Jyrki Pusenius

Choice of voles among genotypes of birch seedlings: its relationship with seedling quality and preference of insects

Selective feeding by herbivores on establishing seedlings has been suggested to affect genotype frequencies in several plant populations. The existence of genotypes susceptible to herbivores calls for an explanation in such populations. In the present study we assessed the choice of multiple herbivores, field voles (Microtus agrestis) and insects, among genotypes of silver birch (Betula pendula) representing variation occurring in a naturally regenerated stand. We examined how food choice of voles and insects is related to each other, competitive ability among the seedling genotypes and variation in soil fertility. We set up a field experiment and randomly assigned seedling populations, composed of mixed genotypes, to fully crossed insect exposure and fertilization treatments. After the first growing season we exposed a half of the seedling populations to vole herbivory. Voles selected clearly among the genotypes: they preferred the fastest growing seedlings as well as those with a low density of resin droplets on their stems. The preference of voles and insects among the genotypes was tightly correlated. We conclude that the effects of herbivory compensate those of intraspecific competition in this system and thus favor coexistence of genotypes differing in their susceptibility to herbivores.

Genotypic variation in growth and resistance to insect herbivory in silver birch (Betula pendula) seedlings

If herbivory is unevenly distributed among different types of plants, or if individual plants differ in their response to herbivory, herbivores may affect seedling growth and survival, and consequently plant population structure. In this study we examined variation in resistance to insect herbivory and in growth responses to feeding among 20 silver birch (Betula pendula Roth) genotypes representing variation within a natural population. Birch seedlings were grown in dense stands in random arrangement so that seedlings of different genotypes competed with each other. On insect exposure plots natural colonization of insects was allowed, and insect removal plots were sprayed with insecticide. Resistance to insect herbivory was measured as the inverse of leaf damage, and growth responses of seedlings to feeding were determined as the change in seedling height relative to the amount of damage. Resistance varied significantly among genotypes, but growth responses to feeding did not. In fertilized seedlings, resistance correlated negatively with height, indicating a trade-off between resistance and growth. The absence of such a correlation in non-fertilized seedlings is a sign of environmental effects on the cost of resistance. Growth responses to feeding did not correlate with either resistance or growth. Nevertheless, different effects of the actual damage on height increase changed the positions of the genotypes in the size hierarchy of the experimental populations. Thus, even moderate levels of insect herbivory can change the outcome of competitive interactions between birch genotypes.

Combination treatment of elevated UVB radiation, CO2 and temperature has little effect on silver birch (Betula pendula) growth and phytochemistry.

Elevations of carbon dioxide, temperature and ultraviolet-B (UBV) radiation in the growth environment may have a high impact on the accumulation of carbon in plants, and the different factors may work in opposite directions or induce additive effects. To detect the changes in the growth and phytochemistry of silver birch (Betula pendula) seedlings, six genotypes were exposed to combinations of ambient or elevated levels of CO2 , temperature and UVB radiation in top-closed chambers for 7 weeks. The genotypes were relatively similar in their responses, and no significant interactive effects of three-level climate factors on the measured parameters were observed. Elevated UVB had no effect on growth, nor did it alter plant responses to CO2 and/or temperature in combined treatments. Growth in all plant parts increased under elevated CO2 , and height and stem biomass increased under elevated temperature. Increased carbon distribution to biomass did not reduce its allocation to phytochemicals: condensed tannins, most flavonols and phenolic acids accumulated under elevated CO2 and elevated UVB, but this effect disappeared under elevated temperature. Leaf nitrogen content decreased under elevated CO2 . We conclude that, as a result of high genetic variability in phytochemicals, B. pendula seedlings have potential to adapt to the tested environmental changes. The induction in protective flavonoids under UVB radiation together with the positive impact of elevated CO2 and temperature mitigates possible UVB stress effects, and thus atmospheric CO2 concentration and temperature are the climate change factors that will dictate the establishment and success of birch at higher altitudes in the future.

