Reducing Pollen Dispersal using Forest Windbreaks

The adoption of genetically engineered (GE) crops has created a demand for practical methods to mitigate pollen dispersal and gene flow. The goal of this project was to measure the ability of a narrow forest windbreak to reduce downwind pollen fluxes from switchgrass ( Panicum virgatum L.), a North American grass and model biofuels feedstock. Switchgrass fields were established in two identical plots where one had a forest windbreak and the other was in an open (control) site. Switchgrass reproduction, pollen dispersal, wind speed, and wind direction were measured over two years. Daily release of switchgrass pollen peaked at 11:00-13:30 during a flowering period that lasted about 44 days. The best estimate for switchgrass pollen source strength (PSS) was 141 × 10 9 pollen/season/hectare for fields planted at commercial densities. The forest windbreak consistently decreased downwind switchgrass pollen concentrations by 333-20,000 fold compared to the control plot which had a 58-77 fold decrease due to downwind distance alone. These results suggest that forest windbreaks could be used as a barrier to reduce pollen dispersal and gene flow from switchgrass and other crops. Research Highlight A narrow forest windbreak greatly decreased downwind pollen concentrations from a switchgrass field suggesting that trees can reduce crop gene flow, enhance coexistence between farming systems, and provide ecosystem services.