Lei L.,Xinjiang University |
Lei L.,Key Laboratory of Oasis Ecology of Ministry of Education |
Tiyip T.,Xinjiang University |
Tiyip T.,Key Laboratory of Oasis Ecology of Ministry of Education |
And 6 more authors.
Guang Pu Xue Yu Guang Pu Fen Xi/Spectroscopy and Spectral Analysis | Year: 2014
The present paper selects the Kuqa Oasis as the study area, studies spectrum characteristics of soil salinity, and establishes soil spectrum library. Through transforming and analyzing varying degrees of soil salinization reflectance spectra data in the typical study area, and selecting the most sensitive spectral bands in response to salinization, we established the measured hyperspectral soil salinity monitoring model, and by correcting the soil salinity monitoring model established by HIS image through scale effect conversion improved the model accuracy under the conditions of a regional-scale monitoring of soil salinization. The results show that both measured hyperspectral soil salinity monitoring model and HSI image soil salinity inversion model have good accuracy, model determination coefficient (R2) is higher than 0.57 and the model stability is better. Compared with the corrected HSI image soil salinity inversion model and uncorrected HSI image soil salinity inversion model, the coefficient of determination has been greatly improved, which increased from 0.571 to 0.681, and through the 0.01 significance level, the root mean square error (RMSE) value is 0.277. The correction HIS image soil salinization monitoring model can better improve the model accuracy under the condition of regional scale soil salinization monitoring, and using this method to carry out the soil salinization quantitative remote sensing monitoring is feasible, and also can provide scientific reference for future research.
Yao J.,Xinjiang University |
Yao J.,Key Laboratory of Oasis Ecology of Ministry of Education |
Yang Q.,Institute of Desert Meteorology |
Liu Z.,Xinjiang University |
And 2 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2015
Using monthly precipitation records from 122 meteorological stations in the arid region of Northwest China, the spatial and temporal distribution of precipitation were analyzed for the period 1961—2011. The Mann-Kendall trend test and Morlet wavelet analysis were utilized to detect the spatio-temporal distribution of the mean annual and seasonal precipitation. In the present paper, the Northwest arid area was divided into the northern Xinjiang region, the southern Xinjiang region, Qilian Mountains, Tianshan Mountains, Hexi Corridor region, and the Inner Mongolia Plateau region. The results obtained indicate that the mean annual precipitation (MAP) in the northwest arid region had a significant rising trend (P < 0.01), at a rate of 9.31 mm/ decade. The mean annual precipitation in the Qilian Mountains area rose the fastest, increasing by 38.67 mm/ decade; the second fastest was on the Tianshan Mountains, increasing by 16. 79 mm/ decade; the slowest increase was in the Hexi Corridor, southern Xinjiang, and western Inner Mongolia, increasing by 8.49 mm/ decade, 5.44 mm/ decade, and 5.09 mm/ decade, respectively. The Mann-Kendall test showed that the increasing trend of the mean annual precipitation in each area was statistically significant at P<0.05 level, except in western Inner Mongolia. A rising tendency of the mean annual precipitation was observed in 95.9% of the stations in the study region, but the amplitude shows regional differences. The Tianshan Mountains, Qilian Mountains, and northern Xinjiang show a rising tendency in all stations, followed by those in southern Xinjiang and the Hexi Corridor, whereas the lowest increase is in western Inner Mongolia, accounting for 77. 78% of the stations. Centers of the highest increase in mean annual precipitation were identified. for example, Yeniugou (52.5 mm/ decade) in the Qilian Mountains, Tianchi (22.8 mm/ decade) in the middle of the Tianshan Mountains, and Xinyuan (28. 3 mm/ decade) west of the Tianshan Mountains. There are seasonal differences in the rising trend of the mean annual precipitation. The rate of precipitation increased the fastest in spring, by 3.32 mm/ decade, followed by the rate in summer and winter, by 5.44 mm/ decade and 5.09 mm/ decade, respectively, whereas it is the slowest in fall (only 2.07 mm/ decade). The precipitation rate in winter was universal across the studied region, it was 98.36% in all stations. Summer precipitation rate presented regional differences; the precipitation rate was 79.51%. Abrupt changes in mean precipitation in the arid region and sub-region of northwest China are evident. The changes occurred in northern and southern Xinjiang and western Inner Mongolia in the middle of the 1980s, in the Hexi Corridor and the Qilian Mountains changes occurred in the middle of the 1970s, and in the Tianshan Mountains the changes occurred in 1991. The abrupt changes in the mean precipitation in each area were statistically significant at P < 0.05 level. The Morlet wavelet analysis showed that the precipitation has an approximate 4-year, 8-year, 12-year, and 22-year cycle in the studied region. According to the level of wet and dry, the rates for normal, abnormally dry, dry, wet, and extremely wet mean precipitation series were 32%, 12%, 24%, 16%, and 16%, respectively. Since the 1980s, precipitation has increased significantly; the rate of positive anomalous years has increased from 10% in the 1970s to 80% nowadays. Today, it is relatively wetter in the arid region of northwest China, with an obvious ongoing increasing trend. © 2015 Ecological Society of China. All Rights Reserved.
