No difference in plant species diversity between

Forest Ecology and Management 430 (2018) 587–593

Contents lists available at ScienceDirect

Forest Ecology and Management journal homepage: www.elsevier.com/locate/foreco

No difference in plant species diversity between protected and managed ravine forests

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Jakub Baran, Remigiusz Pielech , Jan Bodziarczyk Department of Forest Biodiversity, Faculty of Forestry, University of Agriculture in Krakow, 29 Listopada 46, 31-425 Kraków, Poland

A R T I C LE I N FO

A B S T R A C T

Keywords: Forest management Forest protection Hart's-Tongue fern Phyllitis scolopendrium Ravine forest Tilio-Acerion Sycamore maple forest

The influence of management practices on forest ecosystems is usually analyzed by a comparison of species composition and richness. Different types of management practices increase plant species richness, mainly due to an increase in the number of ruderal and open habitat species. So far, most of the studies have been performed in the forest types that were most common in the studied regions. In this study we focused on broadleaved ravine forests that are spatially limited to specific habitat conditions, including steep rocky slopes with skeletal soil and unstable ground. These forests are local biodiversity hotspots, and, due to limited accessibility, have been subject to only limited management practices, mainly removal of single trees. We collected a dataset of 215 plots sampled between 1991 and 2015 in both managed forests and protected areas. We used multivariate techniques to compare the differences in the overall species composition. In addition, we compared differences in diversity, structural and habitat indices to find any possible differences. There were no differences in both the plot level and accumulative species richness and diversity indices between protected and managed forests. In addition, a comparison of habitat conditions and different ecological groups, including ruderal and open habitat species, alien species and ancient forest indicator species also revealed no differences. The only significant differences between the protected and managed forests related to the evenness and shrub cover. We concluded that low intensity forest management in ravine forests resembles natural disturbances, which are characteristic of natural ravine forests. The species composing these communities are adapted to frequent natural disturbances and thus forest management did not influence significant habitat conditions. However, to fully understand the effect of these practices on biodiversity, a comparison of structural characteristics is needed.

1. Introduction During the last millennia, the vast majority of forests in Europe were heavily changed by human activity (Christensen and Emborg, 1996; Kalis et al., 2003; Sabatini et al., 2018). Except for the obvious management activities, like clearing of forests for agricultural and industrial purposes, forest management also affects natural processes (Bengtsson et al., 2000). Different types of management activities influence forest ecosystems by changing the forest stand structure (Kuuluvainen et al., 1996; Commarmot et al., 2005; Wesely et al., 2018), species composition (Okland et al., 2003; Nagaike et al., 2005; Sebastià et al., 2005; Durak, 2012; Horvat et al., 2017a; Kaufmann et al., 2017), soil properties (Carlson and Groot, 1997; Thiffault et al., 2011; Gross et al., 2018; Kovács et al., 2018) or local microclimate (Chen et al., 1999; Daolan et al., 2000; Frey et al., 2016). In addition, forest management influence the availability of particular ecological niches by affecting the

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presence of coarse woody debris, pits and mounds after natural disturbances or giant trees (Peterson et al., 1990; Nilsson and Baranowski, 1997; Bobiec, 1998; Christensen et al., 2005; Ódor et al., 2006). It is generally believed that unmanaged forests under strict protection in national parks and nature reserves promote biodiversity and host more species than managed forests. Many studies, however, showed that the relationships between forest management and biodiversity are very complex. The effect of forest management activities depends largely on the type and magnitude (Halpern and Spies, 1995). For example, clear-cutting has a different effect on forest biodiversity than shelterwood lodging or coppicing (Nagaike et al., 2005). In addition, the time since management was abandoned can have significant effects on species diversity in unmanaged forests, because the forest condition and structure change over time (Fenton and Bergeron, 2008; Horvat et al., 2017a; Horvat et al., 2017b). Interestingly, recent reviews have revealed that different components of the biodiversity may

Corresponding author. E-mail address: [email protected] (R. Pielech).

https://doi.org/10.1016/j.foreco.2018.08.052 Received 21 July 2018; Received in revised form 28 August 2018; Accepted 30 August 2018 0378-1127/ © 2018 Elsevier B.V. All rights reserved.


