Salinity and the small-scale distribution of three barrier island shrubs

The importance of salinity to small-scale distribution patterns was examined for three shrubs common on barrier islands of the southeastern United States. Field measurements focused on the salt marsh – upland interface zone on Hog Island, Virginia, where Myrica cerifera, Baccharis halimifolia, and Iva frutescens form distinct distributional zones. Although considerable variation in salinity occurred throughout the growth season (June through October), total soil chlorides and groundwater salinity were lowest for M. cerifera, intermediate for B. halimifolia, and highest for I. frutescens. All three species showed similar diurnal and seasonal patterns in stomatal conductance and leaf xylem pressure potential, despite the differences in salinity. However, a laboratory experiment revealed interspecific differences in water relations when the three shrubs were exposed to identical salinity regimes. The field data and water relations experiment indicated M. cerifera is least tolerant to salinity, I. frutescens ...

研究了盐度对美国东南部堰洲岛上常见的三种灌木的小尺度分布模式的重要性。野外测量集中在弗吉尼亚州霍格岛的盐沼 - 高地交界区，在那里，蜡杨梅（Myrica cerifera）、银叶菊（Baccharis halimifolia）和假苍耳（Iva frutescens）形成了不同的分布区。尽管在整个生长季节（6月至10月）盐度有相当大的变化，但蜡杨梅的土壤氯化物总量和地下水盐度最低，银叶菊居中，假苍耳最高。尽管盐度存在差异，但这三个物种在气孔导度和叶片木质部压力势方面都表现出相似的昼夜和季节模式。然而，一项实验室实验表明，当这三种灌木处于相同的盐度条件下时，它们在水分关系方面存在种间差异。野外数据和水分关系实验表明，蜡杨梅对盐度的耐受性最差，假苍耳……