Добірка наукової літератури з теми "Mangrove swamps Victoria Western Port"

The metabolism of organic nitrogen compounds in sediments from salt-marsh (Sarcocornia quinqueflora) and mangrove (Avicennia marina) areas at Western Port, Victoria, was investigated. Organic nitrogen compounds were metabolized at potential rates of up to 3.9 �mol cmF3 day-1 for amino acids, 23 �mol cm-3 day-( for dipeptides, and 5 �mol cm-1 day-1 for an amide. These were higher than the rate of ammonium regeneration in the absence of added substrate (<0.08 �mol cm-3 day-1); this indicates that organic nitrogenous compounds play a major role in nutrient cycling in coastal sediments. Rates of some transformations were highly correlated with sediment organic-matter content, total nitrogen content or concentration of soluble reactive phosphorus in the sediments, but overall there were few significant correlations between metabolic rates and edaphic conditions. Degradation of organic nitrogenous compounds in these sediments is likely to be influenced strongly by the availability of phosphorus, the quantity and quality of detrital inputs, and the size and activity of microbial populations.

Sediments from mangrove and saltmarsh areas at Yaringa, Western Port contained high concentrations of chloride (c. 330-2100 mmol per litre of interstitial water) and sodium (c. 320-1900 mmol 1-1). The concentrations recorded during the study were highest in March and lowest in July-August; salinity in the marsh during summer was considerably higher than that commonly reported for saltmarshes in other parts of the world. Sediment ammonium contents (c. 180-580 nmol per cm3 of fresh sediment) were variable across the marsh and throughout the sampling period, with there being little overall pattern to these changes. In contrast, concentrations of nitrate plus nitrite were low (< 100 nmol cm3) for most of the year except for a period in March when they were extremely high (c. 1100-1800 nmol cm-3). The leaf-cell sap of all saltmarsh and mangrove plants contained high concentrations of chloride (c. 300-1200 mmol per litre of cell sap), sodium (c. 280-900 mmol l-1) and potassium (c. 40-200 mmol l-1). Glycinebetaine was accumulated in the leaf-cell sap to concentrations of up to about 90 mmol l-1 by Atriplex paludosa, Avicennia marina, Sarcocornia quinqueflora, Sclerostegia arbuscula and Suaeda australis. Proline and glycinebetaine were accumulated by Limonium australe, Samolus repens, Selliera radicans and Triglochin striata, but no species accumulated proline alone. Concentrations of inorganic osmotica in the foliage were generally highest in March, whereas glycinebetaine and proline were at their most concentrated in April. No significant relationship was detected between concentrations of organic osmotica in the plants and that of salt or inorganic nitrogen in the sediments.

The historic influence of human fire and the role of ‘top-down’ vs ‘bottom-up’ drivers on ecosystems globally is highly contested, and our knowledge of regime diversity is poor. This paper uses an early European account as a case study to describe Aboriginal fire history in south-eastern Australia based on links between fire and: grasslands, native foods and culture. The route and observations detailed in Assistant Protector William Thomas’ 1840 account of a journey led by Aborigines to Western Port, Victoria, were overlayed with grass-tree boundaries compiled from historic plans. The narrative provides direct evidence of up to moderate-scale and intensity burns (with minimal fine-scale patchiness), undertaken in the height of the dry season, opportunistically linked to rainfall. The fires targeted open grassy ‘plains’ to maintain and access preferred hunter-gathering grounds. A synthesis of the earliest records supports high frequency anthropogenic burning maintaining alternative vegetation states with dynamic boundaries on elevated alluvial plains and, in places, adjoining swamps. The narrative represents an important primary source for studying traditional society, including the description of a local historic fire regime (‘koyuga burning’). Establishing such a fire regime ‘benchmark’ has the potential to stimulate new interdisciplinary research around the complex processes controlling grass-tree patterns, and build confidence that fire-stick farming was potentially instrumental in grassland formation, and integral to grassland maintenance throughout this region.