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species characteristic of open habitats.

respond both positively and negatively to forest management intensity and time since abandonment (Paillet et al., 2010; Biber et al., 2015; Dieler et al., 2017). Organisms that mainly depend on deadwood, forest cover continuity and presence of large trees, including bryophytes, lichens, fungi and saproxylic beetles, were negatively affected by forest management. On the contrary, the diversity of vascular plants was usually higher in managed forests. Understanding these effects coupled with a growing awareness of the important role of natural resources has fundamentally changed management practices over the last decades. Methods emulating natural processes, like natural disturbances or saving coarse woody debris, are gaining popularity among forest managers and are replacing harmful clear-cuttings (Christensen and Emborg, 1996; Angelstam, 1998; Bengtsson et al., 2000; Firm et al., 2009; Long, 2009). Organisms that mainly depend on deadwood, forest cover continuity and presence of large trees, including bryophytes, lichens, fungi and saproxylic beetles, were negatively affected by forest management. On the contrary, the diversity of vascular plants was usually higher in managed forests. Understanding these effects coupled with a growing awareness of the important role of natural resources has fundamentally changed management practices over the last decades. Methods emulating natural processes, like natural disturbances or saving coarse woody debris, are gaining popularity among forest managers and are replacing harmful clear-cuttings (Christensen and Emborg, 1996; Angelstam, 1998; Bengtsson et al., 2000; Firm et al., 2009; Long, 2009). Although previous research has gained great insights into the effect of forest management on biodiversity, more comparative studies are needed instead of purely descriptive ones (Paillet et al., 2010). In addition, these comparisons should be based on more comprehensive and insightful measures than just on species richness. For example, a vast number of studies have shown higher plant species richness in managed forests compared to unmanaged forests (Graae and Heskjær, 1997; Nagaike et al., 2005; Schmidt, 2005; Paillet et al., 2010; Horvat et al., 2017a; Kaufmann et al., 2017). However, a simple number of species recorded per plot is not always a good measure of the conservation status of forest stand. For example, Brunet et al. (1996) showed that species richness in the herb layer increased with management intensity mainly due to the establishment of ruderal species from the seed bank, while species richness of typical forest flora remained unaffected by the management. Most of the studies were performed in forest types that predominate in particular regions. In Europe, this includes mainly beech and mixed beech-fir forests, oak and oak-hornbeam forests and mountain spruce forests. The effect of forest management on biodiversity in forest types that are characteristic of more specific habitat conditions have not been well studied. In this study, we focused on communities of broadleaved ravine forests that are spatially limited to specific habitat conditions, including steep rocky slopes with skeletal soil and unstable ground. Ravine forests play an important role as biodiversity hotspots and contribute to the protection of the soil and water resources. A survey conducted in France proved that sycamore ravine forests have higher ecological value than the surrounding mixed forest (Paillet et al., 2008). Due to high biodiversity and limited economic value, most stands of ravine forest were subject to extensive management or remained unmanaged (Paillet et al., 2008). Ravine forests are a subject of frequent natural disturbances due to being located on unstable ground on steep slopes, and thus constitute a very interesting study system. We hypothesized that the low intensity forest management that was commonplace until recently outside protected areas had an effect similar to natural disturbances of low to moderate magnitudes. To test this hypothesis, we selected a dataset of 215 plots sampled in both managed and protected forests and tested these two groups for significant differences in species composition. In addition, we compared numerous characteristics related to species richness, including diversity and evenness indices, species richness, cover of tree, shrub and herb layers as well as the contribution of alien species, ancient forest indicator species and

