Biogeochemical parameters of sea water and bottom sediments near the Curieuse Island (Seychelles Islands)

Biogeochemical reef studies carried out in 1981 and 1984 found low concentration of total natural and anthropogenic hydrocarbons in inshore waters. Detection of lignin in marine and bottom sediments indicates that the land has major effect on makeup of organic matter there. Comparison of compositions of organic matter in sea water, suspended matter and bottom sediments indicated that it was altered rapidly by the reef community. Thus, in the inshore zone of the island, runoff from the land is important in supplying nutrients to the reef ecosystem alongside with transport of nutrients by deep waters. Concentrations of nutri¬ents (N, P) in the inshore zone are higher than in waters of the tropical part of the ocean. Nitrogen is the limiting element in development of phytoplankton in the inshore zone.

Sedimentological investigations of a sediment core profile from the continental slope of the South Orkney Islands

Sediment patterns such as texture, composition, and facies from three selected areas of the Antarctic continental margin of the Weddell Sea are discussed in relation to environmental variations of the Quaternary hydrosphere and kryosphere. Advance and retreat of ice shelves as well as oscillations in sea ice coverage are reflected by particular sediment facies. The distribution of ice-rafted detritus tracks the Antarctic Coastal Current, and the Weddell Sea Bottom water contour current can be recognized by its distinctive winnowing and erosion pattern. Distribution and abundance of biogenic sediment components are mainly controlled by duration of sea ice coverage reflecting the long-term climatic evolution.

Locally produced wood biochar increases nutrient retention in agricultural soils of the San Juan Islands, WA, USA

Thesis (Master's)--University of Washington, 2016-06

Forest Resource Islands in a Sub-tropical Marsh: Soil–Site Relationships in Everglades Hardwood Hammocks

Spatial heterogeneity in soils is often characterized by the presence of resource-enriched patches ranging in size from a single shrub to wooded thickets. If the patches persist long enough, the primary constraint on production may transition from one limiting environmental factor to another. Tree islands that are scattered throughout the Florida Everglades basin comprise nutrient-enriched patches, or resource islands, in P-limited oligotrophic marshes. We used principal component analysis and multiple regressions to characterize the belowground environment (soil, hydrology) of one type of tree island, hardwood hammocks, and examined its relationship with the three structural variables (basal area, biomass, and canopy height) indicative of site productivity. Hardwood hammocks in the southern Everglades grow on two distinct soil types. The first, consisting of shallow, organic, relatively low-P soils, is common in the seasonally flooded Marl Prairie landscape. In contrast, hammocks on islands embedded in long hydroperiod marsh have deeper, alkaline, mineral soils with extremely high P concentrations. However, this edaphic variation does not translate simply into differences in forest structure and production. Relative water depth was unrelated to all measures of forest structure and so was soil P, but the non-carbonate component of the mineral soil fraction exhibited a strong positive relationship with canopy height. The development of P-enriched forest resource islands in the Everglades marsh is accompanied by the buildup of a mineral soil; however, limitations on growth in mature islands appear to differ substantively from those that dominate incipient stages in the transformation from marsh to forest. Key words: resource island; tree

Across-scale patterning of plant-soil-water interactions surrounding tree islands in Southern Everglades landscapes

The freshwater Everglades is a complex system containing thousands of tree islands embedded within a marsh-grassland matrix. The tree island-marsh mosaic is shaped and maintained by hydrologic, edaphic and biological mechanisms that interact across multiple scales. Preserving tree islands requires a more integrated understanding of how scale-dependent phenomena interact in the larger freshwater system. The hierarchical patch dynamics paradigm provides a conceptual framework for exploring multi-scale interactions within complex systems. We used a three-tiered approach to examine the spatial variability and patterning of nutrients in relation to site parameters within and between two hydrologically defined Everglades landscapes: the freshwater Marl Prairie and the Ridge and Slough. Results were scale-dependent and complexly interrelated. Total carbon and nitrogen patterning were correlated with organic matter accumulation, driven by hydrologic conditions at the system scale. Total and bioavailable phosphorus were most strongly related to woody plant patterning within landscapes, and were found to be 3 to 11 times more concentrated in tree island soils compared to surrounding marshes. Below canopy resource islands in the slough were elongated in a downstream direction, indicating soil resource directional drift. Combined multi-scale results suggest that hydrology plays a significant role in landscape patterning and also the development and maintenance of tree islands. Once developed, tree islands appear to exert influence over the spatial distribution of nutrients, which can reciprocally affect other ecological processes.

Water source utilization and foliar nutrient status differs between upland and flooded plant communities in wetland tree islands

Tree islands in the Everglades wetlands are centers of biodiversity and targets of restoration, yet little is known about the pattern of water source utilization by the constituent woody plant communities: upland hammocks and flooded swamp forests. Two potential water sources exist: (1) entrapped rainwater in the vadose zone of the organic soil (referred to as upland soil water), that becomes enriched in phosphorus, and (2) phosphorus-poor groundwater/surface water (referred to as regional water). Using natural stable isotope abundance as a tracer, we observed that hammock plants used upland soil water in the wet season and shifted to regional water uptake in the dry season, while swamp forest plants used regional water throughout the year. Consistent with the previously observed phosphorus concentrations of the two water sources, hammock plants had a greater annual mean foliar phosphorus concentration over swamp forest plants, thereby supporting the idea that tree island hammocks are islands of high phosphorus concentrations in the oligotrophic Everglades. Foliar nitrogen levels in swamp forest plants were higher than those of hammock plants. Linking water sources with foliar nutrient concentrations can indicate nutrient sources and periods of nutrient uptake, thereby linking hydrology with the nutrient regimes of different plant communities in wetland ecosystems. Our results are consistent with the hypotheses that (1) over long periods, upland tree island communities incrementally increase their nutrient concentration by incorporating marsh nutrients through transpiration seasonally, and (2) small differences in micro-topography in a wetland ecosystem can lead to large differences in water and nutrient cycles.

A Geospatial Database of Tree Islands within the Mustang Corner Fire Incident of 2008

Fire, which affects community structure and composition at all trophic levels, is an integral component of the Everglades ecosystem (Wade et al. 1980; Lockwood et al. 2003). Without fire, the Everglades as we know it today would be a much different place. This is particularly true for the short-hydroperiod marl prairies that predominate on the eastern and western flanks of Shark River Slough, Everglades National Park (Figure 1). In general, fire in a tropical or sub-tropical grassland community favors the dominance of C4 grasses over C3 species (Roscoe et al. 2000; Briggs et al. 2005). Within this pyrogenic graminoid community also, periodic natural fires, together with suitable hydrologic regime, maintain and advance the dominance of C4 vs C3 graminoids (Sah et al. 2008), and suppress the encroachment of woody stems (Hanan et al. 2009; Hanan et al. unpublished manuscript) originating from the tree islands that, in places, dominate the landscape within this community. However, fires, under drought conditions and elevated fuel loads, can spread quickly throughout the landscape, oxidizing organic soils, both in the prairie and in the tree islands, and, in the process, lead to shifts in vegetation composition. This is particularly true when a fire immediately precedes a flood event (Herndon et al. 1991; Lodge 2005; Sah et al. 2010), or if so much soil is consumed during the fire that the hydrologic regime is permanently altered as a result of a decrease in elevation (Zaffke 1983).