Cottagers in an Urban Field

The use of rural areas by the urban population is an important organizing principle in the study of the rural hinterland of urban centers. One of the important land uses identified within the urban field is recreation. This paper focuses on cottage property ownership in one part of the urban field, the rural-recreational countryside. Using three case studies from Canada, it was found that cottage properties account for a large proportion of local residential property. Although most cottage properties are owned by urban residents, up to one-quarter are owned by local residents. Using a questionnaire survey, it was also found that cottage owners are more likely to be older, better educated, and have higher incomes than rural residents.     

Climate Change Impacts for the Conterminous USA: An Integrated Assessment

Human activities have altered the distribution and quality of terrestrial ecosystems. Future demands for goods and services from terrestrial ecosystems will occur in a world experiencing human-induced climate change. In this study, we characterize the range in response of unmanaged ecosystems in the conterminous U.S. to 12 climate change scenarios. We obtained this response by simulating the climatically induced shifts in net primary productivity and geographical distribution of major biomes in the conterminous U.S. with the BIOME 3 model. BIOME 3 captured well the potential distribution of major biomes across the U.S. under baseline (current) climate. BIOME 3 also reproduced the general trends of observed net primary production (NPP) acceptably. The NPP projections were reasonable for forests, but not for grasslands where the simulated values were always greater than those observed. Changes in NPP would be most severe under the BMRC climate change scenario in which severe changes in regional temperatures are projected. Under the UIUC and UIUC + Sulfate scenarios, NPP generally increases, especially in the West where increases in precipitation are projected to be greatest. A CO₂-fertilization effect either amplified increases or alleviated losses in modeled NPP. Changes in NPP were also associated with changes in the geographic distribution of major biomes. Temperate/boreal mixed forests would cover less land in the U.S. under most of the climate change scenarios examined. Conversely, the temperate conifer and temperate deciduous forests would increase in areal extent under the UIUC and UIUC + Sulfate scenarios. The Arid Shrubland/Steppe would spread significantly across the southwest U.S. under the BMRC scenario. A map overlay of the simulated regions that would lose or gain capacity to produce corn and wheat on top of the projected distribution of natural ecosystems under the BMRC and UIUC scenarios (Global mean temperature increase of +2.5 °C, no CO₂ effect) helped identify areas where natural and managed ecosystems could contract or expand. The methods and models employed here are useful in identifying; (a) the range in response of unmanaged ecosystem in the U.S. to climate change and (b) the areas of the country where, for a particular scenario of climate change, land cover changes would be most likely.     

Intermittency of riometer auroral absorption observed at South Pole

Auroral radio-wave absorption values measured at South Pole for 3 years using a riometer are analyzed in order to test whether they show evidence of intermittency. The properties of the parameters of the probability density functions determined for several magnetic local time sectors are found to be significantly different. The probability density functions for the pre-midnight sector show the typical shape associated to intermittency. No results are given for the afternoon sector because few auroral absorption events meet the selection criteria to give statistically significant results. It is suggested that if the precipitating particle population responsible for the riometer auroral absorption shared the intermittency features of the absorption then the present results would allow the study of the properties of the induction component of magnetospheric turbulence.     

Eddy correlation measurements of CO2, latent heat,and sensible heat fluxes over a crop surface

Eddy correlation equipment was used to measure mass and energy fluxes over a soybean crop. A rapid response CO₂ sensor, a drag anemometer, a Lyman-alpha hygrometer and a fine wire thermocouple were used to sense the fluctuating quantities.Diurnal fluxes of sensible heat, latent heat and CO₂ were calculated from these data. Energy budget closure was obtained by summing the sensible and latent heat fluxes determined by eddy correlation which balanced the sum of net radiation and soil heat flux. Peak daytime CO₂ fluxes were near 1.0 mg m^–2 (ground area) s^–1.The eddy correlation technique was also employed in this study to measure nocturnal CO₂ fluxes caused by respiration from plants, soil, and roots. These CO₂ fluxes ranged from - 0.1 to - 0.25 mg m^–2s^–1.From the data collected over mature soybeans, a relationship between CO₂ flux and photosynthetically active radiation (PAR) was developed. The crop did not appear to be light-saturated at PAR flux densities < 1800 Ei m^–2 s^–1. The light compensation point was found to be about 160 Ei m^–2 s^–1.Published as Paper No. 7402, Journal Series, Nebraska Agricultural Experiment Station. The work reported here was conducted under Nebraska Agricultural Experiment Station Project 27-003 and Regional Research Project 11–33.Post-doctoral Research Associate, Professor and Professor, respectively. Center for Agricultural Meteorology and Climatology, Institute of Agriculture and Natural Resources, University of Nebraska, Lincoln, NE 68583-0728.     

