The relationship between N mineralization or microbial biomass N with micromorphological properties in beech forest soils with different texture and pH

Abstract

To test relationships between net N-mineralization, organic matter and soil organisms, we combined micromorphology with laboratory incubation experiments over a soil gradient. Microbial biomass N generally increased with pH, and from sandy to loamy soil, but net N-mineralization showed the opposite, and was highest in acid, sandy soil. Twenty-two micromorphological characteristics were analyzed with principal component analysis. PC1 had high eigenvalue (0.70), and clearly separated fungi from earthworms, microarthropods and bacteria. PC2 was less important (0.15). Organic layer and sand content clearly correlated with the fungi-end of PC1, but pH and C-content of the Ah with the opposite. Microbial N also correlated with the earthwormbacteria end, but net N-mineralization did not. Efficiency of N-mineralization per unit microbe even correlated with the fungi end of PC1, in both organic layer and mineral topsoil. The results support the hypothesis that high (or low) litter turnover and biological activity can be counteracted by high (or low) microbial N-demand.

The influence of environmental variables on soil mite communities (Acari: Mesostigmata) from overgrazed grassland ecosystems – Romania

“…In contrast, some other research has found that these invertebrates prefer a lower pH, which is favourable for the development of fungi, the food source for other soil invertebrates which in turn form the prey for mesostigmatids (Chikoski et al 2006;Manu 2011a;Birkhofer et al 2012). Acidity and dominance of sandy soils (such as those described from the six grassland ecosystems in the present study) are known to contribute to low actinomycete biomass (Kooijman et al 2009;Birkhofer et al 2012).…”

Plant nutrient mobilization in temperate heathland responds to elevated CO2, temperature and drought

“…These observations of decreased P availability are in contrast to effects of CO 2 fumigations at other soil types (Ebersberger et al 2003;Khan et al 2008). The sensitivity in soil P availability to enhanced CO 2 might, however, be soil specific and related to soil pH, contents of ion, aluminum and other adsorbing minerals important for soil P chemistry (Britton et al 2003;Chapin III et al 2002;Kooijman et al 2009). In studies with shortterm treatments, pulse releases of P after drying and rewetting of soils were observed but with no relation to microbial biomass C (Blackwell et al 2009;Butterly et al 2009).…”

Changes in nutrient availability from calcareous to acid wetland habitats with closely related brown moss species: increase instead of decrease in N and P

“…In terrestrial soils, increase in net N-mineralization from high to low pH seemed associated with a shift in microbial community (Kooijman et al 2008(Kooijman et al , 2009). Bacteria usually predominate at high pH, and fungi under more acid conditions (Bååth and Anderson 2003).…”