Modeling seed dispersal distances: implications for transgenic Pinus taeda.

Predicting forest-tree seed dispersal across a landscape is useful for estimating gene flow from genetically engineered (GE) or transgenic trees. The question of biocontainment has yet to be resolved, although field-trial permits for transgenic forest trees are on the rise. Most current field trials in the United States occur in the Southeast where Pinus taeda L., an indigenous species, is the major timber commodity. Seed dispersal distances were simulated using a model where the major determinants were: (1) forest canopy height at seed release, (2) terminal velocity of the seeds, (3) absolute seed release, and (4) turbulent-flow statistics, all of which were measured or determined within a P. taeda plantation established from seeds collected from wild forest-tree stands at the Duke Forest near Durham, North Carolina, USA. In plantations aged 16 and 25 years our model results showed that most of the seeds fell within local-neighborhood dispersal distances, with estimates ranging from 0.05 to 0.14 km from the source. A fraction of seeds was uplifted above the forest canopy and moved via the long-distance dispersal (LDD) process as far as 11.9-33.7 km. Out of 10(5) seeds produced per hectare per year, roughly 440 seeds were predicted to be uplifted by vertical eddies above the forest canopy and transported via LDD. Of these, 70 seeds/ha traveled distances in excess of 1 km from the source, a distance too great to serve as a biocontainment zone. The probability of LDD occurrence of transgenic conifer seeds at distances exceeding 1 km approached 100%.     

Agricultural policies and the emergence of voluntary landscape enhancement efforts: an exploratory analysis of rural tourism using an agent-based model

Conservation and enhancement of ecosystem services have become a priority of rural policies. Feedback loops from rural policies on ecosystem service supply have often been highlighted in the literature, but only vaguely investigated. In this paper, we model feedback loops from rural policies through an agent-based model, and we analyse whether feedback loops can indirectly create a system in which voluntarily landscape enhancement emerges from the interactions between farmers and rural tourists. The results suggest that, in certain conditions, feedback loops from policies can be a relevant element to take into account, but that greater attention to the ecosystem service demand is required.     

A Bayesian network highlighting the linkages between landscape structure and the local economy: the case of agritourism in lowland areas of Northern Italy

Linking landscapes to socio-economic benefits necessarily requires considering the usability of landscape structure. To do so, however, depends on the interaction between users and producers of landscape-related services. We illustrate this interaction with a Bayesian Belief Network (BBN) in a case study analysing the connection between residents' perceptions of landscape structure and agritourism restaurants in the eastern lowlands of Ferrara (Italy). We use estimates of prior and conditional probabilities from a mix of different data: land use, survey data, regional statistics, and expert judgements to show the likely effects of the landscape structure on the local economy by using intermediate forms of services (i.e. second-order services). The second-order service is highly influenced by the agritourism density and by the frequency with which customers dine at agritourism restaurants and less by landscape attractiveness, confirming the importance of the supply and demand of second-order services in the provision of landscape-related services.     

Implementing the Water Framework Directive: Contract Design and the Cost of Measures to Reduce Nitrogen Pollution from Agriculture

The performance of different policy design strategies is a key issue in evaluating programmes for water quality improvement under the Water Framework Directive (60/2000). This issue is emphasised by information asymmetries between regulator and agents. Using an economic model under asymmetric information, the aim of this paper is to compare the cost-effectiveness of selected methods of designing payments to farmers in order to reduce nitrogen pollution in agriculture. A principal-agent model is used, based on profit functions generated through farm-level linear programming. This allows a comparison of flat rate payments and a menu of contracts developed through mechanism design. The model is tested in an area of Emilia Romagna (Italy) in two policy contexts: Agenda 2000 and the 2003 Common Agricultural Policy (CAP) reform. The results show that different policy design options lead to differences in policy costs as great as 200–400%, with clear advantages for the menu of contracts. However, different policy scenarios may strongly affect such differences. Hence, the paper calls for greater attention to the interplay between CAP scenarios and water quality measures.     

