Abstract Detail

Ecophysiology

Neufeld, Howard [1], Perkins, Fern [2].

Host Tree Species is an Important Determinant of Corticolous Lichen Responses to Elevated CO₂ and O₃ after 10 Years Exposure in the ASPEN-FACE.

We surveyed the corticolous lichens on two host trees, paper birch (Betula papyrifera) and trembling aspen (Populus tremuloides) after 10 years of exposure (1998-2007) to elevated CO₂ and O₃ in the ASPEN-FACE experiment in Rhinelander, WI, USA. The experiment utilized chamberless exposure rings, 30 m diameter, with both host trees planted together in one quadrant and to which were allocated four treatments: ambient, elevated CO₂ (eCO₂), elevated O₃ (eO₃), and the combination of eCO₂ + eO₃, each replicated once in each of three blocks. Target daytime exposures (7 am to 7 pm) were 560 ppm CO₂ in the eCO₂ treatment and 1.5x ambient O₃ in the eO₃ treatment. Rings receiving eCO₂ averaged ~530 ppm CO₂ over the course of the experiment, while O₃ concentrations averaged ~37 ppb for ambient and ~49 ppb in the eO₃ rings. Season-long W126 exposure index values ranged from a high of 50.8 in 1999 to a low of 15.1 in 2007. Ozone concentrations and exposures declined linearly over time, probably due to increased canopy deposition and uptake as the host trees got larger. Tree growth and leaf area index were negatively affected by eO₃ and stimulated by eCO₂, resulting in photosynthetically active radiation being highest in the eO₃ rings and lowest in the eCO₂ rings. We assessed lichen richness and areal cover on five host trees per ring in 100 cm² quadrats placed 30-50 cm from the ground on the north-facing side of the host tree trunks. Lichen species richness and cover were higher on birch than on aspen, but those on birch did not respond to the exposure treatments, while those on aspen had their highest values in the eO₃ treatment and lowest in the eCO₂ treatment. Lichen cover on aspen was highly correlated with incident light in the rings. This study demonstrated that these lichens are insensitive to the direct effects of eCO₂, and eO₃ at the levels applied in this experiment, and that indirect effects such as changes in understory light levels, as moderated by host tree responses, and host tree characteristics, may dominant in determining their responses to future climate change.

1 - Appalachian State University, Department of Biology, 572 Rivers St., Boone, NC, 28608
2 - Instituto Monteverde, APDO 69-5655, Monteverde, Puntarenas, Costa Rica

Keywords:
Lichens
climate change
Aspen FACE
Growth
Ozone
carbon dioxide.

Presentation Type: Oral Paper
Session: ECOPH2, Ecophysiology II
Location: Virtual/Virtual
Date: Thursday, July 30th, 2020
Time: 1:15 PM
Number: ECOPH2002
Abstract ID:280
Candidate for Awards:None