Article

Sanitary felling of Norway spruce due to spruce bark beetles in Slovenia: A model and projections for various climate change scenarios

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Abstract

A model is presented to predict sanitary felling of Norway spruce (Picea abies) due to spruce bark beetles (Ips typographus, Pityogenes chalcographus) in Slovenia according to different climate change scenarios. The model incorporates 21 variables that are directly or indirectly related to the dependent variable, and that can be arranged into five groups: climate, forest, landscape, topography, and soil. The soil properties are represented by 8 variables, 4 variables define the topography, 4 describe the climate, 4 define the landscape, and one additional variable provides the quantity of Norway spruce present in the model cell. The model was developed using the M5′ model tree. The basic spatial unit of the model is 1 km2, and the time resolution is 1 year. The model evaluation was performed by three different measures: (1) the correlation coefficient (51.9%), (2) the Theil's inequality coefficient (0.49) and (3) the modelling efficiency (0.32). Validation of the model was carried out by 10-fold cross-validation. The model tree consists of 28 linear models, and model was calculated for three different climate change scenarios extending over a period until 2100, in 10-year intervals. The model is valid for the entire area of Slovenia; however, climate change projections were made only for the Maribor region (596 km2). The model assumes that relationships among the incorporated factors will remain unchanged under climate change, and the influence of humans was not taken into account. The structure of the model reveals the great importance of landscape variables, which proved to be positively correlated with the dependent variable. Variables that describe the water regime in the model cell were also highly correlated with the dependent variable, with evapotranspiration and parent material being of particular importance. The results of the model support the hypothesis that bark beetles do greater damage to Norway spruce artificially planted out of its native range in Slovenia, i.e., lowlands and soils rich in N, P, and K. The model calculation for climate change scenarios in the Maribor region shows an increase in sanitary felling of Norway spruce due to spruce bark beetles, for all scenarios. The model provides a path towards better understanding of the complex ecological interactions involved in bark beetle outbreaks. Potential application of the results in forest management and planning is discussed.

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... There are phenological models that predict bark beetle phenology, such as PHENIPS [14] and RITY [15]. On the other hand, there are ecological models which take different variables into account [13,[16][17][18]. These models have found that outbreak potential is most affected by drought and high temperatures, the amount of spruce and storm felled trees [5,19,20]. ...
... These models have found that outbreak potential is most affected by drought and high temperatures, the amount of spruce and storm felled trees [5,19,20]. However, the majority of these models do not predict future outbreaks in the short term or long term (for example, see [16,17,20,21]). Such models can focus on predicting the occurrence of a potential outbreak or predicting the amount of sanitary felling. Both outcomes are important in their own way. ...
... Slovenia has a long history of bark beetle outbreaks. Several methods exist for the short-and long-term predictive modeling of spruce bark beetles [15][16][17]22] and have been implemented for several years [22][23][24]. However, a model that predicts short-term sanitary felling is still lacking. ...
... Another method is modeling of outbreak probability based on environmental data from the previous year. Although many studies have already modeled the potential drivers of bark beetle outbreaks (Blomqvist et al., 2018;Marini et al., 2017;Ogris and Jurc, 2010;Pasztor et al., 2014), most only examined data from the same year or neglected the possibility of forecasting outbreaks for short periods. ...
... The following data were used for the development of the models: sanitary felling of spruce and fir because of bark beetle outbreaks in the current year (m 3 /ha), amount of fir and spruce (share in total wood stock), altitude (m a.s.l.), exposition (°), slope (°), dominant geology type, exchangeable phosphorus (mg/100 g), soil depth (cm), soil cation exchange capacity (mmolc/100 g), soil base saturation (%) (Ogris, 2007;Ogris and Jurc, 2010), Standardized Precipitation Index (SPIa proxy for drought) during the previous growing season (Minimum SPI means that it is very dry and maximum SPI very wet), average temperature during the previous growing season (°C), cumulative amount of precipitation in the previous year (mm), amount of sanitary felling because of bark beetle outbreak in the previous year (m 3 /ha), amount of weakened trees because of bark beetles in the previous year (m 3 /ha), amount of sanitary felling because of abiotic factors in the previous year (m 3 /ha), and the location (X and Y) of the model grid cell. ...
... Host density was also positively correlated with sanitary felling because of bark beetles (Yildiz et al., 2007, see results). This association was also observed in other species of bark beetles (de Groot et al., 2019;Fettig et al., 2007;Ogris and Jurc, 2010). However, in the case of other bark beetle species such as Ips typographus and western balsam bark beetle (Dryocoetes confuses Swaine), host trees are often found in large monocultures, which greatly increases the probability of attack. ...
Article
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In recent years bark beetles have been shown to be an important risk factor in European forests. An early warning system is needed to mitigate bark beetle damage, and short-term forecasting models that assist efforts to identify attacked trees comprise an important part of such a system. The aim of this study was to develop short-term forecasting models of the probability of bark beetle outbreaks on two important conifer tree species: Norway spruce (Picea abies) and silver fir (Abies alba). For the development of the models, we used a time series of 20 years of sanitary felling because of bark beetles and relief data (altitude, slope and exposition), several soil variables, climate data (temperature and SPI), sanitary felling because of bark beetles, sanitary felling due to harmful abiotic factors, and amount of weakened trees due to bark beetles. The forecasting variable was sanitary felling because of bark beetles in the current year. The models were developed with a general linear model with binomial error distribution. For the probability of bark beetle outbreaks on silver fir, the amount of fir, soil base saturation percentage, sanitary felling of attacked fir, weakened fir, and sanitary felling because of abiotic factors increased the probability of sanitary felling because of fir bark beetles. Altitude, exposition, slope, phosphorus, soil depth, soil cation exchange capacity, SPI and temperature decreased the probability of sanitary felling because of fir bark beetles. For Norway spruce, the amount of Norway spruce, soil base saturation percentage, SPI, temperature, amount of sanitary felling in the previous year, amount of weakened trees in the previous year, and amount of sanitary felling because of abiotic factors in the previous year increased the probability of sanitary felling of Norway spruce because of bark beetles in the current year. Slope, soil cation exchange capacity, and precipitation decreased the probability of sanitary felling because of bark beetles in the current year. The performance of the bark beetle risk model for Norway spruce was very good. The performance of the model for silver fir was also good, but not on par with that for Norway spruce. Therefore, additional research on fir bark beetles is needed to further improve the risk model for bark beetle attacks on silver fir.
... Bark beetle management is based on preventive and reactive management (Wermelinger, 2004;Vega & Hofstetter, 2015). Preventive bark beetle management is based on silvicultural management, where the host plant should not be so abundant as to increase the probability of outbreaks, as has already been shown in many cases (Ogris & Jurc, 2010;Pasztor et al., 2014). Reactive bark beetle management deals with short-term measurements when the outbreak is already in progress. ...
... There was a visible change in drivers between the endemic and the epidemic state of the bark beetle population. Factors such as slope and the amount of spruce in the forest were determined to be important for bark beetle outbreaks in other studies (Ogris & Jurc, 2010;Pasztor et al., 2014). However, the ice storm had the opposite effect on the importance of both factors. ...
... In the ice storm, the bark beetle damage to spruce was greater in areas with a large amount of spruce than in areas with less spruce. Even when there was a low proportion of damaged spruce, the population of bark beetles increased to the extent that healthy trees were also attacked (Ogris & Jurc, 2010;Pasztor et al., 2014). Slope on the other hand had a negative correlation with the amount of attacked trees. ...
Article
Large-scale disturbances in forests are becoming more frequent due to a changing climate. Biotic disturbances can have cascading effects and therefore have a significant economic impact in forestry. It is therefore important to gain an understanding of the drivers of forest pest outbreaks in epidemic situations after large-scale disturbances and the implications for forest management. We investigated the influence of drivers on the bark beetle outbreaks following a large-scale ice storm in 2014 in Slovenia. A country-wide survey was done on the variables affecting ice storm damage to spruce trees. Additionally, the influence of the drivers of bark beetle attacks on outbreak intensity was assessed and compared under epidemic and endemic situations, and the effectiveness of forest management measures was assessed. Spruce trees were either uprooted or snapped, or the crown was lightly to severely damaged. The outbreaks under endemic situations were potentiated by the increasing amount of spruce and reduced by increasing slope. After the ice storm, the amount of sanitary felling because of outbreaks increased in areas with more steeper slopes, where the ice storm took place. An increase in the level of disturbance and a higher availability of dead and weakened trees positively affected bark beetle populations. The removal of dead trees alone in the first year after the ice storm was found to be an insufficient measure for preventing bark beetle outbreaks. The ineffectiveness of current practices suggests that bark beetle management should be reconsidered with regard to large-scale disturbances. When defining measures against bark beetle outbreaks, drivers in epidemic situations should be prioritized over those that are important in endemic situations. The results imply that the known factors that affect bark beetle attacks are not necessarily the same as those that drive bark beetle attacks after extraordinary disturbance events. Mixed stands should be promoted in forests for sustainable management.
... Outbreaks of I. typographus are especially common after catastrophic climatic events (windthrow, heavy snowfall, ice storms, etc.) (de Groot et al., 2018;Kausrud et al., 2012;Komonen et al., 2011;Wermelinger, 2004). In addition, tree health and local site characteristics also play an important role in the susceptibility of forests to outbreaks (Ogris and Jurc, 2010;Pasztor et al., 2014). Although many studies have already focused on the causes of I. typographus outbreaks (Kausrud et al., 2012;Wermelinger, 2004 and references herein), few have focused on the role of forest management. ...
... There were interactions found between the altitude, proportion of Norway spruce and whether it was an epidemic or non-epidemic period. Altitude had a negative correlation with sanitary felling (Mezei et al., 2014;Ogris and Jurc, 2010;Pasztor et al., 2014) and was negatively associated with the altitudinal temperature gradient. Higher temperatures weaken Norway spruce, particularly in areas outside its natural range (Levanič et al., 2009). ...
... The proportion of Norway spruce, on the other hand, had a positive correlation with sanitary felling. This can be explained by resource availability, meaning that more Norway spruce trees sustain a larger population of I. typographus (Ogris and Jurc, 2010), or that a higher number of species obscure the secondary volatiles of Norway spruce trees, which makes it more difficult for bark beetles to find host trees (Lieutier et al., 2004). Although the effect of altitude and Norway spruce was already known, the factors interact with each other and are amplified when there is an epidemic period. ...
Article
Historical management practices could have a strong effect on the current status of forests and therefore affect the potential for outbreaks of forest pests. We tested whether forest management history and forest tending of Norway spruce affects the potential for bark beetle outbreaks after large disturbances. We also assessed the effect of the proportion of spruce under epidemic situations and different altitudes. For this survey we used long-term data on sanitary felling and forest inventory data. Forest management history was defined by the change in the forest compared to the natural forest composition and was divided into four classes of change in tree species composition. We compared the proportion of spruce and sanitary felling because of bark beetles with the different classes of change in tree species composition. Forest tending was analyzed by looking at how the proportion of realized cut in relation to the planned cut affected sanitary felling. The analysis was done with Bayesian modeling including both spatial autocorrelation and random effects. There was a strong association between the change in the forest tree species composition and the proportion of Norway spruce and sanitary felling because of spruce bark beetles. Interactions were observed between epidemic periods, the proportion of Norway spruce and altitude. Altitude had a negative influence and the proportion of Norway spruce had a positive influence on sanitary felling. During epidemic periods, sanitary felling was amplified at lower altitudes and in areas with a higher proportion of Norway spruce. Furthermore, there was a negative association between the proportion of realized cut in relation to the planned cut and sanitary felling in periods after abiotic stress. It is therefore suggested that monocultures of Norway spruce should be converted to mixed forests and that maintenance of the forest should be improved to increase resistance to bark beetle outbreaks.
