as prairies and forests. Thompson said that it has
generally been found that an increase in biodiver-
sity increases ecosystem functioning — nutrient
cycling, rate of generation of biomass, pest resis-
tance, etc.
"In our research we looked at monocultures and
polycultures of commercial turfgrass species," he
said. "A monoculture would be Kentucky bluegrass
exclusively, for instance, while the polycultures
included mixes of tall grass fescues, fine fescues,
supine bluegrass, annual bluegrass, Kentucky blue-
grass, and micro-clover."
Thompson's research took place under con-
trolled greenhouse conditions for five months.
How did the turfgrass monocultures and polycul-
tures compare?
"In the polycultures, we found some moderate
increases in biomass and some moderate retention
of nitrogen," he said. "Interestingly, we also found
that the rhizospheres (root zone) of the polycultures
contained more diverse soil bacterial and fungal
communities. You could say that the below-ground
diversity mirrored the above-ground diversity."
Thompson said he doesn't yet know the full
implications of that biodiversity in terms of turf per-
formance, but he and Kao-Kniffin took away that
BEF theory might also be applied to lawns and, by
extrapolation, to other urban managed landscapes
such as ornamental gardens. Bearing in mind that
this greenhouse study would need to be replicated
in field settings, Thompson said this study shows
that turfgrass polycultures contribute to soil micro-
bial diversity and they enhance grass biomass while
decreasing leaching of nitrogen from soils. This is in
line with the consistent findings of BEF that biodi-
versity supports multiple ecosystem functions.
What are the implications of Thompson's
research for turf managers and landscapers? He said
that for the high-intensity, large-area turf managers
such as golf course supervisors, they have systems
in place for managing monocultures. Yet in roughs
and fairways, increasing turf diversity could be
beneficial. For the lower-intensity, lower-input
landscapes such as municipal parks and residential
lawns, turf polycultures are also viable.
Said Thompson, "Landscapers and turf care
companies should think about increasing diversity
in their landscape at all levels — genus, species,
and cultivar — and should think about their land-
scapes in terms of ecosystem services in addition to
aesthetics."
Michelle Sutton (michellejudysutton.com) is a
horticulturist, writer, and editor.
www.landscapeirrigation.com September 2014 Landscape and Irrigation 25
Among other things, Thompson's study looked at the level of fungal and bacterial diversity in the
rhizosphere (root zone) of monocultures and polycultures.
Photo by Grant Thompson
Grant Thompson's turf diversity experiment compared turf monocultures and polycultures in con-
trolled greenhouse conditions. Photo by Grant Thompson
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