What can BRYOMONITOR do?
The main task for BRYOMONITOR is the determination of the degree of disturbance of neotropical rainforests. Depending on the presence of certain indicators (bryophytes) the program assigns a naturalness index to a forest. This index may be used for the comparison of diffferent forests (even of different countries or altitudes). Because of its database functionallity BRYOMONITOR may also be used for long-term studies.
Where can the biomonitoring system be used?
The program has been developed using field data from different areas in Ecuador, Peru, Bolivia and Argentina between 300 and 2000 m in altitude. Therefore, it should be effective for tropical and subtropical humid forests between 0 and 2000 m.
It has been tested in eastern Bolivia in a forest with 1200 mm annual precipitation and a dry season of 3-4 months yielding reasonable results. Therfore, the program may work in such dry areas as well. However, results may be unreliable because such dry forests normally possess a poor bryophyte flora and a very low number of indicators.
The program has not been tested in Central American and Caribbean rainforests to date, but it is expected to work there as well.
It will not be effective for dry forests and in forests significantly above 2000 m altitude. It should not be used for heavily polluted areas as many epiphytic bryophytes are very sensitive to air pollution, and we do not know how the indicators will respond to air pollution.
How the biomonitoring system works
With increasing disturbance, the structure and microclimate of rainforests, especially light, temperature and humidity conditions change significantly. Therefore, species growing exclusively in the tree crowns in undisturbed forest are able to colonize the tree trunks in disturbed and open forests. Species growing exclusively in humid conditions near the trunk base disappear rapidly in disturbed forests. The bryophyte vegetation reacts to changes in forest structure, independent of their origin; thus, the biomonitoring will not discriminate between human and natural disturbance.
The program uses 34 indicator species or species groups, of which 17 are characteristic for primary forests without or with a low degree of disturbance and 17 species or species groups typical for secondary forests and isolated trees. The program calculates a naturalness index of the forest ranging from 10 to 1 based on the presence of these indicators. An index of 10-9 characterises primary forest or forests with a very low degree of disturbance. Typical logged forests show naturalness indices between 7 and 5 and secondary forests have indices between 2 and 4. An index of 1 is characteristic for isolated trees.
Why does the system use bryophytes as indicators?
Bryophytes possess various advantages compared to other species groups:
Bryophytes react quickly to changes in the forest structure
Many species are restricted to certain microclimatic conditions
Many species possess a very wide range of geographical distribution
Bryophytes are a relatively small group of about 4000 species in tropical America
Many bryophytes are taxonomically quite well known
In particular, the wide range of distribution make bryophytes very useful indicators as they can be used in vast parts of neotropical rainforests while most vascular plants can be used only as local indicators.
Another advantage is that only the lower part of the tree trunk has to be studied. The collection of twigs in tree-crowns, often necessary for identification, can be very difficult and time-consuming when tree species are used as indicators.
Disadvantages of bryophytes are their small size and the fact that only few specialists live in South America.
To facilitate the application of the program only species that are easy to identify have been chosen and in many cases whole genera or subgenera are used as indicators. In addition, several genera with only one species in the neotropics are used e.g. Monoclea gottschei, Pseudocryphaea domingensis, Phyllodon truncatulus or Rigodium toxarion.
Several recent floras make the determination of bryophytes much easier today than it was 15 years ago. Useful for determination of the genera of bryophytes is Gradstein et al (2001). For determination of moss-species the floras of Colombia (Churchill & Linares 1995), the lowlands of Ecuador (Churchill 1994), Mexico (Sharp, Crum & Eckel 1994) and of the West Indies (Buck 1998) can be used. A description of Radula voluta can be found in Reiner-Drehwald (1994) and in Schuster (1980).
Buck, W.R. (1998). Pleurocarpous mosses of the West Indies. - Memoirs of the New York Botanical Garden 82: 400 pp.
Gradstein, S.R., Churchill, S. O. & Salazar-Allen, N, (2001). A guide to the bryophytes of tropical America. Memoirs of the New York Botanical Garden 86.
Churchill, S.P. (1994). The mosses of Amazonian Ecuador. - AAU Reports 35: 211 pp.
Churchill, S.P. & E.L. Linares C. (1995). Prodromus bryologiae Novo-Granatensis. – Instituto de ciencias naturales - Museo de historia natural Biblioteca “Jose Jeronimo Triana” No. 12: 924 pp.
Reiner-Drehwald, M.E. (1994). El género Radula Dum. (Radulaceae, Hepaticae) en el Noreste de Argentina. - Tropical Bryology 9: 5-22.
Schuster, R.M. 1980. The Hepaticae and Anthocerotae of North America, vol. IV. Columbia University Press, New York.