Preliminary Floristic Inventory of the Bilsa Biological Station, Esmeraldas, Ecuador
John Littner Clark
US Peace Corps - Fundacion Jatun Sacha - National Herbarium of Ecuador
Abstract
Extensive logging and colonizing since the 1960s have cleared all but 0.8% of the wet forest category in the coastal region of Ecuador, encompassing tropical wet forest and premontane wet forest. In the July of 1994, the Jatun Sacha Foundation purchased 760 hectares ranging from 400 to 600 meters altitude in the last continuous tract of these forests and established the Bilsa Biological Station, located in the Mache Mountains of northwestern coastal Ecuador. Since September 1994 until October 1995 a team of four botanists have made over 2,500 collections. Thus far new species discovered include: 6 epiphytes, 3 herbs, 5 understory trees, 4 subcanopy trees and 2 canopy trees.Introduction
The coastal forests of Ecuador are considered some of the most severely threatened ecosystems on earth (Meyers, 1987,1988; Gentry, 1989; Simerloff, 1986; Dodson & Gentry, 1991). The tropical wet and moist forests of coastal Ecuador once spanned a continuous band from Colombia to Peru reaching up to 20km wide near the northern exent and becoming very narrow and broken in the South. Extensive logging and colonizing since the 1960s have cleared all but 0.8% of the wet forest category, encompasing tropical wet forest and premontane wet forest (Dodson & Gentry, 1991). In order to protect one of the last continuous tracts of these forests, the Jatun Sacha Foundation purchased 760 hectares in July of 1994 to establish what is now known as the Bilsa Biological Station. This step made it possible to begin investigation of what is left of this poorly understood area. The focal point of research thus far has been a botanical survey.Ten years ago, Gentry(1982,1986) wrote that the tropical wet forests of coastal Ecuador constituted the southermost extension of the Choco, therefore the farthest extent of the Central American flora reaching into South America. This was accepted until Gentry(1992) conducted studies based on a series of transects (plants > 2.5 cm dbh. in 0.1 ha.) in western Ecuadorian forests. He found that these coastal sites and the Andean foothills were similar enough to suggest that they may have originally constituted part of the same uninterrupted block of forest, and that they are unique and distinct from the Choco flora.
The collections made thus far from the Bilsa Biological Station are some of the first for the Mache Mountain Range and only the beginning of botanical exploration for the area. It is too early to make definitive conclusions about the relationship of the Bilsa Biological Station's flora to other well known areas such as Rio Palenque Science Center and Centinela because most of the collections have not yet been seen by specialists.
Study Area
The Bilsa Biological Station is located in the Mache Mountains of northwestern Ecuador in the southernmost part of the province of Esmeraldas (00°21'N 79°44'W). The Pacific Ocean is 29km due west and the equator is 36km south. It is an important watershed for the Dogola and Cube Rivers that drain into the Quinindé and Esmeraldas Rivers. The current size of the reserve is 760 hectares, but additional land purchases are being made to the south and west along the headwaters of the Dogola River. The area is mountainous with steep slopes and ranges in elevation from 400 to 600 meters.There is a pronounced wet season between December and June that restricts interior access to foot, horse or mule. After the end of the rainy season it may take three months for the logging road to dry and be cleared for motorized vehicle access. The reserve is constantly covered in mist and fog created by the orographic uplift from ocean currents, from which it derives its local name, El Paramo. The annual precipitation is probably between 2,500 and 4,000mm, but because mist and fog are not measured, no accurate data exist. The average temperature is between 23 and 25.5°C.
The Bioclimatic Map of Ecuador (Canadas, 1983) places the Mache-Chindul Mountains in the categories of tropical and premontane wet forest. However, the forests at the Bilsa Biological Station have characteristics of both lowland tropical wet, premontane wet, and highland cloud forests. For example, many genera that are typical of cloud forests, such as Panopsis (Proteaceae), Bacconia (Papaveraceae), Meliosma (Sabiaceae), and Saurauia (Actinidiaceae), are found at the Bilsa Niological Station. The abundance of epiphytes, lichens, and mosses that characterize cloud forests are also prominent in the station property.
Results and Discussion
Since September 1994 over 2,500 collections have been made, which is only a start on the amount of collecting needed for a comprehensive inventory. The Rio Palenque Science Center, a tropical wet forest 110kn south of Bilsa, between Quevedo and Santa Domingo de la Colorados (0°30'S; 79°20'W), is the most thoroughly studied site in coastal Ecuador and required 223 person-days to complete the florula of the 100 hectare forest. In contrast, at the Bilsa Biological Station only 182 person-days have been devoted to a reserve which is over seven times larger.To date, the most speciose groups with the approximate number collected in each so far have been the ferns and their allies (>110), Rubiaceae (>46), Orchidaceae (>44), Araceae (>35), and Gesneriaceae (?).
Although there is an absence of any quantitative data, plant distributions in the mature forest at Bilsa appear to be markedly clumped, or patchy. Few of the most common species are found consistently throughout the reserve. More frequently, they are only locally common or dominant in some areas, and rare or absent in subjectively similar sites elsewhere. In this respect, the reserve may differ from the Cabeceras de Bilsa Rapid Assessment Program site located 25 km north and 200m lower in elevation, where Foster (1992b) noted that
the year-round moisture tends to eliminate the formation of separate communities on ridgetops, slopes, and ravine bottoms.
