<正>采用不同龄级样方调查海南橡胶林林下植被的物种多样性，研究了胶林的植被类型及生物多样性的变化。结果表明：橡胶林下植物约有维管束植物207种、61个科和113个属，以耐阴性禾本科植物为主。经聚类分析，橡胶林下代表性的植被群落类型主要有8种：幼龄阳性杂灌木为主的群落、飞机草群落、白茅群落、耐阴性禾草（为主的）群落、假蒟群落、芒萁群落、蕨类群落、阳性禾草（为主的）群落。橡胶林生物多样性因降雨量、土壤理化性质、胶林年龄而异。降雨量越大胶林林下生物多样性越丰富。随着橡胶树年龄的增长，生物多样性有所下降。多样性指数与土壤有机质、全氮含量之间存在显著的正相关关系，与全磷、速效钾、全钾含量的关系不密切。

The changes of relative leakage of electrolytes and fresh weight from leaves of Jatropha curcas L. seedlings were studied after the seedlings were pretreated with drought (the water content of ground substance was less than 6.0%) for 72 hours, low temperature ((10± 1)℃) for 72 hours and salt solution (0.25 mol/L NaCl) for 120 hours, and during low temperature ((2± 1)℃) for 72 hours together with the controls. The results showed that the relative leakage of electrolytes of pretreated seedlings was markedly reduced and fresh weights of leaves were small affected compared with the control (CK). In other words, different stresses pretreatments could efficiently enhance the chilling resistance of J. curcas seedlings. It is suggested that J. curcas seedlings have an ability of cross-adaptation under the stress condition.