Beetle Infestation Research Articles

Integrating Neighborhood Effect and Supervised Machine Learning Techniques to Model and Simulate Forest Insect Outbreaks in British Columbia, Canada

Background and Objectives: Modelling and simulation of forest land cover change due to epidemic insect outbreaks are powerful tools that can be used in planning and preparing strategies for forest management. In this study, we propose an integrative approach to model land cover changes at a provincial level, using as a study case the simulation of the spatiotemporal dynamics of mountain pine beetle (MPB) infestation over the lodgepole pine forest of British Columbia (BC), Canada. This paper aims to simulate land cover change by applying supervised machine learning techniques to maps of MPB-driven deforestation. Materials and Methods: We used a 16-year series (1999–2014) of spatial information on annual mortality of pine trees due to MPB attacks, provided by the BC Ministry of Forests. We used elevation, aspect, slope, ruggedness, and weighted neighborhood of infestation as predictors. We implemented (a) generalized linear regression (GLM), and (b) random forest (RF) algorithms to simulate forestland cover changes due to MPB between 2005 and 2014. To optimize the ability of our models to predict MPB infestation in 2020, a cross-validation procedure was implemented. Results: Simulating infestations from 2008 to 2014, RF algorithms produced less error than GLM. Our simulations for the year 2020 confirmed the predictions from the BC Ministry of Forest by forecasting a slower rate of spread in future MPB infestations in the province. Conclusions: Integrating neighborhood effects as variables in model calibration allows spatiotemporal complexities to be simulated.

Tree Species Classification and Health Status Assessment for a Mixed Broadleaf-Conifer Forest with UAS Multispectral Imaging

Automatic discrimination of tree species and identification of physiological stress imposed on forest trees by biotic factors from unmanned aerial systems (UAS) offers substantial advantages in forest management practices. In this study, we aimed to develop a novel workflow for facilitating tree species classification and the detection of healthy, unhealthy, and dead trees caused by bark beetle infestation using ultra-high resolution 5-band UAS bi-temporal aerial imagery in the Czech Republic. The study is divided into two steps. We initially classified the tree type, either as broadleaf or conifer, and we then classified trees according to the tree type and health status, and subgroups were created to further classify trees (detailed classification). Photogrammetric processed datasets achieved by the use of structure-from-motion (SfM) imaging technique, where resulting digital terrain models (DTMs), digital surface models (DSMs), and orthophotos with a resolution of 0.05 m were utilized as input for canopy spectral analysis, as well as texture analysis (TA). For the spectral analysis, nine vegetation indices (VIs) were applied to evaluate the amount of vegetation cover change of canopy surface between the two seasons, spring and summer of 2019. Moreover, 13 TA variables, including Mean, Variance, Entropy, Contrast, Heterogeneity, Homogeneity, Angular Second Moment, Correlation, Gray-level Difference Vector (GLDV) Angular Second Moment, GLDV Entropy, GLDV Mean, GLDV Contrast, and Inverse Difference, were estimated for the extraction of canopy surface texture. Further, we used the support vector machine (SVM) algorithm to conduct a detailed classification of tree species and health status. Our results highlighted the efficiency of the proposed method for tree species classification with an overall accuracy (OA) of 81.18% (Kappa: 0.70) and health status assessment with an OA of 84.71% (Kappa: 0.66). While SVM proved to be a good classifier, the results also showed that a combination of VI and TA layers increased the OA by 4.24%, providing a new dimension of information derived from UAS platforms. These methods could be used to quickly evaluate large areas that have been impacted by biological disturbance agents for mapping and detection, tree inventory, and evaluating habitat conditions at relatively low costs.

