The effect of tree species on seasonal fluctuations in water-soluble and hot water-extractable organic matter at post-mining sites

Calcium amendment is a restorative option for nutrient-depleted, acidic soils in the forests of the northeastern United States. We studied the effects of watershed-scale wollastonite (CaSiO3) application on the structural composition of soil organic matter (SOM) and hot-water-extractable organic matter (HWEOM) at the Hubbard Brook Experiment Forest in New Hampshire 7–9 years after treatment, along an elevation gradient. Soils in the high-elevation spruce–fir–birch (SFB) zone contained significantly greater amounts of HWEOM compared with lower elevation hardwood soils, likely due to differences in litter quality and slower decomposition rates in colder soils at higher elevation. The only significant difference in hot-water-extractable organic carbon concentration between reference and calcium-treated watersheds was in Oie horizons of the SFB zone, which also exhibited the greatest degree of soil chemical change after treatment. The 13C nuclear magnetic resonance (NMR) spectra showed no significant patterns in O-alkyl C abundance for either soil or HWEOM along the elevation gradient, suggesting that there were no elevation-related patterns in carbohydrate concentration. The general absence of long-term effects in this study suggests that effects of Ca amendment at this dosage on the composition of SOM were small or short-lived.

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Bulk and water-extractable organic matter from compost: evaluation of the selective dissolution in water using infra-red absorbance ratios.

10.31220/osf.io/5pnkx ◽

2020 ◽

Author(s):

Alla Nasonova ◽

Guy J. Levy ◽

Mikhail Borisover

Keyword(s):

Organic Matter ◽

Selective Dissolution ◽

Land Application ◽

Water Soluble ◽

Novel Approach ◽

Freeze Dried ◽

Infra Red ◽

Carboxylic Groups ◽

Extractable Organic Matter ◽

Water Extractable

Abstract Land application of composts affects concentration and composition of dissolved organic matter (OM) which plays important roles in soil functioning and may have effects on spreading of environmental pollution. Linking between the compositions of bulk compost OM and its water-soluble fraction may, therefore, allow better understanding and prediction of environmental impact of compost land use. The objectives of this study were to (i) examine compositional links between bulk compost OM and its water-extractable OM (WEOM), and (ii) evaluate and quantify selectivity of bulk compost OM dissolution, based on infra-red (IR) absorbing functional groups. For that, 8 different composts and their freeze-dried WEOMs were characterized by mid-IR transmission spectroscopy. Compositions of compost OM and WEOM were characterized in terms of ratios (R) defined on the basis of both areas and heights of specific IR bands in relation to absorbance by aliphatic CH groups. A simple novel approach is suggested, whereby selective dissolution of compost OM components is quantified by relating the R values determined for WEOM to those associated with compost OM. Significant similarities of IR spectra found in a series of WEOMs (and, to a lesser extent, in a series of compost OMs) suggest significant contributions of OM carboxylic groups to various bands. WEOM composition (characterized by the R values) is associated, to a certain extent, with compost OM composition expressed by similar type indices. The WEOM aromaticity estimated by specific UV absorbance correlated strongly with some R values determined for bulk OM.

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