Bark Beetle Damage Research Articles

Remote sensing of bark beetle damage in urban forests at individual tree level using a novel hyperspectral camera from UAV and aircraft

Climate-related extended outbreaks and range shifts of destructive bark beetle species pose a serious threat to urban boreal forests in North America and Fennoscandia. Recent developments in low-cost remote sensing technologies offer an attractive means for early detection and management of environmental change. They are of great interest to the actors responsible for monitoring and managing forest health. The objective of this investigation was to develop, assess, and compare automated remote sensing procedures based on novel, low-cost hyperspectral imaging technology for the identification of bark beetle infestations at the individual tree level in urban forests. A hyperspectral camera based on a tunable Fabry-Pérot interferometer was operated from a small, unmanned airborne vehicle (UAV) platform and a small Cessna-type aircraft platform. This study compared aspects of using UAV datasets with a spatial extent of a few hectares (ha) and a ground sample distance (GSD) of 10–12 cm to the aircraft data covering areas of several km2 and having a GSD of 50 cm. An empirical assessment of the automated identification of mature Norway spruce (Picea abies L. Karst.) trees suffering from infestation (representing different colonization phases) by the European spruce bark beetle (Ips typographus L.) was carried out in the urban forests of Lahti, a city in southern Finland. Individual spruces were classified as healthy, infested, or dead. For the entire test area, the best aircraft data results for overall accuracy were 79% (Cohen’s kappa: 0.54) when using three crown color classes (green as healthy, yellow as infested, and gray as dead). For two color classes (healthy, dead) in the same area, the best overall accuracy was 93% (kappa: 0.77). The finer resolution UAV dataset provided better results, with an overall accuracy of 81% (kappa: 0.70), compared to the aircraft results of 73% (kappa: 0.56) in a smaller sub-area. The results showed that novel, low-cost remote sensing technologies based on individual tree analysis and calibrated remote sensing imagery offer great potential for affordable and timely assessments of the health condition of vulnerable urban forests.

Using UAV-Based Photogrammetry and Hyperspectral Imaging for Mapping Bark Beetle Damage at Tree-Level

Low-cost, miniaturized hyperspectral imaging technology is becoming available for small unmanned aerial vehicle (UAV) platforms. This technology can be efficient in carrying out small-area inspections of anomalous reflectance characteristics of trees at a very high level of detail. Increased frequency and intensity of insect induced forest disturbance has established a new demand for effective methods suitable in mapping and monitoring tasks. In this investigation, a novel miniaturized hyperspectral frame imaging sensor operating in the wavelength range of 500–900 nm was used to identify mature Norway spruce (Picea abies L. Karst.) trees suffering from infestation, representing a different outbreak phase, by the European spruce bark beetle (Ips typographus L.). We developed a new processing method for analyzing spectral characteristic for high spatial resolution photogrammetric and hyperspectral images in forested environments, as well as for identifying individual anomalous trees. The dense point clouds, measured using image matching, enabled detection of single trees with an accuracy of 74.7%. We classified the trees into classes of healthy, infested and dead, and the results were promising. The best results for the overall accuracy were 76% (Cohen’s kappa 0.60), when using three color classes (healthy, infested, dead). For two color classes (healthy, dead), the best overall accuracy was 90% (kappa 0.80). The survey methodology based on high-resolution hyperspectral imaging will be of a high practical value for forest health management, indicating a status of bark beetle outbreak in time.