Monitoring Bark Beetle Forest Damage in Central Europe. A Remote Sensing Approach Validated with Field Data

Over the last decades, climate change has triggered an increase in the frequency of spruce bark beetle (Ips typographus L.) in Central Europe. More than 50% of forests in the Czech Republic are seriously threatened by this pest, leading to high ecological and economic losses. The exponential increase of bark beetle infestation hinders the implementation of costly field campaigns to prevent and mitigate its effects. Remote sensing may help to overcome such limitations as it provides frequent and spatially continuous data on vegetation condition. Using Sentinel-2 images as main input, two models have been developed to test the ability of this data source to map bark beetle damage and severity. All models were based on a change detection approach, and required the generation of previous forest mask and dominant species maps. The first damage mapping model was developed for 2019 and 2020, and it was based on bi-temporal regressions in spruce areas to estimate forest vitality and bark beetle damage. A second model was developed for 2020 considering all forest area, but excluding clear-cuts and completely dead areas, in order to map only changes in stands dominated by alive trees. The three products were validated with in situ data. All the maps showed high accuracies (acc > 0.80). Accuracy was higher than 0.95 and F1-score was higher than 0.88 for areas with high severity, with omission errors under 0.09 in all cases. This confirmed the ability of all the models to detect bark beetle attack at the last phases. Areas with no damage or low severity showed more complex results. The no damage category yielded greater commission errors and relative bias (CEs = 0.30–0.42, relB = 0.42–0.51). The similar results obtained for 2020 leaving out clear-cuts and dead trees proved that the proposed methods could be used to help forest managers fight bark beetle pests. These biotic damage products based on Sentinel-2 can be set up for any location to derive regular forest vitality maps and inform of early damage.

Exploiting the full potential of Bayesian networks in predictive ecology

AbstractAlthough ecological models used to make predictions from underlying covariates have a record of success, they also suffer from limitations. They are typically unable to make predictions when the value of one or more covariates is missing during the testing. Missing values can be estimated but methods are often unreliable and can result in poor accuracy. Similarly, missing values during the training can hinder parameter estimation of many ecological models. Bayesian networks can handle these and other limiting issues, such as having highly correlated covariates. However, they are rarely used to their full potential.Indeed, Bayesian networks are commonly used to evaluate the knowledge of experts by constructing the network manually and often (incorrectly) interpreting the resulting network causally. We provide an approach to learn a Bayesian network fully from observed data, without relying on experts and show how to appropriately interpret the resulting network, both to identify how the variables (covariates and target) are interrelated and to answer probabilistic queries.We apply this method to the case study of a mountain pine beetle infestation and find that the trained Bayesian network has a predictive accuracy of 0.88 AUC. We classify the covariates as primary and secondary in terms of contributing to the prediction and show that the predictive accuracy does not deteriorate when the secondary covariates are missing and degrades to only 0.76 when one of the primary covariates is missing.As a complement to the previous work on constructing Bayesian networks by hand, we show that if instead, both the structure and parameters are learned only from data, we can achieve more accurate predictions as well as generate new insights about the underlying processes.

Consequences of Climate Change-Induced Habitat Conversions on Red Wood Ants in a Central European Mountain: A Case Study.

Simple SummaryThe red wood ants are considered to be one of the main ecosystem engineers and keystone species of the habitats in which they exist. Most of the species from this species group inhabit coniferous forests, which, due to the consequences of anthropogenic climate change, are continuously cut down. Therefore, the main habitat of these important species is rapidly disappearing. We investigated the consequences of the absence of conifers (clear-cut area and deciduous forest) on one of the members of this species group, namely Formica polyctena. We have found that compared with the mixed-coniferous forest stand, the absence of coniferous species resulted in significant changes in the colony and nest structure of F. polyctena. In addition, the colony size was also smaller in these sites. These changes suggest that although F. polyctena is able to survive in suboptimal habitats, still their population decline is expected and urges conservation managers to apply necessary action plans for their protection.The consequences of anthropogenic climate change are one of the major concerns of conservation biology. A cascade of negative effects is expected to affect various ecosystems, one of which is Central European coniferous forests and their unique biota. These coniferous forests are the primary habitat of many forest specialist species such as red wood ants. Climate change-induced rising of temperature allows trees to skip winter hibernation, making them more vulnerable to storms that cause wind felling, and in turn, promotes bark beetle infestations that results in unscheduled clear-cuttings. Red wood ants can also be exposed to such habitat changes. We investigated the effects of bark beetle-induced clear-cutting and the absence of coniferous trees on colonies of Formica polyctena, including a mixed-coniferous forest as a reference. Our aim was to investigate how these habitat features affect the nest characteristics and nesting habits of F. polyctena. Our results indicate that, in the absence of conifers, F. polyctena tend to use different alternatives for nest material, colony structure, and food sources. However, the vitality of F. polyctena colonies significantly decreased (smaller nest mound volumes). Our study highlights the ecological flexibility of this forest specialist and its potential to survive under extreme conditions.

