Nutrient partitioning and storage, nutrient use efficiency and below-ground decomposition of organic matter in mangroves along the arid coast of the Pilbara Region, Western Australia

The data were used to examine 3 different aspects of nutrient dynamics of mangrove forests in the arid coastal zone of north Western Australia: Below-ground decomposition; nutrient partitioning and storage; and nutrient use efficiency.Samples were collected during October to November 1993 and September 1994 from mangrove forests near Dampier, at Port Hedland, in the Bay of Rest (Exmouth Gulf) and at Mangrove Bay (Cape Range National Park). Forest characteristics recorded were: intertidal zone (low, mid and high); type (Rhizophora apiculata or Avicennia marina);Estimates of above-ground biomass were based on calculations of stems/ha and diameter at breast height (DBH). Net primary production was estimated using light interception methods and measurements of light absorption were used to estimate leaf area index. Below-ground biomass estimates (metric tons dry weight/ha) were made for living and dead roots. Net primary production was estimated using mol C/ha/day.Bulk sediment and nutrient sampling: samples were taken for grain size and water content; temperature, redox potential and pH were measured; samples for solid-phase nutrients and porewater were obtained. Samples were analysed for ammonium, nitrite, nitrate, silicate, phosphate, DON and DOP. Separate samples were taken for sulphate and methane, TOC, TC and TN values .Flux measurements of CO2 production were estimated using a core incubation method. Net rates of Mn and Fe were estimated using a different core incubation method, and rates of sulphate reduction were measured using a core injection technique. Gas (O2, CO2, methane) and solute (silicate, phosphate, DOP, DON, ammonium, nitrite, nitrate) fluxes were also measured.Sediment respiration to forest net primary production (TCOx/NPP ratios) was calculated. Individual trees were cut and divided into component parts and analyses carried out on each component.Nutrient use efficiency was estimated on the basis of productivity per nutrient uptake or loss using litter fall rates and rates of leaf CO2 exchange.
 To examine differences between 3 Rhizophora stylosa and 3 Avicennia marina forests in different coastal settings of arid Western Australia. Above and below ground nutrients, trace elements concentrations were estimated and the efficiency of the use of nutrients related to primary productivity were estimated.To determine the impact of intertidal position, tidal range, and coastal geomorphology on differences and similarities in biogeochemical processes and forests of A. marina and R. stylosa.To collect data, to compare arid zone mangroves with the more studied mangrove forests of the northeast Australian humid tropics, three to four permanent study plots were established to carry out long term observational and experimental studies in the region.Permanent study plots were established to carry out long-term observational and experimental studies in the region and to collect data to compare arid zone mangroves with the more studied, mangrove forests of the northeast Australian humid tropics.
 Experiments were set up to measure leaf fall and degradation within these forests. Soil characteristics, including particle size, dissolved and particulate nutrients, salinity and heavy metal content, and microbial parameters such as bacterial sulfite reduction, were determined at each site.One component of this project was to test the hypothesis that regional mangrove forest structure and growth, mangrove-based food chains and soil biogeochemistry are strongly regulated by aridity. Research was designed to provide scientific information necessary to assess current and potential impacts of human activities on mangroves, including recovery from oil spills, heavy metal stress, changes in soil salinities from salt pond construction and sea level rise. Surveys were also carried out to establish sites for estimating potential impacts of sea level rise on regional mangrove communities.Replicate plots were established in mangrove forests near Dampier, at Port Hedland, in the Bay of Rest (Exmouth Gulf) and Mangrove Bay (Cape Range National Park). These sites encompass most of the important geomorphological settings in which mangrove forests occur in the Pilbara region.At each of the above locations, three to four permanent plots were established in canopy forests of Avicennia marina and Rhizophora stylosa, the dominant mangrove tree species in the region. All trees in each plot were tagged and measured to initiate long-term measurements of trunk growth, net biomass production and tree survival. Where seedlings occurred in the understorey, they were tagged to follow their growth and survival.

Organization: Australian Ocean Data Network