Gap thinning improves soil water content, changes the vertical water distribution, and decreases the fluctuation

2018 ◽  
Vol 48 (9) ◽  
pp. 1042-1048 ◽  
Author(s):  
Zhe Wang ◽  
Qihua He ◽  
Bin Hu ◽  
Xueyong Pang ◽  
Weikai Bao
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Forest Restoration ◽  
Water Distribution ◽  
Gap Size ◽  
Eastern Tibetan Plateau ◽  
Soil Water Conditions ◽  
Gap Creation ◽  
Soil Water Distribution

Although it is clear that gap thinning significantly increases the soil water content (SWC) of the topsoil, less is known about whether and how this treatment affects deeper layers. From December 2008 to April 2012, we monitored the SWC at depths of 10, 20, 30, 45, 60, and 90 cm in gap creation treatments (small gap size of 30 m2, intermediate gap size of 80 m2, and unthinned plots) in a typical pine plantation in the eastern Tibetan Plateau. Among gap treatments, differences in SWC and its coefficient of variation (CV) at each depth and the soil water content proportion (SWCP) of the whole soil profile at specific depths were compared. Gap thinning improved SWC and decreased the CV at each depth. The SWCPs in thinned plots were lower at depths from 10 to 30 cm compared with unthinned plots but higher at depths of 45 and 60 cm. Also, in each season, the patterns were similar to the general results. In conclusion, gap thinning improves the SWC, changes the vertical soil water distribution, and decreases the SWC heterogeneity. The soil water conditions in intermediate gaps are more appropriate for local forest restoration.

Effect of Soil Water Content on the Removal of Volatile Chlorinated Hydrocarbons from Soil by Mechanical Soil Aeration

2015 ◽  
Vol 737 ◽  
pp. 541-548 ◽  
Author(s):  
Yan Ma ◽  
Xiao Ming Du ◽  
Yi Shi ◽  
Zhi Fen Wang ◽  
Shi Jie Wang ◽  
...  
Keyword(s):  
Distribution Coefficient ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Water Distribution ◽  
Effective Diffusion ◽  
Chlorinated Hydrocarbons ◽  
Soil Aeration ◽  
Volatile Chlorinated Hydrocarbons ◽  
Soil Water Distribution

Mechanical soil aeration is an easy, effective, and low-cost soil remediation technology; in particular, it is suitable for large sites contaminated by volatile chlorinated hydrocarbons (VCHs). Mechanical soil aeration encourages the volatilization of soil contaminants, but soil moisture, which reduces the amount of open pores, may hinder this process. The present study examined the remediation of silty soil containing 1,2-dichloroethane (1,2-DCA), chloroform (TCM), trichloroethylene (TCE), and tetrachloroethylene (PCE) using mechanical soil aeration and evaluated the influence of soil water content on the efficiency of the process. For artificially contaminated soil, the following conclusions were reached: (i) moisture undermines the volatilization of contaminants. When the soil water content increased from 5% to 20%, the residual concentrations of 1,2-DCA, TCM, TCE, and PCE in the soil increased from 0.08, 0.10, 0.09, and 0.48 mg/kg to 1.43, 0.81, 1.16, and 1.43 mg/kg, respectively. The effective diffusion coefficients also decreased from 1.88×10-2, 1.43×10-2, 1.88×10-2, and 1.30×10-2 cm2/s to 1.71×10-6, 1.30×10-6, 1.71×10-6, and 1.18×10-6 cm2/s, respectively. (ii) Residual contaminants are related to the octanol-water partition coefficient. The soil-water distribution coefficient of PCE was highest among the hydrocarbons (3.72), and the residual contaminants were mainly adsorbed on soil particles. The soil-water distribution coefficient of DCA was lowest (0.42), and the residual contaminants were mainly dissolved in the soil water.

scholarly journals Water Distribution in Reconstructed Soil of Nonmetal Mines and the Ecological Effect in Xinjiang, China

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Zizhao Zhang ◽  
Xiaoli Guo ◽  
Qianli Lv ◽  
Ruihua Hao ◽  
Zezhou Guo ◽  
...  
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Water Distribution ◽  
Land Reclamation ◽  
Observation System ◽  
Neutron Probe ◽  
Matrix Potential ◽  
The Law ◽  
Reconstructed Soil

Because of the arid climate and fragile ecological environment in Xinjiang, China, land reclamation should be carried out after mining. The core of land reclamation is the water content of the surface covering soil. In this paper, the law of water distribution in reclamation reconstructed soil of nonmetal mines in Xinjiang was studied. In order to obtain the law of water distribution in reconstructed soil, we set up an observation system of the neutron probe and tensiometer. The neutron probe was used to monitor the soil water content. The tensiometers were used to obtain the matrix potential of soil for verifying the water distribution in reconstructed soil. Volumetric water content and matrix potential of reconstructed soil during 1-year period of management and irrigation were obtained by long-term monitoring. After one year’s field in situ test, 2424 sets of neutron probe data and 1368 sets of tensiometer data were obtained. By studying the above parameters, we summarized the law of water distribution in reconstructed soil of variable thickness and degree of compaction with nonmetallic waste rock filling. The results showed that covering soil was helpful to retain water content. Whether the soil was compacted or uncompacted, the soil water content at the depth of 10 cm was less than that at other depth of reconstructed soil because it was greatly affected by meteorological factors. The water content of reconstructed soil at 30 cm depth was greater than that at other depths. Under the influence of factors such as the thickness and compaction of the soil, the response time of soil water content and matrix potential to each irrigation infiltration was different. According to the characteristics of reclamation-vegetation such as alfalfa growth in Xinjiang, the thickness of surface reconstructed soil should be not less than 50 cm. Over time, soil that was compacted once was better for the vegetation. The research results could provide a reference for the land reclamation of nonmetallic mines in Xinjiang, China.

