Leif Martin Schroeder

Attacks by Ips typographus and Pityogenes chalcographus on windthrown spruces (Picea abies) during the two years following a storm felling.

Attacks by Ips typographus and Pityogenes chalcographus during the first 2 yrs after a storm were studied on 1848 windthrown spruces (Picea abies) in southern Sweden. In the first and second summer, 29% and 24%, respectively, of the spruces were attacked by I. typographus, while 21% and 44%, respectively, were attacked by P. chalcographus. High stumps were attacked less frequently than tops, broken trees and windfelled trees with root contact. In both years, trunks in gaps were preferred over those in stands. The proportion of windthrown trees attacked by I. typographus increased with stem diameter, whereas the opposite was true for P. chalcographus. Positive interspecific associations between the species were found on the lower, middle and upper third parts of the trees in the first summer and on the lower part in the second summer. The results are discussed with regard to forest protection and nature conservation.

Attacks by bark- and wood-boring Coleoptera on mechanically created high stumps of Norway spruce in the two years following cutting

Abstract Attacks of bark- and wood-boring beetles on mechanically created high stumps of Norway spruce, Picea abies L. (Karst.), were studied in the provinces of Dalarna (Grangarde area) and Uppland (Fageron) in central Sweden. The experiment included a total of 362 stumps in the Grangarde area as well as 48 stumps and 18 logs at Fageron. Most inspections were conducted in the first and second autumns following the cuttings made to create the stumps. All stumps were attacked by at least one species during the two-year period, and for almost all of them (95%) the initial attacks occurred in the first summer. The most frequently encountered species on the stumps were the scolytids Ips typographus (L.), Pityogenes chalcographus (L.), Hylurgops palliatus (Gyll.), Orthotomicus spp., Trypodendron lineatum (Oliv.), Dryocoetes sp. and Polygraphus poligraphus (L.), and the cerambycids Tetropium spp. and Monochamus sutor (L.). Both the time of cutting and stump diameter influenced beetle colonisation. I. typographus was not found in autumn-cut stumps, while Orthotomicus spp. was found more frequently in autumn-cut stumps than in spring-cut stumps. There was a positive relationship between I. typographus occupancy and stump diameter, while negative relationships were found between stump diameter and H. palliatus and T. lineatum occupancy. Most stumps (ca. 80%) were attacked by more than one bark- and wood-boring species in the first summer. The proportion of stumps attacked was significantly higher than the proportion of logs attacked for P. poligraphus, T. lineatum and Tetropium spp., whereas the opposite was true for I. typographus. The percentage of bark area utilised by I. typographus was significantly higher in logs than in stumps.

Attack rates of scolytids and composition of volatile wood constituents in healthy and mechanically weakened pine trees

The composition of volatile wood constituents in healthy (untreated) and injured (top‐cut or girdled) Scots pine trees, Pinus sylvestris L., was studied during three years using gas chromatography. The data were evaluated using PCA (principal components analysis) and PLS‐DA (projections to latent structures‐discriminant analysis), two methods for multivariate data analysis. Data from headspace analysis from the first and the third year revealed a significant difference in the composition of volatile wood constituents between untreated and top‐cut trees while GC analysis of extracts only revealed a significant difference for the first year. The higher proportions of ethanol and acetaldehyde in top‐cut trees were important in differentiating these trees from healthy ones. Differences in the monoterpene composition also seemed to be important in this respect. Untreated trees remained unattacked by the scolytid species. Hylurgops palliants (Gyll.) and Trypodendron lineatum (Oliv.) (Scolytidae) only attacked t...

Attacks of bark- and wood-boring Coleoptera on snow-broken conifers over a two-year period.

The attacks of bark‐ and wood‐boring Coleoptera on broken conifer stems after severe snow‐breakage in early 1988 were studied in autumn 1988 and 1989. The study included twelve stands in the county of Varmland in central Sweden differing in age and edaphic conditions. The tops on the ground as well as the remaining rooted stem stumps of 94 Picea abies and 61 Pinus sylvestris were inspected. The presence of living branches on the stumps strongly influenced the incidence of insect attack. All stumps without branches were attacked during the two‐year period, whereas only a few spruce stumps with more than ten branches and no pine stumps with more than five branches were attacked. On spruce stumps, the most frequently encountered Coleoptera were all scolytids, i.e. the species Pityogenes chalcographus, Hylurgops palliatus, and the genera Polygraphus, Dryocoetes, and Trypodendron. On pine stumps, Tomicus piniperda was the most common species. Most of the spruce tops and virtually all pine tops were attacked du...

Conservation goals and the relative importance of costs and benefits in reserve selection.

Including both economic costs and biological benefits of sites in systematic reserve selection greatly increases cost-efficiency. Nevertheless, limited funding generally forces conservation planners to choose which data to focus the most resources on; therefore, the relative importance of different types of data must be carefully assessed. We investigated the relative importance of including information about costs and benefits for 3 different commonly used conservation goals: 2 in which biological benefits were measured per site (species number and conservation value scores) and 1 in which benefits were measured on the basis of site complementarity (total species number in the reserve network). For each goal, we used site-selection models with data on benefits only, costs only, and benefits and costs together, and we compared the efficiency of each model. Costs were more important to include than benefits for the goals in which benefits were measured per site. By contrast, for the complementarity-based goal, benefits were more important to include. To understand this pattern, we compared the variability in benefits and in costs for each goal. By comparing the best and the worst possible selection of sites with regard to costs alone and benefits alone for each conservation goal, we introduced a simple and consistent variability measure that is applicable to all kinds of reserve-selection situations. In our study, benefit variability depended strongly on how the conservation goal was formulated and was largest for the complementarity-based conservation goal. We argue that from a cost-efficiency point of view, most resources should be spent on collecting the most variable type of data for the conservation goal at hand.

