水分胁迫下荒漠地区2种草本植物生物量分配策略

Strategies for Biomass Allocation of Two Desert Plant Species under Water Stress

水分胁迫是荒漠地区生态系统结构和功能变化的主要驱动力。分析水分胁迫下,不同生长阶段荒漠植物生物量在地上-地下的分配比例,对精确估算地下有机碳存储量有重要的理论意义。通过盆栽控制实验,设置对照、中度和重度胁迫的水分梯度,选取荒漠地区2种草本植物涩荠(Malcolmia africana)和角果藜(Ceratocarpus are-narius),分析其生物量在地上-地下的分配比例变化。结果表明:无论水分胁迫存在与否,总生物量累积均符合Sigmoidal生长模型;水分胁迫对植株早期发育阶段总生物量的累积无明显影响,但显著减少了发育后期总生物量的累积;植株每生长10 d,涩荠和角果藜叶片占总生物量的比例分别减少8.9%～10.6%和3.1%～3.4%。几乎等同于茎所增加的比例。水分胁迫使得地下生物量显著增加,但总生物量的累积仍以地上部分为主;根冠比在整个生长过程中呈4个渐变的阶段。

Water stress is one of the main driving forces to affect the structure and function of ecosystem in arid and desert regions. The objective of this study was to analyze the relationship between aboveground and belowground biomass of two desert plant species at their growth stages under water stress. The processes of biomass accumulation and allocation of Malcolmia africana and Ceratocarpus arenarius at their growth stages were researched by pot experiment. Three water supply treatments, i.e. the water-control treatment （CK）, moderate water stress （LW1） and severe water stress （LW2）, were applied in the experiment. The results showed that whether there was water stress or not, the accumulation of total biomass was fitted well by Sigmoidal growth model. The effect of water stress on total biomass accumulation was not obvious at early growth stages, but was significantly reduced at late stages. The proportions of leaves in total biomass of M. africana and C. arenarius were decreased by 8.9% - 10.6% and 3.1% - 3.4% respectively with the plant growth every 10 days, which were almost equal to the increased proportion of stems. Water stress could significantly increase root biomass, but the total biomass accumulation was still dominated by the increase of aboveground biomass. There were four visible stages of root-shoot ratio change during the whole growth stage of these two plant species.