基于改性糯米灰浆的3种锚杆锚固性能对比研究

锚固浆液的类型及其与杆体、土体的兼容协调性问题是土遗址锚固领域的研究焦点。由糯米浆为胶凝主材和由黏土、粉煤灰为填充料组成的改性糯米灰浆与木锚杆、玻璃纤维增强塑料锚杆、钢筋锚杆组成了3种锚固系统。通过对3种锚固系统的原位锚固、拉拔试验和界面应力-应变监测,分析比较了3种锚固系统的破坏模式、极限荷载、荷载-位移特征,剖析了杆体-浆体界面应力分布传递规律和界面测点应变对荷载时步的响应程度。在初步分析其锚固机制的基础上,最终得出了此类基于改性糯米灰浆的3种锚固系统的锚固性能的优劣完全取决于杆体-浆体的受力机制、变形和强度特征所决定的力学兼容性的结论。该研究成果为以糯米浆为主材的改性浆液在土遗址锚固领域中的应用提供了依据和参考。     

潮湿环境中稻草的防腐效果及极限拉伸性能

滨海盐渍土存在盐胀、溶陷和吸湿软化等问题,需对其进行处理。设想使用高分子材料SH胶防腐处理稻草,以防腐后的稻草加筋滨海盐渍土。为评价浸胶稻草的防腐效果及其力学性能,测试了天然和浸泡SH胶稻草的吸水率,及天然、浸水、浸胶及浸胶后再浸海水稻草的极限拉力和极限延伸率。结果表明：（1）浸胶稻草与天然稻草相比,吸水率最多可降低50%,证实防腐效果较好;（2）浸胶后,稻草的极限延伸率和极限拉力最大提高了26%和23%;（3）同是浸泡在海水中,浸胶后稻草较天然稻草,其极限延伸率和极限拉力的最大增长率为12%和11%;（4）浸胶稻草的SEM照片观察及能谱分析表明,SH胶包裹了纤维并进入到稻草的孔隙中,增强了纤维间的联结,提高了稻草的极限抗拉性能。SH胶防腐后的稻草作为加筋材料是可行的。     

Agrobiodiversity of Muda Rice Agroecosystem:A case Study in Largest Granary Area of Malaysia

A survey was carried out at the largest rice cultivation area in Peninsular Malaysia,the Muda rice agroecosystem.The main objective of this study was to document the overall biodiversity associated with this unique agroecosystem by using a combination of sampling techniques in order to record different groups of fauna and flora.The total number of biota recorded and identified from the rice field ecosystem during the study period consisted of 46 species of zooplankton,81 species of aquatic insects,5 species of rodents,7 species of bats,87 species of birds,11 species of fishes and 58 species of weeds.A long-term study should be carried out as more species are expected to be recorded when more of the Muda rice agroecosystem area has been sampled to obtain sufficient information on the Muda rice agrobiodiversity.     

Consensus maps of cloned plant cuticle genes

Plant cuticle,which covers the plant surface,consists of waxes and cutins,and is associated with plant drought,cold,and salt resistance.Hitherto,at least 47 genes participating in the formation of plant cuticle have been cloned from Arabidopsis thaliana,Oryza sativa,Zea mays,Ricinus communis,Brassica napus,and Medicago truncatula;and about 85% of them encode proteins sharing above 50% identities with their rice homologous sequences.These cloned cuticle genes were mapped in silico on different chromosomes of rice and Arabidopsis,respectively.The mapping results revealed that plant cuticle genes were not evenly distributed in both genomes.About 40% of the mapped cuticle genes were located on chromosome 1 in Arabidopsis,while 20% of the mapped cuticle genes were located on chromosome 2 but none on chromosome 12 in rice.Some cloned plant cuticle genes have several rice homologous sequences,which might be produced by chromosomal segment duplication.The consensus map of cloned plant cuticle genes will provide important clues for the selection of candidate genes in a positional cloning of an unknown cuticle gene in plants.     

Percolation losses in paddy fields with a dynamic soil structure: model development and applications

The hydraulic characteristics of the plough pan of paddy fields provide continuous ponding conditions during the growing season and control the water use efficiency in wet rice production. Its saturated hydraulic conductivity K_s, however, exhibits a large spatiotemporal variability as a consequence of a highly dynamic soil structure involving temporary shrinkage cracks. Water flow through the earthen bunds surrounding the fields further contributes to the uncertainty in water flux calculations. The objective of this study was to develop a simple deterministic model with stochastic elements (‘PADDY‐FLUX’) for depiction of deep percolation, and to assess the effect of different water management scenarios on percolation in two channel command areas. Darcy's law is used as the fundamental equation for water flow calculations with the ponding water depth h as a time‐dependent variable. Flux uncertainty is estimated by a Monte‐Carlo‐type implementation. K_s is treated as a random variable of a bimodal probability density function (PDF), which is the weighted sum of two Gaussian PDFs (accounting for a matrix and a preferential flow domain). The weighing factor α is a function of h, reflecting an increasing risk for preferential flow situations after desiccation and the development of shrinkage cracks. Under‐bund percolation is calculated using transfer functions. The results demonstrate that percolation losses increase in the following order: continuous soil saturation < continuous flooding (CF) < mid‐season drainage and intermittent irrigation (MD + II) < mid‐season drainage and continuous flooding. The bunds contribute up to 54 and 17% to total fluxes under CF and MD + II, respectively. Preferential water fluxes are responsible for the major part of water losses as soon as desiccation causes the formation of shrinkage cracks. As a conclusion, continuous soil saturation should be promoted as the least water‐intensive irrigation regime, while intermittent irrigation is recommended only in case that irreversible shrinkage cracks have already developed. Copyright © 2010 John Wiley & Sons, Ltd.     