Assessing and modeling moose (Alces alces) habitats with airborne laser scanning data

Abstract In the analysis of forest resources, the use of ALS (airborne laser scanning) enables detailed three dimensional (3D) descriptions of forests and their vegetation. Simultaneously, ecologists have recognized that 3D information on vegetation is highly important in analyzing the habitat suitability of a given site. Recently, animals’ habitat preferences have been analyzed, for example, with GPS-collared animals. This has resulted in detailed knowledge about the animals’ movements both spatially and temporally. This study combines 3D information on vegetation obtained from ALS data with information about animal locations from GPS data. The aim was to map and analyze the habitat preferences of moose. The study area was located on the west coast of Finland. The data consisted of 18 GPS-collared moose (monitored from 2009 to 2010) and ALS data collected in 2010. We investigated how habitat structure changes as a function of distance to observed moose locations and how observed moose locations differ from randomly selected locations in terms of 3D structure. We also created a model-based habitat suitability map and tested it against moose occurrences. The results suggested that there are clear differences between the areas occupied and not occupied by moose and that these differences can be detected from ALS data. More importantly, ALS proved its potential in linking 3D descriptions of vegetation directly to observed moose locations without any proxy variables. These observations strongly support future studies.

Dark‐leaved willow (Salix myrsinifolia) is resistant to three‐factor (elevated CO2, temperature and UV‐B‐radiation) climate change

Elevated carbon dioxide (CO2 ), temperature (T) and ultraviolet-B (UV-B) radiation may affect plant growth and secondary chemistry in different directions, but the effect of the combination of the three factors has seldom been tested. Here, we grew four dark-leaved willow (Salix myrsinifolia) clones under combinations of ambient or elevated CO2, T and UV-B radiation in top-closed chambers for 7 wk. Elevated UV-B had no effects on growth or phenolic compounds, and there were no significant interactions between UV-B, CO2 and T. CO2 alone increased most growth parameters, but the magnitude of the effect varied among the clones. Total phenolics increased at elevated CO2 , whereas they decreased at elevated T. The responses varied between the clones. The results imply that dark-leaved willow are fairly resistant to the applied three-factor climate change, probably because of high constitutive defense. However, the interactions between clone and climate change factors implies that some clones are more susceptible than the species as a whole.

Effects of the availability of herbaceous food on vole attacks on birch seedlings

Abstract According to the optimal diet theory, predators should consume low-quality prey only when the availability of better-quality prey is low. The model of short-term apparent competition predicts, somewhat contradictorily, that low-quality prey co-occurring in the same patches with high-quality prey should be attacked more than low-quality prey in patches containing no high-quality prey. The prediction should apply, in particular, to poor environments. We compared vole attacks on experimental birch seedlings (low-quality prey) in patches with and without herbs (high-quality prey) in experimental enclosures with non-depleted or depleted herbaceous vegetation. Voles attacked fewer birch seedlings in the non-depleted enclosures compared to the depleted ones. They attacked more birch seedlings in patches with herbs than in patches without herbs independently of food depletion in the enclosure. Tree-seedling predation increased with vole density, but the increase was more pronounced in the depleted enclosures. These results may be useful for explaining and controlling natural predation of tree seedlings by voles.

Temporal patterns of moose-vehicle collisions with and without personal injuries

Collisions with wild ungulates are an increasing traffic safety issue in boreal regions. Crashes involving smaller-bodied deer species usually lead to vehicle damage only, whereas collisions with a large animal, such as the moose, increase the risk of personal injuries. It is therefore important to understand both the factors affecting the number of moose-vehicle collisions (MVCs) and the underlying causes that turn an MVC into an accident involving personal injuries or fatalities. As a basis for temporal mitigation measures, we examined the annual and monthly variation of MVCs with and without personal injuries. Using a 22-year-long (1990-2011) time series from Finland, we tested the effect of moose population density and traffic volume on the yearly number of all MVCs and those leading to personal injuries. We also examined the monthly distribution of MVCs with and without personal injuries, and contrasted the Finnish findings with collision data from Sweden (years 2008-2010) and Norway (years 2008-2011). Both moose population abundance indices and traffic volume were positively related to the yearly variation in the number of MVCs in Finland. The proportion of MVCs involving personal injuries decreased during our 22-year study period. The monthly distribution of all MVCs peaked during the autumn or winter depending on country, while MVCs involving personal injury peaked in summer. Our study indicates that efforts to reduce MVCs involving personal injuries need to address driver awareness and attitudes during summer, despite most MVCs occurring in autumn or winter.

