Conifer leader browsing by roe deer in English upland forests: Effects of deer density and understorey vegetation

At moderate to high densities ungulates can impact negatively on forest crops and these may be managed by lethal control. In production forestry an understanding of the relationship between ungulate density, habitat-related factors and the incidence of tree damage may promote more efficient ungulate damage management than by lethal control alone. In plantation forests in the north east of England, the incidence of conifer leader browsing by roe deer (Capreolus capreolus) was positively associated with an index of deer density (at the site scale) and planted crop tree density (at the feeding patch scale) and was negatively associated with the relative abundance of palatable understorey vegetation (at the site scale). An interaction between the deer density index and palatable understorey browse abundance was positively associated with leader browsing. Coefficients from the optimal model were used to construct a browse probability surface across a matrix of values of deer dung density and palatable understorey vegetation abundance. This illustrated a very different relationship between dung density and conifer leader browsing probability across the various levels of palatable understorey vegetation abundance. From this we hypothesise that in areas of limited palatable understorey vegetation abundance, higher levels of culling may be required to achieve reductions in the incidence of conifer leader browsing than would be necessary in areas with moderate to high palatable understorey vegetation abundance. Improvements to understorey vegetation in concert with roe deer population control may enhance the efficiency of deer damage management in upland areas with nutrient-poor soils.     

Young conifer stands form a deer browsing refuge for an oak admixture: silvicultural implications for forest regeneration under herbivore pressure

There is little knowledge how ungulate pressure on forest regeneration may be mitigated by silvicultural methods. The knowledge is especially needed for artificially regenerated, deciduous tree species. We studied factors affecting browsing incidence by deer in the Pisz Forest District in Poland, an area where 10,000 ha of forest was damaged by a 2002 hurricane. In 2006, we established three experimental plots (in total, 22.6 ha), in which the main species was Scots pine (Pinus sylvestris) admixed with pedunculate oak (Quercus robur). The data on browsing were collected in 2008–2015. In general, oak browsing incidence was unrelated to oak planting density. On a plantation scale, it was significantly affected by the pine age. Although in each variant all the oaks were browsed for four consecutive years (2009–2012), in 2013 browsing incidence began to decrease. When the pines grew higher and formed a physical barrier, it was harder for deer—roe deer (Capreolus capreolus), red deer (Cervus elaphus) and moose (Alces alces)—to move through and locate the oaks. Moreover, within plantations, oak browsing incidence was higher in the patches with shorter pines. Browsing of individual saplings or small groups of saplings was also negatively affected by the height of neighbouring pine saplings. Oak density influenced deer selectivity depending on the tree height. In a low oak tree density, browsing incidence was unrelated to oak height, while in higher tree density, deer selected oaks of the height between 40 and 100 cm. We postulate that deciduous admixture in a coniferous (unattractive) stand can be planted with a few year delay. Older coniferous trees should impede locating of attractive tree species by deer and the browsing incidence.     

Reduction of herbivore density as a tool for reduction of herbivore browsing on palatable tree species

Browsing of overabundant free-living herbivores often limits the natural as well as artificial regeneration of forest in Central-European Mountains. The aim of the study was to assess the efficiency of the extensive reductions of herbivore populations for protection of forest regeneration in preferred areas. We analysed the relationship between the intensity of shoot browsing and relative density of herbivores in viewpoint of natural regeneration of secondary mountain spruce stands with low proportion of broadleaved trees in Králicky Sněžník Reserve (Czech Republic). The distribution of seasonally migrating herbivores was established by counting faecal pellet groups (standing crop method) in growing season. The intensity of browsing of spruce, beech and rowan was assessed using the proportion of browsed shoots on individual tree sapling. Density of red deer was re-counted from the number of pellet groups and it was 15–56 individual/km². The intensity of spruce browsing was low in the whole area in all seasons. In general, the intensity of rowan and beech shoot browsing was high in the whole area. There were no correlations between deer density and browsing intensity of rowan (browsing was severe in all plots). We conclude that the natural regeneration of attractive trees and shrubs is nearly impossible in habitats where proportion of these food items is too small, even when the density of herbivores is low. Reduction of herbivores density is useful for protecting spruce and other tree species with low preference by herbivores. Forest managers should take into account the high palatability of deciduous tree species and distribution of herbivores on localities. Preference of localities is often based on grasses in the food supply. Regeneration of highly palatable tree species requires both low density of herbivores and sufficient protection of saplings.     

