THE INFLUENCE AND COMPARISON OF INDIVIDUAL FOREST TREES ON SOIL PROPERTIES AND POSSIBLE INHIBITION OF NITRIFICATION DUE TO INTACT VEGETATION

Soil properties were found to vary with increasing distance from tree trunks of individuals of the same species, and different species were found to vary in their effects on soil properties. The differences in pH and mineral concentration at different distances from the trunk were often statistically significant even under the same tree. When all species are considered, iron had the least variability at different distances from the trunks of all minerals investigated, followed by potassium. Nitrate nitrogen had the greatest overall variability at different distances from the trunks. Ammonium nitrogen in the soil was always considerably higher than nitrate nitrogen when compared at each distance from the trunk under each species. Low amounts of nitrate nitrogen could not have been due to its uptake by the intact vegetation, because the soil samples were taken before the active growth period. It seems possible that the variable tree litter under different species plays an important role in controlling the soil pH, nitrification, and mineralization. Thus, it appears that in a climax community different dominating species, by developing variable physio-ecological niches, can determine the variable undergrowth vegetation under them.