Understanding communities in complex agroforestry systems: methodological advances and ecological implications

Jarrett, Crinan (2022) Understanding communities in complex agroforestry systems: methodological advances and ecological implications. PhD thesis, University of Glasgow.

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Agroforestry, the practice of growing crops beneath a canopy of shade trees, is common in tropical regions, and has the potential to provide habitat for wildlife whilst maintaining agricultural production. However, the increasing demand for commodity crops is driving intensification of agriculture in the tropics, which results in the conversion of agroforestry systems into monocultures. This conversion to monocultures drives declines in biodiversity in these habitats, which may in turn cause a drop-off in yields due to loss of ecosystem services. However, the effects of agricultural management on animal communities and the downstream effects on productivity are poorly understood, especially in the Afrotropics.

This project aimed to study the influence of farm management on wildlife communities, and the potential implications for productivity, in African cocoa agroforestry. My research was based on data of bird and arthropod communities in 28 cocoa farms in southern Cameroon. The study farms varied in their shade cover (a proxy for management intensity), from 20% to 100% cover. In these farms we surveyed arthropods using visual surveys, sweep-netting and malaise traps, and birds using mist-netting and acoustic recorders. I investigated trends in bird and arthropod community composition using several statistical methods, including data integration, hierarchical modelling and community modelling.

My results show that the shade cover of farms had a strong influence on animal community composition. Shady (low-intensity) cocoa farms supported higher densities of vulnerable rainforest bird species such as ant-followers and forest specialists. Shady farms also contained higher densities of potential pollinators and natural enemies, and lower densities of pest insects. I investigated the interplay between shade management and interspecific interactions, and found that both these factors were important in shaping communities in these complex agricultural habitats.

Overall, my results indicate that low-intensity management of agroforestry may be beneficial for both biodiversity conservation and productivity, as it favours populations of vulnerable species and ecosystem services providers, whilst reducing pest burdens. These findings shed light on the risks associated to the current push towards intensification of agriculture in the tropics.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Funding support provided by the Royal Society of Edinburgh and the Carnegie Trust for the Universities of Scotland.
Subjects: S Agriculture > S Agriculture (General)
Colleges/Schools: College of Medical Veterinary and Life Sciences > Institute of Biodiversity Animal Health and Comparative Medicine
Supervisor's Name: Haydon, Professor Daniel T. and Powell, Dr. Luke L.
Date of Award: 2022
Depositing User: Theses Team
Unique ID: glathesis:2022-83033
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 20 Jul 2022 09:55
Last Modified: 20 Jul 2022 09:57
Thesis DOI: 10.5525/gla.thesis.83033
URI: https://theses.gla.ac.uk/id/eprint/83033
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