A non-linear model to predict crown recession of Norway spruce (<Emphasis Type="Italic">Picea abies</Emphasis> [L.] Karst.) in Austria

In this study, a non-linear model was developed that predicts the five-year change of height to crown base (HCB) of Norway spruce (Picea abies [L.] Karst.). Data were available from the Austrian National Forest Inventory and comprised 2,419 trees from 1,637 permanent sample plots measured during 1981 and 2002. The dynamic model explained 36% of the variation in the observed change of HCB. It is well behaved and meets biological expectations. Based on five independent data sets, the predictive ability of the new dynamic model was compared to an already existing static crown ratio model. For this comparison, the models were applied as follows: the new ∆ HCB model was used to predict the change in HCB directly. For the semi-dynamic method, the static model was applied at the end and at the start of the growth period to obtain two estimates of HCB. The difference of these two estimates was then added to the initial HCB. For the static method, the model was only applied at the end of the prediction period to obtain the new estimate of HCB. Except for one plot, the new ∆ HCB model yielded the smallest BIAS and the highest precision, followed by the semi-dynamic and the static method. Because the independent data sets cover a broad range of age classes and thinning regimes, the validation results also indicate that the new ∆ HCB is robust and the effect of stand management is adequately represented.     

Absence of geographical structure of morphological variation in <Emphasis Type="Italic">Juniperus oxycedrus</Emphasis> L. subsp. <Emphasis Type="Italic">oxycedrus</Emphasis> in the Balkan Peninsula

We examined leaf and mature seed cone variation of Juniperus oxycedrus L. subsp. oxycedrus in 12 natural populations across the species range in the Balkan Peninsula. We measured 10 morphological traits from a minimum of 100 leaves in each of 190 individuals, and two morphological traits from 30–50 seed cones in each of 94 females. High phenotypic variation was found, but no geographical structure or cline across populations was detected for any of the studied traits. Mean values of comparable leaf and cone morphological traits did not differ considerably from values reported elsewhere. Gender dimorphism in leaf morphology was detected, but it was not distributed uniformly throughout the studied area. An ANOVA model with both nested and crossed effects revealed that the largest proportion of the total variation was, as expected, contained within populations, partly as among-tree variation (18–47%, depending on the trait) and partly as within-tree variation (33–77%), which was remarkably high. Gender dimorphism explained only 0–3% of the total variation. Differences among populations (2–23%) were significant for all studied traits except one; however, PCA showed no clear geographical differentiation of the studied populations. This lack of phylogeographical structure may be the consequence of repeatedly occurring colonisation-retreat scenarios and suggests the existence of several small refugial populations scattered over a large part of the Balkan Peninsula in the Pleistocene. Further research including palaeobotanical and molecular genetic studies will be needed to better understand the forces that shaped current variation patterns of J. oxycedrus L. subsp. oxycedrus in the Balkan Peninsula.     

Stem modeling and simulation of conversion of cork oak stems for quality wood products

Recent research is underway to study cork oak (Quercus suber L.) wood potential for production of wood components. A total of 35 stems of young and mature cork oaks were sampled, live sawn into flitches, scanned using VTT’s WoodCIM^®, and the measured data computed by VTT’s PuuPilot software, allowing stem 3D reconstruction. Sawing simulations were run for 0.5 m and 1 m logs and the whole stem. Sawn products were (1) planks, (2) parquet, (3) lamparquet, and (4) external component of multilayer planks. Cork oak stems showed a moderate to small taper (mean 24 mm/m). Curviness varied between straight to significantly crooked stems (mean value 40 mm) Batch yields for the tested products ranged 25–43% and 37–50% for 0.5 m logs of young and mature trees, respectively; for 1 m logs, batch yields ranged 19–41% and 25–54%. When using the whole stem, batch yields were lower, ranging 11–38% and 15–50%. Higher yields were obtained for all log lengths and samples for production of lamparquet, parquet, and multilayer component.     

Post-fire attractiveness of maritime pines (<Emphasis Type="Italic">Pinus pinaster</Emphasis> Ait.) to xylophagous insects

The spectrum and dynamics of xylophagous insects infesting Pinus pinaster after a fire event were studied from November 2007 to December 2008 at Sierra de Outes (Galicia, NW Spain). Insects were collected within and outside the fire area. Relationships among species status, species abundance, tree parameters and tree injury were assessed. Mortality of injured trees was also recorded. Insect colonization built up consistently during the first year after the fire, although the pests did not colonize unburned trees in nearby areas. Thirteen insect species from six xylophagous families were collected. Tomicus spp., Buprestis novenmaculata, Anobium punctatum and Pissodes castaneus were the first species detected. Tomicus spp. (29%) and Ips sexdentatus (23%) were the dominant taxa. Bole char height and soil burn severity were positively correlated with insect presence. Trees with short stem diameter and thinner bark were also preferred. B. novenmaculata presence was positively correlated with crown scorch. Loss of cambium hydration was negatively related to the occurrence of pests, likely because sapwood desiccation and loss of nutrient impede brood development. About 33.3% of the fire-scorched pines died. The results recommend the removal of injured and dying pines after fire, to avoid the rise of pest population threatening recovering trees in the burned areas.     

