DISTRIBUTION OF NUTRIENT ELEMENT RESERVES IN A POORLY GROWING 100-YR-OLD NORWAY SPRUCE STAND ON AN ACID SANDSTONE (BUNTSANDSTEIN) SITE

Reserves and distribution of nutrient elements N, P, S, K, Ca, Mg, Na, Fe, Mn, Cl, and Al were determined in a pure stand of poorly growing Norway spruce (Picea abies [L.] Karst.) on an acid sandstone (Buntsandstein) site located in the eastern Black Forest (SW Germany). The inventory based on the analysis of two trees of mean basal area included the following components: heartwood, sapwood, bark, branches, twigs, current needles, older needles, and lichens. Crown components were differentiated into sun-exposed and shaded parts. The assessment of the belowground dendromass was achieved by total excavation of one of the sample trees. Roots were sampled by soil layers and divided into seven diameter classes. The inventory of the element pools in the soil was done separately for the forest floor and the intensively and extensively rooted mineral soil, respectively. The aboveground biomass totals 250 metric tons dry mass per hectare, the belowground biomass 65.5 t.ha-1, representing a shoot:root ratio of 3.8. In the aboveground tree components, elements are distributed primarily according to nutrient requirements. Depth distribution of element contents in the fine roots reveals a distinct relationship to the supply in the soil. In general, a poor nutrition of the stand with N, P, K, Ca, and Mg emerges. This is attributed to the excesive management practices in the past. In the case of K, Mg, and Ca, accumulation in the dendromass clearly exceeds the reserves available in the intensively rooted upper soil. Although N-reserves are normal, N-availability is low due to an impaired mineralization of organic matter. The same is true for P. Calculations of the element removal by different harvesting systems illustrate that on this nutrient-depleted site even conventional removal of stemwood means a substantial loss of nutrients. Thus, more intensive harvesting systems (tree-length, whole-tree logging), which represent an up to 10 times higher removal of nutrients in the harvested crop, are not advisable. A combined application of dolomitic limestone and potassium phosphate is recommended in order to improve the nutrient supply. For an appropriate long-term management of this problem site, silviculture should favor fir and pine as tree species, which develop deeper root systems.