scholarly journals Infiltration and Soil Water Distribution in Irrigation Furrows Treated with Polyacrylamide

2020 ◽  
Vol 63 (5) ◽  
pp. 1451-1464
Author(s):  
Rick D. Lentz ◽  
Eduardo Bautista ◽  
Anita Koehn ◽  
Robert Sojka
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Irrigation Water ◽  
Water Distribution ◽  
Water Soluble ◽  
Inflow Rate ◽  
Lower Section ◽  
Irrigation Uniformity ◽  
Advance Time ◽  
Soil Water Distribution

HighlightsControl furrows with 1× inflow rates were compared with 3× advance inflows treated with 10 mg L-1 polymer (WSPAM).WSPAM reduced sediment loads in furrow streams by 89%, despite its 3× greater advance inflows.WSPAM furrow advance times and infiltrated volumes were greater than predicted from increased inflows alone.WSPAM enabled reduced upper-section infiltration and increased lower-section infiltration relative to control furrows.Abstract. Few if any studies have measured the effects of water-soluble anionic polyacrylamide (WSPAM) on infiltration and soil water distribution in different segments of irrigation furrows. We conducted a four-year study on a silt loam soil with 1.5% slopes. Control furrows received no WSPAM and inflows were 15.1 L min-1, whereas WSPAM was applied using 10 mg L-1 a.i. to 45 L min-1 inflows during furrow advance. Despite its greater advance phase inflow rates, WSPAM application reduced sediment concentrations in furrow streams by an average of 89% relative to the control. A surface irrigation model, WinSRFR 5.1, was used to separate furrow inflow rate effects on infiltration from that of WSPAM. Relative to results predicted by simulation for the entire furrow, the polymer treatment: (1) increased advance time an average 1.4-fold, (2) increased advance-phase infiltrated volume 1.5-fold, and (3) increased infiltration volume at the common opportunity time 1.2-fold. Hence, these effects resulted from WSPAM and not from differences in treatment inflow rates. Treatment infiltration amounts varied markedly among irrigations and years, as did the intensity of WSPAM effects. These were attributed mainly to differences in infiltration opportunity time, but temporal differences in soil water content during furrow formation, irrigation water electrical conductivity, initial soil surface water content and water temperature, and the irrigation-long, furrow-stream mean sediment content also appear to have influenced infiltration rates. Although inconsistent, WSPAM increased net furrow infiltration in the lower section and reduced infiltration in the upper section relative to control furrows. This effect could not be explained by the greater inflow rate and shorter advance time of the WSPAM treatments and was attributed to spatially variable WSPAM effects on infiltration opportunity time and possibly irrigation water viscosity. The WSPAM management approach, while protecting against furrow erosion, may potentially provide a means of improving irrigation uniformity and reducing associated percolation water and nutrient losses. Keywords: Furrow advance, Irrigation, Irrigation uniformity, Polymers.

The effects of drainage on substrate water content at several forested Alberta peatlands

1996 ◽  
Vol 26 (1) ◽  
pp. 53-62 ◽  
Author(s):  
R.L. Rothwell ◽  
U. Silins ◽  
G.R. Hillman
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Water Table ◽  
Tree Growth ◽  
Soil Conditions ◽  
Drainage Ditch ◽  
Sampling Locations ◽  
Soil Water Conditions ◽  
And Performance

Hydrologic drainage criteria that describe the position of the water table between adjacent ditches are commonly used to assess the initial effectiveness of peatland drainage projects for tree growth improvement. However, these criteria do not reflect the soil conditions that regulate tree growth and performance after drainage. The effect of three drainage ditch spacings (30, 40, and 50 m) on the spatial variability of soil water conditions at three drained boreal Alberta peatlands was studied. Soil water content (0–30 cm depth) was found to be insensitive (p = 0.686) to drainage ditch spacing several years after drainage. Greater variation was observed between different sampling locations (p = 0.024) relative to the position of the ditch edge within similar ditch spacings. Spatial distribution of soil water in the unsaturated zone was found to be inversely related to the degree of water table lowering. Spatial patterns of soil water content were strongly associated with changes to substrate bulk density resulting from post-drainage peatland subsidence.

