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    Deadwood and old-growth stands are essential for birds

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    Lying deadwood is extremely important for regeneration, especially in mountain forests. Young trees emerge from this decaying spruce trunk, where the snow melts earlier in spring than on the surrounding ground. © Pierre Mollet

    Deadwood and old-growth stands are critical resources for a wide variety of species groups. Both have become more abundant in forests of marginal economic importance. Not surprisingly, birds that rely on deadwood and old growth show positive population trends. However, in lowland forests especially, there is a lack of deadwood and old-growth stands as well as forest reserves.

    Deadwood refers to dead tree material in various forms: standing and lying trees or parts of trees, but also root plates or tree stumps. The main processes that create deadwood are ageing, windthrow, fire, and fungal or insect infestations. In most forests, ageing is the driving force. Deadwood is therefore much more abundant in old-growth stands than in young forests. Veteran trees with thick trunks and branches and large crowns are another particularly valuable feature.

    The decay of deadwood is caused mainly by fungi and insects: after the bark of a dead tree falls off, the hard wood gradually softens until it turns into humus. The speed of this process depends on the tree species, humidity, exposure to wind and sun, summer temperatures and contact with ground vegetation or the damp forest floor.

    Habitat for numerous specialised organisms

    Deadwood takes a variety of forms that change continuously throughout the process of decay, offering countless cavities that provide habitat for an equally large number of specialised organisms. About a quarter of our native woodland species need deadwood, including more than 1700 beetles and over 2700 species of macrofungi.

    Without the influence of major events such as fire or storms, the creation of deadwood is a slow process, and large amounts take a long time to form. In cultivated forests, where timber is regularly removed, the quantity of deadwood amounts to a few m3/ha and is thus much smaller than in unexploited forests, where the volume of deadwood can reach 200 m3/ha and make up almost half a forest’s total timber volume. Because there are very few unmanaged forests in Europe following centuries of more or less intensive silviculture, many organisms that live in deadwood, especially insects, have become rare and are considered threatened.

    Important for many species of birds

    Deadwood is also of great importance for several bird species. Dead trunks and large branches enable or facilitate the excavation of nesting cavities for woodpeckers, Crested Tit, Alpine and Willow Tit, and other cavity nesters. Natural cavities or cracks and hollows beneath dead, protruding pieces of bark are excellent nesting sites for species like the Eurasian Treecreeper. Dead and dying wood provides habitat for arthropods and their larvae, which several species of woodpecker feed on. The Black Woodpecker, for instance, likes to feed on carpenter ants, whose nests are close to the ground in spruce trees with rotting trunks. The Three-toed Woodpecker is a specialist feeder with a preference for bark beetles and longhorn beetles. The White-backed Woodpecker relies to a particular degree on large quantities of deadwood due to its preference for saproxylic insect larvae. Two typical habitats of the White-backed Woodpecker in northern Grisons contained 107 and 163 m3 of deadwood per hectare, respectively.

    Distribution change since 1993–1996 of eight common species that require deadwood and old-growth stands (Eurasian Green Woodpecker, Black Woodpecker, Great Spotted Woodpecker, Middle Spotted Woodpecker, Lesser Spotted Woodpecker, Crested Tit,  Alpine and Willow  Tit, Eurasian Treecreeper). The map combines the distribution change maps of all eight species.

    The volume of deadwood in Swiss forests more than doubled between 1993–1995 and 2009–2013, increasing from 11 to 26 m3/ha on average, a development that at least partly explains the population increases of several bird species that rely on deadwood. In the lower-lying, easily accessible woods of the Central Plateau and the Jura, however, the average volume of deadwood is still well below 20 m3/ha. The need for improvements, such as the creation of natural forest reserves where interventions are kept to a minimum and the forest is left to natural succession, is all the more urgent in these areas.

    Old forests rich in deadwood are necessary to support specialised species, but are absent in many parts of the country, especially in easily accessible areas of the Central Plateau and Jura. 

    © Gilberto Pasinelli

    Urgent need to promote deadwood and old growth

    The shortage of old-growth stands and therefore dead and old wood is considered one of the greatest ecological deficits of managed forests. Accordingly, promoting deadwood and old-growth stands is an important federal objective, especially on the Central Plateau and in the Jura. Natural forest reserves are at the forefront of this strategy and are to become core areas for deadwood-dependent species. However, due to the limited mobility of many saproxylic organisms, there would be little connectivity between populations in geographically dispersed forest reserves. Deadwood and old growth therefore need to be protected in the managed forests that lie between forest reserves by promoting old-growth patches and habitat trees, which are left standing until they decay.