While such separate communities are not readily apparent at Bilsa, neither is the relative uniformity of vegetation reported from Cabeceras de Bilsa
The common herbs of the mature forest are Gasteranthus crispus (Gesneriaceae), Dicranopygium sp. (Cyclanthaceae), and Cyclanthus bipartitus (Cyclanthaceae). Frequent understory epiphytes and climbers are Begonia glabra (Begonaceae), Tillandsia cornuta (Bromeliaceae), Philodendron verrucosum (Araceae), and Anthurum sp. (Araceae).
Common mature forest shrubs include Chrysochlamys sp. (Clusiaceae), Faramea quinqueflora (Rubiaceae), Eschweilera rimbachii (Lecythidaceae), Henriettella sp. (Melastomataceae), and Miconia sp. (Melastomataceae). Frequently encountered trees of the under- and mid-story are Licania celiae (Chrysobalanacaea), Hippotis sp. (Rubiaceae), Coccoloba sp. (Polygonacaea), Salacia juruana (Hippocrateaceae), Eschweilera caudiculata (Lecythidaceae), and Grias sp. nov. (Lecythidaceae).
The two most common canopy trees are Carapa guianensis (Meliaceae) and Otoba gordoniaefolia (Myristicaceae). The dominance of Carapa guianensis at the Bilsa Biological Station is similar to the Rapid Assessment Programme's Cerro Pata de Pajaro site (25km south), where it sometimes accounted for 95% of the canopy (Foster, 1992a). Other canopy trees include Dacryodes sp. (Burseraceae), Pterocarpus sp. (Fabaceae), Virola dixonii (Myristicaceae), Pouteria sp. (Sapotaceae), Iriartea deltoidea (Arecaceae) and Socratea exorrhiza (Arecaceae). The most common canopy epiphytes are Sphyrospermum buxifolium (Ericaceae), Elaphoglossum sp. (Pteridophyta) and Pleurothallis sp. (Orchidaceae).
Plants common along streams include Cuphea tetrapetala (Lythreaceae), Dicranopygium sp. (Cyclanthaceae), Bolbitis pandurifolia (Pteridophyta), and Podandrogyne brevipedunculata (Capparidaceae).
Historically, the coastal region of Ecuador has been neglected botanically. There are few collections from the tropical wet and moist forests of coastal Ecuador, and the collections from Bilsa are some of the first ever made in that area. Identification of the specimens is made more difficult by the lack of coastal collections in the National Herbarium of Ecuador. The collectors and other botanists working in Ecuador have made some determinations, but it will take a few years before most of the specimens are identified. Nevertheless, 15 new species have been discovered.
An undescribed canopy tree species, Chlorocardium (Lauraceae) was locally common on a lot southwest of the reserve. This genus was recently described by Werff(1991), but it is still poorly known. When Werff described the genus, there was so little reproductive material available, he had to base his description on wood structure because most of the flower buds available for dissection had suffered fungal attack (Werff 1991). The two species described in this genus are found in Amazonia and only one, Chlorocardium venenosum, reaches Ecuador near the Colombian border. Although this canopy tree was only recently discovered by botanists, it has been sought by loggers for years because of its fine yellow wood.
A new species of Bauhinia with large white caulescent flowers is a common understory tree. A similar Bauhinia with red flowers was found in the Cerro Pata de Pajaro site from the Rapid Assessment Program. Foster (1992b) wrote that other species of Bauhinia with these characteristics are known only from Africa.
Other new species include: two sub-canopy trees in the genus Dussia (Fabaceae); a canopy tree, Citharexylum (Verbenaceae); an understory tree, Cinnamomum (Lauraceae); a canopy tree, Pleurothyrium (Lauraceae); an understory tree, Panopsis (Proteaceae); an understory tree, Grias (Lecythidaceae); and many new species of Anthurium and Philodendron (Araceae).
In contrast to the tropical wet and moist forests of Amazonia, the coastal forests are relatively low in tree species diversity (Gentry, 1986). This is especially apparent at Bilsa in the hilly area. However, the flat areas vary in diversity and dominance of species. For example, in the SE section of the property, where the land is least hilly, the alpha diversity is higher than any other area of the reserve (Palacios, 1995). Unfortunately, the Bilsa reserve has only a small portion of this type of Terrain. Luckily, there are still several large intact areas outside of the reserve that are being purchased and that represent these areas of high alpha diversity.
Conclusions
The last year (1994) saw major deforestation, including all the forest on the northwest border of the small Jatun Sacha Bilsa Biological Station. In the next two to five years, the station will likely be an island surrounded by pasture. The logging company ENDESA Setrafor is attempting to log the area on a sustainable basis, but this is not realistic due to the rapid colonization after the logging roads are constructed. The reputation of the area as having cheap land and opportunity is growing and sometimes groups of up to twenty people come to colonize new communities. In the town closest to the Station, Santa Isabel, the number of its stores increased from one to five in less than a year.The overall floristic diversity of the Bilsa Biological Station and surrounding forests will not be known until more thorough inventories are compiled. From the collections to date, it is clear that the forests at the Bilsa Station are different from those at Rio Palenque. There is not yet enough information available to conclude that the forests at the Bilsa Station are a separate phytobiogeographic entity, but in order to further understand this forest and its relationship to others, it must be preserved.
Acknowledgements
This study was made possible through the collections and volunteer help from Richard Abbott, Barbara Adnepos, Margaret Bass, Lara Kueppers, Nigel Pitman, Yvonne Troya, and Clare Watt. I am grateful to the National Herbarium of Ecuador for providing use of their facilities. Special thanks are due to Patti Anderson, Heather Lintz, Lars Kvist, Abigail Rome, and Laurence E. Skog for comments on the manuscript.Literature Cited
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