Photosynthesis and respiration of managed C3 turfgrass fields under various light conditions

Abstract

Net ecosystem CO2 exchange from managed C3 turfgrass (Kentucky bluegrass, Poa pratensis) fields under various light conditions (irradiance level of 100, 60, 49, 20 ) was measured with the closed dynamic chamber method from spring to fall. Net ecosystem CO2 exchange was measured in situ using a 'clear' chamber, and total ecosystem respiration rate was measured using a 'dark' chamber. Both respiration rate and the amount of biomass were smaller in the shaded plots. Ecosystem respiration normalized with respect to soil temperature decreased in summer, coinciding with the seasonal change in plant biomass. The amount and seasonal change of biomass, not temperature, mainly governed the ecosystem respiration of the C3 turfgrass fields under various light conditions. The light curve of gross photosynthesis, which was calculated by adding the respiration rate to net ecosystem exchange at each measurement time, was compared between plots. There were no obvious differences between plots in the response of gross photosynthesis to light in spring, and a decline of the maximum photosynthesis at an optimal irradiance was observed in summer, except in the darkest plot.

Seasonal fluctuations in growth/decline and single-leaf gas exchange of C3 turfgrass fields under various light conditions

“…In terms of gross photosynthesis of the ecosystem at the same site, a summer decline in maximum photosynthesis at optimal irradiance was observed in all plots (Kosugi et al, 2010). This trend differed from the single leaf Vcmax, which did not show a post-summer decline in Plot A.…”

Effects of seasonal fluctuations in gas exchange parameters on estimation of single-leaf photosynthesis of C3 turfgrass grown under different light conditions

“…Kentucky bluegrass that had been grown in open fields was laid in plot A in April 2004, in plot C in February 2005, and in plot D in September 2005 in a 1:1 blend of decomposed granite soil (Masa soil) and sand. These plots were the same as in our previous reports (Kosugi et al, 2010;Matsubara et al, 2011). In this study, we made no observations in plot B. Observations were conducted from January 2006 to December 2007.…”

“…We established three plots with different light regimes. Plot A was a nursery (600 m 2 ) in an open (unshaded) area, and plots C and D were located in a stadium (9,279 m 2 ) with a retractable roof that is usually open but is surrounded by buildings that screen the sun, depending on the season and time of day (Kosugi et al, 2010). Plot C was shaded in both the early morning and the late afternoon.…”

“…No differences were observed between plots in the spring, and a decrease in photosynthetic ability was observed after early summer, depending on the level of shade, and was coupled with a decline in biomass. Kosugi et al (2010) also measured net ecosystem CO2 exchange and total ecosystem respiration of C3 turfgrass vegetation using the closed dynamic chamber method. They reported that canopy photosynthetic capacity decreased in summer, with no differences between plots.…”

Partitioning of respiratory CO2 fluxes in a managed C3 turfgrass field

“…The in situ acrylic chambers were 0.2 m tall and had stainless steel collars 0.1 0.2 m in size that were inserted 0.03 m into the soil (as in Kosugi et al, 2010). At the time of measurement, the lid and midportion of the chamber were closed and air was circulated in a loop between the chamber headspace and IRGA at a flow rate of 1.0 L min -1 using a pump (MP-15CF; Shibata, Tokyo, Japan).…”