Effects of species and environmental factors on browsing frequency of young trees in mountain forests affected by natural disturbances
Introduction
The browsing of young trees by ungulate herbivores is a widespread phenomenon, affecting tree regeneration in most forests of the temperate zone (Ammer, 1996, Rooney, 2001, Takatsuki, 2009, Côté et al., 2004, Russell et al., 2017). It is considered one of the main driving forces in forest dynamics (Bradshaw et al., 2003, Didion et al., 2009, Herrero et al., 2016) and it plays a major role both in natural forests (Kuijper et al., 2010, Beschta and Ripple, 2016) and managed stands with various management intensities (Klopčič et al., 2010, Kupferschmid et al., 2013, Pendergast et al., 2016, Boulanger et al., 2018). With growing deer populations, the intensity of browsing increases, making the natural regeneration of some highly palatable species very difficult (Kupferschmid and Bugmann, 2005, Boulanger et al., 2009, Ramirez et al., 2018).
Browsing pressure is uneven at both local and landscape spatial scales. Wild ungulates prefer some plant species more than others, and therefore tree species can be browsed selectively (Boulanger et al., 2009, Kupferschmid, 2018). The strength of ungulate pressure upon certain tree species varies geographically, depending strongly on the local composition of tree stands and forage availability (Tripler et al., 2005, Boulanger et al., 2009, Gerhardt et al., 2013). In Central-European temperate forests, silver fir (Abies alba), sycamore maple (Acer pseudoplatanus) and oaks (Quercus spp.) are among the most preferred by wild ungulates, while Norway spruce (Picea abies) and European beech (Fagus sylvatica) are usually avoided (Senn and Suter, 2003, Götmark et al., 2005, Boulanger et al., 2009, Didion et al., 2009, Klopčič et al., 2010, Nagel et al., 2015). Locally, ground vegetation and management practices may affect browsing habits of wild ungulates (Partl et al., 2002, Bakker et al., 2004, Rammig et al., 2007, Ewald et al., 2014, Möst et al., 2015).
Although numerous studies have shown that the amount of forage was probably the most important factor determining browsing intensity (Russell et al., 2017), landscape-scale factors matter, including surrounding land cover types, management activities, vegetation structure and preferences of wild browsers in terms of habitat and food sources (Sabo, 2019). Analyses of the browsing behaviours of most important European wild ungulates revealed their preferences for browsing in gaps rather than in closed forests (Kuijper et al., 2009, Tahtinen et al., 2014). The amount of open spaces, forest edges and fields with palatable crops in the surrounding landscape is also positively correlated with the browsing activity of wild ungulates in forests (Staines and Welch, 1984, Tufto et al., 1996, Nagel et al., 2015). Proximity to roads and trails significantly reduces browsing by wild herbivores (Möst et al., 2015). Some studies also reported relationships between browsing pressure and topography, including elevation, slope and aspect (Mysterud et al., 2010; Heurich at al., 2015), snow cover (Månsson, 2009) as well as habitat productivity and habitat type (Mysterud et al., 2010). However, relationships between all the above-mentioned factors and the habits of wild browsers may be even more complex. Whether the effects of some of these factors are strong or modest, it will depend mainly on the ungulate densities (Ward et al., 2008, Möst et al., 2015). The relationship between the ungulate density and browsing is not a linear one (Tremblay et al. 2007).
Browsing pressure is of vital importance for both forest management and biodiversity conservation, and therefore great insights into the relationships between forest ecosystems and wild ungulates have been gained. Most studies on browsing pressure are usually focused on undisturbed forest ecosystems affected by high levels of ungulate densities. However, large intensity disturbances can dramatically change the availability of resources and vegetation structures, and therefore usually affect the behaviour of wild ungulates (Widmer et al., 2004). For example, a large number of fallen logs after natural disturbances decrease the browsing intensity as the area is less available for browsing herbivores and there is an increasing risk of predation (Rammig et al., 2007, Hagge et al., 2019, Whyte and Lusk, 2019). The presence of large tip-up windthrow mounds may decrease the ungulate browsing pressures and provide good conditions for regeneration of palatable species (Long et al., 1998, Krueger and Peterson, 2006). In addition, rapid forest regeneration following some large-scale disturbances results in an enormous increase in the available forage (Rammig et al., 2007, Pajtík et al., 2015), which can potentially affect previously recognized browsing behaviour.
