Search

North Australian tropical savanna accounts for 12% of the world's total savanna land cover. Accordingly, understanding processes that govern carbon, water and energy exchange within this biome is critical to global carbon and water budgeting. Climate and disturbances drive ecosystem carbon dynamics. Savanna ecosystems of the coastal and sub-coastal of north Australia experience a unique combination of climatic extremes and are in a state of near constant disturbance from fire events (1 in 3 years), storms resulting in windthrow (1 in 5–10 years) and mega-cyclones (1 in 500–1000 years). Critically, these disturbances occur over large areas creating a spatial and temporal mosaic of carbon sources and sinks. We quantify the impact on gross primary productivity (GPP) and fire occurrence from a tropical mega-cyclone, tropical Cyclone Monica (TC Monica), which affected 10 400 km2 of savanna across north Australia, resulting in the mortality and severe structural damage to ~140 million trees. We estimate a net carbon equivalent emission of 43 Tg of CO2-e using the moderate resolution imaging spectroradiometer (MODIS) GPP (MOD17A2) to quantify spatial and temporal patterns pre- and post-TC Monica. GPP was suppressed for four years after the event, equivalent to a loss of GPP of 0.5 Tg C over this period. On-ground fuel loads were estimated to potentially release 51.2 Mt CO2-e, equivalent to ~10% of Australia's accountable greenhouse gas emissions. We present a simple carbon balance to examine the relative importance of frequency versus impact for a number of key disturbance processes such as fire, termite consumption and intense but infrequent mega-cyclones. Our estimates suggested that fire and termite consumption had a larger impact on Net Biome Productivity than infrequent mega-cyclones. We demonstrate the importance of understanding how climate variability and disturbance impacts savanna dynamics in the context of the increasing interest in using sava

Seismic methods have become common for the detection of low-throw faults ahead of underground coal mining. Surface seismic methods cannot theoretically be used where dykes occur, because seismic waves transmit from the surface down to the seams, and reflect back to the surface. Consequently, where sub-vertical structure such as dykes occurs, the surface seismic method fails. The ability of seismic methods to image dykes depends on the geometry used, the dyke thickness and the seismic wave propagation mode in relation to dyke composition and internal structure. Surface seismic methods find it difficult to distinguish between faults/fractures and very thin dykes (1-2m in thickness) when the dyke's thickness is less than the seismic wavelength. Consequently, borehole seismic methods have to be used to detect the presence of such thin dykes. This paper presents the first results from an ACARP project, which in part is a breakthrough in seismic technology for the detection of dykes. It explains how surface seismic methods were used to detect a thick dyke and associated faulting. An alternative approach, that of going downhole with seismic sources and receivers (borehole seismic profiling), shows that dyke sides can be imaged at depth, and that in future, it should be possible to produce an image of both sides of a dyke, in its correct orientation, using existing boreholes.

FISH & WILDLIFE REFERENCE LIBRARY US Army Corps of Engineers Walla Walla District Identification of Fall Chinook Salmon Spawning Sites Near Lower Snake River Hydroelectric Projects D. D. Cauble R. L. Johnson R. P. Mueller C. S. Abernethy B.J.Evans D.R. Geist October 1994 Pacific Northwest Laboratory P.O. Box 999 Richland, Washington 99352 Identification of Fall Chinook Salmon Spawning Sites Near Lower Snake River Hydroelectric Projects D. D. Dauble, R. L Johnson, R. P. Mueller, C. S. Abernethy, B. J. Evans, and D. R. Geist October 1994 Prepared for U.S. Army Corps of Engineers Wall a Wall a District Walla Walla, Washington 99362 by Pacific Nonhwest Laboratory P.O. Box 999 Richland, Washington 99352 Executive Summary Pacific Northwest Laboratory (PNL) initiated studies to identify potential spawning habitat of threatened fall chinook salmon (Oncorhynchus tshawytscha) stocks in areas downstream of four Snake River dams in fall 1993. This information was needed to provide guidelines for future operation of the lower Snake River hydroelectric system, including assessment of reservoir draw­down, and for site-specific construction planning. We used Geographic Information System (GIS) technology to direct our search areas. Suitable spawning habitat was initially defined using criteria based on substrate, velocity, depth, and slope characteristics of the tailrace areas. Elec­tronic maps of these habitat variables were provided for each of the four dam tailrace areas. Then, based on the area of common overlap, maps of potential spawning habitat, or spawning habitat polygons (SHPs), were created using GIS. Field surveys of the SHPs were conducted in November and December 1993, using an underwater video system. Survey locations were established at 25-to 100-ft intervals using shoreline markers as guides. For some surveys, the actual boat path within the SHP was logged using a Global Positioning System (GPS) and then compared with measurements made using standard surveying equi

Single crystals of La(1-x)Pb(x)MnO3 with 0.25 < x < 0.45 have been grown by the flux technique. X-ray fluorescence, wet chemical, and electron microprobe analyses indicate the crystals are homogeneous and stoichiometric. The crystal structure was determined to be a rhombohedrally distorted perovskite with double cell edges. (Author)