Decadal-scale litter manipulation alters the biochemical and physical character of tropical forest soil carbon. (September 2018)

• Record Type: Journal Article
• Authors: Cusack, Daniela F.; Halterman, Sarah M.; Tanner, Edmund V.J.; Wright, S. Joseph; Hockaday, William; Dietterich, Lee H.; Turner, Benjamin L.
• Is Part Of: Soil biology and biochemistry. Volume 124(2018)
• Page Start: 199
• Page End: 209
• Publication Date: 2018-09
• Subjects: Soil organic matter (SOM) -- Nitrogen -- Dissolved organic carbon (DOC) -- 13C NMR -- Radiocarbon 14C -- Density fractionation; Soil biochemistry -- Periodicals; Soil biology -- Periodicals; Sols -- Biochimie -- Périodiques; Sols -- Biologie -- Périodiques; Sols -- Microbiologie -- Périodiques; Bodembiologie; Biochemie; 631.46
• DOI: 10.1016/j.soilbio.2018.06.005
• Languages: English
• ISSNs: 0038-0717

Abstract

Abstract: Climate change and rising atmospheric carbon dioxide (CO2 ) concentrations are likely to alter tropical forest net primary productivity (NPP), potentially affecting soil C storage. We examined biochemical and physical changes in soil C fractions in a humid tropical forest where experimental litter manipulation changed total soil C stocks. We hypothesized that: (1.) low-density soil organic C (SOC) fractions are more responsive to altered litter inputs than mineral-associated SOC, because they cycle relatively rapidly. (2.) Any accumulation of mineral-associated SOC with litter addition is relatively stable (i.e. low leaching potential). (3.) Certain biomolecules, such as waxes (alkyl) and proteins ( N -alkyl), form more stable mineral-associations than other biomolecules in strongly weathered soils. A decade of litter addition and removal affected bulk soil C content in the upper 5 cm by +32% and −31%, respectively. Most notably, C concentration in the mineral-associated SOC fraction was greater in litter addition plots relative to controls by 18% and 28% in the dry and wet seasons, respectively, accounting for the majority of greater bulk soil C stock. Radiocarbon and leaching analyses demonstrated that the greater mineral-associated SOC in litter addition plots consisted of new and relatively stable C, with only 3% of mineral-associated SOC leachable in salt solution. Solid-state 13 C NMR spectroscopy indicated that waxes (alkyl C) and microbial biomass compounds ( O -alkyl and N- alkyl C) in mineral-associated SOC are relatively stable, whereas plant-derived compounds (aromatic and phenolic C) are lost from mineral associations on decadal timescales. We conclude that changes in tropical forest NPP will alter the quantity, biochemistry, and stability of C stored in strongly weathered tropical soils. Graphical abstract: Image 1 Highlights: Tropical forest soil carbon chemistry was sensitive to changed litter biomass. Soil carbon in stable organo-mineral associations increased with litter addition. Waxes and proteins were the most stable component of organo-mineral associations. Phenolic and aromatic carbon was lost from mineral associations with litter removal.