DOI: 10.5061/dryad.qfttdz0g9
title: Plant diversity enhanced yield and mitigated drought impacts in intensively managed grassland communities

description: There is a global requirement to improve the environmental sustainability
 of intensively managed grassland monocultures that rely on high rates of
 nitrogen fertiliser, which is associated with negative environmental
 impacts. Multi-species grass-legume mixtures are a promising tool for
 stimulating both productivity and sustainability in intensively managed
 grasslands, but questions remain about the benefit of increasing the
 diversity of plant functional groups. We established a plot-scale
 experiment that manipulated the diversity of plant communities from a
 six-species pool comprising three functional groups: grasses, legumes and
 herbs (two species each). Communities were grown as monocultures, or
 mixtures of two to six species, following a simplex design. This allowed
 us to quantify species’ identity effects and functional group interaction
 effects. To investigate the impact of severe weather events, main plots
 were split and two levels of water supply, ‘rainfed’ and a two-month
 experimental drought, were applied. Mineral nitrogen fertiliser was
 applied at 150 kg ha-1 yr-1, and a Lolium perenne monoculture received 300
 kg ha-1 yr-1 (300N) as a highly fertilised comparison. Annual aboveground
 biomass was measured for two years. We found a strong positive effect on
 yield due to functional group interactions. Multi-species communities with
 three functional groups yielded more than the best-performing monoculture
 over a large range of different relative abundances of the three
 functional groups. The highest diversity community outperformed the 300N
 L. perenne under rainfed conditions. Although species’ monoculture yields
 were generally reduced by the experimental drought, the interaction
 effects were not affected by drought and remained sufficiently large for
 the six-species mixture under drought to have similar yields to both the
 best-performing monoculture and the 300N L. perenne under rainfed
 conditions. Synthesis and applications. Plant diversity can result in
 higher yields, mitigate the yield risks associated with extreme weather
 events, and displace fertiliser inputs and their embedded greenhouse gas
 emissions. Multi-species swards offer a practical, farm-scale management
 action to enhance the sustainability of intensive grassland production.
description: We established a plot-scale experiment in 2017, that manipulated
 the diversity of plant communities from a six-species pool comprising
 three functional groups: grasses, legumes and herbs. Communities were
 grown as monocultures, or mixtures of two to six species, following a
 simplex design. Proportions of each species are specified as follows:
 Lp=<em>Lolium perenne, </em>Pp=<em>Phleum pratense,
 </em>Tp=<em>Trifolium pratense</em>,
 Tr=<em>Trifolium repens,</em> Ci=<em>Cichorium
 intybus,</em> Pl=<em>Plantago lanceolata.</em> To
 investigate the impact of severe weather events, main plots were split and
 two levels of water supply, ‘rainfed’ (Drought=<em>0</em>) and
 a two-month experimental drought (Drought=<em>1</em>), were
 applied after random allocation within each plot. Mineral nitrogen
 fertiliser was applied at 150 kg ha-1 yr-1 (XN=0), and some replicates
 of <em>Lolium perenne</em> monoculture received 300 kg ha-1
 yr-1 (XN=1). Annual aboveground biomass was measured for two years. The
 variable 'AnnualYield' is the sum of the dry matter harvested
 for each year for each subplot (Split) in 2018 and 2019. This dry matter
 was measured on seven occasions throughout the year, by cutting at 4.5cm
 height with a Haldrup F-55 harvester. Note that plot 27 had not been sown
 with the correct proportions
 (Split= <em>35</em> and <em>86</em>), thus data
 from this plot is missing.