Abstract
Agricultural grasslands are often cultivated as mixtures of grasses and legumes, and an extensive body of literature is available regarding interspecific interactions, and how these relate to yield and agronomic performance. However, knowledge of the impact of intraspecific diversity on grassland functioning is scarce. We investigated these effects during a 4-year field trial established with perennial ryegrass (Lolium perenne) and red clover (Trifolium pratense). We simulated different levels of intraspecific functional diversity by sowing single cultivars or by combining cultivars with contrasting growth habits, in monospecific or bispecific settings (i.e. perennial ryegrass whether or not in combination with red clover). Replicate field plots were established for seven seed compositions. We determined yield parameters and monitored differences in genetic diversity in the ryegrass component among seed compositions, and temporal changes in the genetic composition and genetic diversity at the within plot level. The composition of cultivars of both species affected the yield and species abundance. In general, the presence of clover had a positive effect on the yield. The cultivar composition of the ryegrass component had a significant effect on the yield, both in monoculture, and in combination with clover. For the genetic analyses, we validated empirically that genotyping-by-sequencing of pooled samples (pool-GBS) is a suitable method for accurate measurement of population allele frequencies, and obtained a dataset of 22,324 SNPs with complete data. We present a method to investigate the temporal dynamics of cultivars in seed mixtures grown under field conditions, and show how cultivar abundances vary during subsequent years. We screened the SNP panel for outlier loci, putatively under selection during the cultivation period, but none were detected.
Highlights
Whereas it is widely accepted that plant species richness and plant trait diversity have a positive effect on the functioning of ecosystems, recent progress in community ecology has emphasized the importance of intraspecific diversity [1,2,3,4]
The total dry matter weight (DMW) was higher when perennial ryegrass was sown in combination with red clover (Fig 2; seed compositions 3 > 1 and 4 > 2)
The DMW of the Meloni monoculture was higher than that of Merks, and this was more evident in the plots in which Merks or Meloni were combined with red clover
Summary
Whereas it is widely accepted that plant species richness and plant trait diversity have a positive effect on the functioning of ecosystems, recent progress in community ecology has emphasized the importance of intraspecific diversity [1,2,3,4]. A large part of the Earth’s terrestrial ecosystem is covered with grasslands [5], which support a wide range of ecosystem services including forage production, water regulation, maintenance of soil fertility and structure, carbon sequestration, and provisioning of habitat to many plant and animal species [6]. These services strongly depend on the grasslands’ ecosystem functioning, which in turn is affected by the diversity they harbor, i.e. by the variety of species, functional traits and genes present in the plant community [7]. Identification of relevant diversity effects in grassland communities and understanding the underlying mechanisms may support effective management strategies and sustainable grassland exploitation
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