Is active management the key to the conservation of saproxylic biodiversity? Pollarding promotes the formation of tree hollows

PLoS One. 2013;8(3):e60456. doi: 10.1371/journal.pone.0060456. Epub 2013 Mar 27.

Abstract

Trees with hollows are key features sustaining biodiversity in wooded landscapes. They host rich assemblages of often highly specialised organisms. Hollow trees, however, have become rare and localised in Europe. Many of the associated biota is thus declining or endangered. The challenge of its conservation, therefore, is to safeguard the presence of hollow trees in sufficient numbers. Populations of numerous species associated with tree hollows and dead wood are often found in habitats that were formed by formerly common traditional silvicultural practices such as coppicing, pollarding or pasture. Although it has been occasionally mentioned that such practices increase the formation of hollows and the availability of often sun-exposed dead wood, their effect has never been quantified. Our study examined the hollow incidence in pollard and non-pollard (unmanaged) willows and the effect of pollarding on incremental growth rate by tree ring analysis. The probability of hollow occurrence was substantially higher in pollard than in non-pollard trees. Young pollards, especially, form hollows much more often than non-pollards; for instance, in trees of 50 cm DBH, the probability of hollow ocurrence was ∼0.75 in pollards, but only ∼0.3 in non-pollards. No difference in growth rate was found. Pollarding thus leads to the rapid formation of tree hollows, a habitat usually associated with old trees. It is therefore potentially a very important tool in the restoration of saproxylic habitats and conservation of hollow-dependent fauna. If applied along e.g. roads and watercourses, pollarding could also be used to increase landscape connectivity for saproxylic organisms. In reserves where pollarding was formerly practiced, its restoration would be necessary to prevent loss of saproxylic biodiversity. Our results point to the importance of active management measures for maintaining availability, and spatial and temporal continuity of deadwood microhabitats.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biodiversity*
  • Conservation of Natural Resources*
  • Czech Republic
  • Forestry / methods*
  • Probability
  • Salix / anatomy & histology
  • Salix / growth & development
  • Salix / physiology
  • Trees / anatomy & histology
  • Trees / growth & development
  • Trees / physiology*
  • Wood / physiology*

Grants and funding

The study and its authors were supported by the Czech Science Foundation (P504/12/1952; http://www.gacr.cz), the Technology Agency of the Czech Republic (TA02021501; http://www.tacr.cz), Grant Agency of University of South Bohemia (145/2010/P; http://www.jcu.cz/research/gaju), and the project Biodiversity of Forest Ecosystems (CZ.1.07/2.3.00/20.0064; http://biodiverzita.prf.jcu.cz) co-financed by the European Social Fund and the state budget of the Czech Republic. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.