【摘要】 沿海防护林的结构状态是影响林分防护效能的关键因素,也是评价人工林生态系统稳定性和划分低效林类型的重要依据。通过不同年龄木麻黄低效林大量标准地的结构指标比较,结果表明低效林的冠幅、冠长和相对冠长均显著小于正常林,各生育阶段低效林的郁闭度均小于0.7,亦显著低于同龄的正常林。滨海前沿木麻黄低效林背风面平均风速下降幅度比正常林低5.5个百分点,其中20H 处距离比正常林降低10.4个百分点。沙地后沿16年生木麻黄低效林的林内风速下降比例比同龄正常林低17.2个百分点,32年生低效林的防风效能较正常林小16.8个百分点。木麻黄低效林的防风效能减小,是防护林结构不善的现实反映。更多还原

【Abstract】 Structure of protection forest is a major factor effecing on protection effeciency of stand,and also a important basis for evaluating stability of ecosystem of plantations and dividing types of lower-effective protec- tion forest.Comparison of structure indications from sample plots in the lower-effective protection forests at different ages showed,that crown width,crown length and relative crown length were obviously less than the normal stands,and crown density of the forest was below 0.7 in every growth period.The average wind speed on the lee side of the lower-effective forest of Casuarina in forward position of coast was 5.5 percent lower than normal forest,and 10.4 percent lower than the normal at 20 H.At rear position of the sandy land,wind speed in the forest at 16 years was 17.2 percent lower than normal forest of the same age,and 16.8 percent lower than the normal at 32 years.更多还原