... Due to shallow rooting systems, Norway spruce stands are particularly vulnerable to low amounts of precipitation, as well as to water defi ciency in upper soil layers (Schwerdtfeger, 1955;Schmidt-Vogt, 1989). Hence, various models developed for evaluating the probability of infestation by I. typographus consider soil and hydrological variables such as the soil depth, drainage class and available water capacity of the soil as important predictors (Dutilleul et al., 2000;Netherer and Nopp-Mayr, 2005;Ogris and Jurc, 2010;Overbeck and Schmidt, 2012). Climate extremes can aggravate the eff ects due to bad matches of site conditions and tree species composition, and may impact the associated forest insects signifi cantly; as, for example, observed during the heat and drought wave in Western Europe in 2003 (Rouault et al., 2006). ...
... Th e projected intensifi cation of drought events for parts of Europe calls for a better understanding of the eff ects on the Eurasian spruce bark beetle and its tree host (Lindner et al., 2010), especially for forest sites that already suff er from water defi cit and will be aff ected most negatively by increasingly stressful climatic conditions (Netherer and Schopf, 2010;Ogris and Jurc, 2010;Seidl et al., 2011b). For example, choice experiments on diff erentially drought-impaired trees (Turcani and Nakladal, 2007) might contribute to a better understanding of how water supply acting upon constitutive and inducible defences (Rosner and Hannrup, 2004;Franceschi et al., 2005) aff ects attack and propagation rates. ...
Chapter
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The Eurasian spruce bark beetle is one of the major forest pests in Europe, capable of mass attacking and killing Norway spruce over extensive areas during outbreaks. Here, we review various aspects of its biology in relation to climatic variables. The aim of this review was to make predictions about the potential consequences of climate change on the propensity for outbreaks across European forests. More frequent extreme winds and drier and warmer summer climate may trigger both population growth and the susceptibility of spruce stands to attack. Breeding material provided by large windfall events increase the beetle population rapidly to a level capable of killing living trees through mass attack. Such epidemics may proceed until the susceptible spruces are exhausted, or when other extrinsic conditions stop the bark beetles from further colonization. At the southern margin of the spruce distribution in Europe, lower than average precipitation seems generally to favour infestations. In central and Western Europe, even-aged plantations outside the natural range of Norway spruce are highly susceptible to disturbance events such as windthrow and bark beetle attacks. A warmer climate is expected to give a northern expansion of the area experiencing two generations per year in Europe. There have been few bark beetle outbreaks in the extensive areas of spruce forest in Finland and the northern part of Scandinavia, but increasing bark beetle populations and infestations have been observed during warm years in the last decade. The northern part of Europe may be subject to huge outbreaks if a warmer climate increases the population sizes of the Eurasian spruce bark beetle.
... For example Rossi et al. (2009), Avtzis et al. (2012) and Six (2012) have investigated the biology, development, ecology and phylogeography of different bark beetle species. From a different approach, the spatial distribution and pattern of I. typographus populations in Europe has been analysed by Heurich et al., 2003, Meier et al. (2003, Müller et al. (2008), Ogris and Jurc (2010) and Lausch et al. (2011Lausch et al. ( , 2013. In addition, a number of other investigations have been conducted for North America (Powers et al., 1999;Negron et al., 2000;Klutsch et al. 2009) and Canada (Wulder et al., 2006a;Aukema et al., 2008;Coops et al., 2009). ...
Article
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The bark beetle (Ips typographus L.) is known for the detrimental impact it can have on Europe’s mature spruce forests with bark beetle outbreaks already having devastated thousands of hectares of spruce forests in Germany. This study analysed the hypothesis that the vitality of spruce vegetation is already susceptible from factors such as climate change or emissions to a certain extent before infestation, so that the role of the subsequent bark beetle infestation is only secondary. Hyperspectral remote-sensing techniques were used to detect changes in biochemical–biophysical vegetation characteristics in the spruce forest of the Bavarian Forest National Park, Germany. For this study, several spectral bands, vegetation indices and specific spectral band combinations of hyperspectral HyMAP remote-sensing data with a 4 m and a 7 m ground resolution were analysed and compared in terms of their classification accuracy, generating an ID3 decision tree. The vitality classes and thus also the attack stages of the spruce vegetation could be estimated with moderate to good accuracy using hyperspectral remote-sensing data. Clear spectral differences between the class with spruce trees that were still green but with reduced vitality (possibly the first stages of green-attack) and the class with healthy spruce trees could be ascertained. The best spectral characteristics, spectral indicators and spectral derivatives related to vitality classes and thus attack stages were typically based on wavebands related to prominent chlorophyll absorption features in the VI within the spectral range of 450–890 nm. Only limited spectral information and derivatives could be found in the short-wave infrared region 1 (SWIR) within the spectral range of 1400–1800 nm, which reflects the water content of the spruce needles. The class of spruce trees that were still green but with reduced vitality (possibly the first stages of green-attack) showed a trend towards detectability and differentiation with spectral indicators and index derivatives. However, the prediction of observed effects with 64% accuracy as observed here is regarded as insufficient in forestry practises. Hyperspectral data with a ground resolution of 4 m were found to contain more information relevant to estimating the vitality class of spruce vegetation compared to hyperspectral data with a ground resolution of 7 m.
... Additionally, bark beetle attacks on the Norway spruce may be more likely under drought conditions (Kazda & Pichler, 1998) or with an increased presence of deadwood in forest gaps (Schroeder, 2010) as a consequence of strong winds (Peltola, Kellomäki, Hassinen, & Granander, 2000). The projected higher average temperatures and prolonged growing seasons can result in a shift from univoltinism to multivoltinism (i.e., from one to two (or more) completely matured bark beetle generations every year (Lange, Økland, & Krokene, 2006;Ogris & Jurc, 2010)) and thereby further increase the pressure on the trees. ...
... We were unable to do this due to our limited dataset and our study frame (the initiation and severity of tree mortality, outbreak phases). Another possibility is to not consider this problem (Ogris and Jurc, 2010), but we did not consider this to be an appropriate approach. Therefore, we addressed this problem by dividing the tree mortality data into the processes of initiation and severity in the different phases of the outbreak. ...
Article
An outbreak of spruce bark beetle (Ips typographus [L.]) in the Tatra Mountains in the Slovak Republic and Poland, Central Europe, was analysed. The study area was nearly 3000 ha. The 11 year outbreak lasted from 1990 to 2000. Three outbreak phases were identified: 1990–1994 (incipient epidemic), 1995–1996 (epidemic) and 1997–2000 (post-epidemic). More than 118,000 m3 of trees were damaged by wind and bark beetles. The analysis considered the relationship and succession of these two types of disturbances. Discrimination analysis, a multiple linear regression and boosted regression trees were used to determine the influence of 11 variables on tree mortality initiation and severity. The wind–bark beetles disturbance system was primarily influenced by stand related factors. Tree mortality initiation primarily depends on stand age and related changes in Norway spruce size and vitality. Wind caused tree mortality severity was primarily related to the tree or stand characteristics as well. The roles of host and environmental factors in the initiation and severity of tree mortality were influenced by the I. typographus outbreak phase. Stand, site and solar radiation variables were the most important factors impacting tree mortality severity caused by this disturbance system, especially in the epidemic phase. However, the severity of tree mortality caused by wind was primarily correlated with the stand characteristics. With the exception of elevation, the roles of the studied factors were similar in all gradation phases.
... In the end, when the automatically induced models are interpreted and combined with expert's knowledge, we can acquire analysis results of a higher quality and gain new insights into the investigated topic. In the area of life sciences, machine learning tools have already been successfully used for data analysis and learning of qualitative and quantitative models from data with many applications in the field of environmental and agricultural sciences (Debeljak et al., 2007(Debeljak et al., , 2011(Debeljak et al., , 2012Trajanov et al., 2008Trajanov et al., , 2009Trajanov, 2011), and also some applications in forestry (Stojanova et al., 2010Ogris and Jurc, 2010). ...
Article
Growing stock is an ecological indicator of forest ecosystem response to natural and anthropogenic impacts that may result from forest management measures or environmental impacts. Information on growing stock is thus essential to understand dynamics of forest stands, their productive capacity and to manage their use within limits of sustainability. Dynamic changes of forest growing stock, as well as predictions of their future development, are usually estimated from the data gathered by national forest inventories using some mechanistic modelling approach. The resulting models are informative, but include many parameters, some of which are difficult to set or estimate. Due to the demanding parameterisation of mechanistic models, it is hard to achieve stability of their output accuracy, which can lower their predictive power. This paper presents an alternative and complementary approach of constructing models with machine learning and data mining methods. We applied these methods to the Silva-SI database and used the resulting interpretable models in order to find explanations for structural changes in Slovenian forests over the period from year 1970 to 2010. In addition, we developed predictive models for growing sock in the decade from year 2010 to 2020. The structure of the models describing temporal dynamics of growing stock shows that trends of growing stock are increasing for the entire studied period, while accumulation of growing stock is much more intensive after 1990. Forests with a lower growing stock are located either in the areas with non-favorable site conditions for forest growth, or at lower altitudes, where they are more exposed to human exploitation due to their vicinity to more densely populated regions. Predictions of growing stock for the decade 2010–2020 suggest that Slovenian forests will continue to accumulate their growing stock (private owned forests to 327 m3/ha and state owned forests to 343 m3/ha in 2020). The presented data mining approach that was here applied to the growing stock can also be used for investigating other ecological indicators.
... For example, windthrown trees can contribute to increased fuel loading, leading to enhanced potential for fire disturbance (Myers and van Lear, 1998;Cannon et al., 2019). Similarly, the volume of downed timber may provide breeding material for bark beetles that then spread to surrounding stands and cause direct effects there (Wichmann and Ravn, 2001;Fettig et al., 2007;Ogris and Jurc, 2010;Stadelmann et al., 2013). There are also important interactions between wind damage and drought (Allen et al., 2015;Csill ery et al., 2017) and insect and wind damage (Taylor and MacLean, 2009) (Hale et al., 2015), for Glen Affric semi-natural pine forest in northwest Scotland (Quine, 2003b). ...
Article
The interaction of wind and trees can result in substantial changes to forest structure and is of interest to many forest ecologists, but the complexity of the relationship has confounded many studies. The result of the interaction can take many forms across a range of scales, may have chronic and acute components, and can be exacerbated by other conditions, such as wet snowfall and salt deposition. Leaves may be abraded, causing subsequent desiccation; young trees may socket (that is, become loosened around the root collar by swaying) and in extreme cases topple because of inadequate rooting; leaders, branches, and crowns may break; older trees may be windthrown when stem and root plate overturn or may experience windsnap when the stem fails above ground level. However, many studies commence after the interaction is complete. Such post event investigation frequently seeks simple relationships and frequently yields disappointing results. There is no escaping the fact that the interaction is complex, and an understanding of the process and response requires the integration of multiple disciplines, such as soil science, physiology, ecology, mechanics, meteorology, and climatology. This chapter seeks to demonstrate that such integration, although difficult, is possible. The chapter also attempts to outline the processes and mechanisms of wind and tree interaction that can be used to understand the likelihood of wind disturbance.
