2010年6月初广西一次极端暴雨特征分析

利用NCEP1°×1°再分析资料、常规观测资料、自动雨量站加密资料及卫星资料,对2010年6月初广西来宾、都安极端暴雨过程的环流背景和中尺度系统进行了分析。结果表明,此次暴雨过程前无急流建立,850 hPa2支气流在暴雨前明显加强。过程中副高北抬,利于降水系统长时间停留在桂中桂北一带。特大暴雨区位于广西θse线相对密集区及拐点上,具备了高温高湿的不稳定条件。强降水发生在云顶亮温TBB低值中心及TBB等值线密集区,且常发生在不断激发出的中β、γ云团中,小时雨量与TBB分布有较好的对应关系。     

2010年铁岭地区一次暴雨过程诊断分析

采用常规资料、多普勒雷达资料、自动站资料,对2010年8月19～22日铁岭地区出现的暴雨到大暴雨天气过程进行诊断分析。结果表明,受高空槽、副热带高压后部深厚的暖湿气流和切变线共同影响,铁岭地区出现了暴雨到大暴雨天气;这次过程主要影响系统是地面气旋倒槽;700和850 hPa切变线、急流使中低层辐合加强,形成了较强的动力抬升和水汽辐合;铁岭地区处于强而宽的假相当位温锋区中,位势不稳定的建立是造成此次强降水的必要条件。     

亚热带丘岗区生态系统水分平衡及农业反应

通过对自然集雨区水分动态10年定位观测研究,初步明确了我国亚热带丘岗区生态系统水资源的分布特征与水平衡状况。该区域雨水丰沛,总量可维持系统水分平衡,但其时空变化大,加之蒸发变化与之错位和土壤持蓄水分性能差等因素作用,导致系统水分盈亏现象发生,水分“高盈期”的湿害和“亏缺期”的伏旱严重制约了丘岗区农业的发展。强化工程、农艺措施调控能力,提高农业水资源管理水平,是促进我国亚热带丘岗区农业持续稳定发展的技术保障。     

亚热带平原区填闲种植冬性牧草的研究（初报）

1992～1993年在四川眉山县东部，亚热带平原区进行镇闲种植冬性牧草及其与水稻短期轮作的研究。结果表明，紫云英＋南苜蓿→水稻、饲用蚕豆+紫云英→水稻、紫云英＋饲用油菜→水稻及南苜蓿→水稻等四个处理，在获得较高词料价值（TDOM3．29～4．18t／ha，CP1．02～1．32t／ha，ME2．51～3．04×104MJ／ha）的同时，其水稻产量比对照高12．6～18．0％。混播冬性一年生禾草和豆草与水稻轮作，即意大利黑麦草＋紫云英→水稻、意大利黑麦草＋南苜蓿→水稻和意大利黑麦草＋绒毛野豌豆→水稻三个处理获得了更高的饲料价值（TDOM3．90～4．17t／ha，CP1．13～1．17t／ha，ME2．86～3．04×104MJ／ha），禾草和豆草之间产生了良好的营养互补作用，其后作水稻产量的差异不显著。前四种轮作方式适合于以生产粮食和饲养非反刍动物为主的广大农户，后三种轮作方式更适合于以饲养反刍和其他草食动物的专业户。     

Agroforestry potential in the southeastern United States: perceptions of landowners and extension professionals

The first steps in developing an agroforestry extension and training program involve compilation, synthesis, and analysis of current knowledge on existing practices. Equally important is to understand the perceptions of landowners and professionals of agroforestry as a land use option. No systematic effort has been made to assess these critical issues in the southeastern United States. Therefore, needs assessment surveys were developed following an analysis of major demographic issues that frame land use in the region and synthesis of information obtained from informal site visits and interviews with people engaged in resource and land use in the Atlantic and Gulf Coastal Plain. Surveys of extension professionals and landowners were then undertaken in the states of Alabama, Florida, and Georgia to represent the southeastern region. In addition to getting insights into the perceived benefits and concerns about agroforestry practices, the surveys indicated that the extent of alley cropping, forest farming and silvopasture practiced by landowners was less than anticipated, and that the prominence of windbreaks was overlooked by professionals. Managed riparian forest buffers or streamside management zones and windbreak technologies were the most widely used forms of agroforestry in the study area, although landowners did not recognize influence of agroforestry practices on quality or quantity of water among benefits of highest importance to them. Multistrata patio- or home gardens were also a prominent landowner-practice and acknowledged by professionals. These survey results can be useful for developing a relevant agroforestry extension and training program in the subtropical Southeast and may be of interest to agroforestry efforts in other similar settings. This revised version was published online in August 2006 with corrections to the Cover Date.     

