Beetle Infestation Research Articles

Dry rot and timber decay: Don’t panic and poison yourself

This paper first shows that timber decay in buildings is primarily due to lack of maintenance and building defects, allowing water penetration into the building fabric providing ideal environmental conditions for fungal and beetle infestation. Secondly, the paper sets out how it is very important that investigations are non-destructive, and result in the correct diagnosis and identification of type and viability of decay. Thirdly the paper discusses the author’s belief that the remedial chemical timber treatments stem from fear and a lack of knowledge of dry rot, and that the demand for 30 year guarantees for treatment results in ‘overkill’. The paper advocates that the environmental control of dry rot and timber decay and preventative maintenance are preferable to conventional remedial treatments. This approach is based on scientific, practical experience and successful case studies carried out over the last 33 years, and provides not only environmentally sustainable holistic conservation solutions, but also ensures the long-term health of building materials, health of the occupants and structures.1

Long-term monitoring of the recruitment and dynamics of large wood in Kamienica Stream, Polish Carpathians

Studies presenting long-term observations of the recruitment and mobility of large wood in mountain watercourses are scarce, but they can considerably contribute to the knowledge of river/riparian forest interactions and the assessment of flood hazard resulting from wood mobility during floods. Widespread dieback of riparian forest along the headwater course of Kamienica Stream in the Polish Carpathians, caused by bark beetle infestation of spruce trees, has raised concerns about potential increases of large wood recruitment to the stream and of the flood hazard to downstream valley reaches. In October 2009, 429 trees growing along three sections of the stream were tagged with numbered metal plates and monitored over 10 years to determine the timing and causes of their delivery to the channel and the lengths of their displacement during individual flood events. Moreover, in 2012 the mode of location of wood deposits and a degree of wood decay were determined in the second- to fourth-order stream reaches. The monitoring of tagged trees indicated that trees were recruited to the channel during highintensity meteorological and hydrological events, mostly as a result of bank erosion during floods or windthrow. With 22% of tagged trees recruited to the channel during 10 years, the rate of turnover of the riparian trees was estimated at 45 years. As the riparian area is overgrown with trees with ages up to ~160 years, the rate evidences substantial intensification of large wood recruitment to the channel in the recent period. Results of large wood inventory and the 10-year-long monitoring of tagged trees indicated variable mobility of large wood along the upper course of the stream. Wood mobility was negligible in the second-order stream reach, very small in the third-order reach, and greater, but still limited in the fourth-order reach. Wood is transported longer distances only during major floods. However, the advanced state of decay of most pieces leads to their disintegration during floods, precluding distant transport. Thus, large wood retained in the upper stream course does not constitute an important flood hazard to downstream, inhabited valley reaches.

Evaluating the capabilities of Sentinel-2 data for large-area detection of bark beetle infestation in the Central German Uplands

An increase in forest damage caused by the European spruce bark beetle (Ips typographus L.) has recently been observed in many Central European forests such as the forests of the Central German Uplands. For these regions, which are highly vulnerable due to their tree species composition and an increasing frequency of extreme weather events, the availability of time- and cost-efficient monitoring procedures is of particular importance. Thus it was the objective of our study to evaluate the potential of Sentinel-2 data for large-area detection of bark beetle infestation. Using change detection, infestation maps were produced for the Saxon Switzerland National Park Forest District (SAXS) and the Black Forest National Park (BFOR). An accuracy assessment provided a user’s accuracy of 97% (SAXS) and 88% (BFOR), respectively. The calculation of the producer’s accuracy (AP) resulted in 34% (SAXS) and 4% (BFOR). However, when small infestation areas were excluded from stereoscopic reference data, AP increased up to 52% (SAXS) and 40% (BFOR), respectively. Taking these findings into account, our study highlights both the high value of Sentinel-2-based change detection for area-wide bark beetle monitoring and its limitation to large contiguous infestation areas.

