PARENT SESSION
Poster Session # 7: Restoration, Resource Management, and Conservation.

Monday, August 4 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.

Competitive interactions between the endangered sink-hole species Helenium virginicum and Boltonia asteroides when exposed to variable water depths.

Lassen, Kari^*,1, Hamilton, E William¹, ¹ Washington and Lee University, Lexington, VA

ABSTRACT- Helenium virginicum (Virginia sneezeweed) is an herbaceous plant from the family Asteraceae and is classified as a threatened species federally and as endangered by the state of Virginia. It is found in seasonally flooded sink-hole ponds in 30 sites in Virginia and 1 site in southern Missouri. In sites where Helenium is found Boltonia asteroides (Asteraceae) also occurs in high numbers. To help identify important ecological variables that influence the recovery of Helenium three experiments were conducted. The first was a germination experiment in which it was determined that Helenium germinates when soils are at field capacity but does not germinate when submerged under water due to anoxia. Boltonia germinates under all conditions (e.g. flooding, under a standing water column and at field capacity). The second experiment quantified photosynthetic tolerance of each species when subjected to water logging and submergence. Chlorophyll content, chlorophyll fluorescence (F_v/F_m), and net photosynthesis were used to quantify effects on the light reactions and Calvin cycle, respectively. Helenium had reduced but positive photosynthetic rates when waterlogged and submerged and increased chlorophyll a:b ratios. Boltonia was not photosynthetically tolerant to water logging and submergence and had reduced chlorophyll concentrations. The third experiment was a competition experiment designed to determine potential interactions that determine the distribution of Helenium and Boltonia in sink-hole ponds. Biomass accumulation in Helenium when competing with Boltonia was significantly lower than intra-specific competition biomass and only when plants were submerged could Helenium out-compete Boltonia. These experiments suggest that in order to successfully implement a recovery strategy for Helenium water levels and hydro-periods must be considered and or managed in suitable Helenium habitats.

Key words: Boltonia asteroides, hydro-period, Helenium virginicum, competition