A spatial analysis of factors influencing farmland conversion in the Bangkok metropolitan area, Thailand

Agricultural land conversion is a complex process that involves a matrix of decisions and decision-makers. This study examines the nature and relative significance of spatial factors that influence the decisions of farmers who either sell farmland to developers for urban use or retain it for agricultural use. The conceptual model views farmers as boundedly rational individuals who seek satisfying economic and noneconomic returns from land. Their decisions are influenced by urban-generated factors that reflect land demand, by agricultural factors that determine the economic viability of agriculture under urban influences as well as by the decision-makers' characteristics. The study is done within the political and socioeconomic context of Bangkok, Thailand. The Thonburi region of the Bangkok Metropolitan Area is chosen as an example of a land use transition zone experiencing various urbanization pressures. Aerial photography is used to establish the location and magnitude of agricultural to urban land conversion between 1967 and 1983. Data from land use maps constructed from the air photo base maps and data from the Agricultural Census are used to test the research hypotheses of the study. The two primary research questions are: 1) Are the farmers' decisions to hold or to sell land related to urbanization pressures, economic viability of agriculture and farmers' characteristics?; and 2) What is the relative significance of these factors in influencing land conversion? Bivariate correlation and multiple regression analyses reveal the significant relationships of farmland conversion and the following variables: accessibility of land parcels, level of agricultural investment, age, education and occupational status. The dominant explanatory variables are the proximity to community centers and major roads. Secondary to them are the roles of farmers' age, education level and investment in irrigation. The effects of the other decision-maker's characteristics and agricultural variables are marginal but statistically significant. The study provides insight into the roles of agricultural viability as well as urban demand factors and decision-maker's characteristics in influencing the pace of land conversion in the developing country

Effect of paclobutrazol on three different aquatic macrophytes under in vitro monoculture or polyculture conditions

Three aquatic plants, coontail (Ceratophyllum demersum L.), hydrilla [Hydrilla verticillata (L. f.) Royle] and giant duckweed [Spirodela polyrhiza (L.) Schleiden], were successfully surface sterilized and cultured on liquid basal MS (Murashige and Skoog, 1962) medium under aseptic conditions. Shoot explants obtained from these plants were transferred to basal MS medium supplemented with 0, 0.25 and 0.5 mg/l paclobutrazol (PBZ) under in vitro monoculture or polyculture conditions. There were some differences in the patterns of fresh weight increases of the three aquatic plants under monoculture and polyculture conditions. Among the three macrophytes studied, coontail was the most sensitive to 0.25 or 0.5 mg/l PBZ as its fresh weights did not increase at these PBZ concentrations during eight weeks under both monoculture and polyculture conditions. Giant duckweed were relatively more sensitive than hydrilla in response to addition of PBZ to the growth medium under both monoculture or polyculture conditions suggesting that PBZ might not be an effective aquatic pest control agent for hydrilla. The dominance of giant duckweed over hydrilla was effectively overturned with the addition of 0.5 mg/l PBZ to the polyculture medium.Keywords: Aquatic plants, coontail, giant duckweed, hydrilla, plant growth retardant.African Journal of Biotechnology Vol. 12(39), pp. 5809-581

Rural–Urban Migration and Experience of Childhood Abuse in the Young Thai Population

Evidence suggests that certain migrant populations are at increased risk of abusive behaviors. It is unclear whether this may also apply to Thai rural–urban migrants, who may experience higher levels of psychosocial adversities than the population at large. The study aims to examine the association between migration status and the history of childhood sexual, physical, and emotional abuse among young Thai people in an urban community. A population-based cross-sectional survey was conducted in Northern Bangkok on a representative sample of 1052 young residents, aged 16–25 years. Data were obtained concerning: 1) exposures—migration (defined as an occasion when a young person, born in a more rural area moves for the first time into Greater Bangkok) and age at migration. 2) outcomes—child abuse experiences were assessed with an anonymous self report adapted from the Conflict Tactics Scales (CTS). There were 8.4%. 16.6% and 56.0% reporting sexual, physical, and emotional abuse, respectively. Forty six percent of adolescents had migrated from rural areas to Bangkok, mostly independently at the age of 15 or after to seek work. Although there were trends towards higher prevalences of the three categories of abuse among early migrants, who moved to Bangkok before the age of 15, being early migrants was independently associated with experiences of physical abuse (OR 1.9 95%CI 1.1–3.2) and emotional abuse (OR 2.0, 95%CI 1.3–3.0) only. Our results suggest that rural–urban migration at an early age may place children at higher risk of physical and emotional abuse. This may have policy implications for the prevention of childhood abuse particularly among young people on the move

Response to Comment on “Plant diversity increases with the strength of negative density dependence at the global scale”

Hülsmann and Hartig suggest that ecological mechanisms other than specialized natural enemies or intraspecific competition contribute to our estimates of conspecific negative density dependence (CNDD). To address their concern, we show that our results are not the result of a methodological artifact and present a null-model analysis that demonstrates that our original findings—(i) stronger CNDD at tropical relative to temperate latitudes and (ii) a latitudinal shift in the relationship between CNDD and species abundance—persist even after controlling for other processes that might influence spatial relationships between adults and recruits