Visual Exposure of Rock Outcrops in the Context of a Forest Disease Outbreak Simulation Based on a Canopy Height Model and Spectral Information Acquired by an Unmanned Aerial Vehicle

This research was focused on the study of visual exposure evolution in the locality of the Drátenická skála nature monument (in the Czech Republic) and the surrounding forest complex in terms of history and through modelling for further possible stand development. The local forests underwent conversion from a natural fir-beech composition to an intensive spruce monoculture with few insect pests or windbreak events to an actual bark beetle infestation. Historic maps, landscape paintings, photographs, and orthophotos served as the basic materials for the illustration of the past situation. Further development was modelled using canopy height models and spectral properties captured by unmanned aerial vehicles (UAVs). As an example, the possible situation of total mortality among coniferous spruce trees after a bark beetle outbreak was modelled. Other options and a practical use of such preprocessed data are, for example, a model for opening and transforming the stands around the rock as one of the ongoing outcrop management trends in the protected landscape area (PLA) of Žďárské vrchy.

Contingency Plans for the Wood Supply Chain Based on Bottleneck and Queuing Time Analyses of a Discrete Event Simulation

Wood supply chain performance suffers from risks intensified by more frequent and extreme natural calamities such as windstorms, bark beetle infestations, and ice-break treetops. In order to limit further damage and wood value loss after natural calamities, high volumes of salvage wood have to be rapidly transported out of the forest. In these cases, robust decision support and coordinated management strategies based on advanced contingency planning are needed. Consequently, this study introduces a contingency planning toolbox consisting of a discrete event simulation model setup for analyses on an operational level, strategies to cope with challenging business cases, as well as transport templates to analyze outcomes of decisions before real, costly, and long-lasting changes are made. The toolbox enables wood supply managers to develop contingency plans to prepare for increasing risk events and more frequent natural disturbances due to climate change. Crucial key performance indicators including truck to wagon ratios, truck and wagon utilization, worktime coordination, truck queuing times, terminal transhipment volume, and required stockyard are presented for varying delivery time, transport tonnage, and train pick-up scenarios. The strategy BEST FIT was proven to provide robust solutions which saves truck and train resources, as well as keeps transhipment volume on a high level and stockyard and queuing time on a low level. Permission granted for increased truck transport tonnages was evaluated as a potential means to reduce truck trips, if working times and train pick-ups are coordinated. Furthermore, the practical applicability for contingency planning is demonstrated by highly relevant business cases such as limited wagon or truck availability, defined delivery quota, terminal selection, queuing time reduction, or scheduled stock accumulation. Further research should focus on the modeling and management of log quality deterioration and the resulting wood value loss caused by challenging transport and storage conditions.

In silico identification and assessment of insecticide target sites in the genome of the small hive beetle, Aethina tumida

BackgroundThe small hive beetle, Aethina tumida, is a rapidly emerging global pest of honey bee colonies. Small hive beetle infestation can be extremely destructive, which may cause honey bees to abscond and render colony infrastructure unusable. Due to the impacts small hive beetles have on honey bees, a wide variety of physical, cultural, and chemical control measures have been implemented to manage small hive beetle infestations. The use of insecticides to control small hive beetle populations is an emerging management tactic. Currently, very little genomic information exists on insecticide target sites in the small hive beetle. Therefore, the objective of this study is to utilize focused in silico comparative genomics approaches to identify and assess the potential insecticide sensitivity of the major insecticide target sites in the small hive beetle genome.ResultsNo previously described resistance mutations were identified in any orthologs of insecticide target sites. Alternative exon use and A-to-I RNA editing were absent in AtumSC1. The ryanodine receptor in small hive beetle (Atum_Ryr) was highly conserved and no previously described resistance mutations were identified. A total of 12 nAChR subunits were identified with similar alternative exon use in other insects. Alternative exon use and critical structural features of the GABA-gated chloride channel subunits (Atum_RDL, Atum_GRD, and Atum_LCCH3) were conserved. Five splice variants were found for the glutamate-gated chloride channel subunit. Exon 3c of Atum_GluCl may be a beetle-specific alternative exon. The co-occurrence of exons 9a and 9b in the pH-sensitive chloride channel (Atum_pHCl) is a unique combination that introduces sites of post-translational modification. The repertoire and alternative exon use for histamine-gated chloride channels (Atum-HisCl), octopamine (Atum_OctR) and tyramine receptors (Atum_TAR) were conserved.ConclusionsThe recently published small hive beetle genome likely serves as a reference for insecticide-susceptible versions of insecticide target sites. These comparative in silico studies are the first step in discovering targets that can be exploited for small hive beetle-specific control as well as tracking changes in the frequency of resistance alleles as part of a resistance monitoring program. Comparative toxicity alongside honey bees is required to verify these in silico predictions.

