The puzzle of forestry and cervid interactions : a missing piece is in the understory

Shrubs of the family Ericaceae, including bilberry (Vaccinium myrtillus), cowberry (V. vitisidaea) and heather (Calluna vulgaris), often dominate the understory in Eurasian boreal and cold-temperate forests. These ericaceous shrubs play crucial roles in forest ecosystems, acting as foundation species for forest communities, as well as influencing carbon cycles and the delivery of other ecosystem services. They also provide a key food resource for various wildlife, including cervids. However, over recent decades, forestry induced changes to the tree layer is thought to have reduced habitat suitability and thus the abundance of these shrubs in Sweden. Nevertheless, the precise nature of how the overstory impacts ericaceous shrubs remains largely unquantified. This thesis investigated the impact of the forest overstory on three species of ericaceous shrubs, focusing on the tree species composition and density of forest stands distributed along a large latitudinal gradient in Sweden. We carried out biomass collections and measurements, surveys, and a three-year browsing exclosure experiment. We quantified how forest stand characteristics shaped the above-ground biomass, growth, morphology, and macro-nutritional composition of these shrubs. We determined that Norway spruce (Picea abies) dominated stands had comparatively less above-ground biomass of the three focal species than Scots pine (Pinus sylvestris) stands; their plants were also shorter, and a larger proportion of their biomass provided suitable forage for cervids (I). These shorter shrubs also provided a larger proportion of new shoot biomass (II) and had a different macronutrient composition (IV) compared to shrubs in more open stands. These findings indicate that forest owners’ decisions regarding tree species composition and density have a strong influence on the biomass, morphology, and nutritional composition of these plant species in Sweden. Three years of exclusion to large cervids’ browsing did not reveal differences in the plants’ growth and morphology in pine dominated stands (III). In addition to providing new insights into the ecology of ericaceous shrubs, we also provide biometric functions to predict the above-ground and forage biomass of the three shrubs (I), and models to predict their production of annual shoot biomass (II). In summary, our results provide a better understanding of canopy influences on ericaceous shrubs growing in conifer forests. This thesis provides tools that can help improve the management of these shrub species, and greatly increase our ability to determine stand and landscape scale availability of this food resource for cervids. We consider our findings within the larger context of landscape scale management, and highlight the importance of ensuring the continued maintenance of these ericaceous shrubs and the diverse range of ecosystem services they provide

Using camera traps to compare the habitat choice of different deer species in hunting versus non-hunting season

A general increase in ungulate populations calls for a better understanding of their habitat use and movement at small spatial scales. This understanding is necessary for the development of useful management actions to solve possible human-wildlife conflicts. One proposed management action is to use the indirect effects of hunting. Hunting activities potentially increase the feeling of risk of being predated perceived by ungulates, which could decrease their fitness by choosing to move to less risky areas with a lower quality of food. In this study, I wanted to determine how habitat use of ungulates changed between seasons in a peninsula in northern Sweden where four species of ungulates coexist: moose (Alces alces), roe deer (Capreolus capreolus) red deer (Cervus elaphus) and fallow deer (Dama dama). I hypothesized that during the hunting period ungulate habitat selection would be driven by hunting risk perception, which would imply a stronger selection for forest sites with low visibility (high denseness of understory vegetation), than for forest sites with high visibility. Outside of the hunting period, I hypothesized that habitat selection would be driven by food availability and preference, making ungulates choose the most productive areas. To study this, I used data collected with camera traps, from which I obtained the passages for the four ungulate species and built models for naïve occupancy, occupancy and passage rates to determine which habitat type was more visited per season and species. I found different habitat selection patterns for three of the four studied species. Most notably, passage rates of moose were higher in open sites outside of the hunting season, while there was no difference between the habitat types during the hunting period. These differences give an insight in the importance of developing specific management per species even if they are situated in a multispecies system. My research confirms that hunting could potentially be used as a management strategy to change the habitat selection of moose away from open areas, such as planted clear-cuts

Cost associated with a relapse-free patient in multiple sclerosis: a real-world health indicator

