Population dynamics of the white pine weevil, Pissodes strobi, infesting jack pine, Pinus banksiana, in Ontario, Canada

1. Eight generations of white pine weevil, Pissodes strobi (Peck) , infesting the terminal shoots of young jack pine trees, were sampled as larvae, pupae, and adults between 1988 and 1995.
2. The density of adult weevils increased rapidly for the first 3 years of the study, then declined in the next 4 years. Between-generation rates of change in density of weevils were related to mean number of weevils produced per terminal shoot of the host tree. Net increases in population density followed years in which a relatively high number of weevils emerged per terminal shoot and vice versa.
3. The mean number of weevils emerging per terminal shoot was determined by survival of weevils between the end of the larval stage and the successful emergence of adult weevils.
4. There was no clear relationship between survival of the post-feeding stages of the weevil and rates of parasitism or bird predation on these same stages. There was, however, a strong negative relationship between survival of weevils within the terminal shoot and the abundance of the facultative dipteran predator Lonchaea corticis Taylor.
5. The relationship among generational rates of change in populations, survival, and predation was evident irrespective of the age of the trees infested, suggesting that population dynamics of the weevil may be influenced as much by local predation pressure as by physical and biotic changes associated with growth of the young host trees.     

Mountain pine beetle selectivity in old‐growth ponderosa pine forests,Montana, USA

A historically unprecedented mountain pine beetle (MPB) outbreak affected western Montana during the past decade. We examined radial growth rates (AD 1860–2007/8) of co‐occurring mature healthy and MPB‐infected ponderosa pine trees collected at two sites (Cabin Gulch and Kitchen Gulch) in western Montana and: (1) compared basal area increment (BAI) values within populations and between sites; (2) used carbon isotope analysis to calculate intrinsic water‐use efficiency (iWUE) at Cabin Gulch; and (3) compared climate‐growth responses using a suite of monthly climatic variables. BAI values within populations and between sites were similar until the last 20–30 years, at which point the visually healthy populations had consistently higher BAI values (22–34%) than the MPB‐infected trees. These results suggest that growth rates two–three decades prior to the current outbreak diverged between our selected populations, with the slower‐growing trees being more vulnerable to beetle infestation. Both samples from Cabin Gulch experienced upward trends in iWUE, with significant regime shifts toward higher iWUE beginning in 1955–59 for the visually healthy trees and 1960–64 for the MPB‐infected trees. Drought tolerance also varied between the two populations with the visually healthy trees having higher growth rates than MPB‐infected trees prior to infection during a multi‐decadal period of drying summertime conditions. Intrinsic water‐use efficiency significantly increased for both populations during the past 150 years, but there were no significant differences between the visually healthy and MPB‐infected chronologies.     

Primers designed to amplify a mitochondrial nad1 intron in ponderosa pine, Pinus ponderosa, limber pine, P. flexilis, and Scots pine, P. sylvestris

The b/c intron of the mitochondrial nad1 gene, was sequenced to characterize the indel region of ponderosa pine, Pinus ponderosa. The sequence in ponderosa pine was aligned with the sequence in Scots pine, Pinus sylvestris, to design seven primers that are useful for sequencing and for revealing size variation in amplified fragments in ponderosa pine, Scots pine, and limber pine, Pinus flexilis. These primers reveal variability in all three species, and the pattern of variability within ponderosa pine is described by a preliminary survey. The indel region of ponderosa pine contains three distinct elements with lengths of 31, 32, and 34 bp. Received: 1 March 2000 / Accepted: 14 April 2000<@head-com-p1a.lf>Communicated by P.M.A. Tigerstedt     

Effects of mountain pine beetle on fuels and expected fire behavior in lodgepole pine forests, Colorado, USA

