The first quantitative taxonomy of phytoliths from Miombos is presented here, including new types and constituting the most extensive phytolith key for any African ecoregion. Evidence is presented that local woody species are hypervariable silica producers and their phytolith morphotypes are highly polymorphic. The taxonomic significance of these phytoliths is largely poor, but there are important exceptions that include the morphotypes produced by members from >10 families and orders. The typical phytolithic signal that would allow scientists to identify ancient woodlands of 'Zambezian' affiliation comprises only half of the original number of phytoliths originally produced and might favour the more resilient blocky, cylindroid, globular and tabular forms.

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This paper describes topsoil phytolith assemblages from 25 loci underneath miombo woodlands on an eco-transect intersecting the Mozambican Rift along a geographical, altitudinal, climatic and botanical gradient. We provide the first comprehensive overview of the phytolith spectrum that defines northern Mozambique's Zambezian floristic zone. Our classifying criteria derive from comparison with previously described and quantified reference collections of trees and grasses growing in the study area. We characterize the sedimentological and soil features of the matrices where phytoliths are found, establishing correlation among geo-edaphic variables and phytoliths. Descriptive statistics along with nonparametric and parametric statistical analyses evaluate phytolith grouping criteria, variation, robustness, and membership. From a taphonomic perspective, we attest that topsoil phytolith assemblages are polygenic and do not represent an episodic snapshot of extant vegetation, but a palimpsest from plants representing various disturbance episodes, succession stages, and ecological trends. Phytoliths retrieved from Mozambican miombo soils do not seem to trace altitudinal, temperature, or precipitation gradients, and no significant differences exist between highland and lowland phytolith assemblages. This article provides a phytolith analog for woodland environments that can guide future paleoenvironmental research. It also confirms that phytolith analysis is able to detect shifts in the woodland/grassland interface.

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