Wanyonyi SN, Mwangi EM, Gichuki N. 2018. Effect of habitat disturbance on distribution and abundance of Papyrus endemic birds in Sio Port Swamp, Western Kenya. Bonorowo Wetlands 2: 49-60. Papyrus (Cyperus papyrus) swamps are found patchily around the shores of Lake Victoria mainly along river inflows. The objective of this study was to investigate the distinct forms of habitat disturbance and their implications on the distribution and abundance of papyrus endemic birds. Data on bird counts, habitat quality, and types of disturbance were collected for six months, from October 2013 to March 2014. Total bird counts were established using Timed Species Count (TSC) and playback call technique at every fixed point. The researcher waited for 1 minute, calls of the study species were played to elicit a response of the secretive papyrus endemic birds. The number of each bird's species seen or heard within a radius of 25 meters was recorded for the next 9 minutes before transferring to the next point count. Habitat quality such as height, density, and level of maturity was determined in 1 m2 plots along transverse transects. Opportunistic observations were made to establish forms of disturbance present during vegetation and bird surveys. Papyrus endemic birds were highly distributed in sites with pure papyrus (55.58%) than in places with mixed plants (44.42%). The abundance of three endemic birds, White-winged Swamp-warbler, Papyrus Gonolek, and Northern Brown-throated Weaver, was significantly different in mixed and pure papyrus sites. However, the abundance of Greater Swamp-warbler was not significantly different in mixed and pure papyrus sites in Sio Port Swamp during the study period. Forms of habitat disturbance established were vegetation clearing and invasion by terrestrial and aquatic plants. As many as 76.47% of papyrus vegetation were young and regenerated (0-2 m high), 19.65% were immature papyruses (2-4 m) whereas 3.88% were tall mature papyruses (4-6 m high). The abundance of papyrus endemic birds was positively and significantly correlated with the density of vegetation in height ranging from 4-6 m. Thus, any change in papyrus density changed the abundance of papyrus endemic birds. Advance management of papyrus clearing is necessary for the long-term conservation of biodiversity.

A new genus, Cryptassiminea, is introduced for the taxon previously known as Assiminea buccinoides (Quoy & Gaimard). These small gastropods are abundant in mangrove and salt marsh habitats in south-eastern and subtropical eastern Australia. Seven species (five new) are recognised using morphological characters in the complex previously treated as a single species. Five taxa have rather narrow ranges while the other two are widespread and often sympatric. Two groups of species are recognised. One contains Cryptassiminea buccinoides, widespread in south-east and east Australia, and two closely related allopatric taxa from South Australia and south-eastern Tasmania (C. adelaidensis, sp. nov. and C. kershawi, sp. nov.). A second group of species is typified by Cryptassiminea tasmanica (Tenison-Woods), also widespread in east and south-east Australia and often sympatric with C. buccinoides. Allied to C. tasmanica, are two closely related taxa from western Victoria: C. glenelgensis, sp. nov. from the Glenelg River estuary and C. surryensis, sp. nov. from the Surry River estuary and Western Port, in the vicinity of Geelong. A distinctive species, Cryptassiminea insolata, sp. nov. from the east coast of Queensland, also has similarities with C. tasmanica. A cladistic analysis using morphological characters of the Cryptassiminea taxa and three other genera of Assimininae, with an omphalotropidine as the outgroup, resulted in a single tree. The new genus has rather poor support, possibly because many of its characters appear to be plesiomorphic within Assimineinae. Cryptassiminea is defined by a unique combination of characters but lacks any obvious synapomorphy. Two clades within Cryptassiminea are well supported, each containing the species-groups referred to above.

The promotion of sedimentation by mangrove ecosystems with adequate sediment supply has been well documented. However, predicting the amount of accretion or erosion at a specific point, is difficult due to the inherent stochasticity of sediment movement and deposition. Forcings which have been thought to influence short-term sedimentation rates, such as the amount of suspended matter in the incoming water, the wave regime at the site, elevation above sea level, distance from the low tide mark, and vegetation density, were investigated using large arrays of erosion pins at five sites around Western Port, Victoria over the course of one and a half years. We analyzed large scale/short-term and small-scale/longer-term vertical displacement within and between sites, and quantified small-scale intra-site variability. Results show, that while all study sites within Western Port were accreting sediment, they were not doing so at the same rate, and both intra-site and inter-site variability is high. Short-term large-scale or site wide analysis shows that total suspended matter and significant wave height (SWH) did not significantly affect vertical displacement rates. Surprisingly, neither distance from water nor vegetation density significantly affected vertical displacement or explain the spatial distribution of accretion and erosion within the sites. The coefficient of variation at each pin shows that there is high temporal variability in vertical displacement at each location, with individual pins alternating between erosion and accretion over time. Our study finds that while large scale (1 km2) patterns of sedimentation are temporally consistent, small scale patterns (&lt; 100 m2) are difficult to predict. This small-scale stochasticity therefore compounds management of mangrove ecosystems, especially as it relates to predicting the response to sea level rise. Thus, investment in small scale management of vegetation density, or microtopography, is perhaps not required for overall shoreline stability with sea level rise and blue carbon accumulation, making ecosystem restoration more feasible where resources are limited. However, at larger, forest-wide, spatial scales a higher level of predictability exists such as the overall response of the coastal tract to prevalent wave energy and sediment supply.