Phosphorus Availability and Salinity Control Productivity and Demography of the Seagrass <Emphasis Type="Italic">Thalassia testudinum</Emphasis> in Florida Bay

Biomass, net primary productivity (NPP), foliar elemental content, and demography of Thalassia testudinum were monitored in populations from five sites across Florida Bay beginning in January 2001. Sites were selected to take advantage of the spatial variability in phosphorus (P) availability and salinity climates across the bay. Aboveground biomass and NPP of T. testudinum were determined five to six times annually. Short-shoot demography, belowground biomass, and belowground NPP were assessed from a single destructive harvest at each site and short-shoot cohorts were estimated from leaf scar counts multiplied by site-specific leaf production rates. Biomass, relative growth rate (RGR), and overall NPP were positively correlated with P availability. Additionally, a positive correlation between P availability and the ratio of photosynthetic to non-photosynthetic biomass suggests that T. testudinum increases allocation to aboveground biomass as P availability increases. Population turnover increased with P availability, evident in positive correlations of recruitment and mortality rates with P availability. Departures from seasonally modeled estimates of RGR were found to be influenced by salinity, which depressed RGR when below 20 psu or above 40 psu. Freshwater management in the headwaters of Florida Bay will alter salinity and nutrient climates. It is becoming clear that such changes will affect T. testudinum, with likely feedbacks on ecosystem structure, function, and habitat quality.     

Coastal paleogeography and human occupation of the Western Alaska Peninsula

Geological and archaeological investigations on the western Alaska Peninsula establish relationships between postglacial sea level changes and regional settlement patterns, which are linked to the spatial and temporal distribution of marine and estuarine resources. Isostatic emergence dominated relative sea‐level changes since deglaciation, but erosional landforms and gaps in the archaeological record suggest that site preservation has varied because of the interplay of eustatic sea level rise, isostatic uplift, and tectonic deformation. Coastal subsidence associated with a major earthquake about 2200 yr B.P. is linked with a 300‐year hiatus in the regional archaeological record. A shift from estuarine to littoral and offshore resources following this period demonstrates the impact of such dynamic sea level fluctuations on the shape and biological productivity of the coastal zone. However, changes in village organization, house form, and subsistence base that define several archaeological phases arise from both environmental and sociopolitical instability. Models of culture change should accommodate local and regional geological boundary conditions in the North Pacific and similarly dynamic settings. © 2000 John Wiley & Sons, Inc.     

Parameterization of the CCN-humidity spectrum in dependency on nucleation conditions and aerosol size distribution

Summary Atmospheric CCN-humidity spectra (describing the CCN-number concentration as function of supersaturation) are derived as the integral over given particle size distributions. In that concept the finite boundary, representing the limiting activated particle size, results from the critical values of the Köhler-curve. As utilization of this general outcome different representative aerosol size distributions of the power law type as well as the log-normal type are chosen for case studies which are compared to empirical results. The dependency on temperature of the limiting activated particle size is shown to provide a non-negligible influence on the number of activated particles.With 3 Figures     

Theoretical studies of the parameterization of the non-neutral surface boundary layer

The parameterization of the non-neutral atmospheric surface layer has been reexamined using the basic principles of small-scale energetics and thermodynamics. On the basis of this more complete treatment, theK-parameterization has been reformulated. It is found that the linear regression laws between fluxes and driving gradient forces of the turbulent heat and humidity exchanges in the surface layer can be derived in a much more comprehensive manner than by using the commonly used K-theory. With respect to stationary conditions and in the context of similarity concepts, a system of algebraic equations has been formulated which provides reasonable estimates of the distributions of the dimension less rates of viscous energy dissipation as well as turbulent kinetic and thermal-diffusive energy transport as functions of the variablez/L. Quantitative calculations have been performed using the scaling height formulations of Takeuchi and Yokoyama, Prandtl, and von Karman as closure conditions of the equations.     

Magnetotelluric investigation on Björkö impact structure,west of Stockholm,Sweden

This paper describes the application of magnetotelluric (MT) method to investigate Björkö impact structure located at west of Stockholm, Sweden. This structure has formed in crystalline rocks ca. 1.2 Ga ago and located relatively close to the district heating infrastructure of the Stockholm region, as the largest district heating system in Europe. Since impact structures mostly contain fractured rock volumes in the form of breccia formations, the occurred brecciation zones in this region are more favorable potential targets for geothermal investigations. The main objective is evaluating the capability of the study area to have potential for geothermal resources by mapping the subsurface structure. To image electrical characteristic of underground layers, 1D and 2D bimodal inversions of TE and TM modes of MT data are performed. The results are also compared with the outputs of the inversion of the determinant data (yielding a direction-independent average of the subsurface conductivity) along the same profiles, proving good accordance of the outputs. The processed resistivity sections at depth along with measuring various rock physical properties across two drilled boreholes at Björkö and Midsommar islands localized two conductors at depths of 1 km and from 2.5 to 4.5 km, which may be attributed to be a potential zone for geothermal energy retrieval.     

Emission and absorption of cyclotron radiation in non-equilibrium plasma

From the kinetic Klimontovich theory we derive the equation of radiative transfer for the case of homogeneous and stationary nonequilibrium plasma in a magnetic fiel. For the sake of simplicity we shall consider only the propagation of cyclotron-radiation in the direction of the magnetic field. Explicit expressions for the coefficients of absorption and spontaneous emission, valid also at the cyclotron frequency, will be obtained. In the final results the plasma is allowed to be weakly inhomogeneous in the z-direction. Application is made of the theory to the simple equilibrium case as a test yields the Rayleigh-Jeans formula of the black-body-radiation.