Abstract Detail

Ecology

Richardson, Lea [1], Wagenius, Stuart [2].

Fire influences flowering phenology and reproduction in two tallgrass prairie forbs.

Flowering phenology is well-linked to climate, but much less is known about how disturbances, such as fire, influence flowering phenology. Fire is a common disturbance that promotes native species diversity in tallgrass prairie ecosystems. Although increases in flowering have been observed for many native plant species following fire, little is known about the magnitude of phenological change following fire or resulting reproductive outcomes for plant species. To investigate the relationship between fire, flowering, and reproduction, I studied two common prairie forbs, Solidago speciosa and Liatris aspera. I randomly selected approximately 90 individuals of each species to monitor along a transect in a prairie preserve that is divided in half and burned every other year. I measured flowering phenology, flowering effort, spatial location, and seedset over two years. During the first year, half of the plants were in the burned half of the prairie preserve, and during the second year neither side burned. I hypothesize that fire synchronizes flowering phenology among individuals, which in turn influences seedset. To understand the impacts of phenology and fire on reproductive success, I generated maximum generalized linear models with seedset as the response and used backwards elimination to select the best model for each species.
In the year with burning (2016), both species’ total reproductive output was higher in the burned unit compared with the unburned unit. Flowering density of conspecifics in the burned unit was double for Solidago, and more than twenty times higher for Liatris. In the year with no burn (2017), the flowering density of both species differed between the sides of the preserve, but the difference was less extreme than during the burn year. These results suggest fire stimulates flowering in Liatris and Solidago. In both years and for both species, seedset was best modeled as a function of burn unit interacting with individual flowering synchrony. Flowering synchronously with the population is associated with higher seedset when flowering density is low, such as on the unburned side of the preserve. However, increased flowering synchrony is associated with lower seedset when flowering density is very high. At low densities, plants may benefit from flowering synchronously with the population because plants that are extremely isolated are less likely to receive pollen. In very dense patches of flowering plants, however, high synchrony could be a disadvantage because of high intraspecific or interspecific competition for pollination.

1 - Northwestern University/Chicago Botanic Garden, Plant Biology and Conservation, 777 Hinman #37, Evanston, IL, 60202, United States
2 - Chicago Botanic Garden, CONS SCI DEPT, 1000 Lake Cook Road, Glencoe, IL, 60022, United States

Keywords:
phenology
fire
plant reproduction.

Presentation Type: Oral Paper
Session: 2, Ecology Section - Functional Traits and Responses
Location: 104/Mayo Civic Center
Date: Monday, July 23rd, 2018
Time: 9:00 AM
Number: 2005
Abstract ID:322
Candidate for Awards:Ecological Section Best Graduate Student Paper