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Spider Abundance in Relation to Needle Density in Spruce

Iréne Sundberg and Bengt Gunnarsson
The Journal of Arachnology
Vol. 22, No. 3 (1994), pp. 190-194
Stable URL: http://www.jstor.org/stable/3705421
Page Count: 5
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Spider Abundance in Relation to Needle Density in Spruce
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Abstract

The effect of micro-habitat change, caused by needle-loss, on spiders living in spruce (Picea abies) was examined in a field experiment. Abundance and size distribution of spiders on spruce branches were recorded at the start and at the end of the experiment. All spiders and approximately 24% of the needles were removed from the experimental branches. In the control branches, the needle density was left unaltered but the spiders were removed. There were no initial differences in the spider community on the selected branches. Spiders were collected after seven weeks of colonization on control and needle-thinned branches, respectively. The mean density of spiders was significantly lower on needle-thinned branches (78%) than on control branches. This was shown to be an effect of reduced density of large (length ≥2.5 mm) spiders, but not of small (≤2.5 mm) ones. However, the total size distributions did not differ between the branch categories. The field experimental data confirm earlier results in laboratory studies and natural populations.

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