Skip to main content

Advertisement

SpringerLink
Log in

A review of habitat thresholds for dead wood: a baseline for management recommendations in European forests

  • Review
  • Published:
European Journal of Forest Research Aims and scope Submit manuscript

Abstract

In contemporary forest management, also of commercial forests, threshold values are widely used for consideration of biodiversity conservation. Here, we present various aspects of dead-wood threshold values. We review published and unpublished dead-wood threshold data from European lowland beech–oak, mixed-montane, and boreo-alpine spruce–pine forests separately to provide managers of European forests with a baseline for management decisions for their specific forest type. Our review of dead-wood threshold data from European forests revealed 36 critical values with ranges of 10–80 m3 ha−1 for boreal and lowland forests and 10–150 m3 ha−1 for mixed-montane forests, with peak values at 20–30 m3 ha−1 for boreal coniferous forests, 30–40 m3 ha−1 for mixed-montane forests, and 30–50 m3 ha−1 for lowland oak–beech forests. We then expand the focus of dead-wood threshold analyses to community composition. We exemplify the two major statistical methods applied in ecological threshold analysis to stimulate forest researchers to analyze more of their own data with a focus on thresholds. Finally, we discuss further directions of dead-wood threshold analysis. We anticipate that further investigations of threshold values will provide a more comprehensive picture of critical ranges for dead wood, which is urgently needed for an ecological and sustainable forestry.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Fig. 1
Fig. 2
Fig. 3
Fig. 4

Similar content being viewed by others

References

  • Albrecht L (1991) Die Bedeutung des toten Holzes im Wald. Forstw Cbl 110:106–113

    Article  Google Scholar 

  • Ammer U (1991) Konsequenzen aus den Ergebnissen der Totholzforschung für die forstliche Praxis. Eur J Forest Res 110:149–157

    Google Scholar 

  • Andersen T, Carstensen J, Hernández-García E, Duarte CM (2008) Ecological thresholds and regime shifts: approaches to identification. Trends Ecol Evol 24:49–57

    Article  PubMed  Google Scholar 

  • Angelstam P (2002) Reconciling land management with natural disturbance regimes in European boreal forests. In: Bissonette J, Storch I (eds) Landscape ecology and resource management: managing the match. Island Press, pp, pp 193–226

    Google Scholar 

  • Angelstam P (2004) Habitat thresholds and effects of forest landscape change on the distribution and abundance of black grouse and capercaillie. Ecol Bull 51:173–188

    Google Scholar 

  • Angelstam P, Bütler R, Lazdinis M, Mikusinski G, Roberge JM (2003) Habitat thresholds for focal species at multiple scales and forest biodiversity conservation–dead wood as an example. Ann Zool Fennici 40:473–482

    Google Scholar 

  • Bader P, Jansson S, Jonsson BG (1995) Wood-inhabiting fungi and substratum decline in selectively logged boreal spruce forests. Biol Conserv 72:355–362

    Article  Google Scholar 

  • Basset Y, Missa O, Alonso A, Miller SE, Curletti G, De Meyer M, Eardley C, Lewis OT, Mansell MW, Novotny V, Wagner T (2008) Changes in arthropod assemblages along a wide gradient of disturbance in gabon. Conserv Biol 22:1552–1563

    Article  PubMed  Google Scholar 

  • Bässler C, Müller J (2010) Importance of natural disturbance for recovery of the rare polypore Antrodiella citrinella Niemelä & Ryvarden. Fungal Biol 114:129–133

    Article  Google Scholar 

  • Bässler C, Müller J, Dziock F, Brandl R (2010) Microclimate and especially resource availability are more important than macroclimate for assemblages of wood-inhabiting fungi. J Ecol 98:822–832

    Article  Google Scholar 

  • Boecklen WJ (1986) Effects of habitat heterogeneity on the species-area relationships of forest birds. J Biogeogr 13:59–68

    Article  Google Scholar 

  • Brustel PH (2004) Coléoptères saproxyliques et valeur biologique des forêts francaises. Collect Dossiers For 13:1–297

    Google Scholar 

  • Burnham KP, Anderson DR (2002) Model selection and multimodel inference. Springer, New York