Background: The efficacy and safety of disease-modifying therapies (DMTs) in multiple sclerosis (MS) are well known; however, owing to their high costs, determining real-world outcomes is essential to evaluate the cost-effectiveness of different therapeutic strategies. This study aimed to investigate the variability in the annual cost of DMTs associated with a relapse-free patient in a representative population cohort of relapsing-remitting MS (RRMS), and whether this could serve as an appropriate health indicator. Methods: We analyzed the patients followed up in our MS clinic during the years 2016 and 2019, and selected patients belonging to our health district diagnosed with RRMS. The treatment cost associated with a relapse-free patient was the ratio between the total cost of DMTs and the number of relapse-free patients, treated and not treated, during the year of the study. Results: A total of 158 patients with RRMS in 2016 and 183 in 2019 were included in our study. In 2016, 101 patients with RRMS (63.9%) received treatment with DMTs and 120 patients (75.9%) remained relapse-free. The mean cost of DMTs per patient in 2016 was 7414.3 (95% confidence interval [CI]: 6325.2-8503.4) considering all the patients (treated and not treated). In 2019, 126 patients (68.9%) received DMTs and 151 patients (82.5%) remained relapse-free. The mean cost of DMTs per patient in 2019 was 6985.4 (95% CI: 5986.9-7983.9) considering all the patients. The cost per year of DMTs to achieve a relapse-free patient was 9762.2 in 2016 and 8465.8 in 2019. Conclusions: The treatment cost per year to achieve a relapse-free patient was stable during successive measurements in the same population. Therefore, it may be considered a good real-world health indicator for patients with RRMS treated with DMTs

Climate change and deer in boreal and temperate regions: From physiology to population dynamics and species distributions

Climate change causes far-reaching disruption in nature, where tolerance thresholds already have been exceeded for some plants and animals. In the short term, deer may respond to climate through individual physiological and behavioral responses. Over time, individual responses can aggregate to the population level and ultimately lead to evolutionary adaptations. We systematically reviewed the literature (published 2000–2022) to summarize the effect of temperature, rainfall, snow, combined measures (e.g., the North Atlantic Oscillation), and extreme events, on deer species inhabiting boreal and temperate forests in terms of their physiology, spatial use, and population dynamics. We targeted deer species that inhabit relevant biomes in North America, Europe, and Asia: moose, roe deer, wapiti, red deer, sika deer, fallow deer, white-tailed deer, mule deer, caribou, and reindeer. Our review (218 papers) shows that many deer populations will likely benefit in part from warmer winters, but hotter and drier summers may exceed their physiological tolerances. We found support for deer expressing both morphological, physiological, and behavioral plasticity in response to climate variability. For example, some deer species can limit the effects of harsh weather conditions by modifying habitat use and daily activity patterns, while the physiological responses of female deer can lead to long-lasting effects on population dynamics. We identified 20 patterns, among which some illustrate antagonistic pathways, suggesting that detrimental effects will cancel out some of the benefits of climate change. Our findings highlight the influence of local variables (e.g., population density and predation) on how deer will respond to climatic conditions. We identified several knowledge gaps, such as studies regarding the potential impact on these animals of extreme weather events, snow type, and wetter autumns. The patterns we have identified in this literature review should help managers understand how populations of deer may be affected by regionally projected futures regarding temperature, rainfall, and snow

From simple metrics to cervid forage: Improving predictions of ericaceous shrub biomass

Common understory vegetation species such as the ericaceous shrubs bilberry (Vaccinium myrtillus), cowberry (V. vitis-idaea) and heather (Calluna vulgaris), are key forage plant species for moose and other large herbivores, as well as fulfilling many additional ecosystem functions and services. Here we developed models to predict above-ground biomass of these ericaceous species in coniferous forests, using data on their percentage cover, height, and different stand characteristics. We also built models to understand how the aforementioned variables affect the proportion of the shrubs commonly utilized as forage by large herbivores. We found that the per-centage cover of shrubs was the most important explanatory variable when predicting above-ground biomass, explaining 51%, 47% and 71% of the variation (marginal R2) in bilberry, cowberry and heather biomass, respectively. By adding ramet height to the model with percentage cover, the variation explained increased to 77% for bilberry, 75% for cowberry and 87% for heather. The best outcome for candidate models was obtained by adding stand site index and spruce basal area to the model, improving the variation explained in bilberry to 83%, to 81% for cowberry, and 91% for heather. When modelling the proportion of the shrubs commonly uti-lized as forage by large herbivores, stand site index and spruce basal area often played important roles. Some of the best fitting models for forage biomass explained 51% of the variation in bilberry, 59% in cowberry and 30% in heather. Site location did not have a major role in improving the variability explained in either type of model, which indicated the applicability of the models regardless of study location. Our models therefore have a high potential to be implemented in forestry decision support systems. Their inclusion should provide better large-scale estimations of forage resources, aiding forest management, and thereby taking an important step for-ward to determine the ecosystem carrying capacity of large herbivores

Small shrubs with large importance? Smaller deer may increase the moose-forestry conflict through feeding competition over Vaccinium shrubs in the field layer

