Abstract
Forest reserves can serve as an opportunity for studying natural processes in the wild. We studied the effect of easy-to-see tree level indicators on saproxylic beetles (Coleoptera), using window traps. Our study was conducted in old-growth mountainous spruce–beech forest Bukacka in the Orlicke Mts. (Czech Republic). Our analyses showed that the species composition of the study group and its response to tree level indicators in the relatively homogenous environment of old-growth mountainous forest area could be explained reasonably well through variance partitioning. The results indicated that the decay stage was the category hosting the highest level of explained variance with respect to saproxylics, followed by diameter and tree. Red-listed beetle species were nearly the same associated with conifers and broadleaves. Our results highlighted the desirability of using tree level indicators to assess insect diversity, using window traps on tree trunk.
Similar content being viewed by others
Avoid common mistakes on your manuscript.
Introduction
Forest ecosystems historically dominated the central European landscape (Küster 2000; Rackham 2006). The forest cover and its spatial structure have been dramatically altered (McNeely 2002). Most lowland forests were intensively exploited through traditional forest management, although the spatial structure has remained almost constant for a long time (Horak et al. 2012a). The forest cover in sub-mountainous and mountainous regions was exploited by humans considerably later than lowland areas. Nevertheless, the spatial and temporal continuity of forests at higher elevations was changed over a relatively short time span (i.e. one or two centuries; Fanta 1997; McNeely 2002). Except for a few areas which were traditionally managed (e.g. wood pasturing), most forests were clear-cut and the timber was floated on rivers to lowlands due to insufficient stocks of fuel wood and building timber in the latter (Fanta 1997, 2007). Therefore, the insufficiency of timber in lowlands caused a lack of dead wood (a crucial forest habitat) in mountains (e.g. Müller and Bütler 2010).
Sustainable forest management helps to maintain biodiversity. One of the main ambitions of conservation-oriented forest management is to maintain undisturbed forest areas for future generations (Jenkins and Joppa 2009). Thus, the implementation of a hands-off approach (i.e. unmanaged areas) to forest reserve management was, and still is, one of the main forest conservationists’ tools to protect forest biodiversity (Margules and Pressey 2000). From a biological point of view, most central European sub-mountainous and mountainous forests are heavily contaminated by commercial spruce stands (Slodičák et al. 2005; Svoboda et al. 2010). Such stands need to be carefully managed during their entire rotation period and foresters often face increased salvage cuttings caused by windstorms, snow-breakages, insect outbreaks, or fungal diseases (Kelty 2006; Slodičák and Novák 2006). For several reasons, it is difficult to leave naturally disturbed forest areas to their spontaneous development (e.g. due to insect outbreaks, imminent commercial losses, high game stocks). The most implicated management approach following disturbances is the above-mentioned salvage cutting (Jonasova et al. 2010). Nevertheless, it is well known that such management practices strongly affect biota (Lindenmayer et al. 2004; Müller et al. 2008; Vávrová et al. 2009; Pouska et al. 2010).
Forest reserves can serve as an opportunity for studying natural processes in the wild (Margules and Pressey 2000). One of the main problems is identifying an area large enough for worthwhile study, and creating sufficient buffer zones to prevent surrounding commercial forests from exerting potential negative influences (e.g. bark beetle attacks; Jakus et al. 2003). Even in the central European country (namely the Czech Republic), where the forest reserves have been established for almost two centuries (Vrška 2008), there is still a lack of knowledge of insect diversity. Old-growth forests are one of the most studied forest ecosystems, but there is very limited knowledge of the insect diversity at the tree level (e.g. Müller and Goßner 2010).
Decomposing wood, particularly tree trunks and other coarse woody debris, is important as a habitat and resource for many forest organisms (Dynesius et al. 2010). Remnants of forests with veteran trees provide many microhabitats (Winter and Möller 2008). Modern studies have shown that the quality of dead wood, which is associated mainly with tree species, decay stage and stem diameter, contribute to explaining species composition, population densities and species richness of saproxylic beetles (Jonsell et al. 1998; Lindhe and Lindelöw 2004; Toivanen and Kotiaho 2010).
