Agroforestry systems impact soil macroaggregation and enhance carbon storage in Colombian deforested Amazonia

Abstract

We investigated the capacity of different types of agroforestry systems to promote the formation of soil macroaggregates through biological or physical processes. Soil macroaggregates were visually separated according to morphological patterns into invertebrate biogenic (small and large faunal aggregates), root biogenic and physicogenic. We evaluated organic carbon in the different types of aggregates: small and large faunal, root biogenic and physicogenic. In agroforestry systems associating shade trees and crops and sylvopastoral systems, small and large faunal aggregates comprised 58.8 and 42.1% respectively of the soil mass. In general, the highest OC contents were found in root macroaggregates (14.1 g C kg−1, followed by small faunal aggregated (13.7 g C kg−1), large faunal aggregated (13.3 g C kg−1) and physicogenic macroaggregates (10.9 g C kg−1). Overall, the average carbon storage in the different land uses was 91.3 ± 4.1. Highest overall C contents were observed in sylvopastoral systems (131 Mg ha−1), pasture (112.2 Mg ha−1), home gardens (105.8 Mg ha−1), nature regeneration (100.6 Mg ha−1) and secondary forest (100.1 Mg ha−1) these being the most efficient options for storing carbon. We conclude that a sound option to increase soil C storage in aggregated structures of deforested Amazonia soils might be planting trees in pastures transformed into sylvopastoral systems.