<正>对不同演替阶段30个群落样地的数量特征进行研究。结果表明：（1）在自然恢复过程中，灌木林阶段物种丰富度和物种多样性均高于乔木林阶段，前者均匀度也稍高于后者，而乔木林阶段生态优势度有所增加；（2）退化喀斯特森林群落具有较为明显的优势种，通常为1～2种；（3）退化喀斯特森林群落的生物量随自然恢复演替的进程不断增大，群落生物量构成也随自然恢复演替的进程而发生变化，灌木林的草本层和灌木层平均生物量都远高于乔木林的相应值，分别是乔木林的5.4倍和3.5倍；（4）群落的连续带指数分析反映了不同群落类型在群落演替中所处的地位。

There are three frequently encountered configurations,in the FET design, which are common source, gate and drain circuits. By comparing them carefully and making effective use of FET epitaxial growth, a reversed channel common-drain circuit has been chosen to make the GaAsFET oscillator. Some electrical specifications, were also analyzed systematically, such as characteristic frequency, maximum output power level, single pulse power gain and resonant frequency,etc. Through the processes of production and adiustment, the completed GaAsFET oscillator has met the demands of the project design. Its frequency band was from 4 GHz to 4. 3 GHz and the output power level came up to more than 100 roW. The final oscillator has the features of tiny errors,great stability and a great practical value.