    Google Scholar 

  • Bussler H, Müller J, Dorka V (2005) European natural heritage: the saproxylic beetles in the proposed parcul National Defileul Jiului. Analele ICAS 18:55–71

    Google Scholar 

  • Bütler R, Angelstam P, Ekelund P, Schlaepfer R (2004) Dead wood threshold values for the three-toed woodpecker presence in boreal and sub-Alpine forest. Biol Conserv 119:305–318

    Article  Google Scholar 

  • Christensen M, Hahn K, Mountford EP, Ódor P, Standóvar T, Rozenbergar D, Diaci J, Wijdeven S, Meyer P, Winter S, Vrska T (2005) Dead wood in European beech (Fagus sylvatica) forest reserves. Forest Ecol Manag 210:267–282

    Article  Google Scholar 

  • Davies ZG, Tyler C, Stewart GB, Pullin AS (2008) Are current management recommendations for conserving saproxylic invertebrates effective? Biodivers Conserv 17:209–234

    Article  Google Scholar 

  • DeMaynadier PG, Hunter ML (1995) The relationship between forest management and amphibian ecology: a review of the North American literature. Environ Rev 3:230–261

    Google Scholar 

  • Dickson JG, Conner RN, Williamson JH (1983) Snag retention increases bird use of a clear-cut. J Wildl Manage 47:799–804

    Article  Google Scholar 

  • Dziock F (2006) Life-history data in bioindication procedures, using the example of hoverflies (Dipter, Syrphidae) in the Elbe floodplain. Int Rev Hydrobiol 91:341–363

    Article  Google Scholar 

  • Ekbom B, Schroeder LM, Larsson S (2006) Stand specific occurence of coarse woody debris in a managed boreal forest landscape in central Sweden. Forest Ecol Manag 221:2–12

    Google Scholar 

  • Erdmann M, Wilke H (1997) Quantitative und qualitative Totholzerfassung in Buchenwirtschaftswäldern. Eur J Forest Res 116:16–28

    Google Scholar 

  • Flade M, Möller G, Schumacher H, Winter S (2004) Naturschutzstandards für die Bewirtschaftung von Buchenwäldern im nordostdeutschen Tiefland. Der Dauerwald–Zeitschrift für naturgemässe Waldwirtschaft 29:15–28

    Google Scholar 

  • Fowles AP, Alexander KNA, Key RS (1999) The saproxylic quality Index: evaluating wooded habitats for the conservation of dead-wood Coleoptera. Coleopterist 8:121–141

    Google Scholar 

  • Frank G (2002) Brutzeitliche Einnischung des Weißrückenspechtes Dendrocopos leucotos im Vergleich zum Buntspecht Dendrocopos major in montanen Mischwäldern der nördlichen Kalkalpen. Vogelwelt 123:225–239

    Google Scholar 

  • Ganey JL (1999) Snag density and composition of snag populations on two national forests in northern Arizona. Forest Ecol Manag 117:169–178

    Article  Google Scholar 

  • Goßner M (2004) Diversität und Struktur arborikoler Arthropodenzönosen fremdländischer und einheimischer Baumarten–Ein Beitrag zur Bewertung des Anbaus von Douglasie (Pseudotsuga menziesii (Mirb.) Franco) und Roteiche (Quercus rubra L.). Neobiota 5, 238

  • Goßner M (2006) Uralt und unbekannt. LWF aktuell 53:12–13

    Google Scholar 

  • Grove S (2002a) The influence of forest management history on the integrity of the saproxylic beetle fauna in an Australian lowland tropical rainforest. Biol Conserv 104:149–171

    Article  Google Scholar 

  • Grove S (2002b) Tree basal area and dead wood as surrogate indicators of saproxylic insect faunal integrity: a case study from the Australian lowland tropics. Ecol Indic 1:171–188

    Article  Google Scholar 

  • Grove S (2002c) Saproxylic insect ecology and the sustainable management of forests. Ann Rev Ecol Syst 33:1–23

    Article  Google Scholar 

  • Grove S, Meggs J (2003) Coarse woody debris, biodiversity and management: a review with particular reference to Tasmanian wet eucalypt forests. Aust For 66:258–272

