The relationship between plant density and survival to water stress in seedlings of a legume tree

ABSTRACT Competition for soil water is one of the major processes that drive the assembly of plant communities, particularly in regions subjected to long dry seasons. The relationship between plant density and soil water competition has strong, but poorly understood, practical implications for population dynamics, restoration and conservation. We planted seedlings of the pioneer legume tree Senegalia polyphylla in containers and assessed the effects of plant density on their resistance to water stress. We completely eliminated the above-ground parts (stem and shoots) of randomly selected plants at 60-days post-planting in order to create three different densities of seedlings. We saturated the soil of the remaining seedlings and then deprived them of additional water until all seedlings died. We assessed the time elapsed from water suppression to wilting and death of individual plants. We found a strong negative relationship between plant density and time to wilting or death. Seedlings survived water stress 80% longer when density was reduced by two-thirds. Planting in lower densities or reducing density by thinning should be considered as strategies to enhance resistance to water stress in drought-prone regions.

摘要：土壤水分竞争是驱动植物群落构建的核心过程之一，在受长旱季影响的区域尤为突出。植物密度与土壤水分竞争之间的关联，对种群动态、生态修复与生物保护具有重要却尚未被充分阐释的实践意义。本研究将先锋豆科乔木多叶儿茶合欢（Senegalia polyphylla）的幼苗种植于容器中，探究植物密度对其水分胁迫抗性的影响。于种植后60天，对随机选取的植株完全去除其地上部分（茎与嫩枝），以构建三种不同的幼苗密度梯度。随后对剩余幼苗的土壤进行饱和灌溉，之后停止额外供水，直至所有幼苗死亡。本研究记录了从停止供水到单株幼苗萎蔫、死亡所经历的时长。研究结果显示，植物密度与幼苗萎蔫、死亡所需时长之间存在显著负相关关系。当密度降低三分之二时，幼苗在水分胁迫下的存活时间可延长80%。在干旱频发区域，可采用降低种植密度或通过间伐调整种群密度的策略，以提升植株的水分胁迫抗性。