ABSTRACT

Plant communities within many of the world’s waterways are losing diversity where flows are stabilised for security and enriched from land-use intensification. Understanding the phenotypic plasticity of plant species that protect and/or store their below-ground biomass during floods may help to promote them if problematic, overabundant species – like Phragmites australis and Typha domingensis – are less plastic. To investigate mechanisms underlying the plasticity of two cosmopolitan (Phragmites, Typha) and two endemic (Cycnogeton procerum, Cyperus gymnocaulos) macrophytes in response to disturbance (fluctuating hydrological regimes) across a nutrient gradient, we analysed historical data from pond experiments with single-species pots. Our analyses showed fluctuating water levels in nutrient-enriched conditions reduced total biomass in all species, with 65% and 46% reduction in Phragmites and Typha respectively. Contrary to expectations, only Cycnogeton allocated a higher proportion of biomass to protect (root) and store (rhizome) resources in fluctuating water levels and nutrient-enriched conditions (45% versus 23% in stable regime), and was the most plastic by allocating 75% more biomass to belowground in the least favourable conditions. Our results indicate that removing impediments to stochastic flooding disturbance could benefit some endemic species while reducing the productivity of overabundant Phragmites and Typha in environments enriched by human activity.

摘要

世界上许多水道中的植物群落正在失去多样性，而在这些地方，流量因安全而稳定，并因土地利用集约化而丰富。了解在洪水期间保护和/或储存地下生物量的植物物种的表型可塑性可能有助于促进它们，如果有问题的、过多的物种——如芦苇和香蒲——的可塑性较差。研究两种世界性植物（芦苇、香蒲）和两种地方性植物（Cycnogeton procerum、Cyperusgynocaulos）可塑性的潜在机制）大型植物响应营养梯度的干扰（波动的水文状况），我们分析了来自单一物种盆栽池塘实验的历史数据。我们的分析表明，在营养丰富的条件下，水位波动会减少所有物种的总生物量，芦苇和香蒲分别减少 65% 和 46% 。与预期相反，只有Cycnogeton在水位波动和营养丰富的条件下（45% 对 23% 在稳定状态下）分配更高比例的生物质来保护（根）和储存（根茎）资源，并且通过将 75% 的生物质分配到地下而成为最具塑性的在最不利的条件下。我们的结果表明，消除随机洪水干扰的障碍可以使一些地方性物种受益，同时降低人类活动丰富的环境中过多的芦苇和香蒲的生产力。