Abstract: The accumulation of phenolic acids in monocultured strawberry soils and their effect on the numbers of total nematodes and bacterial-feeding nematodes were investigated. The effects of exogenous phenolic acids on the numbers of total nematodes and bacterial-feeding nematodes were also examined. With the increase of continuous cropping years, the content of phenolic acids in the soils increased while the numbers of total nematodes and bacterial-feeding nematodes decreased, with the lowest numbers being obtained in the monocultured strawberry soil continuously cropped for 5 years. There was a negative correlation between the content of phenolic acids and the numbers of total nematodes or bacterial-feeding nematodes. The numbers of total nematodes and bacterial-feeding nematodes increased when the addition of phydroxybenzoic acid or pcoumaric acid into soil not in monoculture was below 200 μg·g^-1 but decreased when the addition was above 200 μg·g^-1. A similar pattern was also observed in cinnamic acid test with a different threshold of 100 μg·g^-1. Numbers of total nematodes and bacterialfeeding nematodes decreased when a concentration of higher than 100 μg·g-1 of ferulic acid was added into soil. Numbers of total nematodes and bacterialfeeding nematodes decreased with the increase in concentration of mixed phenolic acids.

Key words: NDVI, vegetation dynamics, climate change, permafrost degradation.