Habitat use of large ungulates in northeastern Germany in relation to forest management

Estimating large herbivore density has been a major area of research in recent decades. Previous studies monitoring ungulate density, however, focused mostly on determining animal abundance, and did not interpret animal distribution in relation to habitat parameters. We surveyed large ungulates in the Biodiversity Exploratory Schorfheide-Chorin using faecal pellet group counts. This allowed us to explore the link between relative ungulate abundance, habitat use, and browsing damage on trees in a region with several types of forest, including unharvested and age-class beech forests, as well as age-class pine forests. Our results demonstrate that roe deer and fallow deer relative abundance is negatively correlated with large tree cover, and positively correlated with the cover of small shrubs (Rubus spec., Vaccinium spec.), and winter food supply. Habitat use of roe deer and fallow deer, as estimated by counting faecal pellet groups, revealed a preference for mature pine forests, and avoidance of deciduous forests. This differential habitat use is explained by different distributions of high quality food resources during winter. The response of deer to understory cover differed between roe deer and fallow deer at high cover percentages. The amount of browsing damage we observed on coniferous trees was not consistent with the relative deer abundance. Browsing damage was consistently higher on most deciduous trees, except for beech saplings which sustained less damage when roe deer density was low. Because roe deer is a highly selective feeder, it was reported to affect tree diversity by feeding only on trees with high nutritional value. Consequently, we propose that managing the number of all deer species by hunting is necessary to allow successful forest regeneration. Such an adjustment to deer numbers would need to account for both current tree diversity and alternative food resources. Our findings may be applicable to other forest landscapes in northeastern Germany including mature pine stands and differently harvested deciduous forests.     

Predicting intensity of white-tailed deer herbivory in the Central Appalachian Mountains

In eastern North America, white-tailed deer(Odocoileus virginianus) can have profound influences on forest biodiversity and forest successional processes.Moderate to high deer populations in the central Appalachians have resulted in lower forest biodiversity.Legacy effects in some areas persist even following deer population reductions or declines. This has prompted managers to consider deer population management goals in light of policies designed to support conservation of biodiversity and forest regeneration while continuing to support ample recreational hunting opportunities. However,despite known relationships between herbivory intensity and biodiversity impact, little information exists on the predictability of herbivory intensity across the varied and spatially diverse habitat conditions of the central Appalachians. We examined the predictability of browsing rates across central Appalachian landscapes at four environmental scales: vegetative community characteristics, physical environment, habitat configuration, and local human and deer population demographics. In an information-theoretic approach, we found that a model fitting the number of stems browsed relative to local vegetation characteristics received most(62%) of the overall support of all tested models assessing herbivory impact. Our data suggest that deer herbivory responded most predictably to differences in vegetation quantity and type. No other spatial factors or demographic factors consistently affected browsing intensity. Because herbivory, vegetation communities, and productivity vary spatially, we suggest that effective broad-scale herbivory impact assessment should include spatially-balanced vegetation monitoring that accounts for regional differences in deer forage preference.Effective monitoring is necessary to avoid biodiversity impacts and deleterious changes in vegetation community composition that are difficult to reverse and/or may not be detected using traditional deer-density based management goals.     

Short-term browsing by roe deer has little effect on survival and growth of sessile oak seedlings

We studied the effect of roe deer (Capreolus capreolus) browsing on the growth and mortality of sessile oak (Quercus petraea) seedlings. First, we measured the height and basal diameter, and counted the number of shoots of the 849 seedlings of an experimental plantation, 60 of which were individually protected by fencing. We then introduced two tame roe deer females every day for three weeks from late May to mid-June. Measurements and counts were repeated after roe deer removal, then once again the following winter. We found no significant effect of browsing on mortality, total height, or basal diameter of the seedlings. However, the browsed seedlings exhibited a lower number of shoots despite regrowth observed after roe deer removal. We propose to use the tolerance of oak to deer browsing to promote natural and inexpensive methods, to protect oak during regeneration, such as the spatial arrangement of plants or the use of slash or surrounding vegetation in favourable environments.     