Comparison of biological parameters between the invasive B biotype and a new defined Cv biotype of <Emphasis Type="Italic">Bemisia tabaci</Emphasis> (Hemiptera: Aleyradidae) in China

The sweetpotato whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is a widely distributed and destructive agricultural pest on various host plants. The biology of two biotypes of B. tabaci: the invasive B and a new defined Cv biotype, on a range of host plants (hibiscus, laurel, poinsettia, collard, cucumber and tomato) were studied in the laboratory. Results revealed that the developmental periods of the B biotype immatures were not significantly different on the tested host plants except those between laurel and collard. The Cv biotype immatures developed significantly slower on cucumber and tomato than on the other plants. B. tabaci B biotype had the highest survivorship on collard (68.55%), and the lowest on laurel (33.24%), while the Cv biotype had the highest and lowest survivorships on laurel (61.63%) and tomato (36.74%). Host plants did not significantly affect the pre-ovipostion period regardless of biotype. The longest averaged longevity and highest fecundity of B biotype were both recorded on collard: 25.15 days and 143.0 eggs. The highest fecundity of Cv biotype was 196.49 eggs on laurel and its longest longevity was on hibiscus (19.62 days). The intrinsic rate of natural increase (r _m) of B biotype on the three vegetables were all higher than those on the three ornamentals whereas the r _m of Cv biotype on the three ornamentals were all higher that those on the three vegetables. Our research indicates that B. tabaci B and Cv biotypes have different host plant suitabilities. The three tested vegetables were more suitable for B biotype while the three tested ornamental plants were more suitable for Cv biotype. The potential mechanism for the different suitability of B and Cv biotypes on various host plants is also discussed.     

Performance of four <Emphasis Type="Italic">Trichogramma</Emphasis> species (Hymenoptera: Trichogrammatidae) as biocontrol agents of <Emphasis Type="Italic">Heliothis virescens</Emphasis> (Lepidoptera: Noctuidae) under various temperature regimes

Trichogramma spp. are major parasitoids of lepidopteran pest eggs, but there is large variation in efficacy toward a given pest among the numerous described Trichogramma species. It is important to select the Trichogramma species that most effectively parasitize and develop in target pest eggs for biological control. In this context, Trichogramma pretiosum, T. exiguum, T. atopovirilia and T. acacioi were studied in Heliothis virescens eggs under different thermal conditions. The parasitoids were reared at constant temperatures of 20, 25 and 30°C and tested at these respective temperatures, while parasitoids reared at 25°C were also tested at 20 and 30°C, for a total of 20 species–temperature combinations. About 30 H. virescens eggs were offered to the parasitoids for 24 h. Among the four species, parasitism rate by T. atopovirilia was highest at all temperature conditions, whereas T. acacioi had the lowest rates of parasitism at 25°C and 25/30°C. Parasitism ranged from 13.8 to 43.8% among all species–temperature combinations. Viability (emerged parasitoids) ranged from 80.8 to 98.4%, and was deemed satisfactory. The emergence rates of T. exiguum and T. acacioi were affected by temperature. Temperature also affected the sex ratio of T. exiguum at 25/30°C, whereas T. pretiosum and T. acacioi produced females predominantly independent of temperature. Overall, the parasitoid T. atopovirilia was the most efficient in parasitizing H. virescens eggs, though the levels of parasitism obtained might not ensure its successful use in biological control programs. The temperature-related differences in biological traits observed in the four Trichogramma species tested hint at the importance of making careful choices regarding climatic conditions where the parasitoid is going to be used when selecting a species for biological control programs.     

Efficacy of spinosad and methoprene,applied alone or in combination,against six stored-product insect species

Efficacy of the insecticides spinosad and methoprene, applied alone or in combination to wheat, was evaluated against six stored-product insect species, Rhyzopertha dominica, Sitophilus oryzae, S. granarius, Cryptolestes ferrugineus, Oryzaephilus surinamensis, and Liposcelis bostrychophila. The concentrations of the insecticides were 0.1 and 0.5 ppm for spinosad and 1 and 5 ppm for methoprene. Parental mortality of R. dominica was 100% on wheat treated with either rate of spinosad, with no progeny production in any combination treatment. Parental mortality of S. oryzae did not exceed 62%, and progeny production was not reduced by any insecticide treatment. All S. granarius adults exposed on wheat treated with spinosad alone at 0.5 ppm were killed, but parental mortality was reduced when methoprene was added. Progeny production was reduced in treatments containing spinosad. Mortality of adult C. ferrugineus was 97% or greater in treatments containing spinosad, but adult mortality of O. surinamensis and L. bostrychophila was not reduced by insecticide treatments. The specific combinations of spinosad and methoprene evaluated in our study would have no benefit over spinosad used alone for control of any of the six species tested.     

