Journal of the Royal Society of Western Australia, 86(1), March 2003 
Figure 4. Avicennia marina margin with salt flat at Lake 
MacLeod, showing scattered stunted trees. Also shown is the 
variability in pneumatophore height at Site 3. 
with occasional very stunted mangrove shrubs (Fig 4). 
Samphires ( Halosarcia sp) occur in both zones. The sharp 
demarcation between the two zones would be controlled 
by micro-elevation, and the relatively stable water levels 
of the ponds. 
At site 3 (Goat Bay), mangroves of the zone 2 salt flat 
margin type had unusual variability in pneumatophore 
height ( ca 5-60 cm; Fig 4). This could be due to periods of 
stationary higher water levels, when the lake floods. In 
places (i.e. adjacent to Plot 1C), Halosarcia grows in dense 
mats over the top of Avicennia pneumatophores. 
Community structure and biomass 
Site descriptions (Table 1) indicate the variable 
characteristics of these mangrove communities. Biomass 
of each 100 m 2 plot at Lake MacLeod, using the 1999 stem 
diameter data and allometric determinations of Clough et 
al. (1997) are given in Table 2. 
Site 1 is a taller promontory of older trees, with 
branches densely overhanging the water. There are no 
seedlings under the dense canopy. Plot 1C is adjacent to 
a patch where mangrove trees have recently died. Here 
Halosarcia samphires are densely growing over the 
Avicennia pneumatophores. 
Site 2 mangroves occur on a low island central in the 
pond, where inundation occurs during strong southerly 
winds. The mangrove margin is narrow, and landward 
of this (inside the island) is unvegetated salt/mud flats. 
The exposed nature of site 2 is reflected by the lower 
heights of trees (Table 1). There is evidence of bank 
erosion, with horizontal Avicennia roots draping over the 
Table 2 
Above ground biomass and foliage cover of mangroves at each 
plot. 
Site/ Plot 
Biomass 
(kg 100 m' 2 ) 
Crown Cover 
% 
Foliage cover 
% 
1A 
1186.9 
100 
70 
IB 
1221.8 
85 
51-68 
1C 
1849.1 
95 
66.5 
2A 
1906.1 
90 
27 
2B 
927.3 
90 
45 
2C 
1004.6 
90 
36 
3A 
2548.8 
100 
80 
3B 
1039.2 
100 
70 
3C 
1215.9 
60 
42 
Mean 
1212.6 
90 
55 
edge of the bank into open water (Fig 3). Some eroded 
sediment has been re-deposited among the mangroves 
within the plots. 
At Goat Bay (Site 3), mangroves vary between a 
narrow margin at plot 3A, to up to a 50 m margin at plot 
3C. Plot 3A is largely one multi-stemmed tree, with 
heavy shading and no samphire growth. Plot 3C has a 
large amount of dead timber, which pre-dates the 
monitoring period. 
Crown cover 
Crown cover values (Table 2) are high, showing that 
while the mangrove margins are narrow the trees have 
dense growth. However, foliage cover is particularly low 
at the island site 2, to give an overall mean of 55%. 
Seasonal production and phenology 
Averaged production in dry weight g m' 2 d' 1 from each 
site is shown in Figs 5-7, and the total annual production 
of litter from the Lake MacLeod sites is given in Table 1. 
Discussion 
Comparing the seasonal productivity and phenology 
data (Figs 5-7), all sites showed minimum productivity 
during the winter period of June to September and 
maximum production during the spring period of 
August to December. The exception is the high 
productivity at Site 1 during late summer (March to 
June). This was caused by heavy fruiting as opposed to 
leaf production. Phenological patterns are very similar 
Table 1 
Stand structure data and annual litter production for mangrove monitoring sites at Lake MacLeod. 
Site 
Tree density 
m* 2 
Tree height (m) 
December 1997 
Tree height (m) 
February 1999 
1997-1999 Mortality 
% 
Annual production 
(g dry wt m’ 2 ) 
1 
0.57 
3.85 
4.05 
2.5 
1077 
2 
0.31 
2.47 
2.46 
0 
659 
3 
0.50 
2.94 
3.10 
4.0 
829 
Mean 
0.46 
3.09 
3.20 
2.1 
855 
28 
