Cost sharing and sustainability of Pongsak Muang Fai irrigation system

The centuries-old, self-organizing Muang Fai community irrigation institution in northern Thailand has high potential in illustrating exemplary practices in irrigation cost sharing. This paper examines the cost sharing structure of the Pongsak Muang Fai Irrigation System in Mae Hong Son Province and its relationship with the system water management and sustainability. Results show that this primitive and high cost system accepts costs of the weir, the entire length of main ditch, not only the individually related ditch sections, and the management as common costs that should be equally shared so that it can gather sizeable membership to support the system. The capacity of this small scale run-of-the-river irrigation system with no river flow limitation is a simple summation of all determined farm intake capacities. The maintenance cost of the system every year depends on how much water should be diverted and conveyed, hence the use of “relative” scale of each farm intake capacity as the basis for sharing cost in the wet season paddy farming. Such structure is directly related to the water management under which every intake shall be served with continuous supply without permitting mid-canal water check-up and the members prefer to take collective action to keep enough water supply without leaving any room for suspicion of unfair water distribution. The direct relationship makes the members understand the purpose of payment and be willing to share the costs which are transparently estimated in easily understood terms and clearly de-aggregated into categories.     

Use of GIS and remote sensing for soil mapping and for locating new sites for permanent cropland — A case study in the “highlands” of northern Thailand

Until a few decades ago, the highlands of northern Thailand were predominantly under forest. Since then, a growing pressure on the land, partly from hill tribes living in the highlands, has led to rapid deforestation and land degradation. To counteract these problems, the Royal Thai Government started a “Highland Development Project” in 1990. Activities of this project include soil inventories and the use of soil and other data to locate new sites for cropland and settlements for hill tribes. In this paper, a case study is described in which the use of a Geographic Information System (GIS) and digital remote sensing methods is compared with the methods currently used in these activities. The GIS is used for the preparation of a terrain mapping unit (TMU) map which integrates data from existing maps and data interpreted from satellite images. The GIS is also used (i) to derive relevant information from the TMU/soil map (e.g. land suitability and estimated erosion rates) and (ii) to integrate this information with land cover/use and accessibility information. This integrated information is used to locate physically suitable, accessible and not yet used areas that could become potential new cropland sites for highland people after resettlement.

A comparison between the currently used methods and the GIS methods shows that apart from considerable time savings, also improvements in data quality are achieved, e.g. by the preparation of a slope map based on a digital terrain model and by up-dating of existing land use information with satellite imagery. The spatial and attribute data base in the GIS makes it possible to use the original, non-aggregated data and, in addition, facilitates the integration of the various data for the analysis of potential sites for resettlement according to various criteria and objectives.     

Morphological and Anatomical Assessment of KDML 105 (Oryza sativa L.spp.indica) and Its Mutants Induced by Low-Energy Ion Beam

Thai jasmine rice KDML 105 is consumed around the world.BKOS,PKOS and TKOS are new cultivars produced from low-energy ion beam induction in KDML 105.The purpose of this study is to compare the morphology and anatomy between KDML 105 and the three new cultivars.Seeds of the four cultivars were germinated and grown in pots until flowering phase.The plants’ organs were observed and the lengths of culms,ligules,leaves and panicles were measured.Leaf surface area was calculated and numbers of roots,spikelets and tillers were counted.BKOS and PKOS had significantly shorter culms than KDML 105 and TKOS.The largest leaf area was found in KDML 105 followed by TKOS,BKOS and PKOS,respectively.Numbers of roots and tillers in BKOS and TKOS were significantly fewer than those in KDML 105 and PKOS.The number of spikelets per plant in BKOS was the lowest among all cultivars.For anatomical comparison,cross sections of culms and roots were observed.All plants had a similar arrangement of tissues,but the number and size of cells were different.Furthermore,longitudinal sections of culms showed that the lengths of epidermal and parenchyma cells were directly related with the length of the culm.To compare the leaves,both stomata and epidermal cells were counted and the lengths of the guard cells were measured.The lengths of guard cells of BKOS and PKOS were shorter,but the stomatal density and the stomatal index were significantly greater than those of KDML 105.For TKOS,though the length of guard cells was shorter than that in KDML 105,the difference was not significant.However,the stomatal density and stomatal index were significantly higher than those in KDML 105.     

Nonrandom processes maintain diversity in tropical forests

An ecological community's species diversity tends to erode through time as a result of stochastic extinction, competitive exclusion, and unstable host-enemy dynamics. This erosion of diversity can be prevented over the short term if recruits are highly diverse as a result of preferential recruitment of rare species or, alternatively, if rare species survive preferentially, which increases diversity as the ages of the individuals increase. Here, we present census data from seven New and Old World tropical forest dynamics plots that all show the latter pattern. Within local areas, the trees that survived were as a group more diverse than those that were recruited or those that died. The larger (and therefore on average older) survivors were more diverse within local areas than the smaller survivors. When species were rare in a local area, they had a higher survival rate than when they were common, resulting in enrichment for rare species and increasing diversity with age and size class in these complex ecosystems.     

The importance of demographic niches to tree diversity

Most ecological hypotheses about species coexistence hinge on species differences, but quantifying trait differences across species in diverse communities is often unfeasible. We examined the variation of demographic traits using a global tropical forest data set covering 4500 species in 10 large-scale tree inventories. With a hierarchical Bayesian approach, we quantified the distribution of mortality and growth rates of all tree species at each site. This allowed us to test the prediction that demographic differences facilitate species richness, as suggested by the theory that a tradeoff between high growth and high survival allows species to coexist. Contrary to the prediction, the most diverse forests had the least demographic variation. Although demographic differences may foster coexistence, they do not explain any of the 16-fold variation in tree species richness observed across the tropics.