The impact of the common vole on the vegetation of agroecosystems

Abstract

Abstract An estimate was made of the effect of a population of the common vole Microtus arvalis (Pallas, 1779) on the crop production of a group of cultivated fields in an area forming 3100 ha of typical agricultural land in the Wielkopolska region of Poland, analysis variations in population density of this species, the composition of its food, the capacity for regeneration of different species of plant and the proportion consumed from the whole biomass of eliminated plants. It was found that the vole is able to reach considerable density in about only 19% of the study area (lucerne, meadows, fringes of shelterbelts), in about 48% occurs regulary but not very numerously (chiefly in cereal crops) and usually does not occupy 23% of the region (root crops, maize, wooded land). It occupies lucerne crops in the greatest numbers, since 74% of all voles present in cultivated fields live in lucerne, which forms 8.5% of the whole of the area. During the year, depending on the phase in the cycle of variations in numbers, voles remove from 1.6 to 45.8% of the biomass of primary production from an average hectare of lucerne. This species is not of economic importance in other crops, since on an average it eliminates about 1% of primary production (winter cereals, rape), or 0.1% (spring cereals). In the study area the vole population eliminated from 0.2 to 6.4% of primary production from an average hectare of cultivated crop. The animals were found to show preference for feeding on weeds in a cultivated area. The effect of the common vole on the crop yield of cultivated plants depends on its density and to a great extent the duration of its effect on a plant, but to a lesser degree on the amount itself of biomass eliminated. Damage is chiefly caused by the voles feeding on lucerne in summer and autumn, on cereals in late spring and summer, and on rape from autumn to late spring. At other times there is strong regrowth of plants, which compensates to a great degree for the losses caused by nibbling rodents. The estimates obtained for amount of damage caused by the vole in crops in relation to income from plant production on the local State Farms are from 0.5 to 16% (in average years 3.5%). In this value as much as 97% of losses are due to the vole population's activities in lucerne crops.