Carbon storage and root penetration in deep soils under small-farmer land-use systems in the Eastern Amazon region, Brazil

• Published in: Plant and soil Vol. 219; no. 1/2; pp. 231 - 241
• Main Authors: Sommer, R, Denich, M, Vlek, P.L.G
• Format: Journal Article
• Language: English
• Published: Dordrecht Kluwer Academic Publishers 01.01.2000; Springer; Springer Nature B.V
• Subjects: Agricultural land; Agricultural soils; Agriculture; Agrology; Agronomy. Soil science and plant productions; biogeochemical cycles; Biological and medical sciences; biomass; Brazil; Carbon; Carbon sequestration; Charcoal; Chemical, physicochemical, biochemical and biological properties; Cultivation; fields; Forest soils; Forests; Fruits; Fundamental and applied biological sciences. Psychology; Land use; Old growth forests; Orchard soils; Organic matter; Organic soils; Pasture; Physics, chemistry, biochemistry and biology of agricultural and forest soils; Plantations; root systems; rooting depth; Roots; Shifting cultivation; Slash and burn; Soil; Soil depth; soil organic matter; Soil science; Vegetation; Brazil; South America; Amazon Basin; America; Brazil, Amazon R; Brazil, Para; Monocotyledones; Passifloraceae; Passiflora edulis; Biomass; Texture; Depth; Dicotyledones; Piper nigrum; Angiospermae; Primary forest; Elaeis guineensis; Root; Cropping system; Piperaceae; Soil structure; Biogeochemical cycle; Oil plant(vegetal); Land use; Carbon cycle; Penetration; Storage; Fruit crop; Flavoring crop; Spermatophyta; Palmae; Biological accumulation
• ISSN: 0032-079X; 1573-5036
• DOI: 10.1023/A:1004772301158

The north-east of Pará state in the Eastern Amazon of Brazil was settled over 100 years ago. Today the region is an agricultural landscape with variously-aged secondary vegetation and fields with annual cultures, plantation crops and pastures. The effect of these different land covers on carbon sequestration as well as on water and nutrient extraction remain subject of debate. Therefore, we assessed the importance of land use on soil carbon stocks by measuring various C fractions and root biomass (0-6 m) in slash-and-burn systems and (semi-) permanent cultures. An extensive root system down to at least 6 m depth was present under various secondary vegetation stands and slashed and burned fields recently taken into cultivation as well as under a primary forest. Shallower rooting patterns were evident under (permanent) oil palm (4.5 m) and (semi-permanent) passion fruit plantations (2.5 m). Carbon storage in soils of traditional slash-and-burn agriculture up to 6 m depth (185 t ha⁻¹) was not significantly lower than under a primary forest (196 t ha⁻¹) but declined significantly under (semi-) permanent cultures (to 146-167 t ha⁻¹). Compared to above-ground C losses, soil C losses due to slash-and-burn agriculture may thus be small. This is an argument for maintaining the secondary vegetation as part of the agricultural land-use system, as the root system of its trees is conserved and thus C is sequestered also at greater depth.