Influence of climate on the growth of quaking aspen (Populus tremuloides) in Colorado and southern Wyoming

We analyzed a series of increment cores collected from 260 adult dominant or co-dominant quaking aspen (Populus tremuloides Michx.) trees from national forests across Colorado and southern Wyoming in 2009 and 2010. Half of the cores were collected from trees in stands with a high amount of crown dieback, and half were from lightly damaged stands. We define the level of stand damage based on stand survey data in which lightly damaged stands had average crown dieback of 16% and heavily damaged stands averaged 41%. Upon analysis, two-thirds of the cores collected did not exhibit radial growth correlated with region-wide patterns (e.g., climate) and were classified as having a low cohesive response. The site variable most predictive of whether a stand exhibited high cohesive response or low cohesive response was site elevation, followed by aspect, slope, and canopy closure. Sites with high cohesive response stands were more likely to have aspen bark beetle damage, white rot, and Cryptosphaeria canker. We did not detect relationships between tree growth and summer precipitation from 1900–2008, but there was a relationship between growth and annual precipitation. A growth model included maximum May and July temperatures, as well as the current and previous year’s annual precipitation.

Genetic variation and heritability estimates of Ulmus minor and Ulmus pumila hybrids for budburst, growth and tolerance to Ophiostoma novo-ulmi

Seedlings obtained by crossing Ulmus minor and U. minor × U. pumila clones were assessed for flowering, bark beetle damage, vegetative budburst, height growth and resistance to Ophiostoma novo-ulmi. Ramets and open pollinated seedlings obtained from the parent trees were assessed for the same traits. Most progenies had similar traits to their parents, but some presented heterosis in annual growth or resistance to O. novo-ulmi. Leaf wilting was significantly lower in progenies with U. minor × U. pumila rather than U. minor as female parent (21.5 and 30.6%, respectively; P<0.05). Resistance to O. novo-ulmi increased significantly as a function of increased amounts of U. pumila germplasm from the female parent, suggesting that resistance to Dutch elm disease is primarily transmitted from the mother. Budburst occurred earlier in seedlings with low rather than high growth rates (P=0.0007) and percentage of wilting was negatively related to early budburst (P<0.0001). Other phenotypic relations included percentage of flowering trees and annual height growth (rp=0.44; P=0.0042), percentage of flowering trees and vegetative budburst (rp=-0.53; P=0.0004) and percentage of beetle-affected trees and annual height growth (rp=0.60; P<0.0001). Heritability estimates obtained from the regression and variance components methods ranged from 0.06 ± 0.04 to 0.64 ± 0.18, 0.10 ± 0.05 to 0.69 ± 0.17, and 0.13 ± 0.32 to 0.71 ± 0.22 for budburst, growth and tolerance to O. novo-ulmi, respectively. Broad- and narrow-sense heritability values were higher when estimated 60 days post inoculation (dpi) than 15, 30 or 120 dpi. Heritability estimates and genetic gains reported indicate a high degree of additive genetic control and show the effectiveness of selection for Dutch elm disease resistance and rapid tree growth.

Bark beetle pests in an altitudinal gradient of a Mexican managed forest

Global climate change is having multiple effects upon plant populations. In recent years, conifers in the northern hemisphere have experienced increased bark beetle damage, particularly at the limits of their distribution. In this project, we investigated bark beetle populations and insect damage in Pinus trees along an altitudinal gradient in order to obtain an overview of damage at regional level, and also to analyze the consequences of rising temperatures on insect damage in trees. The study was conducted in the communal pine forests of Nuevo San Juan Parangaricutiro in the state of Michoacán, Mexico. In September 2011, 32 Lindgren traps were hung along an altitudinal gradient from 2200 to 2750m a.s.l., with traps set at 150–200m intervals of altitudinal difference. In each trap, α-Pinene and turpentine were added as bark beetle attractants. Every three weeks over a study period of one year, the captured insects were collected and identified in the laboratory. Abiotic site conditions (temperature and humidity) were also measured at each altitude hourly. During the dry season, phytosanitary characterization was conducted at each site. Throughout the study, 19 Scolytinae bark beetle species were recorded, all of which were considered to be non-aggressive pests. Bark beetles showed higher species richness and abundance at the lowest altitude (2200m a.s.l.), particularly on the early collection dates, compared to other altitudes (2400, 2600 and 2750m a.s.l.; p<0.05). Maximum temperature, minimum temperature, and lowest humidity were higher at low altitudes while maximum humidity was higher at high altitudes. There was a significant positive relationship between maximum temperature and bark beetle abundance. Pines with bark beetles damage were more abundant at 2200m a.s.l. with Pinus pseudostrobus identified as the most damaged tree species. Higher temperatures at lower elevations and projected temperature rise appear to be related to higher damage by the bark beetles on susceptible tree species in these communal forests. Possible management strategies are discussed.

