APPLICATION OF TABU SEARCH TO GROUND WATER PARAMETER ZONATION1

ABSTRACT: The spatial distribution of hydrogeologic parameter is an important issue in ground water simulation. One of the methods is to divide an area into several zones such that parameters are assumed to be constant within zone. The purpose of this study is to apply Tabu Search (TS) to find the best zonation of parameters that can result in the best ground water simulation. The initial zonation can be determined as the Thiessen method, and then zonation is optimized by T.S. The mean square error between simulated and observed hydraulic heads was used as the objective function. A designed confined aquifer with known zonation was used as an example to test the proposed method. Results indicated that Tabu Search can locate the optimal zonation successfully and avoid being trapped by local optimal zonations. Besides this, four other arbitrary initial zonations can be directed to the optimal zonation by TS, which proves the robustness of the proposed method. The method proposed in this study is feasible and expected to work well in the field problems with sufficient sampling of concerned parameters.     

Ability of Matrix Models to Explain the Past and Predict the Future of Plant Populations

Uncertainty associated with ecological forecasts has long been recognized, but forecast accuracy is rarely quantified. We evaluated how well data on 82 populations of 20 species of plants spanning 3 continents explained and predicted plant population dynamics. We parameterized stage‐based matrix models with demographic data from individually marked plants and determined how well these models forecast population sizes observed at least 5 years into the future. Simple demographic models forecasted population dynamics poorly; only 40% of observed population sizes fell within our forecasts’ 95% confidence limits. However, these models explained population dynamics during the years in which data were collected; observed changes in population size during the data‐collection period were strongly positively correlated with population growth rate. Thus, these models are at least a sound way to quantify population status. Poor forecasts were not associated with the number of individual plants or years of data. We tested whether vital rates were density dependent and found both positive and negative density dependence. However, density dependence was not associated with forecast error. Forecast error was significantly associated with environmental differences between the data collection and forecast periods. To forecast population fates, more detailed models, such as those that project how environments are likely to change and how these changes will affect population dynamics, may be needed. Such detailed models are not always feasible. Thus, it may be wiser to make risk‐averse decisions than to expect precise forecasts from models. Habilidad de los Modelos Matriciales para Explicar el Pasado y Predecir el Futuro de las Poblaciones de Plantas     

Fate of 14C‐lindane in a rice‐fish model ecosystem*

Abstract

A model ecosystem has been used to evaluate the impact of ¹⁴C‐lindane on rice‐fish agricultural system. The distribution of ¹⁴C‐residues among the constituents of the model ecosystem was studied over a period of 90 days. The insecticide was found to be readily absorbed by the roots and translocated to all parts of the rice plant. The peak level in the shoots (26 ppm) and roots (105 ppm) of plants was reached to within three weeks. Lindane was concentrated in fish and residues as high as 90 ppm could be detected after 30 days.

The major part of the residues present in the different constituents of the ecosystem could be extracted with hexane and proved to contain soley the parent compound. The data obtained show that lindane possesses a relatively low biodegradability in fish and in rice plant. The insecticide accumulates in fish and rice plant to considerable extent.     

Building disaster‐resilient micro enterprises in the developing world

Family‐owned micro enterprises operating within the informal sector of most developing countries provide millions of citizens with a livelihood and are the economic backbone of many communities. Yet, the turbulence that emanates up or down respective supply chains following a disaster can cause these entities to fail. This study develops a model that recognises the relative weakness of micro enterprises to such disaster‐related shocks. The model proposes that micro enterprises can moderate the effect of such shocks by creating resilience through cognitive preparation, continuous learning, and the generation of various forms of social capital (cognitive, relational, and structural). The propositions for the model are established through an extensive literature review, coupled with examples drawn from the documents of humanitarian agencies performing disaster relief work in India. This model also serves as a preliminary basis with which to derive metrics to set benchmarks or to assess the viability of a micro enterprise's ability to survive disaster‐related shocks.     