The loss of habitats often leads to vanishing or even extinction, and subsequent red-listing, of formerly common species (Komonen et al. 2008). The recent IUCN Red List of saproxylic beetles (Nieto and Alexander 2010) shows that there is a sharp decline in the distribution of several species and, in certain cases, this led to recent relictual occurrence (Horak et al. 2012a).
Modelling species and environmental relationships is one of the main goals in ecological research (Frutos et al. 2007). Statistical techniques, such as multiple regression methods, are widely used (Guisan and Zimmermann 2000). However, some issues of robustness of these developed models have been detected (MacNally 2000). Techniques such as variance partitioning are used to solve these problems (Borcard et al. 1992; Økland 1999; Lepš and Šmilauer 2003; Svoboda et al. 2011). Through multivariate analyses of ecological data and variation partitioning, it is relatively easy to evaluate the relative importance of the species and their environmental relationships (Burrascano et al. 2011). Although variance partitioning is used in the study of flora and the environment (Aude and Lawesson 1998; Økland 1999), to our knowledge not so many studies have been undertaken on animals, including insects (Kitching et al. 1993; Crist et al. 2006; Horak et al. 2013).
The main goals of our study of undisturbed old-growth mountainous spruce-beech forest were to answer the following questions: (1) are tree level indicators, which are easy-to-see (i.e. simple to collect) in the field, able to explain the species composition of saproxylic beetles and, if so, to what extent and (2) how do red-listed species respond to the environmental variables included in our study?
Materials and methods
Study area
Our study sites were in Bukacka (Eastern Bohemia: Czech Republic), probably the oldest mountainous spruce–beech forest in the Orlicke Mts. (EN: Eagle Mts., DE: Adler Gebirge). This woodland area of more than 50 ha (960–1,025 m a. s. l.) is within the Protected Landscape Area (PLA) of the Orlicke hory and is located on the Czech–Polish border (50°20′N, 16°22′E). The area has recently been protected through hands-off management practices (i.e. unmanaged). However, salvage cutting has been carried out several times over the past decades due to bark beetle (mainly Ips typhographus) outbreaks (e.g. Belicová 1982). The European Beech (Fagus sylvatica) formerly dominated the forest, but is now declining due to several biotic (e.g. high palatability for game stocks) and abiotic (e.g. air pollution) factors, and the Norway Spruce (Picea abies) has been spreading through the area. Typical admixed trees in the tree species composition are rowan (Sorbus aucuparia), and the Sycamore Maple (Acer pseudoplatanus). A smaller part of Bukacka consists of orchid grasslands, formerly pastured and used for growing hay (Hájek and Kučera 2002).
Study groups
We studied saproxylic beetles (Coleoptera), a highly diverse and abundant ecological group. This ecological group is often used in studies on biological diversity and the natural condition of forest habitats (Goßner et al. 2008; Müller et al. 2010; Horak 2011).
Sampling method
We sampled the core area of Bukacka (≈20 ha). We used 20 (one per ha) passive (i.e. non-attractive) window traps, which were placed on tree trunks, and therefore worked as trunk traps. Each trap consisted of three transparent plastic panes (one pane 400 mm × 500 mm and two panes 200 mm × 500 mm), a protective top cover (d = 450 mm), and a funnel leading down into a container holding a solution of water and salt with a small amount of detergent to reduce the surface tension of the liquid. A detailed description of the traps can be found in Horak (2011). We sampled a priori standing high-dimension (i.e. veteran) trees (Table 1). Due to the problems with satellite signal reception in our study area, we were not able to use GPS to determine coordinates, and were therefore not able to provide a map of trap distribution. However, the traps did not have a clumped distribution, and were placed randomly with respect to the study variables (Table 1). Study trees with relatively similar surrounding environments were selected (medium dead wood accumulation, no gaps in canopy and high distance from stand walls). Due to this and the tree species distribution (see section on study area above), we presume that any significant spatial bias in the trap distribution used for our analyses was highly improbable. Each trap was placed at a height of 1.3 m facing the south. The traps were activated during the snow meltdown (i.e. at the end of April), and deactivated during the first frosts at the end of September 2009, which resulted in twelve routine sampling efforts. Thus, each trap was working for a period of 161 days (i.e. 3,220 days for our trapping design).