Characterization of the ecological quality of the coastal Gulf of Lions (NW Mediterranean). A comparative approach based on three biotic indices

The ecological quality of the Gulf of Lions coast was assessed using three biotic indices (H', AMBI and BQI). The three indices correlated positively. The positive correlation between AMBI and BQI was surprising and was mostly due to the fact that the dominant species Ditrupa arietina featured a low ES50(0.05) but was classified in GI by AMBI. Both H' and BQI were efficient in distinguishing impacted from un-impacted sites but AMBI was not. Differences between H' and BQI were mainly due to the scale used to translate indices in terms of EcoQ. The three indices were able to detect the major changes in macrofauna composition, which occurred in the Bay of Banyuls-sur-Mer during the last 40years. However, the interpretations of such changes in terms of EcoQ differed between indices. These results are discussed relative to the characteristics of the tested indices.     

Efficiency of phosphorus accumulation by plankton,periphyton developed on submerged artificial substrata and metaphyton: in-situ observation in two shallow ponds

Phosphorus overenrichment of shallow ponds prevailing in wetlands leads to their eutrophication causing the collapse of those vulnerable habitats. The potential...     

Chemical reaction rates and entrainment within the Endeavour Ridge hydrothermal plume

The aging of the hydrothermal plume over the Endeavour segment of the Juan de Fuca Ridge was estimated by measuring the²²²Rn³He ratio in the plume as it dispersed. Despite uncertainties in the source function of hydrothermal input, it wa determined that the relative sequence of removal from the plume isH₂ > Δc >²²²Rn>CH₄ Mn, whereΔc is a measure of particle concentration and the mean life of²²²Rn is 5.5 days. H₂ is removed from the plume within hours of input while Mn is not removed within the two-week timescale of the radon-helium clock.Entrainment of bottom water within the buoyant plume may introduce additional chemical signatures into the spreading effluent layer over that which would be introduced by hydrothermal discharge alone. This is particularly significant for those chemical species which are not greatly enriched in the vent fluids relative to bottom water concentration and which display a nutrient-like profile in the deep ocean. Thus we found that significant fractions of the Si and²²⁶Ra anomalies in the plume were not of hydrothermal origin but were derived from entrained bottom water which has a higher concentration of these elements than ambient water at plume height.     

Partition of Forecast Error into Positional and Structural Components

Weather manifests in spatiotemporally coherent structures. Weather forecasts hence are affected by both positional and structural or amplitude errors. This has been long recognized by practicing forecasters(cf., e.g.,Tropical Cyclone track and intensity errors). Despite the emergence in recent decades of various objective methods for the diagnosis of positional forecast errors, most routine verification or statistical post-processing methods implicitly assume that forecasts have no positional error.The Forecast Error Decomposition(FED) method proposed in this study uses the Field Alignment technique which aligns a gridded forecast with its verifying analysis field. The total error is then partitioned into three orthogonal components:(a) large scale positional,(b) large scale structural, and(c) small scale error variance.The use of FED is demonstrated over a month-long MSLP data set. As expected, positional errors are often characterized by dipole patterns related to the displacement of features, while structural errors appear with single extrema, indicative of magnitude problems. The most important result of this study is that over the test period, more than 50% of the total mean sea level pressure forecast error variance is associated with large scale positional error. The importance of positional error in forecasts of other variables and over different time periods remain to be explored.