2. Material and methods 2.1. Study object and vegetation database As an object of the study, we selected broadleaved forests dominated by species of maples (Acer pseudoplatanus, A. platanoides) and other ‘noble’ forest trees with Hart's-Tongue fern (Phyllitis scolopendrium) occurring in the herb layer. This specific type of forest is characterized by a narrow ecological niche and it grows on steep slopes and ravines with north-west to east aspects on calcareous screes with shallow soils (Ellenberg, 2009). This forest community type has been recognized as a Phyllitido-Aceretum pseudoplatanii Moor 1952 association (Clot, 1990; Matuszkiewicz, 2001). At present, most of the maple forest stands are protected as a priority habitat type Natura 2000 (code 9180). Until recently, however, many of these forest stands were localized outside protected areas and could have been managed with different intensity. As an extreme case, a clear cut in a ravine forest stand was documented at the beginning of the 2000s to obtain a better landscape view and to make the rocks available for climbing (Bodziarczyk and Malik, 2006). Almost all stands of this type of forest in Poland were sampled during a detailed study on the ecology of Phyllitis scolopendrium (Bodziarczyk, 2012). This resulted in detailed phytosociological descriptions of more than 500 plots sampled by one person, which were thus free from observer bias. These phytosociological relevés are stored in the Forest Database of Southern Poland (Pielech et al., 2018). As some research has clearly shown that comparing species diversity of vascular plants between protected and managed forests is trustworthy only when the site conditions are the same (Graae and Heskjær, 1997; Schmidt, 2005), we tried to ensure high homogeneity in our dataset in terms of environmental conditions. First, as mentioned above, our studied forest type has a very narrow ecological niche. Second, to eliminate possible differences within a broad geographical range, we limited the further analyses to one geographical mesoregion, which was the Carpathians. We used the following criteria for selecting vegetation data from the database: (i) locality in the Carpathians; (ii) cover of tree or shrub layers higher than 50% and (iii) occurrence of Phyllitis scolopendrium. As a result, we obtained a subset of 215 forest plots, including 83 plots localized within protected areas (national parks and nature reserves) and 132 plots localized in managed forests (both private and managed by Polish State Forests) (see Fig. 1). The comparison of these two subsets revealed no significant differences in terms of slope and aspect (t-test: t = 0.708, p = 0.479 and t = 0.663, p-value = 0.508, respectively); however, we identified significant differences in elevation (ttest: t = −4.152, p = 0.00005). The samples from protected areas were located at higher elevations than the samples from managed forests (at 600.3 and 517.5 m a.s.l., respectively; see Table 1). This pattern reflects the history of forest management within the studied area; in general, forest stands at lower elevations could be easily accessed and were more affected by human pressure. As a result, national parks and nature reserves were established at higher elevations to protect the most preserved forests. Nevertheless, we found that the difference in the mean altitudes was lower than 100 m and so does not affect the meaningfulness of our comparison, and thus can be neglected. All the plots were sampled within the large study area and the protected areas are very diverse in terms of their history. For that reason, for the plots located in protected areas we calculated how many years had passed since the establishment of the protection to the date of vegetation sampling. Based on these data, we estimated that – on average – these plots have been unmanaged for about five decades. This includes, however, plots unmanaged for more than eight decades as well as several plots from protected areas that were established less than two decades before the sampling occured. 588


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Fig. 1. Distribution of sample plots in Central-European and regional (Polish part of Carpathians) contexts.

Ellenberg’s Indicator Values (EIVs) to compare habitat conditions between both protected and not protected ravine forests. EIVs reflect the habitat preferences of Central-European vascular plants by placing them on defined 9–12-point ordinal scales for seven environmental variables, including soil moisture, pH, nutrients, light, temperature, continentality and salinity (Ellenberg et al., 1992). The EIVs are broadly used in applied ecology (Diekmann, 2003; Pielech et al., 2017). In this study we calculated community weighted means for light, moisture, reaction, temperature and nutrients for each plot. We used t-tests to compare structural and compositional indices and modified permutation tests to compare mean EIVs (Zelený and Schaffers, 2012). All statistical analyses were performed and graphically presented in R (R Core Team (2018)) with ‘vegan’ (Oksanen et al., 2018) and ‘ggplot2′ (Wickham, 2009) packages.

2.2. Data processing and analyses First, we used Nonmetric Multidimensional Scaling (NMDS) with the vegan::metaMDS() function (Oksanen et al., 2018) to examine the overall differences in species composition between protected and not protected ravine forests. As both groups partially overlapped in ordinal space, we then tested these differences for significance using the vegan::anosim() function. Second, we compared species richness between protected and not protected ravine forests both at the plot level and as cumulative richness. At the plot level, we used t-tests to compare separate plots of different sizes, including 100, 200 and 400 m2. To compare cumulative species richness, we used the vegan::specacum() function. Third, we compared different structural and compositional indices, including covers of trees, shrubs and herbs; Simpson and Shannon diversity and evenness; as well as the contribution of alien species, ancient forest indicator species and species characteristic of open habitats. We used the list compiled by Tokarska-Guzik et al. (2014) for alien species and the list by Dzwonko and Loster (2001) for ancient forest indicator species. For open habitat species indicators we used the phytosociological concept of characteristic species, proposed by Mucina et al. (2016), including species of perennial ruderal communities (Artemisietea vulgaris class) and species of pastures, meadows and tall-herb fringes (Molinio-Arrhenatheretea class). We selected those two phytosociological classes as many species that are typical of these vegetation types also occur with a high frequency in forest communities, indicating some disturbances resulting in canopy openness and a high amount of light reaching the forest floor. Finally, we used

