Distribution of soil organic carbon in the light and heavy fractions for six shelterbelt species and their adjacent agricultural fields in Saskatchewan.

Abstract

Agroforestry systems play an important role in the sequestration of carbon (C) to reduce atmospheric carbon dioxide (CO 2) levels. However, the extent of long-term C sequestration will depend on physical stabilization of the sequestered C. This study determined the influence of six major shelterbelt species on soil organic carbon (SOC) distribution in the light-and heavy-density fractions of bulk soil compared with adjacent agricultural fields. Soil samples were collected from the shelterbelts and adjacent agricultural fields and were separated into light and heavy fractions using sodium iodide solution (NaI, density = 1.6 g cm −3) and analyzed for their organic C stocks. Both the light and heavy fractions to a 50 cm soil depth contained higher SOC stocks for the shelterbelts (21 and 91 Mg C ha −1 , respectively) compared with the adjacent agricultural fields (14 and 81 Mg C ha −1 , respectively). Most SOC added at the 0-10 cm soil depth was in the form of labile light fraction (92%), whereas heavy fraction contributed to 70% of the increase in the SOC stocks at the 10-30 cm soil depth. Increase in light-fraction SOC stocks was higher for coniferous species compared with hardwood species, and accounted for 48%-50% and 28%-31% of the increase in SOC stocks for coniferous and hardwood shelterbelts, respectively. This trend was attributed to the differences in the amount and quality of litter between coniferous and hardwood species.

Soil Organic Carbon in Alley Cropping Systems: A Meta-Analysis

“…However, in their meta-analysis, they used a large number of publications that investigated alley cropping stands that were converted from natural forests to alley cropping. The decay of organic matter (OM) can take up to several decades [21], so it is expected that SOC in such alley cropping systems, converted from natural forests, is higher than that in long-term agricultural fields under monocultures. However, what about the land-use conversion in the other direction?…”

“…Dhillon and Van Rees [21] reported that assessments of SOC pools could help determine the effects of land management practices on soil C sequestration potential as well as its quality and fertility. In this research, we were interested in the impact of trees on SOC when trees are introduced into agricultural fields and not alley cropping stands established on previously natural forest sites.…”

Response of soil aggregate disintegration to the different content of organic carbon and its fractions during splash erosion

“…In order to distinguish the influence of SOC on the formation of aggregates, some researchers used physical or chemical methods to classify SOC into different components (Barrios et al, 1996; Dhillon & Van Rees, 2017; Guan et al, 2018; Six et al, 2000; Xiang et al, 2015). Density fractionation of SOC is a common way to separate the SOC into light fraction organic carbon (LFOC) and heavy fraction organic carbon (HFOC) (Christensen, 1992; Turchenek & Oades, 1979; Wagai et al, 2009).…”

“…In order to distinguish the influence of SOC on the formation of aggregates, some researchers used physical or chemical methods to classify SOC into different components (Barrios et al, 1996;Dhillon & Van Rees, 2017;Guan et al, 2018;Six et al, 2000;Xiang et al, 2015).…”