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1.
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.  相似文献   

2.
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.  相似文献   

3.
Sallow (Salix caprea L.) and rowan (Sorbus aucuparia L.) constitute small proportions of the deciduous tree volume in Scandinavia, but are highly preferred winter forage for moose and red deer, which occur at historically high densities. Thus, a possible decline of these tree species has been indicated. Against this background, we have reviewed the life histories of relevance for browsing, as well as the basic biology and genetics of sallow and rowan. The species show similarities with respect to short lifespan, small size and sympodial growth pattern, which are risk factors in a browsing context. They also have high juvenile growth rate, important for growing quickly out of reach of browsers. Sallow depends strongly on disturbance for establishment and is more demanding with respect to soil and light conditions than rowan, possibly important for the substantially lower abundance of sallow on the Norwegian Forest Inventory plots. Similarly, the relative recruitment of small size classes of sallow is less than for rowan. Although recruitment is reported to be hampered in wintering areas with high moose or red deer densities, the inventory data, however, dating only back to 1994, do not suggest a general decrease in any of the species. Sallow and rowan saplings show low mortality in moose and deer dominated areas and the species can be characterised as rather resilient to browsing. Of more concern is that browsing can constrain the development of mature rowan and sallow trees locally, with possible consequences for associated epiphytic biodiversity.  相似文献   

4.
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.  相似文献   

5.
Aspen (Populus tremula L.) and rowan (Sorbus aucuparia L.) are important for biodiversity conservation and aesthetic reasons. Intensified levels of ungulate browsing the last decades have raised concerns over the recruitment of aspen and rowan in boreal forests. Demographic data are vital to understand and quantify how the structure of tree populations are affected over time by browsing and other factors but such data are rare. In a five-year study, we quantified vital demographic rates for co-occurring aspen and rowan using exclosures in a productive forest area in eastern-central Sweden. Mean annual browsing rate on small (<1 m) aspen and rowan stems was 20 vs. 38%, whereas the order in browsing intensity was reversed for stems of medium (1–2 m) size (28 vs. 14%). Browsing had a clear negative effect on transition rate from small to medium size class in both species, but had a much smaller impact on transition rate from medium to large (2–3 m) size class. Residence time for small stems and regeneration rate was much higher in aspen than in rowan, but browsing did not affect these dynamics. Transition to ungulate safe height (>3 m) was reduced with a factor of two in rowan and four in aspen by browsing.  相似文献   

6.
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.  相似文献   

7.
Uneven-aged silver fir-European beech forest stands were studied to (1) analyse the dynamics of diameter structure and tree species composition in the past two centuries and (2) determine the impact of red deer on the regeneration and recruitment of silver fir. The study used current data on forest stands, archival data from old forest management plans for the period 1789–2004, and red deer harvesting records for the period 1907–2006. During the observation period, the silver fir population aged and silver fir and European beech alternated in dominance. The study revealed a strong impact of red deer on the composition and recruitment of tree regeneration, especially on silver fir regeneration. The drastic changes in red deer density (from extermination up to 5.8 animals km−2) and past forest management practices were apparently the main factors driving the population dynamics of silver fir (regeneration, recruitment, and diameter structure) in the study area during the past two centuries.  相似文献   

8.
Absence of, or poor, oak (Quercus spp.) regeneration is a problem in uneven-aged, mixed closed-canopy broadleaved forests. Browsing by ungulates on small trees may contribute to poor oak regeneration in such forests. This possibility was investigated in 25 Swedish stands, and browsing damage was analysed in relation to landscape and stand factors. The proportion of browsed small (<20 cm tall) oak seedlings and other seedlings was low, and apparently a minor mortality factor. For saplings (20–130 cm tall), accumulated browsing damage was generally higher on oak than on five major competing tree species: Fraxinus excelsior, Corylus avellana, Tilia cordata, Acer platanoides and Sorbus aucuparia. Leaf removal was rare in late summer, except for rowan. The amount of cover (shelter) for ungulates near plots was positively correlated with oak browsing intensity; within plots, a high density of ash saplings may reduce browsing on oak saplings. In these forests, browsing probably retards growth of oak saplings relative to competing trees. Oak may persist as a minor stand component, but monitoring is needed to study future changes.  相似文献   

