Submitted to: Global Change Biology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/1/2006
Publication Date: 1/1/2007
Citation: Ziska, L.H., George, K., Frenz, D.A. 2007. Establishment and persistence of common ragweed (Ambrosia artemisiifollia L.) in disturbed soil as a function of an urban-rural macro-environment. Global Change Biology. 13:266-274. Interpretive Summary: Ragweed is a common weed usually found in disturbed areas. As such, it is a problem in both agriculture and in vacant lots. Although we know that ragweed needs disturbance in order to grow, how long it persists in a given area following disturbance is unclear. However, knowing how long ragweed persists at a given location helps to determine its ability to produce seed and pollen. In this experiment, we grew ragweed using the same fallow soil in three different outdoor environments that differed in the amount of carbon dioxide and temperature. The high carbon dioxide, high temperature environment was the city of Baltimore; while the high temperature, normal carbon dioxide environment was a nearby suburb. A rural farm location at normal carbon dioxide and temperature acted as the control. The experiment conducted over a three year period showed that while the growth and pollen production of ragweed was initially highest in the city environment, by the end of three years, other plants, particularly perennial plants, had crowded out the ragweed, with a dramatic drop in population. There are indications that this may also be occurring in suburban and rural ragweed populations, but at a slower rate. Overall, these data suggest that macro-climatic differences associated with the urban heat-island effect while initially increasing ragweed productivity, may reduce the longevity of ragweed and its subsequent growth and pollen production. These data will be of interest both to farmers and growers as well as ecologists, health care workers and the lay public.
Technical Abstract: Although ragweed is a significant agricultural weed as well as a recognized cause of allergic rhinitis, little work has focused on its establishment and persistence following natural or anthropogenic disturbance. To examine how climate change could alter the longevity of this species during secondary succession, we exposed fallow agricultural soil from 2001 with a common seed bank population to an in situ temperature and carbon dioxide concentration [CO2] gradient along an urban-rural transect from 2002-2004. The urban induced increases in [CO2] and temperature observed along this gradient were consistent with most short-term (i.e. ~50 year) global change scenarios regarding [CO2] and air temperature. Measurements over this period demonstrated that ragweed biomass along the transect was initially greatest at the urban site, peaking in 2003. However, by the Fall of 2004, urban ragweed populations had dwindled to a single plant, while the suburban ragweed community now demonstrated maximum biomass. Parallel changes in pollen production as a function of urbanization were also inferred over this time period (2002-2004) based on previously established relationships between pollen release and ragweed biomass. The decline in urban ragweed populations was associated with a demographic shift in plant types from annuals to perennials, indicating an accelerated rate of succession for this location. Overall, these data suggest that macro-climatic differences associated with the urban heat-island effect while initially increasing ragweed productivity, may reduce the longevity of ragweed during secondary succession and its subsequent growth and pollen production.