Effect and Control of Pollution in Catchment Area of Lake Sapanca, Turkey

/ Land-based point and diffuse pollution sources in the catchment area of Lake Sapanca, Turkey, were investigated. The present and future distribution of pollution loads were evaluated in terms of nitrogen, phosphorus, biochemical oxygen demand, and pesticides. A methodology for the estimation of pollution loads was presented; most of which were based on "unit loads." Presently domestic and industrial point sources dominate over diffuse sources including fertilizers and pesticides from agricultural use, nutrient loads from forests and meadows, urban runoff, and leachates from unregulated dumps of solid wastes. For the future, the aim of the control action is to maintain the sustainability of the water quality of the lake, at least at the second class of European Community standards. Within this framework; urgent/short-term and medium/long-term control actions will be exercised. In the urgent/short-term stage, simpler and natural ways of treatment will be employed. In the medium/long-term stage an integrated collection and treatment system will be put on operation. After completion of a proposed collection system and treatment plants to handle point sources, the control of diffuse sources will be more significant. Control of diffuse sources for the abatement of further deterioration of water quality then becomes the key issue to be emphasized in the Lake Sapanca catchment area. Diffuse sources control will be achieved by dividing the catchment area into three major protection zones. Use of pesticides and fertilizers on agricultural land and all other activities within these protection zones will be accomplished according to control plans, which will be supervised by an institution established to be responsible of all the activities within the basin.KEY WORDS: Diffuse sources; Land-based pollution; Nutrients; Pesticides; Point sources; Protection zones     

Shielding from ELF Magnetic Fields Emanating from Power Plants in Large Facilities

Summary Large facilities frequently have internal power plants. High power transformers and low voltage cables associated with these plants generate low-frequency magnetic fields of large amplitude, which can be above allowed exposure levels. In order to shield against these magnetic fields large shields are used. These plates are finite and their shielding effectiveness is compromised due to their finite dimensions. This paper evaluates the shielding afforded by such a plate, as related to the geometry of the placement of the source and victim and the dimensions and structure of the shield plate.     

Results of the UNDP (SF)/FAO regional fisheries survey in West Africa. Report no. 4. T/S relationship in the Canary Current area

Based on historical oceanographic data supplied by the National Oceanographic Data Center (NODC), Washington, D.C., USA, temperature salinity (T/S) diagrams were drawn for a large number of one-degree squares within marsden Squares (MS) 074, 038 and the northern half of MS 002. The shelf area of these squares was the area of the Regional Fisheries Survey activities in 1969 and 1970. The aim of the work is to illustrate the different characteristics of the water in the area. It is shown, in a set of diagrams, that the northern part of MS 074 contains nearly pure North Atlantic Central Water (NACW), except for the surface layer, where the characteristics change with season. In the upwelling area of Senegambia, during the upwelling season, the water is of a South Atlantic Central Water (SACW) and NACW mixed type, while in the offshore area it is nearly pure NACW. In the southern part of MS 074 and the northern part of MS 038, the subsurface water is a mixture of NACW and SACW, which changes into pure SACW southwards, but remains a mixture in medium depths. The SACW is always superimposed on the NACW. Inshore, the water mass changes with season. During the rainy season this is Liberian surface water of low salinity and high temperature. In MS 002, to the south, offshore, the subsurface water becomes pure SACW, which in deep parts overlays the Antarctic Water. Inshore at the surface, the water is desalinated during the rainy season. The Liberian surface water spreads over the whole of MS 002, nearly 1000 miles offshore.     

Results of the UNDP(SF)/FAO Regional Fisheries Survey in West africa. Report no 3. Silicates in the Canary Current area

The Canary Current region off West Africa was examined for its temperature, salinity and dissolved oxygen relations. When historical data on dissolved silicate were examined in the same area, it was found that the area of intensive upwelling has the least amounts of silicate compared with adjacent regions.