... Many authors have studied the factors that influence spruce mortality caused by bark beetles (Ips typographus) (Dutilleul et al., 2000;Becker and Schröter, 2001;Gilbert et al., 2005;Klopcic et al., 2009;Ogris and Jurc, 2010;Lausch et al., 2011;Marini et al., 2012;Overbeck and Schmidt, 2012;Albrecht et al., 2012;Thom et al., 2013;Mezei et al., 2014). The results of these investigations indicate that the mortality caused by I. typographus can be explained by characteristics such as forest age, potential solar radiation, and disturbance history. ...
... The central tendency and quantiles below the 75 th percentile, however, match the theoretical expectations from a negative exponential distribution fairly well (Fig. 1b). This underlines the utility of our database, particularly considering that long disturbance records with large spatial coverage and small spatial grain are scarce (but see Ogris and Jurc, 2010;Stadelmann et al., 2013). Notwithstanding the limitations of our data, the analysis presented here can serve as an important baseline for future analyses (both empirical and model-based) of climate-induced changes in the disturbance regime. ...
Article
Forest disturbance regimes have intensified in many parts of the world in recent decades, and are an increasing problem for managers concerned with the sustainable and continuous provisioning of forest ecosystem services. In order to address these changes an improved understanding of disturbance regimes is needed, particularly with regard to their main drivers and climate sensitivity. Here, our objectives were to first quantitatively describe the recent disturbance regime of forest ecosystems in Austria (3.99 × 106 ha). Second, our aim was to identify the main drivers of the disturbance regime, distinguishing slow, predisposing factors and fast, inciting factors. We utilized district-level disturbance observations from 2002 to 2010, and focused on damage from wind and bark beetles, the most detrimental abiotic and biotic disturbance agents in Europe. In a two-stage approach, we first analyzed the influence of slow, predisposing variables on the spatial variation in mean disturbance damage, using principle component regression. Subsequently, the year-to-year residuals from these average damage levels were regressed against fast, inciting factors related to disturbance occurrence.
... Applications can be found in medical science ( Shao et al., 2007;Trujillano et al., 2009), quality management ( Srdoc et al., 2007), agriculture (Debeljak et al., 2007;Kocev et al., 2009), water management ( Bhattacharya and Solomatine, 2005) and wave forecasting (Etemad-Shahidi and Mahjoobi, 2009;Bonakdar and Etemad-Shahidi, 2011;Jain et al., 2011). Although MTs have been regularly implemented in terrestrial ecology for describing and modeling population dynamics ( Stankovski et al., 1998;Demsar et al., 2006;Jurc et al., 2006;Ogris and Jurc, 2010), their applications related to modeling ecological processes in aquatic ecosystems are restricted. These studies have focused on the influence of environmental conditions on diatom assemblage abundance ( Kocev et al., 2010;Naumoski and Mitreski, 2010), the effect of physical and biological factors on the spatial distribution of a sea cucumber ( Dzeroski and Drumm, 2003), changes in the biomass of algal species (Dzeroski, 2001), and the phytoplankton dynamics of N. Adriatic Sea ( Volf et al., 2011). ...
... In order to further demonstrate the proposed method, five measures of forecasting performance are introduced [34], [45], [46], including mean absolute percentage error (MAPE), root MSE (RMSE), Teil's inequality coefficient (TIC), Teil's U -statistics (TUS), and modeling efficiency (ME). These indicators are all based on forecast residuals and are widely employed in the realm of forecasting practice. ...
Article
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In engineering practice, a system's behavior constantly changes over time. To predict the behavior of a complex engineering system, a model can be built and trained using historical data. This paper addresses the forecasting problems with a belief rule base (BRB) to trace and predict system performance in a more interpretable and transparent way. More precisely, it extends the BRB method to handle a system's behavior prediction, and a new prediction model based on BRB is presented, which can model and analyze prediction problems using not only numerical data but human judgmental information as well. The proposed forecasting model includes some unknown parameters that can be manually tuned and trained. To build an effective BRB forecasting model, a multiple-objective optimization model is provided to locally train the BRB prediction model by minimizing the mean square error (MSE). Finally, a practical case study is provided to illustrate the detailed implementation procedures and examine the feasibility of the proposed approach in engineering application. Furthermore, the comparative studies with other state-of-the-art prediction methods are carried out. It is shown that the proposed model is effective and can generate better prediction in terms of accuracy, as well as comprehensibility.
... and by Luther et al. (1997) for Acleris variana (Fern.). Ogris and Jurc (2010) recently presented a correlation model using a multivariate regression tree to predict potential sanitary fellings of bark beetle-attacked Norway spruce based on 21 climate, soil and forest variables. Despite several restrictions, such as the high demands regarding data quality or the limited geographical transferability, such multiple linear regressions continue to be widely used. ...
Article
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Natural disturbances play a key role in ecosystem dynamics and are important factors for sustainable forest ecosystem management. Quantitative models are frequently employed to tackle the complexities associated with disturbance processes. Here we review the wide variety of approaches to modelling natural disturbances in forest ecosystems, addressing the full spectrum of disturbance modelling from single events to integrated disturbance regimes. We applied a general, process-based framework founded in disturbance ecology to analyze modelling approaches for drought, wind, forest fires, insect pests and ungulate browsing. Modelling approaches were reviewed by disturbance agent and mechanism, and a set of general disturbance modelling concepts was deduced. We found that although the number of disturbance modelling approaches emerging over the last 15 years has increased strongly, statistical concepts for descriptive modelling are still largely prevalent over mechanistic concepts for explanatory and predictive applications. Yet, considering the increasing importance of disturbances for forest dynamics and ecosystem stewardship under anthropogenic climate change, the latter concepts are crucial tool for understanding and coping with change in forest ecosystems. Current challenges for disturbance modelling in forest ecosystems are thus (i) to overcome remaining limits in process understanding, (ii) to further a mechanistic foundation in disturbance modelling, (iii) to integrate multiple disturbance processes in dynamic ecosystem models for decision support in forest management, and (iv) to bring together scaling capabilities across several levels of organization with a representation of system complexity that captures the emergent behaviour of disturbance regimes
... Climate change projections for Scandinavia also predict a shift in the geographical distribution of Norway spruce and with this a shift in the distribution of its pests (Williams and Liebhold, 2002). According to these predictions, the living range of Ips typographus has the potential to move 600 km north of its current range (Ogris and Jurc, 2010). A change in forest composition and structure can in some cases lead to a high percentage of susceptible mature, large host trees and decreased overall heterogeneity (Jenkins, et al. 2008). ...
Conference Paper
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As insects have short life cycles and are sensitive to temperature variances, even a small change in climate has the potential to influence their distribution and abundance. An increase in temperature and precipitation can affect both their reproductive potential and their dispersal (Ayres and Lombardero, 2000). Some insects utilise dead or damaged trees as breeding grounds and with the right environmental conditions their numbers can drastically increase causing an epidemic that can become economically devastating, especially for the forest industry (Jönsson and Barring, 2010).This is the case especially when considering some herbivorous insect species such as bark beetles (Coleoptera: Curculionidae, Scolytinae), which prefer mature, large diameter host trees. Bark beetles are also known to act as host to several fungus species, some of which can also be damaging to the economic value of the trees. Large bark beetle outbreaks generally happen after storms or strong winds cause lot of windfall, offering the beetles plenty of suitable breeding places (Jönsson and Barring, 2010). When windfall happens in conjunction with an increase in temperature, as predicted by climate chance projections, beetle numbers can be expected to rapidly increase as the insects go on to produce two generations per year instead of current one generation per year.
... and by Luther et al. (1997) for Acleris variana (Fern.). Ogris and Jurc (2010) recently presented a correlation model using a multivariate regression tree to predict potential sanitary fellings of bark beetle-attacked Norway spruce based on 21 climate, soil and forest variables. Despite several restrictions, such as the high demands regarding data quality or the limited geographical transferability, such multiple linear regressions continue to be widely used. ...
Article
Natural disturbances play a key role in ecosystem dynamics and are important factors for sustainable forest ecosystem management. Quantitative models are frequently employed to tackle the complexities associated with disturbance processes. Here we review the wide variety of approaches to modelling natural disturbances in forest ecosystems, addressing the full spectrum of disturbance modelling from single events to integrated disturbance regimes. We applied a general, process-based framework founded in disturbance ecology to analyze modelling approaches for drought, wind, forest fires, insect pests and ungulate browsing. Modelling approaches were reviewed by disturbance agent and mechanism, and a set of general disturbance modelling concepts was deduced. We found that although the number of disturbance modelling approaches emerging over the last 15 years has increased strongly, statistical concepts for descriptive modelling are still largely prevalent over mechanistic concepts for explanatory and predictive applications. Yet, considering the increasing importance of disturbances for forest dynamics and ecosystem stewardship under anthropogenic climate change, the latter concepts are crucial tool for understanding and coping with change in forest ecosystems. Current challenges for disturbance modelling in forest ecosystems are thus (i) to overcome remaining limits in process understanding, (ii) to further a mechanistic foundation in disturbance modelling, (iii) to integrate multiple disturbance processes in dynamic ecosystem models for decision support in forest management, and (iv) to bring together scaling capabilities across several levels of organization with a representation of system complexity that captures the emergent behaviour of disturbance regimes.
... Forest management can alter forest predisposition by shaping the forest stands and the landscape dynamics, and reactive strategies such as salvage and sanitary cutting can be of importance for modifying an outbreak pattern (J€ onsson et al., 2013). In a study in Slovenia, Ogris and Jurc (2010) predicted an increased need of sanitary felling due to I. typographus in response to climate change. Model simulations of adaptive management strategies (tree species change) revealed that there can be a considerable time lag between the start of adaptation measures and a decrease in bark beetle-caused damage (Seidl et al., 2009). ...
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Bark beetles that feed on live tissue are major contributors to global tree mortality and can also cause declines in crop systems. Many bark beetle life history traits that influence population success are temperature dependent, and climate change will therefore cause significant alterations to bark beetle population dynamics, both positive and negative. Many species have responded to increased temperature and reduced precipitation in the past decade, and projected global changes will undoubtedly continue to manifest through alterations in bark beetle population outbreaks and shifts in species distributions. To adequately manage future forest and agriculture ecosystems, knowledge of potential bark beetle impacts in a changing climate will be required. Despite the importance of climate in predicting bark beetle outbreaks, only six species have sufficient information for development of mechanistic and statistical models. We review mechanistic phenology models that incorporate thermally dependent physiological processes that control survival and seasonality (i.e., development, diapause, cold tolerance), and ecosystem models that describe the effect of climate and host plant conditions on bark beetle population abundance using statistical and analytical techniques. We discuss commonalities that may facilitate future modeling frameworks and identify limitations that could hinder projections in future climates.
... The 95 high susceptibility of pure spruce stands compared to spruce 96 stands with admixed tree species is shown by numerous studies 97 (e.g. Klopcic et al., 2009;Ogris and Jurc, 2010;Overbeck and 98 Schmidt, 2012;Hlásny and Turčáni, 2013). Norway spruce trees 99 under physiological stress such as from drought, fungal diseases 100 or intense competition in overly dense stands are particularly suit-101 able habitat for bark beetles (e.g. ...
