Response of soil chemistry to forest dieback after bark beetle infestation

We evaluated changes in the chemistry of the uppermost soil horizons in an unmanaged spruce forest (National Park Bohemian Forest, Czech Republic) for 3 years after dieback caused by a bark beetle infestation, and compared these changes with a similar undisturbed forest area. The soils below the disturbed forest received 2–6 times more elements via litter fall compared to the unaffected plot. The subsequent decomposition of litter and reduced nutrient uptake by trees resulted in a steep increase in soil concentrations of soluble N (NH₄-N, organic-bound N) and P forms in the disturbed plot. The average concentrations of NH₄-N and soluble reactive P increased from 0.8 to 4.4 mmol kg^?1 and from 0.04 to 0.9 mmol kg^?1, respectively, in the uppermost soil horizon. Decomposition of litter at the disturbed plot elevated soil concentrations of Ca²⁺, Mg²⁺ and K⁺, which replaced Al³⁺ and H⁺ ions from the soil sorption complex. Consequently, soil concentrations of exchangeable base cations increased from 120 to 200 meq kg^?1, while exchangeable Al³⁺ and H⁺ decreased 66 and 50 %, respectively, and soil base saturation increased from 40 to 70 %. The Al³⁺ liberation did not elevate concentrations of ionic Al in the soil solution, because most of the liberated Al³⁺ was rapidly complexed by dissolved organic carbon (DOC) and transformed to DOC–Al complexes. The chemical parameters investigated at the unaffected plot remained stable during the study.     

The European spruce bark beetle <Emphasis Type="Italic">Ips typographus</Emphasis> in a national park: from pest to keystone species

The influence of natural disturbance on biodiversity is poorly known in the intensively cultivated landscape of Europe. As an example of insect disturbance we studied effects of gaps generated by outbreaks of the spruce bark beetle (Ips typographus) on biodiversity in the area of the National Park “Bavarian Forest” and compared them with openings (e.g. meadows) created by humans in these forests. Insects were sampled using flight interception traps across twelve ecotones between edges of closed forest, six bark beetle gaps and six meadows. The diversity and species density of true bugs and of bees/wasps increased significantly from the closed stand to the edge, and continued to increase inside the openings at interior and exterior edges. Species density in saproxylic beetles also increased significantly from closed forest to opening, but only across ecotones including bark beetle gaps. Similarly, the number of critically endangered saproxylic beetles increased significantly in bark beetle gaps. Using indicator species analysis a total of 60 species were identified as possessing a statistically significant value indicating preference for one of the habitat types along the ecotones: 29 of them preferred gaps, 24 preferred meadows, three were characteristic for edges of meadows, three for edges of bark beetle gaps, but only one was typical of closed forest. Most of our results support the thesis that I. typographus fulfils the majority of criteria for a keystone species, particularly that of maintenance of biodiversity in forests. Our results emphasize the value for the study and conservation of insect diversity of the policy of non-interference with natural processes pursued in some protected areas. As a recommendation to forest management for increasing insect diversity even in commercial forest, we suggest that logging in recent gaps in medium aged mixed montane stands should aim at retention of a part of the dead wood. Planting should be avoided, to lengthen the important phase of sunlit conditions.     

The aggregation pheromone system of a Dendroctonus bark beetle in Guatemala

Analysis of the volatile contents of hindguts from a Dendroctonus bark beetle in Guatemala indicated distinct differences from those of D. frontalis, which it resembles morphologically. The major compound in emergent males, most of which disappears during initial attack of host trees (Pinus maximinoi), was identified as 1-phenylethanol. During initial attack females produce frontalin and trans-verbenol, males produce myrtenol, and both sexes produce 1-heptanol and 2-heptanol. Synthetic frontalin attracted predominantly males to small traps, but the use of larger trapping surfaces increased the proportion of females caught. The heptanols, as well as 1-phenylethanol, apparently had some regulatory effect on the response to frontalin, but myrtenol and trans-verbenol were inactive. The results suggest that frontalin is the key compound responsible for the aggregation of this species, but the response-regulating mechanism differs from that of D. frontalis.     

