A dendroecological comparison of two Miombo woodlands under differing anthropogenic disturbances in Zambia
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The Miombo woodlands of interior Africa are fire adapted ecosystems with a relatively open canopy dominated by Brachystegia spp., Julbernardia spp., and Isoberlina spp. These ecosystems are threatened due to deforestation, habitat fragmentation, and impacts from climate change, and in Zambia, they are further threatened by the rapidly growing mining industry which contributes to air pollution, contamination of soils and water, and land degradation. In this study, we used modified variable area transects to determine stand structure of an old-growth, unlogged, but fire-excluded Miombo woodland and at a degraded and recently logged Miombo woodland near Kitwe, Zambia. At the old growth woodland, we developed local chronologies for 10 species. The site was dominated by Julbernardia paniculata (2000+ stems/ha). Using establishment dates, we identified a significant shift in the species composition associated with fire exclusion. The degraded site was comprised of a monoculture of Albizia adianthifolia (3000+ stems/ha). Seedlings and juveniles had the highest densities (450-800 stems/ha). We were unable to develop a chronology for the species due to a lack of definitive annual ring boundaries. Our results describe the characteristics of two different degraded Miombo woodlands, showing how different anthropogenic disturbances (fire-exclusion vs. logging) lead to a transformation of the species composition and affect the trajectory of the ecosystem. Additionally, this research contributes to a growing body of chronologies for the African continent, the least sampled continent for dendrochronological research.