    The target values of 25 m3/ha in the Pre-Alps and Alps and 20 m3/ha on the Central Plateau, in the Jura and the southern Alps will presumably benefit most species of birds that depend on old and decaying wood. For the Three-toed Woodpecker, for example, a threshold value of at least 15 m3/ha on at least 100 ha of forest was calculated. This value is already reached in most woodlands of the Pre-Alps and Alps today. The population of the Three-toed Woodpecker has indeed responded with increasing numbers in the past 15 years or so, and trends are equally positive for most other birds that depend on deadwood and old-growth stands. For the White-backed Woodpecker, however, these threshold values are insufficient. The species will only be able to spread in the long term if much larger areas of forest at low altitudes are left unmanaged for long periods of time, so that large quantities of deadwood and old growth can accumulate, or if old and dead trees are left much more frequently in managed forests. Many other specialists of deadwood stand to benefit from these measures as well.

    Text: Pierre Mollet & Gilberto Pasinelli


    Recommended citation of the Atlas online:
    Knaus, P., S. Antoniazza, S. Wechsler, J. Guélat, M. Kéry, N. Strebel & T. Sattler (2018): Swiss Breeding Bird Atlas 2013–2016. Distribution and population trends of birds in Switzerland and Liechtenstein. Swiss Ornithological Institute, Sempach.

    References

    Abegg, M., U.-B. Brändli, F. Cioldi, C. Fischer, A. Herold-Bonardi, M. Huber, M. Keller, R. Meile, E. Rösler, S. Speich, B. Traub & B. Vidondo (2014a): Fourth national forest inventory - result tables and maps on the Internet for the NFI 2009-2013 (NFI4b). Swiss Federal Research Institute WSL, Birmensdorf. http://www.lfi.ch/resultate/ (Stand: 30.3.2018).

    Abegg, M., U.-B. Brändli, F. Cioldi, C. Fischer, A. Herold-Bonardi, M. Huber, M. Keller, R. Meile, E. Rösler, S. Speich, B. Traub & B. Vidondo (2014b): Quarto inventario forestale nazionale - Tabelle e cartine dei risultati in internet IFN 2009-2013 (IFN4b). Istituto federale di ricerca WSL, Birmensdorf. http://www.lfi.ch/resultate/ (Stand: 30.3.2018).

    Abegg, M., U.-B. Brändli, F. Cioldi, C. Fischer, A. Herold-Bonardi, M. Huber, M. Keller, R. Meile, E. Rösler, S. Speich, B. Traub & B. Vidondo (2014c): Quatrième inventaire forestier national suisse - tableaux et cartes des résultats de l’IFN 2009-2013 disponibles sur internet (IFN4b). Institut fédéral de recherches WSL, Birmensdorf. http://www.lfi.ch/resultate/ (Stand: 30.3.2018).

    Abegg, M., U.-B. Brändli, F. Cioldi, C. Fischer, A. Herold-Bonardi, M. Huber, M. Keller, R. Meile, E. Rösler, S. Speich, B. Traub & B. Vidondo (2014d): Viertes Schweizerisches Landesforstinventar - Ergebnistabellen und Karten im Internet zum LFI 2009-2013 (LFI4b). Eidgenössische Forschungsanstalt WSL, Birmensdorf. http://www.lfi.ch/resultate/ (Stand: 30.3.2018).

    Albrecht, L., R. Geiser, W. Neuerburg & J. Rauh (1988): Das Naturwaldreservat "Wettersteinwald". Jahrb. Ver. Schutz Bergwelt 53: 87–105.

    Brändli, U.-B., F. Cioldi, C. Fischer & M. Huber (2015a): Inventaire forestier national – Analyses ciblées à l’occasion du Rapport forestier 2015, disponibles en ligne. Institut fédéral de recherches WSL, Birmensdorf. http://www.lfi.ch/publ/waldbericht/2015-fr.php (Stand: 30.3.2018).

    Brändli, U.-B., F. Cioldi, C. Fischer & M. Huber (2015b): Inventario forestale svizzero – Analisi speciali per il Rapporto forestale 2015 in internet. WSL, Birmensdorf. Istituto federale di ricerca WSL, Birmensdorf. http://www.lfi.ch/publ/waldbericht/2015-it.php (Stand: 30.3.2018).

    Brändli, U.-B., F. Cioldi, C. Fischer & M. Huber (2015c): Schweizerisches Landesforstinventar – Spezialauswertungen zum Waldbericht 2015 im Internet. Eidgenössische Forschungsanstalt WSL, Birmensdorf. http://www.lfi.ch/publ/waldbericht/2015.php (Stand: 30.3.2018).

    Brändli, U.-B., F. Cioldi, C. Fischer & M. Huber (2015d): Swiss National Forest Inventory – Special assessments for the Forest Report 2015 in the internet. Swiss Federal Research Institute WSL, Birmensdorf. http://www.lfi.ch/publ/waldbericht/2015-en.php (Stand: 30.3.2018).

    Bühler, U. (2009): Totholz - existenziell für den Weissrückenspecht in Nordbünden. Schweiz. Z. Forstwes. 160: 210–217.