Effects of white-tailed deer on vegetation structure and woody seedling composition in three forest types on the Piedmont Plateau

White-tailed deer (Ododcoileus virginiana) can substantially affect the structure and species composition of a forest. The tolerance of a forest community to browsing may vary by type as a result of varying biotic and abiotic factors of the environment. To date, no studies have compared the effects of browsing among forest communities within a physiographic region. We investigated the effects of browsing on vegetation structure and woody seedling composition in three forest types (oak–hickory, Virginia pine–eastern red cedar, bottomland hardwood) in Manassas National Battlefield Park (MNBP), Virginia, USA. We compared forb cover, vertical plant cover (0–1.5 m tall), and survival of tagged seedlings in 10 exclosed (2 m × 6 m) and 10 unexclosed plots in each forest type during a 5-year period. No differential effects of browsing were found among forest types. In all forest types, deer (67 deer/km²) suppressed forb and vertical plant cover to levels less than would be expected in the absence of deer. Seedling survival rates of most species were significantly reduced by browsing. By the 4th year of the study, box elder (Acer negundo), hickory (Carya spp.), and red maple (Acer rubrum) had been eliminated from unexclosed plots, and red and white oaks (Quercus spp.) dramatically reduced. Ash (Fraxinus spp.), black cherry (Prunus serotina), and hackberry (Celtis occidentalis), although significantly impacted, remained the most abundant species throughout the study. These findings suggest that white-tailed deer may be modifying the structure of the forest interior to the extent that it adversely affects wildlife species dependent on a dense understory to thrive. We predict that the future composition of forests in MNBP will shift towards stands with fewer species and a greater dominance of ash, black cherry, and hackberry, particularly in the oak–hickory and bottomland hardwood forests, where the majority of current dominants are most affected.     

Browsing by large herbivores on Scots pine (Pinus sylvestris) seedlings in mixture with ash (Fraxinus excelsior) or silver birch (Betula pendula)

Abstract

Food selection by large herbivores occurs at a hierarchy of scales, for example landscape, patch or plant. Several hypotheses regarding food plant selection on patch or plant level have been developed. In this cafeteria-type design field experiment, conducted during one winter immediately after planting, we tested the effect of species mixture on browsing by large herbivores (mainly roe deer) on Scots pine seedlings in mixture with seedlings of ash (highly preferred) or silver birch (less preferred). Browsing on Scots pine was not affected by species mixture, neither in terms of the number of browsed pines nor browsing intensity. Instead, browsed biomass was positively and significantly correlated to the total biomass available for browsing. Also, there were differences due to species, with ash being most browsed (44.6%), followed by Scots pine (18.9%) and silver birch (11.6%). Browsed biomass per browsed seedling, however, was largest for Scots pine. In addition, browsed seedlings were initially taller compared to unbrowsed seedlings for all species. The main management implication in this study is that the species mixture did not influence large herbivore browsing on Scots pine seedlings. Hence, removing or discouraging more (or less) attractive browse species in early stages of pine regeneration activities seems unnecessary from the point of large herbivore browsing.     

Mammalian browsing damage in the Mt. Cole State forest,southeastern Australia: analysis of browsing patterns,spatial relationships and browse selection

Browsing by mammals can have a substantial impact on the survival, growth and form of regenerating forest trees. This study investigated the severity and distribution of mammalian browsing damage, and the degree to which eucalypt seedlings (Eucalyptus spp.) were selected for browsing on three regenerating native forest coupes in southeastern Australia. Damage was greatest 6 months after eucalypt germination and at this time, both messmate (Eucalyptus obliqua) and blue gum (E. globulus) seedlings were browsed at similar intensity. Nine and 12 months after germination, messmate was browsed more heavily than blue gum. Consistent relationships between browsing damage and both distance from the forest edge and wallaby density were not observed. Analysis of use and availability data for messmate, blue gum and manna gum (E. viminalis) seedlings showed that messmate was selected for browsing more than expected by chance while manna gum was browsed less than expected. Mammalian browsing affects a substantial portion of Victorias native forest estate, and could alter the species composition of future forests. Research into the ecology of browsing species and the development of non-lethal browsing reduction strategies is seen as a priority for the management of mammalian browsing in Victoria.     

Responses of Young Norway Spruce (Picea abies) to Winter Browsing by Roe Deer (Capreolus capreolus): Effects on Height Growth and Stem Morphology

The effects of natural and simulated winter browsing by roe deer on mortality, growth and defects in tree form among young recently planted Norway spruces were studied in two field studies and one simulation (clipping) experiment. No effect of browsing or clipping on mortality was observed. However, height growth was reduced by browsing and clipping, and the reduction increased with increases in the number of years in which they were browsed or clipped. Browsing or clipping in three successive years reduced height growth by the equivalent of about 1 yr. Spruces frequently became multi-trunked and/or developed multiple leaders as long as browsing and clipping lasted. However, when the browsing or clipping ceased, almost all spruces became single-trunked again. A more persistent effect was that many of the multiple trunks developed into large, abnormal branches or "spike-knots". The characteristics of the spike-knots resulting from browsing and clipping were very similar to those caused by other types of damage. The results indicate that roe deer browsing on spruce is less harmful than many Swedish foresters have feared.     

