Transplantation of bryophytes outside the native forest: Bazzania azorica and Lepidozia cupressina

Background/Question/Methods Due to the high air humidity and mild atmospheric temperature, Azorean laurel forests present a particularly important habitat for bryophytes, with high biodiversity and a luxuriant cover of all available substrata, including leaves. Some of their most characteristic bryophytes are not able to survive outside the forests, as is confirmed by their absence from different open habitats on the Azores. However, it is not clear how the stresses resulting from destruction of the forest canopy would limit the growth and fitness of these plants.
Transplantation of bryophytes has mainly been employed in pollution monitoring studies. However this approach may provide interesting information about acclimatization capacity and survival under different kinds of stress and may be particularly valuable to separate genetic from environmental influences upon plants. In this work the transplant technique has been used to investigate the importance of major environmental variables that cause metabolic stresses to bryophytes when the forest cover is removed.
The aims of this study were: (1) to determine whether two bryophytes Bazzania azorica, an Azorean endemic, and Lepidozia cupressina, a wider occurring species, can tolerate conditions outside forests; (2) to investigate the degree of stress imposed on the transplanted liverworts by examining metabolic markers of oxidation and other types of cellular injury. The metabolic markers examined were total lipid content, concentration of lipid peroxides and photosynthetic pigment concentrations.

Results/Conclusions The transplant of the liverworts to positions outside the forest allowed an insight into their behaviour towards high light intensities and simultaneous presence of higher rainfall levels but also higher evaporation stress. Those conditions induced dramatic decreases in the contents of photosynthetic pigments in both species, as well as an increase in the lipid peroxide concentrations in Bazzania azorica, when compared with non transplanted plants.
These variations confirm the ability of bryophytes, even relatively rare ones, to modify their physiological characteristics in response to changing environmental conditions. It became obvious that the presence of Bazzania azorica at medium altitude required compensation factors, usually strong shade and shelter, as was shown by its preferential occupation of soil in shaded forests, and its death outside those conditions.
Although both liverworts may generally be considered shade plants, they differ in many respects such as preferential substrate, relative position in the forest, growth form and physiological behaviour, thus helping to explain their different geographical range. This study emphasizes the importance of dense humid laurel forests for the conservation of bryophytes in the Azores.