Long T.,Xinjiang University |
Long T.,Key Laboratory of Oasis Ecology of Ministry of Education |
Xiong H.,Beijing Union University |
Xiong H.,Key Laboratory of Oasis Ecology of Ministry of Education |
And 4 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2010
In order to optimize the micro-lysimeters (MLS) and improve its measurement accuracy, influential elements of accuracy was studied by the field testing without changing soil in 15 days. Result showed that the accuracy of all test treatments was high. The highest point was up to 97.40%. Whether the inner cylinder was drilled or not did not affect obviously the measurement accuracy. The accuracy of the drilled outside cylinder was higher than the undrilled ones, and the drilled holes were better to be equally distributed. Further more, the holes number was less than 36 when the diameter was 3 mm. The sealed outside cylinder could lower the measurement accuracy. The thinner material of sealed inside cylinder was and the more ventilative function was, the higher accuracy could be achieved. Moreover, when the space between inside and outside cylinder was smaller, the measurement accuracy also became higher. Dew studying results indicated that dew at night could markedly lower measurement accuracy of MLS. When the condensed quantum was above soil evaporation, MLS could not accurately measure out soil evaporation. Meanwhile, the measurement accuracy varied from time to time. The soil water content in the first 3 days was more, but the accuracy of MLS was lower than the later days. If there was available water supply, it was practicable without changing the MLS soil in 15 days.
Luo Y.,Xinjiang University |
Luo Y.,Key Laboratory of Oasis Ecology of Ministry of Education |
Gong L.,Xinjiang University |
Gong L.,Key Laboratory of Oasis Ecology of Ministry of Education
Chinese Journal of Ecology | Year: 2016
The ecological stoichiometry of root, stem and leaf of Phragmites australis in different habitats of Keriya River of the southern marginal zone of Tarim Basin, Xinjiang was studied, to explore the effects of habitats and organs on stoichiometry. The results showed that the mean concentrations of C, N and P in P. australis organs were in order of leaves > stems > roots, the C: N and C: P ratios were in order of roots > stems > leaves, whereas the N: P ratio was in order of leaves > stems > roots. The concentrations of C, N, P and their stoichiometric ratios in roots, stems and leaves differed with habitat. The concentrations of C in root, stem and leaf were significantly higher in riverbank than in oasis and desert. Stem N concentration was significantly lower in desert than in riverbank and oasis, while the concentrations of N in leaf and root were not significantly different among the three habitats. Leaf P concentration in oasis was significantly higher than in desert, and the concentrations of P in stem and root were significantly higher in ri-verbank than in oasis and desert. There was no significant difference in C: N ratio among root, stem and leaf. The C: P ratios in stem and root differed between riverbank and desert, while the ratio of N: P did not differ among the three habitats and was less than 14, which indicated that the growth of P. australis was mainly limited by N. The N concentration was positively correlated with the P concentration, indicating a consistent demand of N and P during P. australis growth. According to the factorial analysis of GLM, we concluded that the C and N concentrations and C: N and N: P ratios were mainly affected by the organs, while the P concentration and C: P ratio were mainly determined by the habitats. © 2016, Editorial Board of Chinese Journal of Ecology. All rights reserved.