Study variables
We focused on six tree level characteristics grouped into three categories for the final analyses. We used (1) tree category with two categorical (dummy) variables sorted by tree species sampled (beech, rowan and maple as broadleaves and spruce as conifers); (2) diameter category with two quantitative (continuous) variables—diameter of stem at the breast height (DBH in cm measured at 1.3 m above ground) and height of stem (estimated in m); and (3) decay stage category with two categorical variables—fruiting bodies of wood-decaying fungi (presence and absence) and withering stage of stem (snag, dead tree, withered tree) and one semi-quantitative variable of bark coverage (estimated to the nearest 10 %).
Data analyses
For our analyses we used multivariate statistical methods provided by CANOCO for Windows version 4.5 (ter Braak and Šmilauer 2002). The length of gradient for species composition data was calculated with downweighting of rare species (Lepš and Šmilauer 2003), using detrended correspondence analysis (DCA), at 3.23. We therefore used a canonical correspondence analysis (CCA; ter Braak and Šmilauer 2002) with species composition matrix as dependent variable. The potential bias caused by multi colinearity was controlled by variance inflation factor (VIF < 5; Lepš and Šmilauer 2003). We used focused biplot scaling on inter-species correlations. Monte-Carlo permutation tests with significance of canonical axes (9,999 permutations) under the full model were used (Lepš and Šmilauer 2003). We employed test of explanatory variables for our tree level variables, using a Monte Carlo permutation test (9,999 permutations) under the full model to measure explained variance for each study variable. For the resulting ordination diagrams, we used biplots for both of the sample-environmental variables and species-environmental variables, created in CanoDraw 4.14 (ter Braak and Šmilauer 2002). Statistical significance of associations between particular species and variables of the tree category were tested using t value biplots with van Dobben circles (ter Braak and Šmilauer 2002). The process of variance partitioning is described in detail by many authors (see references in Peres-Neto et al. 2006). Two or three sets of environmental categories are commonly used. The measuring of each fraction was based on sets of multivariate analyses using combinations of species, variables and covariables (Lepš and Šmilauer 2003). We finally visualised the results of variance partitioning using a three circles Venn diagram.
Results
In total, we trapped 1,650 individual beetles (Coleoptera) from 179 species of which 83 species (900 individuals) were saproxylic beetles. One species was critically endangered, seven endangered, nine vulnerable and three near threatened (Table 2).
Variance partitioning
We observed that the decay stage category had the highest explained variance for saproxylic beetles, while the diameter and tree had lower effect on explained variance (Fig. 1), which reflected the number of variables in particular category. The value of fractions with shared variance was not very high. The most shared variance was between the tree species and decay stage categories. On the other hand, the diameter category had a negative shared variation of joint fractions and acted as a suppressor.
Visualisation of canonical correspondence analysis and explained variance of particular variables
We were able to explain nearly 50 % of the variance in the diversity of saproxylic beetles at the tree level (Fig. 1). The first axis explained more than 16 % of the variance and the cumulative percentage variance of species data of the first two shown axes was 26.56 % (Fig. 2). Most species-rich samples were distributed along the first ordination axis (Fig. 2). Broadleaves and conifers, presence and absence of fungi, bark coverage and DBH were significant variables. Broadleaves and conifers shared the most explained variance (>10 %) in saproxylic beetle composition (Table S1 of supplementary material) and six species indicated significant response to the tree category, while half of them preferred broadleaves and half of them conifers (Table 2).
Factors causing occurrence of red-listed species
Nearly the same number of red-listed species was attracted by broadleaves and conifers. Most trapped red-listed beetles seemed not to be responding to the withering stage of stem variables (Fig. 3). The critically endangered saproxylic click beetle Ampedus auripes seemed to prefer dead spruce stems without presence of wood-decaying fungi. The most abundant red-listed rove beetle, saproxylic Hapalaraea pygmaea (EN) seemed to prefer high diameter trees. Two near threatened flightless weevils were trapped in higher abundances—Acalles camelus was more associated with withered infested beech trees, while Trachodes hispidus occurred more on trees with low bark coverage.