In Colorado and southern Wyoming, mountain pine beetle (MPB) has affected over 1.6 million ha of predominantly lodgepole pine forests, raising concerns about effects of MPB-caused mortality on subsequent wildfire risk and behavior. Using empirical data we modeled potential fire behavior across a gradient of wind speeds and moisture scenarios in Green stands compared three stages since MPB attack (Red [1-3 yrs], Grey [4-10 yrs], and Old-MPB [～30 yrs]). MPB killed 50% of the trees and 70% of the basal area in Red and Grey stages. Across moisture scenarios, canopy fuel moisture was one-third lower in Red and Grey stages compared to the Green stage, making active crown fire possible at lower wind speeds and less extreme moisture conditions. More-open canopies and high loads of large surface fuels due to treefall in Grey and Old-MPB stages significantly increased surface fireline intensities, facilitating active crown fire at lower wind speeds (>30-55 km/hr) across all moisture scenarios. Not accounting for low foliar moistures in Red and Grey stages, and large surface fuels in Grey and Old-MPB stages, underestimates the occurrence of active crown fire. Under extreme burning conditions, minimum wind speeds for active crown fire were 25-35 km/hr lower for Red, Grey and Old-MPB stands compared to Green. However, if transition to crown fire occurs (outside the stand, or within the stand via ladder fuels or wind gusts >65 km/hr), active crown fire would be sustained at similar wind speeds, suggesting observed fire behavior may not be qualitatively different among MPB stages under extreme burning conditions. Overall, the risk (probability) of active crown fire appears elevated in MPB-affected stands, but the predominant fire hazard (crown fire) is similar across MPB stages and is characteristic of lodgepole pine forests where extremely dry, gusty weather conditions are key factors in determining fire behavior.     

A reappraisal of the population dynamics of the pine beauty moth, Panolis flammea, on lodgepole pine, Pinus contorta, in Scotland

The pine beauty moth, Panolis flammea, is a defoliating pest of lodgepole pine (Pinus contorta) forests in Scotland. This article reviews early and recent research on the population ecology of Panolis flammea and presents an analysis of pupal survey data collected between 1977 and 1993. Research in the 1980s suggested that natural enemies, although effective in preventing P. flammea outbreaks on Scots pine (Pinus sylvestris), played an insignificant role in the population dynamics of P. flammea on lodgepole pine. However, analysis of pupal survey data showed that delayed density-dependent action of natural enemies, probably parasitoids, was overlooked during the 1970s and 1980s. Recent research suggests that fungal pathogens are responsible for a decline in the frequency and severity of outbreaks of P. flammea on lodgepole pine. This suggestion, together with the overlooked importance of other natural enemies, indicates that the population ecology of P. flammea in Scotland has changed during the past 20 years and requires a full reappraisal. Received: May 31, 1999 / Accepted: August 18, 1999     

Characterization of microsatellite loci in the fungus, Grosmannia clavigera, a pine pathogen associated with the mountain pine beetle

The largest forest pest epidemic in Canadian history caused by the mountain pine beetle (MPB) and its fungal associates has killed over 15 million hectares of forest. Sixty simple sequence repeat regions were identified from Grosmannia clavigera, an MPB associated fungus. Eight loci genotyped in 53 isolates from two populations in British Columbia, Canada revealed three to 10 alleles per locus and gene diversities of 0 to 0.79. All but two of these loci showed length polymorphism in Leptographium longiclavatum, a related MPB fungal associate. These microsatellites will be useful in population genetic studies of these fungi.     

Carbon and nitrogen status of litterfall, litter decomposition and soil in even-aged larch, red pine and rigitaeda pine plantations

The carbon (C) and nitrogen (N) status in forest ecosystems can change upon establishment of plantations because different tree species have different nutrient cycling mechanisms. This study was carried out to evaluate C and N status of litterfall, litter decomposition and soil in three adjacent plantations consisting of one deciduous (larch: Larix leptolepis) and two evergreen (red pine: Pinus densiflora; rigitaeda pine: P. rigida × P. taeda) species planted in the same year (1963). Both the pine plantations showed comparatively higher C input from needle litter but significantly lower N concentration and input than the larch plantation (P < 0.05). During the decomposition process, the deciduous larch needle litter showed low C concentration and C remaining in soil, but high N concentration and N remaining in soil compared to the two evergreen pine needle litters. However, the soil C and N concentration and their content at a soil depth of 0–10 cm were not affected significantly (P > 0.05) by the plantation type. These results demonstrate the existence of considerable variation in C and N status resulting from needle litter input and litter decomposition in these three plantations grown at sites with similar environmental conditions.     