Within-Stand Distribution of Tree Mortality Caused by Mountain Pine Beetle, Dendroctonus ponderosae Hopkins.

The mountain pine beetle (MPB) (Dendroctonus ponderosae) is a bark beetle that attacks and kills ponderosa pine (Pinus ponderosa), among other pine species throughout the western conifer forests of the United States and Canada, particularly in dense stands comprising large trees. There is information on the stand conditions that the insect prefers. However, there is a paucity of information on how small-scale variation in stand conditions influences the distribution of tree mortality within a stand. I examined the small-scale distribution of ponderosa pine basal area pre- and post a mountain pine beetle infestation, and used geostatistical modeling to relate the spatial distribution of the host to subsequent MPB-caused tree mortality. Results indicated increased mortality in the denser parts of the stand. Previous land management has changed historically open low-elevation ponderosa pine stands with aggregated tree distribution into dense stands that are susceptible to mountain pine beetles and intense fires. Current restoration efforts are aimed at reducing tree density and leaving clumps of trees, which are more similar to historical conditions. The residual clumps, however, may be susceptible to mountain pine beetle populations. Land managers will want to be cognizant of how mountain pine beetles will respond to restoration treatments, so as to prevent and mitigate tree mortality that could negate restoration efforts.

Snagfall the first decade after severe bark beetle infestation of high-elevation forests in Colorado, USA.

The persistence and fall rate of snags (standing dead trees) generated during bark beetle outbreaks have consequences for the behavior, effects, and suppression of potential wildfires, hazard tree and timber salvage operations, wildlife habitat, and numerous ecosystem processes. However, post-beetle snagfall dynamics are poorly understood in most forest types. We tagged standing live and dead lodgepole pine (Pinus contorta), subalpine fir (Abies lasiocarpa), and Engelmann spruce (Picea engelmannii), including beetle-killed pine snags following the peak of a recent mountain pine bark beetle outbreak in watersheds at the Fraser Experimental Forest in northcentral Colorado and sampled snagfall 10 and 12 years later. Bark beetle attacks began in 2003, peaked by 2006, and killed 78% of overstory lodgepole pine in 133 plots distributed across a range of stand and site conditions. Of those snags, only 17% fell between 2007 and 2018. Most snags broke at ground level, due to butt rot, and were oriented downhill. In contrast, snags that tipped up or snapped off above the ground were oriented with the prevailing winds. Equal numbers of snags fell singly and in multiple-tree groups, and equal numbers remained elevated rather than in contact with the ground. Lodgepole pine snagfall was 1.6-times higher on steep slopes (>40%) where dead pine density was higher, compared to flatter sites. Based on our findings and previous research, we estimate that one-half the beetle-killed lodgepole pine in high-elevation forests such as those at Fraser may fall within 15-20yr of beetle infestation, but that some pine snags are likely to persist for decades longer. Post-outbreak snagfall dynamics create a multiple-decade legacy of bark beetle outbreaks that will persist longer in high-elevation compared to lower-elevation forests.

Structural and Functional Dynamics of Soil Microbes following Spruce Beetle Infestation.

As the range of bark beetles expands into new forests and woodlands, the need to understand their effects on multiple trophic levels becomes increasingly important. To date, much attention has been paid to the aboveground processes affected by bark beetle infestation, with a focus on photoautotrophs and ecosystem level processes. However, indirect effects of bark beetle on belowground processes, especially the structure and function of soil microbiota remains largely a black box. Our study examined the impacts of bark beetle-induced tree mortality on soil microbial community structure and function using high-throughput sequencing of the soil bacterial and fungal communities and measurements of extracellular enzyme activities. The results suggest bark beetle infestation affected edaphic conditions through increased soil water content, pH, electrical conductivity, and carbon/nitrogen ratio and altered bulk and rhizosphere soil microbial community structure and function. Finally, increased enzymatic activity suggests heightened microbial decomposition following bark beetle infestation. With this increase in enzymatic activity, nutrients trapped in organic substrates may become accessible to seedlings and potentially alter the trajectory of forest regeneration. Our results indicate the need for incorporation of microbial processes into ecosystem level models.IMPORTANCE Belowground impacts of bark beetle infestation have not been explored as thoroughly as their aboveground counterparts. In order to accurately model impacts of bark beetle-induced tree mortality on carbon and nutrient cycling and forest regeneration, the intricacies of soil microbial communities must be examined. In this study, we investigated the structure and function of soil bacterial and fungal communities following bark beetle infestation. Our results show bark beetle infestation to impact soil conditions, as well as soil microbial community structure and function.

