The Liupan Mountains are located in the southern Ningxia Hui Autonomous Region of China, that forms an important divide between
landforms and biogeographic regions. The populated part of the Liupan Mountain Region has suffered tremendous ecological damage
over time due to population pressure, excessive demand and inappropriate use of agricultural land resources. To present the
relationship between land use/cover change and spatio-temporal variation of soil erosion, data sets of land use between the
late 1980s and 2000 were obtained from Landsat Thematic Mapper (TM) imagery, and spatial models were used to characterize
landscape and soil erosion conditions. Also, soil erosion in response to land use and land cover change were quantified and
analyzed using data from geographical information systems and remote sensing. Soil erosion by water was the dominant mode
of soil loss, while soil erosion by wind was only present on a relatively small area. The degree of soil erosion was classified
into five severity classes: slight, light, moderate, severe, and very severe. Soil erosion in the Liupan Mountain Region increased
between the late 1980s and 2000, both in terms of acreage and severity. Moderate, severe, and very severe eroded areas accounted
for 54.86% of the total land area. The lightly eroded area decreased, while the moderately eroded area increased by 368817
ha (22%) followed by severe erosion with 146552 ha (8.8%), and very severe erosion by 97067.6 ha (5.8%). Soil loss on sloping
cropland increased with slope gradients. About 90% of the cropland was located on slopes less than 15°. Most of the increase
in soil erosion on cropland was due to conversion of steep slopes to cropland and degradation of grassland and increased activities.
Soil erosion was severe on grassland with a moderate or low grass cover and on dry land. Human activities, cultivation on
steep slopes, and overgrazing of pastures were the main reasons for the increase in erosion severity. 相似文献
Arsenic is an environmental contaminant, its multiple effects on human tend to increase the rate of disease, cancer and other health problems. Some of long non-coding RNAs (lncRNAs) can be induced in major cellular processes such as necrosis, proliferation, and mutation. While the toxicity of arsenic is well established, the association between arsenic exposure and long non-coding RNAs has not been studied enough. This study investigated the association between arsenic and the expression of HOTAIR and LincRNA-p21 in vivo and vitro. In epidemiological studies, the expression of HOTAIR and LincRNA-p21 was increased after long-term arsenic exposure. HOTAIR and LincRNA-p21 expression were positively linked to monomethylarsenic acid (MMA), dimethylarsenic acid (DMA), inorganic arsenic (iAs), total arsenic (tAs), and MMA% and negatively linked to secondary methylation index (SMI). In A549 cells, arsenic exposure resulted in enhanced HOTAIR and LincRNA-p21 expression dose-dependently. The expression of HOTAIR was considerably high in the presence of NaAsO2 and MMA but showed no difference in DMA compared with control group. And LincRNA-p21 expression was increased in the presence of NaAsO2, MMA, and DMA. The expression of HOTAIR and LincRNA-p21 induced by iAs was much higher than that induced by MMA and DMA. Compared with the control group, treatment of A549 cells with NaAsO2/S-adenosylmethionine (SAM) and NaAsO2/glutathione (GSH) combination increased HOTAIR and LincRNA-p21 expression. The expression of LincRNA-p21 in combination of NaAsO2/GSH was significantly decreased compared with NaAsO2 alone. Besides, in the presence of arsenic, both of HOTAIR and LincRNA-p21 were upregulated significantly when P53 was knocked down. We revealed that inorganic arsenic, its methylated metabolites, and arsenic metabolism efficiency affect the expression of HOTAIR and LincRNA-p21.