Out of Africa: novel source of small hive beetles infesting Eastern and Western honey bee colonies in China

Small hive beetles (SHB, Aethina tumida Murray, Coleoptera: Nitidulidae) are parasites of social bee colonies endemic to sub-Saharan Africa and have become an invasive species. Even though the global spread of SHB seems inevitable, the origin of novel introductions and their impact on new host populations need to be investigated to foster mitigation. Here, we report a case of SHBs from China and use COI gene sequencing to trace their origin. Since July 2018, beetle infestations of Eastern (Apis cerana) and Western (Apis mellifera) honey bee colonies with clinical symptoms were repeatedly reported from two Chinese provinces. These infestations apparently had a severe impact on A. cerana. Using morphometrics, genetics and clinical symptoms in the field, the beetles were confirmed to be A. tumida. The DNA sequences suggest an introduction from a yet unidentified African source similar to the Philippines, but very different to any other previously reported SHB haplotypes. The establishment of SHB in China underlines the need to limit novel introductions. Given that Eastern honey bees and possibly other Apis spp. are susceptible to SHB infestations, our findings highlight the need for adequate protection measures of endemic Asian honey bees.

Indirect biogeomorphic and soil evolutionary effects of spruce bark beetle

Outbreaks of bark beetles, for example Ips typographus L. in Eurasia or Dendroctonus ponderosae Hopkins in North America, have serious impacts on forest resources, biodiversity, and ecological dynamics, with economical and social ramifications. Moreover, many models predict increasing frequency and severity of such biotic disturbances due to ongoing climate change, and land use driven changes in forest structure and composition. Bark beetles are recognized as keystone species due to their strong and complex effects on ecosystem dynamics. However, due to the increasingly widely recognized biogeomorphic impacts of trees, bark beetles may have significant indirect biogeomorphic and pedogenetic impacts through their effects at scales ranging from individual trees to forest landscapes. These include: (1) Reduced uprooting, with associated impacts on topography, mass movements, regolith and soil formation, and slope hydrology; (2) Reductions in bioprotection via trapping of downslope sediment movement; (3) Hydrological impacts, including increased total runoff and increased proportion of subsurface flow; (4) Decreased microtopographic irregularity (and associated hydrological and pedological impacts); and (5) Changes in biochemical and biomechanical effects on soils, regolith, and hillslope morphology. Five separator factors (discriminators between different developmental trajectories) were revealed for the case of the central European region. These factors may determine the occurrence and severity of biogeomorphic impacts: First is whether the site is prone to potential uprooting or whether an spruce bark beetle (SBB) outbreak is initiated by a blowdown/uprooting event. Second is whether the site is dominated by mineral soils or Histosols. A third discriminating factor is whether the forest is managed or unmanaged, which determines the pre-attack tree species composition and coarse woody debris and disturbance regimes; and a fourth is the post-outbreak management. Finally, the fifth separator factor relates to slope thresholds that determine the significance of impacts on mass movements and erosion. These findings support the need, and provide guidelines, for research on geomorphic impacts of bark beetle infestations. Though we mainly restrict our consideration to bark beetles in Europe, both our approach and findings are likely to have broader relevance for biogeomorphic impacts of extensive tree mortality. • Spruce bark beetles (SBB) influence various geomorphic and pedogenetic processes. • SBB influence soils and hillslope dynamics from local scale of tree to landscape scale. • Five separator factors may determine the occurrence and severity of SBB impacts. • Findings have broader relevance for geomorphic impacts of other biotic disturbances.