Influence of selected habitat and stand factors on bark beetle Ips typographus (L.) outbreak in the Białowieża Forest

The European spruce bark beetle (Ips typographus L.) is one of the most critical insect disturbance agents in Europe. In recent years, bark beetles have caused tremendous economic losses, and affected ecosystems over large spatial scales. In this study, we evaluated the influence of selected factors on the bark beetle outbreak in 2015, the year with the most severe drought to have been recorded in the last few decades. The main aim of this study was to develop a new approach of identifying and mapping individual trees infested by bark beetles, for more efficient bark beetle management. The study was conducted on an area occupying 62,000 ha, using airborne laser scanning, multispectral imagery data, and digital forest maps.First, an individual dead tree detection method, based on remote sensing data, was developed, which allowed the quantification of the bark beetle outbreak at an individual tree level, with accurate information on the number and location of killed spruces. Then, topography, habitat, and single tree-based variables were used to examine their influence on tree mortality. Finally, a spatial hot-spot analysis of the outbreak, throughout the 62,000 ha of the Polish part of the Białowieża Forest, was performed.For the first time, we mapped the status of the spruce bark beetle outbreak across the Białowieża Forest, using the method developed in this study. 283,166 dead Norway spruce trees were detected in the study area, supporting the fact that the current bark beetle outbreak is the largest in this area since 1945. The number of dead spruces surrounding any given dead tree was the single most important predictor in all models, with a relative contribution of 35–79% depending on the neighbourhood analysed (radius from 0 to 2000 m). Crown closure and stand age, as well as the share of dead spruce and dominant tree species were found to be the most important predictors of the development of bark beetle infestation. The method developed in this study was evaluated and proved to be suitable for the monitoring and management of the ongoing insect outbreak.

Pest survey card on Polygraphus proximus

This pest survey card was prepared in the context of the EFSA mandate on plant pest surveillance (M-2017-0137) at the request of the European Commission. Its purpose is to assist the Member States in preparing their survey activities for Polygraphus proximusBlandford (Coleoptera: Scolytidae) using a statistically sound and risk-based pest survey approach. Polygraphus proximus is a quarantine species in the EU, which has been introduced from east Asia into both Siberia and central European Russia. The species is a vector for pathogenic fungi that kills fir trees and is a threat to fir stands and other conifers in Europe. In the areas of recent introduction this insect pest species has had an impact of unprecedented severity on Abies forest stands. Detection surveys should combine visual inspection of primary host plants for the presence of symptoms of bark beetle infestation in Abiesspp. However, other species of conifer should not be neglected in detection surveys. Forest stands, woodlands or areas of trees with firs, spruce or other conifers near wood storage facilities, sawmills, or transport hubs (ports, train stations) with frequent passage of imported wood should initially be targeted.

Früherkennung von Buchdruckerbefall dank Fern erkundung: Was ist schon möglich?

Early detection of bark beetle infestations by remote sensing: what is feasible today? Infestation by the Norway spruce (Picea abies) bark beetle (Ips typographus) in uniform forest stands of the high montane and subalpine stage is a major challenge for management. It is impossible to identify in time all susceptible or already infested spruces in the often steep terrain solely by terrestrial observations and to prevent the proliferation of the beetle. A time-saving, cost-effective and effective method for finding these spruces is necessary and remote sensing techniques appear promising. Therefore, we investigated the potential of hyperspectral remote sensing data for the early detection of stressed or infested spruces using a case study in the experimental forest of the Swiss Federal Institute of Technology Zurich (ETHZ) in Sedrun. The approach that we developed is based on a combination of field surveys, hyperspectral data, vegetation indices calculated from these and their classification into the three classes “dead”, “stressed” and “healthy” using Random Forests, a machine-learning approach. We demonstrate that stressed spruces can be identified with this approach, but it is not yet ready for operational use. In particular, a slope-specific calibration of the method is necessary, which makes practical application impossible.

