Abstract
High species and functional group richness often has positive effects on ecosystem function including increasing productivity. Recently, intraspecific diversity has been found to have similar effects, but because traits vary far less within a species than among species we have a much poorer understanding of the mechanisms by which intraspecific diversity affects ecosystem function. We explored the potential for identity recognition among the roots of different Pseudoroegneria spicata accessions to contribute to previously demonstrated overyielding in plots with high intraspecific richness of this species relative to monocultures. First, we found that when plants from different populations were planted together in pots the total biomass yield was 30 % more than in pots with two plants from the same population. Second, we found that the elongation rates of roots of Pseudoroegneria plants decreased more after contact with roots from another plant from the same population than after contact with roots from a plant from a different population. These results suggest the possibility of some form of detection and avoidance mechanism among more closely related Pseudoroegneria plants. If decreased growth after contact results in reduced root overlap, and reduced root overlap corresponds with reduced growth and productivity, then variation in detection and avoidance among related and unrelated accessions may contribute to how ecotypic diversity in Pseudoroegneria increases productivity.
Highlights
Biodiversity and ecosystem functioning are often positively linked (Balvanera et al 2006; Cardinale et al.2007, 2011)
Recent studies have shown that the root growth of some species increases in species mixtures compared with monocultures causing belowground overyielding, potentially due to reduced effects of plant pathogens in diverse assemblages (Mommer et al 2010; de Kroon et al 2012)
Most studies have focussed on the roles of species and functional group diversity on ecosystem functioning; a few recent studies have found that intraspecific diversity can have similar effects on ecosystem function (Crutsinger et al 2006; Fridley and Grime 2010; Cook-Patton et al 2011; Crawford and Rudgers 2012; Schob et al 2015)
Summary
Biodiversity and ecosystem functioning are often positively linked (Balvanera et al 2006; Cardinale et al.2007, 2011). A possible, but to our knowledge unexplored, mechanism for variation in productivity in ecotypic monocultures is different degrees of overlap among the roots of individual plants (see Schenk et al 1999; Novoplansky 2009). Root segregation may provide competitive advantages for resources or space for some individuals over others, functioning effectively as the establishment of territories (Schenk et al 1999) It is unknown how spatial root segregation might affect the growth of individual plants, and how this ramifies to community productivity. We explored potential mechanisms for the positive relationship between ecotypic diversity of P. spicata and productivity reported by Atwater and Callaway (2015) in which plots with high intraspecific richness overyielded relative to monocultures. We tested the hypotheses that (i) the total biomass of two interacting plants from different populations would be more than that for two plants from the same population and (ii) the growth rates of Pseudoroegneria roots would decrease more when contacting roots from other individuals from the same populations than when contacting roots from individuals from other populations
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