POLLEN DISPERSAL AND DEPOSITION IN AN AGROECOSYSTEM AT PROVINCE OF BUENOS AIRES, ARGENTINA.

The aim of this study is to analyze factors and mechanisms involved in dispersal and deposition of airborne pollen captured with Tauber type traps in a 20 x 20 m plot of Helianthus annus cultivation and accompanying weeds and to investigate the relation of these processes with the vegetation structure and dynamics from cultivation to its senescence over a 14 week period. Weekly samples obtained with pollen traps showed a significant change in the deposition due to a filter effect and dispersal patterns due to source variations during the time elapsed. A conceptual and interpretative model for both processes and its relation to pollen sources is proposed. Our results showed that in the study site, the leaves development of Helianthus annus produced a pollen filter effect. Furthermore the cultivation and weeds phenology was linked to deposition and dispersal of pollen, whose sources were the study plot, local or extralocal distances. Three periods could be characterized according to the presence of pollen contents coming from different pollen sources. The first period was characterized by deposition of local and extralocal pollen types such as Caryophyllaceae, t. Physalis, etc, the second by pollen originate from the study plot (such as Helianthus annus) and the third by a combination of all three sources. [ABSTRACT FROM AUTHOR]