Complex emergence patterns in a bark beetle predator

1 The emergence pattern of Thanasimus dubius (F.) (Coleoptera: Cleridae), a common predator of the southern pine beetle, Dendroctonus frontalis Zimmermann (Coleoptera: Scolytidae), was studied under field conditions across different seasons. A simple statistical model was then developed to characterize the emergence data, using the truncated geometric distribution. Data are also presented on the mortality of T. dubius eggs at various temperatures and humidities in an effort to explain certain aspects of emergence behaviour. 2 Emergence of T. dubius from a given tree usually occurred in several discrete episodes across a two‐year period, with most individuals emerging in spring or autumn. Almost no emergence occurred in July and August, which may be an adaptation to avoid high temperature mortality. Emergence patterns appeared similar across seasons, with the time of year serving mainly to shift the pattern through time. 3 Cycles in D. frontalis abundance may be the result of delayed density dependence generated by its natural enemy complex. The predator T. dubius is likely to be an important component of this delayed density dependence, because of its lengthy development time and apparent impact on D. frontalis.     

The pattern and range of movement of a checkered beetle predator relative to its bark beetle prey

Theoretical studies of predator‐prey population dynamics have increasingly centered on the role of space and the movement of organisms. Yet, empirical studies have been slow to follow suit. Herein, we quantified the long‐range movement of a checkered beetle, Thanasimus dubius, which is an important predator of a pernicious forest pest, the southern pine beetle, Dendroctonus frontalis. Adult checkered beetles were marked and released at five sites and subsequently recaptured at traps baited with pine and pine beetle semiochemicals and located at distances up to 2 km away from the release point. While the pattern of recaptures‐with‐distance at each site provided a modest fit to a simple random‐diffusion model, there was a consistent discrepancy between observed and expected recaptures: a higher than expected proportion of beetles were recaptured at the more distant traps. To account for this deviation, we developed a model of diffusion that allowed for simple heterogeneity in the population of marked beetles; i.e., a slow and fast moving form of the checkered beetle. This model provided a significantly better fit to the data and formed the basis for our estimates of intra‐forest movement. We estimated that on average, one half of the checkered beetles dispersed at least 1.25 km, one third dispersed>2 km, and 5% dispersed>5 km. The source of the heterogeneous dispersal rates were partially due to differences in beetle size: smaller beetles (for both males and females) were more likely to be recaptured away from the release site than larger beetles. The southern pine beetle (prey for the checkered beetle) exhibited no significant heterogeneity in dispersal ability and provided a very good fit to the simple diffusion model. The only difference in dispersal between these two species was that checkered beetles were undergoing greater long‐distance dispersal than the pine beetles (the radius containing 95% of the dispersing individuals was 5.1 km for the checkered beetle and 2.3 km for the pine beetle). Data on the movement of these two species is used to evaluate a general model of spatial pattern formation in a homogeneous environment, and the potential of the checkered beetle as a biological control agent for the southern pine beetle.     

The effect of larval aggregation behaviour on larval growth of the spruce bark beetle Dendroctonus micans

1. The great spruce bark beetle Dendroctonus micans is a primary pest of spruce in Europe. It is unusual among Eurasian scolytids in that apparently healthy trees are attacked by solitary adults, but larvae feed en masse , in response to a larval aggregation pheromone.
2. The effect of brood size on larval growth was determined in experiments on detached bark, logs and living trees. A positive relationship was found between brood size and larval growth in experiments started with either eggs or larvae up to fifth instar. The relationship appeared to be independent of the effects of both preformed and induced defences in bark.
3. No evidence was found to support the hypothesis that larvae feeding in groups spend a greater proportion of time feeding. Addition of resin to egg chambers in detached bark pieces resulted in high mortality of first-instar larvae. A possible role for larval aggregation in minimizing the effects of host defences is discussed.     

The role of lignin as a defence against the spruce bark beetle Dendroctonus micans: effect on larvae and adults

Summary The role of lignin as a physical defence against Dendroctonus micans was investigated in laboratory feeding experiments. The effect of lignin is dose-dependent, reducing larval survival, growth rate, and weight, as well as affecting gallery construction. Adults lay fewer eggs in lignified bark and also tend to construct abnormal galleries. The distribution of lignin in trees suggests a role in defence against bark beetles that feed in the thicker bark on the lower bole.     

