Relationships of soil microarthropod biomass with organic matter and pore size distribution in soils under different land use

Abstract

Soil microarthropods were sampled every 3 months for 1 y at 10 sites in the northern Netherlands, varying in soil type and land use. Microarthropods were divided into seven functional groups and biomass-C ha −1 was calculated for the top 10 cm soil layer. The four quantitatively principal functional groups were: cryptostigmatic mites; non-crytostigmatic mites; predatory mites; and omnivorous collembola. Possible relationships between the mean annual biomass of these groups and soil type, land use or soil organic matter were studied. Microarthropod biomass was larger in sandy soil than in loamy and generally larger in meadows than in wheat fields; the mineral layer of forest soils being intermediate. Non-cryptostigmatic mite, omnivorous collembola and predatory mite biomass showed strong positive correlations. Cryptostigmatic mite biomass correlated with lower organic matter input quality, while omnivorous collembola and non-cryptostigmatic mites showed a positive correlation with the amount of input. Omnivorous collembola were negatively affected by a discontinuous input of organic matter to the soil. We found relationships between functional group biomass and either soil organic matter density fractions or soil pore size distribution only when the grassland sites were analyzed separately. Both analyses showed correlation patterns for cryptostigmatic mites to deviate from those of the other three main functional groups. Cryptostigmatic mites showed a positive correlation with the lightest organic matter density fraction, while the non-cryptostigmatic mites and omnivorous collembola were correlated to the heavier fractions. The cryptostigmatic mites correlated with the 6–90 μm pore size class, while the other three groups showed strong correlation to the 1.2–6 μm, as well as the largest (> 90 μm) pore size class. Both observations lead to the conclusion that omnivorous collembola and non-cryptostigmatic mites are related to fungal growth (in the largest pores and on the heavy organic matter fraction), while the cryptostigmatic mites show a more saprovorous feeding mode.