Extended Abstract (40K)2.4
Measured Airborne Concentration and Deposition rate of maize pollen (Zea Mays L.) Downwind of and Experimental Field
Benjamin Loubet, National Institute of Argronomic Research, Thiverval-Grignon, France; and N. Jarosz, B. Durand, X. Foueillassar, and L. Huber
Atmospheric transport of pollen is an essential vector of gene dispersion in the environment as well as crops interbreeding. For wind-dispersed pollens such as maize pollens, it is therefore crucial to understand the effects of microclimatic conditions on pollen transport in order to strengthen our knowledge of this phenomenon. However, the mechanisms underlying the emission, the dispersion and the subsequent deposition of maize pollen have not been extensively studied in the past. In this study, we present results of an experiment, in which airborne pollen concentration and horizontal fluxes as well as ground deposition rates were measured at several distances (x) downwind of a 20 m ´ 20 m maize field (Zea Mays L.). Standard micrometeorological, plant physiological and ultrasonic turbulence measurements were also performed in order to interpret the pollen concentration and fluxes measured. Airborne pollen concentration measured with rotorods ranged between 1 and 210 grains m-3 between x=3 m and x=10 m. It was combined with wind speed measurements to estimate the total horizontal flux of pollen below 5 m height, using the mass balance approach. These horizontal fluxes ranged between 10 and 480 grains m-1 s-1 at x=3 m and 3 and 210 grains m-1 s-1 at x=10 m. Pollen emission from the whole field was estimated from these fluxes to range between 2´107 and 8´108 grains day-1, which is roughly an order of magnitude smaller than pollen production by plants ranging between 2´108 and 5´109. Pollen deposition between x=3 m and x=10 m, was estimated as the difference between the horizontal fluxes at these locations. It ranged between 10 and 270 grains m-1 s-1, and was in close agreements direct measurements of deposition rates with flasks placed at the ground. The deposition rates ranged between 28% and 90% of the horizontal flux at x=3 m, which indicates that maize pollen is quickly deposited to ground. Pollen emission and its subsequent deposition to the ground are discussed in conjunction with the micrometeorological and turbulence conditions, in order to identify the most influencing microclimatic parameters.
Session 2, turbulence and dispersion in canopies Part 1
Monday, 20 May 2002, 1:30 PM-3:30 PM
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