Spatial heterogeneity of winter forest resources used by deer

Monitoring red deer (Cervus elaphus) and roe deer (Capreolus capreolus) populations is a key aspect of wildlife management in Europe, so the utilization of resources must be considered. However, the spatial distribution of resources used has often been overlooked. We studied spatial heterogeneity of winter forest resources used by deer and applied an indirect method to evaluate the browsing pressure of these cervids in a forest of the Cévennes National Park (Lozère, France). We analyzed the pattern of browsing by principal component analysis (PCA) and graphical display. We demonstrated that heather (Calluna vulgaris), bilberry (Vaccinium sp.) and beech (Fagus sylvatica), which figured in more than 50% of the browsing observed, were unevenly consumed in the study area. Moreover, the deer consumed more beech outside high beech forest. Our methodology provides a helpful tool to monitor browse–ungulate interaction by taking into account the availability of key browse resources.     

Landscape effect for the Cervidaes Cervidae in human-dominated fragmented forests

We analyse the relationships between the main Cervidae [moose (Alces alces), red deer (Cervus elaphus) and roe deer (Capreolus capreolus)] species and a complex of environmental factors in an extensive fragmented landscape of Central Lithuania. The highest determining positive influence on moose density was the proportions of wet forest sites. In forest complexes with fewer proportions of wet sites, the most important factor was the total forest area. The proportion of shrub cover, upland and dense undergrowth area, and road density also has significant effect on moose density. The total area of forest complexes has the highest determining positive influence on red deer density. The highest density of red deer was calculated in large forest complexes (>2,745 ha) with a <17.6 % proportion of pine and <36.5 % of deciduous forests. Other significant factors were core area, road density and urbanization level. Forest edge density has the highest influence on the roe deer populations. The highest density of roe deer was recorded on forest areas with >51 m ha^?1 of edges in wet forest (>25.4 %) dominating areas. The proportion of deciduous, coniferous mixed and pine forest, also shrub and density of edges also had significant effect.     

Dispersal of vascular plants by game in northern Germany. Part I: Roe deer (<Emphasis Type="Italic">Capreolus capreolus</Emphasis>) and wild boar (<Emphasis Type="Italic">Sus scrofa</Emphasis>)

The endozoochorous and epizoochorous dispersal of vascular plant species by roe deer (Capreolus capreolus) and wild boar (Sus scrofa) was investigated in forest areas of Schleswig-Holstein and Lower Saxony, Germany. The primary aim of this study was to learn about which plant species and in what numbers diaspores are dispersed by the two wild ungulate species. In particular, the significance of zoochory for species composition and biodiversity of forests was evaluated. Fresh faecal pellets were collected from April–November 2001 in the forests of the two study areas. In addition, the coats and hooves of shot roe deer and wild boar were brushed out. The number of viable seeds was determined by greenhouse germination (seedling emergence method). The samples were spread in trays over sterilized soil from the study forests and were kept under controlled conditions in the greenhouse for 12 months. A total of 2,473 individuals from 77 vascular plant species were recorded. While roe deer exceeded wild boar concerning seed contents in the faeces, the significance of roe deer for epizoochorous dispersal was relatively low compared with wild boar. An analysis of the habitat preference of the vascular plant species dispersed by the two ungulate species revealed a high proportion of species growing in forests as well as in the open landscape, and also of non-forest species, while woody plants and herbaceous species closely tied to forest habitats were severely underrepresented. We also discuss consequences for forest ecology and nature conservation.     

