Advanced Materials Research Vols. 518-523

Abstract: In recent years, salt intrusion in estuaries of the Pearl River has become a serious problem for local water supply in dry season. Water level, circulation and salinity around mouth of the Modaomen estuary in spring and neap were examined respectively through field measurements. The results indicated that mild water level process reinforced baroclinic action to cause notable circulation downstream, which was more durable in neap. And, the current in lower layer was generally faster than that in upper layer during the neap circulation. These two probably resulted in higher bottom salinity in neap than in spring within the upper mouth, which was on the contrary to the lower mouth as well as the open coastal sea nearby. The activity of observed salt wedge by tidal force within the lower mouth contributed to local salinity variation. Thus, the saline processes and distributions in the estuary mouth depended on cooperation of estuarine circulation and tidal driving in the absence of river flow and wind.

Abstract: Soil water conditions would determine plant root distribution and influence plant growth. To explore the suitable soil water conditions for different kinds of drought-resistance shrubs, we studied root distribution characteristics of Haloxylon ammodendron, Nitraria sibirica Pall. and Calligonum mongolicum under different irrigation treatment in the hinterland of Taklimakan Desert. At the more irrigation amount in one time, H. ammodendron had more root biomass, fine root surface area, the deeper of the root distribution layer and the deeper of the peak value of the fine root surface area, the root distribution of C. mongolicum shifted to the horizontal direction of the surface layer. The spatial root distribution of N. sibirica Pall. were all between C. mongolicum and H. ammodendron, the less amount of annual irrigation of N. sibirica Pall, the more root biomass and fine root surface area and the peak value of fine root surface area shifted to the surface area. In conclusion, the best irrigation treatment of H. ammodendron was as follows: the irrigation time was 14 hours, irrigation interval was 20 days in spring and autumn and 15 days in summer, the total amount was 661.5 kg, the rate of saving water was 17%; C. mongolicum and N. sibirica Pall. were 6 hours per time, 15 days in spring and autumn, 5 days in summer, the total amount was 588 kg, the rate of saving water was 26%. These results may help to establish scientific irrigation management for sustainable development of Tarim desert highway.

Abstract: Abstract: Xiaojiang drainage basin is one of the regions suffering from serious erosion and ecological degeneration due to the climate, geological and geomorphological conditions and the heavy human activities. Reforestation, which has been done since 1980s in the region, is an effective measure for the ecological restoration. Four types of plantations, i.e., Eucalyptus spp., Acacia mearnsii, Leucaena leucocephala and Pinus yunnanensis are investigated in the sample plots. Development processes and community structures of the tree layers, shrub layers and grass layers are studied with the “ergodic hypothesis” method and the index of species richness, coverage, importance value and Shannon_Wiener index et al, and erosion control abilities of the four types of plantations are compared in this paper. The result shows that the plantations of Acacia mearnsii and Leucaena leucocephala grow faster, which have higher crown coverages and stronger erosion control abilities than that of Pinus yunnanensis and Eucalyptus spp.. The Pinus yunnanensis plantation has a higher secondary understory biodiversity, the Eucalyptus spp. plantation has a high secondary understory biodiversity, but the plantations of Acacia mearnsii and Leucaena leucocephala have low secondary understory biodiversities. Study in this paper shows that the four types of plantation have distinct effects in promoting plant diversity and have different erosion control abilities. So plantation species selection and association mode should be considered in the process of reforestation for ecological restoration.

Abstract: Dust supply is important to sandstorm occurrence as well as wind regime. Dust supply is closely related to groundsurface conditions showed by these index soil physical composition, soil moisture, vegetation cover, human activities. The physical conditions of groundsurface in the Tarim basin is distributed in a ringlike pattern. From edge to hinterland, there are various landscapes in turn as follow: mountains, piedmont pluvial and alluvial fans and plains and shifting desert. At the same time, in this turn, different types of soil has been developed there: brown desert soil, ancient oasis cultivated soil (anthropogenic-alluvial soil), swamp soil, desert forest meadow soil, paddy soil, saline soil, takyr soil, shifting sandy soil, and so on. Through comprehensive analysis, some conclusions were drew as the follow: (1)shifting deserts are the major dust source of sandstorm occurred in the hinterland and the south fringe of the Taklimakan Desert; (2)cultivated soils are another dust source of sandstorm occurred in oasis areas disturbed by high-intensity human activities; (3) gobi deserts in upper of piedmont pluvial and alluvial fans and desert forest areas on alluvial plains are the potential dust sources with high dust-emitting ability that can be activiated by human activities.

