Frequent Freeze Thaw Research Articles

Effects of freeze–thaw cycles on phosphorus adsorption and desorption in the black soil of northeastern China

Frequent freeze–thaw cycles (FTCs) can profoundly affect the chemical properties of soils. We conducted laboratory experiments to explore the effects of freeze–thaw treatments on phosphorus (P) adsorption (Pads) and desorption (Pdes) and to determine the capacity of P retention (Pret) via Pads and Pdes in the fertile black soil of northeastern China. The effects of 0, 1, 3, 6, and 10 FTCs on soil P adsorption and desorption were determined. Each cycle consisted of freezing for 12 h at −10 °C and thawing for 12 h at +7 °C, mimicking a diurnal pattern, at initial soil-moisture contents of 20%, 30%, 40%, and 50% and at amounts of added P of 10, 20, 40, 60, and 80 mg P L−1. Pads increased significantly with increasing amounts of added P. The freeze–thaws of black soils significantly decreased Pads and buffering capacities, which would promote the release of adsorbed P and increase the risk of reducing soil P. High moisture content also affected the behavior of soil P adsorption by reducing adsorbed P as the number of FTCs increased. The P-isotherm data for all soils at equilibrium-P concentrations fit the Langmuir equation well (R2 = 0.93 or higher). Pads had exponential and linear relationships with Pdes capacity and Pret capacity, respectively.

Freeze–thaw cycles and soil water content effects on infiltration rate of three Saskatchewan soils

Fouli, Y., Cade-Menun, B. J. and Cutforth, H. W. 2013. Freeze–thaw cycles and soil water content effects on infiltration rate of three Saskatchewan soils. Can. J. Soil Sci. 93: 485–496. Many soils at high latitudes or elevations freeze and thaw seasonally. More frequent freeze–thaw cycles (FTCs) may affect ecosystem diversity and productivity because freeze–thaw cycles cause changes in soil physical properties and affect water movement in the landscape. This study examined the effects of FTCs (0, 1, 5, and 10) and antecedent soil water content [at soil water potentials (SWP) −1.5, −0.033 and −0.02 MPa] on the infiltration rate of three Saskatchewan soils (a clay, a loam, and a loamy sand). A tension infiltrometer was used at tensions [water potentials of the tension infiltrometer (WPT)] −5, −10 and −15 cm. Infiltration rates increased with increasing SWPs for the loam and clay soils due to higher infiltrability into drier soils. Infiltration rates decreased with increasing SWPs for the loamy sand, probably the result of less surface tension, unimodal porosity, and increased gravitational potential. Infiltration rates either decreased or did not change with increasing FTCs, and this may be due to increased water viscosity as temperatures approach freezing. Also, ice may have formed in soil pores after frequent FTCs, causing lower infiltration rates. Infiltration rates for clay at −1.5 MPa were higher than for loam or loamy sand, probably the result of clay mineralogy and potential shrinking and cracking. Soil texture and initial water content had a significant effect on infiltration rates, and FTCs either maintained or lowered infiltration rates.

Characteristics of soil animal community in the subalpine/alpine forests of western Sichuan during onset of freezing

Seasonal freeze–thaw cycle is a common phenomenon in the subalpine/alpine forest region, and may have a significant influence on the structure and function of soil animal community. To understand the characteristics and dynamics of soil animal community as well as its response to repeated freeze–thaw events in this region during onset of freezing, a field experiment was conducted to investigate the composition, abundance, and diversity of soil fauna in primary fir ( Abies faxoniana) forest, fir and birch ( Betula albosinensis) mixed forest and secondary fir ( A. faxoniana) forest, which were three representative forests in the subalpine and alpine forest region in western Sichuan. Soil samples were collected from November 3 to November 27, 2008, which was defined as onset of freezing based on the simultaneous monitoring of soil temperature. Soil macrofauna were picked up by hand in the fields. Mesofauna were separated and collected from the soil samples by Baermann and Tullgren methods, respectively. By preliminary identification, 40,942 individuals were collected, which belonged to 7 phyla, 15 classes and 25 orders in the three sampling forests. 16,557, 14,669 and 9716 individuals were found in primary forest, mixed forest and secondary forest, respectively. In comparison with the mineral soil layer, the soil organic layer had higher density and groups of soil fauna. Furthermore, following the repeated freeze–thaw events, density and groups of soil fauna experienced a distinct decrease in both soil organic layer and mineral soil layer, and this trend in soil organic layer was more significant in the primary forest, owing to higher intense and more frequent freeze–thaw cycles in soil organic layer of the primary forest. The results revealed that soil animals were sensitive bio-indicators to environmental changes, such as repeated freeze–thaw events and dry–wet cycle. Meanwhile, the results also implied that the dynamics of the structure and function of soil animal community during the onset of freezing was of ecological significance to understand the wintertime ecological process in soils.

