Brad Congdon (Project Coordinator)
BZ1005 - Introductory Ecology (Subject)
21 August 2013
Ecological Patterns and Processes in Mangrove Ecosystem
Location: The Jack Barnes Bicentennial Mangrove Boardwalk, Cairns Qld
Part 1 - Field Notes
Stage 1 (13:50) 15m from the entrance of the boardwalk, 86cm between boardwalk and soil. At this stage the board walk is surrounded by a wide open area that has no tall trees for as far as 20m and over 50m in some directions. This area is completely exposed to sunlight probably most of the day, it doesn’t seem to receive water from the tides or from the rain very regularly, the soil at the moment is extremely dry and cracked at the surface where small wholes can be seen approximately 2-3cm in diameter, possibly made by small crabs, the vegetation in this area consist of few different species of grass, herbs and small shrubs which must be the most tolerant plants to inhabit these conditions (dry and high salinity). Two species of grass/herb can be noticed in this area: Specie a – predominant, high 20-30cm, is composed of several branches coming out from its stalk filled up with lots of light green cylindrical shape thick leaves; Specie b - is less numerous high 20-30cm it has few branches and no leaves, the branch is light green seen to be made of a juicy material and is composed of small segments that become shorter towards the end. There are also at least 2 species of shrubs: Specie c – high 0.4-1.7m has no above soil roots, smooth white grey bark, pointy light green leaves that are grey on the backside; Specie d – High 0.4 to1.2m, oval yellow green leaves with glossy smooth surface grouped at the end of the braches all pointing up.
Stage 2 (14:05) 50m from starting point, 90 cm between boardwalk and soil: At this part of the board walk the soil has not completely dried, it has more moisture than the previous part, it is presumed that it receives tidal waters before and keeps its moisture for longer due to the lower elevation and its proximity to the water channels, the higher humidity could also be assisted by the shading produced by dense, same sized tree vegetation surrounding the area that provides a good shelter from sunlight. The number of holes in the soil is also many times greater than previously seen, what may indicate a higher population of crabs, shrimps and other species that may inhabit this area of the mangrove. The vegetation is predominantly composed of one specie which by the similarity of leaves, bark and roots (buttresses) it seems to be the same as one of the species (specie d) registered in the observation 1, however here they have grown more than two times taller (>2.5m) than the samples found in the dryer part of the mangrove, a similar situation is observed in (previously registered) specie c which at this part of the boardwalk reaches approximately 3m in high however in much less density than specie d. One possible reason for this increasing in size is the different soil salinity of the two specific areas, “the part of the soil that receives water more often and keep its moisture for longer is likely to have less saline concentration than the dryer part that is the last to receive the tidal waters and the first to dry”(mentioned by Brad Congdon – Project Coordinator).
Stage 3 (14:20) 80m from starting point (Boardwalk bifurcation), 94cm between boardwalk and soil. A pattern starts to become apparent at this stage as repetitively the decline in the soil elevation, the shorter distance from water channels and reducing in sunlight exposure has provided the soil with a longer lasting moisture which may be associated with the growing capacity of certain plants species. Species (previously registered) D and C at this part have reached heights of approximately 4m and 5m respectively where specie D is still predominant in the area but specie C has a higher density than the one found in stage 2. The number of holes on