氟污染区绿化树种的选择

前言凡使用含氟矿石(如冰晶石、磷矿石等)作原料的工厂,在碾磨、加热、酸化等过程中,以及利用含氟化合物作为接触剂、助熔剂的各种工艺过程的生产中,都会散发出大量的含氟废气与粉尘污染环境,给农林业生产及人     

Distribution of two species of sea snakes, <Emphasis Type="Italic">Aipysurus laevis</Emphasis> and <Emphasis Type="Italic">Emydocephalus annulatus</Emphasis>, in the southern Great Barrier Reef: metapopulation dynamics,marine protected areas and conservation

Aipysurus laevis and Emydocephalus annulatus typically occur in spatially discrete populations, characteristic of metapopulations; however, little is known about the factors influencing the spatial and temporal stability of populations or whether specific conservation strategies, such as networks of marine protected areas, will ensure the persistence of species. Classification tree analyses of 35 years of distribution data (90 reefs, surveyed 1–11 times) in the southern Great Barrier Reef (GBR) revealed that longitude was a major factor determining the status of A. laevis on reefs (present = 38, absent = 38 and changed = 14). Reef exposure and reef area were also important; however, these factors did not specifically account for the population fluctuations and the recent local extinctions of A. laevis in this region. There were no relationships between the status of E. annulatus (present = 16, absent = 68 and changed = 6) and spatial or physical variables. Moreover, prior protection status of reefs did not account for the distribution of either species. Biotic factors, such as habitat and prey availability and the distribution of predators, which may account for the observed patterns of distribution, are discussed. The potential for inter-population exchange among sea snake populations is poorly understood, as is the degree of protection that will be afforded to sea snakes by the recently implemented network of No-take areas in the GBR. Data from this study provide a baseline for evaluating the responses of A. laevis and E. annulatus populations to changes in biotic factors and the degree of protection afforded on reefs within an ecosystem network of No-take marine protected areas in the southern GBR. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Continuous measurement of oxygen concentration in citrus soil by means of a waterproof zirconia oxygen sensor

A limiting-current type of zirconia oxygen sensor has been developed and its efficiency was tested for the determination of oxygen in soil air. This oxygen sensor is waterproof and has a very short response time. By the use of the sensor, changes in soil oxygen concentration, due to undecomposed organic material and waterlogging, were observed. The sensor was found to be highly stable in the soil and suitable for continuous oxygen monitoring in the field.     

基于根部年轮与导管特征的黄土高原苜蓿生长衰退分析

紫花苜蓿作为黄土高原退耕还林还草工程的重要人工草本物种,对控制水土流失、植被固碳和生态环境改善等方面都发挥着重要生态作用;但是苜蓿草地在黄土高原普遍出现生长不可持续的特征,在第6年左右植被出现明显生长衰退现象。本研究在黄土高原4个降水梯度(280、400、500 mm和550 mm)的地点采集紫花苜蓿和自然对照草本物种:委陵菜的根部年轮样品,并分析了紫花苜蓿与委陵菜的年轮宽度和导管大小随年龄的变化趋势特征及与气候要素的相关关系。研究结果表明:在气候暖干化环境下,紫花苜蓿和委陵菜的年轮宽度随年龄增加都有不断下降的趋势,且在降水量偏低样点下降更为显著,这是由于植株在降水量偏低地点易遭受严重水分胁迫,以致无法满足生长所需的水分而造成根部生长速率明显减缓。紫花苜蓿根部导管大小随年龄增加均有明显下降趋势,在降水量偏低的样点下降趋势更加显著;这表明水分胁迫随年龄增加逐渐加剧,紫花苜蓿导管大小逐年下降以致不能满足自身生长的水分需求,植被生长呈衰退趋势,且在降雨偏低地区,苜蓿生长衰退出现时间较早。自然草本委陵菜根部导管大小随年龄增加均有明显上升趋势且在降水量偏低样点上升趋势更显著,这表明委陵菜通过增大根部导管大小、增加输水能力来满足随年龄增加不断上升的水分需求,这也说明委陵菜导管结构特征较好的适应了黄土高原干旱半干旱环境,生长处于可持续发展状态。