梭梭幼苗的存活与地上地下生长的关系

近几十年来,全球气候变化以及人类活动的加剧,导致古尔班通古特南缘荒漠地区的降水与地下水位发生显著的改变,这些改变必然导致荒漠植物用水策略的适应性变化。以古尔班通古特沙漠南缘原始沙漠中建群种梭梭的1年生幼苗为研究对象,对气象因子、土壤含水率、梭梭幼苗死亡率、地上地下高度(深度)、面积、生物量状况进行了全生长期的连续监测,以期探明1年生梭梭的生长、生存规律。结果表明:梭梭幼苗在土壤水分较为充沛的4—6月生长迅速,但随着土壤水分的消耗,7月地上地下部分都出现了不同程度的萎缩,在8月又恢复生长。在全年生长期中,幼苗死亡率基本呈现逐月下降的趋势。这说明在干旱来临前,梭梭幼苗快速生长以抢占更多资源;当遭遇干旱时,幼苗通过同化枝凋落有效的维持了根系供水与地上部分需水之间的平衡,保证了存活同化器官的光合能力,从而降低了死亡率。同时,幼苗以牺牲地上部分生长为代价将更多的光合产物转向根系,使得幼苗能够获得更多的水分保证其生长、生存。

The survival and above/below ground growth of Haloxylon ammodendron seedling

Due to the current background of global climate change and heavy human activities, the precipitation and groundwater table on the southern edge of the Gurbantunggut desert have significantly changed, which could lead to variations in water use strategies of local plants. In our study, growth of the seedlings of Haloxylon ammodendron was investigated to reveal its growth traits and adaptability in the southern edge of Gurbantunggut desert. The results showed that the seedlings grew well from April to June when the soil water content was high, with the consumption of soil moisture, the above-and below-ground part of plant began to fall off, and then recovered growing in August. Mortality of seedlings showed a downward trend in the whole growth period. It suggested H. ammodendron seedlings could occupy more resource through rapid growth before the drought period, and falling of the assimilating branches in the drought period could maintain balance between water supply deficit and water consume of the assimilating organs. This morphological adjustment reduced seedlings mortality effectively. Also, more photosynthate was assigned toward root could ensure seedlings survival and recovered growth quickly at proper water conditions.