Abstract
AbstractThe mandate by the Energy Independence and Security Act of 2007 to increase renewable fuel production in the USA has resulted in extensive research into the sustainability of perennial bioenergy crops such as switchgrass (Panicum virgatum) and miscanthus (Miscanthus× giganteus). Perennial grassland crops have been shown to support greater aboveground biodiversity and ecosystem function than annual crops. However, management considerations, such as what crop to plant or whether to use fertilizer, may alter belowground diversity and ecosystem functioning associated with these grasslands as well. In this study, we compared crop type (switchgrass or miscanthus) and nitrogen fertilization effects on arbuscular mycorrhizal fungal (AMF) and soil nematode abundance, activity, and diversity in a long‐term experiment. We quantified AMF root colonization, AMF extra‐radical hyphal length, soil glomalin concentrations, AMF richness and diversity, plant‐parasitic nematode abundance, and nematode family richness and diversity in each treatment. Mycorrhizal activity and diversity were higher with switchgrass than with miscanthus, leading to higher potential soil carbon contributions via increased hyphal growth and glomalin production. Plant‐parasitic nematode (PPN) abundance was 2.3 × higher in miscanthus plots compared to switchgrass, mostly due to increases in dagger nematodes (Xiphinema). The higher PPN abundance in miscanthus may be a consequence of lower AMF in this species, as AMF can provide protection against PPN through a variety of mechanisms. Nitrogen fertilization had minor negative effects on AMF and nematode diversity associated with these crops. Overall, we found that crop type and fertilizer application associated with perennial bioenergy cropping systems can have detectable effects on the diversity and composition of soil communities, which may have important consequences for the ecosystem services provided by these systems.
Highlights
The mandate by the Energy Independence and Security Act of 2007 to increase renewable fuel production in the USA has resulted in extensive research into the economic viability and sustainability of bioenergy crops
We ask: (1) Do arbuscular mycorrhizal fungal (AMF) activity and diversity differ between switchgrass and miscanthus? (2) Do belowground nematode abundance and diversity differ between switchgrass and miscanthus? And (3) Does fertilization alter these belowground relationships?
Previous work in this Great Lakes Bioenergy Research Center (GLBRC) experiment found that switchgrass and miscanthus plots did not differ in soil organic matter, total soil carbon, active carbon pools, or slow carbon pools (Sprunger, 2015; Tiemann & Grandy, 2015), though these studies were conducted just three years after experiment initiation, and so may not reflect development of long-term differences among crops
Summary
The mandate by the Energy Independence and Security Act of 2007 to increase renewable fuel production in the USA has resulted in extensive research into the economic viability and sustainability of bioenergy crops. While current bioenergy production relies heavily on corn grain and residues (Wallander et al, 2011) there is growing interest in developing lignocellulosic biofuels produced from dedicated perennial energy crops because of their potential to enhance sustainability of bioenergy systems. Cultivation of perennial feedstocks produces half of the greenhouse gas emissions compared to annual grain feedstock (Robertson et al, 2011). These grasses can be grown on marginal lands which are not amenable to grain production (Gelfand et al, 2013). Management practices to enhance productivity of perennial cropping systems, such as fertilizer or pesticide applications, may eliminate or reduce many of the benefits provided by these perennial grasslands
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