Influences of the biophysical environment on blister rust and mountain pine beetle,and their interactions,in whitebark pine forests

Aim To understand how the biophysical environment influences patterns of infection by non‐native blister rust (caused by Cronartium ribicola) and mortality caused by native mountain pine beetles (Dendroctonus ponderosae) in whitebark pine (Pinus albicaulis) communities, to determine how these disturbances interact, and to gain insight into how climate change may influence these patterns in the future. Location High‐elevation forests in south‐west Montana, central Idaho, eastern and western Oregon, USA. Methods Stand inventory and dendroecological methods were used to assess stand structure and composition and to reconstruct forest history at sixty 0.1‐ha plots. Patterns of blister rust infection and mountain pine beetle‐caused mortality in whitebark pine trees were examined using nonparametric Kruskal–Wallis ANOVA, Mann–Whitney U‐tests, and Kolmogorov–Smirnov two‐sample tests. Stepwise regression was used to build models of blister rust infection and mountain pine beetle‐related mortality rates based on a suite of biophysical site variables. Results Occurrence of blister rust infections was significantly different among the mountain ranges, with a general gradient of decreasing blister rust occurrence from east to west. Evidence of mountain pine beetle‐caused mortality was identified on 83% of all dead whitebark pine trees and was relatively homogenous across the study area. Blister rust infected trees of all ages and sizes uniformly, while mountain pine beetles infested older, larger trees at all sites. Stepwise regressions explained 64% and 58% of the variance in blister rust infection and beetle‐caused mortality, respectively, indicating that these processes are strongly influenced by the biophysical environment. More open stand structures produced by beetle outbreaks may increase the exposure of surviving whitebark pine trees to blister rust infection. Main conclusions Variability in the patterns of blister rust infection and mountain pine beetle‐caused mortality elucidated the fundamental dynamics of these disturbance agents and suggests that the effects of climate change will be complex in whitebark pine communities and vary across the species’ range. Interactions between blister rust and beetle outbreaks may accelerate declines or facilitate the rise of rust resistance in whitebark pine depending on forest conditions at the time of the outbreak.     

Segregation,linkage, and diversity of allozymes in knobcone pine

Summary Female gametophytes of knobcone pine were used to study genetic variation at 58 loci in 26 enzyme systems. Mendelian segregation and linkage were tested at 21 loci. Got1, Pgi2, Mnr3, Adh2, and Lap2 were linearly arrayed in a single linkage group. Est and Acp3, and Flest and Lap1, formed two independent linkage groups. Although Mendelian segregation was the rule, several cases of segregation distortion were observed. Pooled over trees, Lap1 and Aap1 showed significant distortion. Of 11 cases of distortion observed for individual trees, 10 showed an excess of common alleles. Pooled over both loci and trees, giving a total sample of 17,183 gametes, the common alleles were significantly overrepresented by 1.1%, and heterogeneity was highly significant. Our results, and others in the literature, suggest that segregation distortion may affect the genetic structure of conifer populations.     

湖北宜昌松林景观格局对松材线虫流行及扩散的影响

景观格局对能量流、物质流和物种流等生态学过程影响显著。为了探究区域生境差异对病虫害发生及扩散的影响,以湖北省宜昌市夷陵区松材线虫病为对象,结合区域森林资源二类清查矢量数据和松材线虫病普查资料,运用景观生态学的原理和方法,探究景观格局对松材线虫病发生的影响。研究结果表明:1)松林景观类型百分比、平均斑块面积、自然连接度和聚合度与松材线虫病的发病率成正相关;2)松林斑块的粒级结构分析表明,中、小斑块能抑制松材线虫病的发生,巨斑块、超大斑块对松材线虫的发生有利;3)从景观干扰上分析显示人类活动强度与松材线虫病发病率成正相关;4)在景观尺度水平上,景观的破碎度大、多样性指数高、蔓延度指数小、斑块形状简单、受人类活动影响大的乡镇松材线虫病发病率高。通过斑块类型尺度和景观尺度两个水平上的分析可知,在夷陵区乡镇尺度上,由小斑块松林组成且斑块聚集度低、景观破碎化程度低的景观格局对松材线虫病有一定的抑制作用。研究结论对当地松材线虫病的防治就有较好的参考价值。     

