毛乌素沙地油蒿(Artemisia ordosica)种群空间格局对比

以空间自相关分析、半方差分析和九项轨迹方差分析等方法对比研究了毛乌素沙地优良固沙小灌木油蒿(Artemisia ordosica)在不同沙地条件下的小尺度种群格局。结果表明:在半固定沙地上油蒿种群的空间自相关性和空间异质性较强,同时斑块与斑块间隙的分化较为显著;在固定沙地上油蒿种群的空间自相关性和空间异质性较弱,同时斑块与斑块间隙的分化较轻微。半固定沙地油蒿种群的空间格局可能受控于地表风沙流,因为频繁而强烈的风沙流可以通过淘汰非聚集植株促使油蒿种群发生斑块分化。聚集斑块不仅是半固定沙地油蒿种群生存的重要形式,而且是半固定沙地油蒿种群继续发展的基础。在半固定沙地上油蒿种群的面积扩增很可能通过斑块边缘的连续性扩张过程实现。固定沙地油蒿种群缺乏斑块分化的现象可能与种群盖度高和种内竞争剧烈有关。研究结果对流沙治理具有指导意义,当把油蒿人工移栽到流动沙地时,如果将其配置为斑块与斑块间隙交替排列的格局,将有助于提高流沙固定和植被恢复重建的效率。

Relationship between Framingham risk score and subclinical atherosclerosis in carotid plaques： an in vivo study using multi-contrast MRI

The assessment and management of early-stage atherosclerosis are important for the prevention of cardiovascular disease(CVD).In this study,we used multi-contrast magnetic resonance imaging(MRI) to investigate the carotid plaque feature in asymptomatic,at-risk subjects;we also evaluated the correlation between MRI findings and Framingham risk score(FRS).One hundred sixty-six asymptomatic individuals with risk factors for CVD underwent multi-contrast MRI.After the arterial morphology and plaque components were outlined,the differences in carotid plaque burden among the various risk categories were analyzed.The FRS analysis showed that high-risk individuals had thicker vessel wall and higher plaque lipid content than did low risk participants.A substantial proportion of advanced carotid plaques occurred in low and intermediate-risk groups.Multi-contrast MRI may provide incremental value to the FRS in managing asymptomatic at-risk population.