毛乌素沙地天然臭柏居群有性更新幼苗动态研究

采用定位监测的方法,对毛乌素沙地天然臭柏居群有性更新幼苗动态进行6年的连续调查.结果表明:臭柏幼苗苗高的年均生长率为24.69%,冠幅的年均生长率达到44.48%,均呈逐年上升趋势.样方内幼苗总株数动态变化率均值31%,编号幼苗的平均死亡率8.88%,幼苗株数的增长大于幼苗的死亡,更新状况良好.幼苗高度大于20 cm的死亡株数占总死亡株数的7.89%,幼苗的死亡率呈现出随着幼苗的高度级的增加逐渐下降的趋势.臭柏幼苗生长速度以高度大于20 cm的植株最快,达到9.43 cm·a-1,幼苗的生长速度与幼苗的高度级成正比.对影响臭柏天然更新的气候因子进行线性相关分析表明:幼苗平均高度与冬季(11-3月)的降水量呈正相关关系;与夏季(6-8月)的气温呈负相关关系;幼苗冠幅与夏季气温呈负相关关系;幼苗的总株数动态变化率与冬季降水量和春季(4-5月)降水量均呈正相关关系,而编号幼苗的死亡率与年平均气温呈负相关关系.

Regenerative Seedlings Dynamics of Natural Sabina vulgaris Community in Mu Us Sandland

For the purpose of understanding dynamics of sexual regeneration seedlings of Sabina vulgaris communities in Mu Us sandland,we had investigated continuously for six years. Results indicated that:The annual average increment rate of seedlings height and crown width was about 24.69% and 44.48% respectively. The trendline of seedlings height and crown width was ascendling. The dynamic variation rate of tolal numbers of seedling was 31%, death rate of marked seedlings was 8^88%, indicating that the increased rate was higher than death rate, showing regenerative condition was well. Three seedlings that height over 20 cm were dead within five year, about 7.89% of total tead seedlings. The death rate of seedlings declined gradually with increasing of seedlings height. The growth speed of seedlings that height over 20 cm reached 9.43 cm5a~{-1}, which was the most quick compared with that of other height levels. Direct ratio was revealed between growth speed and seedlings height. At the same time, linear correlative analysis was conducted on selecting meteorologic elements that might influence natural regeneration. The result showed there was the positive correlation between the average height of seedlings and winter (Nov._Mar.) rainfall, and the negative correlation between the average height of seedlings and the summer (June_Aug.) temperature. The crown width of seedlings was negatively correlated with the summer temperature. There were the positive correlations between the dynamic variation rate of total seedlings and the precipitation in winter and in spring (Apr._May). Whereas the death rate of marked seedlings was related with the annual mean temperature negatively.