Genetic Architecture of Cereal Leaf Beetle Resistance in Wheat.

Wheat production can be severely damaged by endemic and invasive insect pests. Here, we investigated resistance to cereal leaf beetle in a panel of 876 winter wheat cultivars, and dissected the genetic architecture underlying this insect resistance by association mapping. We observed an effect of heading date on cereal leaf beetle infestation, with earlier heading cultivars being more heavily infested. Flag leaf glaucousness was also found to be correlated with resistance. In line with the strong effect of heading time, we identified Ppd-D1 as a major quantitative trait locus (QTL), explaining 35% of the genotypic variance of cereal leaf beetle resistance. The other identified putative QTL explained much less of the genotypic variance, suggesting a genetic architecture with many small-effect QTL, which was corroborated by a genomic prediction approach. Collectively, our results add to our understanding of the genetic control underlying insect resistances in small-grain cereals.

Storage of chickpea grains (Cicer arietinum L.) in triple layer bags prevent losses caused by Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae) under laboratory conditions

Present study envisages the potential of triple layer bags for reducing pulse beetle infestation under laboratory conditions over six months of storage. It was observed that when chickpea grain was stored in jute bags with bruchid infestation, the germination percentage decreased significantly from 84.67 to 18.67% in six months of storage. But, the grain stored in jute bags without infestation the germination percentage decreased from 92.00 to 73.33% only. On the other hand, grains stored in triple layer bags with bruchid infestation, the germination percentage merely decreased from 86.00 to 78.33% in six months of storage and triple layer bags without infestation the germination percentage only decreased from 91.67 to 90.67%. The per cent grain damage over a period of six months storage also increased significantly from 14.54 to 70.67% and 0.00–26.45% in jute bag with bruchid infestation and jute bag without infestation, respectively. However, per cent grain damage in triple layer bags with bruchid infestation increased only from 15.15 to 25.70% and triple layer bags without bruchid infestation showed negligible increase from 0.00 to 2.64% grain damage in six months of storage. The corresponding per cent weight loss of infested grain was increased significantly from 8.51 to 55.67% in six months of storage in jute bag with bruchid infestation and from 0.00 to 15.08% in jute bag without infestation. Whereas, per cent weight loss of infested grain in triple layer bags with bruchid infestation increased only from 7.83 to 15.70 in six months of storage and triple layer bags without bruchid infestation recorded a mere per cent increase in weight loss from 0.00 to 1.48%. Benefit cost ratio showed that grains stored in triple layer bags for 6 months has highest benefit cost ratio (1.23) compared to jute bag storage (0.39).

Habitat and stand factors related to spatial dynamics of Norway spruce dieback driven by Ips typographus (L.) in the Białowieża Forest District

Among the complex tasks involved in forest protection, one of the most laborious is dealing with tree mortality caused by forest pests. The European spruce bark beetle, which settles primarily on spruces, causes major damages in temperate and boreal forests. To manage forest activities more accurately during outbreaks, robust models are needed to understand how a given phenomenon expands.Our study examines spruce dieback dynamics in a 13,000-ha area of the Białowieża Forest in Białowieża Forest District in Poland, using individual trees assigned to a 100 × 100 m resolution grid based on data from 2015 and 2017. To find the most important factors affecting bark beetle outbreaks, two different approaches were applied. In the first approach, we conducted spatial hot-spot analyses by means of global and local Moran's coefficients. In the second one, we used a machine learning technique, i.e. boosted regression trees (BRTs).Both approaches allowed us to identify the share of area covered by tree crowns excluding spruce, stand height, and share of spruce as the key factors for bark beetle infestation. It means, that the most intensive outbreak progressed in old stands dominated by spruces. Proposed methodology of spatial analysis allowed to discover potential initiation points of beetle-caused tree mortality, localized in more opened old stands and indicate the most outbreak-resistant areas with young trees less than 90 years old. Methods and results presented in this study serve as baseline information, supporting the efforts to model the spread of bark beetle dynamics and future decision-making.

