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item Ziska, Lewis
item Bunce, James
item Goins, Ernest

Submitted to: Oecologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/28/2004
Publication Date: 3/1/2004
Citation: Ziska, L.H., Bunce, J.A., Goins, E.W. 2004. Initial changes in plant population and productivity during secondary succession along an in situ gradient of carbon dioxide and temperature. Oecologia. 139:454-458.

Interpretive Summary: One of the methodological difficulties faced by scientists who do research on global change and plant biology is simulating future climatic conditions. The two most likely climatic conditions are increased temperature and increased carbon dioxide. Although these can be simulated in a greenhouse or growth chamber, it is difficult to simulate both outdoors, in "real-world" conditions. Here we describe an effort to use cities as a surrogate for climate change. Utilizing a gradient of temperature and carbon dioxide from downtown Baltimore to an organic farm 40 miles away, we found that city environments were very similar to those predicted for the rest of the world in 2050 (i.e. hotter with more carbon dioxide). Using this gradient we examined plant growth and reproduction from a common seed bank from fallow farm soil which had been distributed equally to each of three sites along the gradient (urban, suburban and rural). Overall, we found that urbanization resulted in greater aboveground biomass and reproduction of lambsquarters, a ubiquitous weed. While more information is needed, these are the first "real-world" data to suggest how plant biology will be affected in fallow soil in response to climate change. These data will therefore be of value to urban planners, plant biologists and those interested in global warming.

Technical Abstract: Because of methodological difficulties, few community-level studies have been conducted to determine the impact of rising atmospheric carbon dioxide concentrations [CO2], in combination with global warming. To examine the impact of climate change on secondary sucession, we exposed fallow agricultural soil to an in- situ temperature and CO2 gradient between urban, suburban and rural areas and measured species number and aboveground biomass over the growing season. Along the gradient, average daytime CO2 concentration increased by 20% and maximum (daytime) and minimum (nighttime) daily temperatures increased by 1.6 and 3.3 oC, respectively in an urban relative to a rural location. These urban-induced environmental changes are consistent with most global change scenarios. Although plots at all sites were dominated by a single pioneer species, lambsquarter (Chenopodia album), the number of species present at the beginning (suburban, urban) and at the end (urban) of the growing season increased with increasing CO2 and air temperature. Overall, final above- ground biomass was positively affected by warming and increased [CO2], increasing 60 and 115% for the suburban and urban sites, respectively, relative to the urban site. These are the first in-situ data indicating how secondary succession in fallow agricultural soil may respond to projected changes in [CO2] and temperature. The large increase in biomass with [CO2] and temperature suggests that the rate of succession might be increased in a future, warmer, higher [CO2] environment.