J Plant Ecol ›› 2020, Vol. 13 ›› Issue (5): 589-600.DOI: 10.1093/jpe/rtaa047

• Research Articles • Previous Articles     Next Articles

Growth, phenology and N-utilization by invasive populations of Gunnera tinctoria

Maurício Cruz Mantoani1,* , Alberto Benavent González2, Leopoldo García Sancho2 and Bruce Arthur Osborne1   

  1. 1UCD School of Biology and Environmental Science and UCD Earth Institute, University College Dublin, Belfield, Dublin 4, Ireland, 2Departamento de Farmacología, Farmacognosia y Botánica, Facultad de Farmacia, Universidad Complutense de Madrid, 28040 Madrid, Spain

    *Corresponding author. E-mail: mauricio.cruzmantoani@ucd.ie
  • Received:2020-07-02 Accepted:2020-07-15 Online:2020-07-21 Published:2020-10-01

Abstract:

Aims

Gunnera tinctoria is an unusual N-fixing plant species that has become invasive worldwide, generally in environments with a low evaporative demand and/or high rainfall. Amongst the many mechanisms that may explain its success as an introduced species, a contrasting phenology could be important but this may depend on an ability to grow and utilize nutrients under sub-optimal conditions. We examined whether G. tinctoria has an advantage in terms of a contrasting phenology and N-fixing capability, in comparisons with Juncus effusus, the native species most impacted by G. tinctoria invasions.

Methods

We made phenological assessments on a weekly or bi-weekly basis on long-established populations on Achill Island, Ireland, during 2016–2017. Data on leaf and inflorescence number, total leaf area, light interception and above-ground biomass were collected alongside measurements of soil temperature, moisture and oxidation–reduction potential. The significance of N-fixing ability for supporting seasonal growth was assessed using δ 15N isotopic assessments, together with in situ acetylene reduction measurements.

Important Findings

The timing of the initiation of growth of G. tinctoria and J. effusus varied between 2016 and 2017, with the earlier emergence and expansion of leaves of G. tinctoria, and the largest above-ground biomass associated with higher water availability. The early growth of G. tinctoria was dependent on preformed structures, with maximum canopy development occurring in late May, prior to that of J. effusus. Whilst N-fixation was observed in March, this made a more significant contribution to growth during the later stages of canopy development. Based on δ 15N isotopic analyses, early growth was predominantly associated with N-remobilization from the rhizomes, whilst seedlings were largely reliant on N-fixation. This emphasizes the importance of nutrient mobilization for early growth and shows that the importance of an N-fixing capability may vary developmentally, as well as during different stages of the invasion process.

Key words: growth, invasive species, Gunnera tinctoria, Juncus effusus, nitrogen fixation

摘要:

智利大叶草(Gunnera tinctoria)是一种不同寻常的固氮植物,已入侵到了世界各地,通常入侵到低蒸发需求和/或高降雨的环境。 在许多可以解释其作为一个成功的引入物种的机制中,差异性的物候特征可能起重要作用,但这可能取决于在次优化条件下生长和利用 营养物质的能力。我们研究了智利大叶草在物候和固氮能力方面是否具有优势,并将其与受智利大叶草入侵影响最大的本地物种灯芯草 (Juncus effusus)进行了比较。2016–2017年,我们每周或每两周对爱尔兰阿奇尔岛的长期种群进行物候学评估。在测量土壤温度,湿度和氧化还原电位的同时,收集了叶和花序数,叶总面积,光截获和地上生物量的数据。利用δ 15N 同位素并结合原位乙炔还原测量的方法评估了用于支持季节生长的固氮能力的重要性。研究结果表明,2016–2017年,智利大叶草和灯芯草开始生长的时间不同,智利大叶草叶片出现和展叶的时间较早,水分利用率较高时地上生物量最大。智利大叶草的早期生长依赖于预先形成的结构,5月下旬冠层发育达到最大,并且早于灯芯草。虽然在3月份观察到固氮作用,但这对冠层发育后期的生长有更显著的贡献。基于δ 15N 同位素分析结果表明,早期生长主要与根状茎的氮转移有关,而幼苗主要依赖于固氮作用。这一发现强调了养分调动对早期生长的重要性,并表明固氮能力的重要性可能在不同的发育过程中有所不同,并且其在入侵过程的不同阶段也是如此。

关键词: 生长, 入侵物种, 智利大叶草(Gunnera tinctoria), 灯芯草(Juncus effusus), 固氮