    Google Scholar 

  • Guénette JS, Villard MA (2004) Do empirical thresholds truly reflect species tolerance to habitat alteration. Ecol Bull 51:163–171

    Google Scholar 

  • Haase V, Topp W, Zach P (1998) Eichen-Totholz im Wirtschaftswald als Lebensraum für xylobionte Insekten. Zeitschr Ökol Naturschutz 7:137–153

    Google Scholar 

  • Heilmann-Clausen J, Christensen M (2004) Does size matter? On the importance of various dead wood fractions for fungal diversity in Danish beech forests. Forest Ecol Manag 201:105–117

    Google Scholar 

  • Heilmann-Clausen J, Christensen M (2005) Wood-inhabiting macrofungi in Danish beech-forests—conflicting diversity patterns and their implications in a conservation perspective. Biol Conserv 122:633–642

    Article  Google Scholar 

  • Hering D, Kail J, Eckert S, Gerhard M, Meyer EI, Mutz M, Reich M, Weiss I (2000) Coarse woody debris quantity and distribution in Central European streams. Int Rev Hydrobiol 85:5–23

    Article  Google Scholar 

  • Hilszczanski J, Gibb H, Hjältén J, Atlegrim O, Johansson T, Pettersson RB, Ball JP, Danell K (2005) Parasitoids (Hymenoptera, Ichneumonoidea) of Saproxylic beetles are affected by forest successional stage and dead wood characteristics in boreal spruce forest. Biol Conserv 126:456–464

    Article  Google Scholar 

  • Hothorn T, Zeileis A (2008) Generalized maximally selected statistics. Biometrics 64:1263–1269

    Article  PubMed  Google Scholar 

  • Hothorn T, Hornik K, Zeileis A (2006) Unbiased recursive partitioning: a conditional inference framework. J Comput Graph Stat 15:651–674

    Article  Google Scholar 

  • Hövemeyer K, Schauermann J (2003) Succession of diptera on dead beech: a 10-year study. Pedobiologia 47:61–75

    Article  Google Scholar 

  • Huggett AJ (2005) The concept and utility of ‘ecological thresholds’ in biodiversity conservation. Biol Conserv 124:301–310

    Article  Google Scholar 

  • Jonsell M, Schröder M, Weslien J (2005) Saproxylic beetles and high stumps of spruce—fungal flora important for determining the species composition. Scand J For Res 20:54–63

    Article  Google Scholar 

  • Jönsson MT, Edman M, Jonsson BG (2008) Colonization and extinction patterns of wood-decaying fungi in a boreal old-growth Picea abies forest. J Ecol 96:1065–1075

    Article  Google Scholar 

  • Junninen K, Similä M, Kouki J, Kotiranta H (2006) Assemblages of wood-inhabiting fungi along the gradients of succession and naturalness in boreal pine-dominated forests in Fennoscandia. Ecography 29:75–83

    Article  Google Scholar 

  • Kappes H (2005) The influence of coarse woody debris on the gastropod community of a managed calcareous beech forest in western Europe. J Molluscan Stud 71:85–91

    Article  Google Scholar 

  • Kappes H, Jabin M, Kulfan J, Zach P, Topp W (2009) Spatial patterns of litter-dwelling taxa in relation to the amount of coarse woody debris in European temperate deciduous forests. Forest Ecol Manag 257:1255–1260

    Article  Google Scholar 

  • Kirby KJ, Reid CM, Thomas RC, Goldsmith FB (1998) Preliminary estimates of fallen dead wood and standing dead trees in managed and unmanaged forests in Britain. J Appl Ecol 35:148–155

    Article  Google Scholar 

  • Kratzer R (2008) Totholzschwellenwertanalyse für die Habitate des Dreizehenspechts (Picoides tridactylus alpinus) im Schwarzwald. Diploma, Fakultät für Forst- und Umweltwissenschaften. University Freiburg. Freiburg. 83pp

  • Lindenmayer DB, Luck G (2005) Synthesis: thresholds in conservation and management. Biol Conserv 124:351–354

    Article  Google Scholar 

  • Loser E, Bebié N, Niggli-Luder S, Bürkler F (2005) Wie naturnah ist ein Wald. Schweiz. Z Forstwes 156:13–21