Dynamic simulations of mixed broadleaved-Pinus koraiensis forests in the Changbaishan biosphere reserve of China

The development of mixed broadleaved-Korean pine (Pinus koraiensis Sieb. et Zucc.) forests in the Changbaishan Biosphere Reserve, located on the border with North Korea, was simulated using the gap model KOPIDE. Forest succession was simulated under three initial conditions from: (1) bare ground after clearcutting; (2) secondary forest; (3) old-growth forest. The simulations from the different initial conditions converged and support earlier successional theory that Korean pine is the climax species on the highlands of northeast China even under disturbed conditions. In addition to clear-cutting, the resilience of the forest to different levels of other human impacts, pine seed harvesting and selective cutting, was examined. These results further demonstrate that these forests possess a relatively stable structure characterized by the dominance of Korean pine. However, the model showed successional processes of the forest to be susceptible to high levels of pine seed harvesting. To predict forest dynamics at landscape scales, KOPIDE was linked with a Geographic Information System containing site and stand data sets. Running this model to simulate a forested area initially comprising several successional stages suggests that, in the absence of disturbance, Korean pine is likely to become increasingly dominant on the area over the next century.     

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.     

Interactions among forestry regeneration treatments,plant vigour and browsing damage by deer.

In a large field experiment we studied the influence of regenerationmethods on the extent to which roe deer (Capreoluscapreolus L.) browse on spruce (Picea abies L.Karst) seedlings. Our objective was to evaluate if treatments that are good atstimulating regeneration may increase browsing damage by deer. Data werecollected between 1993 and 1995, and in the winters of 1993–94 and1994–95 the frequency of browsed seedlings was 13.2% and 13.4%,respectively. The frequency of browsing damage varied considerably betweensitesand clearcuts. Browsing damage was more frequent when the regeneration methodsincluded insecticide treatments. Among insecticide-free treatments, browsingwasheavier on scarified plots than on herbicide-treated or control plots (in whichseedlings were planted on untreated ground and given no post-plantingtreatment). Containerised seedlings were browsed more than bare-rooted ones.Neither the age of clearcut when planting, nor removal of slash, had any effecton browsing. It was demonstrated that regeneration methods that increased plantvigour (as assessed by leader growth and needle colour index) led to morebrowsing damage. Thus, our results support the plant vigour hypothesis, whichstates that many herbivores prefer to feed on vigorous plants because they aremore nutritious. However, the difference in browsing damage betweencontainerised and bare-rooted seedlings could not be explained solely by theplant vigour hypothesis.     

Changes in the stand structure of a pine forest after rapid growth of Quercus serrata Thunb.

We studied the species composition and stand structure of secondary pine forests affected by pine wilt disease, caused by epidemic attacks of the nematode Bursaphelenchus xylophilus, in western Japan. Based on the species composition, the vegetation was divided into four types: (1) Cladonia rangiferina, (2) Wikstroemia sikokiana, (3) Quercus glauca, and (4) Gleichenia japonica. The sequence of types from (1) to (3) represents a successional series in accordance with topographical position. The relative basal areas of Rhododendron reticulatum and Juniperus rigida in the C. rangiferina and W. sikokiana types were larger than in the Q. glauca type. The relative basal areas of Q. serrata, Clethra barbinervis, and Eurya japonica in the C. rangiferina and W. sikokiana types were less than in the Q. glauca type. The mortality of light-demanding trees was higher in the Q. glauca type than in the C. rangiferina and W. sikokiana types. In stands that were severely affected by pine wilt disease, light was reduced and soil became moist after rapid growth of Q. serrata and other species which are not affected by the disease. The numbers of species and components of evergreen broad-leaved natural forests were decreased, because pine forests in the study area had been cut frequently and the land had degraded. Pine wilt disease has shifted the dominance of pine forests from Pinus densiflora to deciduous oaks such as Q. serrata and physical conditions seemed to provide a safe site for shade-tolerant plant species, which are components of evergreen broad-leaved forests. Moreover, the seed dispersal of evergreen oaks appears to be an important factor in the succession to evergreen broad-leaved forest in degraded areas.     