... In central Europe Norway spruce is often grown outside its natural geographical range. Bark beetles are predicted to do greater damage to Norway spruce that has been planted out of its native range on soils rich in N, P and K in the lowlands of Slovenia in a future climate (Ogris and Jurc 2010). Also, a climate driven model predicts the damage levels of I. typographus in Austria to be more than three times higher in 2099 than in 1990-2004 and a substantial time-lag between the start of adaptation measures and a decrease in damage (Seidl et al. 2009). ...
... (Dutilleul et al. 2000;Becker and Schröter 2001;Gilbert et al. 2005;Klopcic et al. 2009;Kautz et al. 2013;Ogris and Jurc 2010;Lausch et al. 2011;Marini et al. 2012;Overbeck and Schmidt 2012;Albrecht et al. 2012;Thom et al. 2013;Mezei et al. 2014). ...
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Mountain forests constitute one of the most diverse ecosystems, not only in Europe but also all over the world. Mountain ranges, which frequently encompass multiple countries, constitute a unique link between various natural areas, which are very often completely different from the historical point, or which are characterized by different use and management types. Although the role of mountain forests is relatively well recognized nowadays, in the distant past, these areas were poorly penetrated, mainly due to the unfavourable climate and natural topography, which discouraged not only from settling down but also from moving around. Despite the fact that mountains had been the object of interest of mining, weaving, and glassmaking industries for hundreds of years, dramatic changes in the stands in these areas were sealed by the industrial revolution in the 18th and 19th centuries. The purpose of this paper is the analysis of forest dieback process in the mountain ranges of Sudetes and Western Carpathians placed in Poland. Stress factors have been divided into three main groups, however, it should be remembered that it is a very simplified division and some factors could be partially found in the anthropogenic, as well as biotic, and even abiotic factor groups. Neither the beginning nor the end of deforestation process was defined precisely in the study, which was deliberate in taking into account constant changes in the ecosystems. Generally, three periods may be distinguished here, regarding the spruce forests dieback process. Typically anthropogenic deforestation, caused by the industrialization of the areas during the industrial revolution and earlier, deforestation in the years 1970–1980 and partially before the year 2000 (Western Carpathians) caused by a set of various stress factors and the latest period, that is, generally understood climate change. The last several years have particularly contributed to the expansion of detailed knowledge about the dependencies and the influence of abiotic, biotic, and anthropogenic factors on the health condition of spruce trees. Although models have already been developed, which describe the course of insect outbreaks, the growth and health condition of spruces, or climate factors, no model has been developed so far that would allow to depict the process of hitherto deforestation, and to enable modelling the forthcoming changes. It seems that the development of such tool, not only from the forest management point of view, would constitute a milestone on the way to precision forestry.
... For example, windthrown trees can contribute to increased fuel loading, leading to enhanced potential for fire disturbance (Myers and van Lear, 1998;Cannon et al., 2019). Similarly, the volume of downed timber may provide breeding material for bark beetles that then spread to surrounding stands and cause direct effects there (Wichmann and Ravn, 2001;Fettig et al., 2007;Ogris and Jurc, 2010;Stadelmann et al., 2013). There are also important interactions between wind damage and drought (Allen et al., 2015;Csill ery et al., 2017) and insect and wind damage (Taylor and MacLean, 2009) (Hale et al., 2015), for Glen Affric semi-natural pine forest in northwest Scotland (Quine, 2003b). ...
Chapter
Wind is an important disturbance agent in many natural forests and a major cause of destructive damage in managed forests around the world. The interaction of the wind with trees and the processes leading to tree breakage and uprooting are complex and depend on many factors. Furthermore, these processes operate at a range of temporal scales from seconds to decades and spatial scales from centimeters to 100s of kilometers. This chapter attempts to bring order to this complex issue and to provide the reader with a straightforward understanding of the key factors and mechanisms involved in wind disturbance in forests. It also provides a set of key mathematical expressions for predicting the likelihood of wind damage in different circumstances. It also discusses how this likelihood of damage changes with location, topography, soil type, species, and management operations and the consequences of damage for forest ecosystem functioning. The chapter places forest wind disturbance within an understanding of the global wind climate and what the consequences of the future wind climate might be for both natural and managed forests.
... Yet, while some authors promoted this practice (e.g. Ogris and Jurc, 2010), the efficacy of this practice under warmer climate was questioned (Dobor et al., 2020b). Studies aimed at direct manipulation of MPB populations, specifically in response to a changing climate, were focused on the use of semiochemicals and insecticides for protection of high value trees and stands (Keane et al., 2017;Seybold et al., 2018). ...
Article
Tree-killing bark beetles are globally the most destructive forest pests and their impacts have increased in recent decades. Such an increase has been consistently reported from Europe and North America, and it is, with high confidence, driven by climate change. We investigated how the scientific community in both continents responded to this situation by conducting a comprehensive search of the Scopus database from 1970 to 2020. Studies that investigated interactions between climate change and two prominent bark beetles in Europe and North America, the European spruce bark beetle Ips typographus (ESBB) and the mountain pine beetle Dendroctonus ponderosae (MPB), were identified. We used several hierarchical search criteria, starting from general aspects of pest – climate change interactions, to studies with clear implications for management and policies. We found that authors investigating the two bark beetle species mentioned climate change in publications beginning in 1998, and have constituted 8.9 and 13.8 % of all studies on ESBB (N = 987) and MPB (N = 1479) recorded in Scopus. However, only part of these studies addressed climate change as a fundamental or integral part of their research design (59.1 % in ESBB and 38.7 % in MPB). We identified 30 studies on ESBB and 50 studies on MPB which informed efforts towards improving bark beetle management strategies to address climate change-affected ecosystem dynamics. Publications on both insects consistently highlighted the importance of vegetation management aiming to reduce the risk and severity of outbreaks and prevent large-scale population expansion. Only a minor portion of studies placed their findings into the context of relevant policies and legislation, and this connection was particularly lacking in studies on MPB. We conclude that research on bark beetle management under climate change has received inadequate attention and it lags behind observed and foreseen global-scale impacts. We suggest that focused and applied research with clear management implications is needed to develop new climate-adapted and evidence-based management strategies.
... particularly, however, machine learning algorithms demonstrated high capacity to predict physical condition of trees associated with insect damage, such as to forecast tree death or survival following the attack of Thecodiplosis japonensis Uch. et Inou where artificial neural networks (Park and Chung, 2006) were used to predict potential sanitary fellings of bark beetle-attacked Norway spruce, based on 21 climate, soil, and forest variables through multivariate regression trees (Ogris and Jurc, 2010) and also to estimate defoliation of Scots pine stands in western Poland, by k-nearest neighbors, random forest, and support vector machines as well as Sentinel-2 vegetation indices (Hawryło et al., 2018). White pines (genus Pinus, subgenus Strobus) are common tree species in temperate forest ecosystems. ...
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Insect damage to cones and seeds has a strong impact on the regeneration of conifer forest ecosystems, with broader implications for ecological and economic services. Lack of control of insect populations can lead to important economic and environmental losses. Pinus strobiformis is the most widespread of the white pines in Mexico and is widely distributed throughout the mountains of northern Mexico. Relatively few studies have examined insect damage to the cones and seeds of these pines, especially in Mexico. In this study, we therefore analyzed insect damage to cones and seeds of P. strobiformis in Mexico by using X-ray and stereomicroscopic analysis. The specific objectives of the study were (a) to characterize insect damage by measuring external and internal cone traits, (b) to assess the health of seeds and cones of P. strobiformis in the Sierra Madre Occidental, Mexico, and (c) to estimate the relative importance of the effects of different environmental variables on cone and seed damage caused by insects. We found that 80% of P. strobiformis seeds and 100% of the tree populations studied had damage caused by insects. Most seeds were affected by Leptoglossus occidentalis, Tetyra bipunctata, Megastigmus albifrons, and the Lepidoptera complex (which includes Apolychrosis synchysis, Cydia latisigna, Eucosma bobana, and Dioryctria abietivorella). The cones of all tree populations were affected by some type of insect damage, with Lepidoptera causing most of the damage (72%), followed by Conophthorus ponderosae (15%), the hemipteran L. occidentalis (7%), and the wasp M. albifrons (6%). The proportion of incomplete seeds in P. strobiformis at the tree level, cone damage by M. albifrons and seed damage in L. occidentalis were associated with various climate and soil variables and with crown dieback. Thus, cone and seed insect damage can be severe and potentially impact seed production in P. strobiformis and the reforestation potential of the species. The study findings will enable managers to better identify insects that cause damage to cone and seeds. In addition, identification of factors associated with damage may be useful for predicting the levels of insect predation on seeds and cones.
... Whether increased winter time temperatures will favour insect development or not depends on the individual species (Battisti, 2004), but normally, warmer winters enhance egg survival rate (Bale et al., 2002;Leather et al., 1996). Finally, rising frequencies of drought are expected to promote bark beetle attacks (Bakke, 1983;Faccoli, 2009;Ogris and Jurc, 2010). ...
Article
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Plants, and particularly trees, are the largest source of atmospheric volatile organic compounds globally. Insect herbivory alters plant volatile emission rates and the types of compounds that are emitted. These stress volatiles are a major contribution to total plant volatile emissions during active herbivore feeding, with important implications for atmospheric chemistry processes. However, emission models do not currently have a quantitative description of plant volatile emission rates during and after insect herbivore feeding. This review provides a brief background on plant volatile organic compounds, the urgency of including biotic stress emissions in models, and a summary of plant volatile emission models and steps they have taken to incorporate stress emissions into their framework. The review ends with a synthesis of volatile emissions from trees during insect herbivory. This synthesis highlights key gaps in studied systems and measurement approaches. We provide a summary of recommendations for future work to address these gaps, improve comparability between studies, and generate the data-sets we need to develop a descriptive model of these plant stress volatile emissions. Keywords: Plant volatile emission, Volatile organic compounds, Stress plant emissions, Insect herbivory
... Unfortunately, the planting of Norway spruce trees (Picea abies) in new habitats, in most cases at lower altitudes, resulted in lower viability (Levanič et al., 2009). One of the negative consequences of this was a rise in I. typographus infestations (Ogris & Jurc, 2010). According to the work of de , in the period from 1996 to 2017, in natural or unchanged forests with a median P. abies growing stock of 5.61%, the median sanitary felling because of I. typographus was 0.025 m 3 ha −1 year −1 , while in highly changed forests, the median sanitary felling increased to 0.26 m 3 ha −1 year −1 . ...
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In recent decades, there have been an increasing number of outbreaks of Ips typographus in Europe. A large amount of sanitary felling has taken place, with significant economic and ecological consequences. In order to anticipate such large-scale outbreaks, an effective monitoring system should be set up. One important aspect of monitoring is deciding which pheromone to use. Therefore, we decided to test five different commercially available pheromone lures under different disturbance conditions: Pheroprax®, IT Ecolure Extra®, Ipstyp®, Ipsowit® and Typosan®. We investigated the ability of the pheromones to distinguish between disturbed and undisturbed locations, their cost-efficiency ratio, and side effects such as bycatch abundance and composition. We set 50 traps in two areas with sites that were disturbed and undisturbed by windstorms. We collected the catch from traps every 1–2 weeks from the end of March until the end of September in 2019. We found that IT Ecolure Extra®, Ipsowit® and ® Pheroprax® caught the most I. typographus and best showed changes in the trap catch of I. typographus throughout the whole season. There was a low amount of bycatch (<6% of the total catch) and a low number of predators (a few specimens), but some groups seem to prefer certain pheromones. The cost of the pheromones increased with their effectiveness. However, pheromone costs are low relative to the personnel costs involved in setting traps and collecting the catch. Based on all of the gathered data, we created an index which helps to assess the cost-efficiency of the five chosen commercially available pheromones. We also present guidelines on how to make such an index to assist other researchers in choosing the right pheromone for monitoring populations of I. typographus or other bark beetle species.
