Abstract
AbstractAimAmazonian forests predominantly grow on highly weathered and nutrient poor soils. Anthropogenically enriched Amazonian Dark Earths (ADE), traditionally known as Terra Preta de Índio, were formed by pre‐Columbian populations. ADE soils are characterized by increased fertility and have continued to be exploited following European colonization. Here, we evaluated the legacy of land‐use and soil enrichment on the composition and structure in ADE and non‐ADE (NDE) forests.LocationEastern and southern Amazonia.Time periodPre‐Columbia – 2014.MethodsWe sampled nine pairs of ADE and adjacent NDE forest plots in eastern and southern Amazonia. In each plot, we collected soil samples at 0–10 and 10–20 cm depth and measured stem diameter, height, and identified all individual woody plants (palms, trees and lianas) with diameter ≥ 10 cm. We compared soil physicochemical properties, vegetation diversity, floristic composition, aboveground biomass, and percentage of useful species.ResultsIn the nine paired plots, soil fertility was significantly higher in ADE soil. We sampled 4,191 individual woody plants representing 404 species and 65 families. The floristic composition of ADE and NDE forests differed significantly at both local and regional levels. In southern Amazonia, ADE forests had, on average, higher aboveground biomass than other forests of the region, while in eastern Amazonia, biomass was similar to that of NDE forests. Species richness of both forest types did not differ and was within the range of existing regional studies. The differences in composition between large and small diameter tree recruits may indicate long‐term recovery and residual effects from historical land‐use. Additionally, the proportion of edible species tended to be higher in the ADE forests of eastern and southern Amazonia.Main conclusionsThe marked differences in soil fertility, floristic composition and aboveground biomass between ADE and NDE forests are consistent with a small‐scale long‐term land‐use legacy and a regional increase in tree diversity.
Highlights
The aim of this study was to evaluate the potential legacy of Amazonian Dark Earth (ADE) and their contribution to the structure and floristic composition of modern forests with the following questions: (a) Do forests that grow on ADEs have different richness and floristic composition than adjacent forests? (b) Does forest structure and aboveground biomass differ between ADEs and non-Dark Earth (NDE)? (c) Is the diversity of edible species in ADE forests greater than in NDE forests? Our study takes a novel approach by studying ADE and NDE forests in two distant regions, with contrasting environments and occupation history, to evaluate whether differences between ADE and NDE forests that were already identified in local studies are consistent across broader scales
The southern Amazonian vegetation growing on dystrophic soils has been considered hyperdynamic, with lower species richness (Marimon et al, 2014); in contrast, forests located on higher fertility soils of Andean-Amazon lowland forests are dynamic but have higher species richness
The dissimilarities in floristic composition between ADEs and NDEs indicate a contribution at regional scales to species richness
Summary
The degree to which pre-Columbian people modified Amazonia is one of the most debated topics in ecology, botany, archaeology, palaeoecology, soil science and conservation (Balée, 2013; Barlow, Gardner, Lees, Parry, & Peres, 2012; Clement et al, 2015; Glaser, Balashov, Haumaier, Guggenberger, & Zech, 2000; Heckenberger et al, 2008; Lehmann, Kern, Glaser, & Woods, 2003; Levis et al, 2017; McMichael, Feeley, Dick, Piperno, & Bush, 2017; McMichael, Matthews-Bird, Farfan-Rios, & Feeley, 2017; McMichael et al, 2012; Schaan et al, 2012; Willis, Gillson, & Brncic, 2004; Woods et al, 2009). Recent work conducted across the Amazon Basin suggests potential landscape-scale legacies contributing to the floristic composition and diversity of modern forests (Levis et al, 2017). A disproportionate number of plants are hyperdominant (ter Steege et al, 2013) and domesticated species are five times more likely to be hyperdominant than non-domesticated species (Levis et al, 2017). These data suggest that modern forest composition was influenced by past populations. Previous studies from the eastern Amazon have shown that pre-Columbian crop cultivation and agroforestry altered the modern composition, enriching modern ADE forests in edible plant species (Maezumi et al, 2018)
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