The effect of a mealybug infestation on the activity of amino acid decarboxylases in orchid leaves

Changes in the activity of lysine decarboxylase (LDC), tyrosine decarboxylase (TyDC), and ornithine decarboxylase (ODC) within orchid (Phalaenopsis × hybridum ‘Innocence’) leaves, infested by two mealybug species: Pseudococcus longispinus (Targ. Tozz.) and Pseudococcus maritimus (Ehrh.) were quantified. The pattern of changes was dependent on the insect species and duration of infestation. P. longispinus feeding increased LDC and TyDC activity after one week during the total period of observations. This species inhibited ODC activity after one week but increased later. P. maritimus decreased LDC activity in orchid leaves at all studied terms. TyDC action also went up during the first week of the infestation and was reduced after two weeks, while ODC was decreased after one day and induced later. The mechanism for the participation of analysed amino acid decarboxylases in local and/or systemic steps of orchid responses to mealybug infestation is discussed.     

Chiral escape of bark beetles from predators responding to a bark beetle pheromone

Summary Two species of predatory beetles that locate their prey, Ips pini, by responding to its aggregation pheromone have different chiral preferences to ispdienol than does the herbivore. This suggests that chiral disparity may provide some escape for bark beetles from predation, and that geographic variation in herbivore communication systems may be partially due to predator — imposed selection pressures. These results also suggest ways in which the semiochemical and biological control of North America's most damaging group of forest insects can be improved.     

Carabid beetle diversity and distribution in Boston Harbor Islands national park area (Coleoptera, Carabidae)

As part of an All Taxa Biodiversity Inventory in Boston Harbor Islands national park area, an inventory of carabid beetles on 13 islands was conducted. Intensive sampling on ten of the islands, using an assortment of passive traps and limited hand collecting, resulted in the capture of 6,194 specimens, comprising 128 species. Among these species were seven new state records for Massachusetts (Acupalpus nanellus,Amara aulica,Amara bifrons, Apenes lucidulus, Bradycellus tantillus, Harpalus rubripes and Laemostenus terricola terricola-the last also a new country record; in passing we report also new state records for Harpalus rubripes from New York and Pennsylvania, Amara ovata from Pennsylvania, and the first mainland New York records for Asaphidion curtum). For most islands, there was a clear relationship between species richness and island area. Two islands, however, Calf and Grape, had far more species than their relatively small size would predict. Freshwater marshes on these islands, along with a suite of hygrophilous species, suggested that habitat diversity plays an important role in island species richness. Introduced species (18) comprised 14.0% of the total observed species richness, compared to 5.5% (17 out of 306 species) documented for Rhode Island. We surmise that the higher proportion of introduced species on the islands is, in part, due to a higher proportion of disturbed and open habitats as well as high rates of human traffic. We predict that more active sampling in specialized habitats would bring the total carabid fauna of the Boston Harbor Islands closer to that of Rhode Island or eastern Massachusetts in richness and composition; however, isolation, human disturbance and traffic, and limited habitat diversity all contribute to reducing the species pool on the islands relative to that on the mainland.     

The effect of undersowing cabbage with white clover on thrips infestation and flight activity

