Extrapolative Capability of Two Models That Estimating Soil Water Retention Curve between Saturation and Oven Dryness

<div><p>Accurate estimation of soil water retention curve (SWRC) at the dry region is required to describe the relation between soil water content and matric suction from saturation to oven dryness. In this study, the extrapolative capability of two models for predicting the complete SWRC from limited ranges of soil water retention data was evaluated. When the model parameters were obtained from SWRC data in the 0–1500 kPa range, the FX model (Fredlund and Xing, 1994) estimations agreed well with measurements from saturation to oven dryness with RMSEs less than 0.01. The GG model (Groenevelt and Grant, 2004) produced larger errors at the dry region, with significantly larger RMSEs and MEs than the FX model. Further evaluations indicated that when SWRC measurements in the 0–100 kPa suction range was applied for model establishment, the FX model was capable of producing acceptable SWRCs across the entire water content range. For a higher accuracy, the FX model requires soil water retention data at least in the 0- to 300-kPa range to extend the SWRC to oven dryness. Comparing with the Khlosi et al. (2006) model, which requires measurements in the 0–500 kPa range to reproduce the complete SWRCs, the FX model has the advantage of requiring less SWRC measurements. Thus the FX modeling approach has the potential to eliminate the processes for measuring soil water retention in the dry range.</p></div

Mean error (ME) and root mean square error (RMSE) of the FX model (Fredlund and Xing, 1994) for the tested eight soils from saturation to oven dryness: FX-1 and FX-3 indicate that the parameters were obtained by fitting the models to the measurements in the suction range of 0 to 100 kPa and 0 to 300 kPa, respectively.

<p>Mean error (ME) and root mean square error (RMSE) of the FX model (Fredlund and Xing, 1994) for the tested eight soils from saturation to oven dryness: FX-1 and FX-3 indicate that the parameters were obtained by fitting the models to the measurements in the suction range of 0 to 100 kPa and 0 to 300 kPa, respectively.</p

The effect of H₂S on hepatic I/R injury in young and old rats.

<p>(A) The serum levels of H2S were significantly increased in the young rats that received a preconditioning dose of 20 µmol/kg NaHS compared to rats in the I/R group. (B) The serum levels of H2S were significantly increased in the old rats that received a preconditioning dose of 20 µmol/kg NaHS compared to the rats in the I/R group. (C) The serum levels for alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were determined in the young rats after 6 h of reperfusion. (D) The serum levels for ALT and AST were determined in the old rats after 6 h of reperfusion. (E) Suzuki’s scores for the livers of the young rats after 24 h of reperfusion. (F) Suzuki’s scores for the livers of the old rats after 24 h of reperfusion. **P<0.01, indicates significant differences from the respective control groups.</p

The effect of H₂S on Nrf-2-mediated signaling pathway.

<p>Relative mRNA levels of Nrf-2 were assayed in the young and old rats. Pretreatment with NaHS (20 µmol/kg) significantly increased Nrf-2 mRNA (A) and protein (B) levels in the young rats treated with I/R, but it had little effect on those in the old rats. Pretreatment with 20 µmol/kg NaHS significantly increased mRNA (C) and protein (D) levels of NQO1, GST, and HO-1 in the young rats treated with I/R. Pretreatment of 20 µmol/kg NaHS slightly increased mRNA (E) and protein (F) levels of NQO1, GST and HO-1 in the old rats treated with I/R. **P<0.01, indicate significant differences from the respective control groups.</p

Soil organic matter content (OM) and texture of the soils.

<p>Soils 1-7 were collected in China and soil 8 was collected in the USA.</p><p>Soil organic matter content (OM) and texture of the soils.</p

Knockout of miR-34a expression enhanced the hepatoprotective effect of H₂S on the old rats.

<p>(A) The serum levels of ALT and AST were assayed in the old rats. Pretreatment with NaHS had little effect on the serum levels of ALT and AST, which were significantly decreased by miR-34a inhibitor in the old rats with I/R. (B) The injection of miR-34a inhibitor clearly decreased miR-34a levels. (C) Suzuki’s scores for the livers of the old rats. **P<0.01, indicates significant differences from the respective control groups.</p

Overexpression of miR-34a inhibited the hepatoprotective effect of H₂S on young rats.

<p>(A) The serum levels of ALT and AST were assayed in the young rats. The serum levels of ALT and AST were significantly decreased in the young rats following the pretreatment with NaHS, and this decrease was reversed by miR-34a mimic. (B) The injection of miR-34a mimic clearly increased miR-34a levels. (C) Suzuki’s scores for the livers of the young rats. **P<0.01, indicates significant differences from the respective control groups.</p

miR-34a mediated Nrf-2 signaling pathway was implicated in the hepatoprotective effects of H₂S.

<p>The injection of miR-34a mimic decreased the mRNA (A) and protein (B) levels of Nrf-2, NQO1, GST and HO-1 in the young rats in the I/R+pretreatment with NaHS group. The injection of miR-34a inhibitor increased the mRNA (C) and protein (D) levels of Nrf-2, NQO1, GST and HO-1 in the old rats in the with I/R+pretreatment with NaHS group. **P<0.01, indicates significant differences from the respective control groups.</p

Mean error (ME) and root mean square error (RMSE) of the FX model (Fredlund and Xing, 1994) and the GG model (Groenevelt and Grant, 2004) for the tested soils from saturation to oven dryness.

<p>Soil water retention data in the 0–1500 kPa suction range were used for model establishment.</p><p>Mean error (ME) and root mean square error (RMSE) of the FX model (Fredlund and Xing, 1994) and the GG model (Groenevelt and Grant, 2004) for the tested soils from saturation to oven dryness.</p

Comparison of measured and estimated soil water retention curves from oven-dryness to saturation from the FX model (Fredlund and Xing, 1994) and KCGS model (Khlosi et al., 2006) on 10 soils from Prebble (1991).

<p>FX-1 and KCGS-1 indicate that the parameters were obtained by fitting the FX model and KCGS model to the measurements in the suction range of 0 to 100 kPa, respectively.</p