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United States Department of Agriculture

Agricultural Research Service

Research Project: ECOLOGY, MANAGEMENT AND ENVIRONMENTAL IMPACT OF WEEDY AND INVASIVE PLANT SPECIES IN A CHANGING CLIMATE

Location: Global Change and Photosynthesis Research Unit

Title: Local conditions, not regional gradients, drive demographic variation of giant ragweed (Ambrosia trifida) and common sunflower (Helianthus annus) across northern US maize belt

Authors
item Wortman, Sam -
item Davis, Adam
item Schutte, Brian -
item Lindquist, John -
item Cardina, John -
item Felix, Joel -
item Sprague, Christy -
item Dille, J Anita -
item Ramirez, Analiza H M -
item Reicks, Graig -
item Clay, Sharon -

Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 27, 2012
Publication Date: August 6, 2012
Citation: Wortman, S.E., Davis, A.S., Schutte, B.J., Lindquist, J.L., Cardina, J., Felix, J., Sprague, C.L., Dille, J., Ramirez, A., Reicks, G., Clay, S.A. 2012. Local conditions, not regional gradients, drive demographic variation of giant ragweed (Ambrosia trifida) and common sunflower (Helianthus annus) across northern US maize belt. Weed Science. 60:440-450.

Interpretive Summary: Knowledge of the environmental and climatic factors influencing the demography of weed species will improve understanding of current and future weed invasions. The objective of this study was to quantify the potential sources of regional-scale variation in the vital rates of giant ragweed (Ambrosia trifida) and common sunflower (Helianthus annuus). To accomplish this objective, a common field experiment was conducted across 17 site-years for giant ragweed, and 15 site-years for common sunflower between 2006 and 2008 throughout the north central US maize production region. Giant ragweed and common sunflower were planted following the soybean phase of maize – soybean rotations, and demographic parameters (winter seed survival, summer seed survival, seedling recruitment, seedling survival to reproductive maturity, and fecundity) were measured in intra- and interspecific competitive environments. Environmental and geographical data (e.g., daily air temperature, precipitation, elevation, latitude, and longitude) were collected within each site-year. Site was the strongest predictor of seed survival and seedling recruitment and survival, indicating the sensitivity of these parameters to abiotic site characteristics such as soil properties and average climate conditions. However, biotic factors also had important effects on plant demography: interplant competition from maize reduced weed fecundity relative to giant ragweed and common sunflower monoculture. When the covariance among vital rates was taken into account using partial least squares regression (PLSR), overall “demographic performance” of giant ragweed and common sunflower was most strongly influenced by thermal time (growing degree days base 2 C, GDD2). The relationship with GDD2 was negative for giant ragweed and positive for common sunflower. The first PLSR components, both characterized by growing degree days, explained 63.2% and 77.0% of the variation in the demographic performance of giant ragweed and common sunflower, respectively; the second PLSR components, both characterized by precipitation, explained 18.3% and 8.5% of the variation, respectively. Demographic performance of both species was negatively related with precipitation. The apparent influence of growing degree days and precipitation is important in understanding and predicting the future distribution and population dynamics of these species in response to climate change.

Technical Abstract: As our climate continues to change, the geographic distribution of agricultural weed species will follow environmental conditions that enable them to thrive in a crop production setting. We set out to quantify the relationship between regional-scale environmental and climatic variables and the population dynamics of two economically important weeds, giant ragweed (Ambrosia trifida) and common sunflower (Helianthus annuus). To accomplish this objective, a common field experiment was conducted across 17 site-years for giant ragweed, and 15 site-years for common sunflower between 2006 and 2008 throughout the north central US maize production region. Giant ragweed and common sunflower were planted following the soybean phase of maize – soybean rotations, and demographic parameters (winter seed survival, summer seed survival, seedling recruitment, seedling survival to reproductive maturity, and fecundity) were measured in intra- and interspecific competitive environments. Environmental and geographical data (e.g., daily air temperature, precipitation, elevation, latitude, and longitude) were collected within each site-year. Site was the strongest predictor of seed survival and seedling recruitment and survival, indicating the sensitivity of these parameters to abiotic site characteristics such as soil properties and average climate conditions. Vital rates of giant ragweed and common sunflower were most strongly influenced by thermal time (growing degree days base 2 C, GDD2). The relationship with GDD2 was negative for giant ragweed and positive for common sunflower. Vital rates of both species were negatively related with precipitation. The apparent influence of growing degree days and precipitation is important in understanding and predicting the future distribution and population dynamics of these species in response to climate change.

Last Modified: 11/28/2014
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