Scientific note on small hive beetle infestation of stingless bee (Tetragonula carbonaria) colony following a heat wave

We present the first study of infestation by the small hive beetle, Aethina tumida, in a queenright colony of the stingless bee Tetragonula carbonaria, a species used for pollination services. Nine managed hives were deployed outside the bee’s endemic range. After 2 months, including a heat wave of four consecutive days above 40 °C, one colony was visibly weakened with fewer foragers. This hive was removed from the site for the colony to recover. After a second heat wave, another colony was found weakened and infested with small hive beetle (SHB). Inside the hive, 14 adults and 133 larvae of SHB were discovered. Extreme daily maximum temperatures and low humidity appear to have weakened this colony. Our study highlights the need for careful placement of managed hives, as the SHB has potential to be a significant pest of stingless bees under adverse conditions.

Reducing rotation age to address increasing disturbances in Central Europe: Potential and limitations

Forest disturbance regimes are intensifying in many parts of the globe. In order to mitigate disturbance impacts a number of management responses have been proposed, yet their effectiveness in addressing changing disturbance regimes remains largely unknown. The strong positive relationship between forest age and the vulnerability to disturbances such as windthrows and bark beetle infestations suggests that a reduced rotation length can be a potent means for mitigating the impacts of natural disturbances. However, disturbance mitigation measures such as shortened rotation lengths (SRL) can also have undesired consequences on ecosystem services and biodiversity, which need to be considered in their application.Here, we used the process-based landscape and disturbance model iLand to investigate the effects of SRL on the vulnerability of a 16,000 ha forest landscape in Central Europe to wind and bark beetle disturbances. We experimentally reduced the current rotation length (between 100 and 115 years) by up to −40% in 10% increments, and studied effects on disturbance dynamics under current and future climate conditions over a 200-year simulation period. Simultaneously, we quantified the collateral effects of SRL on forest carbon stocks and indicators of biodiversity. Shortening the rotation length by 40% decreased disturbances by 14%. This effect was strongly diminished under future climate change, reducing the mitigating effect of shortened rotation to <6%. Collateral effects were severe in the initial decades after implementation: Reducing the rotation length by 40% caused a spike in harvested timber volume (+92%), decreased total forest carbon storage by 6% and reduced the number of large trees on the landscape by 20%. The long-term effects of SRL were less pronounced. At the same time, SRL caused an increase in tree species diversity. Shortening rotation length can reduce the impact of wind and bark beetle disturbances, but the overall efficiency of the measure is limited and decreases under climate change. Given the potential for undesired collateral effects we conclude that a reduction of the rotation length is no panacea for managing increasing disturbances, and should be applied in combination with other management measures reducing risks and fostering resilience.

Studi Bioekologi Parasitoid Tetrastichus brontispae Feer (Hymenopters : Eulophidae) Terhadap Hama Brontispa longissima Gestro (Coleoptera:Chrysomelidae)

In recent years, the coconut leaf beetle (Brontispa longissima, Hymenopters: Eulophidae) has been a significant pest in Ende, Indonesia and has destroyed the majority of the coconut crop leading to overall production to decline. In 2007 coconut leaf beetle began being controlled biologically using the parasitoid Tetrastichus brontispae (Hymenopters: Eulophidae). This is now considered locally to be the most effective way to suppress pest populations of coconut leaf beetle but until now there have been no scientific studies on this biological pest control method. This study aims to determine the effectiveness of Tetratichus brontispae parasitoids as a treatment for coconut leaf beetle infestations. This research used a Completely Randomized Design (CRD), which was comprised of three types of experiments. First, the average coconut leaf beetle survival rate was measured when exposed to T. brontispae at five ratios: 1:1, 2:1, 3:1, 4:1, and 5:1. Researchers also measured the effect of Tetratichus brontispae treatment duration using 5treatments, namely: 24 hours, 48 hours, 72 hours, 96 hours, and 120 hours of repeated 10 times. 3) Observation of biological parameters of Tetratichus brontispae was conducted qualitatively. The results showed that treatment with the highest level of parasitization occurred at the ratio of 3:1, as much as 20.75% parasitization, and the lowest level parasitization effect occurred at a level of the 1:1 ratio, as low as 7.07%, with the highest percentage survivability of T. Brontispae occurring on the first day (6.48%) and the lowest on day five at 1.29%. On average, 98.13% of T. Brontispae specimens produced offspring, and an average of 32.71% of specimens gave birth each day. Tetratichus brontispae adults had an average life span of 9-11 days, had no pre- oviposition period with the oviposition period occurring until day five. Specimens would die an average of 6 days following oviposition.

