AOBPreview originally published online on February 14, 2005
Annals of Botany 2005 95(5):869-877; doi:10.1093/aob/mci093
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Photosynthetic Responses of Plant Communities to Sand Burial on the Machair Dune Systems of the Outer Hebrides, Scotland
1 School of Geography, University of Plymouth, Drake Circus, Plymouth, Devon, PL4 8AA, UK, 2 School of Biology, University of Plymouth, Drake Circus, Plymouth, Devon, PL4 8AA, UK and 3 Yetta Farm, Mount, Bodmin, Cornwall, PL30 4EZ, UK
* For correspondence. E-mail mkent{at}plymouth.ac.uk
Received: 16 July 2004 Returned for revision: 22 September 2004 Accepted: 5 January 2005 Published electronically: 14 February 2005
• Background and Aims The effects of both short-term (2 weeks) and long-term (6 weeks) burial on the photosynthetic efficiency of four typical plant sub-communities of the machair sand dunes of the Outer Hebrides are described. Previous studies have examined the photosynthetic responses on individual species rather than the response at the community level.
• Methods Three replicate turves from four different sub-community types (foredune grassland, dune slack, three-year fallow and unploughed grassland) were subjected to short- and long-term burial treatments after acclimatisation in an unheated greenhouse for approximately 10 weeks. Three replicate control turves from each sub-community were left unburied. After treatment, photosynthetic rate was measured at 16–20 h and 40–44 h after re-exposure, using an infra-red gas analyser, with standardization by total leaf area for each turf. Effects of sub-community type, burial duration and time since re-exposure were analysed by 3-factor split-plot analysis of variance (ANOVA) with repeated measures for time since re-exposure in the subplots.
• Key Results Buried turves were characterized by a low dark respiration rate, which may represent a maintenance response to burial. After removal of sand, each machair sub-community showed some capacity for an elastic photosynthetic response. There were no differences between the effects of short- and long-term burial on the photosynthetic efficiency of machair vegetation, although turves buried for 6 weeks generally attained photosynthetic rates approaching those of control rates sooner than turves buried for 2 weeks. Photosynthetic responses to burial varied between sub-communities, with the slack turves exhibiting the poorest capacity for recovery within the investigated 44-h period.
• Conclusions In the machair environment, the ability to maintain photosynthetic equipment whilst buried, and the ability to bring about a relatively rapid reinstatement of photosynthetic mechanisms on emergence or exposure, is an important adaptation for survival. Survival is closely related to the ability of a plant to replenish carbohydrate reserves before the next burial event.
Key words: Coastal dunes, dark respiration, elastic responses, infra-red gas analyser, machair, Outer Hebrides, photosynthetic efficiency, plant communities, sand burial, transplant experiments