The aim of this study was to analyse the patterns of browsing pressure in the Tatra Mts. (southern Poland) after large scale intense disturbances. Specifically, we aimed to answer the following questions:
- (1)
Do the effects of natural disturbances change the already known preferences of ungulate herbivores towards certain species and size classes of young trees?
- (2)
Is the browsing frequency influenced more by the effects of recent disturbances on stand structure than by the environmental factors, like elevation, solar radiation, bedrock and soil type?
- (3)
Do the landscape-scale effects of natural disturbances modify the influence of human pressure on the browsing patterns of ungulate herbivores?
Section snippets
Study area
The research was carried out in the Tatra National Park (TNP) covering an area of 21,197 ha. The TNP covers the entire area of the Polish Tatra Mountains, which in the southern part borders the Slovak Tatra National Park. Depending on the location, the bedrock consists of two distinct various rocks formations; limestones and dolomites in the northern part, ans. gneisses and granites in the south. The climate in the lower mountain zone is moderately cool, with an annual temperature up to 5 °C
Differences in browsing pressure among tree species
Of the 40,707 young trees recorded in sample plots, 5193 individuals (12.8%) showed signs of herbivore browsing. The percentage of young trees that had been browsed by ungulates varied from 6.8% in seedlings, through 11.6% in tall saplings to 21.2% in short saplings. The browsing pressure was very unevenly distributed among the tree species. Among the seedlings, extremely high levels of browsing were recorded in the case of species represented by only a few individuals; therefore, in the
Differences in browsing pressure among species and size classes
Wild herbivores have specific preferences with regards to their forage and therefore exert a higher browsing pressure on some tree species than on other species. Large differences in browsing pressure upon various tree species have been frequently documented in the literature (Motta, 2003, Boulanger et al., 2009, Čermák et al., 2009, Klopčič et al., 2010). In this study, we partially corroborated the previous findings of other authors. In the Tatra Mts., rowan is the most heavily browsed
Conclusion
Browsing pressure in the Tatra N.P. is strongly concentrated upon the shorter saplings of the highly palatable species, especially rowan and sycamore maple. It is highly variable among the sample plots, and these differences cannot be explained by environmental factors, like elevation, slope, geology or soil type. Canopy tree mortality contributes to increased levels of browsing, mostly due to the larger amount of young trees under partly open forest canopies. However, because of the ample
CRediT authorship contribution statement
Jerzy Szwagrzyk: Conceptualization, Funding acquisition, Methodology, Project administration, Writing - original draft, Writing - review & editing. Anna Gazda: Data curation, Formal analysis, Funding acquisition, Methodology, Writing - original draft, Writing - review & editing. Elżbieta Muter: Writing - review & editing. Remigiusz Pielech: Formal analysis, Methodology, Writing - original draft, Writing - review & editing. Janusz Szewczyk: Data curation, Writing - original draft, Writing -
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
This research was financially supported by the Polish National Science Foundation (NCN) grant No. 2018/31/B/NZ8/02786 (project title: “How do large-scale disturbances influence the relationship between ungulate herbivory and natural regeneration in temperate forests?”), Ministry of Science and Higher Education of the Republic of Poland in frame of statutory activities SUB/040011-D019/2020 of Department of Forest Biodiversity, University of Agriculture in Krakow and by “Forest Found” (resources
References (85)
- et al.
Herbivory and seedling establishment in Pyrenean forests: Influence of micro- and meso-habitat factors on browsing pressure
For. Ecol. Manage.
(2015) Impact of ungulates on structure and dynamics of natural regeneration in mixed mountain forests in the Bavarian Alps
For. Ecol. Manage.
(1996)- et al.
Deer browsing promotes Norway spruce at the expense of silver fir in the forest regeneration phase
For. Ecol. Manage.
(2017) - et al.
Riparian vegetation recovery in Yellowstone: the first two decades after wolf reintroduction
Biol. Conserv.
(2016) - et al.
High density of keystone herbivore vs. conservation of natural resources: Factors affecting red deer distribution and impact on vegetation in Słowiński National Park, Poland
For. Ecol. Manage.