... P. chalcographus preferably attacks either young spruce trees or the tops and branches of older spruce trees, usually after they have suffered from previous damage caused by drought, pollutants or simultaneous attack by the I. typographus (Göthlin et al., 2000;Hedgren, 2004;Schroeder, 2013;Zúbrik et al., 2008). The relatively good capacity of P. chalcographus for host plant shifting and dispersal (Bertheau et al., 2012;Bertheau et al., 2009), together with global climatic changes that negatively affect the health status of Norway spruce stands, may result in increasing occurrence of population outbreaks of this pest in the future (Avtziz et al., 2010;Heliövaara and Peltonen, 1999;Ogris and Jurc, 2010;Verkaik et al., 2009). ...
Article
The purpose of the study was to develop, calibrate and validate a comprehensive phenological model for the spatiotemporal simulation of the seasonal development of the six-toothed spruce bark beetle, Pityogenes chalcographus (CHAPY). The validation dataset was acquired through monitoring of the bark beetle's phenology at eight sites in Slovenia in 2017 and 2018, along with air and bark temperature measurements. The predictions were made using air temperature from the INCA system (Integrated Nowcasting through Comprehensive Analysis), which is used to calculate the effective bark temperature for beetle development. Since the biology of P. chalcographus is poorly studied, a sensitivity analysis was used to pinpoint the most important model parameters. The first order (main) effect was the highest for the lower developmental threshold (DTL), while the second order (interaction, total) effect was the highest for the optimum temperature (TO). DTL was calibrated with an iterative procedure, and the best result with the lowest mean absolute error (MAE) was achieved at 7.4°C. Effective temperatures in the range between TO and the upper developmental threshold were calculated with a nonlinear function whose parameters were appropriately calibrated. The spring date threshold when the model calculation starts was calibrated with an iterative procedure and set at 9th March, which had the minimum MAE. The onset of Norway spruce infestation in spring was estimated using a lower threshold of 15.6°C for flight activity and a mean thermal sum of 216.5 degree-days (dd) from 9th March onward. The observed mean thermal sum required for total development of filial beetles was 652.8 ± 22.7°C, while the predicted mean thermal sum was 635.4 ± 31.4°C. Re-emergence of parental beetles occurred when 52.7% of the minimum thermal sum for total development was reached. The relative duration of the egg, larval and combination of the pupal and teneral adult developmental stages was 9.4%, 58.2% and 32.4%, respectively. Mass swarming concluded in the end of August when daylength was lower than 13.6 h, which was determined with the independent dataset of 1,017 pheromone traps. The diapause initiation at a daylength < 13.6 h is included in the model as an assumption. Successful hibernation of established broods is predicted by assessing the developmental stage of initiated generations at the 31st December. For validation, we compared the timing of phenological events in the field with predicted events using both 30-minute recorded data at study sites in the field and hourly data from the INCA. The time of spring swarming was estimated with a MAE of 5.6 days. The onset of infestation was predicted with a MAE of 6.0 days. The predicted onset of emergence of filial beetles was estimated with a MAE of 2.1 days. Additionally, CHAPY simulates the number of generations. CHAPY was successfully incorporated into two publicly available web applications. Development of the model revealed several knowledge gaps in P. chalcographus phenology, thus providing opportunities for further research of the second most damaging bark beetle of Norway spruce in Central Europe and for further improvement of the CHAPY model. Potential applications of the model for monitoring and management of P. chalcographus are discussed.
... Analiza dolgoletnih meteoroloških podatkov kaže, da so ekstremne vremenske razmere v zadnjih letih vse pogostejše tako na ravni Evrope (Schelhaas in sod., 2003) kot tudi v Sloveniji (Ogrin, 2007;Grecs in Kolšek, 2016) in na Postojnskem (Gozdnogospodarski …, 2012;Poročilo …, 2019). Ujmam v mnogih primerih sledijo še obsežne gradacije podlubnikov (Ogris in Jurc, 2010;Rozman in sod., 2015;Oražem, 2017). ...
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Serbian spruce (Picea omorika (Pančić) Purk.) is an endemic tree species from the Balkan Peninsula. The species also thrives in Slovenia and would be an interesting minority alternative to Norway spruce (Picea abies (L.) Karst.) on some sites. This study was carried out in a Serbian spruce plantation below Počivalnik hill, between Unec and Postojna. The trees were planted in 1988 and are currently classified as a pole stand. We measured the diameters of the trees and systematically evaluated the vitality of each tree throughout the plantation. Data processing consisted of calculating the percentage of trees of each health status for each provenance and phenotype present in the plantation, creating a plantation model, and performing an analysis of variance and Tukey's post-hoc test. We found that provenance has a significant effect on the vitality of trees but not on tree diameter. Phenotype affects both the vitality of trees and tree diameter. The correlation between phenotype and tree diameter is significant within phenotypes B (type %semidichotomy%) and C (type %serbica%). Also, the impact of phenotype on diameter increment varies between the different provenances. According to our investigations, the most suitable seed material for the Dinaric karst region of Slovenia is from the Šargan provenance (read Shargan). In terms of phenotype, types C ('serbica') and F ('argentea') seem to be the most suitable. They are also the most desirable for horticultural use.
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In recent years, the red turpentine beetle (RTB), an invasive pest species, has caused extensive pine mortality in North China. Although some studies have theoretically clarified the interference mechanism of multi-level factors with the development of RTB damage, knowledge about this mechanism from the empirical research is still limited. The aim of this study was to determine whether the primary factors influencing RTB occurrence change during different periods of RTB invasion. Stand-level variables of sample plots were obtained through field investigation and the forest resource survey data including forest stand characteristics, topographic characteristics, and soil properties. Remote sensing classified images were to develop the characteristic variables related to landscape composition and configuration around the sample plots at multiple scales. Generalized linear models (GLMs) and generalized linear mixed models (GLMMs) were used to explore the relative importance of stand-level and landscape-level variables in explaining the severity of RTB damage. Result showed that two stand-level factors, aspect and canopy density, were the best predictors of damage in the early stage of RTB invasion. The landscape-level factor, the proportion of Chinese pine ( Pinus tabuliformis ) patches, was the main predictor of damage in the middle stage of RTB invasion. The most effective spatial scale at which RTB responded to landscape pattern was 250 m. With the increasing severity of RTB damage, the factors driving RTB invasion have shifted from the stand-level to the landscape-level. This calls for an urgent consideration of multi-scale processes to address the changing disturbance regimes in ecosystem management.
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Decision tree learning is among the most popular machine learning techniques used for ecological modelling. Decision trees can be used to predict the value of one or several target (dependent) variables. They are hierarchical structures, where each internal node contains a test on an attribute, each branch corresponding to an outcome of the test, and each leaf node giving a prediction for the value of the class variable. Depending on whether we are dealing with a classification (discrete target) or a regression problem (continuous target), the decision tree is called a classification or a regression tree, respectively. The common way to induce decision trees is the so-called Top-Down Induction of Decision Tress (TDIDT). In this chapter, we introduce different types of decision trees, present basic algorithms to learn them, and give an overview of their applications in ecological modelling. The applications include modelling population dynamics and habitat suitability for different organisms (e.g. soil fauna, red deer, brown bears, bark beetles) in different ecosystems (e.g. aquatic, arable and forest ecosystems) exposed to different environmental pressures (e.g. agriculture, forestry, pollution, global warming).
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Los socio-ecosistemas forestales vascos tienen un elevado potencial para garantizar el mantenimiento de las funciones y servicios de sus ecosistemas, y por lo tanto, para ayudar en la mitigación del cambio climático y global. Estos ecosistemas forestales ocupan más de la mitad del territorio, con dominio de las plantaciones de coníferas, si bien es cierto que en los últimos diez años se observa una tendencia de aumento tanto de los bosques naturales, como de las plantaciones de eucalipto. A fin de orientar las decisiones presentes que ayuden en la búsqueda conjunta de soluciones positivas de cara al futuro, es importante fomentar procesos de gestión democrática y participativa.
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Natural disturbances play a key role in ecosystem dynamics and are important factors for sustainable forest ecosystem management. Quantitative models are frequently employed to tackle the complexities associated with disturbance processes. Here we review the wide variety of approaches to modelling natural disturbances in forest ecosystems, addressing the full spectrum of disturbance modelling from single events to integrated disturbance regimes. We applied a general, process-based framework founded in disturbance ecology to analyze modelling approaches for drought, wind, forest fires, insect pests and ungulate browsing. Modelling approaches were reviewed by disturbance agent and mechanism, and a set of general disturbance modelling concepts was deduced. We found that although the number of disturbance modelling approaches emerging over the last 15 years has increased strongly, statistical concepts for descriptive modelling are still largely prevalent over mechanistic concepts for explanatory and predictive applications. Yet, considering the increasing importance of disturbances for forest dynamics and ecosystem stewardship under anthropogenic climate change, the latter concepts are crucial tool for understanding and coping with change in forest ecosystems. Current challenges for disturbance modelling in forest ecosystems are thus (i) to overcome remaining limits in process understanding, (ii) to further a mechanistic foundation in disturbance modelling, (iii) to integrate multiple disturbance processes in dynamic ecosystem models for decision support in forest management, and (iv) to bring together scaling capabilities across several levels of organization with a representation of system complexity that captures the emergent behaviour of disturbance regimes.
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By using an empirical GIS model, the potential spatial changes of forest vegetation driven by expected climate change have been analysed. Based on the three different scenarios predicting climate warming in Slovenia (the mean, pessimistic and optimistic scenarios), the simulation showed that the share of vegetation types will be altered under the impacts of climate change, and the shift of vegetation belts upwards might be expected. By the year 2100, the share of mesic beech forests is likely to decrease. From ecological, - nature-conservation - and forest-management points of view, the predicted decrease of the share of Dinaric fir-beech forests is especially important. The model predicts an increase of the share of thermophilous forests from the present 14% to a range between 50% (according to the optimistic scenario) and 87% (according to the pessimistic scenario). A significant part of the coniferous forest with Picea abies and Abies alba predominating might be converted to deciduous forests.
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Extreme weather conditions, namely droughts, heat waves, heavy rains, floods, and landslides are becoming more frequent globally and in Serbia as a result of climate change. Generally, various parts of human society are affected by changing climate conditions. Forest ecosystems are one of the most sensitive systems to weather and climate. In that sense, small changes may lead to large disturbances including forest decline, outbreaks of insect pests and diseases and eventually mortality. In Serbia, the average temperature in forest ecosystems of the most important and abundant forest tree species has risen for more than 1°C in the last thirty years (1990-2019) in comparison to the previous period (1961-1990). During the last thirty years, the northern and western parts of Serbia experienced an increase in precipitation as opposed to the southern and eastern parts of the country. If one takes a closer look at the climate within a particular forest stands, it would seem that the effect of precipitation decrease is stronger in less humid parts of a tree species range. In this paper, we discuss various aspects of climate change impacts on forests and forestry, including forest ecology, genetics, physiology, pests and diseases, ground vegetation, monitoring, reporting and verification system, climate change litigation and perspectives of forests in the 21 st century in Serbia.
