Plant Community Structure, Fire Disturbance, and Recovery in ...

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30 Contributions to the Study of Biological Diversity Vol. 3 Although green algae are photosynthetic protists rather than true plants, this is listed because the study of algae is typically grouped within the discipline of botany. Amaranthus australis (A. Gray) J.D. Sauer, Amaranthaceae, det. T. Hollowell, 2001: Hollowell, A. James and Savory 352, collected 12 May 2000. This was apparently the second collection for Guyana; the other known collection was M.S. Grewal and H. Lall 305 (held at Utrecht Herbarium), from the Shell Beach area in 1977. The species is also known in the Guianas from two collections made in French Guiana and two collections made in Surinam (R.A. DeFilipps, pers. comm.). This collection was made to the southeast of Kamwatta Beach (see Figure 1.2), in open water of scrubby mangrove swamp that was possibly affected by a small fire around 1992 (Audley James, pers. comm). Nypa fruticans Wurmb., Arecaceae, det. T. Hollowell, 1997: Hollowell et al. 213, collected 16 June 1997. This was the first known South American voucher for this Asian mangrove palm, collected along the banks of the Mora Passage between the mouth of the Waini River and the Barima River (Figure 1.2). Nypa is a monotypic genus and is unusual among both mangroves and palms because of its dichotomously branching, rhizomatous form (Tomlinson 1986; Tralau 1964); only the fronds and reproductive structures of Nypa extend above the riverbank mud. Nypa is common in Riverine Mangrove swamps along the tidal Waini River, Barima River, and Mora Passage. This species may be spreading in the Northwest District, displacing some native Rhizophora racemosa trees. Nypa fruits have been reported stranded on beaches in Trinidad (Bacon 2001). Plants have been recorded on the Caribbean coast of Panama (Duke 1991), and Nypa has become a widespread exotic species in the Niger Delta (Sunderland & Morakinyo 2002). It has long been utilized in Asia for many purposes, particularly thatching, but it has only rarely been observed in use in Guyana. Roystonea oleracea (Jacq.) O.F. Cook, Arecaceae, det. T. Hollowell, 2002: Hollowell and Hinds 593, collected 21 October 2001. This was apparently the first record of native Roystonea for the Guianas. It was collected in fruit from the isolated population midway across the Waini Peninsula, with an elevation of 5-10 meters above sea level. It was composed of 50- 60 mature trees up to 20 meters high, with a number of juvenile palms present (Figure 1.27). These palms may have been able to survive fires because palm cambium tissues are protected by Fig. 1.27 The first native population of Roystonea oleracea (Jacq.) O.F. Cook found midway across the Waini Peninsula. This isolated population was composed of 50- 60 mature trees up to 20 meter high, with a number of juvenile palms present. their internal position (Cochrane 2003). The species was known from Venezuela including a few localities in Delta Amacuro and Bolívar states, and from Colombia. Some of those populations have been reported as native (Zona 1996). Roystonea oleracea also occurs in coastal swamps of Trinidad and Tobago (Bonadie 1998), and Barbados (Zona 1996), apparently in slightly elevated locations similar to that of the Waini Peninsula population. Species of Roystonea have been cultivated in cities and towns of the Guianas, but the Waini Peninsula population occurred far from any settlement and more than 20 kilometers from Mabaruma, the nearest town with cultivated Roystonea. Ipomoea violacea L., Convolvulaceae, det. T. Hollowell, 2002: Hollowell 217, collected 17 June 1997. This was possibly the second collection in Guyana of the white-flowered, coastal species. Collected along a narrow beach ridge west of Almond Beach. The other known specimen was collected by G.S. Jenman (collection number 5068, at US as Ipomoea macrantha Roem. & Schult.) in 1889 in “coastal