Discussion
The tree species category was the only significant with respect to the saproxylic beetle composition. Significant response of saproxylics to broadleaves and conifers with respect to the conventionally studied categories of decay stage and diameter may seem to be surprising. Although this variable is often studied (Jonsell et al. 2007; Horak 2011), most tree-beetle species associations in the conditions of the central Europe do not seem to be so interconnected (e.g. Sláma 1998) as in Scandinavia (e.g. Jonsell et al. 1998). This may reflect that mountainous conditions are much closer to Boreal landscapes due to the continuity and the size of spruce stands in the study site. Although, explained variance and number of associates of conifers was the same as opposed to broadleaves. The coleopteran fauna was composed of species connected with sub-mountainous and mountainous beech and spruce forests of central Europe. The critically endangered click beetle Ampedus auripes, as an example, is a typical saproxylic beetle known to be associated with mountainous spruce forests, which are not negatively affected by intensive forest management (Jarzabek-Müller and Müller 2008). The significant response of saproxylics and nearly 9 % of explained variance to DBH was not surprising because veteran trees of high diameters are known to positively affect the species composition of saproxylic beetles (Alexander 2008). The same reason is most probably for presence and absence of fungi and bark coverage (Horak et al. 2012b).
We found that we were able to explain high levels of variance in our study group using easy-to-see tree level indicators through variance partitioning. In our case of saproxylic beetles, we were able to explain nearly one half of variance. This result highlighted the desirability of tree level indicators when using this design of trap.
The hands-off style of management in smaller areas (as is the case in most of the forest reserves in the Czech Republic), without large-scale disturbances, often results in decreasing heterogeneity of this forest habitat due to over-shading by the closed upper canopy (Konvicka et al. 2004; Horak et al. 2012b). Thus, in our study, in which we needed to combine quantitative, semi-quantitative and categorical variables, and where most of the study variables were not solely able to explain the relationships, possibly due to homogeneity of the study area, variance partitioning seems to be an appropriate method to help explain the interconnection of disparate groups and their habitat.
Conclusions
Our results showed that the beetle species composition and response to tree level indicators in a relatively homogenous environment of old-growth mountainous forest area could be explained reasonably well by variance partitioning. Species composition of saproxylic beetles did not show highly distinct levels of explained variance for categories of variables, but rather at different levels of significance. Some variables, even carefully selected, were not significant to explaining the relationships with the species composition themselves. This could be explained by an absence of spatial heterogeneity in the old-growth forest of our study area, which was subject to hands-off management. Our results highlighted the desirability of tree level indicators when using window traps in trunk tree trap design.
References
Alexander KNA (2008) Tree biology and saproxylic Coleoptera: issues of definitions and conservation language. Rev Ecol 63:1–5
Aude E, Lawesson JE (1998) Vegetation in Danish beech forests: the importance of soil, microclimate and management factors, evaluated by variation partitioning. Plant Ecol 134:53–65
Belicová J (1982) Botanická inventarizace statních přírodních rezervací Bukačka, Častvec, Černá stráň a Sítovka v severovýchodních Čechách. Acta Mus Reginaehrad 17:53–88
Borcard D, Legendre P, Drapeau P (1992) Partialling out the spatial component of ecological variation. Ecology 73:1045–1055
Burrascano S, Sabatini FM, Blasi C (2011) Testing indicators of sustainable forest management on understorey composition and diversity in southern Italy through variation partitioning. Plant Ecol 212:829–841