Drivers of the bark beetle disturbance regime in Alpine forests in Austria

Bark beetles are the major biotic disturbance factor threatening Norway spruce (Picea abies [L.] karst.) forests in Austria. The increase of bark beetle salvage after large storm damages is well known. However, over the recent two decades salvage from bark beetle damages in Austria has increased and varied between 0.6 and 3.0millionm3, where at regional scale a complex interplay of initial beetle population density, forest conditions, weather phenomena such as drought periods, various other disturbance agents such as snow and storm and forest management have been hypothesized as major determinants. This points at the need to develop tools to assess the risks of damage from bark beetle disturbances at the operational scale of forest stands, so that adaptation measures can be developed and implemented in a targeted approach. In the current analysis, binomial generalized linear mixed models (GLMMs) were used to assess the effects of site, stand and climate conditions on the probability, and linear mixed models (LMMs) for the intensity of bark beetle disturbance events at forest stand level. The database used for model development combined 10-year forest management plans and related harvest records of four management units of the Austrian Federal Forests covering in total more than 40,000ha of forest, and a gridded climate data set provided by the Austrian Central Institution for Meteorology and Geodynamics. In the models, timber stock volume and previous disturbances had the largest impacts on bark beetle damage. Potential bark beetle generations estimated from a beetle phenology model were also a useful predictor. While the model of disturbance probability correctly classified 90% of all cases in the data set (specificity 95%, sensitivity 29%), the model for damage intensity explained only low shares of the variation in the recorded damage data (full model R2=0.45, fixed-effects-only model R2=0.13; cross validation in the four forest management units yielded similar R2 values). Benefits and limitations of the data set are critically discussed and conclusions for operational forest management are drawn.

Effects of salvage logging and sanitation felling on bark beetle (Ips typographus L.) infestations

The European spruce bark beetle (Ips typographus) is the most devastating biotic disturbance agent in Norway spruce (Picea abies) forests of Central Europe and Scandinavia. To reduce damage by bark beetles, foresters aim at (i) preventing outbreaks by salvage logging of storm-damaged timber, and (ii) lowering bark beetle damage by sanitation felling of beetle-infested spruce trees. The effectiveness of these measures are controversially discussed but has not yet been thoroughly analyzed on a quantitative basis. We analyzed a survey dataset with annual resolution that covers 9years and 487 forest districts (82% of the forested area) all over Switzerland to quantify the drivers of bark beetle infestations, in particular salvage logging and sanitation felling. Poisson log-normal models were used to analyze the dynamics of bark beetle infestations at the forest district level.Bark beetle infestations increased with increasing storm damage, heat sum, volume of Norway spruce stock and the number of infestation spots in the previous year. In contrast, infestations decreased with increasing proportions of sanitation felling relative to the total volume of infested spruce, and with increasing proportions of salvaged windthrown spruce.Our study is the first to quantify the combined effects of salvage logging and sanitation felling on the infestation dynamics of I. typographus in subsequent years, thus allowing forest managers to improve management strategies of bark beetle damage. Sanitation felling and salvage logging reduce the emergence of new infestation spots. In regions with large scale storm damage, salvage logging is clearly more urgent than sanitation felling in the first year and it is therefore recommended to prioritize in the first year after storm events.

