Journal
GEODERMA
Volume 241, Issue -, Pages 221-229Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.geoderma.2014.11.013
Keywords
Aggregate fractionation; Fungal biomass; Microbial carbon; Seasonal dynamics
Categories
Funding
- German Research Foundation (Research Training Group 1397 Regulation of soil organic matter and nutrient turnover in organic agriculture)
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In grassland soils, the temporal dynamics in different fractions of soil organic carbon (SOC) is not completely understood. We investigated the temporal variations of water-stable aggregates, microbial biomass C (C-mic) and ergosterol concentrations (as a proxy for fungal biomass) in loamy sandy soils under grassland (north of Kiel, Germany). Samples were taken six times between October 2010 and October 2011 from i) a permanent grassland, ii) an arable plot converted to grassland and iii) a grassland with a one-time tillage operation (both in September 2010). Water-stable aggregate concentrations were determined by a wet-sieving procedure, C-mic concentrations by chloroform-fumigation-extraction and ergosterol concentrations by ethanol extraction. Temporal variation in aggregate distribution of soil samples from the permanent grassland was considerable: the large macroaggregate (>2000 mu m) concentrations (mean +/- standard error, n = 3) in the surface soil (0-10 cm) were highest in October 2011 (666 +/- 12 g kg(-1)) and lowest in May (206 +/- 49 g kg(-1)). The tillage operation in grassland led to lower concentrations of large macroaggregates, ergosterol and C-mic in the surface soil than in the permanent grassland. The conversion of arable land into grassland did not affect macroaggregate concentrations, despite an increase in C-mic (1.4-fold) and ergosterol concentration (3.3-fold) in the surface soil. Multiple linear regression analysis described the variations in the large macroaggregate concentration satisfactorily (R-2 = 0.60) and indicated that the gravimetric moisture content and the C-mic concentration had positive effects and the pH a negative effect. While ergosterol concentrations (mean +/- standard error) showed some temporal variations (values for the surface soil in the grassland ranged from 0.5 +/- 0.1 to 1.5 +/- 0.1 mg kg(-1)), C-mic concentrations varied much less, indicating a higher sensitivity of ergosterol to soil cultivation or changing environmental conditions. (C) 2014 Elsevier B.V. All rights reserved.
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