Crist TO, Pradhan-Devare SV, Summerville KS (2006) Spatial variation in insect community and species responses to habitat loss and plant community composition. Oecologia 147:510–521
Dynesius M, Gibb H, Hjältén J (2010) Surface covering of downed logs: drivers of a neglected process in dead wood ecology. PLoS ONE 5:e13237
Fanta J (1997) Rehabilitating degraded forests in Central Europe into self-sustaining forest ecosystems. Ecol Eng 8:289–297
Fanta J (2007) Lesy a lesnictví ve střední Evropě: II. Z dávné historie využívání lesů. Živa 55:65–69
Frutos A, Olea PP, Vera R (2007) Analyzing and modelling spatial distribution of summering lesser kestrel: the role of spatial autocorrelation. Ecol Model 200:33–44
Goßner M, Engel K, Jessel B (2008) Plant and arthropod communities in young oak stands: are they determined by site history? Biodiv Conserv 17:3165–3180
Guisan A, Zimmermann NE (2000) Predictive habitat distribution models in ecology. Ecol Model 135:147–186
Hájek J, Kučera J (2002) Chapter V., protected landscape area Orlické (Eagle) mountains—Hradec Králové Region. Protected areas of the Czech Republic. AOPK ČR, Praha, EkoCentrum, Brno, ČR
Horak J (2011) Response of saproxylic beetles to tree species composition in a secondary urban forest area. Urban For Urban Green 10:213–222
Horak J, Chobot K, Horakova J (2012a) Hanging on by the tips of the tarsi: review of the plight of critically endangered saproxylic beetle in European forests. J Nat Conserv 20:101–108
Horak J, Chumanova E, Hilszczanski J (2012b) Saproxylic beetle thrives on the openness in management: a case study on the ecological requirements of Cucujus cinnaberinus from Central Europe. Insect Conserv Divers 5:403–413
Horak J, Vodka S, Pavlicek J, Boza P (2013) Unexpected visitors: flightless beetles in window traps. J Insect Conserv 17:441–449
Jakus R, Schlyter F, Zhang QH, Blazenec M, Vavercak R, Grodzki W, Brutovsky D, Lajzova E, Turcani M, Bengtsson M, Blum Z, Gregoire JC (2003) Overview of development of an anti-attractant based technology for spruce protection against Ips typographus: from past failures to future success. J Pest Sci 76:89–99
Jarzabek-Müller A, Müller J (2008) On the distinction between Ampedus auripes (Reitter, 1895) and Ampedus nigrinus (Herbst, 1784) (Coleoptera: Elateridae). Elateridarium 2:199–212
Jenkins CN, Joppa L (2009) Expansion of the global terrestrial protected area system. Biol Conserv 142:2166–2174
Jonasova M, Vavrova E, Cudlin P (2010) Western Carpathian mountain spruce forest after a windthrow: natural regeneration in cleared and uncleared areas. Forest Ecol Manage 259:1127–1134
Jonsell M, Weslien J, Ehnström B (1998) Substrate requirements of red-listed saproxylic invertebrates in Sweden. Biodivers Conserv 7:749–764
Jonsell M, Hansson J, Wedmo L (2007) Diversity of saproxylic beetle species in logging residues in Sweden—comparisons between tree species and diameters. Biol Conserv 138:89–99
Kelty MJ (2006) The role of species mixtures in plantation forestry. Forest Ecol Manage 233:195–204
Kitching RL, Bergelson JM, Lowman MD, McIntyre S, Carruthers DG (1993) The biodiversity of arthropods from Australian rain-forest canopies—general introduction, methods, sites and ordinal results. Aust J Ecol 18:181–191
Komonen A, Jonsell M, Ranius T (2008) Red-listing saproxylic beetles in Fennoscandia: current status and future perspectives. Endanger Species Res 6:149–154
Konvička M, Čížek L, Beneš J (2004) Ohrožený hmyz nížinných lesů: Ochrana a management. Sagittaria, Olomouc, ČR
Küster H (2000) Prehistoric cultures and the development of woodlands. In: Agnoletti A, Anderson S (eds) Methods and approaches in forest history. CABI Publishing, UK, pp 215–220
Lepš J, Šmilauer P (2003) Multivariate analysis of ecological data using CANOCO. Cambridge University Press, UK
Lindenmayer DB, Foster DR, Franklin JF, Hunter ML, Noss RF, Schmiegelow FA, Perry D (2004) Salvage harvesting policies after natural disturbance. Science 303:1303
Lindhe A, Lindelöw A (2004) Cut high stumps of spruce, birch, aspen and oak as breeding substrates for saproxylic beetles. Forest Ecol Manage 203:1–20
MacNally R (2000) Regression and model-building in conservation biology, biogeography and ecology: the distinction between and reconciliation of ‘predictive’ and ‘explanatory’ models. Biodiv Conserv 9:655–671
