Aspects of biodiversity of Scots pine forests in Europe

Abstract

Management  of Scots pine, the most widely distributed conifer in the world, was often  based on    clearfelling and replanting regimes, resulting in a rather poor  biodiversity value. However, there    is nowadays a general expectation to increase biodiversity by applying a  more complex    silviculture.    Although present knowledge of genetic factors is insufficient to draw firm  conclusions on the    desirable level of genetic diversity, it seems unlikely that current  silvicultural practices will limit    genetic diversity in Scots pine    Native pinewoods are rare in Europe, but have a flora and fauna of high  conservation value.    Therefore they must be recognized as a priority habitat under the European  Commission's    Habitat Directive. The high conservation value of native stands is a  function of their old-growth    structure that provides a rare habitat.    A number of measures should be taken in all types of Scots pine forests to  enhance biodiversity.    Firstly, old growth habitats should be promoted. Foresters have to accept  that a small    percentage of the pine resource should be managed upon much longer  rotations. Secondly,    retention of deadwood should be encouraged. Dead and dying wood are key  components of    stand structure and act as key substrates for many associated species, such  as microbes,    invertebrates, small mammals and birds. Furthermore, a complex stand  structure should be    promoted at both the horizontal and the vertical scale. A small scale  forestry, group regeneration    systems, natural regeneration, introduction of broadleaves and stronger  thinnings are strongly    recommended. Availability of quite precise niches significantly increases  biodiversity value.    Conservation of isolated populations, found under extreme environmental  conditions, is an    absolute need. Populations endangered either by their small size or by  environmental stresses,    hybridization with other species or human interference should be primarily  conserved. Forest    edges support a range of taxa, and open habitats can comprise many  different plant community    types. A large number of organisms are directly or indirectly dependent on  or favoured by fire.    However, enhancing biodiversity provokes also some risks. Generally,  browsing is considered    as a moderate risk. Introduced species, such as aspen, act as an alternate  host to the rust.    Open species can present a threat to the European pine marten, dying and  deadwood can    provide breeding habitats for pest species (Tomicus  piniperda), burning increases the risk of    seedlings being attacked pine fire fungus (Rhizina  undulata) and forest edges may be an    attractive habitat for pest insects.    An extension of existing growth models is needed to incorporate  biodiversity issues in forest    management planning. Distance dependent individual tree growth models should  be developed.    Sets of indicators for biodiversity must integrate compositional,  structural and functional attributes. Attributes such as species richness,  species abundance, species diversity, horizontal and vertical distribution,  tree age, tree size, stand diversity, architectural complexity, genetic  variants and deadwood are needed for the establishment of biodiversity  indices. Assessment of functional phenomena needs the knowledge of the  driving biotic environmental factors.