Investigations on the root distribution of differently foliated beech trees - A case study

In the late summer of 1991 many mature beech trees were found, on a number of sites in the forest district ''Siegen-Nord'', to have extremely sparse leaf cover while fully foliated ones grew next to them. As no signs of biotic damage were found at the above ground around the sparsely foliated beech trees it was assumed that the root system might be disturbed. To investigate this root ditches were excavated around a sparsely and a fully foliated beech tree (A and B respectively) situated no more than 10 m apart and both, root distribution and soil morphology, were recorded. The result of this investigation demonstrated chat beech A had developed a shallow and tree B a deep root system. The shallow root system of beech A may be due to a soil horizon showing typical stagnic colour patterns resulting in temporary reducing conditions directly under this tree. Thus the vertical soil volume that beech A can use for its water supply is considerably smaller than that of beech B which rooted significantly deeper, enabling it to use the soil water supply at these deeper levels even in periods of drought. The sparse leaf cover of beech A may thus be the result of the tree's insufficient water supply in the dry summer of 1991. This assumption is supported by the fact that beech A had formed significantly more fertile buds than did the fully foliated beech B.