Ungulate browsing on conifers during summer as revealed by DNA

Young trees are particularly vulnerable to browsing by ungulates, since most, or all, of their canopies are within browsing height. In tree species with strong apical dominance, browsing may also affect the structural development of the tree, causing impaired timber quality. Across Sweden, ungulate communities comprise multiple coexisting species, making it a challenge to determine which herbivore species have caused the browsing damages. However, correct identification of the culprits is pivotal for the appropriate management actions to be undertaken. In central Sweden, forest plantation owners recently reported a perceived increase in browsing damages on conifers, primarily Scots pine (Pinus sylvestris). Concurrent with this increase in browsing damages, they noticed an increase in the population of red deer in the area, leading them to suspect that the red deer (Cervus elaphus) were the primary browsers responsible for the damages. Browsed twig samples were sent to us so that we could identify the responsible browsing species using DNA. We discovered that 73.7% of the damages were actually attributable to moose (Alces alces) with 24.7% caused by red deer and 1.5% by fallow deer (Cervus dama). DNA diagnostics can thus yield important information regarding multispecies assemblages enabling managers to correctly identify the relative contributions of different species to browsing damages.     

Ecological functions of persistent Japanese cedar litter in structuring stream macroinvertebrate assemblages

Stream macroinvertebrate assemblages are expected to be affected by the abundance and constitution of litter from surrounding forests. We compared forest floor cover, overland flow, stream environment, and stream macroinvertebrate assemblages between the catchments of a Japanese cedar plantation (CP) and a primary deciduous forest (DF). Both systems experience excessive deer browsing. Understory vegetation cover was higher in the DF than in the CP in summer, although cover was low (<20 %), possibly because of excessive deer browsing. Litter cover was much higher in the CP than in the DF in summer as a result of the long abscission period, slow breakdown, and low rate of dispersal of Japanese cedar litter compared to deciduous litter. Monthly overland flow was always lower in the CP than in the DF, and substrate size was smaller in the DF stream. In the CP, cedar litter accumulated in the stream, probably because of its low breakdown rate and morphology, and abundant shredder taxa characterized the macroinvertebrate assemblage. In contrast, abundant burrower taxa characterized the macroinvertebrate assemblage in the DF stream. These results imply that Japanese cedar litter functions in structuring the macroinvertebrate assemblage by supplying persistent food resources for detritivores, and by buffering fine sedimentation via overland flow under excessive deer browsing.     

Modeling successional patterns of high-elevation forests under changing herbivore pressure – responses at the landscape level

We describe an ecological risk assessment for determining the potential long-term impacts of browsing by red deer, roe deer and chamois on the stand dynamics of mountain forests in xeric parts of Central Europe. The assessment is performed by applying a forest succession model of the FORET/JABOWA type which was supplemented with an empirically based browsing subroutine to simulate the effects of browsing by red and roe deer, and chamois. The following scenarios are assumed: (1) no browsing; (2) actual browsing intensity as determined in field trials; (3) browsing intensity twice as high as in scenario (2); and (4) browsing intensity three times as high as in scenario (2). The simulations for two different forest sites in the subalpine region of Eastern Switzerland revealed that heavy browsing can alter development and composition of the observed forests. The extent of this alteration was influenced not only by high browsing intensity, but also by the selection of tree species which were browsed on a particular site at the same time. Taking into account all the uncertainties of the model approach, we conclude from our preliminary studies that, in the regions considered, even strong herbivore pressure (2–3 times today's values) is not a major threat for the survival of the forest as a biological resource, i.e. the long-term total woody biomass is not altered significantly and the changes in the successional pathways are not dramatic. High browsing intensities, however, alter the forest structure considerably. We found that heavily browsed forests tend to be more open, mortality is higher and trees reach an intermediate and adult size quicker. This shortened development cycle of the stands may have implications for forest functions. The risk assessment yields critical values for mean browsing intensity, ‘MBI', (Pinus cembra/Pinus mugo: 30%; Picea abies: 50%; and Larix decidua: 40%), below which successional patterns and forest structures with browsing are not significantly different from forest succession without browsing.     

