Analysis of soil biota role in key processes of ecosystem functioning across a Mediterranean climatic gradient
Soil is a non-renewable ecosystem resource under seriously pressure by land use, urbanisation and climate change. Soil organic matter (SOM) is key to soil fertility, improving the soil structure and associated soil moisture and aeration processes and, providing nutrients, important for the global carbon (C) cycle, climate change mitigation and combatting land degradation, and the conservation of above- and below-ground biodiversity and associated ecosystem services. The supply of ES is mainly controlled by a suite of factors ranging from abiotic operating at large scales (climate, nature of the bedrock) to biotic with small scale domains (vegetation and soil biota). The SOM is biologically transformed by micro-organisms (bacteria and fungi) and fauna and stabilized in organo-mineral complexes with different turnover rates. The composition and role of soil fauna varies with respect to climate and land use, and they affect the activity and community composition of soil microorganisms in multiple ways such as feeding and changing the biophysical conditions in the soil. Soil fauna, their biodiversity and species traits are crucial for SOM turnover. The important contribution of soil fauna to SOM dynamics has so far been considered mainly by soil ecologists who developed their own models. These describe C dynamics mainly on the basis of trophic interactions (among microbes, micro-, meso- and macro-fauna). The engineering effects of soil fauna through the production of biogenic structures, are not specifically addressed either. Soil food web models are proposed with relatively detailed descriptions of trophic interactions but oversimplifying soil physical and chemical processes, and overlooking the engineering effects of soil fauna. Recent studies and papers still describe microbial participation in soil processes and neglect the important role of large soil invertebrates. The (quantitatively probably) important activity of the functional group of soil engineers is disregarded. Major soil ecosystem engineers create physical domains in soils that have all the characteristics of self-organized systems. SOM is occluded within aggregates, and its physical protection increases the residence time of C in soil preventing its rapid release in the form of greenhouse gases. Soil fauna affect soil structure formation through their burrowing, consumption and excretion activities, significantly enhancing OM incorporation into the soil and macro-aggregate formation. Most of the macro-aggregate structure of soils is dependent on the activities of soil ecosystem engineers and roots. A thorough understanding of aggregate structure and formation, including the role of soil biota is thus necessary in the study of SOM stabilization in soils. In this project through direct field and lab-based experimentation we aim at understanding and clarifying the role of soil fauna in SOM dynamics across land uses in different sites across an altitudinal gradient, from the semi-arid land in the Ebro valley to the upper mountains in the Pyrenees. We also aim at understanding the processes governing soil fauna-microbial-SOM dynamics is essential for managing soil fertility and ecosystem services.
Soil is a non-renewable ecosystem resource under seriously pressure by land use, urbanisation and climate change. Soil organic matter (SOM) is key to soil fertility, improving the soil structure and associated soil moisture and aeration processes and, providing nutrients, important for the global carbon (C) cycle, climate change mitigation and combatting land degradation, and the conservation of above- and below-ground biodiversity and associated ecosystem services. The supply of ES is mainly controlled by a suite of factors ranging from abiotic operating at large scales (climate, nature of the bedrock) to biotic with small scale domains (vegetation and soil biota). The SOM is biologically transformed by micro-organisms (bacteria and fungi) and fauna and stabilized in organo-mineral complexes with different turnover rates. The composition and role of soil fauna varies with respect to climate and land use, and they affect the activity and community composition of soil microorganisms in multiple ways such as feeding and changing the biophysical conditions in the soil. Soil fauna, their biodiversity and species traits are crucial for SOM turnover. The important contribution of soil fauna to SOM dynamics has so far been considered mainly by soil ecologists who developed their own models. These describe C dynamics mainly on the basis of trophic interactions (among microbes, micro-, meso- and macro-fauna). The engineering effects of soil fauna through the production of biogenic structures, are not specifically addressed either. Soil food web models are proposed with relatively detailed descriptions of trophic interactions but oversimplifying soil physical and chemical processes, and overlooking the engineering effects of soil fauna. Recent studies and papers still describe microbial participation in soil processes and neglect the important role of large soil invertebrates. The (quantitatively probably) important activity of the functional group of soil engineers is disregarded. Major soil ecosystem engineers create physical domains in soils that have all the characteristics of self-organized systems. SOM is occluded within aggregates, and its physical protection increases the residence time of C in soil preventing its rapid release in the form of greenhouse gases. Soil fauna affect soil structure formation through their burrowing, consumption and excretion activities, significantly enhancing OM incorporation into the soil and macro-aggregate formation. Most of the macro-aggregate structure of soils is dependent on the activities of soil ecosystem engineers and roots. A thorough understanding of aggregate structure and formation, including the role of soil biota is thus necessary in the study of SOM stabilization in soils. In this project through direct field and lab-based experimentation we aim at understanding and clarifying the role of soil fauna in SOM dynamics across land uses in different sites across an altitudinal gradient, from the semi-arid land in the Ebro valley to the upper mountains in the Pyrenees. We also aim at understanding the processes governing soil fauna-microbial-SOM dynamics is essential for managing soil fertility and ecosystem services.