Improved daily precipitation nitrate and ammonium concentration models for the Chesapeake Bay Watershed

Daily precipitation nitrate and ammonium concentration models were developed for the Chesapeake Bay Watershed (USA) using a linear least-squares regression approach and precipitation chemistry data from 29 National Atmospheric Deposition Program/National Trends Network (NADP/NTN) sites. Only weekly samples that comprised a single precipitation event were used in model development. The most significant variables in both ammonium and nitrate models included: precipitation volume, the number of days since the last event, a measure of seasonality, latitude, and the proportion of land within 8km covered by forest or devoted to industry and transportation. Additional variables included in the nitrate model were the proportion of land within 0.8km covered by water and/or forest. Local and regional ammonia and nitrogen oxide emissions were not as well correlated as land cover. Modeled concentrations compared very well with event chemistry data collected at six NADP/AirMoN sites within the Chesapeake Bay Watershed. Wet deposition estimates were also consistent with observed deposition at selected sites. Accurately describing the spatial distribution of precipitation volume throughout the watershed is important in providing critical estimates of wet-fall deposition of ammonium and nitrate.     

Spatial and temporal analysis of vegetation change in agricultural landscapes: A case study of two brigalow (Acacia harpophylla) landscapes in Queensland, Australia

The majority of landscapes around the world have been modified or transformed by human activities to meet the needs of human societies. The loss of native vegetation for agricultural development affects the sustainability of growing proportion of the world's ecosystems. Factors such as land tenure, roads and agricultural intensification, together with biophysical properties, have been cited as drivers of deforestation. This paper combined analysis of the historical drivers of change with analysis of the trends of deforestation since 1945 in two brigalow landscapes (100,000 ha) in sub-tropical Australia. A selection of these drivers were then applied at a property-level (1000 ha) to test their influence on native vegetation retention. Regression trees were used to identify significant human drivers and biophysical properties, and then a generalised linear modelling approach was used to quantify the effect of these factors on the proportion of remnant native vegetation. Results showed that until the mid-20th century, government policies to intensify settlement did not result in increased agricultural production, but since this time, landscape change has been rapid, and has particularly affected ecosystems on fertile clay soils. Although socio-economic factors were critical in driving deforestation, after 60 years of agricultural intensification by far the most significant explanatory variable determining the proportion of native vegetation retained at a property scale was the suitability of the soil for agriculture. Property size was an important secondary influence. The results were not, by and large, consistent with other studies of landscape change and suggest that generalised principles explaining deforestation may be elusive. Solutions to the problem of over-clearance of native vegetation, therefore, need to be tailored to the specific regional situations encountered.     

Managing crop residues, fertilizers and leaf litters to improve soil C, nutrient balances, and the grain yield of rice and wheat cropping systems in Thailand and Australia

This paper reports on the influence that residue and fertilizer management have on nutrient balances, soil organic matter (SOM) dynamics, and crop yields of a flooded rice system in northeast Thailand (1992–1997) and a wheat–forage legume rotation in eastern Australia (1992–1998). Both soils had been subject to at least 18 years of cultivation and had lost up to 90% of the original labile (C_L) and 85% of the total carbon (C_T).For the rainfed rice cropping systems of northeast Thailand, a system is described in which small applications of leaf litter from locally grown trees are applied annually to rice paddy soils prior to transplanting. Annual applications of 1500 kg ha⁻¹ of leaf litter from different locally grown shrubs for five seasons resulted in increases in rice grain yield in 1997 of between 20 and 26% above the no-leaf litter control. Nutrient balances, determined by the difference between the inputs (fertilizer and added leaf litters) and outputs (grain and straw), indicated net positive balances of up to 457 kg N ha⁻¹, and 60 kg P ha⁻¹, after five seasons of leaf litter applications. Sulfur and potassium balances resulted in net deficits of up to −13 kg S ha⁻¹ and −52 kg P ha⁻¹, where no leaf litter was applied and rice straw was removed following harvest. Soil carbon (C) concentrations increased significantly only where higher fertilizer rate and rice stubble retention were combined.The poor management of fertilizers and crop residues, and excessive cultivation has also resulted in large soil fertility losses in the grain growing areas of Eastern Australia. After five wheat and two legume/fallow crops, negative N balances of up to −303 kg ha⁻¹ were calculated for the treatments where wheat stubble was not retained and bare fallow leys were used. The balance of nutrients such as K, which are contained in larger proportions in stubble, were found to be up to −362 kg ha⁻¹ on the straw-removed treatments and up to +29 kg ha⁻¹ on the straw-retained treatments. Forage legume leys resulted in short term increases in C_L and the carbon management index (CMI).Sustainable farming systems require that crop yields are stable through the maintenance of soil fertility and the balance of nutrients in the system. Increases in soil C levels require sustained periods of balanced fertilization and residue retention.     

COMPARISON OF TRACE ELEMENT CONCENTRATIONS IN TISSUE OF COMMON CARP AND IMPLICATIONS FOR MONITORING1

Common carp (Cyprinus carpio) collected from four sites in the Red River of the North in 1994 were analyzed for arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb), nickel (Ni), selenium (So), and zinc (Zn). Concentrations differed among liver, muscle, and whole body. Generally, trace element concentrations were the greatest in livers while concentrations in whole bodies were greater than those in muscle for Cd, Cu, Ni, Pb, and Zn, and concentrations in muscle were similar to whole body for As and Se. Concentrations of Cr were lower in liver than either muscle or whole body. Correlations between liver and whole body concentrations were stronger than those between liver and muscle concentrations, but the strongest correlations were between muscle and whole body concentrations. Examination of tissue concentrations by collection sites suggested that, for a general survey, the whole body may be the most effective matrix to analyze.     

