Durham E-Theses The Physiological Response of sub-Arctic Lichens to Their Abiotic Environment HENRI, DOMINIC,CHARLES How to cite: HENRI, DOMINIC,CHARLES (2011) The Physiological Response of sub-Arctic Lichens to Their Abiotic Environment , Durham theses, Durham University. Available at Durham E-Theses Online: http://etheses.dur.ac.uk/623/ Use policy The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that: • a full bibliographic reference is made to the original source • a link is made to the metadata record in Durham E-Theses • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders. Please consult the full Durham E-Theses policy for further details. Academic Support Oce, Durham University, University Oce, Old Elvet, Durham DH1 3HP e-mail: [email protected] Tel: +44 0191 334 6107 http://etheses.dur.ac.uk 2 The Physiological Response of sub-Arctic Lichens to Their Abiotic Environment Abstract The effect of environmental factors on metabolic processes of sample thalli, of four sub-Arctic lichen species from Abisko, Sweden (68.37˚N, 18.69˚E). Nephroma arcticum , Cladina mitis , C. stellaris and C. rangiferina , which are found in contrasting niche habitats within the same ecosystem, have been studied. An oxygen electrode apparatus has been used to study the effects of air temperature, thallus irradiance intensity and climatic regime during thallus storage, on the rate of net photosynthesis and dark respiration of sample thalli, in a series of studies on the four lichen species named above. Environmental temperature and light intensity both significantly affected the rate of thallus net photosynthesis (NP) in samples of all four species. The mean rate of thallus NP was significantly depressed at 17⁰C in all four species due to an exponential increase in respiratory rate with rising temperature. Maximal NP was achieved at 5⁰C in N. arcticum , 10⁰C in C. rangiferina , and NP at 5 & 10⁰C were not significantly different in C. mitis and C. stellaris . Optimum light intensity for photosynthesis was 340 µmol m -2 s-1 in all four species; however, temperature significantly increased the light compensation point of photosynthesis. Furthermore, mean light compensation points were greater in the more shaded adapted species N. arcticum and C. mitis ; suggesting, as found in vascular plants, lichens exhibit photosynthetic characteristics adapted to their abiotic environment. C. mitis thalli did not provide any evidence of plastic adaptation to temperature over a six day storage period; whereas, N. arcticum samples exhibited increased NP after six days at 10 & 15⁰C compared to non- acclimatized samples. Prolonged storage at 10⁰C appeared to be detrimental to samples of C. stellaris . Responses to temperature and light intensity were similar to those found, in similar species, in photosynthetic rate investigations utilizing IRGA apparatus; validating the use of O 2 electrode experiments using small samples of thallus tissue, as used in this investigation. The response of species, within this study, to environmental factors was slightly different to those obtained in similar studies for North American populations, which suggests that lichens may exhibit some within-species genetic variation between lichen populations from different continents. Analysis of moisture availability, from past climate-data of the region from which the lichen populations are found, suggests that the growth season of sub-Arctic lichens is very different to that of vascular plants that are within the same ecosystem. Future warming may cause longer, wetter Arctic Autumns and Springs, which would benefit lichen biomass, but environmental warming would suppress lichen growth and promote vascular plant productivity. i The Physiological Response of sub-Arctic Lichens to Their Abiotic Environment A report of investigations undertaken to study the effect of the external environment, on photosynthesis and respiration in lichen species, which are common in tundra-heath ecosystems from Abisko, Sweden. Dominic Charles Henri Supervisors: Dr. Robert Baxter and Prof. Brian Huntley Durham University, Department of Biological and Biomedical Sciences Thesis for the degree of MSc Biology by research October 2010. ii Table of Contents 1. Introduction ............................................................................................................................... Page 1 1.1. What are lichens? ..................................................................................................................................................... 1 1.1.1. Definitions .......................................................................................................................................................... 2 1.1.2. The physiology of lichens ............................................................................................................................ 3 1.1.3. The importance of lichens in Arctic regions ...................................................................................... 4 1.1.4. The economic importance of lichens ..................................................................................................... 5 1.1.5. The ecological importance of the loss of lichen species ................................................................ 5 1.2. Ecological significance of temperature for lichen species .................................................................. 7 1.2.1. Evidence for the effect of temperature on the growth of lichens ............................................. 7 1.2.2. How does temperature affect lichen growth? ................................................................................... 8 1.2.3. The effect of temperature on lichen productivity and growth ............................................... 12 1.2.4. Lichens and extreme temperatures .................................................................................................... 13 1.3. Thallus hydration and growth ........................................................................................................................ 15 1.3.1. The interaction between thallus hydration and metabolic activity ...............................16 1.3.2. Climatic factors that affect thallus hydration ............................................................................... 19 1.4. Effect of light related external environment factors on lichen productivity .......................... 23 1.4.1. Photosynthesis and light .......................................................................................................................... 23 1.4.2. Light stress ..................................................................................................................................................... 25 1.5. Within species variation of the net photosynthetic rate of lichens due to environmental factors .......................................................................................................................................................................... 27 1.5.1. Measuring the significance of seasonal fluctuation of NP to the contribution of lichens, to net ecosystem productivity ................................................................................................................. 27 1.5.2. Acclimation .................................................................................................................................................... 28 1.6. Ecological response of lichens to climate change ................................................................................. 32 1.6.1. Evidence of past climate change affecting lichen ecology ....................................................... 32 1.6.2. Future climate change .............................................................................................................................. 34 1.6.3. Non-climate related factors affecting the ecology of sub-Arctic lichens ........................... 37 1.7. Aims of the present study ................................................................................................................................. 39 1.8. Dissertation outline .............................................................................................................................................. 41 2. Samples ............................................................................................................................................... 42 2.1. Lichen species ecology ....................................................................................................................................... 42 2.2. Storage ........................................................................................................................................................................ 45 2.3. Creating samples from lichen thalli ............................................................................................................. 48 3. Methodological development ....................................................................................................... 49 iii 3.1. The importance of metabolic rate data as an ecological tool ......................................................... 49 3.2. Measurement of the metabolic