The effect of femel- and small scale clear-cutting on ground dwelling spider communities in a Norway spruce forest in southern Germany

Published source details Huber C., Schulze C. & Baumgarten M. (2007) The effect of femel- and small scale clear-cutting on ground dwelling spider communities in a Norway spruce forest in southern Germany. Biodiversity and Conservation, 16, 3653-3680.
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Summary

In southern Germany, Norway sprucePicea abies has largely replaced native broadleaf beech Fagus sylvatica dominated forests. These conifer stands have relatively low value for nature conservation, therefore a goal of forest management in Bavaria is to revert these monoculture stands to mixed forest. From 1987 to 2002, the proportion of areas with broadleaf trees increased from 22 to 32% with a view to further future increses. There are generally two methods used in this region for stand conversion: private forest owners make small clearcuts (all trees removed with a resultant increase in temperature and decrease in shade) between 0.5 and 1 ha in size; the Bavarian state forest administration regenerates stands by 'femel cutting', a strategy to maintain a forest cover during the regeneration phase; over 10-15 years trees are selectively felled, while deciduous saplings grow under the cover of the remaining canopy. Final spruce removal will be done when the saplings are well established. The impacts of these management options on forest ecology are unclear. Femel-cutting is thought to have a lower impact on faunal groups and may maintain biodiversity in managed forests. However, until now, studies on the ecological effects of femel-cutting are scarce. This present study investigated the influence of these two conversion methods on spider communities.

Study site: The study was conducted at Höglwald (11˚04'E, 48˚17'N), at a long-term ecological experimentation site (370 ha) situated 50 km west of Munich in southern Bayern, Germany. The stands were mature Norway spruce plantations established in 1910/11.

Experimental treatments and plots: In 1999 plots were installed prior to cutting treatments, which were undertaken in February 2000. Trunks were removed but slash was left. In an area with a uniform stand and site conditions the treatments were:

control plot - spruce uncut
femel-cutting - 20% of trees (0.9 ha), regeneration with planted beech saplings
CC - small scale clear-cut (1 ha) divided into:
CCB - clear-cut, regeneration with planted beech saplings (0.5 ha)
CCS - clear-cut, regeneration with natural (5-10-year old spruces) or planted spruce saplings (0.5 ha)

Five-year-old saplings (beech or spruce) were planted in March 2000.

Spider sampling: Spiders were collected at each treatment with a combination of 10 pitfall and six emergence traps during the pre-treatment year, the year of cutting, and the year after cutting. The trapping period covered May-October, sampling three times a year (spring, summer and autumn). The traps were emptied 2 weeks after installation. All captured animals were preserved and assigned to taxonomic groups. Spiders were identified where possible to species level.

In total 7,101 individual spiders (4,530 identified comprising 107 species) were collected; 4,468 were adult and 2,633 juvenile. A single species, Coelotes terrestris, dominated the control (uncut spruce stand) comprising up to 49% of the total identified.

Clear-cutting resulted in a dramatic change in species composition; the number of individuals of the families Linyphiidae, Amaurobiidae, Agelenidae and Clubionidae decreased drastically within the 2 years after clear-cutting, whilst Lycosidae became numerically dominant. Small (<3 mm) and large spiders (>10.5 mm), web builders, ‘forest habitat species’, species favouring hygrophilic to medium moisture conditions, and preferences to live below ground or in and on the moss layer, all decreased significantly in numbers. Middle-sized spiders, free hunters, ‘open habitat species’, spiders favouring dry conditions or that are euryoecious, preferring patterns covered by grasses or uncovered patches, increased. Clear-cuts with dense spruce regeneration showed a delayed and less pronounced response. The first step in femel-cutting retained the ground-living spider forest community

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http://www.springerlink.com/content/085787j080444777/fulltext.pdf