加强宣传工作 提升南亚所形象

新闻宣传工作是中国热带农业科学院南亚热带作物研究所(以下简称南亚所)建设和发展的重要工作之一。阐述了南亚所宣传工作的现状、个人新闻采写工作体会及如何创新南亚所宣传工作机制，并进一步探讨如何做好新闻宣传工作。     

亚热带森林凋落物产量及动态的研究

本文是广西森林生态定位研究工作的一部分,旨在研究、弄清不同森林凋落物的数量和质量、组成和动态及其与森林组成、树种特性、年龄结构、空间结构、生长状况及环境因子间的相互关系,为分析森林群落的生产力、研究森林群落的养分循环和制定营林措施提供理论依据。一、自然环境和样地概况研究工作在广西龙胜、岑溪、宜山三个森林生态定位站进行(表1)。研究的森林类型     

Above- and belowground carbon inputs affect seasonal variations of soil microbial biomass in a subtropical monsoon forest of southwest China

Soil microbial activity drives carbon and nutrient cycling in terrestrial ecosystems. Soil microbial biomass is commonly limited by environmental factors and soil carbon availability. We employed plant litter removal, root trenching and stem-girdling treatments to examine the effects of environmental factors, above- and belowground carbon inputs on soil microbial C in a subtropical monsoon forest in southwest China. During the experimental period from July 2006 through April 2007, 2 years after initiation of the treatments, microbial biomass C in the humus layer did not vary with seasonal changes in soil temperature or water content. Mineral soil microbial C decreased throughout the experimental period and varied with soil temperature and water content. Litter removal reduced mineral soil microbial C by 19.0% in the ungirdled plots, but only 4.0% in girdled plots. Root trenching, stem girdling and their interactions influenced microbial C in humus layer. Neither root trenching nor girdling significantly influenced mineral soil microbial C. Mineral soil microbial C correlated with following-month plant litterfall in control plots, but these correlations were not observed in root-trenching plots or girdling plots. Our results suggest that belowground carbon retranslocated from shoots and present in soil organic matter, rather than aboveground fresh plant litter inputs, determines seasonal fluctuation of mineral soil microbial biomass.     

亚热带地区蔬菜地甲烷净交换通量研究

农田土壤是大气甲烷(CH_4)的重要源和汇,以往关于农田CH_4净交换通量的研究多关注水稻、小麦、玉米等作物,而蔬菜地的观测研究不足。本研究采用静态暗箱-气相色谱法对亚热带地区一块种植包菜的典型露天蔬菜地开展将近1年的田间原位CH_4通量观测,以揭示蔬菜地CH_4净交换通量的周年变化特征及其影响因素,估算CH_4年累积净交换通量,并定量评估CH_4净交换通量的误差。本试验在包菜地的垄上和垄间同时布设观测点进行CH_4通量观测,并对环境因子进行同步测量,观测期为2016年1月1日至12月8日。结果表明,所研究的蔬菜地为大气CH_4的微弱汇,年平均通量为(-9.9±7.0)μg(C)×m~(-2)×h~(-1),全年累积通量为-0.84kg(C)×hm~(-2),较高的土壤水分条件和高施氮量可能是导致本研究蔬菜地CH_4吸收较弱的主要原因。全年CH_4累积通量的总体误差为-48%~-16%,其中,由于通量计算方法引起的系统误差会使估算的通量偏低32%,年尺度上的随机误差大小为16%,主要来自CH_4通量的空间差异,因此可适当增加空间重复,以减小空间随机误差。研究还发现垄上的CH_4吸收通量显著高于垄间(P0.01),因此在开展农田温室气体通量观测时应兼顾垄上和垄间、种植行和行间等农田管理措施存在显著差异的区域,均布设观测点,避免对通量观测结果造成系统性偏差。     

夏季对流层上空东风带扰动的结构演变特征及其影响西太副高短期东退的机制分析

针对东风带扰动影响西太副高短期异常东退的过程进行了分析。首先给出以下事实:位于西太副高南侧的东风带扰动与西风带扰动接近同经度时,西太副高出现异常东退。10年的统计结果表明,此现象出现的频数很高。挑选典型个例进行合成分析表明:东风带扰动具有垂直尺度深厚,上暖下冷的特征,冷区贯穿对流层中低层;垂直运动与经向风的分布取决于周围环境场;东风带扰动与西风带扰动相向移动到同经度时,南北冷区打通,在纬向上形成暖-冷-暖的温度梯度,从而引发的经向风变化是导致西太副高异常东退的原因。用热力学方程对此温度梯度的形成进行讨论,结果表明,东风带扰动西侧与西风带扰动东侧的变温联接成的负变温带造成了该温度梯度;东风带扰动西侧负变温的形成主要来自温度平流项与绝热加热项的作用;西风槽东侧负变温主要来自绝热加热项与余差项的作用。