Carlesso, Lea
(2019)
Functional interactions between management of arable field margins and soil mesofauna.
PhD thesis, University of Nottingham.
Abstract
The damage to soils caused by agricultural intensification greatly affects belowground faunal communities, typically via a reduction in population size and diversity in comparison with those in semi-natural habitats. This can cause an imbalance in associated soil functions. The soil mesofauna, including Acari (mites) and Collembola (springtails), fulfil a wide range of these functions and our understanding of soil processes is closely linked to our knowledge of the dynamics of invertebrate communities. In the context of current global change, sustainable food production is a significant challenge that can potentially be better met by improved understanding of the abundance and composition of the soil mesofaunal populations, in order to optimize ecosystem services delivered by agricultural soils.
This PhD project addressed this issue by investigating the changes induced by sown grass field margins on the abundance of populations and community structure of soil mesofauna in the context of arable fields. It aimed to understand to what extent field margins affect soil mesofauna communities and whether these effects extend into the adjacent crop. To do so, the project investigated: (i) the nature of the ecological succession of the mesofaunal populations in relation to time since establishment of the margin; (ii) the impact of field operations on the abundance and structure of the invertebrate communities, regarding the effects of the margin; (iii) whether faunal-driven soil processes, such as decomposition, are affected by field management (establishment of field margins) and field operations (traffic; restitution of crop residues); (iv) the impact of historical landscape management on current biodiversity markers. To answer these questions, field margins, on two UK farms which work with BASF to demonstrate sustainability in Agriculture, that had been established for different durations (1, 6 and 10 years) were investigated and changes in structure and population sizes of invertebrate communities associated with these field margins and their adjacent crop areas were studied over two years. Soil mesofauna were sampled, counted and identified from the various field margins of different ages, with differing orientations regarding the field traffic, and their adjacent crop.
It was found that population abundances and complexity of the community structures were generally enhanced in the field margins: more invertebrates and complex communities were found in the margins than in the adjacent crops. Likewise, community composition in the margins changed over time toward larger organisms and specialist species. Although it was hypothesised that mesofaunal populations in the crop would be influenced by the presence of the margin (the closer to the margin, the more similar the composition), it was found that field management was also an important driver of the soil mesofaunal communities. In the cropped areas, the heterogenous distribution of species abundances and the differences in community structure reflected the degree of disturbance caused by the different agricultural activities, such as tillage practices, management of crop residues or wheeling from field traffic. The ability of certain groups of soil invertebrates to disperse, and colonise new habitats was revealed; for example, at the margin:crop interface where there are compacted, traffic-related 'tramlines', abundances were particularly low while further into the field in less-disturbed areas, populations were more abundant.
The interaction effects between field margins, within-field crops and farm management highlighted the importance of well-designed and integrated agricultural strategies to maximise soil functions contributed-to by the soil fauna, such as litter decomposition and nutrient cycling, which in turn provide ecosystem services, such as maintenance of the soil fertility and structure, essential to sustainable food production.
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