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Harvard Forest Symposium Abstract 2012

• Title: Variation in the vital rates of an allergenic plant, common ragweed (Ambrosia artemisiifolia L.), across an urban to rural and climate gradient
• Primary Author: Jamia Jennings (Mount Holyoke College)
• Additional Authors: Sydne Record (Harvard Forest); Kristina Stinson (University of Massachusetts - Amherst )
• Abstract:

  Ten to twenty percent of Americans suffer from seasonal allergies caused by the pollen of common ragweed (Ambrosia artemisiifolia L.). In a previous study, plant size and flowering responded positively when grown in warmer temperatures and in higher concentrations of carbon dioxide. The goal of our research was to determine if local populations of A. artemisiifolia vary in height and flowering across a rural to urban (cool to warm temperature) gradient in Massachusetts. We measured plants in 24 populations, with 8 populations per temperature group, located along a rural to urban gradient from Boston to the Berkshires in Massachusetts. At each population, 3-5 1m × 1m plots containing 50+ plants were established. The number of flowering plants per plot were recorded weekly and the survival, size, and number of flowers of a subset of 15 tagged individuals were noted biweekly. At the end of the flowering season we harvested the tagged plants from each population to assess the male and female flower production. We analyzed the individual plant growth and reproduction data with nested ANOVAs to determine the effect of temperature, population and plot-level variation, and we analyzed the phenology data with a split plot repeated measures analysis of variance (ANOVA) test.
  
  
  
  
  
  Height and growth varied between the temperature groups. The data demonstrated a trend of taller plants in the urban, warm populations at the beginning (F2,232 = 23.431, P = 8.923 × 10-10) and end of the growing season (F2,232 = 15.889, P =4.624 × 10-7), but the overall plant growth was greatest in the rural, cool populations (F2,232 = 15.30866, P = 7.076 x 10-7). The overall reproductive mass did not vary between the groups (F2,323 = 0.8504, P = 0.429), but the plants in the cooler region produced more female flowers than those in the warm region (F2,323 = 6.821, P = 0.0013) and the plants in the warm region produced more male flowers than those in the cool region (F2,296 = 6.8208, P = 0.00128). Plants in the rural, cool and suburban, medium temperature sites began flowering earlier than those in the urban, warm sites (F2,665 = 3.923, P = 0.023). These findings suggest that the allergy season varies in urban and rural areas and that that people living in warmer, urban areas in Massachusetts may be exposed to more A. artemisiifolia pollen than those who live in the cooler, rural areas in the state.
  
  
  

• Research Category: Invasive Plants, Pests & Pathogens
  Physiological Ecology, Population Dynamics, and Species Interactions
  Conservation and Management