Habitat selection by ungulates in relation to predation risk by wolves and humans in the Białowieża Forest, Poland

Predation risk is an important factor influencing the distribution of ungulates and their impact on forest structure. However, simultaneous predation risk by wolves and humans is rarely considered in the analyses of habitat selection by ungulates. We counted ungulate pellets on transects to analyse the influence of wolves and humans on ungulate density distribution in the Białowieża Forest, Poland. We assessed whether (1) forest exploitation influenced ungulate habitat selection, (2) ungulate density was higher in areas without human hunting, (3) ungulates avoided the surroundings of a major road, (4) prey density was higher in the strife zone between home ranges of wolf packs both in the presence and absence of human hunting, (5) ungulates avoided areas selected by wolves, and (6) wolf kill sites were in high prey density areas. Red deer (Cervus elaphus) and wild boar (Sus scrofa) selected unexploited over exploited forests and areas without hunting, whereas roe deer (Capreolus capreolus) preferred exploited forests. Wild boar and European bison (Bison bonasus) avoided the area within 300 m of a major road, whereas we could not detect any avoidance by red or roe deer. Prey density was not higher in wolf strife zones, regardless of human hunting. Ungulates did not avoid areas selected by wolves. Wolves killed red deer in areas with prey density of about 4 red deer/km², regardless of whether the average red deer density in those areas was higher or lower. We conclude that habitat alteration by forest exploitation and hunting by humans influenced the density distribution of ungulates more than predation risk by wolves.     

Effects of silvicultural cleaning in mixed pine‐deciduous stands on moose damage to scots pine (Pinus sylvestris)

Silvicultural cleaning is commonly carried out in young stands to control competition between conifers and deciduous tree species. However, it has been questioned whether this practice affects moose (Alces alces L.) browsing on Scots pine (Pinus sylvestris L.) with respect to damage at the stand level. In this study, moose winter browsing was examined in relation to food availability in 19 Scots pine stands divided into silviculturally cleaned and non‐cleaned blocks. Cleaning had a negative effect on moose foraging in terms of reduced density, biomass availability, and height of the deciduous tree species. The total biomass consumed by moose was significantly lower on the cleaned blocks than on the non‐cleaned ones. There were no differences between the treatments in the amounts of pine consumed and in moose damage to pines. The density or biomass available of different deciduous tree species did not explain the variation in moose browsing on pine. In conclusion, timing of silvicultural cleaning with reference to moose browsing should be taken into account. If pines are not overtopped by deciduous trees, as in the present study, silvicultural cleaning is not necessary to prevent moose damage.     

Influence of variable retention harvests on forest ecosystems: Plant and mammal responses up to 8 years post-harvest

Green-tree retention systems are an important management component of variable retention harvests in temperate zone coniferous forests. Residual live trees (“legacy trees”) provide mature forest habitat, increase structural diversity, and provide continuity in the regenerating stand. This study was designed to test the hypotheses that, at up to 8 years after harvest, abundance and species diversity of communities of (i) understory plants and (ii) forest-floor small mammals, and (iii) relative habitat use by mule deer (Odocoileus hemionus), will decline with decreasing levels of tree retention. Communities of plants and forest floor small mammals were sampled in replicated clearcut, single seed-tree, group seed-tree, patch cut, and uncut forest sites in mixed Douglas-fir (Pseudotsuga menziesii)—lodgepole pine (Pinus contorta) forest in southern British Columbia, Canada from 2000 to 2003 (5–8 years post-harvest). Habitat use by mule deer was measured during summer and winter periods each year from 1999 to 2003 in these same sites.     

Stand Structure in Pine,Spruce and Deciduous Forests: A Comparison Between Finnish and Russian Karelia

This study investigated the stand structure in pine, spruce and deciduous forests in the border district of Finland and Russia. A total of 46 mature forest stands was selected as pairs, the members of each pair being as similar as possible with respect to their forest site type, age, moisture and topography. The stands were then compared between the two countries by means of basal areas and number of stems. The proportions of dominating tree species were 2-12% lower, and correspondingly the proportions of secondary tree species higher, in Russian forests. The density of the forest stock was also higher in each forest type in Russia. The forests in the two countries differed most radically in terms of the abundance of dead trees. The amount was two to four times higher in Russian deciduous and spruce forests, and in pine forests the difference was 10-fold. The stand structures indicated that Russian coniferous stands, in particular, were more heterogeneous than intensively managed pine and spruce stands in Finland.     

