Spatial variation of carbon and nutrients stocks in Amazonian Dark Earth

Abstract

Amazonian Dark Earths (ADE) are anthropic soils that are enriched in carbon (C) and several nutrients, particularly calcium (Ca) and phosphorus (P), when compared to adjacent soils from the Amazon basin. Studies on ADE empower the understanding of complex pre-Columbian cultural development in the Amazon and may also provide insights for future sustainable agricultural practices in the tropics. ADE are highly variable in size, depth and soil physico-chemical characteristics. Nonetheless, the differentiation between ADE and the adjacent soils is not standardized and is commonly done based on visual field observations. In this Highlights  Carbon and nutrients stocks in ADE were predicted using an environmental covariate.  Total Ca and Total P contents exhibited better fit to our model than Total C content.  Pretic horizon criteria enabled the differentiation of two unambiguous areas.

Pre-Columbian soil fertilization and current management maintain food resource availability in old-growth Amazonian forests

“…Given the strong association of total phosphorus to the soil fertility axis ( Table 2) and given that total soil phosphorus was previously recognized as the best indicator of anthropogenic enrichment of ADE sites (Alho et al 2019), total P was chosen to represent soil fertility in our structural equation models. Additionally, together g) h) p = 0.002 p = 0.048 p < 0.001 p = 0.596 p = 0.076 p = 0.057 p = 0.015 p = 0.065 Fig.…”

“…We found strong effects of past activities on nutrients of forest soils, especially on calcium and total phosphorus, towards the core of pre-Columbian villages (ADE sites), but a weak and negative effect near current villages. Even though most studies have defined ADE and non-ADE sites as discrete categories due to sharp contrasts in soil nutrients between these soils (e.g., Alho et al 2019). Fraser et al (2011) proposed a continuum of soil fertility from the core of ADE sites towards the adjacent soils in Central Amazonia.…”

Anthropogenic Soils Promote Biodiversity in Amazonian Rainforests

“…Station, while the other one was at the Tapajós National Forest, a site of previous work on ADEs 39 . Both OFs at IR were at the Embrapa Amazônia Ocidental Caldeirão Experiment Station, and have been extensively studied in the past for soil fertility and pedogenesis 42,53 , as well as microbial diversity 54,55 . ADE formation in IR was estimated to have begun ~1,050 -950 years BP 56 and at BT ~530-450 years BP 57 .…”

Long-term persistence of soil organic matter in Amazonian Dark Earth

“…proxy for ADJ) (Fig. 1) as described in Chapter 2 (Alho et al, 2019). These samples exhibit the typical contrast in soil properties between ADE and ADJ (e.g.…”

“…proxy for ADJ ( Fig. 1) as described in Chapter 2 (Alho et al, 2019). Soil samples were air-dried at room temperature, passed through a 2mm sieve and visible roots were removed manually.…”