(2019) - et al.
Ranking temperate woody species along a gradient of browsing by deer
For. Ecol. Manage.
(2009) - et al.
A long-term perspective on ungulate–vegetation interactions
For. Ecol. Manage.
(2003) - et al.
Disturbance and structural development of natural forest ecosystems with silvicultural implications, using Douglas-fir forests as an example
For. Ecol. Manage.
(2002) - et al.
Determinants of deer impact in European forests – A systematic literature analysis
For. Ecol. Manage.
(2013) - et al.
Deadwood retention in forests lowers short-term browsing pressure on silver fir saplings by overabundant deer
For. Ecol. Manage.
(2019)
Intensity of red deer browsing on young rowans differs between freshly-felled and standing individuals
For. Ecol. Manage.
Do ungulates preferentially feed in forest gaps in European temperate forests?
For. Ecol. Manage.
Selective browsing behaviour of ungulates influences the growth of Abies alba differently depending on forest type
For. Ecol. Manage.
Effects of microsites, logs and ungulate browsing on Picea abies regeneration in a mountain forest
For. Ecol. Manage.
Browsing regime and growth response of naturally regenerated Abies alba saplings along light gradients
For. Ecol. Manage.
Creating a landscape of management: unintended effects on the variation of browsing pressure in a national park
For. Ecol. Manage.
Ungulate impact on rowan (Sorbus aucuparia L.) and Norway spruce (Picea abies (L.) Karst.) height structure in mountain forests in the eastern Italian Alps
For. Ecol. Manage.
Forest restoration and browsing impact by roe deer
For. Ecol. Manage.
Impact of deer on temperate forest vegetation and woody debris as protection of forest regeneration against browsing
For. Ecol. Manage.
Wind disturbance in mountain forests: Simulating the impact of management strategies, seed supply, and ungulate browsing on forest succession
For. Eco. Manage.
Effects of wild ungulates on the regeneration, structure and functioning of temperate forests: a semi-quantitative review
For. Ecol. Manage.
Interactions between white-tailed deer density and the composition of forest understories in the northern United States
For. Ecol. Manage.
Ungulate browsing on silver fir (Abies alba) in the Swiss Alps: beliefs in search of supporting data
For. Ecol. Manage.
Coarse woody debris facilitates oak recruitment in Białowieża Primeval Forest, Poland
For. Ecol. Manage.
Influence of hurricane Lothar on red and roe deer winter diets in the Northern Vosges, France
For. Ecol. Manage.
Effects of sika deer on vegetation in Japan: A review
Biol. Conserv.
The blame game: Using eDNA to identify species-specific tree browsing by red deer (Cervus elaphus) and roe deer (Capreolus capreolus) in a temperate forest
For. Ecol. Manage.
Conifer leader browsing by roe deer in English upland forests: effects of deer density and understorey vegetation
For. Ecol. Manage.
Woody debris in treefall gaps shelters palatable plant species from deer browsing, in an old-growth temperate forest
For. Ecol. Manage.
The effects of hurricane Lothar on habitat use of roe deer
For. Ecol. Manage.
Ecological anachronisms in the recruitment of temperate light-demanding tree species in wooded pastures
J. Appl. Ecol.
The structure of forest stands in the Tatra National Park: the results of 2016–2017 inventory
For. Res. Papers
Ungulates increase forest plant species richness to the benefit of non-forest specialists
Glob. Change Biol.
glmmTMB balances speed and flexibility among packages for zero-inflated generalized linear mixed modeling
R J.
Odnowienie naturalne drzew w Puszczy Białowieskiej
Sylwan
Clarification of a technique for analysis of utilization-availability data
J. Wildl. Manage.
Relationships between browsing damage and woody species dominance
J. For. Sci.
Ecological impacts of deer overabundance
Ann. Rev. Ecol. Evol. Syst.
Long-term effects of ungulate browsing on forest composition and structure
For. Ecol. Manage.
Effects of ungulate browsing on recruitment of aspen and rowan: a demographic approach
Scand. J. For. Res.
Estimating the distribution of forage mass for ungulates from vegetation plots in Bavarian Forest National Park
Tuexenia
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