Servicio de Información Comunitario sobre Investigación y Desarrollo - CORDIS

GAP - regeneration and ground vegetation dynamics

Regeneration and ground vegetation was studied at selected beech forest research sites around Europe (i.e. Denmark, U.K., Netherlands, Germany, Hungary and Slovenia) to produce general recommendations and guidelines for using natural regeneration in beech forests in forest management. The general objective were:

- To determine the ecological differences in gap-phase regeneration and ground vegetation patterns between natural and managed European beech forests;

- To identify suitable methods to naturally regenerate beech forests. The results are based on literature review, study of current practices and field research.

The general aim of the field research work was to assess the interactions between major ecological factors (light, soil conditions, and microclimate) and ground vegetation and tree regeneration patterns found in natural and managed beech forests.

The research showed that within a gap size range of 10-1400m2 in natural beech forests, the relationship between gap size and the spatial distribution and level of key ecological factors (e.g. sun radiation, soil moisture) can be quite variable. This had much to do with the diversity of gap shapes, presence of features in the sub-canopy and under-storey, and topography. Gaps found in managed beech forests, tended to be more discrete and regularly circular. Accordingly, they showed a clearer, steady increase in light and soil moisture levels towards the centre.

The light conditions at the forest floor were dramatically higher within gaps - radiation levels were around ten times greater (3% - 30%) and this initiated a strong regeneration response. However, no strong correlation was observed between different radiation levels and the amount of beech regeneration, which suggested that young beech seedlings have the ability to survive in a wide variety of light conditions from heavy shade to open conditions. In this way, the whole gap area, including its surroundings, are potentially suitable for beech regeneration.

Gaps clearly provided conditions suitable for the rapid growth of tree seedlings and ground vegetation. Where the ground vegetation became abundant, it generally had negative effects on tree seedlings, competing with them for light and soil nutrients and water, and also by physically suppressing their upward growth and branch development. However, in some cases, the ground vegetation was thought to have positive effects, by providing protection against high temperatures, photo-inhibition, browsing and other harmful agents.

At the central and south Europe study sites, up to 70,000 beech seedlings per hectare were counted: beech regularly regenerates vigorously and dominates young stands with little competition. However, at the north and northwest European study sites, beech seedlings were less frequent with counts of <20,000 per hectare.

Common problems recognised widely were: (i) excessive browsing (mainly by deer), which not only results in fewer beech seedlings but also reduces the potential quality of those that survive; and (ii) excessive competition from ground vegetation, especially on fertile sites and in larger canopy gaps.

Problems distinctive to north and north-west Europe were: (i) scarcity of natural regeneration, related to predation of seeds and seedlings, infrequent mast years, damage to seedlings by late-spring frost and summer drought; (ii) lack of knowledge and experience in using natural regeneration rather than planting; and (iii) lack of sustained long-term management towards natural regeneration, due to fragmentation of ownership and presence of industrialised forestry concepts and practices. A major problem identified in south-Europe was undesirable architecture of beech seedlings, which results in low quality beech timber when applying small-scale management systems.

Despite the problems encountered, the results show that natural regeneration of beech can be an effective tool in restocking forests. The gap studies has in this regard provided a basic template for using gap cutting practices in promoting natural regeneration in beech forests managed under nature-based forest management regimes.

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Reported by

Dept. of Forestry and Renewable Forest Resources, University of Ljubljana
Vecna pot 83
1001 Ljubljana
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