Gordon Research Conference: Isotopes in Biological and Chemical Sciences, 14–19February 2010, Galveston,TX, USA

The natural flow properties of the Yangtze River have been changed completely following the construction of the Three Gorges Dam. The dam's operation has affected the resources and environment in the middle and lower reaches of the Yangtze River, changing the hydrological conditions and ecological environment of the Dongting Lake. During three different dispatching periods of the reservoir, we took triplicate samples of the river and lake water. All the samples were analysed for δ²H and δ¹⁸O to determine the relationship between the lake and the Yangtze River (and other rivers), and to evaluate objectively the influence of the dam's operation on the lake. During the period of water-supply dispatch, the Four Rivers and Miluo River are the main recharge sources of the lake. During the flood-storage dispatching period, the Dongting Lake is recharged largely by the Three Outlets and the Four Rivers, whereas during the period of water-storage dispatch, most of the lake's water originates from the Miluo, Xiang, Zi, and Yuan rivers. Although the Yangtze River only contributes significantly to the lake's recharge through the Three Outlets during the flood-storage dispatching period, the lake discharges large amounts of water into the Yangtze River during all three periods. Through the operation of the reservoir, it should be ensured that the water level of the Dongting Lake is not too low during the dry season, nor too high during the wet season, thus preventing the lake region from future flood and drought disasters.     

Relationship between water use efficiency (WUE) and production of different wheat genotypes at soil water deficit

Through 2-year field experiments, 7 wheat genotypes were better in their field yield. These 7 wheat genotypes and other 3 wheat species, which are being popularized on a large scale in different locations of China, were selected as experimental materials for the sake of measuring their difference in WUE and production and comparing their relationship at soil water deficits, future more, providing better drought resistance lines and theoretical guide for wheat production and practices and exploring anti-drought physiological mechanisms of different wheat genotypes. Under the condition of 3 soil–water–stress treatments (75% field capacity (FC), 55% FC, 45% FC, named level 1, level 2 and level 3, respectively), pot experiments for them were conducted and the related data were collected from their life circle. The main results were as followed: (1) according to the selected soil stress levels, water use efficiency (WUE) of 10 different wheat genotypes was divided into two groups (A and B); group A included genotypes 2, 3, 4, 5, 6, 7, 8, whose WUE decreased basically from level 1 to level 3 and reached individual peak of WUE at level 1; Group 2 included genotypes 1, 9, 10, whose WUE reached their individual peak at level 2; (2) based on total water consumption through all life circle, genotypes 1, 4, 8, 9 had lower water consumption (TWC) at level 1, genotypes 2, 3, 5, 6, 7 lower TWC at level 2, genotype 10 lower TWC at level 3; (3) at level 1, genotypes 2, 3, 4, 5, 6, 7, 8 had higher grain weight of single spike (GWSS), genotypes 1, 9, 10 better GWSS at level 2, which was in good line with individual WUE of different wheat genotypes; (4) by analyzing the indexes related to examining cultivars, it was found that genotypes 1, 2, 3, 4, 5, 6, 9, 10 had longer plant length (PL), spike length (SL), bigger grain number (GN) except genotypes 7 and 8 at level 1, RL was in better line with genotypes 1, 2, 3, 8, 9, 10, but not in the other genotypes at level 1.     

区域旱情评估模型

旱灾是我国主要的自然灾害之一。不同程度的旱灾所采取的措施和投入将是不同的。认清旱情等级作出相应的对策，对抗旱减灾是十分重要的。本文分析了影响区域旱情的因素并给出了区域旱情评估的模型和实际的应用。     

梭梭幼苗抗旱性与生物自由基,膜伤害关系初探

梭梭幼苗同化枝的相对含水量和束／自比值随着幼苗生长而增加，渗透势与相对电导率却下降．ＳＯＤ在梭梭幼苗同化枝中的定位表明随着幼苗的生长过程各细胞器中ＳＯＤ的活性也在不断变化，但总趋势是随着生长、细胞质和叶绿体中的ＳＯＤ活性以及总ＳＯＤ活性不断增高，只有线粒体中的ＳＯＤ活性呈现下降趋势。另外梭梭种子的ＳＯＤ活性明显高于子叶和幼苗ＭＤＡ和叶绿素含量以及叶绿素ａ／ｂ的值随着生长在不断增高，相反呼吸速率却降低．     

COMBINING SOCIAL CAPITAL AND TECHNOLOGY FOR DROUGHT RESILIENCE IN AGRICULTURE

In water‐scarce regions of the world, water‐saving technology adoption augments farm productivity. But so does social capital. In this paper, the issue of ensuring livelihood for farmers through the combined use of social capital and water‐saving technology is modeled in the context of repeated droughts. The model presented here derives optimal resource conservation and accumulation strategies when the farmer must ensure minimum consumption during a set of repeated drought events in the future. Findings indicate that the path to drought resilience presents a complex trade‐off between accumulating one form of capital over another and is influenced by farmers’ wealth and water endowments, level of risk associated with the repeated droughts and the duration of the repeated drought event that the farmer plans to survive. A higher risk of repeated droughts leads to an increase in groundwater conservation efforts but delays technology adoption. Lower water endowments may also delay adoption and reduce social capital, however, a lower social capital or a slow rate of its growth is not a hindrance to adopting water‐saving technology earlier. Finally, social capital evolves to higher levels when farmer is simultaneously faced with a higher level of risks and a longer span of drought events.     

基于SPEI及游程理论的云贵地区1960-2014年干旱时空变化特征

基于云贵地区49个气象站点1960-2014年的逐月气象数据,计算得到云贵地区季尺度及年尺度的标准化降水蒸散发指数序列,结合游程理论及经验正交（EOF）等方法,揭示云贵地区干旱的时空变化特征.研究结果表明：（1）云贵地区气候呈现逐渐变干的趋势,且年尺度和季尺度在21世纪初均出现由湿转干的迹象.（2）同一干旱历时条件下,不同等级干旱发生的频率不同,等级越小发生频率越高,反之亦然.同一等级的干旱发生频率随干旱历时长度的增加而减小.（3）在历时2~5个月的干旱事件中,云南省的干旱重现期均小于贵州省,即云南省发生干旱事件较贵州省频繁.27°N以北地区的干旱重现期较长,干旱事件发生频率较小.（4）对云贵地区近55 a的SPEI进行经验正交（EOF）分析知,EOF展开第1模态反映的是季风系统控制下的云贵地区旱涝一致性变化情况,21世纪后,云贵地区普遍处于干旱状态;EOF展开第2模态反映的是受乌蒙山阻隔,东西两侧干旱呈现反相位变化的空间分布特征.该研究对于认识和把握区域气候干旱趋势与规律,提高区域干旱预警能力,保证粮食安全和生态经济稳定有重要的现实意义.