中国南方调整水稻种植格局——一种水稻生产预先适应气候变化的选择(英文)

Rice planted in southern China accounts for 94% of the total in sown acreage and 88% of the total in production, which matters a lot to Chinese food security. However, due to the prolonged conflict between water availability and rice growth in spatial/temporal distribu-tion, rice production suffers from seasonal drought at acreage of 16%-22%, which compro-mises food production capacity and food security. Focusing on the spatial distribution of seasonal drought with rice and the practices to adapt to it, and based on an analysis of bal-anced water supply for and demand by rice at a growing season scale during 1981-2030, this paper assesses the changing seasonal drought in the process of rice production under the changing climate in the future, and identifies general rice re-cultivation options for climate change adaptation. Some conclusions can be drawn as follows. (1) Rice suggests a decline in seasonal drought, with early season rice (early rice hereafter) by 12,500 km2, middle season rice (middle rice) by 80,000 km2, and in particular late season rice (late rice) by 25,000 km2, which accounts for almost 20% of its cultivated acreage. It is indicated that due to climate change, seasonal drought in major rice producing areas tends to alleviate in general, late season rice in particular. (2) Future climate change brings about a significant impact on the spatial/temporal distribution of water resources in rice producing areas in China. Based on ’pre-designed’ adaptation actions for rice-re-cultivation, the rice cultivation pattern undergoes a significant alteration between 1981-2000 and 2001-2030. In eastern Guizhou and western Hunan, the pattern of single early plus single dry farming is changed into double cropping. In eastern Hunan, the pattern of dry cropping is changed into single early plus single dry farming. In northern Anhui, the pattern of dry farming cropping is changed into middle rice. All this is aimed at a potential adequate availability of water for rice production in the future. (3) Rice re-cultivation patterns developed in this paper help re-balance water demand and supply for rice growth using the spatial analysis tool to adapt rice growth to the changing water avail-ability from spatial perspective, and come up with rice producer-friendly re-cultivation options in response to climate change.     

Change analysis of rice area and production in China during the past three decades

Rice＇s spatial-temporal distributions, which are critical for agricultural, environ- mental and food security research, are affected by natural conditions as well as socio-eco- nomic developments. Based on multi-source data, an effective model named the Spatial Production Allocation Model （SPAM） which integrates arable land distribution, administrative unit statistics of crop data, agricultural irrigation data and crop suitability data, was used to get a series of spatial distributions of rice area and production with 10-km pixels at a national scale -it was applied from the early 1980s onwards and used to analyze the pattern of spatial and temporal changes. The results show that significant changes occurred in rice in China during 1980-2010. Overall, more than 50% of the rice area decreased, while nearly 70% of rice production increased in the change region during 1980-2010. Spatially, most of the increased area and production were in Northeast China, especially, in Jilin and Heilongjiang; most of the decreased area and production were located in Southeast China, especially, in regions of rapidly urbanization in Guangdong, Fujian and Zhejiang. Thus, the centroid of rice area was moved northeast approximately 230 km since 1980, and rice production about 320 km, which means rice production moved northeastward faster than rice area because of the significant rice yield increase in Northeast China. The results also show that rice area change had a decisive impact on rice production change. About 54.5% of the increase in rice pro- duction is due to the expansion of sown area, while around 83.2% of the decrease in rice production is due to contraction of rice area. This implies that rice production increase may be due to area expansion and other non-area factors, but reduced rice production could largely be attributed to rice area decrease.     

Ancient dams,settlement archaeology and Buddhist propagation in central India: the hydrological background

Abstract

A group of ancient dams (c. second—first century BC) was located during an archaeological study of the Sanchi area in central India. Comparison of reservoir volumes with estimated inflows suggests that their design was based on hydrological understanding.     

水稻籽实及其根系土壤中镉含量的相关性研究——以几个金土地工程土地整理区为例

通过对水稻籽实（大米）及其根系土壤中镉含量的相关性研究表明：酸性水稻土壤区域,根系土中的镉与水稻籽实中的镉相关系数为0．971,说明大米中镉积累与土壤环境中镉含量密切相关。碱性水稻土壤区域,水稻根系土中的镉与水稻籽实中的镉相关系数为0．265,大米中镉含量较低,碱性土壤中镉不易活化而原地淀积,则根系土壤中镉对大米中镉的富集贡献小。水稻根系土壤中有机质（Org）与镉相关系数为0．59,也较为显著。土壤中有机质对重金属元素镉具正吸附作用,有机质含量越高,重金属元素镉呈难吝硫化物而原地淀积。