Evaluation of the Contribution of Genetic Research to the Management of the Endangered Plant Zieria prostrata

Abstract: Zieria prostrata (Rutaceae) is known from only four headlands within a 3-km stretch of coastline in New South Wales, Australia. The species was presumed to have occurred at a headland 24 km south of its present range. We used random amplified polymorphic DNA analysis to assess patterns of genetic variation within and among the extant populations. The analysis also included an individual reputedly rescued from the now extinct population. A high level of population divergence was revealed by principal coordinate analysis and an analysis of molecular variance (AMOVA; 37% among populations). Our genetic findings provide implications for the conservation management of the species. First, the loss of any one population would lead to a severe loss of genetic variation. Second, an adequate ex situ collection must sample the full range of genetic diversity from all populations. Third, the consequences of mixing populations may be an important conservation consideration if further translocations proceed. Fourth, the individual apparently sampled prior to its population extinction is genetically similar to individuals from one of the extant sites. This degree of similarity was unexpected and, after further investigation, led to the conclusion that prior existence of the species at the site is doubtful. Subsequently, a planned reintroduction program was abandoned. So far, of these four management implications, only the last has had a direct management outcome. Those implications that failed to lead to practical management outcomes did so because the same management recommendations could be obtained without genetic research. Clearly, the challenge for more effective conservation is to identify those cases in which genetic studies are likely to produce practical outcomes for conservation managers. This may be best achieved by assessing the outcomes of genetic studies already conducted.     

Simulation of mixing depths incorporating the urban heat island effect

The main objective of this paper was to establish the effect of anthropogenic heat flux on the formation of mixing depth specially in urban areas. In this study an energy balance mixing depth model was developed for the simulation of mixing depth incorporating the heat island effect. To demonstrate the effect of heat island, mixing depths were simulated under two conditions. Under the first condition, hourly gridded anthropogenic heat flux and variant surface characteristics were considered, while under the second condition anthropogenic heat flux term was ignored and constant surface characteristics were considered throughout the modelling domain. The release of anthropogenic heat flux in the urban environment was found to be responsible for the growth of the unstable layer in the lower atmosphere even during the night. This resulted in higher mixing depth values in urban areas compared to the surrounding countryside. The maximum differential surfaces sensible heat flux between urban and rural areas was estimated as 130 W/m². From the simulation of mixing depth, it was revealed that the maximum increment in mixing depth in urban areas was 300 m due to the heat island effect. This increment in mixing depth in urban areas can provide an extra space for dilution and mixing of pollutants.     

Policy diffusion in arid Basin water management: a Q method approach in the Murray–Darling Basin,Australia

The Murray–Darling Basin is Australia’s national food bowl, home to almost half of the national income from food production, as well as internationally significant wetlands, iconic red gum forests, endangered flora and fauna, and approximately 40 autonomous indigenous nations. Persistent severe drought and extreme flooding episodes have presented new challenges in the region. Chief among these challenges is the establishment of a legitimate framework to sustainably manage water resources that finds common ground between environmental, indigenous and commercial interests. A powerful approach to examine these processes is through the theory of diffusion and adaptation of policy innovations. Here, we describe an approach to place this theory on empirical ground using Q methodology. We elucidate patterns of subjectivity, to explore the perceptions of expert advice, subsidiarity and local knowledge to better understand the interests in play. We find that respect is held for local practitioners (water managers and farmers) and indigenous knowledge, but while policy innovations are being generated, the diffusion of policy is contested. We identify the potential, though limited, for common ground through substantive and respectful consultation.     

Brake Lining Decomposition Products

A number of investigators have found asbestos bodies in the lungs of urban residents who were not occupationally exposed to asbestos. A relationship between the carinogenic properties of asbestos and the urban excess of lung cancer has been suggested. The decomposition products of brake linings have been described as a possible source of these fibers. Brake testing laboratory methods were used to test fiber emission from a variety of friction products. Only a very small fraction of the asbestos escaped as free fiber while the remainder was transformed into some other, nonfibrous, mineral. A significant release of free fiber occurred only under conditions extreme enough to produce brake failure.     

Declines in migrant shorebird populations from a winter‐quarter perspective

Many long‐distance migrating shorebird (i.e., sandpipers, plovers, flamingos, oystercatchers) populations are declining. Although regular shorebird monitoring programs exist worldwide, most estimates of shorebird population trends and sizes are poor or nonexistent. We built a state‐space model to estimate shorebird population trends. Compared with more commonly used methods of trend estimation, state‐space models are more mechanistic, allow for the separation of observation and state process, and can easily accommodate multivariate time series and nonlinear trends. We fitted the model to count data collected from 1990 to 2013 on 18 common shorebirds at the 2 largest coastal wetlands in southern Africa, Sandwich Harbour (a relatively pristine bay) and Walvis Bay (an international harbor), Namibia. Four of the 12 long‐distance migrant species declined since 1990: Ruddy Turnstone (Arenaria interpres), Little Stint (Calidris minuta), Common Ringed Plover (Charadrius hiaticula), and Red Knot (Calidris canutus). Populations of resident species and short‐distance migrants increased or were stable. Similar patterns at a key South African wetland suggest that shorebird populations migrating to southern Africa are declining in line with the global decline, but local conditions in southern Africa's largest wetlands are not contributing to these declines. State‐space models provide estimates of population levels and trends and could be used widely to improve the current state of water bird estimates.