Relating genetic variation of ecologically important tree traits to associated organisms in full-sib aspen families

Knowledge on phenological, morphometric, and phytochemical variation of local progenies of European aspen (Populus tremula, L.) is limited. The goal of this study was to characterize variation in growth and ecologically important leaf properties in aspen full-sib families in relation to interacting organisms (mycorrhiza, endophytes, and insects) and to determine whether these interactions were affected by soil application of a systemic fungicide. In local progenies, within-family variation of neutral molecular genetic markers (nuclear microsatellites) was higher than between families. Significant variation in growth, production of phenolic defensive compounds and other phytochemical leaf traits was found between families. Phenolic compounds showed clear negative correlation with generalist herbivores, but did not result in negative trade-off with biomass production. Differences in mycorrhizal colonization were not found among full-sib families and application of a systemic fungicide suppressed neither mycorrhizal colonization nor infestation with insects. However, a strong suppression of endophytes occurred, whose long-term consequences may require attention when fungicides are used in agroforestry plantations.     

Larval performances and life cycle completion of the Siberian moth, <Emphasis Type="Italic">Dendrolimus sibiricus</Emphasis> (Lepidoptera: Lasiocampidae), on potential host plants in Europe: a laboratory study on potted trees

The Siberian moth, Dendrolimus sibiricus, Tschtv. is the most harmful defoliator of coniferous forests in North Asia. The pest has already spread over the Urals and continues moving westwards. Recently, it has been recommended for quarantine in member countries by European and Mediterranean Plant Protection Organization (EPPO). The performances of the pest on coniferous species planted in Europe were assessed on a range of potted trees corresponding to the spectrum of economically important conifers in the EU: European larch Larix decidua, Norway spruce Picea abies, Scots pine Pinus sylvestris, European black pine Pinus nigra, and the North American species: Douglas fir Pseudotsuga menziesii and grand fir Abies grandis. Larvae showed a potential to survive and complete the development on all these host tree species. Favorable hosts were grand fir, European larch, and Douglas fir that allowed higher survival, better larval development, and as a result, yielded heavier pupae and adult moths with higher longevity. Black pine was a poor host but, however, could still support larval and pupal development. Norway spruce and Scots pine had an intermediate behavior. If accidentally introduced to Europe, the Siberian moth may become especially damaging in forest stands predominated by European larch and by the North American firs. Norway spruce and especially the two-needle pines will be less prone to intensive defoliation by this species. The fact that the pest may damage the range of economically important coniferous species should be taken into account in the pest risk assessment for Europe and also for North America where the Siberian moth occurrence is considered likely.     

A landscape and policy perspective on forest conversion: Long-tailed tit (<Emphasis Type="Italic">Aegithalos caudatus</Emphasis>) and the allocation of deciduous forests in southern Sweden

As resources allocated specifically for conservation are limited, there is a need to ensure conservation policy initiatives lead to effective conservation outcomes. In this study, we investigated the potential conservation benefits from alternative spatial allocations of old deciduous stands to a landscape dominated by coniferous production forests owned primarily by non-industrial private forest owners. As a target species, we used the long-tailed tit (Aegithalos caudatus), a species associated with deciduous forests and known to be sensitive to isolation. We used a previously published model based on empirical data on the occurrence of this species, to assess the probability of occurrence of the bird in a 4,000 km² area in southern Sweden for which we possess detailed spatial GIS data (kNN data) of tree species composition and age. We assessed alternative scenarios where old deciduous forest was allocated with or without respect to distance from existing old deciduous forests. Due to the long-tailed tit’s habitat requirement increasing the amount of old deciduous forests close to existing habitats was the most effective strategy. However, the potential advantages of this strategy may in fact be overturned in favor of the other scenarios if ownership structures and probable uptake rates of policy initiatives are also considered. If a policy initiative is targeted toward owners with properties in close proximity to existing suitable habitat, when compared to if all forest owners are targeted, a higher proportion of owners is needed to participate in order to achieve the same degree of habitat creation for the species. Here, we discuss the potential benefits for effective conservation policy formulation from integrating spatially explicit datasets and detailed ecological knowledge with land-ownership structures and policy uptake scenarios.