Colonization of storm gaps by the spruce bark beetle: influence of gap and landscape characteristics

1 After storm disturbances, there is a risk for degradation of the quality of fallen trees, and for subsequent tree mortality caused by the spruce bark beetle Ips typographus (L.) (Coleoptera: Curculionidae). Models assessing the risk for bark beetle colonization of different kinds of storm gaps would be a valuable tool for management decisions. 2 The present study aimed to determine which gap and landscape characteristics are correlated with the probability of colonization of wind‐felled Norway spruce trees by I. typographus. 3 The study included 36 storm gaps, varying in size from three to 1168 wind‐felled spruces, created by the storm Gudrun in southern Sweden in January 2005. 4 In the first summer, on average, 5% of the wind‐felled spruces were colonized by I. typographus. The percentage of colonized wind‐felled trees per gap was negatively correlated with the total area of storm gaps within 2000 m in the surrounding forest landscape. 5 In the second summer, the proportion of colonized trees increased to 50%. Both gap (mean diameter of wind‐felled trees and basal area of living spruce trees) and landscape variables (amount of spruce forest) were significantly correlated with colonization percentage and explained almost 50% of the variation between gaps. 6 There was no relationship between gap area and colonization percentage. This implies that landscapes with many large storm gaps, where logging resources will be most effectively used, should be salvaged first.

Escape in space from enemies: a comparison between stands with and without enhanced densities of the spruce bark beetle

1 Populations of the spruce bark beetle, Ips typographus (L.), are known to grow rapidly in storm‐disturbed stands as a result of relaxation from intraspecific competition. In the present study, it was tested whether a second mechanism, escape in space from natural enemies, also contributes to the rapid population increase.

Differences in responses to α-pinene and ethanol, and flight periods between the bark beetle predators Thanasimus femoralis and T. formicarius (Col.: Cleridae)

Abstract The responses of the bark beetle predators Thanasimus femoralis (Zett.) and Thanasimus formicarius (L.) (Col.: Cleridae) to a combination of α-pinene and ethanol, and Pheroprax ® , the aggregation pheromone of Ips typographus (Col.: Scolytidae), were estimated using baited and unbaited flight barrier traps in central Sweden in 1996 and 1998. In addition, the flight periods of the two Thanasimus species were analysed on the basis of trap catches. Egg development and egg loads of T. formicarius were estimated by dissecting females caught on different dates, and counting the number of medium sized and large eggs in the ovaries. T. femoralis was strongly attracted to Pheroprax ® , but almost no individuals were caught in the traps baited with α-pinene and ethanol. In contrast, T. formicarius was strongly attracted to both kinds of baits. The flight periods of the two Thanasimus species were markedly different. T. formicarius initiated flight in early spring, at about the same time as the first bark beetle species, Tomicus piniperda and Hylurgops palliatus , began to fly. The flight period of T. femoralis started later in the spring, at about the same time as that of I. typographus . Medium sized and large eggs were not present in the ovaries of T. formicarius in the beginning of the flight period. Thereafter, during the major part of the flight period, most females carried medium sized eggs while large eggs occurred mainly in the first half of the flight period.

Population levels and flight phenology of bark beetle predators in stands with and without previous infestations of the bark beetle Tomicus piniperda

Abstract Relative population levels and flight periods of Tomicus piniperda (L.) (Col.: Scolytidae) and two of its main predators, Thanasimus formicarius (L.) (Col.: Cleridae) and Rhizophagus depressus (F.) (Col.: Monotomidae) were monitored in 1995 in eight Scots pine stands in central Sweden using flight barrier traps (five per stand) baited with α-pinene and ethanol. In four of the stands (A-stands) T. piniperda and associated species had reproduced the previous year in stumps and slash remaining after thinnings conducted in the winter of 1993/1994. In the remaining four stands (B-stands) no bark beetle breeding material had been available during the five preceding years. In addition, the flight periods of the species were monitored in one stand in 1996. In 1995 the catches of T. piniperda and R. depressus were four to five times higher in the A-stands than in the B-stands, whereas there was no difference in the catch of T. formicarius between the two kinds of stands. The T. formicarius/T. piniperda ratio was ca. 50 times higher in the B-stands compared with the A-stands during the period of clerid predation on colonising bark beetle adults and six times higher during the period of clerid oviposition. The R. depressus/T. piniperda ratio was only slightly higher in the A-strands than in the B-stands as a result of the spatial distribution of T. piniperda. Three additional species of bark beetle predators were caught: Glischrochilus quadripunctatus (L.), Pityophagus ferrugineus (F.) (Col.: Nitidulidae) and Rhizophagus ferrugineus (Payk.) (Col.: Monotomidae). Based on their seasonal abundance the bark beetle predators can be divided into three temporal groups: the first species to occur in the spring is G. quadripunctatus, the second group consists of R. depressus and T. formicarius, and the last species to initiate flight are R. ferrugineus and P. ferrugineus.

Transmission of Bursaphelenchus mucronatus (Nematoda) to branches and bolts of Pinus sylvestris and Picea abies by the cerambycid beetle Monochamus sutor

One hundred eighty‐two newly emerged M. sutor beetles, originating from central and northern Sweden, were allowed to feed on branch sections of Scots pine, Pinus sylvestris L., and Norway spruce, Picea abies (L.) Karst., for two to six weeks. Twenty‐two of these beetles transmitted the nematode Bursaphelenchus mucronatus Mamiya and Enda 1979, to the branches they were feeding on. After two weeks of feeding, 63 M. sutor male‐female pairs were allowed access to bolts of Scots pine and Norway spruce, suitable for oviposition, for three weeks. Seven of these pairs transmitted Bursaphelenchus mucronatus to the bolts of both tree species.