Advanced Materials Research Vols. 518-523

Abstract: The functional equations have been established between the soil water retention curve and the soil structures fractal dimension by fractal geometry theory. Based on the functional equations have the same or similar law form with Campbell law, Soil pore space fractal dimensions were deduced conversely by the curve of soil water retention, which not only reveal physics matter of Campbell law， but also can carry out fractal research of prediction of soil water retention. The comparison of predicted soil water retention with measured data shows that the proposed model can be used to describe various soil textures.

Abstract: Locations of sampling points in Pinus koraiensis-dominated broadleaved mixed forest gap in Xiao Xing’an Mountains of Northeast China were determined by grid method. Spatial variability in physical soil properties (PSPs) at those locations in 2 depths of 0–20 cm and 20–40 cm was analyzed by descriptive statistics and geostatistics. The results indicated that soil water content (SWC), saturated moisture capacity, capillary water-holding capacity and porosity were higher in 0–20 cm than in 20–40 cm except for bulk density. PSPs in 0–20 cm had relatively higher ranges and coefficients of variation. The total and autocorrelative spatial heterogeneity in PSPs were larger in 0–20 cm than in 20–40 cm. SWC had a strong anisotropic structure in an easterly and northerly direction, but porosity exhibited isotropy structure in the same directions. With increasing spatial distance, the three other PSPs presented anisotropic structures. Within spatial autocorrelative range, the interactive effect between semivariograms of PSPs in 0–20 cm was not significant. For spatial distribution of PSPs in 2 different depths, the patches with the middle and lower ranks dominated in the forest gap. Patches with higher rank were only distributed in 0–20 cm and were located north of the forest gap.

Abstract: The characteristics of soil erosion of steppe in Inner Mongolia were studied in wind-tunnel tests. The results indicated that the soil in this region consists primarily of sand and coarse silt, with particle sizes mainly between 0.02 and 1mm, and it is defined as erodible sandy soil. The eroded sediments are mainly concentrated at heights of 0~24cm, and the extreme value of particle size is clearly in the range 100~300μm. Average particle size increased with increasing wind speed, and it decreased exponentially in the vertical direction, reflecting the characteristics of sand transport by wind. The relationship between wind erosion rate and wind speed assumes a power function with correlation coefficients greater than 0.9. A wind speed of 15m/s is a significance point above which wind erosion in this region becomes very large. Soil erosion rate decreases logarithmically as soil moisture content and vegetation coverage increase, and the 5% level of moisture content is a turning point.

Abstract: Abstract: The effect on Sediment-laden flow turbulence characteristics of Wetland plants simulated by flexible plastic tree growing and distribution of suspended sediment concentration were studied through the flume experiment under a certain hydraulic condition. The experimental results showed that the vertical velocity distribution of sediment flow with plant was no longer consistent with logarithm distribution with no plants in sediment flow, but for the "S"-type distribution. The turbulent intensity and Reynolds stress in longitudinal,transversal and vertical orientation were anisotropic, and the maximum and the location of the maximum increased with increasing plant height. Plant growth effects of sediment removal was significant. The vertical suspended sediment concentration increased with plant height decrease, the suspended sediment concentration gradually decreased along the flow direction.

Abstract: In this article, the prediction model of wheat water requirement was established by optimization algorithm BP neural network, and network topological structure was ascertained. Input-output variable were leafage electricity characteristic and irrigation volume. The BP neural network is trained by 60 sets of experimental data. The result of emulation showed that the BP neural network can solve the uncertainty and non-linear of the model, and the model has high precision.

Abstract: The monitoring and evaluation on silt arrester system of small watersheds involves monitoring indicators, data collection, analysis and evaluation etc. The Yellow River Water Conservancy Committee carried out a "small watersheds of the Loess Plateau model project" from 2005 to 2010 in the Yellow River sandy area. The project has 12 small watershed silt arresters, one of which is in Yonghe county of Shanxi province. This article takes the work of sediment transport monitoring in Yonghe silt arrester system as an example and describes the monitoring method, content, and finally analyzes the influence of silt arrester system construction and sediment transport on ecological environment.