Contrasting patterns of natural mortality in primary Picea forests of the Carpathian Mountains

Mortality, driven by both climate and disturbance legacies, is a key process shaping forest dynamics. Understanding the mortality patterns in primary forests in the absence of severe disturbances provides information on background natural dynamics of a given forest type under ongoing climate change. This can then be compared to mortality rates in severely-disturbed stands. Using a large number of sample plots along a gradient from low to high disturbance, we examined the mortality rates and composition of mortality agents in primary mountain Norway spruce (Picea abies (L.) Karst.) forests on different spatial scales. We evaluated the mortality rates and causes of mortality in 28 stands across a large geographical gradient spanning over 1000 km. We resampled (five-year period) 371 plots (16,287 living trees) in primary Norway spruce forests along the Carpathian mountain chain. The estimated overall annual mortality rate was within the previously reported range of background (ambient) mortality, however, stand-level and plot-level mortality rates varied substantially. Over 18% of plots displayed more than 2% annual mortality and 6% of plots even exceeded 10% per year. Stands in the Western Carpathians showed the highest variability in the mortality rate, with 30% of the stands in this region showing annual mortality rates over 5%. At the plot level, mixed-severity disturbances increased variability of mortality rates within most localities. Overall mortality was evenly distributed among size classes up to 50 cm diameter at breast height (DBH). However, the distributions differ for individual mortality agents. Mortality modes were classified into six categories (broken crown, broken stem, uprooted, competition, bark beetle/fungi, climatic extremes). Bark beetle (Ips typographus L.) infestation was the most frequent mortality agent in all stands, whereas the influence of competition as a mortality agent varied substantially. Mortality from abiotically-caused physical damage was similar to that from competition, yet the distribution among modes of physical damage (uprooted, crown, or stem breakage) varied. The lack of clear evidence of mortality agents in some locations implies that many tree deaths are caused by a combination of contributing factors. The results suggest the role of bark beetle as a mortality agent does not equate to severe mortality at large scales. Prevalence of different size classes affected by individual mortality agents underline the high complexity of the mortality process in primary forests.

Conceptualizing data‐deliberation: The starry sky beetle, environmental system risk, and Habermasian CSR in the digital age

Building on an illustrative case of a systemic environmental threat and its multi‐stakeholder response, this paper draws attention to the changing political impacts of corporations in the digital age. Political Corporate Social Responsibility (PCSR) theory suggests an expanded sense of politics and corporations, including impacts that may range from voluntary initiatives to overcome governance gaps, to avoiding state regulation via corporate political activity. Considering digitalization as a stimulus, we explore potential responsibilities of corporations toward public goods in contexts with functioning governments. We show that digitalization—in the form of transparency, surveillance, and data‐sharing—offers corporations’ scope for deliberative public participation. The starry sky beetle infestation endangering public and private goods is thereby used to illustrate the possibility of expanding the political role of corporations in the digital sphere. We offer a contribution by conceptualizing data‐deliberation as a Habermasian variation of PCSR, defined as the (a) voluntary disclosure of corporate data and its transparent, open sharing with the public sector (b) along with the cooperation with governmental institutions on data analytics methods for examining large‐scale datasets (c) thereby complying with existing national and international regulations on data protection, in particular with respect to privacy and personal data.

Relationships among wood-boring beetles, fungi, and the decomposition of forest biomass.

A prevailing paradigm in forest ecology is that wood-boring beetles facilitate wood decay and carbon cycling, but empirical tests have yielded mixed results. We experimentally determined the effects of wood borers on fungal community assembly and wood decay within pine trunks in the southeastern United States. Pine trunks were made either beetle-accessible or inaccessible. Fungal communities were compared using culturing and high-throughput amplicon sequencing (HTAS)of DNA and RNA. Prior to beetle infestation, living pines had diverse fungal endophyte communities. Endophytes were displaced by beetle-associated fungi in beetle-accessible trees, whereas some endophytes persisted as saprotrophs in beetle-excluded trees. Beetles increased fungal diversity several fold. Over forty taxa of Ascomycota were significantly associated with beetles, but beetles were not consistently associated with any known wood-decaying fungi. Instead, increasing ambrosia beetle infestations caused reduced decay, consistent with previous in vitro experiments that showed beetle-associated fungi reduce decay rates by competing with decay fungi. No effect of bark-inhabiting beetles on decay was detected. Platypodines carried significantly more fungal taxa than scolytines. Molecular results were validated by synthetic and biological mock communities and were consistent across methodologies. RNA sequencing confirmed that beetle-associated fungi were biologically active in the wood. Metabarcode sequencing of the LSU/28S marker recovered important fungal symbionts that were missed by ITS2, though community-level effects were similar between markers. In contrast to the current paradigm, our results indicate ambrosia beetles introduce diverse fungal communities that do not extensively decay wood, but instead reduce decay rates by competing with wood decay fungi.

