Abstract Detail

Ecological Section

Schafer, Jennifer L. [1], Hohmann, Matthew G. [2], Hoffmann, William A. [1].

Effects of fire on nitrogen use efficiency of deciduous and evergreen shrubs.

In fire-prone ecosystems, the mechanism plants use to maximize nitrogen use efficiency (NUE) may mediate the effects of fire on competitive ability. Evergreen plants are believed to be competitive in low-N ecosystems primarily because long leaf lifespan promotes N conservation, resulting in high NUE. We hypothesized that this N-conserving strategy is thwarted by frequent burning due to increased tissue turnover, thereby reducing the advantage of evergreen leaves. We tested this hypothesis under replicated prescribed fires, conducted at 3-year intervals, by quantifying NUE at different times after fire at our Fort Bragg, NC study site. We measured NUE of two deciduous (Clethra alnifolia and Gaylussacia frondosa) and two evergreen (Ilex glabra and Lyonia lucida) shrub species that occur in the ecotone between upland longleaf pine savannas and wetlands. We calculated NUE as the ratio of the biomass lost to leaf senescence and fire to the N lost to leaf senescence and fire. As expected, evergreen species had higher NUE than deciduous species under unburned conditions, but this difference was greatly reduced under frequent burning. Ilex glabra maximized NUE via high N resorption, whereas Lyonia lucida maximized NUE via a long leaf lifespan. Our study suggests that maintaining the current 3-year fire return interval may promote co-existence of deciduous and evergreen shrubs. An increase in fire frequency, however, may reduce the competitive ability of evergreen shrubs by preventing N resorption and reducing leaf lifespan, and thus, reducing their NUE.

1 - North Carolina State University, Plant and Microbial Biology, 2115 Gardner Hall, Box 7612, Raleigh, NC, 27695, USA
2 - US Army Corps of Engineers, Engineer Research and Development Center, PO Box 9005, Champaign, IL, 61826, USA

Keywords:
Nutrient Use Efficiency
Prescribed Fire
Longleaf Pine Savanna
Leaf lifespan
Nitrogen resorption.

Presentation Type: Oral Paper:Papers for Sections
Session: 24
Location: Clearwater/Grove
Date: Tuesday, July 29th, 2014
Time: 11:30 AM
Number: 24006
Abstract ID:294
Candidate for Awards:None