马尾松毛虫种群消长与寄主受害程度的关系

研究不同受害程度松林与马尾松毛虫Dedrolimuspunctatus(Walker)种群发育阶段的关系。结果表明,松毛虫大面积发生时松林的受害程度可以很好地标示着松毛虫种群的发生阶段。松林点片受害显示松毛虫种群进入上升开始阶段;松林受害程度中等时,松毛虫仍处于上升种群阶段;当松林的针叶被吃光,表明松毛虫已处暴发阶段。松毛虫暴发种群在自然情况下,将出现典型的蛹期和下一代卵期的寄生率大幅度升高、雌性比、蛹重和产卵量等种群参数大幅度下降等特征;其后代会自然转入下降种群或进入低虫口期。但这些暴发种群的卵转入在保证充足饲料的可控条件下饲养时,其后代的生长发育、存活率、性比、蛹重等主要种群参数没有明显差异。即没显示出上升种群和暴发种群的特征差异,说明暴发种群的终止主要是受外界环境的限制而不是松毛虫本身的内因所致。     

Microsatellite variability of Sardinian pine martens, Martes martes

The pine marten, Martes martes, is a medium-sized terrestrial carnivore associated with woodland habitats of the western Palearctic region. The present distribution area of the species also includes six islands of the western Mediterranean basin. The origin of these insular populations and their taxonomic status are still debated; their molecular characterization appears relevant for conservation purposes. To describe the genetic variability of the pine martens from Sardinia we characterized 40 insular and 14 Italian individuals at seven nuclear microsatellite loci. The identification of private alleles and the calculated F(ST) value of 0.074 revealed some genetic differentiation between the two populations, which accounts for the high percentages of correct allocation (96.39-98.80%) scored by the genotype assignment test. The presence of two distinct clusters corresponding to Sardinia and mainland Italy was further confirmed by the multivariate Factorial Correspondence Analysis of individual genotypes. Moreover, the genome of the Sardinian individuals bore signs of past demographic fluctuations, i.e. the presence of the monomorphic locus Ma-4, a lower allelic richness and a lower number of private alleles, which may derive from the combination of drift, founder effects, and human overexploitation. Anyway, if such events ever affected the Sardinian population, this is likely to have happened in the past since, according to our microsatellite data, the present-day population does not show evidence of recent bottlenecks or inbreeding, the Wilcoxon sign-rank test and the F(IS) index being not statistically significant (both P > 0.05). Based on this genetic evidence, we advance hypotheses about the distinctiveness of the Sardinian population and its significance for taxonomy and conservation.     

Gas exchange and canopy structure of 9-year-old loblolly pine,pitch pine and pitch x loblolly hybrids

Summary Seasonal gas exchange and canopy structure were compared among 9-year-old loblolly pine (Pinus taeda L.), pitch pine (Pinus rigida Mill.), and pitch x loblolly hybrids (Pinus rigida x taeda) growing in an F2 plantation located in Critz, Va., USA. Leaf net photosynthesis, conductance, internal CO₂ concentration (c_i), water use efficiency (WUE; photosynthesis/conductance), dark respiration and the ratio of net photosynthesis/respiration did not vary among or within the three taxa. Significant differences in volume production, crown length, total crown leaf surface area and the silhouette area of shade shoots among the taxa were observed. The loblolly-South Carolina source had greater volume and crown surface area than the pitch pine, and the hybrid taxa were intermediate between the two. Although the silhouette area ratio of shade foliage varied among taxa, it was not related to volume. A strong relationship between total leaf surface area and volume was observed. Leaf conductance, c_i, WUE and leaf water potential were the physiological parameters significantly and positively correlated with volume. This study suggests that the amount of needle surface in the canopy is more important in early stand volume growth than the leaf carbon exchange rate and the degree of needle self-shading in the lower canopy.     

Verticillium balanoides, a nematode endoparasite associated with pine needles of collapsing Japanese red pine trees in Tsukuba

Verticillium balanoides, isolated from nematodes associated with pine needles of collapsing Japanese red pine trees in Tsukuba, which is new to Japan, was redescribed with illustrations.     

