Soil organic matter dynamics in a North America tallgrass prairie after 9 yr of experimental warming

Abstract

Abstract. The influence of global warming on soil organic matter (SOM) dynamics in terrestrial ecosystems remains unclear. In this study, we combined soil fractionation with isotope analyses to examine SOM dynamics after nine years of experimental warming in a North America tallgrass prairie. Soil samples from the control plots and the warmed plots were separated into four aggregate sizes (>2000 µm, 250-2000 µm, 53-250 µm, and <53 µm), and three density fractions (free light fraction -LF, intra-aggregate particulate organic matter -iPOM, and mineral-associated organic matter -mSOM). All fractions were analyzed for their carbon (C) and nitrogen (N) content, and δ 13 C and δ 15 N values. Warming did not significantly effect soil aggregate distribution and stability but increased C 4 -derived C input into all fractions with the greatest in LF. Warming also stimulated decay rates of C in whole soil and all aggregate sizes. C in LF turned over faster than that in iPOM in the warmed soils. The δ 15 N values of soil fractions were more enriched in the warmed soils than those in the control, indicating that warming accelerated loss of soil N. The δ 15 N values changed from low to high, while C:N ratios changed from high to low in the order LF, iPOM, and mSOM due to increased degree of decomposition and mineral association. Overall, warming increased the input of C 4 -derived C by 11.6 %, which was offset by the accelerated loss of soil C. Our results suggest that global warming simultaneously stimulates C input via shift in species composition and decomposition of SOM, resulting in negligible net change in soil C.

Shifts in soil organic carbon and nitrogen dynamics for afforestation in central China

“…The C and N concentrations and ␦ 13 C and ␦ 15 N values were measured for all of the soil fractions and plant materials. Subsamples from all of the fractions were treated with 1 N HCL for 24 h at room temperature to remove any soil carbonates (Cheng et al, 2011). Subsamples of leaf, root, litter, and SOM were weighed and analyzed for ␦ 13 C, ␦ 15 N, and C and N concentrations using an isotope ratio mass spectrometer (Thermo Finnigen, Delta-Plus, Flash, EA, 1112 Series, USA).…”

“…The plant samples (leaves, litter and roots) and collected soil were dried at 50 • C to a constant weight and were then ground to pass through 20-mesh (0.84 mm) sieves (Cheng et al, 2011). The C and N concentrations and ␦ 13 C and ␦ 15 N values were measured for all of the soil fractions and plant materials.…”

“…The decomposition rate constant (k) for the old C (i.e. the C of the 18 year-old organic matter) from organic soil was calculated based on Cheng et al (2011):…”

Riparian soil physicochemical properties and correlation with soil organic carbon of an inflowing river of Taihu Lake

“…Each soil sample was weighed for bulk density determination, then passed through an 8-mm mesh sieve by gently breaking soils along natural fracture planes [4]. Soil was digested using H 2 SO 4 -HClO 4 and TP was measured by the spectrophotometric method with a continuous flow automated analyzer at 700 nm [1].…”

“…Soil was digested using H 2 SO 4 -HClO 4 and TP was measured by the spectrophotometric method with a continuous flow automated analyzer at 700 nm [1]. SOC was measured using acid dichromate wet oxidation as described by Nelson and Sommers [13], TN was tested with potassium persulfate oxidation [2].…”