A comparison of lodgepole and spruce needle chemistry impacts on terrestrial biogeochemical processes during isolated decomposition.

This study investigates the isolated decomposition of spruce and lodgepole conifer needles to enhance our understanding of how needle litter impacts near-surface terrestrial biogeochemical processes. Harvested needles were exported to a subalpine meadow to enable a discrete analysis of the decomposition processes over 2 years. Initial chemistry revealed the lodgepole needles to be less recalcitrant with a lower carbon to nitrogen (C:N) ratio. Total C and N fundamentally shifted within needle species over time with decreased C:N ratios for spruce and increased ratios for lodgepole. Differences in chemistry correlated with CO2 production and soil microbial communities. The most pronounced trends were associated with lodgepole needles in comparison to the spruce and needle-free controls. Increased organic carbon and nitrogen concentrations associated with needle presence in soil extractions further corroborate the results with clear biogeochemical signatures in association with needle chemistry. Interestingly, no clear differentiation was observed as a function of bark beetle impacted spruce needles vs those derived from healthy spruce trees despite initial differences in needle chemistry. These results reveal that the inherent chemistry associated with tree species has a greater impact on soil biogeochemical signatures during isolated needle decomposition. By extension, biogeochemical shifts associated with bark beetle infestation are likely driven more by changes such as the cessation of rhizospheric processes than by needle litter decomposition.

Carbon storage recovery in surviving lodgepole pine (Pinus contorta var. latifolia) 11 years after mountain pine beetle attack in northern British Columbia, Canada

We studied the recovery of tree- and stand-level carbon (C) storage in a lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) forest in northern British Columbia that experienced substantial (∼83%) mortality in 2006–2007 (total loss by 2013 = 86%) during a severe mountain pine beetle (MPB; Dendroctonus ponderosae Hopkins, 1902) infestation. Earlier work suggested that this forest recovered positive annual C storage 3 years after attack based on eddy covariance measurements. We sought to confirm these results by examining C storage in surviving pine trees using tree core analysis. Average growth release of surviving lodgepole pine trees was 392% (range of –53% to 2326%) compared with mean decadal growth prior to MPB attack. Nearly 97% of trees underwent a growth release, considerably higher than the 15%–75% reported for lodgepole pine in previous studies. Mean annual stem C storage of the surviving trees in this study was highly correlated (r = 0.88) with 10 years of annual net ecosystem productivity estimates made using the eddy covariance technique, indicating that surviving lodgepole pine remain an important part of C recovery after MPB attack. Mean annual stem C storage was also highly correlated (r = 0.92) with the cumulative percentage of downed stems per hectare at the site, suggesting that increased availability of resources is likely assisting the growth release.

