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

Contributions to the Study of Biological Diversity Vol. 3
reflectance in both infrared and red bands.
Burned areas in the pure Avicennia swamp
of the northern portion of the Waini Peninsula
were investigated in more detail with ecological
plots (see Chapter 4). Those swamps suffered
nearly full tree mortality and have undergone
slow early regeneration. Initially, in wet seasons
they were covered with deeper surface water
than neighboring unburned areas, probably
resulting from a combination of decreased
transpiration and lowered elevation from
combustion of the upper organic soil layer.
When surface water was present they were
dominated by floating vegetation, first Lemna
aequinoctialis Welw., which was followed after
the first year by Limnobium laevigatum (Humb.
& Bonpl. ex Willd.) Heine (Figure 1.26). Such
areas that were covered with floating plants were
not distinguishable from forest in band 3 of the
Landsat images, while sparse vegetation and
bare soil were apparent. Areas of open, standing
water were obvious in the near infrared band
(4) due to very low return.
Fig. 1.26 Burned area in the pure Avicennia swamp of the
northern portion of the Waini Peninsula. When surface
water was present they were dominated by floating
vegetation, first Lemna aequinoctialis Welw., followed by
Limnobium laevigatum (Humb. & Bonpl. Ex willd.) Heine.
Later in those areas, shrubby Laguncularia
racemosa (L.) C.F. Gaertn. trees became
established; that species is often considered the
most disturbance adapted of Neotropical
mangrove species (Ball 1980; Elster 2000; Elster
et al. 1999; Roth 1992; Woodroffe 1983), as it
has the smallest, and so presumably most easily
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dispersed, propagules.
In areas that were not apparent as obviously
burned in the FCC image but were actually
recovering from fires, most were lightly to
moderately covered with herbaceous vegetation
including vines, Typha, and Acrostichum, which
reflected adequate near-IR (band 4) to make
them difficult to distinguish from undisturbed
vegetation. Most of those areas were also
slightly elevated and not covered with standing
water or with highly saturated soils that
contribute to low return in the near-IR.
The Kamwatta burn was the subject of
limited field work, as it was not initially
discerned in the Landsat FCC, perhaps due to
limited areas of standing water, and confusion
with adjacent areas of clouds and cloud shadows
in the far southeastern part of the view.
Nonetheless, manual delineation of the
Kamwatta burn using separate bands 3 and 4
was practicable and consistent with preliminary
field investigations in the area. In the future it
would be useful to conduct additional field
investigations in that area south of Kamwatta
Beach to determine if fires had occurred there.
Plant Collections of Interest
Some plant collections made during field
work were of particular interest because they
represented new information on the ranges of
species. In the first section, collections from the
Waini Peninsula are covered, followed by
collections made elsewhere in the Northwest
District.
- On the Waini Peninsula:
Rhizoclonium africanum Kützing,
Cladophoraceae, det. J. Norris, 2000: Hollowell,
Arjoon and Chin 255, collected 4 November
1998. This algal species is newly recorded for
the Guianas. It is known from mangrove swamps
in Brazil, Central America, the Caribbean, and
the west coast of Africa. Through introduction
it is nearly pantropical in mangrove swamps
(Guiry & Nic Dhonncha 2004). The collection
was made just behind the beach ridge
approximately 4 kilometers southeast of Waini
Point. Rhizoclonium was collected on
pneumatophores of Avicennia trees, and was
very common in the wetter parts of the Coastal
Mangrove swamps near the beach ridges.