Is salvage logging effectively dampening bark beetle outbreaks and preserving forest carbon stocks?

Abstract Salvage logging is one of most frequently applied management responses to forest disturbances world‐wide. As forest disturbances are increasing, so too is the application of salvage logging, yet its effects on ecosystems remains incompletely understood. In the Norway spruce (Picea abies (L.) Karst.) forests of Europe, salvaging of windfelled trees is inter alia applied to reduce the risk of bark beetle outbreaks (mainly Ips typographus L.). By preventing further disturbances, salvage logging can conserve live tree carbon (C) in forest landscapes. At the same time salvage logging reduces C stocks in detrital pools via the extraction of disturbed trees, its net effect thus remains unclear. We used the forest landscape model iLand to explore the effect of a wide range of salvaging intensities on (a) subsequent bark beetle outbreaks, and (b) landscape‐scale forest C stocks in a Norway spruce‐dominated production forest in Slovakia under past and future climatic conditions. Climate change resulted in a two‐ to three‐fold increase in bark beetle disturbances throughout the 21st century in our simulations. We found that removing >95% of disturbed trees can effectively buffer the effect of increasing disturbances, dampening bark beetle infestations and increasing live tree C. Total ecosystem C followed a U‐shaped pattern over salvaging intensity, with highest values in no salvage and 100% salvage scenarios. However, realistic rates of salvaging (<95% of disturbed trees detected and removed) had no significant effect on bark beetle dynamics and live tree C, and reduced the total ecosystem C stored in the landscape. Furthermore, the effect of reduced bark beetle disturbance under intensive salvaging was partly offset by increased wind disturbance. Synthesis and applications. Clearing disturbed areas to prevent future disturbances from bark beetles and conserve live tree carbon should only be applied where very high salvaging rates are feasible (i.e. small and concentrated disturbances). Considering that changing disturbance regimes make high‐intensity salvaging increasingly challenging, alternative disturbance management approaches need to be developed.

Juvenile thinning can effectively mitigate the effects of drought on tree growth and water consumption in a young Pinus contorta stand in the interior of British Columbia, Canada

Large-scale forest disturbances including mountain pine beetle infestation and forest fires have generated overstocked lodgepole pine stands in the interior of British Columbia. A critical need is to determine sustainable management strategies to ensure their healthy growth and provision of various ecological functions under increased drought risk due to climate change. In 2016, a field experiment was established to study the effects of juvenile thinning on carbon assimilation and water use at the both tree- and stand-scales in a 16-year old lodgepole pine stand from June to October in 2016 and 2017. This study located northeast of Penticton, British Columbia, included two thinning treatments (T1: 4500 stems per ha; and T2: 1100 stems per ha) and one control (C: 27,000 stems per ha), randomly assigned in three blocks. Sap flow and microclimatic variables were continuously monitered in one plot of each treatment in one block, while tree diameter at breast height were measured across the three blocks. The results showed that C had the lowest tree radial growth (0.14 mm2/d), sap flow velocity (64.61 g/cm2d), and highest stand transpiration (4.36 mm/d), while T2 had the highest tree radial growth (1.28 mm2/d), sap flow velocity (149.14 g/cm2d), and lowest stand transpiration (0.36 mm/d) over the two-year study period. Significant differences of tree radial growth and sap flow velocity between T1 and T2 only occurred under the drought condition (in the summer season of 2017), with T2 having a significant higher resistant index of sap flow velocity than C and T1, by taking advantage of the change in microclimatic conditions following intense thinning. At the stand-level, only the stand transpiration of T1 statistically decreased in the drought year. We conclude that the thinning plays a significant and positive role in maintaining tree growth and water consumption in the short term, and the more heavily thinning (T2) would be more effective to mitigate the drought effect in young overstocking lodgepole pine forests in terms of water consumption. These findings improve our understanding on how thinning can be used to manage ecological responses to forest practices in a changing climate.

A quantitative approach for assessing bark beetle infestations: A study of Pityokteines spinidens Reitt. egg gallery densities in windthrown Abies alba Mill.

