Fire Environment Mechanism of Lightning Fire for Daxing''''an Mountains

Lightning fire is one of natural fires; its mechanism is very complex and difficult to control. Daxing'an Mountain is the main region that lightning fires occur in China. Research on lightning fires indicates that special fuel, dry-storm weather and high altitude form the lightning fire environment. Lightning fires have close relation with lights. When lightning occurs, especially dry-lightning which brings little precipitation with surface temperature growing and fuel dehydrating, these often lead to lightning fires. Lightning fires have characteristics of geography, time and topography. The higher altitude forest region in Daxing'an Mountain, the more lightning fires occur. Valley with altitude above 800 m in the north of 51.N and Larix gmelinii-Pinus pumila, Pinus sylvestris var. mongolica -Pinus pumila forests on the top of mountain are the most concentrating region where lightning fires occur. One serial dry-storming can ignites many lightning fires, the furthest between them is as long as 150 km.     

波涌灌溉核心设备-波涌阀的研究

波涌灌溉技术是20世纪70年代末发展起来的地面灌水新技术。该系统一般由水源、波涌阀、自控器和田间输配水管道等组成。根据我国丘陵山区机修梯田地的灌溉特点,运用水力学原理开发研制了波涌灌溉的核心设备—波涌阀。经过田间灌水试验,结果表明:波涌阀阀片的密闭止水效果、阀片的启闭定位等各项性能指标均满足波涌灌溉设备的性能要求,该设备具有较高的实用性和可操作性。     

波涌灌溉技术田间适应性分析

利用地面灌溉模型对波涌灌溉条件下地表水流及入渗过程进行模拟,在模拟结果与田间实测资料对比基础上,确定适宜的田间灌水参数,即土壤入渗强度、田块规格、田面坡度、入地流量、田间微地形等的变化范围,给出适合于波涌灌水方法应用的田间组合条件,提出波涌灌水技术对壤类土质的田间适应性,为制定波涌灌溉的田间实施方案提供科学的依据     

Dust storm erosion and its impact on soil carbon and nitrogen losses in northern China

There is increased awareness of the environmental impacts of soil carbon (C) and nitrogen (N) losses through wind erosion, especially in areas heavily affected by dust storm erosion. This paper reviews the recent literature concerning dust storm-related soil erosion and its impact on soil C and N losses in northern China. The purpose of our study is to provide an overview of the area of erosion-affected soils and to estimate the magnitude of soil C and N losses from farmland affected by dust storm erosion.According to the second national soil erosion remote-sensing survey in 2000, the area affected by wind erosion was 1.91 million km², accounting for 20% of the total land area in China. This area is expanding quickly as the incidence of heavy dust storms has greatly increased over the last five decades, mainly as a result of the intensification of soil cultivation. The economic and ecological damage caused by wind erosion is considerable. Heavily affected areas show a loss of nutrients and organic carbon in soils and the heavily degraded soils are much less productive. Compared with the non-degraded soil, the C and N contents in degraded soils have declined by 66% and 73%, respectively. The estimated annual losses per cm toplayer of soil C and N by dust storm erosion in northern China range from 53 to 1044 kg ha^− 1 and 5 to 90 kg ha^− 1, respectively. Field studies suggest that soil losses by wind erosion can be reduced by up to 79% when farmers shift from conventional soil tillage methods to no-till. Thus shifting to no-till or reduced tillage systems is an effective practice for protecting soil and soil nutrients. Our study indicates that soil conservation measures along with improved soil fertility management measures should be promoted in dry-land farming areas of northern China. As erosion is a major mechanism of nutrient withdrawal in these areas, we plead for the development of accurate methods for its assessment and for the incorporation of erosion, as a nutrient output term, in nutrient budget studies.     

神经网络与暴雨泥石流灾害预报

建立了用于暴雨泥石流适时预报的人工神经网络模型，在荒溪分类和危险区划分基础上，结合北京山区暴雨泥石流例子，验证模型判别结果与实际情况相符，应用效果良好。     

坡面水土保持措施影响流域产汇流特性值计算与分析

以甘肃省武都地区清水沟小流域为研究对象，通过实地调查和资料分析，推求出清水沟流域产流和汇水特征值，并求得其设计洪水过程线，同时通过模拟实验验证实地勘测成果，为提出和计算流域水力类泥石流体的起动安全洪水过程线服务。     

涌泉根灌多点源交汇入渗湿润体试验研究

在米脂山地微灌枣树示范基地进行原状土涌泉根灌入渗试验,研究了多点源交汇入渗条件下涌泉根灌湿润体特征值的变化规律.结果表明,涌泉根灌多点源交汇入渗孔洞处和交汇面处的湿润锋运移距离与入渗时间均符合幂函数关系,交汇面处的湿润锋运移速度比孔洞处的快,最终交汇入渗湿润土体沿孔洞布置方向的剖面形状近似带状;在孔洞底部周围的中间区域...     

香港暴雨中心迁移与滑坡位置关系分析

香港地区每年均有一定数量的滑坡灾害发生,诱发滑坡灾害的主要因子是强降水,即暴雨.暴雨过程中,降水强度的时空分布存在一定差异性,这种降水强度的时空与滑坡灾害的时空分布存在一定的联系.以香港地区1992年5月8日暴雨为例,以30 min为时间间隔,分析了暴雨中心时空变动与滑坡事件时空分布及出现频率之间的关系,发现空间上滑坡均出现在暴雨中心或暴雨中心的边沿地区;时间上滑坡事件出现在暴雨中心出现或上一阶段时间内;并且降水的强度与滑坡的出现频率也有一定关系.     

波涌灌间歇入渗饱和-非饱和土壤水分运动数值模拟及试验

考虑到地下水浅埋对上层包气带水分分布造成一定影响,该研究结合波涌灌技术,对地下水浅埋下间歇入渗的土壤水分分布特征和运动规律进行了分析,建立了基于饱和-非饱和土壤条件下一维间歇入渗水分运动模型,根据试验实测资料采用Hydrus-1D软件反推土壤水分运动参数,并对入渗过程进行了模拟。在此基础上,确定了饱和导水率的估算模型。结果表明:所建参数估算模型较好地反映了饱和导水率与间歇周期数、循环率以及周期时间之间的相关关系,所建水分运动模型模拟值与实测值比较,累计入渗量、土壤含水率以及湿润体运移距离总体相关系数高于0.96,均方差在0.5以内,吻合度较高,能够较好地描述了地下水影响条件下波涌灌间歇入渗饱和-非饱和土壤水分运动特征。该研究为波涌灌技术进一步发展奠定了科学基础。     

灌施连续与间歇入渗硝态氮运移与土壤含水量的关系

通过室内土壤灌施间歇入渗试验，研究了灌施条件下波涌灌溉土壤间歇入渗硝态氮的运移与分布特性，分析了硝态氮分布与土壤含水量的关系，并与灌施条件下土壤连续入渗进行了对比，为进一步研究施肥条件下波涌灌溉土壤间歇入渗溶质运移规律奠定了基础。