SOIL FAUNA INCREASE BETULA-PENDULA GROWTH - LABORATORY EXPERIMENTS WITH CONIFEROUS FOREST FLOOR

The effects of soil fauna on the growth and nutrient contents of birch seedlings were studied in laboratory microcosms simulating the complexity of a coniferous forest floor. In one set of microcosms partially sterilized soil was reinoculated with soil microorganisms only; another set was reinoculated with microorganisms and a diverse soil fauna. A birch seedling (Betula pendula) was planted in each microcosm, all of which were incubated in a climate chamber with various temperature and illumination regimes. During two growing periods birch-leaf, stem, and root biomasses were 70%, 53%, and 38% greater, respectively, in the presence of fauna. The N and P contents of leaves were almost-equal-to 3- and 1.5-times higher, respectively, in the refaunated microcosms than in the controls with microorganisms only. The amount of K, Ca, and Mg in leaf tissue were almost the same in both treatments. Despite the greater leaf biomass, and therefore more effective transpiration, the water content of the soil remained significantly higher in the refaunated microcosms. The results clearly indicate that soil fauna, via enhanced nutrient mobilization and favorable changes in the structural soil properties, exert a positive influence on plant growth.