The End of the Known World

The End of the Known world is the author's name for a limestone escarpment in Wyoming's Big Horn Mountains. Its location remains unnamed on any map. Over a period of twenty years, its physical and spiritual power has lured her many times to travel on foot to this precipice. As she hikes this time, however, new questions arise: What is it about certain places that calls to us? Do they sometimes wish we would leave them alone? What is the meaning of sacred space? On this journey, the author, now in her sixties, poses these questions to the genius loci, the Greek term for the particular spirit that inhabits sacred locations here on earth. As she hikes over difficult terrain, the author confronts some unexpected physical changes, such as a lack of balance when moving down a steep incline. These bodily changes parallel environmental changes, such as bark beetle damage to many Douglas fir trees that, on her first visit, stood tall and strong at the End of the Known World. The completion of her journey, however, reveals important discoveries. Mollusk fossils inscribed into limestone remain as evidence that the ground on which she stands was once an ancient sea. Eastward, over the Big Horn Basin, soft stripes of gray, blue, and white obscure the horizon, where Mother Earth marries Father Sky. The voice of the genius loci speaks of the love between person and place, and of the impermanence of all things.

Unraveling the drivers of intensifying forest disturbance regimes in Europe

AbstractNatural disturbances like wildfire, windthrow and insect outbreaks are critical drivers of composition, structure and functioning of forest ecosystems. They are strongly climate‐sensitive, and are thus likely to be distinctly affected by climatic changes. Observations across Europe show that in recent decades, forest disturbance regimes have intensified markedly, resulting in a strong increase in damage from wind, bark beetles and wildfires. Climate change is frequently hypothesized as the main driving force behind this intensification, but changes in forest structure and composition associated with management activities such as promoting conifers and increasing standing timber volume (i.e. ‘forest change’) also strongly influence susceptibility to disturbances. Here, we show that from 1958 to 2001, forest change contributed in the same order of magnitude as climate change to the increase in disturbance damage in Europe's forests. Climate change was the main driver of the increase in area burnt, while changes in forest extent, structure and composition particularly affected the variation in wind and bark beetle damage. For all three disturbance agents, damage was most severe when conducive weather conditions and increased forest susceptibility coincided. We conclude that a continuing trend towards more disturbance‐prone conditions is likely for large parts of Europe's forests, and can have strong detrimental effects on forest carbon storage and other ecosystem services. Understanding the interacting drivers of natural disturbance regimes is thus a prerequisite for climate change mitigation and adaptation in forest ecosystem management.

Ophiostomatoid fungi associated with Ips typographus (L.) on Picea abies [(L.) H. Karst.] and Pinus sylvestris L. in north-eastern Poland

This study dealt with the species distribution and frequency of ophiostomatoid fungi associated with the bark beetle Ips typographus on Norway spruce and Scots pine in north-eastern Poland. At all locations high spruce bark beetle damage has occurred in 2002-2003. Fungi were isolated from beetles and from brood systems of trees infested by the spruce bark beetle. The ophiostomatoid fungi were represented by 13 species. A similar spectrum of ophiostomatoid fungi as that recorded from &lt;em&gt;Picea abies&lt;/em&gt; was associated with &lt;em&gt;I. typographus&lt;/em&gt; on &lt;em&gt;Pinus sylvestris&lt;/em&gt; trees. The most frequent ophiostomatoid species isolated from beetles, phloem and sapwood of Norway spruce were &lt;em&gt;O. bicolor&lt;/em&gt; and &lt;em&gt;O. penicillatum&lt;/em&gt;. The frequency of occurrence of ophiostomatoid fungi varied significantly among the examined locations. &lt;em&gt;O. bicolor&lt;/em&gt; was the most frequently found species on Scots pine infested by &lt;em&gt;I. typographus&lt;/em&gt;. The potential role of ophiostomatoid fungi in the epidemiology of &lt;em&gt;I. typographus&lt;/em&gt; is discussed. Additionally, we also recorded how the ophiostomatoid fungi associated with spruce bark beetle could grow into phloem and sapwood of &lt;em&gt;Pinus sylvestris&lt;/em&gt; trees.

