Population density of tropical forest frogs: relation to retreat sites

The forest frog Eleutherodactylus coqui defends specific sites for retreats and nests in the Luquillo Forest, Puerto Rico. The hypothesis that shortages of nest and retreat sites limit population size was tested by placing 100 bamboo frog houses in plots measuring 100 square meters in areas of high frog density. These new sites were readily adopted by adult frogs. After one year, experimental plots had significantly more nests and frogs of all sizes than did control plots.     

冬小麦的春化作用和单叶积温

单叶积温已被用于小麦(Triticum aestivum L.)动态发育模型中描述叶的阶段性发育.春化作用控制冬小麦发育进程.本试验旨在确定春化作用是否影响冬小麦产生叶片所需积温.在人工气候室和室外钵中分别种植"Stephens"的预春化处理和未春化处理萌芽种子.室外钵栽植的植株自然地通过春化阶段,播前春化处理对生长、发育和开花均没有影响.人工气候室里两种方法处理萌芽种子的植株在经春化处理的植株达到开花之前,单叶积温或主茎总叶数没有差异.未春化处理植株继续产生分蘖直到试验结束,然而春化处理植株于拔节期停止分蘖.这些结果支持了在摸拟春化处理和未春化处理的冬小麦幼苗的叶片发育时,单叶积温应用一个恒定值的观点.然而也显示出了摸拟作物叶片冠层发育需要塑造合理的春化效应模型.