In 2001-2003, the levels of infestation of thrips in cabbage monocrops and cabbage/white clover intercrops were compared. The flight activity of thrips was monitored using blue sticky traps and white water traps to obtain a better understanding of population dynamics of thrips. Plant samples were taken to record the number of thrips on cabbage. Over the years of observations, the highest number of thrips was collected in blue sticky traps on cabbage undersown with white clover. In the period from 15th June to 5th July 2001, the number of thrips collected in blue sticky traps in the monocropped cultivation and intercrops with white clover was on similar low levels. Next, the number suddenly increased to 372 thrips/trap in monocropped cultivation and 509 thrips/trap in the intercropped cultivation. During the period of the highest peak of thrips activity, which was on 17th July, there were 650 thrips/trap and nearly the same number was noticed for both types of cultivations. After this period, until the end of vegetation, the greater number of thrips was noticed for the traps placed in the intercrops. Additionally, in 2001 the thrips were collected in white water traps. Using this type of traps, 480 total thrips/trap were collected in the monocropped cultivation and 819/thrips/trap in the intercrops during the whole vegetation season. The percentage participation of Thrips tabaci Lind. caught in white water traps was 24.4% in the monocropped cultivation and 15.4% in the intercrops. In 2002, during the period from the middle of June to the third decade of July, significantly higher number of thrips was collected in blue sticky traps placed in the cabbage with white clover. The number of thrips collected during the period of the mass flights, which means in the first decade of July was over twice as many thrips in the traps placed in the intercropped cultivation (1316 thrips/trap) as in the monocropped cultivation (589 thrips/trap). In 2003, during the whole vegetation period, the number of thrips collected in blue sticky traps placed on the plots where cabbage was cultivated with white clover was evidently higher. In this year two peaks of the thrips flight activity were recorded: the first on 16th July and the second on 5th August. On both occassions, the number of thrips collected in blue sticky traps placed in the intercropped cultivations was about twice as high as in the monoculture cultivation. In 2001-2003, the thrips feeding on cabbage in the monocropped and intercropped cultivations were observed mainly in July and once again in August. The number of thrips on cabbage was low, only in 2002 this number was higher. In 2001, the number of thrips on cabbage in both types of cultivations was on similar level. The highest number of thrips was observed during the peak of thrips flight activity, which was in the middle of July. In years 2002-2003, despite the higher number of thrips collected in blue sticky traps placed in the intercropped cultivations, the number of pests collected from the cabbage undersown with white clover was lower than in the monocropped cultivation. In 2002, the period of the most intensive occurrence of thrips on cabbage was overlapping with the period of mass flight activity of thrips. During this period, a little higher number of thrips was noticed on cabbage in the intercropped cultivation (3.4 thrips/plant) than in the monocropped cultivation (3.2 thrips/plant). In 2003, the highest number of thrips on cabbage in both types of cultivations was noticed before the first significant peak of thrips flight activity. Whereas in the first decade of August, when the same high number of thrips collected in blue sticky traps was again noticed, no increase in the number of thrips feeding on cabbage was observed in both type of cultivations. Over all years of observations, despite the higher number of thrips collected in blue sticky traps in the intercropped cultivation, this number was always lower on the cabbage undersown with white clover. The most dominant species in both cultivations was Thrips tabaci Lind. Its percentage participation in the collected material was 83.1% in the monocropped cultivation and 76.6% in the intercropped cultivation.     

The avifauna 23 years after logging in Kibale National park, Uganda

The bird fauna of logged and unlogged forest in Kibale National Park, western Uganda were studied and comparisons made. Species diversity and richness were higher in the logged areas. A single species, the Yellow-whiskered Greenbul Andropadus latirostris dominated in the logged compartment. However, the majority of individual birds found in the logged forest were generalist or forest-edge species. Over 84% of the forest interior specialist species that occurred in primary forest had recolonized or persisted in the logged forest; however, there were seven out of 48 understorey forest specialists that had not done so. Although there was moderate species overlap between the two habitats, the logged forest compartment had not fully recovered from logging after 23 years.     

Spatio-temporal impact of climate change on the activity and voltinism of the spruce bark beetle, Ips typographus

The spruce bark beetle Ips typographus is one of the major insect pests of mature Norway spruce forests. In this study, a model describing the temperature-dependent thresholds for swarming activity and temperature requirement for development from egg to adult was driven by transient regional climate scenario data for Sweden, covering the period of 1961–2100 for three future climate change scenarios (SRES A2, A1B and B2). During the 20th century, the weather supported the production of one bark beetle generation per year, except in the north-western mountainous parts of Sweden where the climate conditions were too harsh. A warmer climate may sustain a viable population also in the mountainous part; however, the distributional range of I. typographus may be restricted by the migration speed of Norway spruce. Modelling suggests that an earlier timing of spring swarming and fulfilled development of the first generation will significantly increase the frequency of summer swarming. Model calculations suggest that the spruce bark beetle will be able to initiate a second generation in South Sweden during 50% of the years around the mid century. By the end of the century, when temperatures during the bark beetle activity period are projected to have increased by 2.4–3.8 °C, a second generation will be initiated in South Sweden in 63–81% of the years. The corresponding figures are 16–33% for Mid Sweden, and 1–6% for North Sweden. During the next decades, one to two generations per year are predicted in response to temperature, and the northern distribution limit for the second generation will vary. Our study addresses questions applicable to sustainable forest management, suggesting that adequate countermeasures require monitoring of regional differences in timing of swarming and development of I. typographus , and planning of control operations during summer periods with large populations of bark beetles.     