Contributions to the Study of Biological Diversity Vol. 3 lands” of Guyana. It is a widespread coastal vine in the Caribbean and has a nearly pantropical distribution. Sesbania sericea (Willd.) DC., Fabaceae, det. T. Hollowell, 2000: Hollowell, A. James and Savory 351. Collected along a beach ridge swale to the southeast of Kamwatta Beach. The other known collection of this species from Guyana was made by A.S. Hitchcock (collection number 16626) in 1919, with the collection habitat listed as “among weeds” in the Georgetown Botanic Garden. The species is native to Asia, possibly to Sri Lanka (Howard 1976). - In the Northwest District of Guyana: Passiflora amicorum Wurdack, Passifloraceae, det. C. Feuillet, 2000: Hollowell and V. James 383, collected 16 May 2000. Collected on “Kissing Rock” hill north of Mabaruma. This was the first collection of the species for the Guianas; it was previously known only from Bolívar state of Venezuela. This redflowered vine was growing upon low understory vegetation on a steep hillside, in partial shade. Werauhia gigantea (Mart. ex Schult. f.) J.R. Grant. (=Vriesea amazonica (Baker) Mez.), Bromeliaceae, det. E.J. Gouda, 2002: Hollowell, A. James and V. James 386, collected 16 May 2000. This was apparently the second collection of the species in Guyana, the previous record being from Mabura Hill in central Guyana, collected by R. Ek (1997). This specimen was collected from the branches of a Rhizophora racemosa tree overhanging the Aruka River near “Kissing Rock” in the Mabaruma vicinity. Habenaria sp. nov.? Orchidaceae, det. G. Carnevali, 2002. Hollowell and Hinds 607, collected 22 October 2001. This white-flowered, terrestrial orchid was not matched by other Habenaria species (fide Germán Carnevali, CICY) and is awaiting further examination. Collected on terra firme, approximately 100 meters from the Waini River well upriver from tidal influence, near an abandoned sawmill. Miconia minutiflora (Bonpl.) DC. Melastomataceae, det. F. Almeda and D. Penneys, 2002. Hollowell and Hinds 724, collected 4 November 2001. This was the first collection of the species for Guyana. Specimens of this shrub were collected near the Wauna Oil 31 Palm Estate, a small agricultural experimental station that is located about 12 kilometers to the west-southwest of Mabaruma. DISCUSSION These plant collections in Northwest Guyana were carried out as part of ecological research rather than as part of comprehensive plant collection expeditions. Dedicated collection efforts would almost certainly yield additional plant species records for the Waini Peninsula. The number of species records resulting from this fieldwork that were found to be of interest highlights the degree to which the flora of this lowland region has been undersampled. Compared to remote interior areas in Guyana, the coastal plain of the Northwest District can be easily accessed, and additional field work might be relatively inexpensive for the information yielded. As the state of botanical research in Guyana advances, there will be more effort to understand species distributions at the level of a variety of ecosystems and for smaller political units. While existing specimen data can be modeled with GIS to investigate probable species distributions (Funk & Richardson 2002; Funk et al. 2005; Funk et al. 1999), the needs to verify models and produce more accurate and complete input data will always depend upon plant collecting expeditions. A substantial amount of fieldwork, plant identification, and museum work will be required to provide those specimens and data. Changes in the global climate could have significant effects on Guyana’s coastal ecosystems, changing the types of dominant plant communities. Increased severity of El Niño events could lead to higher fire frequencies on the northwest coast of Guyana, particularly if population pressure grows, increasing the chances of ignition. Guyana’s occasional extreme droughts make it vulnerable to incremental forest degradation in which fires can play a key role (Cochrane 2002, 2003). The 1998 fires on the Waini Peninsula had severe impacts on coastal swamp habitats, and effects on forest composition are likely to persist. Fires among the Waini Peninsula mangroves were possibly less anomalous than they initially seem
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138 Guatteria flexilis R.E. Fr. Gua
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144 Aniba hostmanniana (Nees) Mez A
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150 Turneraceae Turnera scabra Mill
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158 Asplundia glandulosa (Gleason)
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162 Psychotria wessels-boeri Steyer
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164 Celastraceae Elaeodendron xyloc
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