9.
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.  相似文献   

10.
Investigation of gap characteristics and tree regeneration patternsis central for our understanding of forest dynamics. By integratingaerial photograph analyses and ground surveys, we provide astudy of long-term canopy gap dynamics and tree regenerationpatterns in a Hungarian beech forest reserve. We found (1) thatin spite of the overall increase of gap area during the investigated30-years (from 2.5 to 7.7 per cent), total gap area and averagegap size (40–93 m2) were remarkably similar to those foundin other temperate and tropical forests, (2) if the fate ofindividual gaps was followed, two to three times more intensivecanopy dynamics (gap creation, closure and expansion) couldbe recognized than simple change of gap area indicated, and(3) average seedling density was considered to be sufficientfor natural regeneration. However, it was apparent that recentincreased deer browsing had prevented establishment of youngertrees of 1–2 m in height, as taller saplings were recordedonly in old gaps. Our results not only provide useful informationon forest dynamics but can also contribute to understandingthe potential roles that small forest reserves can play in providingessential reference data for nature-based forest managementof this forest type.  相似文献   

11.

Understanding how species-specific disturbances affect the dynamics of mixed forests is becoming increasingly important due to rapidly changing disturbance regimes. This study estimated the effect of Norway spruce (Picea abies (L.) Karst.) mortality on the disturbance processes in two mixed beech stands of the Western Carpathians that were affected by a bark beetle outbreak. We evaluated the size distribution, fraction of canopy and expanded gaps, the characteristics of gapmakers and the contribution of different species to gap size. The measured canopy gap fraction was <5%, and most canopy gaps were small (<100 m2). Spruce was the most abundant gapmaker, and its share among gapmakers was 3–6 times higher than its share in the canopy. We found that the increase in spruce mortality due to the outbreak resulted in a fine-scale mortality pattern. However, spruce gapmakers did not contribute much to gap area size, as shown by a weak correlation between the number of spruce gapmakers and the area of expanded gaps. Diameter distribution of living versus recently dead trees showed that beech mortality occurred disproportionately in large size classes. However, dead spruce trees were equally frequent in all diameter classes, which means beetles did not exclusively attack larger trees in these stands during the outbreak. We conclude that spruce mortality may have influenced successional processes by giving a competitive advantage to two other species that were not affected by the outbreak, provided that a high deer browsing intensity does not hinder the regeneration of new seedlings.

  相似文献   

12.
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.  相似文献   

13.
As a result of diverse management policies, densities of red and roe deer have varied considerably for the last few decades in Europe. Their selective browsing on woody species can modify the interactions between competing species and thus change overall patterns of plant diversity in forests. However, no classification of woody species according to browsing by deer yet exists in Europe. The selectivity index, which measures the balance between availability and consumption of plant species by herbivores, could be used for such a classification. The aim of this study was, first, to rank woody species according to this selectivity index, then to test whether their rank changed when browsing pressure varied in space or time. We also explored morphological and ecological life traits (Ellenberg indicator values) that might explain differences in selectivity.In 2006, we re-sampled a network of 217 coupled floristic and browsing survey plots, which had been previously described twice (1976, 1981). The plots were located in the forest of Arc-en-Barrois (France), a large woodland area divided into a North and a South Forest which have had different histories of browsing pressure.For the three samples and the two forests, we calculated a selectivity index for 19 woody species. Dogwood (Cornus sp.) and field rose (Rosa arvensis) appeared to be the most selected species whereas beech (Fagus sylvatica), common mezereon (Daphne mezereum) and wild-service tree (Sorbus torminalis) were always avoided. The rank order of species according to their selectivity index remained stable over the three sample years and between the two forests (Spearman's rank correlations: ρ ≈ 0.8 spatially, and range from 0.3 to 0.8 temporally). This indicates that variations in browsing pressure did not strongly modify deer selectivity patterns. Selectivity was positively correlated with wood density and negatively correlated with maximum height of the species, but unrelated to other plant traits. Finally, selectivity can be seen as an intrinsic characteristic of those woody species, and could be used as an additional life trait when analyzing vegetation communities.  相似文献   

