Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Evaluation of plant-grazer-soil interactions and agroecosystem carbon cycling properties in California perennial crop-livestock systems

Auteur : Brewer, Kelsey

Université de soutenance : University California Davis

Grade : Doctor of Philosophy (PhD) 2022

Résumé partiel
One historically foundational, yet scientifically understudied, agroecological diversification strategy is the integration of animals and crops within the same production system. Integrated crop-livestock (ICL) systems, where animals provide various grazing-based services for crop production and the diversification of on-farm income, are common across much of the world’s subsistence farming communities. Global practitioners of ICL management rely on extensively developed local and indigenous knowledge systems, with regional specificity and complexity in the coordination of components. However, the industrial intensification of agriculture, especially throughout the last century, has increasingly resulted in highly specialized, mechanized, and de-coupled crop and animal production throughout much the world’s market-based agricultural systems. This is currently understood to contribute to poor nutrient (re)cycling within and between agricultural operations, higher rates of external input, reduced adaptive capacity, and an increased environmental footprint (GHG emissions, land-use conversion, etc.) of both crop and animal productions. However, much of these dynamics remain underexplored and the potential for SOC storage remains largely unknown. The goal of the research presented here was to narrow critical knowledge gaps specific to perennial ICL management outcomes, especially as they relate to soil nutrient cycling and carbon flux and storage dynamics within semi-arid climates. Collectively, the experiments in this study aim to observe perennial ICL outcomes across both spatial (i.e. bulk vs. rhizosphere soils) and temporal (i.e. long-term vs. short-term adoption ; intra-seasonal vs. inter-seasonal monitoring) scales. The value of this information is in validating the potential usefulness of ICL for the purposes of energy and nutrient cycling, soil carbon sequestration, and the provisioning of other key soil ecosystem services. More specifically to the cycling of carbon, this research explored if and how these more complex and diversified ICL systems impact : (1) functional traits of the forage plant community ; (2) soil physicochemical characteristics ; (3) recycling and retention of carbon and nutrients ; (4) soil biological activity and carbon substrate utilization ; and (5) SOC biochemical and physical partitioning into storage pools. This information is critical for informing future integrated-systems research platforms and management applications ; toward the goal of developing ICL production models with well-coordinated and strategically applied grazing practices. To carry forth this work, a comprehensive review of ICL literature was first conducted (Chapter 1). The broad aim of this review was to identify the status of ICL research, especially as it pertained to biogeochemical dynamics of carbon and nutrients within agroecosystems. Whereas the state of ICL literature is currently scarce, the aim of this review shifted toward providing a perspective and the development of working hypotheses and potential mechanistic frameworks

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