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QuanLin MA Fang CHENG YouJun LIU FangLin Wang DeKuai ZHANG HuJia JIN Gansu Key Laboratory of Desertification Combating & Minqin National Studies Station for Desert Steppe Ecosystem Gansu Desert Control Research Institute Lanzhou China 《干旱区科学》2011,3(4):268-277
Sandy soils in arid,rain-fed environments have low and limited water content,which is a principal factor limiting vegetation development,and a key constraint controlling the structure and functions of the ecological systems in arid areas.The spatial heterogeneity of soil water content is a major soil property,and a focus of soil science and hydrology.On the southern edge of the Tengger Desert,sample plots were selected from mobile sand dunes in desertified lands that had been enclosed for 5,15 and 25 years,respectively.This study explored the dynamic and spatial heterogeneity of soil water content in these different layers of soil that were also in the reversion process of desertification.The results showed that the soil water content of the mobile sand dunes was highest when in the initial stages of the reversion process of desertification,while the soil water content in the 0-20 cm,20-40 cm and 40-60 cm layers of soil was 1.769%,3.011%,and 2.967% respectively,presenting a restoring tendency after 25 years of enclosure.There were significant differences,as a whole,in the soil water content among different restoration stages and different soil layers,respectively.Changes in soil water content,in different soil layers,at different restoration stages,exhibited exponential or spherical patterns.The spatial distribution of soil water content exhibited a mosaic patch pattern with obvious spatial heterogeneity.The ratio of the heterogeneity of spatial autocorrelation to gross spatial heterogeneity was greater than 50%.The gross spatial heterogeneity of the 0-20 cm layer of soil improved gradually,while those of the 20-40 cm and 40-60 cm layers improved initially,then weakened in the reversion process of desertification.This study revealed that restoration with sand-binding vegetation reduced soil water content,and increased its spatial heterogeneity in arid areas.However,after 25 years of vegetation-soil system restoration,the soil water content started to increase and its spatial heterogeneity started to weaken.These results will further benefit the understanding of the ecological mechanism between soil water and sand-binding vegetation. 相似文献
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Huaping Zhao Zhipeng Cui Yucheng Gu Yuxiu Liu Qingmin Wang 《Pest management science》2011,67(9):1059-1061
Natural tetramic acid derivatives have attracted a great deal of interest of chemists because of their structural features and the broad range of biological activities. This paper focuses on five naturally occurring tetramic acid derivatives reported to have phytotoxicity and discusses their common structural characteristics. Copyright © 2011 Society of Chemical Industry 相似文献
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2006年来,宁波出入境检验检疫局植检实验室曾多次从进境木质包装中首次截获并报道非洲伞滑刃组(africanus group)线虫,它们分别为非洲伞滑刃线虫(Bursaphelenchus africanus Braasch, Gu, Burgermeister, Brandstetter &; Metge, 2006)、伯氏伞滑刃线虫(B. burgermeisteri Braasch, Gu, &; Brandstetter, 2007)和欧斐切伞滑刃线虫(B. obeche Gu, Braasch, Zhen, Burgermeister &; Lin, 2008)。这些线虫均为作者最先截获。非洲伞滑刃组线虫的主要鉴定特征是:侧线4条;尾乳突7个(第3对和第4对靠近并位于交合伞起始处,第3对略位于第4对前并更靠近腹面);交合刺较直,中部有横纹,冠状体愈合(基顶和喙突不明显),远端无盘状突;后阴子宫囊约占肛阴距1 /2。目前尚无关于该组线虫媒介昆虫及致病性的报道。 相似文献
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