COMPARISON OF TWO SOIL-WATER MODELS UNDER SEMI-ARID GROWING CONDITIONS

1988 ◽  
Vol 68 (1) ◽  
pp. 17-27 ◽  
Author(s):  
R. DE JONG
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Water Distribution ◽  
Water Movement ◽  
Arid Zone ◽  
Absolute Difference ◽  
Long Term Experiment ◽  
Growing Conditions ◽  
Semi Arid

The Versatile Soil Moisture Budget (VSMB) and the Soil-Plant-Air-Water (SPAW) model were compared and tested against soil-water content data from a long-term experiment in which wheat was grown on fallow land in the semi-arid zone of Saskatchewan. Both models were driven by daily air temperatures and precipitation data. At the expense of requiring more detailed soil and crop information, the SPAW model simulated the water balance and its components in greater detail than the VSMB. Predictions of soil-water contents throughout the growing season with either model corresponded very well with the measured data. The overall mean absolute difference in total soil-water content to a depth of 120 cm was 1.5 cm for the VSMB and 1.2 cm for the SPAW model. Predictions of water distribution in the profile were also satisfactory. A choice between the two models, to be used under semi-arid growing conditions, will depend on the availability of input data and the required level of output. Key words: Soil-water movement, modelling, evapotranspiration

scholarly journals Forest decline caused by high soil water conditions in a permafrost region

2010 ◽  
Vol 14 (2) ◽  
pp. 301-307 ◽  
Author(s):  
H. Iwasaki ◽  
H. Saito ◽  
K. Kuwao ◽  
T. C. Maximov ◽  
S. Hasegawa
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Forest Recovery ◽  
Annual Precipitation ◽  
Line Transect ◽  
Permafrost Region ◽  
Taiga Forest ◽  
Water Conditions ◽  
Soil Water Conditions

Abstract. In the permafrost region near Yakutsk, eastern Siberia, Russia, annual precipitation (June–May) in 2005–2006 and 2006–2007 exceeded the 26-year (1982–2008) mean of 222±68 mm by 185 mm and 128 mm, respectively, whereas in 2007–2008 the excedent was only 48 mm, well within the range of variability. Yellowing and browning of larch (Larix cajanderi Mayr.) trees occurred in an undisturbed forest near Yakutsk in the 2007 summer growing season. Soil water content at a depth of 0.20 m was measured along a roughly 400 m long line transect running through areas of yellowing and browning larch trees (YBL) and of normal larch trees (NL). In the two years of supranormal precipitation, soil water content was very high compared to values recorded for the same area in previous studies. For both wet years, the mean degree of saturation (s) was significantly greater in YBL than NL areas, whereas the converse was the case for the gas diffusivity in soil. This implies that rather than mitigating water stress suffered during normal precipitation years, elevated soil water conditions adversely affected the growth of larch trees. Eastern Siberia's taiga forest extends widely into the permafrost region. Was such supranormal annual precipitation to extend for more than two years, as might be expected under impending global climate changes, forest recovery may not be expected and emission of greenhouse gas might continue in future.

scholarly journals Forest decline caused by high soil water conditions in a permafrost region

2009 ◽  
Vol 6 (5) ◽  
pp. 6087-6105 ◽  
Author(s):  
H. Iwasaki ◽  
H. Saito ◽  
K. Kuwao ◽  
T. C. Maximov ◽  
S. Hasegawa
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Forest Decline ◽  
Annual Precipitation ◽  
Line Transect ◽  
Permafrost Region ◽  
Taiga Forest ◽  
Water Conditions ◽  
Soil Water Conditions

Abstract. In the permafrost region near Yakutsk, eastern Siberia, Russia, annual precipitation (June–May) in 2005–2006 and 2006–2007 exceeded the 26-year (1982–2008) mean of 222±68 mm by 185 mm and 128 mm, respectively, whereas in 2007–2008 the excedent was only 48 mm, well within the range of variability. Yellowing and browning of larch (Larix cajanderi Mayr.) trees occurred in an undisturbed forest near Yakutsk in the 2007 summer growing season. Soil water content at a depth of 0.20 m was measured along a roughly 400 m long line transect running through areas of yellowing and browning larch trees (YBL) and of normal larch trees (NL). In the two years of supranormal precipitation, soil water content was very high compared to values recorded for the same area in previous studies. For both wet years, the mean degree of saturation (s) was significantly greater in YBL than NL areas, whereas the converse was the case for the relative gas diffusivity (DP/D0). This implies that rather than mitigating water stress suffered during normal precipitation years, elevated soil water conditions adversely affected the growth of larch trees. Eastern Siberia's taiga forest extends widely into the permafrost region. Was such supranormal annual precipitation to extend for more than two years, as might be expected under impending global climate changes, forest decline would be expanded and a danger of accelerating greenhouse gas emissions could result.

SOIL WATER CONTENT AFFECTS THE AVAILABILITY OF PHOSPHATE

1985 ◽  
pp. 185-189
Author(s):  
M.C.H.Mouat Pieter Nes
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Soil Solution ◽  
Equivalent Reduction

Reduction in water content of a soil increased the concentration of ammonium and nitrate in solution, but had no effect on the concentration of phosphate. The corresponding reduction in the quantity of phosphate in solution caused an equivalent reduction in the response of ryegrass to applied phosphate. Keywords: soil solution, soil water content, phosphate, ryegrass, nutrition.

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