河北省沿海地区气候变化特征及相关分析

利用南堡盐场气象站1966～2005年40 a逐年各月的气温、降水量、蒸发量、日照时数和风速等资料,应用气候倾向率、Mann-Kendall非参数检验和相关分析等方法,分析了各气候要素的变化特征。结果表明：年平均气温、年平均最高气温和年平均最低气温呈上升趋势,且均通过了99%显著性检验,气候倾向率分别为0.41℃/10 a、0.31℃/10 a和0.46℃/10 a;年日照时数和年蒸发量呈减少趋势,且通过了99%显著性检验,气候倾向率分别为-224.1 h/10 a和-147 mm/10 a;年降水量和年平均风速变化趋势不显著;年平均气温与年日照时数和年蒸发量为负相关关系,年日照时数与年蒸发量为正相关关系,年平均气温升高不是日照时数和蒸发量减小的直接原因,日照时数是影响蒸发量的1个主要因子。     

Water uptake of maize roots under conditions of non-limiting soil water content

The relation between the root density distribution of a horizontally homogeneous maize root system and the vertical root extraction patterns was studied. A field data set of root density distribution during the vegetation period were used together with the root extraction patterns calculated from soil water content distributions. Only those time intervals during which crop transpiration was potential were considered. Therefore, the shape of vertical root extraction patterns depends only on the relevant root morphological parameters. The maximum depth-dependent root extraction rate of maize was assumed to be proportional to the root density ddstribution. The root density distribution can then be used as a parameter of the root system for the evaluation of the ‘sink term’ in water uptake models.