3. Results The Nonmetric Multidimensional Scaling revealed a strong overlap within two-dimensional space (Fig. 2). Samples representing protected and not-protected ravine forests were no clearly separated, which suggest only small differences in species composition. Analysis of similarity (ANOSIM) suggested an even distribution of the ranked dissimilarities between the two analysed groups (R = 0.057, p = 0.002). The comparison of the plot-level species richness for 100, 200 and 400 m2 sizes did not reveal any differences between the protected and not protected forests (Table 2). Similarly, analysis of cumulative species richness did not show any significant differences in species richness

Table 1 Basic statistics regarding dataset used in this study.

Not protected Protected

Number of plots

Years of sampling

Plot size [m2] min–max (mean/SD)

Altitude [m] min–max (mean/SD)

Aspect [°] min–max (mean/ SD)

Slope [°] min–max (mean/ SD)

132 83

1996–2015 1991–2015

100–400 (231.8/112.3) 100–400 (213.2/111.3)

210–880 (517.5/143.1) 345–1100 (600.3/141.7)

23–360 (185.9/135.0) 23–360 (173.9/124.9)

10–70 (35.8/8.9) 10–70 (35.2/9.5)

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Fig. 2. Comparison of species composition between protected and not protected ravine forests in two-dimensional NMDS space.

affect plant species composition when compared to either intact forests or forests abandoned for at least a few decades (Graae and Heskjær, 1997; Nagaike et al., 2005; Schmidt, 2005; Paillet et al., 2010; Horvat et al., 2017a; Kaufmann et al., 2017). Forest management usually leads to an increase in plant species richness. Especially, ruderal species or species of open habitats are the ones responsible for that increased richness (Brunet et al., 1996). Thus, species richness as well as diversity and evenness indices are often used to describe human influence on forests in comparisons between managed and unmanaged stands (Pitkänen, 1998; Onaindia et al., 2004). In our study we compared the species richness both at the plot level (separately for each size) and as cumulative richness. Both approaches revealed that there were no significant differences in species richness between managed and protected ravine forests. What is more, we did not detect any differences in Shannon and Simpson diversity indices between protected and unprotected forests. The only significant difference was detected for the evenness index, which was slightly higher in managed forests suggesting more evenly distributed abundances. Some possible explanations could include disturbances of different types (both natural and anthropogenic) being more frequent in managed forests and prevent more competitive species from predominating. However, the detected differences in evenness were in fact close to the fixed significance level (P = 0.05) and together with the lack of significant difference in the other indices, they are not very convincing in terms of the analysed management influences. It has been shown that forest management can affect particular ecological groups of plants. For example, plants susceptible to disturbances driven by forest management or shadow demanding species may be eliminated from forests as a result of management activities (Falkengren-Grerup and Tyler, 1991; Halpern and Spies, 1995). The loss in the number of species might be compensated for by an increase in the number of species in other ecological groups, e.g., ruderal or

Table 2 Comparison of species richness, cover of trees, shrubs and herbs layers, Simpson and Shannon diversity and evenness, as well as contribution of alien species, ancient forest indicator species and species characteristic of open habitats. Forest characteristics

Species richness (n/100 m2) Species richness (n/200 m2) Species richness (n/400 m2) Cover of trees (%) Cover of shrubs (%) Cover of herbs (%) Shannon diversity index Simpson diversity index Evenness Species of open habitat (n/plot) Alien species (n/plot) Ancient forest indicator species (n/plot)