Windwurf und Borkenkäferepidemien im Alptal nach Vivian und Lothar | Windthrow and bark beetle attacks in the Alptal after the wind storms Vivian and Lothar

After the strong winter storms Vivian (1990) and Lothar (1999), many Swiss forests have been severely infested by bark beetles. Based on detailed forest management information from 28 forest compartments this study tested a set of potential explanatory variables as predictors for the occurrence of bark beetle damage in the Alptal valley (northern Swiss Prealps). For each storm we developed a separate multiple linear regression model. Bark beetle occurrence was measured as the sum of insect-damaged wood within five years after the winter storms. Two predictors (wind-damaged wood during a winter storm and occurrence of adult spruce) explained more than 50% of the variance of bark beetle occurrence. Our results support the idea that windthrow damage is highly conducive to subsequent bark beetle attack of the surrounding forests. Additionally, the occurrence of larger spruce trees (diameter at breast height &amp;gt; 40 cm) explains a significant fraction of the remaining variance of bark beetle occurrence, which underpins the importance of forest age structure for windthrow and insect damage as causes of tree death. Methodologically, our study highlights the value of historical forest management data in the context of ecological modeling.

Improvement of low level bark beetle damage estimates with adaptive cluster sampling

Detection of low level infestation in forest stands is of principle importance to determine effective control strategies before the attack spread to large areas. Of particular concern is the ongoing mountain pine beetle, Dendroctonus ponderosae (Hopkins) epidemic, which has caused approximately 14 million hectares of damage to lodgepole pine (Pinus contorta Dougl. ex. Loud var. latifolia Engl.) forests in western Canada. At the stand level attacked trees are often difficult to locate and can remain undetected until the infestation has become established beyond a small number of trees. As such, methods are required to detect and characterise low levels of attack prior to infestation expansion, to inform management, and to aid mitigation activities. In this paper, an adaptive cluster sampling approach was applied to very fine-scale (20 cm) digital aerial imagery to locate mountain pine beetle damaged trees at the leading edge of the current infestation. Results indicated a mean number of 7.36 infested trees per hectare with a variance of 18.34. In contrast a non-adaptive approach estimated the mean number of infested trees in the same area to be 61.56 infested trees per hectare with a variance of 41.43. Using a relative efficiency estimator the adaptive cluster sampling approach was found to be over two times more efficient when compared to the non-adaptive approach.

Impact of bark beetle ( Ips typographus L.) disturbance on timber production and carbon sequestration in different management strategies under climate change

The likely environmental changes throughout the next century have the potential to strongly alter forest disturbance regimes which may heavily affect forest functions as well as forest management. Forest stands already poorly adapted to current environmental conditions, such as secondary Norway spruce ( Picea abies (L.) Karst.) forests outside their natural range, are expected to be particularly prone to such risks. By means of a simulation study, a secondary Norway spruce forest management unit in Austria was studied under conditions of climatic change with regard to effects of bark beetle disturbance on timber production and carbon sequestration over a time period of 100 years. The modified patch model PICUS v1.41, including a submodule of bark beetle-induced tree mortality, was employed to assess four alternative management strategies: (a) Norway spruce age-class forestry, (b) Norway spruce continuous cover forestry, (c) conversion to mixed species stands, and (d) no management. Two sets of simulations were investigated, one without the consideration of biotic disturbances, the other including possible bark beetle damages. Simulations were conducted for a de-trended baseline climate (1961–1990) as well as for two transient climate change scenarios featuring a distinct increase in temperature. The main objectives were to: (i) estimate the effects of bark beetle damage on timber production and carbon (C) sequestration under climate change; (ii) assess the effects of disregarding bark beetle disturbance in the analysis. Results indicated a strong increase in bark beetle damage under climate change scenarios (up to +219% in terms of timber volume losses) compared to the baseline climate scenario. Furthermore, distinct differences were revealed between the studied management strategies, pointing at considerably lower amounts of salvage in the conversion strategy. In terms of C storage, increased biotic disturbances under climate change reduced C storage in the actively managed strategies (up to −41.0 tC ha −1) over the 100-year simulation period, whereas in the unmanaged control variant some scenarios even resulted in increased C sequestration due to a stand density effect. Comparing the simulation series with and without bark beetle disturbances the main findings were: (i) forest C storage was higher in all actively managed strategies under climate change, when biotic disturbances were disregarded (up to +31.6 tC ha −1 over 100 years); and (ii) in the undisturbed, unmanaged variant C sequestration was lower compared to the simulations with bark beetle disturbance (up to −69.9 tC ha −1 over 100 years). The study highlights the importance of including the full range of ecosystem-specific disturbances by isolating the effect of one important agent on timber production and C sequestration.