A Hierarchical Deep-Learning Approach for Rapid Windthrow Detection on PlanetScope and High-Resolution Aerial Image Data

Forest damage due to storms causes economic loss and requires a fast response to prevent further damage such as bark beetle infestations. By using Convolutional Neural Networks (CNNs) in conjunction with a GIS, we aim at completely streamlining the detection and mapping process for forest agencies. We developed and tested different CNNs for rapid windthrow detection based on PlanetScope satellite data and high-resolution aerial image data. Depending on the meteorological situation after the storm, PlanetScope data might be rapidly available due to its high temporal resolution, while the acquisition of high-resolution airborne data often takes weeks to a month and is, therefore, used in a second step for more detailed mapping. The study area is located in Bavaria, Germany (ca. 165 km2), and labels for damaged areas were provided by the Bavarian State Institute of Forestry (LWF). Modifications of a U-Net architecture were compared to other approaches using transfer learning (e.g., VGG19) to find the most efficient architecture for the task on both datasets while keeping the computational time low. A custom implementation of U-Net proved to be more accurate than transfer learning, especially on medium (3 m) resolution PlanetScope imagery (intersection over union score (IoU) 0.55) where transfer learning completely failed. Results for transfer learning based on VGG19 on high-resolution aerial image data are comparable to results from the custom U-Net architecture (IoU 0.76 vs. 0.73). When using both architectures on a dataset from a different area (located in Hesse, Germany), however, we find that the custom implementations have problems generalizing on aerial image data while VGG19 still detects most damage in these images. For PlanetScope data, VGG19 again fails while U-Net achieves reasonable mappings. Results highlight the potential of Deep Learning algorithms to detect damaged areas with an IoU of 0.73 on airborne data and 0.55 on Planet Dove data. The proposed workflow with complete integration into ArcGIS is well-suited for rapid first assessments after a storm event that allows for better planning of the flight campaign followed by detailed mapping in a second stage.

A bark beetle infestation predictive model based on satellite data in the frame of decision support system TANABBO

The European spruce bark beetle Ips typographus L. causes significant economic losses in managed coniferous forests in Central and Northern Europe. New infestations either occur in previously undisturbed forest stands (i.e., spot initiation) or depend on proximity to previous years’ infestations (i.e., spot spreading). Early identification of newly infested trees over the forested landscape limits the effective control measures. Accurate forecasting of the spread of bark beetle infestation is crucial to plan efficient sanitation felling of infested trees and prevent further propagation of beetle-induced tree mortality. We created a predictive model of subsequent year spot initiation and spot spreading within the TANABBO decision support system. The algorithm combines open-access Landsat-based vegetation change time-series data, a digital terrain model, and forest stand characteristics. We validated predicted susceptibility to bark beetle attack (separately for spot initiation and spot spreading) against beetle infestations in managed forests in the Bohemian Forest in the Czech Republic (Central Europe) in yearly time steps from 2007 to 2010. The predictive models of susceptibility to bark beetle attack had a high degree of reliability (area under the ROC curve - AUC: 0.75-0.82). We conclude that spot initiation and spot spreading prediction modules included within the TANABBO model have the potential to help forest managers to plan sanitation felling in managed forests under pressure of bark beetle outbreak.

Local-level emergence of network governance within the U.S. Forest Service: A case study of mountain pine beetle outbreak from Colorado, USA

In the U.S. and around the world, governmental and non-governmental actors are piloting network governance approaches to fill gaps in governance resources (management capacity, local legitimacy) that cannot be met by a single entity alone. Such resources are needed to respond adaptively to changing conditions, such as those posed by severe disturbance. The purpose of this study is to provide insight into the drivers, pathways, and outcomes of network governance emergence within a federal bureaucracy, that of the U.S. Forest Service. We aim to shed light on the local variability of emergent network types (partnerships, collaboratives, combination types). We conducted case study research on responses to a severe mountain pine beetle (MPB, Dendroctonus ponderosae Hopkins) infestation (~1996–2012) on the Arapaho and Roosevelt National Forests in northern Colorado, USA. We applied a multi-level analysis, comprised of bottom-up, top-down, and “from around” (pre-existing network) factors, to three examples of MPB outbreak-driven network emergence. The examples vary in their combination of geographic location (Western Slope vs. Front Range) and scale (local vs. regional). Our analysis revealed: (1) network type and governance outcomes varied due to interlinked, multi-level factors (predominant gaps in governance resources, bottom-up factors, and pre-existing networks); (2) USFS managers and counterparts exercised agency in navigating top-down bureaucratic constraints on network governance emergence; (3) state, local, industry, and NGO entities, along with federal counterparts, co-initiated network governance of federal lands; (4) emergent networks generally did not persist in the large bureaucracy after the aftermath subsided. This study's findings are applicable to governance networks associated with land management bureaucracies in the U.S. and around the world.