The moose (Alces alces) is a dominant large mammalian herbivore in the world's boreal zones. Moose exert significant browsing impacts on forest vegetation and are therefore often at the centre of wildlife-forestry conflicts. Consequently, understanding the drivers of their foraging behaviour is crucial for mitigating such conflicts. Management of moose in large parts of its range currently largely ignores the fact that moose foraging is influenced by increasing populations of sympatric deer species. In such multispecies systems, resource partitioning may be driven by foraging height and bite size. Feeding competition with smaller species might replace larger species from the field layer and drive them towards higher foraging strata offering larger bites. This bite size hypothesis has been well documented for African ungulate communities. Based on a large diet DNA metabarcoding dataset we suggest that feeding competition from three smaller deer species (red deer Cervus elaphus, fallow deer Dama dama, and roe deer Capreolus capreolus) over Vaccinium shrubs in the forest field layer might drive moose towards increasing consumption of Scots pine (Pinus sylvestris) in Sweden. We found that in areas of high deer density, moose diets consistently contained less Vaccinium and higher proportions of pine over three spring periods. Utilization of these food items by the smaller deer species was either unaffected by deer density or, for Vaccinium showed the opposite pattern to moose, i.e., increases of proportions in the diet of roe and red deer with increasing deer density. Availability of pine and Vaccinium, measured as proportion of available bites, did not explain the observed patterns. Our results suggest that managing key food items like Vaccinium and the populations of smaller deer may play an important role in controlling browsing impacts of moose on pine

Small shrubs with large importance? Smaller deer may increase the moose-forestry conflict through feeding competition over Vaccinium shrubs in the field layer

The moose (Alces alces) is a dominant large mammalian herbivore in the world’s boreal zones. Moose exert significant browsing impacts on forest vegetation and are therefore often at the centre of wildlife-forestry conflicts. Consequently, understanding the drivers of their foraging behaviour is crucial for mitigating such conflicts. Management of moose in large parts of its range currently largely ignores the fact that moose foraging is influenced by increasing populations of sympatric deer species. In such multispecies systems, resource partitioning may be driven by foraging height and bite size. Feeding competition with smaller species might replace larger species from the field layer and drive them towards higher foraging strata offering larger bites. This bite size hypothesis has been well documented for African ungulate communities. Based on a large diet DNA metabarcoding dataset we suggest that feeding competition from three smaller deer species (red deer Cervus elaphus, fallow deer Dama dama, and roe deer Capreolus capreolus) over Vaccinium shrubs in the forest field layer might drive moose towards increasing consumption of Scots pine (Pinus sylvestris) in Sweden. We found that in areas of high deer density, moose diets consistently contained less Vaccinium and higher proportions of pine over three spring periods. Utilization of these food items by the smaller deer species was either unaffected by deer density or, for Vaccinium showed the opposite pattern to moose, i.e., increases of proportions in the diet of roe and red deer with increasing deer density. Availability of pine and Vaccinium, measured as proportion of available bites, did not explain the observed patterns. Our results suggest that managing key food items like Vaccinium and the populations of smaller deer may play an important role in controlling browsing impacts of moose on pine

Small shrubs with large importance? Smaller deer may increase the moose-forestry conflict through feeding competition over Vaccinium shrubs in the field layer

The moose (Alces alces) is a dominant large mammalian herbivore in the world’s boreal zones. Moose exert significant browsing impacts on forest vegetation and are therefore often at the centre of wildlife-forestry conflicts. Consequently, understanding the drivers of their foraging behaviour is crucial for mitigating such conflicts. Management of moose in large parts of its range currently largely ignores the fact that moose foraging is influenced by increasing populations of sympatric deer species. In such multispecies systems, resource partitioning may be driven by foraging height and bite size. Feeding competition with smaller species might replace larger species from the field layer and drive them towards higher foraging strata offering larger bites. This bite size hypothesis has been well documented for African ungulate communities. Based on a large diet DNA metabarcoding dataset we suggest that feeding competition from three smaller deer species (red deer Cervus elaphus, fallow deer Dama dama, and roe deer Capreolus capreolus) over Vaccinium shrubs in the forest field layer might drive moose towards increasing consumption of Scots pine (Pinus sylvestris) in Sweden. We found that in areas of high deer density, moose diets consistently contained less Vaccinium and higher proportions of pine over three spring periods. Utilization of these food items by the smaller deer species was either unaffected by deer density or, for Vaccinium showed the opposite pattern to moose, i.e., increases of proportions in the diet of roe and red deer with increasing deer density. Availability of pine and Vaccinium, measured as proportion of available bites, did not explain the observed patterns. Our results suggest that managing key food items like Vaccinium and the populations of smaller deer may play an important role in controlling browsing impacts of moose on pine