Coupling between Extracellular Polymeric Substances (EPS) and Soil Structure in Semiarid Resource Islands
Abstract
Under semiarid climate conditions complex soil-vegetation interactions are present. Individual plant species form so-called resource islands in the barren landscape, whereby many soil properties are enhanced including soil structure. Soil structure, expressed as aggregation and aggregate stability, is important for a wide range of soil functions, including soil aeration and erosion control.
These resource islands are hotspots of microbial activity. Despite the better conditions in these resource islands, the microbial community experiences drought stress on a regular base. To increase their endurance, microbes form a more stable environment in which to live by producing extracellular polymeric substances (EPS). EPS consist mainly of exopolysaccharides, proteins and other molecules like DNA. This EPS forms a biofilm on mineral surfaces, in which nutrients and water is stored. The effects of EPS on aggregate stability seem to be twofold, as it adsorbs to mineral surfaces and forms bridges between mineral surfaces. The theoretical effect of this microbial glue on soil aggregation has not well been studied. To examine the role of EPS on soil aggregation, sites were selected on south facing slopes in the Sierrra de los Filabres and Sierra Nevada (Almeria, Spain). This semiarid part of Europe is dominated by a sparse vegetation cover on shallow, poorly developed soils. The upper 10 cm of the soil was sampled over a distance gradient from the dominating Anthyllis cytisoides and Macrochloa tenacissima plant species, up to 70 cm into the bare interspace (n=5). Besides general soil properties, EPS was extracted using a cation exchange resin and its constituents quantified. Furthermore, micro-aggregate distribution and stability will be tested. First results indicated that the closer to the plant EPS-saccharides content became higher in comparison with the easily extractable saccharides content of the soil. It is expected that following this trend the micro-aggregate stability would be enhanced with increasing EPS levels. This relation might be more pronounced around the legumes shrub species Anthyllis cytisoides, as a higher diversity of undergrowth plant species was observed. It seems that microorganisms influenced by plant species are actively involved in soil structure formation by producing EPS.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.B53G2148Z
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCESDE: 0463 Microbe/mineral interactions;
- BIOGEOSCIENCESDE: 0465 Microbiology: ecology;
- physiology and genomics;
- BIOGEOSCIENCESDE: 0466 Modeling;
- BIOGEOSCIENCES