Protected

Not protected

Mean

SD

Mean

SD

34.0 35.4 37.4 75.3 21.8 77.6 2.74 0.88 0.77 0.5 0.2 19.7

9.9 10.1 10.2 18.4 15.1 16.8 0.36 0.05 0.06 0.8 0.4 5.4

32.0 37.4 38.6 70.4 26.9 77.6 2.81 0.89 0.79 0.7 0.2 20.4

7.6 10.6 10.6 22.4 19.3 19.6 0.33 0.04 0.05 1.2 0.4 6.0

p

0.392 0.356 0.693 0.087 0.031 0.983 0.126 0.059 0.039 0.067 0.836 0.376

between the two groups of ravine forests (Fig. 3). We found significant differences in shrub covers but no significant differences in the cover of trees and herbs. No differences were found in the diversity indices (except for evenness), number of ancient forest indicator species, alien species and open habitat indicators (Table 2). In addition, the comparison of EIVs showed no differences in community weighted means for five analysed indices (Table 3). 4. Discussion 4.1. Species composition in managed and protected ravine forests Numerous studies have shown that forest management practices 590


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Fig. 3. Accumulation curves for not protected (a) and protected (b) ravine forests. Filled ellipses denote confidence intervals (0.95) and confidence intervals of second group (contour) are given as reference.

with forest continuity. There were no differences in the number of ancient forest indicator species in our study due to the low to medium intensity forest management in the ravine forests not breaking the forest continuity. In our study we also compared the number of alien plants between managed and protected forests. Previous studies showed that forest management favours alien species and the number of alien species is lower in protected areas when compared to unprotected forests (Chmura, 2004; Gallardo et al., 2017; Moustakas et al., 2018). In ravine forests, we detected no differences between protected and not protected forests. Alien species play a marginal role in the Carpathians’ ravine forests and none of them were recorded in most of the plots. One of the most widespread invasive species in Polish forests, Impatiens parviflora (Obidziński and Symonides, 2000; Chmura, 2004; Chmura and Sierka, 2007), was recorded only in four plots with limited abundance. This suggests that ravine forests even when subjected to human disturbances are to some extent resistant to plant invasions. No differences in the plant species composition and richness were somewhat surprising and we suggest that the best explanation is related to the specific habitat conditions in ravine forests, mainly the presence of natural disturbances, which are typical of this type of forest community. Natural disturbances caused by slope instability and rubble cover constitute an essential factor that shapes ravine forests (Bodziarczyk and Szwagrzyk, 1995; Bodziarczyk, 2002). These disturbances affect forest stands as well as ground cover and act as environmental filters. For that reason, the plants composing the community of ravine forests are adapted to frequent disturbances and the most typical plant species of the analysed forest type, Hart’s-tongue fern, can

Table 3 Comparison of community weighted means of EIVs for protected and not protected ravine forests using modified permutation test (Zelený and Schaffers, 2012) with 1000 iterations. EIVs

Light Temperature Moisture Reaction Nutrients

Protected

Not protected

Mean

SD

Mean

SD

3.8 5.0 5.5 6.8 6.3

0.4 0.3 0.2 0.4 0.6

3.9 5.1 5.5 6.8 6.3

0.4 0.2 0.2 0.4 0.4

F-value

p

0.001 0.086 0.012 0.067 0.616

0.981 0.783 0.920 0.811 0.457

open habitat species. For that reason, beside simple qualitative comparisons, we aimed to undertake comparisons of different ecological groups of species. According to our initial expectations, the cutting of single trees in managed forest – which was a common practice in managed ravine forests in the studied area – could change habitat conditions by increasing the amount of light reaching the forest floor and thus promoting species characteristic of open habitats. Surprisingly, we did not find any significant differences neither in the habitat conditions as expressed by EIVs nor in the number of species of open and ruderal habitats. Our results are consistent with previous studies on the functional response of forest floor vegetation to management. Graae and Sunde (2000) showed that there was no effect of forest management on the composition of plant traits. The authors, however, showed that traits typical of ancient forest indicator species were correlated 591


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relatively low economic value, ravine forests have hardly been subjected to any intensive management activities. According to ecological threshold theory, however, an increase in management treatment intensity may cause the ecological threshold (or breakpoint) to be crossed and then cause significant abrupt change in the community (Groffman et al., 2006). For example, at the beginning of the 2000s, excessive cutting of trees in ravine forests was done on Krakow-Czestochowa Upland and caused a decline in Hart’s-tongue fern (Bodziarczyk and Malik, 2006).

