Abstract Detail

Ecophysiology

Luong, Justin [1], Loik, Michael [1].

Drought responses of coastal California prairie species during non-native competition.

Environmental filter theory predicts that plants must survive abiotic and biotic challenges in order to successfully establish. Abiotic filters generally require plants to have similar traits for survival, while biotic factors cause trait divergence to facilitate species coexistence. Exploring tradeoffs between traits that mediate abiotic and biotic filtering can uncover physiological mechanisms that may contribute to community assembly. Native California species can withstand drought with minimal impact on productivity but are often sensitive to competition as seedlings. We hypothesized that (1) drought would reduce the biomass of non-native species, and (2) this would result in competitive release and greater growth of California coastal prairie species. In a greenhouse at Santa Cruz, CA, we grew five native species (Bromus carinatus and Stipa pulchra; Diplacus aurantiacus; Lupinus nanus, and Sidalcea malviflora) for six weeks, then seeded five non-native annual species (Carduus pycnocephalus, Festuca bromoides, Geranium dissectum, Medicago polymorpha, and Raphanus sativus) as the competition treatment. We applied an episodic drought on week 8, by withholding water until stomatal conductance was minimized. We quantified above- and belowground biomass, leaf traits (specific leaf area (SLA), major vein length per unit area, lobedness and C:N) and midday leaf photosynthesis. Mid-day photosynthesis for native species was measured weekly through the drought, and during recovery following re-watering. Consistent with our first hypothesis, non-native species had reduced aboveground biomass in response to drought. Carduus pycnocephalus and F. bromoides were able to adjust their root:shoot biomass ratio when competing with certain native species, while other non-natives did not. Drought had minimal effects on the biomass of native coastal prairie plants, but competition led to increased root:shoot biomass for most species. Contrary to predictions from the leaf economic spectrum, SLA increased in response to drought for S. pulchra and L. nanus. Many L. nanus leaf traits were changed by competition and drought. The gas-exchange of L. nanus and D. aurantiacus were negatively affected by drought and competition. Stipa pulchra, B. carinatus and S. malviflora were relatively unaffected by drought and competition. For B. carinatus, competition resulted in a greater rate of photosynthetic recovery following drought, indicating that it may be a suitable restoration species where there is high non-native cover. Tradeoffs between morphology and physiology may help determine which of these native coastal prairie species are able to persist in the face of non-native competition and drought.

1 - University Of California Santa Cruz, Environmental Studies, 1156 High St, Santa Cruz, CA, 95064, United States

Keywords:
drought resilience
gas-exchange
competition
competitive release
functional traits
plant community ecology.

Presentation Type: Oral Paper
Session: ECOPH2, Ecophysiology II
Location: /
Date: Tuesday, July 20th, 2021
Time: 11:45 AM(EDT)
Number: ECOPH2008
Abstract ID:130
Candidate for Awards:Physiological Section Physiological Section Li-COR Prize,Physiological Section Best Paper Presentation