Risk of bark beetle (Coleoptera, Scolytidae) damage in a spruce forest restoration area in central Finland

A beetle inventory using window traps was performed to examine the effect of forest restoration by artificial addition of dead wood on the abundance of beetles and to evaluate the risk of bark beetle damage in a forest restoration area. The number of beetle families was slightly increased, but no consistent differences were found in the abundance of families containing saproxylic Coleoptera between the restoration and control plots. The abundance and species number of bark beetles and longhorn beetles were significantly higher on the restoration plots. Ips typographus and Pityogenes chalcographus increased only slightly in abundance. In the regression models produced, the abundance of bark beetles was best explained by the volume of recently dead wood. However, the bark beetle species whose abundance increased most were secondary and the material also suggests an increase in the abundance of bark beetles’ natural enemies. The risk of bark beetle damage in the area is thus considered insignificant.

Adaptive roadside sampling for bark beetle damage assessment

Bark beetle infestations are often scattered throughout the forest landscape and therefore difficult to accurately and rapidly assess. We tested a roadside sampling technique in a pure maritime pine forest ( Pinus pinaster) of ca. 1300 ha where bark beetle outbreak foci were observed following a windstorm. The sampling method relied on the count along stand edges of all dying or dead trees sighted within a fixed distance from the road. About 2300 trees attacked by Ips sexdentatus were recorded and located using colour-infrared aerial photography. Accuracy of the infestation map was verified by ground sampling. Piles of cut logs stored along the edge significantly increased the percentage of attacked trees in the neighbouring stand. However, the percentage of attacked trees within the stand edges did not differ with the percentage within the stand interior. It allowed us to use stand edges as sampling units to estimate the mean percentage of attacked trees per stand. At the stand scale, the use of a fixed 10 m wide strip along stand edges maximized the detection of attacked trees and minimized the bias of estimated percent of attacked trees. Based on GIS data, various stratified roadside sampling plans with increasing numbers of edges per stand and increasing numbers of stands per forest were simulated by bootstrap resampling. In a forest without any storage of cut logs, systematic roadside surveys underestimated the level of damage. The sampling accuracy increased with the kilometers of edges surveyed. In a forest with piles of cut logs on which bark beetles can breed, the best option was an adaptive sampling plan where at least two additional consecutive edges were observed in stands close to the pile. As compared to systematic sampling plans, adaptive plans were three times less expensive in terms of sampling effort for the same accuracy. Overall, adaptive sampling plans were also more robust as they provided less biased estimates as the proportion of stands with nearby piles increased in simulated forests.

Fungal flora associated with Ips typographus: frequency, virulence, and ability to stimulate the host defence reaction in relation to insect population levels