Adult parasitoids of the southern pine beetle, Dendroctonus frontalis Zimmermann (Coleoptera: Scolytidae), feed on artificial diet on pine boles, pine canopy foliage and understory hardwood foliage

This study examined adult parasitoids of Dendroctonus frontalis Zimmermann (Coleoptera: Scolytidae) utilizing an artificial parasitoid food on locations with and without hosts. Eliminade™ was applied to bark on boles of infested pines, to pine canopy foliage and to understory hardwood foliage. Adult parasitoids were collected, identified and dissected to determine the presence of Eliminade™ within their guts. Individuals from eight parasitoid species were collected on pine boles within D. frontalis infestations in the Talladega National Forest (Alabama) in the summer of 1999 and 2000. Mean percentage of parasitoids feeding on Eliminade™ was 62±10% during both summers. Percentage of parasitoids feeding was the same 24 h after Eliminade™ application, regardless of food location or parasitoid species. Seven days later, level of parasitoid feeding on Eliminade™ was insignificant in the pine canopy and hardwood understory. In contrast, percent of parasitoid feeding on Eliminade™ applied to pine boles remained the same between 1 and 7 days of the application. Therefore, not only will adult parasitoids visit and feed on artificial food on pine boles with hosts, but also non-host locations such as pine canopy and understory hardwood foliage. These results have implications for potential sources of adult nutrition for parasitoids of D. frontalis.     

辽宁抚顺松材线虫入侵松林内天牛种类调查

【目的】松材线虫Bursaphelenchus xylophilus (Steiner&Buhrer) Nickle的媒介昆虫云杉花墨天牛Monochamus saltuarius Gebler在辽宁省被发现意味着我国北方松林的生态安全正在遭受严重的威胁。明确松材线虫入侵松林内的天牛种类、数目,可以为早期监测松材线虫媒介昆虫和潜在媒介昆虫的种群动态以及预测松材线虫病的发生提供参考。【方法】为了明确天牛广谱型引诱剂、APFI持久增强型松墨天牛高效诱剂、F8型松墨天牛引诱剂及其复配诱芯的诱捕效果,于2019-2020年的5-10月在辽宁省抚顺市的油松林、红松林、落叶松林开展诱捕天牛试验。【结果】将天牛广谱型引诱剂和F8型松墨天牛引诱剂放在同一诱捕器中具有较好引诱效果,每诱捕器捕获的天牛物种数量（油松林18种,红松林14种,共计19种）和天牛样本数量（油松林（18.31±8.86）头/周,红松林（23.44±10.92）头/周）最多。在试验林地共计诱捕到34种共计13307头天牛,其中云杉花墨天牛数量最多,占总诱捕量的67%,褐梗天牛Arhopalus rusticus、锯天牛Prionus insularis、小灰长角天牛Acanthocinus griseus、松皮花天牛Rhagium japonicum分别占总诱捕量的13.2%、6.6%、4.1%和2.7%。【结论】捕获到危害针叶树的天牛8种,包括云杉花墨天牛（优势种）、小灰长角天牛、灰长角天牛Acanthocinus aedilis、褐梗天牛、脊鞘幽天牛Asemum striatum和锯天牛。根据天牛的取食产卵习性推测,小灰长角天牛、灰长角天牛在补充营养的时候可能会传播松材线虫到健康松树上,而褐梗天牛、脊鞘幽天牛和锯天牛羽化成虫后不需补充营养且产卵在衰弱木的树皮缝隙或者表土处,它们有效传播松材线虫的几率较小。     

Host acceptance behaviour of the jack pine tip beetle, Conophthorus anksianae and the red pine cone beetle, C. resinosae

The jack pine tip beetle, Conophthorus banksianae McPherson (Coleoptera: Scolytidae) and the red pine cone beetle, C. resinosae Hopkins, are doubtful sibling species. However, it is possible that these two taxa are valid species that maintain reproductive isolation because they accept different hosts. In a series of laboratory and field cage experiments, the host acceptance behaviours of these two species under choice and no choice conditions were compared. The field experiments demonstrated that the two species have a similar propensity to accept jack pine cones and shoots for feeding, but differ consistently in their acceptance of red pine cones, and variably in their acceptance of red pine shoots. However, the laboratory experiments did not indicate a difference between the two species in their propensity to accept red pine cones for feeding. In field cages, C. resinosae accepted significantly more red pine cones for oviposition than C. banksianae; the situation was reversed for jack pine shoots. In comparison to C. banksianae, C. resinosae is a more generalist feeder. The results from this study suggest that host acceptance behaviour is a permeable barrier unable to ensure reproductive isolation between the two species. Although there are differences in the host acceptance behaviours between C. banksianae and C. resinosae, we conclude that these differences do not necessarily support their designation as distinct species.