Two‐Stage Recovery of Amphibian Assemblages Following Selective Logging of Tropical Forests

There is a lack of quantitative information on the effectiveness of selective‐logging practices in ameliorating effects of logging on faunal communities. We conducted a large‐scale replicated field study in 3 selectively logged moist semideciduous forests in West Africa at varying times after timber extraction to assess post logging effects on amphibian assemblages. Specifically, we assessed whether the diversity, abundance, and assemblage composition of amphibians changed over time for forest‐dependent species and those tolerant of forest disturbance. In 2009, we sampled amphibians in 3 forests (total of 48 study plots, each 2 ha) in southwestern Ghana. In each forest, we established plots in undisturbed forest, recently logged forest, and forest logged 10 and 20 years previously. Logging intensity was constant across sites with 3 trees/ha removed. Recently logged forests supported substantially more species than unlogged forests. This was due to an influx of disturbance‐tolerant species after logging. Simultaneously Simpson's index decreased, with increased in dominance of a few species. As time since logging increased richness of disturbance‐tolerant species decreased until 10 years after logging when their composition was indistinguishable from unlogged forests. Simpson's index increased with time since logging and was indistinguishable from unlogged forest 20 years after logging. Forest specialists decreased after logging and recovered slowly. However, after 20 years amphibian assemblages had returned to a state indistinguishable from that of undisturbed forest in both abundance and composition. These results demonstrate that even with low‐intensity logging (≤3 trees/ha) a minimum 20‐year rotation of logging is required for effective conservation of amphibian assemblages in moist semideciduous forests. Furthermore, remnant patches of intact forests retained in the landscape and the presence of permanent brooks may aid in the effective recovery of amphibian assemblages. Recuperación de Ensambles de Anfibios en Dos Etapas Después de la Tala Selectiva de Bosques Tropicales     

Integrating Large Wood Jams into Hydraulic Models: Evaluating a Porous Plate Modeling Method

Large wood (LW) jams are key riverine habitat features that affect hydraulic processes and aquatic habitat. The hydraulic influence of LW jams is poorly understood due to the complexity of fluid dynamics around irregular, porous structures. Here we validated a method for two‐dimensional hydraulic modeling of porous LW jams using the open‐source modeling software Delft3D‐FLOW. We sampled 19 LW jams at three reaches across the Columbia River Basin in the United States. We used computer‐generated porous plates to represent LW jams in the modeling software and calibrated our modeling method by comparing model outputs to measured depths and velocities at validation points. We found that modeling outputs are error‐prone when LW jams are not represented. By representing LW jams as porous plates we reduced average velocity root mean square error (RMSE) values (i.e., improved model accuracy) by 42.8% and reduced average depth RMSE values by 5.2%. These differences impacted habitat suitability index modeling. We found a 15.1% increase in weighted useable area for juvenile steelhead at one test site when LW jams were simulated vs. when they were ignored. We investigated patterns in average RMSE improvements with varying jam size, bankfull obstruction, porosity, and structure type, and river complexity. We also identified research gaps related to field estimation of LW jam porosity and porous structure modeling methods.     

Chemical characterization of a water soluble fraction (WSF) of crude oil

Very polar oil compounds are predominant in the resulting water soluble fraction (WSF) of crude oil, in agreement with their high solubility in seawater. Non‐volatile hydrocarbons represent only a low proportion of total soluble extracts.

The experimental process we have achieved allows us to obtain quantitative and reproducible soluble oil extracts that could be used in ecotoxicological tests and for the study and the characterization of marine oil pollution.     

Land‐use trade‐offs between tree biodiversity and crop production in the Atlantic Forest

Trade‐offs in ecosystem services (ES) have received increasing attention because provisioning services often come at the expense of biodiversity loss. When land‐use patterns are not maximally efficient relative to productivity, provisioning services, such as crop production, can often be increased without losing biodiversity. The Atlantic Forest (AF) encompasses dense, mixed, and seasonal forests and has high levels of endemism and anthropogenic threat. We examined trade‐offs between biodiversity and crop production in the AF to provide insights into land‐use management decisions. We developed a biodiversity metric that combines information on tree species richness, evolutionary distinctiveness, and rarity at the local level. We examined the extent to which the nature of ES trade‐offs differ among the 3 forest types. We assessed how annual deforestation rates and land management practices affect biodiversity and agricultural revenues. Finally, we tested whether it is possible to achieve the same total regional revenue without reducing biodiversity by improving local management practices. The 3 forest types had similar patterns in ES trade‐offs, although within mixed forest patterns differed. Biodiversity appeared to be more sensitive to land‐use change than crop revenues. Certain crops yielded up to 10 times higher values in some sites. Enhanced crop productivity may increase revenues without reducing biodiversity. Our results showed that to enhance human well‐being without further conversion of AF, maximizing crop productivity is needed . Increasing efficiency of management outcomes by maintaining higher biodiversity and increasing provisioning services depends on knowledge of forest type, the comparative advantage of planting crops in the best places, and preserving species in a balanced manner across forests.