Abstract The presented statistical method enables monitoring of bark beetles that colonise different parts of the windthrown tree stem at different densities. The bark beetle, Pityokteines spinidens Reitt. occurring in forests with the fir Abies alba Mill. was used as an example. We propose a three-step statistical procedure. In the first step, a hierarchical cluster analysis (HCA), the single gamma function, and the gamma mixture distributions are used to model the distribution of egg galleries of P. spinidens along an A. alba windthrown stem. In the second step, a generalised linear model (GLM) and a generalised additive model (GAM) are employed to analyse the relationships between the number of P. spinidens egg galleries in selected stem sections and the total P. spinidens egg gallery density on the entire A. alba windthrown stem. In the third step, the mean total P. spinidens egg gallery density in the investigated area is estimated using survey sampling with simple random sampling without replacement (SRSWOR). The first and second steps allow us to identify which sections of the A. alba windthrown stem should be evaluated to adequately estimate the total egg gallery density (to save time and money and to reduce the amount of debarking performed per tree). The third step enables the calculation of the estimated relative standard error (to analyse the precision of the proposed method). Data were collected between 1994 and 2003 (data set D1) and in 2014 (data set D2) in forests including A. alba in the Świetokrzyski National Park, Poland. D1 was used to build the GLM and GAM, while D2 was employed to validate the models and to illustrate the proposed method. Six main types of egg gallery distributions along the stem were distinguished. P. spinidens inhabited all parts of the stem of A. alba windthrowns. Validation of the models suggested that the GAM performed better than the GLM. The predicted and observed data were closely consistent. This statistical evaluation of P. spinidens egg gallery densities will aid in the assessment of the ecological roles played by this species in A. alba ecosystems. Similar statistical approaches can be developed for other bark beetles colonising tree stems.

Biological beetle small cell (Aethina tumida: Nitidulidae: Coleoptera )

Small hive beetle (SHB) Aethina tumida (Order Coleoptera، Family Nitidulidae ) is an exotic pest of honeybee colonies، native to Sub-Saharan Africa. It has been found in several of the world over the past few decades. Adults are small، their color ranges from reddish-brown to dark brown (almost black) ، and its life cycle passes through four stages، egg، larva and adult after pupping period in the soil. The beetles are attracted to a number of odors from bee colonies، and can multiply to huge numbers within infested colonies where it eat brood، honey and pollen. In certain conditions، the (SHB) destroys combs and cause comb damage and honey spoilage through feeding and defecation. If beetle infestation is very high and uncontrolled، they ultimately destroy colonies or cause them to abscond.

Impacts Of The Invasive FourEyed Fir Bark Beetle (Polygraphus Proximus Blandf.) On Siberian Fir (Abies Sibirica Ledeb.) Forests In Southern Siberia

The emergence and spread of non-native invasive forest insects represent a major potential threat to global biodiversity. The present study examines the current invasion of the far eastern four-eyed fir bark beetle Polygraphus proximus Blandf. in southern Siberian fir (Abies sibirica Ledeb.) forests. We collected data on 38 large sized (2500 m²) sample plots, situated in fir forests of the Tomsk region. As a direct result of the four-eyed fir bark beetle infestation, stand density decreased by 34-37%, and stand volume by 30%. The mean height, individual age and diameter at the stand level consequently increased. Our results indicated that stands with complete left-sided or normal ontogenetic structure (composed primarily of late virginal firs or firs in young reproductive stage) are more resistant to invasion by the four-eyed fir bark beetle. By contrast, fir forests characterized by more right-sided ontogenetic structure (composed primarily of mature and old reproductive firs), exhibited the least resistance and, with rare exception, degraded rapidly in response to the invasion. Our results also pointed to a mechanism that initiates invasions of the four-eyed fir bark beetle in fir stands of all types of ontogenetic structure, which is the attack of virginal trees and trees in early reproductive stages. Trees up to average diameter are the most susceptible to invasions of the bark beetle. We identified thicker bark, larger DBH and low occurrence of heart rot as the most important parameters for indicating resistance at the single tree level. DBH and bark thickness (p<0.05) correlated significantly with tree health status in infested stands. Our overall assessment of the potential natural regeneration of damaged stands is that the Siberian fir forests are resilient to invasive species and that the fir ecosystems can potentially recover from this disturbance.