Effects of deer abundance on broad-leaf tree seedling establishment in the understory of <Emphasis Type="Italic">Abies sachalinensis</Emphasis> plantations

Browsing by sika deer (Cervus nippon) has significant negative effects on regeneration in many forests in Japan; however, the effects of browsing on regeneration processes have not been determined quantitatively. Our study was conducted in Abies sachalinensis plantations in seven tracts with differences in deer abundance on Hokkaido, northern Japan, to identify indicators for the effects of deer on the regeneration of broad-leaf species from observing seedlings. Five 5 × 20-m plots were located within each tract, and the densities of seedlings 30–200 cm tall and percentages of browsed seedlings were determined. We used sightings per unit effort (SPUE) by hunters and spotlight survey counts (SLCs) as indices of deer abundance for each tract. Seedling density was negatively correlated with deer abundance and coverage of dwarf bamboo, and basal areas of overstory trees also affected number of seedlings. Percentage of browsed seedlings was positively correlated with deer abundance, and it was affected by deer preferences among seedling species. However, the percentage of browsed seedlings was more clearly related to deer abundance than seedling density. There were few seedlings of tree species ≥100 cm tall in tracts with the highest deer abundance. Based on these results, deer abundances of SPUE >6 sightings per hunter-day or SLC >15 animals per 10 km are likely to prevent regeneration of broad-leaf species. The percentage of browsed seedlings and density and browsing damage on tree seedlings ≥100 cm tall are useful indicators of the effects of deer.     

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.     

White-tailed deer herbivory and timber harvesting rates: Implications for regeneration success

Herbivory by white-tailed deer (Odocoileus virginianus) can affect forest regeneration. Typical measures to ensure forest regeneration have included physical barriers or direct manipulation of deer densities. However, altering silvicultural practices to provide abundant deer forage has not been tested thoroughly. We examined browse species preferences and changes in herbivory rates in 1–6 year old regeneration areas from 2001 to 2004 in the central Appalachians on the MeadWestvaco Wildlife and Ecosystem Research Forest in West Virginia. Woody vegetation reached the maximum plot coverage by the 4th growing season. However, the establishment of less abundant woody species, such as northern red oak (Quercus rubra), may be inhibited when browsed greater than or proportionally to occurrence. Herbivory rates declined precipitously as the amount of early successional habitat increased on our study site. We conclude that providing approximately 14% of an area in well-distributed, even-aged managed forests can have substantial impacts on reducing herbivory rates. However, management practices also should consider harvesting effects on hard mast production, habitat requirements of other species, and hardwood lumber marketability.     

Deer Browsing and Impact on Forest Development

Abstract

Browsing by large herbivores can cause serious costs in forest production. The most important costs related to browsing damage are insufficient stand regeneration, volume losses and timber quality impairment. In Sweden, moose (Alces alces)and roe deer (Capreolus capreolus) are the most abundant deer species and therefore cause the majority of browsing damage. Balancing costs and benefits related to deer density is difficult since few data about the final losses in timber volume or quality impairment is available. Simulations of browsing and the impact on stand growth suggest that a minor or moderate browsing intensity has little effect on final harvest volume. The reason is that trees seem to recover some of the lost growth as they grow out of reach of the animals. Balancing between different uses of the forestry resource is complicated by our limited capability to predict the impact of different management regimes.     

Height growth of young larch (Larix kaempferi) in relation to the frequency of deer browsing damage in Hokkaido, Japan

The effect of browsing frequency by Sika deer (Cervus nippon yezoensis) on the height growth of Japanese larch (Larix kaempferi) in Hokkaido, Japan, was analyzed. Tree heights at the time of the census and at the start of the current growing season were determined for 100 trees selected randomly at each site. The tallest shoot on each tree was identified and the number of browsing occurrences on the current-year shoot was determined. Young larches browsed by deer repeatedly develop new shoots during a growing season. Larch is a browsing-tolerant species, and the average height growth of the most heavily browsed trees was >15 cm. Although resprouting partly compensated for decreased height growth caused by browsing, the annual increase in height decreased with increased browsing frequency. Thus, browsing frequency during a growing season best reflects the intensity of browsing damage to larch trees.     

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.     

Effects of browsing on recruitment and mortality of European aspen (Populus tremula L.)

Abstract

High browsing pressure may reduce or halt regeneration of browsing-prone tree species. In this study, exclosures were used to quantify the effects of browsing on vital demographic parameters in European aspen (Populus tremula L.) stands. The experiment focused on stands located in managed forest landscape with densities of 0.85 moose (Alces alces L.)km^?2. Other herbivores such as mountain hare (Lepus timidus L.) were present at densities common for this region and roe deer (Capreolus capreolus L.) at low densities. Recruitment and mortality of aspen ramets were recorded before and after the growing season, and over four consecutive years. Seven to 19% of the ramets within browsing reach were browsed annually. No differences were found in recruitment or mortality attributable to browsing per se. Instead, there were large among-stand variability in vital population parameters unrelated to browsing incidence. In general, aspen stands with high ramet density showed higher recruitment rates than stands with low ramet density. There was substantial variability in self-replacement capability unrelated to ecological factors. The results suggest that more attention should be given to finding and managing stands with high capacity for suckering, as these stands may have a disproportionate impact on aspen recruitment at the landscape scale.