14.
Fire history and stand structure was examined in twelve virgin forest stands situated within forest reserves in northern Sweden. The selected stands represented fire refuges as well as different successional stages after fire. Six of the stands were dominated by Norway spruce (Picea abies L. Karst.), three were dominated by Scots pine (Pinus sylvestris L.), and three were dominated by hairy birch (Betula pubescens Ehrh.) or aspen (Populus tremula L.). In 3 of the southernmost stands, the average fire interval was 34 to 65 years during the late 1600s to late 1800s, but since 1888 no fires had occurred in any of the stands. The absence of fire disturbance since 1888 is probably caused by the fire suppression in the overall landscape. The standing volume of living trees ranged between 87 and 511 m3 ha−1 while the volume of dead trees, including both snags and logs, ranged between 27 and 201 m3 ha−1. The volume of dead trees constituted ca. 30% of the total stem volume. In the conifer dominated stands, there was a statistically significant relationship between total stem volume, including both living and dead trees, and site productivity. A comparison between the amount of dead and living trees indicated substantial changes in tree species composition in several stands. It is suggested that data on the amount of dead trees, especially logs, and its distribution over decay classes could be used to examine the continuity of certain tree species. All stands had a multi-sized tree diameter distribution, which in most cases was similar to a reversed J-shaped distribution. In general spruce was numerous in the seedling cohort and in small diameter classes, indicating that its proportion in the stands was stable, or was increasing at the expense of pioneer tree species such as pine, aspen and silver birch (Betula pendula Roth.). The most numerous species in the seedling cohort, rowan (Sorbus aucuparia L.), was almost totally missing in the tree layer, indicating a high browsing pressure preventing rowan seedlings from growing into trees. The general increase of spruce and the sparse regeneration of pioneer species, in the stands previously affected by fire, are discussed in relation to natural disturbance regimes, biological diversity and nature conservation policies. It is proposed that reintroduction of fire disturbance is a necessity for future management plans of forest reserves. Other management practices to increase species diversity within forest reserves are also discussed.  相似文献   

15.
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.  相似文献   

16.
Bergquist  Jonas  Örlander  Göran  Nilsson  Urban 《New Forests》2003,25(1):25-40
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.  相似文献   

17.
Natural regeneration of windthrow areas is an important issue when planning forestry measures after forest disturbances. Seedling recruitment was investigated in storm-damaged hemiboreal mixed forests in eastern Estonia. The establishment and growth of seedlings from natural regeneration was registered for tree species in soil pits and in mounds of uprooted trees in stands that were either heavily or moderately damaged. Seedling growth is expected to be better in large but shallow soil pits created by uprooted Norway spruce [Picea abies (L.) Karst.] and poorer in small but deep pits created by the hardwoods in the area, silver birch (Betula pendula Roth.) and European aspen (Populus tremula L.). The most abundant regenerating species was birch. Pits hosted larger seedling numbers than mounds, due to soil instability in mounds. Rowan (Sorbus aucuparia L.) showed significantly faster growth than the other seedling species. Norway spruce pits were preferred to pits of other species by both birch and spruce seedlings. Black alder [Alnus glutinosa (L.) J. Gaertn.] did not show a preference for pits of a certain species of uprooted tree. Both spruce and rowan preferred hardwood mounds over spruce mounds. Storm severity also affected species composition: birch predominantly occurred on pits and mounds in heavily disturbed areas, while spruce was more abundant in the moderately damaged areas. The effects of advance regeneration and surrounding stands on seedling microsite preferences should be considered in future research and subsequent management recommendations.  相似文献   

18.
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.  相似文献   

19.
Taking advantage of the introduction of the black-tailed deer to the Queen Charlotte Islands (British Columbia, Canada), we used dendrochronological analyses to understand the consequences of deer browsing on Sitka spruce growth. We compared shape, radial growth, height growth and age of young spruce in three sites. We identified two types of trees growing side by side: (1) stunted and heavily browsed spruce, smaller than the browsing limit and (2) escaped spruce that were taller than the browsing limit but still browsed in their lower part. The compact and heavily ramified shape in stunted spruce was the result of repeated and intense browsing. In escaped spruce this was also the case below the browsing limit (1.16 m±0.07 m), in sharp contrast with the normal shape that escaped spruce resumed above the browsing limit. We show that the release of browsing pressure, once the tree reaches the browsing limit, is characterised by an abrupt increase in radial growth. Before release, trees show a growth stagnation characterized by narrow rings (0.5 mm per year) and small annual height increments (<5 cm per year). After release, trees show a growth stabilisation characterised by wider rings (3 mm per year) and larger annual height increments (20 cm per year). We use this pattern to estimate frequency and age at release and their possible variation over time. Age differences between stunted and escaped spruce are highly significant and indicate that, despite of browsing, most if not all trees will ultimately reach the browsing limit and escape. Heavy deer pressure (30 deer per km2) delays spruce sapling recruitment by about 8 years. This delay varies in relation to site quality and seems to have increased over time, suggesting an increase in browsing pressure.  相似文献   

20.
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