Factors influencing the wind–bark beetles’ disturbance system in the course of an Ips typographus outbreak in the Tatra Mountains (original) (raw)
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Forest Ecology and Management, 2020
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.
Drivers of Spruce Bark Beetle (Ips typographus) Infestations on Downed Trees after Severe Windthrow
Forests
Research Highlights: Bark beetles are important agents of disturbance regimes in temperate forests, and specifically in a connected wind-bark beetle disturbance system. Large-scale windthrows trigger population growth of the European spruce bark beetle (Ips typographus L.) from endemic to epidemic levels, thereby allowing the killing of Norway spruce trees over several consecutive years. Background and Objectives: There is a lack of evidence to differentiate how outbreaks are promoted by the effects of environmental variables versus beetle preferences of trees from endemic to outbreak. However, little is known about how individual downed-tree characteristics and local conditions such as tree orientation and solar radiation affect beetle colonization of downed trees. Materials and Methods: To answer this question, we investigated the infestation rates and determined tree death categories (uprooted, broken, and stump) in wind-damaged areas in Western Tatra Mts. in Carpathians (Slovaki...
In 1981-87 the extended forest decline affected the Norway spruce stands of western Sudetes. Starting from 2002 in the western Carpathians the similar, still ongoing, process takes place. In both areas the direct agent finally determining spruce tree mortality was the bark beetle outbreak, but the factors contributing in the process were not the same. In the Sudetes the spruces have been heavily defoliated by Zeiraphera griseana Hb. larvae prior to the bark beetle outbreak, while in the Carpathians the root rot is supposed to be a factor affecting spruce vitality. The effect of individual features on the predisposition of the stands to the bark beetle attack is discussed. Based on the spatially referenced data, the analysis of the process in altitudinal aspect is presented. The comparison of the origin and characteristics of the outbreaks' development, and resulting forest decline, is proposed.
Folia Forestalia Polonica
In March 2017, in the eastern part of the Tatra National Park in Poland, large windthrowns affected the passively and actively protected Norway spruce Picea abies stands. In early 2018, a set of 12 small research plots (20 trees on each plot) was established in the Norway spruce stands next to the windblown area – 6 in the stands under active nature protection (broken and fallen trees processed in 2017), and 6 in the stands under passive nature protection (trees left on the ground). Living trees on the plots were regularly checked during the growing season in order to identify and register the spruces infested by Ips typographus, which were dissected in 2 or 4 half-meter sections. 155 spruces (64%) infested by I. typographus were recorded on all 12 plots: 118 out of 120 (98%) in passive and 37 out of 120 trees (31%) in active protection. Mean infestation density calculated on 128 samples from 47 trees was higher under passive than under active protection (1.23 and 0.92 mating chambe...
The characteristics of spruce individuals, which survived a massive bark beetle outbreak, were compared with the characteristics of neighbouring attacked trees in Š umava National Park (Czech Republic). Selected parameters related to crown geometry, stand conditions and distances between trees were measured or estimated. Significant differences were found between the surviving trees and the neighbouring trees attacked by I. typographus. Trees with a higher level of stem shading (longer crown length) tended to survive. The attacked trees were usually located in areas with larger basal area, especially southwards from them. A shorter distance to a previously attacked tree increased the probability of additional attack. Spruce trees with more progressive crown structure transformation (primary structure defoliation) were significantly more frequently attacked by spruce bark beetle. Superior and taller trees had a clearly longer life expectancy than dominant ones. These results show that the attack of trees by bark beetle can be predicted to a certain degree, which can be used in management of endangered spruce forests.
