Avoid rocks with regular shapes although some flat ones are necessary as stepping stones to reach all parts of the scree.
Cover the remainder of the scree bed with a layer of small broken stones - of the same material as the rocks and no more than 2in thick - to raise the surface to ground level.
Where a rock garden or scree is neither possible nor needed, why not build a raised bed for growing alpines?
The investigated screes are formed by andesite, basalt, conglomerate, limestone, phonolite, quartzite, sandstone, granite and other kinds of rock.
scree type (1 = bare scree slopes, 2 = scree slopes partly overgrown by solitary trees, 3 = scree forests, corresponding to a gradient from bare to forest screes); position of pitfall traps along the temperature gradient in scree field (1 = lower margin, 2 = middle part, and 3 = upper margin of the scree); ice formation near the trap (1 = no ice formation, 2 = temporal ice inside scree, melting in summer, 3 = permanent ice forming permafrost-like conditions); typical size of stones in the scree (diameter ranging from 0.
49), implying that traps situated at the lower margin of the screes were often surrounded by permanent ice whereas traps placed at the upper margin were free of ice.
Even if elevations of the sites (270-1550 m) spanned the range of elevations in the Czech Republic almost completely, surprisingly the screes with ice formation were found at rather low elevations; the screes with permanent ice filling were situated at 350-650 m a.
The cluster analysis of samples revealed two distinct groups, indicating that two clearly separated spider communities can be identified in the screes (Fig.
Even if their effect was usually less strong than that of the above mentioned variables, they were still significant, suggesting that species composition and abundance of spiders in screes is affected by numerous factors, often interacting with each other in a complicated way.
The species occurring mainly at the scree surface included Acantholycosa norvegica, Diplocentria bidentata, whereas Porrhomma myops, Rugathodes bellicosus, Meta menardi, Nesticus cellulanus, Wubanoides uralensis were found mainly in the depth of the screes.
We showed that ice is regularly formed in screes also from 270-700 m.