Characterizing variations in soil particle size distribution in oasis farmlands-A case study of the Cele Oasis

Characterizing soil particle size distributions (PSD) and their variation is an important issue in environmental research. In this study, fractal theory was used to analyse the soil PSD and its variations in the Cele Oasis, which is located at the southern margin of the Tarim Basin. The characteristics of the soil PSD were then evaluated to identify the primary factors that influence soil PSD. The results showed that the fractal dimension (D) values ranged from 2.11 to 2.27, and that there were significant differences among groups. Furthermore, the D values showed a significant positive correlation with fine particles (<50 mu m) and soil organic matter contents. According to a comparative analysis of D values, the utilization years of farmlands had a significant influence on PSD, while the difference in the spatial distribution of farmlands did not. These results indicated that long-term and effective tillage management of the farmlands will be beneficial to keeping and improving the states of the soil PSD and other soil properties. (C) 2009 Elsevier Ltd. All rights reserved

Ordination as a tool to characterize soil particle size distribution, applied to an elevation gradient at the north slope of the Middle Kunlun Mountains

Soil particle-size distribution (PSD) is one of the most fundamental physical attributes of soil due to its strong influence on other soil properties related to water movement, productivity, and soil erosion. Characterizing variation of PSD in soils is an important issue in environmental research. Using ordination methods to characterize particle size distributions (PSDs) on a small-scale is very limited. In this paper, we selected the Cele River Basin on the north slope of the Middle Kunlun Mountains as a study area and investigated vegetation and soil conditions from 1960 to 4070 m a.s.l. Soil particle-size distributions obtained by laser diffractometry were used as a source data matrix. The Canonical Correspondence Analysis (CCA) ordination was applied to analyse the variation characteristics of PSDs and the relationships between PSDs and environmental factors. Moreover, single fractal dimensions were calculated to support the interpretation of the ordination results. Our results indicate that a differentiation of 16 particle fractions can sufficiently characterize the PSDs in CCA biplots. Elevation has the greatest effect on PSDs: the soil fine fractions increase gradually with increasing elevation. In addition, soil pH, water and total salt content are significantly correlated with PSDs. CCA ordination biplots show that soil and vegetation patterns correspond with one another, indicating a tight link between soil PSDs and plant communities on a small scale in arid regions. The results of fractal dimensions analysis were rather similar to CCA ordination results, but they yielded less detailed information about PSDs. Our study shows that ordination methods can be beneficially used in research into PSDs and, combined with fractal measures, can provide comprehensive information about PSDs. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved

Comprehensive eco-environmental effects of the shelter-forest ecological engineering along the Tarim Desert Highway

In this work, we report a comprehensive study about the eco-environmental effects of the shelter forest along the Tarim Desert Highway, including the effects on aeolian environment, soil, micro-climate, biodiversity, and groundwater. The results show that: (1) The movement of windblown sand near the ground surface was affected by the shelter forest. The wind speed and sediment transport rate in the shelter forest decreased by 64%-80% and 87.45%-99.02%, respectively. In addition, there were also significant changes in the sand flux structure, the sand grain size, and the deflation and deposition on the ground surface. (2) Compared to the natural mobile sand, the soil bulk density in the forest area decreased while the total salt content, the total porosity, and the water content increased. In addition, the soil fertility was significantly improved in the forest area, and showed the "first rapid, then slow" variation pattern. (3) The shelter forest showed positive effects on the micro-climate. Within the 6 m height above the ground, the air temperature in the shelter forest at different heights was lower than that in the mobile sand, while the air humidity was higher, while, the soil temperature was also lower in the shelter forest than mobile sand. (4) The number of soil microbial species increased significantly with the improvement of habitat in the shelterbelt. However, the population of different species was not distributed evenly across the surveyed area. (5) Currently, no significant effects of groundwater-pumping and forest-irrigation water have been found on the groundwater level and its salinity. The variation amplitude of both groundwater level and salinity was at the level of centimeters and 1g/L, respectively. No obvious variation trend has been observed

Effects of different management intensities on soil quality of farmland during oasis development in southern Tarim Basin, Xinjiang, China

Soil quality is a key environmental factor in developing sustainable agricultural. In the oases located at the southern margin of the Tarim Basin of Xinjiang, China, agriculture is the main land use type. However, management intensities differ in the oases and in the process of oasis growth. In 2004, four experimental fields were established in the Cele oasis, representing four typical land-use types according to local farmers tillage practices, namely newly cultivated land (NEF), a field with normal fertilization (NMF), a field with high fertilization (HMF), and a field in the oasis' interior (OIF), in order to analyze the effects of land-use type on soil nutrient content. Additionally, soil from an uncultivated control plot (CTP) was analyzed for comparison. The soil quality index (SQI) and deterioration index (DI) were used to evaluate the effects of different land-use type. Sustainable yield index (SYI) was calculated to evaluate sustainable productivity of these land-use types, based on 4 years of data. Our results indicate (i) statistically significant differences in SOM, total nitrogen N (TN), total phosphorus (TP), and available phosphorus (AP) between the different farmlands; (ii) NEF, in the desert-oasis ecotone, had the lowest soil quality, even lower than CTP, and lowest indicator values; (iii) fertilization of NMF and HMF in the desert-oasis ecotone had a positive effect on soil nutrient content; however, sustainable productivity of these farmlands is low, and much ground water is consumed; and (iv) farmland (OIF) in the oasis interior had the highest values in all assessments. Our study indicates that farmland in the desert-oasis ecotone should be reclaimed prudently, using sustainable development insights