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

    Bütler, R., T. Lachat & R. Schlaepfer (2006): Saproxylische Arten in der Schweiz: ökologisches Potenzial und Hotspots. Schweiz. Z. Forstwes. 157: 208–216.

    Harmon, M. E., J. F. Franklin, F. J. Swanson, P. Sollins, S. V. Gregory, J. D. Lattin, N. H. Anderson, S. P. Cline, N. G. Aumen, J. R. Sedell, G. W. Lienkaemper, K. Cromack Jr. & K. W. Cummins (1986): Ecology of coarse woody debris in temperate ecosystems. Adv. Ecol. Res. 15: 133–302.

    Imesch, N., B. Stadler, M. Bolliger & O. Schneider (2015a): Biodiversität im Wald: Ziele und Massnahmen. Vollzugshilfe zur Erhaltung und Förderung der biologischen Vielfalt im Schweizer Wald. Umwelt-Vollzug Nr. 1503. Bundesamt für Umwelt, Bern.

    Imesch, N., B. Stadler, M. Bolliger & O. Schneider (2015b): Biodiversité en forêt: objectifs et mesures. Aide à l’exécution pour la conservation de la diversité biologique dans la forêt suisse. L'environnement pratique n° 1503. Office fédéral de l'environnement, Berne.

    Mayer, H., M. Neumann & W. Schrempf (1979): Der Urwald Rothwald in den Niederösterreichischen Kalkalpen. Jahrb. Ver. Schutz Bergwelt 44: 79–117.

    Mollet, P., N. Zbinden & H. Schmid (2009): Steigende Bestandszahlen bei Spechten und anderen Vogelarten dank Zunahme von Totholz? Schweiz. Z. Forstwes. 160: 334–340.

    Monnerat, C., S. Barbalat, T. Lachat & Y. Gonseth (2016a): Lista Rossa dei Coleotteri Buprestidi, Cerambicidi, Cetonidi e Lucanidi. Specie minacciate in Svizzera. Pratica ambientale n. 1622. Ufficio federale dell’ambiente, Berna, Info Fauna – CSCF, Neuchâtel, e Istituto federale di ricerca WSL, Birmensdorf.

    Monnerat, C., S. Barbalat, T. Lachat & Y. Gonseth (2016b): Liste rouge des Coléoptères Buprestidés, Cérambycidés, Cétoniidés et Lucanidés. Espèces menacées en Suisse. L'environnement pratique n° 1622. Office fédéral de l’environnement, Berne, Info Fauna – CSCF, Neuchâtel, et Institut fédéral de recherches WSL, Birmensdorf.

    Monnerat, C., S. Barbalat, T. Lachat & Y. Gonseth (2016c): Rote Liste der Prachtkäfer, Bockkäfer, Rosenkäfer und Schröter. Gefährdete Arten der Schweiz. Umwelt-Vollzug Nr. 1622. Bundesamt für Umwelt, Bern, Info Fauna – CSCF, Neuenburg, und Eidgenössische Forschungsanstalt WSL, Birmensdorf.

    Pechacek, P. & A. Kristin (2004): Comparative diets of adult and young Three-toed Woodpeckers in a European alpine forest community. J. Wildl. Manage. 68: 683–693.

    Rigling, A. & H. P. Schaffer (2015a): Forest report 2015. Condition and use of Swiss forests. Federal Office for the Environment, Bern, and Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf.

    Rigling, A. & H. P. Schaffer (2015b): Rapport forestier 2015. État et utilisation de la forêt suisse. Office fédéral de l’environnement, Berne, et Institut fédéral de recherches sur la forêt, la neige et le paysage WSL, Birmensdorf.

    Rigling, A. & H. P. Schaffer (2015c): Rapporto forestale 2015. Stato e utilizzazione del bosco svizzero. Ufficio federale dell’ambiente, Berna, e Istituto federale di ricerca per la foresta, la neve e il paesaggio WSL, Birmensdorf.

    Rigling, A. & H. P. Schaffer (2015d): Waldbericht 2015. Zustand und Nutzung des Schweizer Waldes. Bundesamt für Umwelt, Bern, und Eidgenössische Forschungsanstalt WSL, Birmensdorf.

    Scherzinger, W. (1996): Naturschutz im Wald. Qualitätsziele einer dynamischen Waldentwicklung. Praktischer Naturschutz. Ulmer, Stuttgart.

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

    Speight, M. C. D. (1989): Saproxylic invertebrates and their conservation. Council of Europe, Strasbourg.

    Vallauri, D., J. André & J. Blondel (2003): Le Bois mort, une lacune des forêts gérées. Rev.For.Fr. 2: 99–112.

    Vandekerkhove, K., L. De Keersmaeker, N. Menke, P. Meyer & P. Verschelde (2009): When nature takes over from man: Dead wood accumulation in previously managed oak and beech woodlands in North-western and Central Europe. For. Ecol. Manage. 258: 425–435.

     

    Species concerned
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    Woodland
    Land management & land use
    Species in decline
    Species on the rise
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