降雨格局变化对白刺幼苗根系形态特征的影响

为探讨荒漠植物白刺幼苗根系形态对降雨格局变化的响应特征,设置3个降雨量梯度(W-、W、W+)和2个降雨间隔时间梯度(T、T+)进行人工模拟试验,结果表明,1)降雨量和降雨间隔时间对白刺幼苗根系形态有不同程度的影响,且降雨量的作用效应更大。2)降雨量相同时,延长降雨间隔时间均使白刺幼苗主根长、根系平均直径、根体积和根表面积减小,但总根长和根系生物量和总生物量却增加,在高降雨量条件下(W+)延长降雨间隔时间白刺幼苗比根长和比表面积分别增加了45.09%和20.20%,但差异均不显著。3)降雨间隔时间相同时,降雨量减少30%仅使主根长平均增加12.06%,总根长、根平均直径、根体积和根表面积等根系形态指标均显著减少,比根长和比表面积变化不大;降雨量增加30%仅使比表面积显著增加,其余各形态指标差异均不显著,低降雨量条件下(W-)主根长与根冠比达到最大,其他指标均在高降雨量条件下(W+)达到最大。4)对8个根系形态参数进行主成分分析,根系生物量、总根长、总根表面积、比根长、比表面积和根体积6个根系生态参数受降雨格局影响显著。

Response of the root morphology of Nitraria tangutorum seedlings to precipitation pattern changes

A global climate model has predicted changes in precipitation patterns, with extended periods of time between precipitation events; larger individual precipitation events are expected to increase. Furthermore, with global climate change, local area rainfall patterns have also changed. Over 80 years, the annual precipitation in arid areas of central Asia has generally shown an increasing trend. Such an altered precipitation regime will significantly alter the temporal supply of water to desert ecosystems, and thus have important effects on ecological processes, which could ultimately affect species composition and biological diversity. Root growth of seedlings is the most important stage in plant regeneration and the most sensitive in the plant life cycle to environmental conditions. The responses of root morphology to changes in precipitation and the ability of seedlings to adapt can directly affect the success of subsequent seedling establishment, and may affect regeneration dynamics. Nitraria tangutorum, a super-xerophytic shrub, exhibits a strong tolerance for drought, cold, and saline-alkali soil. The shrub vegetation type in which N. tangutorum is the dominant species is an important vegetation type in the deserts of northwestern China. As a result, N. tangutorum is the key species for the revegetation of these arid and semiarid areas. Most research has examined the impacts of the amount of precipitation on this species rather than the effects of both the amount and interval of precipitation. To understand how climate-driven changes in precipitation can affect desert plants, especially the response of the root morphology to precipitation patterns change, we conducted a controlled experiment with two factors: precipitation quantity (natural precipitation as a control, reduction of 30% and increase of 30%) and interval (time elapsed between two precipitation events; 5 or 10 days). The results showed that root morphological characteristics were influenced by total precipitation and precipitation interval, the former playing a more significant role than the latter. Under the same precipitation condition, the main root length, root diameter, root volume, and root surface area were decreased, total root length, root biomass, and total biomass were increased by extended precipitation intervals, and specific root length (SRL) and specific root area (SRA) were considerably increased by 45.09% and 20.20% in high precipitation, respectively, but the difference was not significant. For the same precipitation condition interval, the main root length was increased by 12.06%, total length, diameter, volume and surface area were significantly decreased, and SRL and SRA were basically unchanged in precipitation reduced by 30% conditions. The SRA increased significantly, but the other index differences were not significant. The main root length and root-shoot ratio were largest in low precipitation, but others (total root length, root surface area, average root diameter, root volume, root biomass, SRL and SRA) were larger in high precipitation conditions. Eight characteristics of root morphology were analyzed using principle component analysis. The characteristics of root biomass, total root length, total root surface area, SRL, SRA and root volume were significantly affected by precipitation pattern changes. We suggested that the root morphology of N. tangutorum seedlings was mainly affected by the amount of precipitation. However, the precipitation interval could be as important as the amount of precipitation for the root morphology of N. tangutorum seedlings. Increasing the precipitation amount and extending the precipitation interval (less frequent but higher volume precipitation events) enhanced root growth and population regeneration.