Impacts of vegetation type and climatic zone on neutral sugar distribution in natural forest soils

Abstract

Soil neutral sugars are a significant component of labile soil organic carbon (SOC) and are derived from both plant and microbial biomass. While plants synthesize both pentose and hexose neutral sugars, microbes almost exclusively produce hexoses. Hexose to pentose ratios in soil thus potentially indicate the extent to which microbes process labile SOC. In this study, we used the ratio of galactose + mannose (G+M) to arabinose + xylose (A+X) to estimate the contribution of sugars derived from microbes and plants to SOC in forest ecosystems. We explored how forest type and climatic zone influence soil neutral sugar profiles by studying coniferous and broadleaf forests located in temperate and subtropical regions in China. At each site, neutral sugars from organic (O) and top-layer mineral (A) soil horizons, as well as from freshly-fallen leaf litter, were measured. Total SOC and soil neutral sugar contents were lower in the subtropical region than in the temperate region, with lower levels in the A horizon than in the O horizon. In both climatic zones, litter (G+M)/(A+X) ratios were higher in coniferous forests (1.2±0.3) than in broadleaf forests (0.4±0.1). Differences in the (G+M)/(A+X) ratios between forest types (coniferous and broadleaf) persisted in the O horizon (1.4±0.2 > 0.9±0.0) and in the A horizon (1.8±0.1 > 1.3±0.0). Across climate zones and forest types, ratios increased from litter over the O horizon to the A horizon. Contrary to our expectations, climate zone did not affect soil (G+M)/(A+X) ratios. Our findings emphasize the important contribution of microbial biomass to labile SOC pools while revealing that soil neutral sugar profiles do not respond to climatic zone drivers as expected.

Responses of Soil Carbon and Microbial Residues to Degradation in Moso Bamboo Forest

“…The amino sugar content in the 0–20 cm soil is higher than that in the 20–40 cm soil. These two conclusions are consistent with the research results of Cui et al [ 34 ] on the temperate forest system in China. The content of amino sugars in the soil is related to the litter content.…”

The impacts of four potential bioenergy crops on soil carbon dynamics as shown by biomarker analyses and DRIFT spectroscopy

“…To determine the origins of soil labile C, we quantified bulk soil neutral sugars, which consist of plant-derived pentoses (C5), including arabinose (Ara), xylose (Xyl), and ribose (Rib), and microbial derived hexoses (C6), including glucose (Glu), mannose (Man), and galactose (Gal), as well as deoxyhexoses (deoxyC6) fucose (Fuc) and rhamnose (Rha) (Cui et al, 2016;Gunina & Kuzyakov, 2015;Jolivet, Angers, Chantigny, Andreux, & Arrouays, 2006), as described by Zhang, He, and Zhang (2007).…”

“…The objective of this research was to explore microbial controls on C dynamics in three potential perennial bioenergy cropping systems, M .× giganteus , switchgrass, and a native prairie assemblage, as well as an annual maize–maize–soybean rotation. We measured SOC concentrations and storage over six growing seasons and assessed how bioenergy crops impact microbial residue contribution to SOC and microbial degradation of labile C of different origins using amino sugar and neutral sugar analyses, respectively (Cui et al., ; Liang, Duncan, Balser, Tiedje, & Jackson, ). We also assessed the degree of existing SOC decomposition as well as SOC stability using diffuse reflectance mid‐infrared Fourier transform spectroscopy (DRIFTS) (Demyan et al., ; Margenot & Hodson, ).…”