Intraspecific Competition, Growth, Chemistry, and Susceptibility to Voles in Seedlings of Betula pendula

We studied the effects of the intensity of intraspecific competition, as indicated by seedling density, and competitive success within populations, as indicated by seedling size, on the secondary chemistry of the stems of silver birch seedlings and their palatability to field voles. We found that the size of seedlings and their total phenolic concentrations were inversely related to stand density. Voles, however, did not discriminate between seedlings grown at the densities studied. Variation in competitive success was associated with several phenomena. Seedling size was positively related to the concentrations of several secondary compounds and to vole preferences, but negatively related to nitrogen concentration. We suggest that the ecological consequences of variation in seedling size cannot be predicted without knowledge of the mechanism behind the variation.

Effects of Fertilizers, Mulches and Land Contours on the Vegetative Growth of Sea Buckthorn Cultivars in Organic Farming

ABSTRACT The effects of different organic cultivation methods on the vegetative growth of two Finnish sea buckthorn (Hippophae rhamnoides L. ssp. rhamnoides) cultivars Terhi and Tytti was studied in an experimental field at a coastal area in Merikarvia, western Finland for 2 years. Cultivation methods included different fertilizers, designed for organic cultivation, mulches, organic and plastic, and land contours, flat surface vs. ridge. Two experiments were done. The first allowed the estimation of the effects of cultivar, fertilizer, land contour and all their interactions, while the other allowed the estimation of the effects of mulches, land contours and their interactions for the cultivar Tytti. Results indicated significant differences between the cultivars, cultivation methods and growing seasons. In the fertilization experiment bioapatite and biolan increased the stem diameters compared with control treatment. During the first growing season Terhi formed longer shoots than Tytti. Shoots grew longer on the ridge than on the flat surface in both cultivars. In the second growing season stem diameter was significantly thicker in Terhi than in Tytti, and the shoot number increased significantly in both cultivars on the ridge compared with previous growing season. The results of mulch experiment indicated that saplings grown with plastic mulch had more shoots than with all other mulch treatments. Furthermore, shoot growth, stem diameter and shoot number increased from the first to the second growing season. In conclusion, the careful selection of cultivation methods will strongly modify the growth of sea buckthorn and is essential to obtain the best berry yield.

Is transport distance correlated with animal welfare and carcass quality of reindeer (Rangifer tarandus tarandus)

BackgroundSlaughter reindeer are exposed to stress caused by gathering, handling, loading and unloading, and by conditions in vehicles during transport. These stress factors can lead to compromised welfare and trauma such as bruises or fractures, aspiration of rumen content, and abnormal odour in carcasses, and causing condemnations in meat inspection and lower meat quality. We investigated the statistical association of slaughter transport distance with these indices using meat inspection data from years 2004–2016, including inspection of 669,738 reindeer originating from Finnish reindeer herding areas.ResultsIncreased stress and decreased welfare of reindeer, as indicated by higher incidence of carcass condemnation due to bruises or fractures, aspiration of rumen content, or abnormal odour, were positively associated with systems involving shorter transport distances to abattoirs. Significant differences in incidence of condemnations were also detected between abattoirs and reindeer herding cooperatives.ConclusionsThis study indicates that in particular the short-distance transports of reindeer merit more attention. While the results suggest that factors associated with long distance transport, such as driver education, truck design, veterinary supervision, and specialist equipment, may be favourable to reducing pre-slaughter stress in reindeer when compared with short distance transport systems, which occur in a variety of vehicle types and may be done by untrained handlers. Further work is required to elucidate the causal factors to the current results.