Natural forage composition decreases deer browsing on Picea abies around supplemental feeding sites

In southern Sweden, maintaining high cervid densities through supplemental feeding has become a common management practice. We aim at investigating deer browsing pressure on young Norway spruce in relation to distance from supplemental feeding sites. Because available forage is considered important in understanding browsing patterns, we modeled several factors affecting food availability, and their interaction effect with distance. We confirmed earlier studies about a locally high browsing pressure on natural vegetation adjacent to supplemental feeding sites where browsing pressure declined with distance and alternative forage abundance. Novel is that browsing on spruce occurred in 27.6% of the investigated plots. The browsing pressure of those plots averaged 9%. Distance was the most important factor in relation to browsing. The interactive effect of occurring field layer (FL), and deciduous trees was also highlighted as these significantly affected the relationship between browsing pressure on spruce and distance. In the studied conditions, browsing pressure ceased at ca. 205 m, whereas in scenarios of an abundant FL, browsing levels were negligible already at 0 m from supplemental feeding sites. We suspect that most of the browsing was caused by fallow deer in our study area.     

Influence of forest riparian vegetation on abundance and biomass of nocturnal flying insects

Despite widespread recognition of linkages between vegetation and insects, understanding of the ecological mechanisms underlying these relationships is limited. Better comprehension of relationships linking abundance and biomass of insects to vegetation would increase accuracy of predictions of the effects of forest management activities on insect communities. This knowledge could also be pivotal to understanding predator–prey dynamics linked to insect populations. We sampled nocturnal flying insects and measured vegetation characteristics in 34 stream reaches in conifer-dominated forests of the Oregon Coast Range in the Pacific Northwest of the United States. We considered five a priori hypotheses (resource quality, resource diversity, resource abundance, resource concentration, and stream cover hypotheses) that could explain mechanisms underlying associations between riparian vegetation and nocturnal flying insects, and used an information-theoretic approach to determine the relative strength of evidence for each. The resource quality hypothesis, which predicts that abundance and biomass of insects increases with cover of deciduous vegetation, explained substantial variation for nearly every order of insect investigated, whereas the remaining hypotheses explained relatively little. Abundance and biomass of insects had stronger associations with characteristics of canopy trees than with characteristics of shrub or understory trees, suggesting that deciduous trees are an important habitat element for nocturnal flying insects in these areas. Resource managers planning riparian vegetation management in conifer-dominated forests should be aware that manipulation of the cover of deciduous trees in riparian areas could have a large impact on these insects and their vertebrate predators. By providing information on forest canopy composition, remote sensing may offer a low-cost tool for identifying areas with high abundance and biomass of insects during conservation planning.     

Effect of stand age on bird communities in late-successional Macedonian pine forests in Bulgaria

To gain insight into the question of which vegetation characteristics have the most influence on avian assemblages in late-successional forests, the habitat preferences of bird-guilds in old-growth endemic forests of Macedonian pine were studied over 3 years in the Pirin National Park, Bulgaria. Bird–habitat relationships were investigated by comparing vegetation characteristics, and bird species richness, diversity, abundance, and guild structure of birds (determined according to food type, foraging and nesting sites) between mature (60–100 years old) and over-mature (>120 years old) Macedonian pine forest stands. Studied forest age-classes differed mainly by the density, height and diameter of trees, and the amount of dead wood. The first one of these parameters decreased and the latter two parameters increased with the forest succession. The difference in the vegetation structure affected the abundance of bird-guilds and thus, the overall bird abundance and the structure of avian assemblages within Macedonian pine forests. There was no significant difference in bird diversity among studied forest age-classes, but the overall bird abundance increased with forest maturation. Analyzed by study plots, species richness was higher in over-mature forests, but at cluster level, there was no significant difference between mature and over-mature forest age-classes. Half of the studied (insectivorous, hole- and ground-nesters, bark- and canopy-foraging bird species) guilds were more abundant in over-mature forests, while there was no bird-guild exhibiting a preference for mature forest stands. The abundances of bird-guilds were correlated with tree height, diameter at breast height and the amount of dead wood between the studied forest age-classes and this might explain their preferences for over-mature pine forests. Therefore, for future sustainable management of these endemic forests and the conservation of their avifauna, efforts should focus on protecting the remaining native old-growth forest stands and the importance of the structure of Macedonian pine forests on their bird assemblages should be considered in forestry practices.     

