Abstract
Over geological timescales, the functions and shape of the Earth’s critical zone (CZ), the region that extends from the top of the vegetation canopy to the bottom of the weathering zone, have been governed by its responses to natural (tectonic and climatic) forcings. Recently, however, anthropogenic activities, occasioned by increasing population (human and livestock) and demand for resources such as food and fibre, have emerged as major drivers of changes in the critical zone. This demand for resources has led to unsustainable land use practices and loss of soil quality especially in karst environments where lithology contributes to the slow formation of nutrient deficient soils.This thesis investigated the impacts of anthropogenic activities and bedrock lithology in the production, distribution, and bioavailability of mineral nutrients in two karst CZs in Guizhou, China and Crete, Greece, both impacted by intensive agricultural activities but under different timescales and seasonality.
This thesis identifies lithological control on the production, distribution, and abundance of the bulk and bioavailable mineral nutrients in both CZs. In addition, this thesis also identifies the influence of atmospheric dust deposition to the abundance and distribution of bulk mineral nutrients consistent with earlier findings and establishing that bedrock age and climate variability have no significant influence in the production of mineral nutrients in these carbonate environments.
The thesis also establishes that lithology and atmospheric deposition control the abundance and distribution of bioavailable mineral nutrients in both CZs. However, atmospheric deposition is more prominent in the Greek CZ than the Chinese CZ. Recovery of mineral nutrient bioavailability after perturbation was also established to take longer than 5 years, which has previously been shown for forested, silicate bedrock soils, but not agricultural, carbonate bedrock soils.
| Date of Award | 12 May 2022 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Penny J Johnes (Supervisor) & Heather L Buss (Supervisor) |