Gibson, Keighery & Lane: Lake Muir-Unicup wetland system 
the fourth from a seasonally inundated claypan. 
The two quadrats from species-poor Baumea articulata 
wetlands (Yarnup and Unicup) had a major collapse of 
the dominant species (the cover abundance scores of B. 
articulata changed from 30-70% to 2-10%). The Yarnup 
quadrat was immediately adjacent to the depth gauge 
while the Unicup quadrat was 100 m to the north of the 
depth gauge. 
Water depth and pH of Yarnup Swamp were 
markedly lower in 2001 than in previous years and pH 
remained low in 2002 even after the return to more 
normal water depths (Fig. 3a). Similarly Yamup's salinity 
was markedly higher in 2001 than in previous years and 
was also higher than usual in 2002 despite an increase in 
water depth. This wetland has a long term (1980-2002) 
trend of increasing salinity (JAK Lane, unpublished 
data). There was a marked decline in water depth - and 
increase in salinity - of Lake Unicup in 2001 and 2002 
(Fig. 3b), however lake water pH did not change 
significantly. 
The third site to show marked change over the 
monitoring period was a Melaleuca swamp in Kodjinup 
Nature Reserve. Here in 1997 the understorey was 
dominated by Lepidosperma longitudinale (30-70% cover) 
and Baumea articulata (10-30% cover) but by 2002 the B. 
articulata had almost disappeared. Only this single 
species showed a change in abundance at this quadrat. It 
is unclear whether this change represents gradual 
compositional shift of the swamp or an abrupt change of 
state since no water depth or water chemistry data are 
available. 
The final quadrat that showed large movement in the 
ordination scores between 1997 and 2002 was on a 
seasonally inundated claypan in Kulunilup Nature 
Reserve. This claypan was dominated by Apodasmia 
ceramophila and these flats are characterized by the 
recruitment of a series of annual taxa as the claypan dries 
(N Gibson, unpublished data). The change noted at this 
quadrat is likely to have resulted from the claypan being 
sampled at different drying and floristic stages in 
October 2002 compared with October 1997. It does not 
represent habitat deterioration. 
Discussion 
The results of this monitoring are initially encouraging 
in relation to the maintenance of the biodiversity values 
of the wetlands in the Lake Muir-Unicup catchment. 
Only four of the 27 wetlands sampled showed obvious 
change over the study period. Two of these wetlands are 
known to have undergone significant changes in water 
quantity and / or quality during the period of 
monitoring. However, the lag period between land 
clearance and impact, and between restoration of 
perennial cover and improvement in ground water 
quality and depth, are known to be significant, perhaps 
being in the order of decades (National Land and Water 
Resources Audit 2001). Hence, results from any single 
monitoring interval need to be interpreted carefully. 
More worrying in relation to the Lake Muir-Unicup 
catchment was the appearance of new saline springs both 
high and low in the landscape over the period 1997 - 
2002 which were not related to surface drainage nor 
known hydrological source areas (R. Hearn, 2002, CALM, 
personal communication). These springs have appeared 
in upland areas in Unicup Nature Reserve, and in low 
lying areas of Kulunilup and Bokarup Nature Reserves 
but are not associated with the basin wetlands of these 
reserves. 
The appearance of these springs suggests that current 
ground water levels are not yet in equilibrium and that 
the hydrological system is complex given that saline 
influences are not initially seen in basin wetlands where 
ground water intersection may have been first expected. 
Detailed hydrological investigations are presently 
underway to identify recharge and discharge areas which 
will allow effective ground water management strategies 
to be developed (R. Hearn, 2003, CALM, personal 
communication). The three affected wetlands urgently 
need ground water management programs. 
Acknowledgements: Bill Muir, Grant Pearson and Kate Brown assisted 
in the fieldwork, CALM regional staff, particularly Roger Heam and Ian 
Wilson, assisted with the logistics and material for the project. 
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