J Plant Ecol ›› 2020, Vol. 13 ›› Issue (5): 554-562.DOI: 10.1093/jpe/rtaa044

• Research Articles • Previous Articles     Next Articles

Variability of water supply affected shoot biomass and root depth distribution of four temperate grassland species in monocultures and mixtures

Eamon Haughey1,2, *, Jennifer C. McElwain1 and John A. Finn2   

  1. 1 Botany Department, School of Natural Sciences, Trinity College Dublin, Dublin 2, Ireland, 2 Teagasc, Environment Research Centre, Johnstown Castle, Wexford, Ireland

    *Corresponding author. E-mail: ehaughey@tcd.ie
  • Received:2019-09-16 Revised:2020-05-26 Accepted:2020-07-15 Online:2020-07-21 Published:2020-10-01

Abstract:

Aims

Research on the effects of extreme rainfall events on ecosystem function has primarily focussed on drought or flooding events, which usually include changes to mean or total rainfall, annually or over a season. However, less is known about the effects of increased rainfall variability without change to mean or total amounts. We investigated the effects of increased variation of water supply on shoot and root biomass as well as the distribution of root biomass of four grassland plant species, grown in monoculture and mixture communities.

Methods

Perennial ryegrass (Lolium perenne L., shallow-rooting grass), chicory (Cichorium intybus L., deep-rooting forb), white clover (Trifolium repens L., shallow-rooting legume) and red clover (Trifolium pratense L., deep-rooting legume) were established in mesocosms. Four plants of the same species were grown in monoculture communities and one of each species grown in four-species communities. Water supply was manipulated such that; compared with a baseline level with low variation in water supply, there was a treatment with medium variation (±40%) and another with high variation (±80%). Shoot and root biomass were measured, and vertical root distribution models fitted.

Important Findings

Compared with the low variation treatment, shoot biomass was significantly reduced under high variation for white clover, red clover and four-species communities. Under all conditions, four-species communities produced more shoot and root biomass than predicted by species performance in monoculture (overyielding). Under increased water variation, chicory monocultures allocated a higher proportion of root biomass to deeper soil layers while the total root biomass of white clover monocultures was significantly reduced. These results indicate that increased variability of water supply can negatively affect the shoot and root biomass production of single and multi-species grasslands. There is a need for further investigation of water variation effects on the functioning of multi-species grassland systems at field 

Key words: climate variability, rainfall, forage production, root depth distribution, grassland ecology

摘要:
极端降雨事件对生态系统功能影响的研究主要集中在干旱或洪水事件,通常包括全年或某个季度的平均或总降雨量的变化。然而,在不改变平均量或总量的情况下,增加降雨变异性的影响还很少被研究。本研究调查了增加水分供应变异性对单一栽培和混合栽培下4种草原植物的地上和根系生物量以及根系生物量分布的影响。将多年生黑麦草(Lolium perenne L., 浅根),菊苣(Cichorium intybus L., 深根),白车轴草(Trifolium repens L., 浅根)和红车轴草(Trifolium pratense L., 深根)种植在中型实验生态系统中。单一栽培条件下种植4株同种植物,混合栽 培条件下每种植物各1株。水分供应变异性处理设置低中高3种水平:与低变异水分供应处理相比,另设置一个中度变异处理(±40%)和高度变 异处理(±80%),测定了地上和根的生物量,拟合了根系垂直分布模型。研究结果表明,与低变异处理相比,白车轴草,红车轴草和4种植物 混种群落的茎生物量在高变异处理下显著减少。在所有处理中,4种植物混种群落产生的茎和根生物量比单一栽培(超产)中物种表现所预测的要多。在水分变异增加的情况下,菊苣在单一栽培下根系分配了更多的生物量到更深的土层,而白车轴草在单一栽培下根系总生物量显著降 低。这些结果表明,水分供应变异的增加会对单一栽培和混合栽培草地的地上和根的生物量产生负面影响。在野外尺度上,水分变异对多物种 草地系统功能的影响需要进一步研究。

关键词: 气候变异, 降雨, 饲草生产, 根系深度分布, 草地生态系统