Reconstructing historical outbreaks of mountain pine beetle in lodgepole pine forests in the Colorado Front Range

Regional-scale mountain pine beetle (Dendroctonus ponderosae) outbreaks in the first decade of the 2000s affected millions of hectares of lodgepole pine (Pinus contorta) in western North American forests. In Colorado, 1.4 million ha exhibited high mortality. These events prompted questions about whether historical outbreaks reached the scale of this most recent event. We aimed to reconstruct past mortality events in lodgepole pine forests in the northern Colorado Front Range and to determine whether these were of similar extent to the 2000s outbreak. We identified logs of mountain pine beetle-killed trees based on visually identifiable signs of beetle infestation including lower bole breakage, egg galleries, exit holes, and the presence of blue stain. We collected cross-sections, developed tree ring chronologies and determined death dates through tree ring analysis. We detected five mortality events since the 1860s, including widely distributed mortality in the 1910s that was geographically as extensive as the 2000s outbreak in our study area. Trees killed were on average 232 years of age and 36 cm in diameter. In our study area, it takes about 200 years for a lodgepole pine to reach the size suitable for mountain pine beetle attack. We conclude that mountain pine beetle infestation signs remain useful for identifying mountain pine beetle-caused tree mortality for over a century and that well-distributed mountain pine beetle-caused mortality has occurred in the past in the northern Colorado Front Range. Future reconstructions of bark beetle-caused mortality may benefit from integrating the use of beetle symptomatology with growth releases. The inclusion of stand demography and fire history will present a holistic picture of how disturbance interactions create the mosaic of forest landscapes. Awareness of the disturbance histories in forests and the legacies of past events advances understanding of their ecology and will inform researchers and managers in developing management strategies to foster sustainable delivery of ecosystem services and maintain resiliency as climate change manifests.

Bark beetle infestation spots as biodiversity hotspots: Canopy gaps resulting from insect outbreaks enhance the species richness, diversity and abundance of birds breeding in coniferous forests

Natural disturbances are a major source of spatial stand heterogeneity, initiating forest community turnover. Besides large-scale events like fires, landslides or windthrows, small-scale canopy gaps resulting from the mortality of a single tree or a group of trees represent a distinct structure within a stand. Although the role of canopy gaps is well recognized in tropical ecosystems, the effect of small-scale openings on species richness, diversity and abundance has not been satisfactorily addressed in temperate forests. A specific example of a canopy gap is the bark beetle infestation spot, that is, a small group of trees that have died as a result of insect activity. We studied the effect of canopy gaps on the breeding bird assemblage in old-growth coniferous forests in the Tatra Mts. and Gorce Mts. (Carpathians, S Poland). Our hypothesis was that the gaps and the nearby closed-canopy forest would differ in species richness, diversity and relative abundance. We censused the breeding bird assemblages in 50 such gaps (median size 0.85 ha, quartile range 0.30–2.34 ha, range 0.03–10.0 ha) and 50 nearby closed-canopy reference plots using point counts. Almost 25% more bird species were recorded in the gaps than in the closed-canopy forest, and species richness correlated positively with the number of snags. The number of individual birds recorded in the gaps was 40% higher than in the closed-canopy forest and correlated positively with the number of fallen logs. Gap size was not correlated with the richness, diversity or relative abundance of species. Our results show that canopy gaps resulting from bark beetle outbreaks increase species richness, diversity and abundance by providing suitable habitats for cavity-nesting, ground-nesting and insectivorous birds. We suggest that by increasing habitat heterogeneity and enhancing food resources, even relatively small-scale canopy gaps improve the overall biodiversity of coniferous forests.