DIRECT CONTRIBUTION BY SOIL ARTHROPODS TO NUTRIENT AVAILABILITY THROUGH BODY AND FECAL NUTRIENT CONTENT

The direct contribution made by soil arthropods to nutrient dynamics was investigated in pine forests that differed in soil nutrient status. Nutrient concentrations (K+, Ca2+, Mg2+, PO43-, N, C) in the most abundant species and groups of arthropods in two Pinus nigra forests were compared, and distinct differences were found among taxonomic groups. In the rank order: collembolans, oribatides, isopods, diplopods, Ca2+ and Mg2+ concentrations increased, while N and C concentrations decreased. The nutrient concentrations in individuals of the same species but originating from the different forests were similar, except for the isopod Philoscia muscorum. The total and available nutrient concentrations in food and faeces of the collembolan Tomocerus minor and the isopod Philoscia muscorum were compared. The isopod faeces contained relatively less K+ and Mg2+ and more Ca2+, PO43-, and greater N availability, compared with the food material. The collembolan faeces showed a higher availability of all nutrients measured. The N species appeared to be changed by collembolans; their faeces contained high NO3- concentrations, while their food contained relatively high concentrations of NH4+. These findings were examined in relation to their significance for ecosystem functioning. It was concluded that about 12% of the total K+, PO43-, N and 2% of the Ca2+ in the organic layer was found in the mesofauna. It was calculated that faeces production by the collembolans resulted in a 2.4 times higher NO3- availability in the forest floor.