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1 Einleitung 1.1 Der Buchdrucker als Forstschädling 1.2 Entstehung von Massenvermehrungen 2 Biologie des Buchdruckers 2.1 Bruttätigkeit und Entwicklung 2.2 Überwinterung des Buchdruckers 2.3 Assoziierung von Bläuepilzen mit dem Buchdrucker 3 Ausbreitung 4 Wechselwirkungen des Käfers mit der Wirtsbaumart Fichte 4.1 Wirtsbaumfindung 4.2 Abwehrverhalten der Fichte gegen Borkenkäferbefall 4.3 Stressfaktoren der Fichte 5 Natürliche Gegenspieler von Ips typographus 6 Integriertes Borkenkäfermanagement
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O Projeto Manejo dos Recursos Naturais da Várzea (ProVárzea) é o projeto que o Ibama submeteu ao Programa Piloto para a Proteção das Florestas Tropicais do Brasil (PPG7), coordenado pela Secretaria de Coordenação da Amazônia do Ministério do Meio Ambiente com o objetivo de estabelecer as bases científica, técnica e política para a conservação e manejo ambiental e socialmente sustentáveis dos recursos naturais das várzeas da região central da bacia amazônica com ênfase em recursos pesqueiros. A ênfase na pesca é consistente com o objetivo geral de promover o uso racional dos recursos da várzea, uma vez que esta atividade é base da dieta e principal fonte de renda da população ribeirinha. Além disso, o recurso pesqueiro representa a síntese das interações entre os diversos componentes do ecossistema de várzea. Os principais problemas abordados pelo ProVárzea foram: 1. Degradação ambiental. A várzea é um ecossistema ameaçado pela destruição de ha-bitats, pesca não manejada e exploração madeireira predatória. A destruição de habitats (especialmente, remoção da cobertura florestal) para implantação de fazendas de gado bovino e criação de búfalos reduz a oferta de alimento e abrigo para os peixes, afetando severamente a cadeia produtiva do ecossistema através do impacto sobre a vegetação mar-ginal, principalmente macrófitas aquáticas. Tanto o consumo direto pelo búfalo, como o pisoteio, reduz a área desta vegetação, importante como habitat para os peixes, principal-mente durante a seca nas áreas alagáveis. 2. Sobrepesca. Particularmente nas espécies de peixe que têm sofrido maior esforço pesqueiro como a piramutaba (Brachyplatystoma vailantii), o tambaqui (Colossoma ma-cropomum) e o pirarucu (Arapaima gigas). Essas espécies têm em comum o fato de ser-em muito apreciadas para o consumo, atingirem tamanhos relativamente grandes, e po-ssuírem uma baixa taxa de crescimento. 3. Conflitos sociais. A redução dos estoques do pescado tem causado conflitos entre os pescadores profissionais e ribeirinhos pelo direito de uso dos recursos. A escassa presença governamental na região tem contribuído para agravar esses conflitos. Na ausência do Governo, as organizações locais (comunidades ribeirinhas) estão desenvolvendo sistemas de manejo fora do sistema formal de gestão. Embora essas iniciativas tenham aspectos positivos e inovadores, faltam amparo legal, embasamento científico e mecanismos para integrá-las em um modelo para a gestão dos recursos naturais na várzea. 4. Escassez de sistemas de manejo. Embora haja vários estudos básicos sobre a ecologia de várzea (estrutura, funcionamento e biodiversidade), há uma escassez de estudos apli-cados e sistemas de manejo efetivos para esse ambiente. Como conseqüência, as práticas
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Bugmann, H. 2007. The influence of changes in climate and land-use on regeneration dynamics of Norway spruce at the treeline in the Swiss Alps. Silva Fennica 41(1): 55–70. Recent changes of climate and land-use are often regarded to affect the European Alpine region substantially and to trigger an increase in the elevation of the upper treeline. The patterns of tree invasion on a subalpine meadow at 1900 m a.s.l. in Sedrun, Canton Grisons, Switzerland, were studied in order 1) to reconstruct the process of tree establishment and tree–growth dynamics in space and time, and 2) to evaluate the influence of site properties, land-use change and climate on these processes. Dendroecological analysis of 105 Norway spruce combined with an assessment of 48 vegetation plots and 17 soil profiles revealed that the trees were established in one main period (1965–1980s), starting 15 years after the abandonment of the agricultural use of the meadow, and that there is a pronounced environmental gradient along the forest-meadow ecotone. Tree establishment and height growth were favoured close to the former forest edge, but all saplings irrespective of their distance to the forest edge and their age showed increased radial growth since 1990, coinciding with a period of higher summer temperatures in the region. Therefore, we conclude that the observed tree-line dynamics in Sedrun are the result of both land-use and climate change: Tree establishment was triggered by the abandonment of the agricultural use of the meadow, and strongly favoured by particularly good growing conditions in a warm decade, which illustrates the sensitivity of conifers near the alpine tree-line to temperature fluctuations.
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Storms are important disturbance factors in the development of forest ecosystems. They trigger definite changes in vegetation composition and hence also in the associated insect fauna. Three windthrow areas created by the storm Vivian in 1990 in alpine spruce forests were each subdivided into a cleared and an uncleared treatment. The abundance of the three most frequent beetle families (Scolytidae, Cerambycidae, and Buprestidae) was monitored with two different trap types during six summer periods within the first 10 years after the windthrow. The large supply of breeding substrate triggered a distinct increase in insect abundance and in the species richness of this guild (except for the number of buprestid species) over a period of approximately five years. The first group reaching peak numbers were the Scolytidae (in 1992), followed by the Buprestidae (1994) and then by the Cerambycidae (1996). Ips typographus, the most important bark beetle, peaked in the third season after the storm (1992). The maximum numbers of saproxylic species were trapped in June/early July. In uncleared windthrow areas beetle abundance as well as species numbers were generally higher than in cleared treatments. In the windthrow areas, cerambycid and buprestid species were 30-500 times more abundant than in an adjacent intact forest. Their species number exceeded that in the forest 2-4 times. To promote saproxylic species in general as well as endangered species of saproxylics, some parts of windthrow areas should be cleared and others left uncleared. The controversy about protecting the forest and promoting biodiversity is discussed.
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Forest insects and pathogens are the most pervasive and important agents of disturbance in North American forests, affecting an area almost 50 times larger than fire and with an economic impact nearly five times as great. The same attributes that result in an insect herbivore being termed a "pest" predispose it to disruption by climate change, particularly global warming. Although many pest species have co-evolved relationships with forest hosts that may or may not be harmful over the long term, the effects on these relationships may have disastrous consequences. We consider both the data and models necessary to evaluate the impacts of climate change, as well as the assessments that have been made to date. The results indicate that all aspects of insect outbreak behavior will intensify as the climate warms. This reinforces the need for more detailed monitoring and evaluations as climatic events unfold. Luckily, we are well placed to make rapid progress, using software tools, databases, and the models that are already available.
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Abstract 1 We analysed time series of spruce bark beetles (Nt) caught in pheromone traps from 1979 to 2000 in approximately 100 localities throughout south-east Norway. 2 The analysis was performed at two spatial scales (whole area and 12 subregions), and included additional analyses of the time-series sequences before and after a large windfelling (1987) that appeared to induce a shift in the dynamics. 3 Regression of Rt (logarithmic per-capita growth rate) on Nt − d indicated that the endogenous dynamics were dominated by lag 1 density dependence. This was particularly so in the sequence after the large windfelling (R2 = 0.79), probably due to intraspecific competition for breeding substrate. 4 The sequence before the windfelling (1979–1987) was declining without significant density dependence. We suggest this to be a transition period, reflecting a drop in carrying capacity due to depletion of susceptible trees during the preceding outbreak period (1970s) and a drop in beetle number to below the density required to kill trees. 5 Windfelling (Wt − 1) appears to be an important predictor of the dynamics; however, it was difficult to evaluate the statistical significance of this factor due to only one large windfall event. 6 The weak influence of drought stress (Dt − 1) could be due to the absence of severe drought periods within the time series.
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1 Attack density and breeding success of bark beetles (Coleoptera: Scolytidae) and the abundance of their predators were studied at forest-clearcut edges in southern Finland on Norway spruce, Picea abies, bolts placed at different distances from a forest-clearcut edge. 2 Attack densities of two species, Hylurgops palliatus and H. glabratus, increased markedly towards the forest interior. The breeding success of H. palliatus was increased with increasing distance from the stand edge. None of the recorded 10 bark beetle species was distinctly abundant near the edge, but Pityogenes chalcographus appeared to prefer this zone. 3 There were no significant differences in numbers of bark beetle predators between the forest interior and the edge. Forest-clearcut edge had a significant effect on the desiccation of sample bolts. 4 Thus, forest edge is likely to affect the colonization behaviour and breeding success of bark beetles via host material properties.
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Using a simple temperature-driven multistage threshold developmental model, we analyse the impact of climate change on the life cycle dynamics of the spruce bark beetle Ips typographus. The completion of a full reproductive second generation within a single year (bivoltinism) might increase the risk of devastating bark beetle outbreaks. A network of more than 300 climate stations, comprising time series of air temperatures both observed as well as simulated using regional climate models, is exploited on the country scale. It is shown that current conditions strongly favor univoltine behavior, whereas climate scenarios predict almost strictly bivoltine behavior for southern Norway in 2071-2100. The dynamics of this threshold phenomenon is investigated in detail. Using a logistic regression, the impact of regional warming can be described as a northward movement of bivoltinism by some 600 kilometres. Thus, the risk for Norway spruce infestations in Scandinavia may be drastically increased over the next decades.
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Spatio-temporal analyses of non-epidemic bark beetle populations may provide insight in dynamics predisposing for outbreaks. The present article presents a spatio-temporal analysis of the population dynamics of Ips typographus based on pheromone trap data from southeast and mid-Norway in the post-epidemic period 1979–2002. The analyses include regression analyses, hierarchical cluster analysis, and analysis of spatial synchrony of beetle time series and climatic data by means of nonparametric spatial covariance functions. The mean abundance of beetles declined linearly with latitude. In addition, the time series means were higher in areas with high forest productivity and rocky soils predisposed to drought. The time series patterns differed significantly between northern and southern study areas. The regional synchrony of the time series was fairly high (0.38), indicating that some large-scale climatic factor may influence the dynamics. Windfelling was the external variable showing the most parallel pattern of correlation to the beetle dynamics. We thus posit that large windfall events may be a major instigator and synchronizer of beetle outbreaks in areas subjected to regionalized weather systems.
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In this paper, we analyze the phenology of spruce bark beetles (Ips typographus and Pityogenes chalcographus) in the Dinaric mountain forests of southwestern Slovenia. The study of I. typographus took place from 1986 to 2000, while that of P. chalcographus took place from 1993 to 2000 in an area characterized as a Dinaric Fir-Beech forest community (Abieti-Fagetum dinaricum) on the Karst plateau (447–751 m above sea level). On the studied area Norway spruce (Picea abies) has been planted between 60 and 90 years ago on approximately 1000 ha. Frequent catastrophic weather conditions are characteristic for this area, followed by an increased trophic capacity of the forest for the various bark beetle species. The population density of spruce bark beetles was monitored at five locations at varying exposures using commercial pheromones (Pheroprax® and Chalcoprax®) in traps under the trade name Theysohn. Both species studied (I. typographus and P. chalcographus) have a relatively high abundance and have two main generations per year; both species may also produce two sister generations. Data on some environmental factors as well as data on bark beetle catches have been collected and then analyzed to model the dependence of spruce bark beetle catches on the environmental factors. The machine learning methodology of liner regression as well as model tree induction was used for this purpose. The following attributes were used to analyze the occurrence of both species of bark beetle: position (NW, NE, W, E, N and S), age of pheromone, number of days since last monitoring, average monthly temperature, monthly precipitation, month and previous number of bark beetles. There was a strong correlation between a high population density of I. typograpus and Northeast (NE) and position and a high density of populations of P. chalcographus and West (W) and North (N) positions.