serve as an excellent example of these adaptations (Bodziarczyk, 2012). Low intensity forest management practices in unprotected ravine forests resemble natural disturbances and thus do not significantly change the plant species composition. Natural ravine forests are also characterised by low stand density due to a high number of broken or uprooted trees. Patches of bare mineral soil and overstory gaps are also common due to natural disturbances. In addition, ravine forests share more species with translucent crowns as compared to surrounding forests dominated by beech and fir. These features create conditions suitable for species with higher light demands (Bodziarczyk and Szwagrzyk, 1995; Brunet et al., 1996, 1997). Thus, single cuttings conducted in managed ravine forests did not substantially change the habitat conditions and no differences in the number of open habitat species were detected. In the presented study we investigated only vascular plant species. However, in ravine forests with highly diverse microhabitats, including stones, rocks, pits, mounds and fallen trees, an important part of the biodiversity is constituted by bryophytes and lichens. Both groups contain organisms that are sensitive to human alterations and are often used as indicators of forest management and ecosystem transformations (Hernández-Hernández et al., 2017; Kaufmann et al., 2017; Haughian, 2018; Tullus et al., 2018; Wierzcholska et al., 2018). Perhaps detailed studies on cryptogram diversity could give more information on the influence of low-intensity management practices on biodiversity in ravine forests.

Acknowledgements This study was financially supported by the Ministry of Science and Higher Education of The Republic of Poland in the frame of statutory funds: DS-3421/2017 Department of Forest Biodiversity, University of Agriculture in Krakow. In addition, the contribution by Remigiusz Pielech was also supported by a grant from the National Science Centre, Poland (2016/20/S/NZ8/00428). References Angelstam, P.K., 1998. Maintaining and restoring biodiversity in European boreal forests by developing natural disturbance regimes. J. Veg. Sci. 9, 593–602. Baran, J., Bodziarczyk, J., 2018. The structure of forest stands in Phyllitido-Aceretum community occurring on limestone rocks and shelves – growing in strictly protected areas and in managed forests. Pol. J. Ecol (submitted). Bengtsson, J., Nilsson, S.G., Franc, A., Menozzi, P., 2000. Biodiversity, disturbances, ecosystem function and management of European forests. For. Ecol. Manage. 132, 39–50. Biber, P., Borges, J., Moshammer, R., Barreiro, S., Botequim, B., Brodrechtová, Y., Brukas, V., Chirici, G., Cordero-Debets, R., Corrigan, E., Eriksson, L., Favero, M., Galev, E., Garcia-Gonzalo, J., Hengeveld, G., Kavaliauskas, M., Marchetti, M., Marques, S., Mozgeris, G., Navrátil, R., Nieuwenhuis, M., Orazio, C., Paligorov, I., Pettenella, D., Sedmák, R., Smreček, R., Stanislovaitis, A., Tomé, M., Trubins, R., Tuček, J., Vizzarri, M., Wallin, I., Pretzsch, H., Sallnäs, O., 2015. how sensitive are ecosystem services in European forest landscapes to silvicultural treatment? Forests 6, 1666. Bobiec, A., 1998. The mosaic diversity of field layer vegetation in the natural and exploited forests of Białowieża. Plant Ecol. 136 175 175. Bodziarczyk, J., 2002. Zróżnicowanie zespołu jaworzyny górskiej z języcznikiem Phyllitido-Aceretum w Polsce [Phytosociological differentiation of PhyllitidoAceretum community in Poland]. Fragm. Flor. Geobot. 9, 187–218. Bodziarczyk, J., 2012. Struktura i dynamika populacji języcznika zwyczajnego Phyllitis scolopendrium (L.) Newm. w Polsce [Structure and dynamics of populations of Hart's Tongue Phyllitis scolopendrium (L.) in Poland]. Wydawnictwo Uniwersytetu Rolniczego im. Hugona Kołłątaja w Krakowie. Bodziarczyk, J., Malik, R., 2006. Rozmieszczenie, warunki wystepowania i ocena liczebnosci populacji Phyllitis scolopendrium (Aspleniaceae) na Wyzynie KrakowskoCzestochowskiej: Distribution, habitat conditions and estimation of population size of the Hart’s tongue fern Phyllitis scolopendrium (Aspleniaceae) in the KrakówCzęstochowa Upland. Fragm. Flor. Geobot. 1, 155–170. Bodziarczyk, J., Szwagrzyk, J., 1995. Species composition and structure of forest stands in Phyllitido – Aceretum community. Pol. J. Ecol. 43, 153–173. Brunet, J., Falkengren-Grerup, U., Tyler, G., 1996. Herb layer vegetation of south Swedish beech and oak forests—effects of management and soil acidity during one decade. For. Ecol. Manage. 88, 259–272. Brunet, J., Falkengren-Grerup, U., Tyler, G., 1997. Pattern and dynamics of the ground vegetation in south Swedish Carpinus betulus forests: importance of soil chemistry and management. Ecography 20, 513–520. Burrascano, S., Keeton, W.S., Sabatini, F.M., Blasi, C., 2013. Commonality and variability in the structural attributes of moist temperate old-growth forests: a global review. For. Ecol. Manage. 291, 458–479. Carlson, D.W., Groot, A., 1997. Microclimate of clear-cut, forest interior, and small openings in trembling aspen forest. Agric. For. Meteorol. 87, 313–329. Chen, J., Saunders, S., Crow, T., Naiman, R., Brosofske, K., Mroz, G., Brookshire, B., Franklin, J., 1999. Microclimate in forest ecosystem and landscape ecology: variations in local climate can be used to monitor and compare the effects of different management regimes. BioScience 49, 288–297. Chmura, D., 2004. Penetration and naturalisation of invasive alien plant species (neophytes) in woodlands of the silesian upland (Southern Poland). Nat. Conserv. 60, 3–11. Chmura, D., Sierka, E., 2007. The invasibility of deciduous forest communities after disturbance: a case study of Carex brizoides and impatiens parviflora invasion. For. Ecol. Manage. 242, 487–495. Christensen, M., Emborg, J., 1996. Biodiversity in natural versus managed forest in Denmark. For. Ecol. Manage. 85, 47–51. Christensen, M., Hahn, K., Mountford, E.P., Ódor, P., Standovár, T., Rozenbergar, D., Diaci, J., Wijdeven, S., Meyer, P., Winter, S., Vrska, T., 2005. Dead wood in European beech (Fagus sylvatica) forest reserves. For. Ecol. Manage. 210, 267–282. Clot, F., 1990. Les érablaies européennes: essai de synthèse. Phytocoenologia 409–564.