Margules CR, Pressey RL (2000) Systematic conservation planning. Nature 405:243–253
McNeely JA (2002) Forest biodiversity at the ecosystem level: where do people fit in? Unasylva 53:10–15
Müller J, Bütler R (2010) A review of habitat thresholds for dead wood: a baseline for management recommendations in European forests. Eur J Forest Res 129:981–992
Müller J, Goßner MM (2010) Three-dimensional partitioning of diversity informs state-wide strategies for the conservation of saproxylic beetles. Biol Conserv 143:625–633
Müller J, Bußler H, Goßner M, Rettelbach T, Duelli P (2008) The European spruce bark beetle Ips typographus (L.) in a national park—from pest to keystone species. Biodiv Conserv 17:2979–3001
Müller J, Noss RF, Bussler H, Brandl R (2010) Learning from a”benign neglect strategy” in a national park: response of saproxylic beetles to dead wood accumulation. Biol Conserv 143:2559–2569
Nieto A, Alexander K (2010) European Red list of saproxylic beetles. Publication Office of the EU, Luxembourg
Økland RH (1999) On the variation explained by ordination and constrained ordination axes. J Veg Sci 10:131–136
Peres-Neto PR, Legendre P, Dray S, Borcard D (2006) Variation partitioning of species data matrices: estimation and comparison of fractions. Ecology 87:2614–2625
Pouska V, Svoboda M, Lepsova A (2010) The diversity of wood-decaying fungi in relation to changing site conditions in an old-growth mountain spruce forest, Central Europe. Eur J Forest Res 129:219–231
Rackham O (2006) Woodlands. Collins, London
Sláma EF (1998) Cerambycidae of the Czech and Slovak republics (Beetles-Coleoptera). Milan Sláma, Krhanice
Slodičák M, Novák J (2006) Silvicultural measures to increase the mechanical stability of pure secondary Norway spruce stands before conversion. Forest Ecol Manage 224:252–257
Slodičák M, Novák J, Skovsgaard JP (2005) Wood production, litter fall and humus accumulation in a Czech thinning experiment in Norway spruce (Picea abies (L.) Karst.). Forest Ecol Manage 209:157–166
Svoboda M, Fraver S, Janda P, Bače R, Zenahlíková J (2010) Natural development and regeneration of a Central European montane spruce forest. Forest Ecol Manage 260:707–714
Svoboda D, Peksa O, Veselá J (2011) Analysis of the species composition of epiphytic lichens in Central European oak forests. Preslia 83:129–144
ter Braak CJF, Šmilauer P (2002) CANOCO reference manual and CanoDraw for Windows user’s guide: Software for Canonical Community Ordination (version 4.5). Microcomputer Power, Ithaca, NY, USA
Toivanen T, Kotiaho JS (2010) The preferences of saproxylic beetle species for different dead wood types created in forest restoration treatments. Can J Forest Res 40:445–464
Vávrová E, Cudlín O, Vavříček D, Cudlín P (2009) Ground vegetation dynamics in mountain spruce (Picea abies (L.) Karsten) forests recovering after air pollution stress impact. Plant Ecol 205:305–321
Vrška T (2008) Unmanaged for a hundred and seventy years. In: Zajoncová D (ed) Unmanaged: the natural forest in photography. Moravská galerie, Brno, pp 12–15
Winter S, Möller GC (2008) Microhabitats in lowland beech forests as monitoring tool for nature conservation. Forest Ecol Manage 255:1251–1261
Acknowledgments
We would like to thank our colleagues S. Benedikt, J. Boháč, L. Dvořák, M. Mikát, K. Nováková, P. Průdek, and T. Růžička for help with determination of specimens, P. Stloukal for his support, the non-governmental organization Lesák (lesak.eu) for logistics. A. Scott and D. Pesek corrected the English, and comments of two anonymous referees much helped to improve our work. This study was supported by a Grant CIGA No. 20124310 (Czech University of Life Sciences Prague) and was undertaken with the permission of the Czech Government (no. 1473/09).
Author information
Authors and Affiliations
Corresponding author
Electronic supplementary material
Below is the link to the electronic supplementary material.
Rights and permissions
About this article
Cite this article
Horak, J., Pavlicek, J. Tree level indicators of species composition of saproxylic beetles in old-growth mountainous spruce–beech forest through variation partitioning. J Insect Conserv 17, 1003–1009 (2013). https://doi.org/10.1007/s10841-013-9583-7
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10841-013-9583-7