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AIDS risk behavior and attitudes towards safer sex were studied in a sample of 666 African American and 626 European American women. Condom use, AIDS-related knowledge, risk perception, self-efficacy beliefs, attitudes and perceived partner attitudes, and an assertive coping style were analyzed with regard to mean differences and predictive power in both ethnic groups. Compared to European American women, African American women had less knowledge and lower self-efficacy beliefs towards safer sex behavior, but they perceived themselves to be at more risk and reported greater condom use. Further, ethnicity was found to moderate the effects of the psychological predictors on safer sex behavior. This moderator effect was tested using a structural equation modeling design. In both groups, risk perception was the strongest predictor of condom use. Among African American women, social-cognitive barriers (e.g. low self-efficacy beliefs, negative attitude towards condom use) worked as a second predictor and mediator of the effects of risk perception on condom use. In contrast, among European American women, social-cognitive factors had no effect on condom use. In general, prediction of safer sex behavior was stronger among African American women.
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The mountain pine beetle, Dendroctonus ponderosae Hopkins, is a significant ecological force at the landscape level. The majority of the life cycle is spent as larvae feeding in the phloem tissue (inner bark) of host pine trees. This feeding activity eventually girdles and kills successfully attacked trees (Amman and Cole 1983, Furniss 1997). Outbreaks of this insect can be truly spectacular events (Fig. 1A; Amman and Logan 1998). Most western pines are suitable hosts for this insect, but ponderosa pine, Pinus ponderosae Lawson, and lodgepole pine, Pinus contorta Douglas, currently are the most important host species. The distribution of the beetle generally reflects this primary host range, although lodgepole pine extends further north and ponderosa pine extends further south than the current geographic range of the beetle. The mountain pine beetle is a native insect, having co-evolved as an important ecological component of western pine forests. The inter-relationship between beetle-caused mortality and subsequent fire has resulted in a basic ecological cycle for many western forests (Schmidt 1988).
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Temperature-dependent development of the egg, larval, and pupal life-stages of the mountain pine beetle (Dendroctonus ponderosae Hopkins) was described using data from constant-temperature laboratory experiments. A phenology model describing the effect of temperature on the temporal distribution of the life-stages was developed using these data. Phloem temperatures recorded in a beetle-infested lodgepole pine (Pinus contorta Douglas) were used as input to run the model. Results from model simulations suggest that inherent temperature thresholds in each life-stage help to synchronize population dynamics with seasonal climatic changes. This basic phenological information and the developed model will facilitate both research and management endeavors aimed at reducing losses in lodgepole pine stands caused by mountain pine beetle infestations.
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A generalized form of the cross‐validation criterion is applied to the choice and assessment of prediction using the data‐analytic concept of a prescription. The examples used to illustrate the application are drawn from the problem areas of univariate estimation, linear regression and analysis of variance.
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Projected climate warming will potentially have profound effects on the earth's biota, including a large redistribution of tree species. We developed models to evaluate potential shifts for 80 individual tree species in the eastern United States. First, environmental factors associated with current ranges of tree species were assessed using geographic information systems (GIS) in conjunction with regression tree analysis (RTA). The method was then extended to better understand the potential of species to survive and/or migrate under a changed climate. We collected, summarized, and analyzed data for climate, soils, land use, elevation, and species assemblages for >2100 counties east of the 100th meridian. Forest Inventory Analysis (FIA) data for >100 000 forested plots in the East provided the tree species range and abundance information for the trees. RTA was used to devise prediction rules from current species-environment relationships, which were then used to replicate the current distribution as well as predict the future potential distributions under two scenarios of climate change with twofold increases in the level of atmospheric CO2. Validation measures prove the utility of the RTA modeling approach for mapping current tree importance values across large areas, leading to increased confidence in the predictions of potential future species distributions. With our analysis of potential effects, we show that roughly 30 species could expand their range and/or weighted importance at least 10%, while an additional 30 species could decrease by at least 10%, following equilibrium after a changed climate. Depending on the global change scenario used, 4-9 species would potentially move out of the United States to the north. Nearly half of the species assessed (36 out of 80) showed the potential for the ecological optima to shift at least 100 km to the north, including seven that could move >250 km. Given these potential future distributions, actual species redistributions will be controlled by migration rates possible through fragmented landscapes.
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This report describes a program, FRAGSTATS, developed to quantify landscape structure. Two separate versions of FRAGSTATS exist: one for vector images and one for raster images. In this report, each metric calculated by GRAGSTATS is described in terms of its ecological application and limitations. Example landscapes are included, and a discussion is provided of each metric as it relates to the sample landscapes. -from Authors
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Economic Forecasting provides a comprehensive overview of macroeconomic forecasting. The focus is first on a wide range of theories as well as empirical methods: business cycle analysis, time series methods, macroeconomic models, medium and long-run projections, fiscal and financial forecasts, and sectoral forecasting. In addition, the book addresses the main issues surrounding the use of forecasts (accuracy, communication challenges) and their policy implications. A tour of the economic data and forecasting institutions is also provided. © Nicolas Carnot, Vincent Koen and Bruno Tissot 2005 and Jean-Philippe Cotis 2005.
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Nine factors were initially suggested by spruce beetle (Dendroctonus rufipennis (Kby.)) experts in Alaska as potentially important in determining the risk of a spruce beetle outbreak in stands. Factors suggested were stand hazard, size and trend of spruce beetle population in neighboring stands, degree-days in the past June, total rainfall in the past summer, and availability of four types of breeding material. Risk factors were organized into a hierarchical model of spruce beetle risk, and the relative importance of factors for determining risk was analyzed in three stages with the analytic hierarchy process. This process derives subjective estimates of factor importance values through a process of pair-wise comparisons. Analysis in stage 1 involved independent responses of two experts from Alaska. In stage 2, three experts from Alaska provided responses as a group. In stage 3, five experts, representing Alaska, British Columbia, and the Rocky Mountain region, provided responses as a group. In the final stage of analysis, stand hazard and windthrown trees were identified as the two most important factors determining risk of a spruce beetle outbreak. Hazard and windthrow were considered about equally important and together accounted for almost two-thirds of the total allocation of importance values among risk factors. The analytic hierarchy process is an effective method for eliciting expert knowledge and can be a useful tool for development of expert systems in natural resource management, where even expert knowledge is often incomplete.
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Forest insects and pathogens are the most pervasive and important agents of disturbance in North American forests, affecting an area almost 50 times larger than fire and with an economic impact nearly five times as great. The same attributes that result in an insect herbivore being termed a "pest" predispose it to disruption by climate change, particularly global warming. Although many pest species have co-evolved relationships with forest hosts that may or may not be harmful over the long term, the effects on these relationships may have disastrous consequences. We consider both the data and models necessary to evaluate the impacts of climate change, as well as the assessments that have been made to date. The results indicate that all aspects of insect outbreak behavior will intensify as the climate warms. This reinforces the need for more detailed monitoring and evaluations as climatic events unfold. Luckily, we are well placed to make rapid progress, using software tools, databases, and the models that are already available.
Article
Abstract 1 To maintain biodiversity in forests more wind-felled trees must be left where they fall. However, there is concern among forest owners that this may result in higher tree mortality caused by the spruce bark beetle, Ips typographus (L.) (Col.: Scolytidae). 2 In the 5 years following a major storm disturbance the number of standing spruces killed by I. typographus was determined in a total of 53 stands. In five of the stands all wind-thrown trees were left (unmanaged stands) and in 48 of the stands, which were situated at distances of 1.4–10.0 km from each focal unmanaged stand, the wind-felled trees were removed directly after the storm (managed stands). In the winter preceding the fifth summer new storm-fellings occurred in the study area. 3 In the 4-year period between the first and second storm-fellings, 50–322 standing trees were killed by I. typographus per unmanaged stand. There was a direct linear relationship between the number of storm-felled spruces colonized by I. typographus and the number of trees subsequently killed in the unmanaged stands. 4 Tree mortality caused by I. typographus in the unmanaged stands was almost nil in the first year, peaked in the second or third year, and decreased markedly to a low level in the fourth and fifth years. 5 In the 4-year period between the first and second storm-fellings twice as many trees were killed per ha in the unmanaged stands than in the managed stands: the average difference being 6.2 killed trees per ha, equivalent to 19% of the number of spruce trees felled by the first storm in the unmanaged stands. 6 Much higher numbers of trees were killed per ha in the stand edges than in the interiors of both the unmanaged and the managed stands.
Article
The intensity of bark beetle Ips typographus L. (Col., Scolytidae) attack on Norway spruce (Picea abies Karst.) is known to vary greatly among stands. In a control strategy approach, previous studies investigated the relationships between the variability in intensity of I. typographus attack and site characteristics such as stand age and altitude, mean tree circumference, growth rate and nearest-neighbour distance, soil moisture, pH in H2O and KCl, and soil contents of C, N, K, P, Mg, Ca, Fe, Cu, Zn and Mn. The data analysis method used in these studies was mainly the multiple linear regression, with the mean number of attacks per spruce tree in a stand as variable to explain. Previous results showed that the expected vulnerability of a Norway spruce stand to attack by I. typographus can be estimated on the basis of simple information of easy access to the forester, when the data on the stand in question is used with others for fitting the regression model. Prediction of the vulnerability of a stand, without including its data in the fitting of the model, was shown to be more approximate. Therefore, the objectives of this study were: (1) to improve the performance of models predicting the vulnerability of Norway spruce stands to attack by I. typographus, based on site characteristics; (2) to assess the stability of such predictive models when these are built using a moderate number of stands; and (3) to incorporate the resulting information in a global approach to control and prevention. Published data were re-analysed for these purposes. A jackknifed multiple linear regression procedure, in which each stand in turn is discarded when fitting the model (jackknife replication), is presented. A great variability in the models fitted, depending on the stand discarded, is observed. For instance, the number of explanatory variables retained ranges from one (i.e. soil P content, for five jackknife replications) to 10 (for one jackknife replication), for R2-values ranging from 0.5 to 1.0 and for one influential stand (i.e. the same stand characterized by an atypically low number of insect attacks compared to other stands with similar soil P content) against many influential stands. Differences between the model finally selected here using the revisited data and the models proposed earlier are discussed. A path analysis diagram is proposed for a more comprehensive modelling of Norway spruce stand vulnerability to I. typographus attack, based on site characteristics.
Article
Disturbance regimes strongly determine vegetation patterns and succession in the boreal landscape. One of the current challenges for boreal vegetation modellers is to represent disturbance agents as dynamic factors that can respond to climate change. Outbreak species of insects and plant pathogens can cause marked changes in vegetation patterns and should be incorporated into vegetation change models. This introduction to the ecology of boreal biotic disturbance agents is designed as a brief overview for global change researchers and modellers. We discuss the importance of biotic disturbance agents in the boreal forest, offer an overview of their ecology, and review modelling approaches. We illustrate these issues with examples from different systems, drawing largely from our experience with bark beetles.
