Vertical rooting patterns of mature Quercus trees growing on different soil types in northern Germany

Abstract

At two different sites in northern Germany, the vertical distribution patterns of roots with diameters of up to 10 mm were investigated with the trench profile wall technique beneath mature trees of Quercus petraea (Matt.) Liebl. growing on clayey (cambi-stagnic gleysol) or sandy soil (dystric cambisol). The rooting patterns were related to soil bulk density, maximum plant-available soil water and soil chemistry, and were compared with the rooting pattern of Q. petraea growing on a silty soil on limestone (luvisol) and with that of Q. robur L. growing on clayey loam (stagnic cambisol). All three Q. petraea sites differed in their vertical rooting pattern, as was indicated by significant differences in the parameter β which was calculated from the cumulative root fraction (Y) for the cumulative rooting depth (d; Y=1−β^d). At the clayey site, a relatively large fraction of roots was found in deeper soil layers (highest β value); whereas, at the silty site, the rooting pattern was most superficial (lowest β value). No significant difference in the vertical rooting pattern was observed between Q. petraea and Q. robur growing on clayey soil. The soil-area related biomasses of living roots did not differ between the clayey and the sandy site of Q. petraea.Comparisons of the rooting patterns with soil water relations and soil chemistry lead to the hypothesis that under the climatic conditions of Central Europe, the vertical root distribution of Q. petraea is more influenced by the availability of nutrients, especially that of nitrogen, than by the amounts of plant-available soil water.