    Article  Google Scholar 

  • MacArthur RH, Wilson EO (1967) The theory of island biogeography. Princeton University Press, Princeton

    Google Scholar 

  • Martikainen P, Siitonen J, Kaila L, Punttila P, Rauh J (1999) Bark beetles (Coleoptera, Scolytidae) and associated beetle species in mature managed and old-growth boreal forests in southern Finland. Forest Ecol Manag 116:1–3

    Article  Google Scholar 

  • Martikainen P, Siitonen J, Punttila P, Kaila L, Rauh J (2000) Species richness of Coleoptera in mature managed and old-growth boreal forests in southern Finland. Biol Conserv 94:199–209

    Article  Google Scholar 

  • Martin K, Eadie JM (1999) Nest webs: a community-wide approach to the management and conservation of cavity-nesting forest birds. Forest Ecol Manag 115:243–257

    Article  Google Scholar 

  • May R (1973) Stability and complexity in model ecosystems. Princeton University Press, USA

    Google Scholar 

  • Möller G (2005) Habitatstrukturen holzbewohnender Insekten und Pilze. LÖBF-Mitteilungen 3:30–35

    Google Scholar 

  • Moning C, Müller J (2008) Environmental key factors and their thresholds for the avifauna of temperate montane forests. Forest Ecol Manag 256:1198–1208

    Article  Google Scholar 

  • Moning C, Bussler H, Müller J (2009) Ökologische Schlüsselwerte in Bergmischwäldern als Grundlage für eine nachhaltige Forstwirtschaft. Wissenschaftliche Reihe des Nationalpark Bayerischer Wald 19:1–102

    Google Scholar 

  • Müller J (2004) Vögel als Inspektionsbeamte in Eichenwäldern. LWF Wissen 46:22–28

    Google Scholar 

  • Müller J (2005) Waldstrukturen als Steuergröße für Artengemeinschaften in kollinen bis submontanen Buchenwäldern. Dissertation, Wissenschaftszentrum Weihenstephan für Ernährung, Landnutzung und Umwelt. Technische Universität. München, http//mediatum.ub.tum.de. 197pp

  • Müller J, Brandl R (2009) Assessing biodiversity by remote sensing and ground survey in montainous terrain: the potential of LiDAR to predict forest beetle assemblages. J Appl Ecol 46:897–905

    Article  Google Scholar 

  • Müller J, Bussler H (2008) Key factors and critical thresholds at stand scale for saproxylic beetles in a beech dominated forest, southern Germany. Rev Écol (Terre Vie) 63:73–82

    Google Scholar 

  • 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

    Article  Google Scholar 

  • Müller J, Hothorn T (2004) Maximally selected two-sample statistics as a new tool for the identification and assessment of habitat factors with an application to breeding-bird communities in oak forests. Eur J Forest Res 123:219–228

    Article  Google Scholar 

  • Müller J, Bußler H, Bense U, Brustel H, Flechtner G, Fowles A, Kahlen M, Möller G, Mühle H, Schmidl J, Zabransky P (2005a) Urwald relict species—Saproxylic beetles indicating structural qualities and habitat tradition. Waldökologie Online 2:106–113

    Google Scholar 

  • Müller J, Strätz C, Hothorn T (2005b) Habitat factors for land snails in acid beech forests with a special focus on coarse woody debris. Eur J Forest Res 124:233–242

    Article  Google Scholar 

  • Müller J, Bußler H, Utschick H (2007a) Wie viel Totholz braucht der Wald? Ein wissenschaftsbasiertes Konzept gegen den Artenschwund der Totholzzönosen. NUL 39:165–170

    Google Scholar 

  • Müller J, Engel H, Blaschke M (2007b) Assemblages of wood-inhabiting fungi related to silvicultural management intensity in beech forests in southern Germany. Eur J Forest Res 126:513–527

    Article  Google Scholar 

  • Müller J, Bussler H, Kneib T (2008) Saproxylic beetle assemblages related to silvicultural management intensity and stand structures in a beech forest in Southern Germany. Eur J Insect Conserv 12:107–124

    Article  Google Scholar 

  • Muradin R (2001) Ecological thresholds: a survey. Ecol Econ 38:7–24

    Article  Google Scholar 

  • Murthy SK (1998) Automatic construction of decision trees from data: a multi-disciplinary survey. Data Min Knowl Disc 2:345–389

