I am using an invasive, saprotrophic lawn fungus (Amanita thiersii) as an integrator of carbon and nitrogen cycling in lawns.
Dear Erik Hobbie,
The use of C4 grass in Tennessee has definitely increased in recent years. Bermuda is the C4 grass in this area and mostly tall fescue is the C3 cool season species.
If temperatures are indeed increasing there may be a move to more use C4 species and they can have advantages for high termperature and droughty conditions.
Nitrogen is the biggest nutrient applied to lawns and recommendations I have seen are about the level for a maize crop 140 to 200 kg/ha N.
In maize the fertilizer application level has been quite level and efficiency of N conversion has improved.
In lawns the economics are not over riding and most applications are weed and feed which are supported by advertisement of major producers.
I believe more and more people are using lawn services and it would be interesting to consult them.
I bet there is sizable increase in organic lawn management but I bet it is still a distinct minority.
Good luck in your investigation could you tell us more about the lawn fungus project goals?
Sincerely Paul Reed Hepperly
Hi Paul,
Thank you very much for your reply. Amanita thiersii is mostly invading in the Midwest but I imagine that lawn care practices have mostly shifted similarly with time across the country. To give you more background, below I give the title and draft abstract of the study. Superscripts and subscripts were lost when I pasted.
Cheers,
Erik
The invasive fungus Amanita thiersii integrates site nitrogen and carbon dynamics across C3 and C4 lawns
Amanita thiersii is an invasive, saprotrophic fungus that is expanding its range rapidly in Midwestern lawns. Carbon isotope (δ13C) values from sporocarps collected between 1982 and 2009 correlated positively with mean annual temperature (MAT) and negatively with mean annual precipitation (MAP), reflecting presumably the relative use of C3 and C4 grasses in lawns. In addition, δ13C values correlated positively with the Suess effect, the drop in δ13C and increase in CO2 concentrations caused by anthropogenic fossil fuel combustion, with a coefficient of 4.9 rather than the expected value of 1. The apparent 13C discrimination accordingly increased by ~2.3‰ (check?) as CO2 concentrations rose by ~40 ppm over this time period. This enhanced 13C discrimination probably reflects increased assimilation by A. thiersii of C3-derived carbon, either resulting from management changes (increases in the planted proportion of C3 lawn grasses over time) or increased quantum yield and productivity of C3 grasses relative to C4 grasses with rising CO2 concentrations. Sporocarp nitrogen isotope (δ15N) values correlated positively with MAT and negatively with MAP, with a negative interaction of MAT with year. The negative correlation with MAP was three times stronger than in natural grasslands, suggesting that fertilization and watering of lawns in drier environments has enhanced 15N-depleted losses much more than in wetter environments. Isotopes in Amanita thiersii may integrate shifts over the last 50 years in lawn maintenance practices, soil nitrogen dynamics, and the physiological responses of turf grasses.
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