A Weedy Business: Weed Composition on Prairie Edges

Weed management is a large part of landscaping and farming projects around the world. As excellent competitors with high dispersal rates, weed species have the ability to outgrow and out-compete native species. With this in mind, characterizing weed populations in prairies should be an integral aspect of prairie conservation projects. Knowing what types of weeds can grow under what sorts of conditions can help optimize such projects by reducing the interspecific competition caused by weeds.

Lososova et al. (2004) study the effects of a number of environmental factors on the composition of weed communities in Central Europe and aim to rank them in order of the significance of their influence on weed community patterning. The four main factors they test are altitude, season, year, and crop type, each of which variably affect several micro-factors such as temperature and soil pH. Based on statistical tests they conducted on releve data they collect from several databases, their results indicate that, out of the four tested factors, altitude had the highest influence on weed species richness and abundance and season, the second highest. These results helped me and my own team build hypotheses as we went into our project.

While our experimental site is very different from the large spatial range covered by the Lososova study, there were plenty of weed-affecting variables discovered that t translate onto our study. We examine the differences in weed abundance and diversity on either edge of a 220 metre long prairie strip. One edge of the strip runs along an active railway track and the other runs along a patch of lawn. Since the edge along the railway is sprayed in regular intervals to prevent growth onto the tracks, we thought there might be a difference in the weed communities on either side. Lososova et al. (2004) lays out an array of possible variables that might affect the weed abundance and richness on either edge of the prairie strip we are conducting our project in. In their study, altitude was the most significant factor affecting weed composition. They explain that soil pH varies greatly with altitude in their experimental region, suggesting that the pH might be a crucial variable to take into account when battling weeds. While altitude doesn’t vary greatly within our small experimental area, the regular spraying on one side may cause differences in soil pH which may, in turn, cause differences in weed communities along either edge.

                  Fig 1. Sampling on the lawn edge of our prairie strip. The railroad is in the background.

While the results from Lososova et al. (2004) build a solid foundation to kick off our weed project, they also generate some interesting contradictions when compared to the field of prairie conservation research. While previous prairie research has led us to believe that human influences are the largest cause of disruptions to the ecosystem, Lososova and her team suggest that natural geographical and climatological variability are more important for weed species composition than human-based factors such as crop type and other agricultural management. I wonder whether their results will extend to our study in the prairie strip? Furthermore, given that seasonality, including variables like temperature and precipitation, plays the second largest role in weed composition in the study, would the results of our experiment be different if we extended it into a long term project across various seasons?

References

Lososova, Z.,  M. Chytrý, Š. Cimalová, Z. Kropáč, Z. Otýpková, P. Pyšek, and L. Tichý. 2004.    Weed Vegetation of Arable Land in Central Europe: Gradients of Diversity and Species        Composition. Journal of Vegetation Science 15(3): 415-422.          http://www.jstor.org/stable/pdfplus/3236483.pdf?acceptTC=true&jpdConfirm=true