Claudine Ah-Peng is a researcher at the UMR PVBMT (Plant Communities and Biological Invaders in Tropical Environments) and is a specialist on bryophytes. She coordinates the Moveclim Project (Mountain vegetation as listening posts for climate change, using mosses and ferns as bioindicators of climate change).
What are bryophytes?
- Bryophytes are non-vascular plants comprising mosses, liverworts and hornworts.These three varieties of plants are the foundation of the tree of life fromwhich all other land plants have evolved. They have played a pivotal role inthe Earth's colonization by plants. There are currently about 20,000 species of bryophytes widely distributed around the world, from the poles to the equator, from sea level to the mountain summits. They occupy a range of microhabitats (soil, trees, living leaves, humus, rocks etc.) and sometimes adapt to inhospitable conditions such as high temperatures and light levels.
What is their role in the ecosystem and how valuable are they as biological indicators of climate change?
- Knowledge of these plants is relatively poor compared to flowering plants, but everyone agrees that bryophytes play a key role, especially in nutrient and water cycles in ecosystems. Bryophytes have no roots, so they absorb water and nutrients directly from the atmosphere, and are very dependent on their environment and sensitive to variations.
Why are bryophytes dubbed the “sentinels” of the environment?
- Cryptogamic plants (lichens and bryophytes) are known to be very sensitive to their environment, and in particular air contaminants. Since the mid-twentieth century, these plants have been used as bio-indicators of air and water pollution. Studies of bio-indication therefore use mosses and lichens as bio-accumulatorsfor contaminants (both metal and organic, and sometimes radionuclides), by measuring the concentrations of these elements in the plant’s tissues. This is called active biomonitoring. For ecosystems where bryological composition and ecological characteristics of the species are known, it is also possible to determine the appearance and/or the disappearance of certain species, which maybe warning signs of environmental disturbance. It is in this case known as passive biomonitoring. The idea is to increase the knowledge of these small plants by studying their taxonomy, ecology and ecophysiology, and to detect the changes in bryological composition, species shift along altitudinal gradients, indicators of ecosystem disturbance. Previous studies have shown that temperature defines the altitudinal distribution of bryophyte species, and the availability of water defines their growth and distribution within these boundaries.
What are their methods of adaptation to climate change ?
- It is clear that the ability of bryophytes to adapt to variations in their environment, such as temperature or relative humidity, depends on the intensity of change and the size of their ecological niche. Also, it seems that the species will tend to migrate upward in mountains to find their optimum environment. Our project therefore seeks to identify current altitudinal species ranges, but also species abundance, growth and reproduction in order to model the distribution of these species in relation to climate change : temperature, relative humidity and rainfall.
Is it true that Moveclim set up the first bryophyte-based comparative analysis of tropical biodiversity at different altitudes ?
- Indeed. The Moveclim project was launched in June 2012 and brings together researchers and actors in environmental management. It provides insight into the taxonomy, diversity and distribution of bryophytes in these ecosystems which are still relatively unknown. Over the last year, transects comprising two 10x10m plots every 200 meters have been set up in Reunion, Pico (Azores), La Palma (Canary Islands), Guadeloupe and Tahiti. Standardized surveys of bryophytes, ferns and vegetation structure were also made, and are being analyzed. Finally, temperature and relative humidity sensors, set up every 200m along three gradients, make regular measurements of climatic variations. The goal is to continue to create records of climatic changes within these plots. The results* and recommendations from this research project could then be used by environmental managers to better protect these delicate island ecosystems.
What is your initial assessment of this project?
- Based on preliminary results from Réunion, two ecosystems appear to be threatened : cloud forests and altimontane systems (subalpine and alpine). If temperature continues to increase, the altitude of temperature inversion that blocks clouds will rise, resulting in changes to ??cloud formations that cover mountain forests each day, and which are dependent on them for water. Similarly, at highaltitude, rising temperatures will increase aridity and thus endanger endemic plant communities. In addition, these summit plant communities, which have no other environments to migrate to, will be threatened with extinction. Therefore, Moveclim also monitors high-risk mountain areas, which began with Hawaii in August 2012, entitled "Vulnerable islands in the sky : management of tropical island alpine and sub-alpine ecosystems".
* Preliminary results for each island should be available in late 2013 and will be presented during a workshop planned for September 2013 in La Réunion, in the presence of Net Biome partners. The workshop will aim to publish the first comparative inter-island analysis of bryophyte gradient distribution.