Abstract: Based on the three-year standard runoff plot experiment observation through typical runoff plots from 2006 to 2008, this study quantitatively analyzes the effect and difference of runoff and sediment reduction with different soil and water conservation measures in red-soil slope land of Poyang Lake Basin in order to solve the soil losses problems. Surface vegetation, especially the cover of near surface vegetation has extremely obvious effect on runoff and sediment reduction. When the optimal allocation of different layers of vegetation, good effects can be achieved. The function of runoff and sediment reduction of contour cultivation is more obvious than that of downslope cultivation. The reduction effect of terrace is good and grass planting on the ridge of terrace is much better.

Abstract: In this paper the effects of two types of tillage (conventional tillage-CT and zero tillage-ZT) with three different soil fertilization patterns(chemical fertilizer, chemical-organic fertilizer and organic fertilizer) on soil rapidly available nitrogen, rapidly available phosphorus, rapidly available kalium and soil respiration flux in ridge cultivation maize fields were studied. The results indicate that in 2005 and 2006, soil rapidly available nitrogen of two tillage type in different fertilization treatments were organic fertilizer (OF) > chemical-organic fertilizer (OCF) > no fertilizer (CK) > chemical fertilizer(CF); Except For OF, the decreasing of soil available nitrogen contents of each fertilization treatments for ZT were more than those of CT. Rapidly available phosphorus for ZT were OCF >OF > CF >CK, and for CT were OCF > CK >OF> CF; rapidly available kalium for ZT were OCF >OF > CK > CF. soil respiration for different of fertilization patterns for ZT were OCF >OF > CK > CF. In ZT, soil available N and P had close relation with soil respiration flux, especially in OCF treatment. While in CT, soil available N had close relation with soil respiration flux.

Abstract: Thiourea (TU) and dicyandiamide (DCD) were chosen as inhibitors to curb fertility loss of storage urine. For the summer radish experiments, the result shows that the weight of summer radish added urine +TU were 92.2g, and the weight of fruit of summer radish added with urine + DCD, urine and without fertilizer were 72.1g, 52.4g and 40.6g, respectively. On the other hand, compared with the blank, the yield of summer radish fertilized by urine, urine + DCD and urine + TU were increased by 29.1%, 77.5% and 127%, respectively. While, the yield of radish fertilized by urine + TU were increased by 37.6% and 27.9 %, compared with urine and urine + DCD. However, for lettuce experiments, the results show that the average weight of the lettuce added urine +TU were 72.7 g, and the weight of lettuce added with urine + DCD, urine and without fertilizer were, 62.2g, 52.4g and 37.6g, respectively. Compared with the blank, the yield of lettuce fertilized by urine, urine + DCD and urine + TU were increased by 39.4%, 65.4% and 93.4%, respectively. On the other hand, the yield of radish, which fertilized by urine + TU were increased by 38.7% and 16.9 %, compared with urine and urine + DCD. All of these results indicated that TU and DCD have positive effects on fertility loss control, but TU was significantly more effective than DCD, despite the application dose of TU was smaller than DCD.

Abstract: To improve farmland water use efficiency in the semi-arid area, the field experiment of whole film covering with the spring maize was conducted. The results showed that the whole film mulching (WFM) and the conventional film mulching (CFM) could both improve the maturity effective panicles. The sequence of increasing magnitude was: WFM 2a > WFM 1a> CFM 1a> CK. The CFM could significantly improve grain yield and water use efficiency, however, the WFM could reach to a very significant level. The yield effect between the application of the WFM 2a and the WFM 1a were propinquity, the difference was not obvious. The application of WFM 1~2a was effective maize cultivation pattern in semi-arid region, which was for realizing the water-saving and yield increased purposes.

Abstract: In this paper, we firstly defined the potential debris flow gully. And then using the data of different gullies in Wenchuan earthquake hit areas, we built a discrimination model of potential debris flow gully by Fisher Linear Discrimination Analysis method. Finally, the model was used to discriminate the gullies in Jinxihe catchment, in Anxian County. Potential debris flow gully is a kind of special gully which is in a special evolution phase of the gully when the gully has the happening possibilities of debris flow but no debris flow records. Because potential debris flow can often pose more serious disasters, discrimination of potential debris flow gully is important for disaster prevention and mitigation. To build discrimination model of potential debris flow gully, a database of different gullies in quake-hit areas was established and six discrimination indices were selected based on cause analysis of debris flow. Using the database and the six discrimination indices, we built the discrimination model by Fisher Linear Discrimination Analysis method. The discrimination model was used to discriminate the gullies in Jinxihe catchment. Discrimination results showed that the discrimination model was effective and feasible in discriminating potential debris flow gullies, but it still needs further revised and perfected.

Abstract: There are two challenges in front of Guizhou rocky desertification area’s development: environment protection and economic development. There are several ways to solve this contradiction, and grassland agriculture is one effective method. Combined with the management situation of rocky desertification, the writer took field survey to the whole province, got knowledge of the grassland source and the main issues in the rocky desertification area. Some scientific responses were raised for exploring or using the limited grassland resource.