Effects of freeze–thaw on C and N release from soils below different vegetation in a montane system: a laboratory experiment

AbstractUnstable snow cover and more frequent freeze–thaw events have been predicted for montane areas in southern Norway, where stable winters are common today. These systems are important contributors to the flux of carbon (C) and nitrogen (N) to air and water. Here we quantify and compare the effects of freeze–thaw on C and N release from soils collected below Calluna, Molinia or Sphagnum. Intact organic soil cores were subjected to four different freeze–thaw regimes for four consecutive 2‐week periods: (1) slow cycling (SC) with one long freezing event during each 2‐week period, (2) fast cycling (FC) with four short freezing events during each 2‐week period, (3) permanent frost (PF) and (4) permanent thaw (PT). The freezing temperature was −5 °C and the thawing temperature was 5 °C. Before start of treatment, at the end of each 2‐week period, and during postincubation periods, carbon dioxide (CO2) emission as well as leachable dissolved organic C (DOC), dissolved organic N (DON), ammonium (NH4), nitrate (NO3) and absorbance at 254 nm were measured. In soils from all three vegetations, PF increased the release of CO2, DOC, DON and NH4 compared with PT. SC caused some scattered effects whereas FC only resulted in some increase in NO3 release below Molinia. Generally, the emission of CO2 and leaching of DOC, DON and NH4 increased in the following order: Sphagnum < Calluna < Molinia. The release of NO3 was greatest below Calluna. Our data suggest that vegetation cover and composition seem at least as important as increased soil frost for future winter fluxes of CO2, DOC, DON and dissolved inorganic N (DIN) from the soil to air and water. The freezing period needs to be sufficiently long to give significant effects.

Soil formation in Phobjikha Valley, Central Bhutan with special regard to the redistribution of loessic sediments

Soil development and landscape evolution were studied in the basin-shaped Phobjikha Valley at 2900–3200 m a.s.l., to the west of the Black Mountain Range, West Central Bhutan. The local environmental setting with strong along-valley winds, frequent freeze–thaw cycles, extensive dry periods and sparse vegetation cover seems to encourage the generation and short-distance transport of silt-sized particles. The effects of this process are evidenced in the smooth valley morphology and in the nature of the examined pedons. Their involvement in continuing redistribution of local sediments is reflected by a homogeneous silty-clayey and stone-free texture, varying profile depths, buried topsoils and weakly developed recent A horizons. In protected locations, in situ weathering of metamorphic parent materials results in alu-andic features with bulk densities <0.9 g cm −3, (Al o + ½Fe o) > 2%, and phosphate retention >95%. Dominance by Al-hydroxy interlayered clay minerals and large amounts of well-crystallised iron oxides indicate an advanced stage of weathering. In areas of preferred eolian deposition, argic and ferralic features emerge, with clay contents of up to 60% and surface areas of >50 m 2 g −1. Under forest, umbric horizons can develop. CEC eff is below 10 cmol c kg −1 at all sites. Cluster and factor analyses of soil chemical and physical parameters confirm the redistribution of local sediments as a dominant factor behind the measured variables. No clear indication of glacial activities in the area was found, whereas the massive silty sediments in the lower parts of most profiles, the presence of debris slopes, and the asymmetric cross sections of the side valleys suggest periglacial conditions. Buried topsoils dated at about 2000 conventional 14C years BP indicate a weakening or absence of sediment influx under wetter conditions towards the end of the Holocene climate optimum. Charcoal on top of paleosols suggests that human activities of deforestation, grazing and arable agriculture may have contributed to the reactivation of local sediment redistribution until today.