Abstract: The effects of drought stress on the photosynthesis and dry leaf yield in the different Stevia rebaudina Bertoni germplasms of: IS-1, QF-1, QTZ4, JD-1 and AL-4 was studied with the pot method in greenhouse. The results indicated that the net photosynthetic (Pn), transpiration rate (Tr) and dry leaf production of stevia showed different degree changes with the continuing of drought-stress time. There was no significant change in Pn, Tr and dry leaf production in short-term drought-stress treatment(Ta:5d), but as the time of drought-stress continuing, the Pn were on the declining trend: the Pn of various materials in T2 (without irrigation for 10d) showed maximum decrease, they decreased for 28.85%, 47.04%, 43.03%, 43.61% and 42.25% than that in T1 (without irrigation for 5d), respectively. The variation trend of Tr in various materials were the same to the Pn. And it indicated that there was no appreciable impact on the dry leaf yield in the mild drought (without water for 5d), but with the drought stress continuing, the dry leaf yield of per plant became less and less. The varying degrees decreases of dry leaf yield in different materials with the same drought stress showed that different materials with different tolerance to drought stress.

Abstract: As the lack of topsoil resources, and the shortage of water resources, the ecological environment is extremely fragile in the pasture opencast coal mine area of China. Therefore, that the way to achieve the most efficient use of the limited topsoil resources in pasture area, plays a crucial role in land reclamation and ecological restoration. East II opencast coal mine in Datang, Inner Mongolia was taken as an example to analyze topsoil quality variation under different dump platform and slope reclamation modes in the pasture opencast coal mine area. The field investigation method was used in this paper. The study found that the mode "covering topsoil, overlying grass, grass grid, N fertilization, planting vanguard vegetation" in dump platform and "covering topsoil, overlying grass, grass grid, planting vanguard vegetation " in dump slope can lead to the best topsoil quality, though it still less than the original landscape topsoil quality level. The research can provide technical support and scientific basis for the pasture reclamation and ecological restoration.

Abstract: Variations in SA in various stands of first rotation larch plantation (FRLP) at different development stages (DDS), and in young stand (YS) of second rotation larch plantation (SRLP) in eastern montane area of northeast China and the relationship between SA and various forms of OP and IP were studied. Our results demonstrated that soil active acidity (pH value, SAA) in rhizosphere soil (RS) decreased continually with increasing stand ages from YS, half-mature stand (HMS), near mature stand (NMS) to mature stand (MS), but SAA in non-rhizosphere soil (NRS), exchange acidity (EA), exchangeable aluminium (EAL), total hydrolytic acidity (THA), and the ratio of EA to THA in RS and NRS increased apparently; when SA increased, total organic phosphorus (TOP), moderately resistant organic phosphorus (MROP), and highly resistant organic phosphorus (HROP) decreased in all stands of FRLP. For all stands except in HMS, when EA in RS increased, TOP, MROP, and HROP decreased. The correlation between labile organic phosphorus (LOP) and SAA, THA in RS reached highly significant level (HSL) at P=0.01 or significant level (SL) at P=0.05, respectively. Correlation coefficient (CC) between LOP and THA in RS diminished as stand ages increased. Positive correlation between moderately liable organic phosphorus (MLOP) and SAA in RS reached SL at P=0.05 or HSL at P=0.01 in all stands. In most stands, the close correlation existed between MROP and soil potential acidity (SPA), and between HROP and SPA, respectively.

Abstract: Variation in total phosphorus (TP), available phosphorus (AP), the forms of organic phosphorus (OP) and inorganic phosphorus (IP) in rhizosphere soil (RS) and non-rhizosphere soil (NRS) at different development stages in larch (Larix olgensis) plantations was quantitively studied through field investigation, chemical analysis and statistical test. The results indicated that: AP, O-P (occluded phosphate), TP, OP in RS exhibited a significantly or apparently decreased tendency over stand age, but IP, Ca-P (phosphate combined with calcium) and Fe-P (phosphate combined with Ferrum) in RS presented a significantly or apparently increased trend when stand age increased; Ca-P in NRS increased when stand age became larger; Fe-P in half-mature stand (HMS), AP and Fe-P in near mature stand (NMS), AP and Ca-P in mature stand (MS) in NRS was higher than in RS