów — close to the copper foundry and Kórnik — control site. Głogów is the most polluted site, where at 1998 monthly mean daily concentrations of different pollutants were: SO₂ - 17 μg·m⁻³, NO_x - 12 μg·m⁻³ and dust containing heavy metals as Cu, Pb, Cd - 29 μg·m⁻³. Trees growing in Luboń were influenced for many years by high concentration of SO₂ and fluor compounds. A few years ago emissions were markedly reduced, but low pH of soil and high concentration of aluminium ions still influence the growth of trees. Seasonal changes of ascorbate and thiol content were observed in each needle class and population, with the maximum in the winter and minimum in the summer. In needles from trees growing on polluted sites higher level of ascorbic acid and thiols comparing to control site was observed. Significant differences appeared in each population of Scots pine growing under higher pollution stress in the Głogów site. In needles from trees growing in Luboń significant differences in ascorbic acid and thiols content were evidently less numerous. Needles from polluted sites in some seasons contained significantly more malondialdehyde (MDA) and those was more frequent in Głogów than in Luboń. The results indicated that in the Głogów site trees are more influenced by pollution stress than in Luboń and the defense reaction measured as an increase of the antioxidant level is more evident.     

Non-invasively determined multi-site variation in pine marten <Emphasis Type="Italic">Martes martes</Emphasis> density,a recovering carnivore in Europe

Pine martens (Martes martes) are subject to national and international conservation legislation throughout most of their European range. Yet population density and abundance estimates, which are a key component of effective conservation management, are lacking in many countries. In this study, a large-scale non-invasive survey was undertaken in 14 forested study sites throughout Ireland to assess variation in pine marten density and abundance. Pine marten hair samples were collected in each study site and analysed using genetic techniques to determine individual identity data. Density and abundance estimates were obtained using spatially explicit capture-recapture models and CAPWIRE. Across all study sites, a total of 93 individual pine marten were identified and captured 217 times. Estimated pine marten density varied from 0 to 2.60 individuals per km² of forested habitat, with all but a single site having estimated densities of ≤1 pine marten per km² of forest habitat. Mean population abundance estimates across all study sites ranged from 0 to 27 individuals. Spatially explicit capture-recapture models on combined data across all 14 study sites provided a mean density estimate of 0.64 (95% CI 0.49–0.81). Combining this with data on the current distribution and estimated area of forest habitat occupied by the species in Ireland, the total pine marten population abundance of pine marten in Ireland was estimated at 3043 (95% CI 2330–3852) individuals. This research has conducted the largest scale investigation of pine marten density and abundance in any part of its global distribution and provided an improved basis for future population assessment and monitoring of this species.     

Rapid assessment of antimould efficacies of pressure-treated southern pine

A membrane-screening method was developed in conjunction with flow cytometric (FC) analysis for determining the efficacies of antimould pressure-treatment formulations for mould species of cosmetic significance on southern pine. Fusarium subglutinans, Aspergillus flavus, Penicillium chrysogenum, and Paecilomyces spp. were the predominant moulds colonizing surfaces of the variously treated pine stored in sealed plastic bags over 3- to 6-month periods. Nylon membranes placed directly on pressure-treated pine and membranes saturated with the various formulations were inoculated with the conidia of selected moulds. FC analysis of conidia stained with propidium iodide (PI) before and after exposure to the pressure-treatment formulations permitted a rapid assessment of the inocula and selection of those pressure-treatment formulations with probable inhibitory activity versus probable nonactive preparations. Recoveries of the fungi from the membranes over 9–14 days were in general agreement with the emergence of colonizing fungi on the similarly preserved uninoculated pine stored in sealed plastic bags for 6 months. This combination of procedures provided for a relatively rapid assessment of preservative formulations designed to provide enhanced efficacy against surface mould growth on lumber during storage and retail display. Received 21 December 2001/ Accepted in revised form 20 May 2002     

Allelopathy of red pine: isolation and identification of an allelopathic substance in red pine needles

Since red pine (Pinus densiflora Sieb. et Zucc.) often forms sparse forest floors where herbaceous plants do not grow well, allelopathy of red pine was investigated. A growth inhibitory substance was isolated from an aqueous methanol extract of red pine needles and determined by spectral data as abscisic acid-β-d-glucopyranosyl ester (ABA-GE). This substance inhibited root and shoot growth of cress and E. crus-galli seedlings at concentrations greater than 0.1 μM. The concentrations required for 50% growth inhibition on roots and shoots of cress were 0.23 and 0.61 μM, respectively, and those of E. crus-galli were 1.1 and 2.8 μM, respectively. The activity of ABA-β-d-glucosidase, which liberates free ABA from ABA-GE, in cress and E. crus-galli seedlings was 13–29 nmol mg⁻¹ protein min⁻¹. Endogenous concentration of ABA-GE in the pine needles was 4.1–21.5 μmol kg⁻¹ and the concentration in soil water of the pine forest was 2.5 μM. The effectiveness of ABA-GE on growth inhibition and the occurrence of ABA-GE in pine needles and soil water suggest ABA-GE may play an important role in the allelopathy of red pine resulting in the formation of sparse forest floors.