Agricultural and Forest Meteorology, 2017
Norway spruce forests (Picea abies Karst.) of the Carpathian High Tatra Mountains have been subject to unprecedented tree mortality caused by attacks of the Eurasian spruce bark beetle (Ips typographus L.) in recent decades. The outbreaks were preceded and accompanied by wind throw events and periods of increased seasonal temperature. We obtained climatic data and data on tree mortality due to storm throw and bark beetles by using a combination of direct dead tree inventory and remote sensing techniques, and examined annual tree loss change over a 26-year period in a forest district of the Slovak High Tatra National Park. In particular, we found that the combination of the previous year's maximum daily temperature sum, tree mortality caused by wind, and bark beetle-caused tree mortality best explained the annual tree loss change in nonlinear regression models. The number of trees infested by bark beetles clearly increased with maximum air temperature sums ranging from 2850 to 3150°days, but declined below or above this thermal optimum. Annual tree mortality clearly increased subsequent to years associated with seasonal temperature sums allowing for the development of sister broods. Given consistently favourable future climatic conditions for development of I. typographus populations in the study area, a possible shift from the now predominantly uni-voltine to multi-voltine bark beetle populations might increase attack pressure also at high elevation sites.
The spread of bark beetle outbreaks in the Tatra Mountains was explored by using both terrestrial and remote sensing techniques. Both approaches have proven to be useful for studying spatial patterns of bark beetle population dynamics. The terrestrial methods were applied on existing forestry databases. Vegetation change analysis (image differentiation), digital elevation model, and stand characteristics have been integrated in the remote sensing part of the study. Results have revealed that the spatial pattern of bark beetle spread depends on the phase of the outbreak and on the insolation (amount of incoming solar radiation) of stands on mountain slopes and, specifically on the bark beetle spots themselves. Terrestrial Approach We initiated our research by creating rich databases which contained detailed information about the characteristics of stands and bark beetle populations. Information on site characteristics, stand composition and age, and annual tree mortality during the period 1990-1999 was acquired from the administrative offices of the Tatrzński Park Narodowy (TPN-Poland) and Tatranský Národný Park (TANAP-Slovakia). The smallest units of data that were used in our research consisted of forest sub-compartments. The data concerning tree mortality was transformed into tree mortality indices (TMI) and expressed as the mean volume of infested trees per one hectare in the sub-compartment (m 3 /ha). The data were ranked according to a somewhat adjusted scale developed by Capecki (1981), with the following ranges of mortality in m 3 /ha: 0.01-0.4-normal, 0.41-1.2-premonitory, 1.21-2.4-intensive, 2.41-10.0-very intensive, >10.0-catastrophic. The digital map with a DTM, covering the research area (Koreň et al. 2002), and the layers concerning tree mortality, were constructed using a vector oriented software ArcView 3.1. The layers on tree mortality (TMI) in successive years were used to produce a visualization of spread of bark
The characteristics of spruce individuals, which survived a massive bark beetle outbreak, were compared with the characteristics of neighbouring attacked trees in Š umava National Park (Czech Republic). Selected parameters related to crown geometry, stand conditions and distances between trees were measured or estimated. Significant differences were found between the surviving trees and the neighbouring trees attacked by I. typographus. Trees with a higher level of stem shading (longer crown length) tended to survive. The attacked trees were usually located in areas with larger basal area, especially southwards from them. A shorter distance to a previously attacked tree increased the probability of additional attack. Spruce trees with more progressive crown structure transformation (primary structure defoliation) were significantly more frequently attacked by spruce bark beetle. Superior and taller trees had a clearly longer life expectancy than dominant ones. These results show that the attack of trees by bark beetle can be predicted to a certain degree, which can be used in management of endangered spruce forests.
2006
We developed a model for monitoring population dynamics and phenology of Ips typographus. The modelling procedures can be used for simulation of spring swarming, start of offspring generations, assessment of the developmental stage of the brood, and risk assessment of outbreaks. Temperature of the bark is most important for brood development. It is affected by ambient air temperature and direct solar irradiation. Brood development can be estimated using upper and lower temperature thresholds and a nonlinear function for calculating effective temperatures and the thermal sums necessary for successful development. The reproductive phase of I. typographus is limited by a minimum day length of 15 hours. Successful hibernation can be predicted by assessing the developmental stage of established generations at the end of the growing season. Applying the model for retrospective analysis of population dynamics as well as drawing of scenarios can help to get a better understanding of the complex ecological interactions involved in bark beetle outbreaks. In combination with a topoclimatic model, spatial visualization of potential development and possible risks of I. typographus outbreaks was done in the mountainous region of Kalkalpen National Park, Upper Austria.