Abstract
Little is known about the effect of diversity surrounding a focal plant species on the belowground community under that species. At least two alternative hypotheses exist. First, studies involving a range of ecosystems and taxonomic groups have shown that changes in diversity in one group of species can promote diversity in other groups. Alternatively, many studies in soil ecology have shown that belowground communities are strongly determined by the dominant aboveground species. To better understand the role of aboveground diversity on belowground communities, we examined soil nematode communities directly under Panicum virgatum (switchgrass) in areas of high and low surrounding plant diversity. We found that soil nematode diversity under switchgrass in areas of high plant diversity (native prairies) was not significantly different from soil nematode diversity under switchgrass in areas of extremely low plant diversity (switchgrass monocultures), indicating that an agricultural monoculture can maintain high levels of belowground diversity on a plant scale. However, reduced plant diversity surrounding focal switchgrass plants resulted in a compositional shift in the belowground community toward fewer herbivorous nematodes. This evidence for the influence of surrounding diversity on belowground communities under a focal plant species is a major shift in perspective from the conventional view on belowground community ecology. Furthermore, the work has broad implications for ecological perspectives on agricultural systems.
Highlights
Many studies in community ecology involving a broad range of ecosystems and taxonomic groups have revealed a general pattern showing that diversity in one trophic group often influences and promotes diversity in other trophic groups within a community (Wills et al 1997)
We looked at the influence of aboveground plant diversity in the immediate vicinity of a dominant plant species on the soil community directly under the dominant species
Our study focused on soil nematode communities directly under Panicum virgatum in native prairies and in switchgrass monocultures
Summary
Many studies in community ecology involving a broad range of ecosystems and taxonomic groups have revealed a general pattern showing that diversity in one trophic group often influences and promotes diversity in other trophic groups within a community (Wills et al 1997). Insect diversity is positively correlated with prairie plant diversity in a temperate grassland (Haddad et al 2001). Communities may be structured by the dominant species as opposed to diversity per se (Gilbert et al 2009). The identity of the dominant plant species in an experimental grassland system strongly influenced the invasibilty of the entire community (Emery and Gross 2007). Our understanding of intertrophic diversity interactions has largely been informed by studies in aboveground communities (De Deyn and Van der Putten 2005). Studies on aboveground and belowground community interac-
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