Assessing natural and cultural influence on soil in remnant tropical woodlands     

C Y Jim  Michael W H Chan 《Area》2004,36(1):6-18

Rural Hong Kong contains culturally protected enclaves of remnant woodlands that provide sanctuary for vegetation, wildlife and soil. This study focuses on the influence of natural and cultural factors on soil properties in woodlands with different human activities. At each of the nine selected sites, two pits were dug to collect soil samples for analysis of 24 physical and chemical properties. Analyses of variance between soil attributes and site factors suggest the prominence of woodland size, and important contribution of topography, aspect and parent material. Soil indicators of human impacts and the tenacity of woodland soil towards anthropogenic disturbance were demonstrated.  相似文献   

新疆阿克苏地区耕地变化分析及驱动因子研究   总被引：8，自引：4，他引：8  

张勇  刘时银  王建  韩海东  谢昌卫 《干旱区地理》2004,27(2):228-233

据新疆阿克苏地区各市、县的统计数据，分析了阿克苏地区50年代以来耕地面积的总体变化趋势、变化速度、区域差异和驱动因子。分析表明：阿克苏地区的耕地面积呈现波动增加的态势，但人均耕地面积经历了从增加到减少的变化过程；耕地空间变化区域差异较明显；影响阿克苏地区耕地变化的8个因子可归纳为经济发展因素、人类行为因素和城市化发展水平；通过模型计算，人类行为对耕地变化的影响尤其显著。研究结果和分析结论对于阿克苏地区农业可持续发展具有重要的意义。  相似文献   

乌拉苔草光合速率日变化及日同化量   总被引：10，自引：0，他引：10  

徐惠风  刘兴土  徐克章 《湿地科学》2004,2(2):128-132

乌拉苔草沼泽是长白山沟谷湿地的重要类型 ,对其光合速率研究的结果表明 ,乌拉苔草光合速率日变化呈单峰曲线 ,最高峰出现在 1 0时 ,最大值是 1 8.0 7μmol(CO2 ) / (m2 ·s) ;与其该群落伴生的修氏苔草光合速率日变化出现“午休”现象。影响光合速率最大的环境因素是光量子通量密度和叶温 ,呈极显著的正相关 ,其他因素亦多呈正相关 ,环境因子综合影响了乌拉苔草的光合日进程。乌拉苔草光合作用的日总同化量为 1 896 0 1 .2 μmol(CO2 ) /m2 ,是光合能力较强的一种沼泽植物  相似文献   

利用现有重力场模型求定CHAMP卫星加速度计修正参数   总被引：3，自引：0，他引：3  

徐天河  杨元喜 《测绘学报》2004,33(3):200-204

CHAMP卫星加速度计数据的标定是通过确定其尺度因子和偏差参数来完成的.本文基于能量守恒方程,给出利用现有重力场模型标定CHAMP卫星加速度数据的基本原理和数学模型;提出相邻历元间差分算法,大大简化了观测方程,同时避免积分常量的计算.该算法既能同时解算尺度因子和偏差参数,也可任意求解其中之一.基于实测的CHAMP卫星加速度数据,利用EGM96模型和最新公布的EIGEN-2模型进行计算与比较,验证该方法的有效性.  相似文献   

棉花生育期关键气象因子及单产丰歉评估指标     

刘伟昌  张雪芬  王世涛  付祥建  祝新建 《气象科技》2005,(Z1)

根据河南省棉花播种面积权重,选出安阳、新乡、商丘、周口和南阳5个代表站,利用棉花产量与棉花生育期间5个代表站旬平均光照、温度、降水的相关系数,确定7个关键气象因子,建立了其与产量的回归方程,提出了考虑7个关键气象因子综合影响的棉花单产丰歉评估指标。应用该评估指标对1980~2004年棉花单产的丰歉进行检验,与实况一致的达84%,产量与评估指标相关系数达0.71以上,相关极显著。  相似文献   

小波分析方法在提取井水位潮汐因子震前变化特征的初步应用          下载免费PDF全文

杨从杰  冯志生  宋德伟  张秀霞  梅卫萍  张晓勇 《地震工程学报》2005,27(2):163-167

运用小波分析方法对1990年常熟、1995年苍山和1996年南黄海三个中强地震前江苏地区井水位固体潮的变化特征进行了研究，发现井水位M2波潮汐因子在地震前几个月几乎都出现一个幅度较大、周期为半月或一个月左右的异常信号，表明小波分析方法在处理和分析井水位潮汐资料方面可能是一种有效的方法。  相似文献   

锦州地震台体积式钻孔应变仪的映震情况     

明成山  李京锦  李哲 《地震地磁观测与研究》2005,(Z1)

论述了张北MS6.2、沈阳ML4.1、内蒙古ML5.9、日本北海道MS8.0、俄蒙中交界MS7.9、青海昆仑山MS8.1地震前后,锦州地震台体积式钻孔应变仪观测震前异常的变化规律。通过计算潮汐因子、振幅因子、3点线性平滑滤波残差值等方法,识别异常。结果表明,体应变异常资料与地震有一定的相关性。  相似文献   

Study on comparison between absolute and relative input energy spectra and effects of ductility factor     

公茂盛  谢礼立 《地震学报(英文版)》2005,18(6):717-726

Introduction Estimation of an attenuation relationship for strong ground motion parameters has been an interesting research subject in the field of engineering seismology and has played a very important role in seismic safety evaluation, seismic zoning, seismic hazard evaluation of major constructions, etc. At present, the generally used parameters include peak acceleration, peak velocity and elastic response spectrum. Such parameters mentioned above are essentially independent of the duration…  相似文献   

Chemical forms of heavy metal contaminants in sediments of Miyun reservoir     

LIU Xiaoduan  XU Qing  GE Xiaoli  LIU Liu  WU Dianwei 《中国科学D辑(英文版)》2005,48(Z2)

The chemical forms, spatial distribution and sources of As, Hg, Cd, Pb and Zn in sediments of the Miyun reservoir were studied. The results of sequential extraction demonstrate that most of As, Pb and Zn were bound to the residual fraction, Hg was associated with the sulfide fraction while Cd was associated with the carbonate fraction and the residual fraction. On the vertical profiles the concentrations of the heavy metals in total and each fractions mostly decreased with increasing depths in sediments, suggesting that the heavy metals input from the upstream watershed increases yearly. Summation of the residual fraction, the sulfide fraction and the carbonate fraction accounts for 60.03%―85.60% of the total heavy metal contents in the sediments, which represent the geochemical background values of the elements and relate closely to soil erosion. Results of the main factor analysis show that most sediments of the reservoir come from the upstream soil erosion, the point source pollution and domestic waste. Moreover, the microbial activities taking place on the sediment-water interface are also one of the major factors to cause the increasing content of the organic matter fraction and the iron-manganese oxide fraction. Environmental change of the reservoir water could make the removability of the heavy metals increase, leading to the increase of their concentrations in pore water in sediments, and imperiling water quality of the reservoir.  相似文献   

Knowledge Representation Methods in Expert System for Earthquake Prediction ESEP 3.0     

Wang Wei 《中国地震研究》2005,19(1):43-53

INTRODUCTIONKnowledgerepresentationandknowledgeacquisitionarekeyissuesinbuildinganexpertsystem .Theyarecloselyrelatedtothedomainproblem solvinglevelandcompetenceoftheexpertsystem .Intheknowledgeacquisitionprocess,thedomainexpertwillfirstofferandorganizepr…  相似文献