4.2. Structural characteristics and implications for forest management Many studies have shown how management practices affect the structural features of forest stand (Kuuluvainen et al., 1996; Commarmot et al., 2005; Wesely et al., 2018). Unfortunately, our dataset consisted of phytosociological relevés, so brought only limited information regarding forest stand structure. Thus, detailed comparisons of structural characteristics were not possible except for the cover of different vegetation layers. There were significant differences in the cover of shrubs, which was higher in managed forests. Consequently, the coverage of trees was slightly higher (but not statistically significant) in protected forests. This finding may be attributed to the process of regeneration and increase in the abundance of the younger generation of trees. These simple comparisons give very limited insight into the structural effects of forest management in ravine forests. However, in our other research based on five permanent plots (Baran and Bodziarczyk, 2018), we showed that managed ravine forests were characterised by a higher density of living trees and lower density of dead trees. Similar research has been published by other authors for comparisons of structural indices between managed and old-growth forests (McGee et al., 1999; Liira and Sepp, 2009; Meyer and Schmidt, 2011; Burrascano et al., 2013; Wesely et al., 2018). These findings are of great importance and show that structural features are much better predictors of both past and present management practices than a comparison of plant species composition. An interpretation of no differences in plant diversity between managed and protected forests could lead to the conclusion that there is no effect from low intensity forest management on biodiversity. However, a comparison of the structural features, especially the amount of coarse woody debris, which is essential for maintaining high biodiversity in forests, reveals different effects. High species richness, high contribution of ancient forest species and marginal level of plant invasions showed that ravine forest are of high importance for protection of biodiversity resources. Paradoxically, under these unstable and harsh conditions the species composition remained quite stable even when subjected to forest management. We did not identify any negative effects of the management practices; however, these results must be interpreted very carefully. The intensity of management practices is the main factor shaping the response of vegetation to forest management. Due to inaccessibility, harsh conditions and 592


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