    Article  Google Scholar 

  • Neft R (2006) Biotopbaum- und Totholzkonzept des Unternehmens Bayerische Staatsforsten (BaySF). LWF aktuell 55:28–29

    Google Scholar 

  • Ódor P, Heilmann-Clausen J, Christensen M, Aude E, Dort v KW, Piltaver A, Siller I, Veerkamp MT, Standovár T, Hees v AFM, Kosec J, Matocec N, Kraigher H, Grebenc T (2006) Diversity of dead wood inhabiting fungi and bryophytes in semi-natural beech forests in Europe. Biol Conserv 131:58–71

    Article  Google Scholar 

  • Okland B, Bakke A, Hagvar S, Kvamme T (1996) What factors influence the diversity of saproxylic beetles? A multiscaled study from a spruce forest in southern Norway. Biodivers Conserv 5:75–100

    Article  Google Scholar 

  • Pechacek P, D’Oleire-Oltmanns W (2004) Habitat use of the three-toed woodpecker in central Europe during the breeding period. Biol Conserv 116:333–341

    Article  Google Scholar 

  • Penttilä R, Siitonen J, Kuusinen M (2004) Polypore diversity in managed and old-growth boreal Picea abies forests in southern Finland. Biol Conserv 117:271–283

    Article  Google Scholar 

  • Penttilä R, Lindgren M, Miettinen O, Rita H, Hanski I (2006) Consequences of forest fragmentation for polyporous fungi at two spatial scales. Oikos 114:225–240

    Article  Google Scholar 

  • Quinn GP, Keough MJ (2002) Experimental Design and Data Analysis for Biologists. Cambridge University Press, Cambridge

    Google Scholar 

  • R Core Development Team (2008) R: a language and environment for statistical computing. Vienna, Austria: R Foundation for Statistical Computing 3-900051-07-0

  • Ranius T (2002) Influence of stand size and quality of tree hollows on saproxylic beetles in Sweden. Biol Conserv 103:85–91

    Article  Google Scholar 

  • Ranius T (2006) Measuring the dispersal of saproxylic insects: a key characteristic for their conservation. Popul Ecol 48:177–188

    Article  Google Scholar 

  • Ranius T, Fahrig L (2006) Targets for maintenance of dead wood for biodiversity conservation based on extinction thresholds. Scand J For Res 21:201–208

    Article  Google Scholar 

  • Reemer M (2005) Saproxylic hoverflies benefit by modern forest management (Diptera: Syrphidae). J Insect Conserv 9:49–59

    Article  Google Scholar 

  • Roberge J-M, Angelstam P, Villard MA (2008) Specialised woodpeckers and naturalness in hemiboreal forests—Deriving quantitative targets for conservation planning. Biol Conserv 141:997–1012

    Article  Google Scholar 

  • Roff DA (2006) Introduction to computer-intensive methods of data analysis in biology. Cambridge University Press, Cambridge

    Book  Google Scholar 

  • Schiegg K (2000) Are there saproxylic beetle species characteristic of high dead wood connectivity? Ecography 23:579–587

    Article  Google Scholar 

  • Schlaepfer R, Bütler R (2004) Critères et indicateurs de la gestion des ressources forestières: Prise en compte de la complexité et de l’approche écosystémique. Revue Forestière Française 56:431–444

    Google Scholar 

  • Schmidt O (2006) Totes Holz voller Leben. LWF aktuell 53:1

    Google Scholar 

  • Schulz U, Ammer U (1997) Aufgeklappte Wurzelteller und ihr Beitrag zur Insekten-Diversität des Waldes. Mitt Dtsch Ges Allg Angew Ent 11:677–682

    Google Scholar 

  • Siitonen J (2001) Forest management, coarse woody debris and saproxylic organisms: Fennoscandian boreal forests as an example. Ecol Bull 49:11–41

    Google Scholar 

  • Siitonen J, Saaristo L (2000) Habitat requirements and conservation of Pytho kolwensis, a beetle species of old-growth boreal forest. Biol Conserv 94:211–220

