The role of soil biota and plant/biota interaction in aggregate formation and soil profile development
Plant-soil interactions can be realised via interaction of plant roots with associated microbial symbionts as well as by interaction of plant litter with litter associated soil biota. The latter interaction pathways are the subject of this research programme. Processing of leaf litter affects release of nutrients but also formation of soil aggregates and consequently formation of whole soil profile. These processes connect composition of soil biota community with plant litter quality on one side and nutrient cycling and soil formation on the other side. We determine the changes of aggregate formation and soil profile development in soils under various plant species. We characterise the effect of aggregate formation on soil microbial community. And finally, we characterised the effect of soil development on plant growth.
What major biotic and abiotic factors determine formation of soil aggregates in particular? We want to explore interactions between plant roots, fungi, bacterial soil fauna and soil physical properties namely clay content. We expect that the role of individual biotic factors affecting the formation of aggregates vary between various ecosystem.
We use two basic approaches: (i) manipulation experiment in which formation of soil aggregates and soil profile are observed in field and (ii) laboratory microcosms experiment in which litter quality, soil properties (namely clay content) and composition of soil biota community are manipulated. Alternatively, we use several well defined chrono-sequences (such as those described by Frouz et al. 2008) and common garden experiment for which we know development of vegetation, soil microflora and soil fauna. In common garden experiment we use plots planted by single species in post mining overburden. These sites allow to determine effect of individual species on soil and aggregates formation [Frouz et al. 2013]. Combination of manipulation experiments in all available spatial scales and chronosequence studies allow to understand mechanisms of soil aggregates formation in details as well as verifying applicability of these mechanisms into field context.
The micro- and macroaggregates are separated using a fractionation procedure according to [Six et al. 1998; 2000]. Fractionation procedure according to [Zimmermann et al. 2006; 2007] is used to divide fractions according to OM availability. Total C and N content are estimated using a CHN analyser (solid state) or TOC analyser (liquid state) namelly in HWC extracted from soil samples. OM quality is characterized using traditional chemical methods [Sparling et al. 1998] and compound specific IRMS (both the natural abundance and trace labeling method are used). Microbial biomass and diversity analyses are routinely performed using biochemical markers. Phospholipid fatty acid (PLFA) analysis is used to determine total microbial biomass and to characterize the content of fungal and bacterial biomass. Neutral lipid fatty acid (NLFA) analysis is used for AMF abundance. Fungal and bacterial community composition and diversity are also analysed using the next-generation-sequencing approaches.