Article
Global climate change is frequently considered a major conservation threat. The Earth's climate has already warmed by 0.5 degrees C over the past century, and recent studies show that it is possible to detect the effects of a changing climate on ecological systems. This suggests that global change may be a current and future conservation threat. Changes in recent decades are apparent at all levels of ecological organizations: population and life-history changes, shifts in geographic range, changes in species composition of communities, and changes in the structure and functioning of ecosystems. These ecological effects can be linked to recent population declines adn to both local and global extinctions of species. Although it is impossible to prove that climate change is the cause of these ecological effects, these findings have important implications for conservation biology. It is no longer safe to assume that all of a species' historic range remains suitable. In drawing attention to the importance of climate change as a current threat to species, these studies emphasize the need for current conservation efforts to consider climate change in both in situ conservation and reintroduction efforts. Additional threats will emerge as climate continues to change, especially as climate interacts with other stressors such as habitat fragmentation. These studies can contribute to preparations for future challenges by providing valuable input to models and direct examples of how species respond to climate change.
Article
Die Untersuchungen wurden mit Hilfe einer elektronischen Wetterstation in Verbindung mit durch spezielle Infrarotsensoren ausgersteten Pheromonfallen (nachSkatulla) durchgefhrt. So konnten Einzelanflge von Borkenkfern an die Falle zeitlich exakt registriert und gleichzeitig die zum Zeitpunkt eines jeden Anfluges herrschenden Wetterdaten erfat und abgespeichert werden. Es zeigte sich, da das Schwrmverhalten der beiden BorkenkferartenIps typographus undPityogenes chalcographus von der Lufttemperatur stark beeinflut wurde. Fr den Buchdrucker lie sich ein Temperaturminimum fr die Flugaktivitt bei 16,5C ermitteln. Die obere Temperaturgrenze fr den Schwrmflug dieser Art lag bei 30C. Beim Kupferstecher lag der untere Schwellenwert etwas hher: zwischen 16,8–17,0C. BeiP. chalcographus konnte allerdings nach oben bis 35,6C keine Beeintrchtigung der Schwrmaktivitt festgestellt werden. Beide Borkenkferarten reagierten sehr empfindlich und spontan auch auf geringfgiges Unter-bzw. berschreiten der Schwellenwerte.Single catches of bark beetles in pheromone baited traps were registered by the aid of a new instrument. It consists of an electronical weather station in connection with a pheromone trap with infrared sensors as additional equipment. So it was possible also to register weather data at the moment of every catching event. It could be shown that the flight behaviour of both species of bark beetles was influenced by air temperature.I. typographus did not fly beneath a minimum temperature of 16.5C. There was also an upper limit of 30C for flight activity of this species.P. chalcographus has a threshold of temperatures about 16.8–17C, for activity. No upper limit of temperature could be observed up to 35C. Both of them,I.typ. andP. chalc., reacted very sensitive and spontaneous to these temperature thresholds.
Article
To maintain biodiversity in forests more wind-felled trees must be left. However, there is concern among forest owners that this may result in higher tree mortality caused by the spruce bark beetle (SBB). Data from six studies on number of trees killed by the SBB in storm-disturbed stands was analysed. The studies include 16 areas, 2–346 ha in size, where wind-felled spruce trees were left. In one of the studies also stands where all wind-felled trees were removed directly after the storm were included. Few trees were killed in the first summer following the storm disturbance. In most stands the tree mortality peaked already in the second or third summer following the storm. But in five of the stands tree mortality peaked later. The number of trees killed per ha by the SBB varies much between the studied stands. There was a trend that the larger areas experienced on average higher tree mortality per ha than the smaller areas. One of the studies, including six stands, demonstrated an almost perfect correlation between the number of colonised wind-felled trees and the number of killed trees in a 4-year period following the storm disturbance. In the same study the removal of wind-felled trees resulted in a 50% reduction in number of trees killed per ha in the 4-years following the storm.
Article
An account is given of a recently devised method of prediction based on sample reuse techniques. It is most useful in low structure data paradigms that involve minimal assumptions. A series of applications demonstrating the technique is presented.
Article
The Sun is the main energy source of the life on the Earth. Thus, solar radiation energy data and models are important for many areas of research and applications. Many parameters influence the amount of solar energy at a particular standing point of the Earth's surface; therefore, many solar radiation models were produced in the last few years. Solar radiation energy depends mostly on incidence angle, which is defined by astronomical and surface parameters. Our solar radiation model is based on defining incidence angle by computing normal-to-the-surface tangent plane and direction of the Sun. If a part of the surface is in the shadow, it receives lesser energy than sunny areas. That is why shadow determination is an important part of the model. The sky is usually not completely clear, so meteorological parameters had to be integrated into the model. Meteorological model distinguishes among direct and diffuse Sun radiation. The model was tested and implemented for the whole Slovenia and it was also compared with previous studies. Case study surface data were calculated from the DEM with a 25 m resolution. The astronomical data, which were required for virtual Sun motion simulation around the Earth, were derived from the astronomical almanac. Meteorological data were acquired from observed mean values on 24 meteorological stations between 1961 and 1990. All calculations were made for hours and decades and finally, the annual quasiglobal radiation energy, which is the energy received by inclined plane from the Sun in one year, was calculated from the sum of all the energies of all the decades.
Article
The population of the spruce bark beetle Ips typographus (L.) in the forest of Rold Skov was monitored in the years following a 1981 gale. All attacked standing trees, areas with windthrown trees, catches in pheromone traps, timing of salvage harvests, and stands exposed to attack were registered and mapped in 1982 and 1983. Three different indices for attack density in areas around windthrown trees, infested trees and pheromone traps were calculated using GIS (ArcView). The attack densities in 1983 around areas with windthrown trees salvaged after 1 July 1982 were significantly higher than for areas salvaged earlier. Attack densities around windthrown trees salvaged between 15 May and 1 July, just after the main spring-flight period, were the lowest. The maximum distance from an old attack to a new was 650 m and there was an old attack within 500 m of all new attacks. Attack densities around pheromone traps were not correlated with the number of beetles caught in the traps. The majority of the beetles emerging from an epidemic attack dispersed over short distances (i.e. <500 m) before entering a new host. This local dispersal may best be countered by removing old breeding sites/windthrown trees in the period between spring-flight and the emergence of the new generation, i.e. by using the windthrown trees as bait trees. Pheromone traps are not suitable as a sole protective measure to prevent further infestation.
Article
In a spatially explicit climate change impact assessment the modified patch model PICUS v1.2 was applied to simulate the transient response of current forests in Austria under three climate change scenarios which were based on regionalized GCM-scenario data. The forest model was initialized with ground-true stand and soil data from more than 2800 sample plots of the Austrian Forest Inventory (AFI). A comparison of simulated equilibrium species composition under current climate and expert reconstructions of PNV at the sample plots of AFI showed that the model responded realistically to the spatial variability of soil and climate characteristics. In deriving potential climate change impacts the simulation under current climate was used as a reference. Impact criteria representing the period 2000–2050 and long-term criteria derived from simulated site-specific potential natural vegetation (PNV) were used in a multiple-criteria approach to calculate short-/mid-term as well as long-term climate change impact indices. The study showed that neither transient short-/mid-term nor long-term PNV-based indices alone are sufficient to indicate the possible consequences of climate change on existing forests. Based on the results of the study the combined use of such climate change impact indices is recommended. A major finding was that beyond a temperature increase of approximately +1 °C (no changes in precipitation) the proportion of inventory plots showing severe climate change impacts increased markedly. While at higher elevations under warmer climates the set of suitable tree species increased due to increased competitivity of broadleaved species, the study suggests that under the set of analysed climate change scenarios at low-elevation sites Picea abies would become unsuitable as a crop species. Limitations of the presented approach are discussed and conclusions regarding possible consequences for forest management are drawn.
Article
The outbreaks of Ips typographus (L.) in Central Europe after severe storms in the 1990s triggered extensive research. Molecular techniques were used to analyze the relations and origins of European Ips species. The biological characteristics of I. typographus such as the influence of temperature on life history parameters and flight behavior have been analyzed in detail. The spruce bark beetle was found to disperse well beyond 500 m. However, new attacks mostly occurred in the vicinity of old ones.Many studies refer to invertebrate natural enemies of I. typographus such as predatory beetles and flies as well as various parasitoids. While the species assemblages of antagonists have been extensively investigated their dynamics and impact on I. typographus populations are controversial.The susceptibility and defense mechanisms of host trees are crucial for a successful attack by bark beetles. Newly attacked trees respond with preformed resin, local wound reactions and eventually with systemic changes in their physiology. Risk assessments have been performed at both tree and stand level. Risk of attack seems to be mainly related to the exposition, age, and nutrient and water supply of the trees. The dynamics of outbreaks largely depends on insect abundance, tree susceptibility, weather conditions, and human measures. This renders predictions difficult. Various control techniques are reviewed and the need for more sophisticated risk assessment tools is stressed.
Article
Samples of Norway spruce (Picea abies [L.] Karst) were dendrochronologically investigated in order to detect infestations by Dendroctonus micans (Kug.), the great spruce bark beetle (Col. Scolytidae), a relatively recent introduction to France. Uninfested natural forests located in the north-eastern French Alps and heavily infested plantations in the Ardèche region (Massif Central) were compared. The penetration holes bored in trunks by the bark beetle induced visible marks on wood, such as extreme ring width reductions, locally missing rings and crescent-shaped resin patches between consecutive rings that make possible a post-infestation dating.
Conference Paper
In real-world concept learning problems, the representation of data often uses many features, only a few of which may be related to the target concept. In this situation, feature selection is important both to speed up learning and to improve concept quality. A new feature selection algorithm Relief uses a statistical method and avoids heuristic search. Relief requires linear time in the number of given features and the number of training instances regardless of the target concept to be learned. Although the algorithm does not necessarily find the smallest subset of features, the size tends to be small because only statistically relevant features are selected. This paper focuses on empirical test results in two artificial domains; the LED Display domain and the Parity domain with and without noise. Comparison with other feature selection algorithms shows Relief's advantages in terms of learning time and the accuracy of the learned concept, suggesting Relief's practicality.
Article
1- One expected effect of global climate change on insect populations is a shift in geographical distributions toward higher latitudes and higher elevations. Southern pine beetle Dendroctonus frontalis and mountain pine beetle Dendroctonus ponderosae undergo regional outbreaks that result in large-scale disturbances to pine forests in the south-eastern and western United States, respectively. 2- Our objective was to investigate potential range shifts under climate change of outbreak areas for both bark beetle species and the areas of occurrence of the forest types susceptible to them. 3- To project range changes, we used discriminant function models that incorporated climatic variables. Models to project bark beetle ranges employed changed forest distributions as well as changes in climatic variables. 4- Projected outbreak areas for southern pine beetle increased with higher temperatures and generally shifted northward, as did the distributions of the southern pine forests. 5- Projected outbreak areas for mountain pine beetle decreased with increasing temperature and shifted toward higher elevation. That trend was mirrored in the projected distributions of pine forests in the region of the western U.S. encompassed by the study. 6- Projected outbreak areas for the two bark beetle species and the area of occurrence of western pine forests increased with more precipitation and decreased with less precipitation, whereas the area of occurrence of southern pine forests decreased slightly with increasing precipitation. 7- Predicted shifts of outbreak ranges for both bark beetle species followed general expectations for the effects of global climate change and reflected the underlying long-term distributional shifts of their host forests.