Structural Diversity in Growth Habitat
Growth form varies considerably between species, with mangrove plants characteristically ranging from trees (like Sonneratia caseolaris, Bruguiera gymnorhiza), to shrubs (like Aegiceras corniculatum, Osbornia octodonta), to the trunkless palm (Nypa fruticans), and ground fern (Acrostichum speciosum). Trees and shrubs vary further where they might be columnar and erect (like Bruguiera parviflora), to spreading, sprawling (like Acanthus spp., Scyphiphora hydrophylacea) and multiple-stemmed (like Ceriops decandra). Growth form might also vary within the same species (like Lumnitzera littorea and Rhizophora spp.), having both an erect tree form, and a tangled thicket form. In general, plants on the edges of stands (both water and landward) have more lower limbs and foliage, and their stems are typically sprawling and sinuous, rather than erect and straight. Some species typically form closed canopies with various combinations of species (Avicennia marina, Rhizophora apiculata, Bruguiera parviflora, Bruguiera gymnorhiza, Camptostemon schultzii, Xylocarpus spp.), while others are commonly found as undercanopy plants beneath the closed canopy (Aegiceras corniculatum, Cynometra iripa, Acanthus spp., Acrostichum speciosum, Ceriops decandra, and even Rhizophora stylosa in Moreton Bay, Queensland).
Spreading waters’edge tree of Sonneratia caseolaris, Daintree River, Queensland.
- A rockery setting for Aegialitis annulata, Shoalwater Bay, Queensland.
- Stunted thicket of Ceriops australia, Port Curtis, Queensland
Leafy Green in the Canopy
Leaves vary between species with mangroves having leaves that are simple (like Avicennia spp., Rhizophora spp., Sonneratia spp.), compound (like Cynometra spp., Xylocarpus spp.) or pinnate (Acrostichum speciosum). Shape varies within these basic leaf types, ranging from apiculate (like Rhizophora spp.), ovate (like Sonneratia alba), lanceolate (like Sonneratia lanceolata), to spathulate (like Lumnitzera spp.). Other characteristics of leaves also vary including: the leaf apex and tip from pointed (like Avicennia marina), round (like Avicennia integra, Camptostemon schultzii), imarginate (like Lumnitzera spp., Osbornia octodonta), or with a mucronate tip (like Rhizophora spp.); the leaf margin from entire (like Rhizophora spp.) to serrate (like Excoecaria agallocha), or spiny (like Acanthus ilicifolius); the surface from smooth and glabrous (like Bruguiera spp., Rhizophora spp., Ceriops spp.), to pubescent (like Heritiera littoralis), or with salt excreting glands (like Aegiceras corniculatum, Aegialitis annulata); containing milky sap (Excoecaria agallocha) or not; being large (like Heritiera littoralis) or small (like Pemphis acidula); or having distinctive petioles with pulvini (like Heritiera littoralis), or fully enclosing the stem (Aegialitis annulata). Leaves are used by a range of fauna including: crabs (notably Sesarmids that remove fallen leaves from the ground), moth caterpillars (notably removing standing green leaf surfaces), various leaf minors, thrips, crickets (causing various leaf damage), and grazing animals like horses, cattle and goats (causing significant canopy damage).
Glossy simple leaves of Ceriops australis.
- Small pubescent simple leaves of Pemphis acidula.
- Pinnate compound leaflets of Acrostichum speciosum.