Simulating responses of Northeastern China forests to potential climate change

IntroductionItissurethatpresentelevatiollsofCO2a11dotllergrcc11-housegasesinducedbyhumanactivitiesaren1akli1gglobalclimategothroughinexperielICedcl1anges(Scl1le-subgerl987).Thecurrentquasi-equilibriulllstatesofbio-sphereecosystCm,esPeciallyterrestrialecosystems,wouldbebrokenbecausetl1estructure,fu11ction,distributio11andtlledynamicsofanyexistedecosystemsareIberesultsoflongtermadaptationofbio-systemtocurrentclin1ate.Theec()systemsdistributedinhighlatitlldeareawouldhavemuchbiggerchai1ge(Bona…     

Do ungulates preferentially feed in forest gaps in European temperate forest?

Ungulate populations across Europe have been strongly increasing over the past decades. Simultaneously with this increase, concerns about the impact of ungulates on forest systems, and forestry specifically, are increasing. In this study we discuss how the common forestry practice of creating clear cuts in relatively homogenous, managed forests may increase the potential impact of ungulates. Growth of trees in full light conditions is generally higher, but due to higher photosynthetic activity they tend to have higher C:N ratio in their leaves thus decreasing food quality. Next to that, biomass of herbaceous vegetation is enhanced in clear cuts. These changes likely affect foraging decisions of ungulates and it has been suggested that ungulates forage in forest gaps rather than in closed forest. We tested this hypothesis by using an experimental approach. The experiment was conducted in the Białowieża Primeval Forest in Poland, where a full assemblage of native large herbivores occurs. Six plots (6 m × 6 m) inside small clear cuts were compared to six control plots in adjacent closed forest. To exclude the effect of differences in number and species composition of available tree saplings, equal numbers of trees saplings of five species were planted at each plot. Ungulate visitation frequency and visitation time were measured by means of three methods: track plots, camera- and video trapping, and pellet counts. Visitation frequency of all ungulates combined (European bison, red deer, roe deer, moose and wild boar) was almost twice as high inside forest gaps compared to closed forest. Also cumulative visitation time by all ungulates tended to be higher inside forest gaps. Red deer showed the strongest preference for gaps, and duration of single visits was almost seven times longer for forest gaps than in closed forest. The observed preferential foraging of ungulates in forest gaps leads to an uneven distribution of their browsing behaviour. Hence, the creation of forest gaps by clear cutting followed by reforestation provides attractive foraging patches for ungulates potentially leading to high damage. In this way, forestry practices may enhance damage of ungulates to plantations especially when due to management the surrounding forest has a low carrying capacity for ungulates. We suggest that there is much to gain if management approaches would focus at influencing foraging behaviour of ungulates and reduce their concentration in forest gaps, rather than purely focusing on population control.     

Tree effects on the chemical topsoil features of oak, beech and pine forests

We aimed to study tree effects on the chemical properties of forest soils. We compared soil features of three types of forest ecosystems, each with four stands (replicates): beech forests (Fagus sylvatica), oak forests (dominated by Quercus pyrenaica) and pine plantations (Pinus sylvestris). Five samples from the top 10 cm of soil were taken per stand, from which pH, organic matter content (O.M.), total nitrogen (N) and available calcium (Ca²⁺), magnesium (Mg²⁺), potassium (K⁺) and sodium (Na⁺) were determined. Litter layer depth was measured at each soil sampling point. We also measured tree density and crown diameters at each stand. Our results indicated that soil samples from the four pine plantation stands were more similar while oak and beech stands were characterised by great variability in terms of soil properties and leaf litter depth. Although the identity of the dominant tree species significantly influenced several topsoil chemical properties (increase in pH and available cations in oak forests and higher organic matter and total nitrogen in beech and pine ecosystems), there were other important factors affecting soil features that may be taken under consideration. Differences between soil properties of the three types of forest ecosystems were mainly related to the characteristics of the litter layer and less related to the tree layer structure. Finally, the establishment of pine plantations in naturally deciduous tree areas made the topsoil features more homogeneous.