Saccharide-mediated antagonistic effects of bark beetle fungal associates on larvae

Bark beetles are among the most destructive of pine forest pests and they form close symbiotic relationships with ophiostomatoid fungi. Although some fungi are considered to be mutualistic symbionts of bark beetles with respect to the supply of nutrients, detrimental effects of fungal symbionts on larval growth have also been frequently reported. The mechanisms of such antagonistic effects are hypothesized to be a decrease in nutritional resources caused by competition for saccharides by the fungi. Here, we provide experimental evidence that three beetle-associated fungi modify the nutritional content of an artificial phloem diet, leading to a detrimental effect on the growth of Dendroctonus valens larvae. When larvae were fed a diet of pine phloem in agar medium colonized with any of these fungi, feeding activity was not affected but weight significantly decreased. Additional analysis showed that fungi depleted the fructose and glucose concentrations in the phloem media. Furthermore, these detrimental effects were neutralized by supplementing the media with fructose or glucose, suggesting that fungi may affect larval growth by modifying diet saccharide contents. These data indicate that fungus-induced nutritional changes in bark beetle diet can affect larval growth, and that the mechanism involves fungus-induced saccharide depletion from the larval diet.     

Socio-economics and wildlife conservation of a peri-urban national park in central Kenya

The support, perceptions, values and aspiration of the local people, especially those who neighbour protected areas is increasingly recognised as critical for long-term biodiversity conservation in many countries. As such, conservation agencies are keen to understand the linkages and interactions between wildlife conservation and socio-economics of local communities. We assessed the socio-economic, demographic factors and livelihood status of the households of communities bordering Oldoinyo Sapuk National Park in central Kenya, and evaluated their willingness to support wildlife conservation. We randomly interviewed households that neighbour the Park on a wide range of socio-economic, livelihood and demographic factors. The majority of respondents were small-scale farmers practicing crop farming and livestock keeping. Most respondents considered the Park to have great potential for the future economic development of the area, especially through ecotourism as a potential avenue to support local livelihoods.     

Seasonal influence on reproduction in chimpanzees of gombe national park

Although wild chimpanzees are not seasonal breeders, there are seasonal effects on several aspects of chimpanzee reproduction. I examined the seasonal incidence of anogenital swelling in cyclic, pregnant, and acyclic female chimpanzees in Gombe National Park, May 1975–April 1992, and surveyed important reproductive events to determine whether there is a seasonal effect. I analyzed data by season (wet vs. dry) and seasonal quarter;early dry season = May–July;late dry = August–October;early wet = November–January;late wet = February–April. When data for the 17 years are combined, the percentage of females in each reproductive state remains consistent throughout the year. In a given month, 30–35% of subjects were in the cyclic category, 11–15% were pregnant, and 54–61% were acyclic. Cyclic females showed full swelling more often during the late dry season. Pregnant females exhibited anogenital swelling more often during the late dry and early wet seasons. Acyclic females also exhibited a seasonal effect with more anogenital swelling during the late dry season. There is no seasonal difference in frequency of live births (dry, 20;wet, 23). However, the timing of conception showed a seasonal effect (dry, 32;wet, 16). Consistent with earlier reports, the onset of postpartum cycles is highly seasonal;30 occurred during dry season, 9 during wet season. The occurrence of first full swellings for young females is also concentrated in the late dry season. It appears that the dry season is a time of great change for Gombe chimpanzee reproductive physiology. Previous studies indicated that seasonal changes in food availability play a role in increasing group size during the dry season and social contact between females can enhance cyclicity. Accordingly, I suggest that seasonal changes in diet may play a role, either directly (food content) or indirectly (social contact), to alter reproductive physiology.