Functional Diversity in the Hyper-diverse Mangrove Communities in Papua New Guinea

Variation in plant functional traits reflect the differences in an environment a species occupies and the variation in the functional traits across an environmental gradient and growth form reflects the functional performance of the coexisting species. Therefore, detecting the differences in functional traits of species is important to our understanding of the performance of species. The leaf functional traits; Leaf mass per area (LMA) and vein density (D_V) are key traits in the resource use strategies and photosynthetic gas exchange capacity (A_max, g_smax) of all plants. Mangroves occupy a hypersaline narrow ecological range and therefore are thought to have uniform functional performance. This view makes sense for low diversity mangrove communities, but what about the hyperdiversity communities such as those in New Guinea? A comprehensive review of the present understanding on the ecology and socio-ecological values of mangrove was undertaken to establish a good foundational understanding of my study on New Guinea mangroves (Chapter 1). It is widely held that mangroves thriving in a hypersaline environment experience high water constraints and as a result have high water use efficiency, therefore have narrow functional performance. I investigated the leaf and photosynthetic functional traits of 31 mangrove species among different zonation bands and growth from six mangrove communities in New Guinea to test the view that mangroves have a narrow functional performance (Chapter 2). I then investigated the differences in wood and stem hydraulic traits among different zonation bands and growth forms and the relationship between wood hydraulics and leaf photosynthetic gas assimilation functional performance to further test the long standing view that mangroves have a narrow functional performance (Chapter 3). I then summarized the major findings of my two studies and their implications on mangrove restoration and rehabilitation with particular reference to the recent mangrove rehabilitation initiatives in Papua New Guinea (Chapter 4). My studies on leaf and wood functional traits across different zonation bands, growth forms and root system types consistently revealed that mangroves have a wide functional performance, and different species exhibited different resource use strategies.