ALLELOPATHIC INFLUENCE OF ACER NEGUNDO L. ON SOIL ENZYMATIC ACTIVITY IN NATURAL PLANT COMMUNITIES
The enzymatic activity of soil under the influence of an invasive species Acer negundo was studied. The research targets were chosen taking into account the planting rating in terms of crown density. The soil samples were taken depending on horizontal differentiation of the plant communities in the internal, transitional and external zones of phytogenous fields. The content of soil enzymes, metabolites of the activity of Acer negundo as community edificator, at the beginning, in the middle, and at the end of the growing season was studied. Increased enzymatic activity during active tree growth in variants and in the control was revealed. Among the enzymes, the activity of invertase prevails over that of protease and phosphatase. The increased intertase activity was revealed under the cover of single trees (38.27-60.79 mg of glucose per 1 g of soil per 24 h); in close plantings, lower value was revealed (29.91-51.51 mg of glucose per 1 g of soil per 24 h). Protease enzyme is an integrated indicator of decomposition of nitrogen-containing organic compounds; its greatest activity was revealed in the middle of growing season, especially at single trees in the internal and transitional zones (4.37 and 4.65 mg of glycine per 1 g of soil per 24 h, respectively). In terms of phosphatase activity, the average level was revealed. The greatest differences from the control (by 14-21%) were revealed in the stands of average and high density. Consequently, single trees of Acer negundo which form around themselves concentric expressed phytogenous fields have the greatest allelopathic influence on soil activity.