    Article  Google Scholar 

  • Siitonen J, Martikainen P, Punttila P, Rauh J (2000) Coarse woody debris and stand characteristics in mature managed and old-growth boreal mesic forests in southern Finland. Forest Ecol Manag 128:211–225

    Article  Google Scholar 

  • Similä M, Kouki J, Martikainen P (2003) Saproxylic beetles in managed and seminatural scots pine forests: quality of dead wood matters. Forest Ecol Manag 174:365–381

    Article  Google Scholar 

  • Speight MCD (1989) Saproxylic invertebrates and their conservation. Council Eur Nat Environ Ser 42:1–79

    Google Scholar 

  • Stokland JN, Tomter SM, Söderberg U (2004) Development of dead wood indicators for biodiversity monitoring: experiences from Scandinavia. In: Marchetti M (ed) Proceedings of the monitoring and indicators of forest biodiversity in Europe—from ideas to operationality, Florence, 207–226pp

  • Sullivan TP, Sullivan DS (2001) Influence of variable retention harvest on forest ecosystems. II Diversity and population dynamics of small mammals. J Appl Ecol 38:1234–1252

    Article  Google Scholar 

  • ter Braak CJF, Smilauer P (1998) CANOCO reference manual and user’s guide to Canoco for Windows: software for Canonical community ordination (version 4). Mirocomputer Power, Ithaca, New York

    Google Scholar 

  • Tilman D, May RM, Lehman C, Nowak M (1994) Habitat destruction and the extinction debt. Nature 371:65–66

    Article  Google Scholar 

  • Tremblay JA, Ibarzabal C, Dussault C, Savard JP (2009) Habitat requirements of breeding black-backed woodpecker in unburned boreal forests. Avian Conserv Ecol 4(1):2, [online] ULR: http://www.ace-eco.org/vol4/iss1/art2

    Google Scholar 

  • Ulikzka H, Angelstam P (2000) Assessing conservation values of forest stands based on specialised lichens and birds. Biol Conserv 95:343–351

    Article  Google Scholar 

  • Utschick H (1991) Beziehungen zwischen Totholzreichtum und Vogelwelt in Wirtschaftswäldern. Eur J Forest Res 110:135–148

    Google Scholar 

  • Villard M-A (2009) Designing studies to develop conservation targets: a review of the challenges. In: Villard M-A, Jonsson BG (eds) Setting conservation targets for managed forest Landscapes. Cons Biol 16, 30–49

  • Vodka S, Konvicka M, Cizek L (2009) Habitat preferences of oak-feeding xylophagous beetles in a temperate woodland: implications for forest history and management. J Insect Conserv doi:10.1007/s10841-008-9202-1

  • Winter S, Flade M, Schumacher H, Kerstan E, Möller G (2005) The importance of near natural stand structures for the biocoenosis of lowland beech forests. For Snow Lansc Res 79:127–144

    Google Scholar 

Download references

Acknowledgments

We thank Karen A. Brune for linguistic revision of the manuscript and Thibault Lachat, Christophe Bouget and an anonymous reviewer for helpful comments on an earlier version of the manuscript.

Author information

Authors and Affiliations

  1. National Park Bavarian Forest, Freyunger Str. 2, 94481, Grafenau, Germany

    Jörg Müller

  2. WSL Swiss Federal Institute for Forest, Snow and Landscape Research, Site Lausanne, Case postale 96, c/o EPFL, 1015, Lausanne, Switzerland

    Rita Bütler

  3. Ecole Polytechnique Fédérale de Lausanne (EPFL), Laboratory of Ecological Systems, ECOS, Station 2, 1015, Lausanne, Switzerland

    Rita Bütler

Authors
  1. Jörg Müller
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Rita Bütler
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to Jörg Müller.

Additional information

Communicated by K. Puettmann.

Electronic supplementary material

Rights and permissions

Reprints and permissions

About this article

Cite this article

Müller, J., Bütler, R. A review of habitat thresholds for dead wood: a baseline for management recommendations in European forests. Eur J Forest Res 129, 981–992 (2010). https://doi.org/10.1007/s10342-010-0400-5

Download citation

  • Received:

  • Revised:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s10342-010-0400-5

Keywords

Search

Navigation