This study was aimed at determining the composition of Ips typographus L. (Coleoptera: Scolytidae) associated fungal flora in France, its virulence, and its ability to stimulate host defence reactions. The relationship between these parameters and the beetle population levels was also considered. The study was conducted in 2001, 2002, and 2003 in Norway spruce (Picea abies (L.) Karst.) stands, with different bark beetle damage levels. In each stand, the frequency of association between fungi and I. typographus was determined. The virulence of the most frequent species was assessed through mass inoculations on living spruce trees. The ability to stimulate the host defence reactions was estimated with low-density inoculations. The most frequent species, Ophiostoma bicolor Davids. &amp; Wells, Ophiostoma piceaperdum Rumbold, and Ophiostoma tetropii Mathiesen, were all pathogenic. Ophiostoma piceaperdum also induced intense defence reaction zones, suggesting that it could play a role in I. typographus population establishment on living trees. However, significant correlations between fungal frequencies and damage of the current year were observed only with O. tetropii or O. bicolor, and no relationships between damage of the previous year and fungal frequencies were found. The effects of some fungal species on beetle population dynamics was suggested, but selection of species during epidemic condition was not confirmed.

Prefire heterogeneity, fire severity, and early postfire plant reestablishment in subalpine forests of Yellowstone National Park, Wyoming

The 1988 fires in Yellowstone National Park providedan opportunity to study effects of a large infrequent disturbance on a natural community. This study addressed two questions: (1) How does prefire heterogeneity of the landscape affect postfire patterns of fire severity? and (2) How do postfire patterns of burn severity influence plant reestablishment? At three sites, 100 sampling points were distributed regularly in a 1-km x 1-km grid and sampled annually from 1989 to 1992. Information was recorded on fire severity (damage to trees, depth of ash and soil charring, and percent mineral soil exposed); pre-fire forest structure (forest successional stage; tree density; tree species; tree size; and evidence of pre-fire disturbance by mountain pine beetle [Dendroctonus ponderosae Hopk.] or mistletoe [Arceuthobium americanum Nutt. ex Engelm.]); post-fire percent cover of graminoids, forbs, and low shrubs; number of lodgepole pine (Pinus contorta var. latifolia Engelm.) seedlings; and general topographic characteristics (slope and aspect). Fire severity was influenced by successional stage, with older stands more likely to be in the more severe burn class, and by tree diameter, with tree damage diminishing with tree size. Prefire bark beetle and mistletoe damage also influenced fire severity; severe prefire damage increased the likelihood of crown fire, but intermediate prefire damage reduced the likelihood of crown fire. Fire severity was not influenced by slope, aspect, or tree density. Postfire percent vegetative cover and density of lodgepole pine seedlings varied with burn severity. In lightly burned areas, percent cover returned to unburned levels by 1991. In severely burned areas, total percent cover was about half that of unburned areas by 1992, and shrub cover remained reduced. Recruitment of lodgepole pine seedlings was greatest during the second postfire year and in severe-surface burns rather than in crown fires. Continued monitoring of vegetation dynamics in Yellowstone’s burned forests will contribute to our understanding of successional processes following a disturbance that was exceptional in its size and severity.

Field Stereo Viewers for Aerial Photography

Abstract Portable stereo field viewers using color transparencies for three aerial film formats--70 mm, 9 by 9 inch, and panoramic (5 by 50 inch)--were developed for surveys using multistage techniques to appraise bark beetle damage. The three instruments are light in weight, compact, illuminated by indirect or reflected sunlight, and constructed of readily available materials. They can be built by anyone with good mechanical ability and the proper tools.

Colonization of freshly bared pine sapwood surfaces by staining fungi

Bluestain fungi are known to infect pine logs from the cross-cut ends and from bark beetle tunnels, but the importance of man-made bark wounds as infection courts has not been investigated. Evidence is presented to show that sticky-spored Ceratocystis spp. invade wounds where the tangential wood surface is protected from light and desiccation but are unable to invade either tangential or cross-cut surfaces which are exposed to light and desiccation. The freely exposed surfaces are colonized by common airborne dematiaceous saprophytes, which give a superficial appearance of stain. Insecticide treatment prevents bark beetle damage and significantly reduces the incidence of Ceratocystis spp., but does not entirely prevent it and has no effect on airborne staining fungi. The incidence of all fungi is highest in the late summer months.

The research on the cause of the pine bark beetle damage

The research on the cause of the pine bark beetle damage