Sensitivities of species compositions of the mixed forest in eastern Eurasian continent to climate change   总被引：2，自引：0，他引：2  

Guofan Shao  Xiaodong Yan  Harald Bugmann 《Global and Planetary Change》2003,37(3-4):307

Sensitivities of species compositions of the broadleaf–conifer mixed forest in eastern Eurasian continent to climate change were evaluated with three forest gap models, namely KOPIDE, NEWCOP, and ForClim. Testing sites are located on Changbai Mountain, the middle of the distribution range for the mixed forest. Six climate change scenarios characterizing increase in temperature and increase/decrease in precipitation were used to test the sensitivities of species composition to climate change. Simulations suggest that the mixed forest in temperate Monsoon Asia will face changes in species composition should climate change be almost certain. At the minimum level, the order of dominant species is going to change due to species competition, resulting in the increase in the proportion of broadleaved tree species in the forest. If air temperature increases and precipitation decreases, Pinus koraiensis is going to disappear from the forest and the mixed forest will become hardwood forest. This experiment supports some earlier predictions under other climate change scenarios.  相似文献   

Implications of heterogeneous flood‐frequency distributions on traditional stream‐discharge prediction techniques     

Younes Alila  Ahmed Mtiraoui 《水文研究》2002,16(5):1065-1084

Traditional flood‐frequency analysis involves the assumption of homogeneity of the flood distribution. However, floods are often generated by heterogeneous distributions composed of a mixture of two or more populations. Differences between the populations may be the result of a number of factors, including seasonal variations in the flood‐producing mechanisms, changes in weather patterns resulting from low‐frequency climate shifts and/or El Niño/La Nina oscillations, changes in channel routing owing to the dominance of within‐channel or floodplain flow, and basin variability resulting from changes in antecedent soil moisture. Not recognizing these physical processes in conventional flood‐frequency analysis probably is the main reason that many frequency distributions do not provide an acceptable fit to flood data. In this paper, we use long‐term hydroclimatic records from the Gila River basin of south‐east and central Arizona in the USA to explore the extent and significance of mixed populations. First, we discuss the probable causes of heterogeneity in the frequency distribution of annual flood and present evidence of its occurrence. Second, we investigate the implications of using various popular homogeneous distributions for predicting peak flows for basins that exhibit mixed population characteristics. Third, we demonstrate how alternative frequency models that explicitly account for floods generated by a mixture of two or more populations are both hydrologically and statistically more appropriate. We illustrate how the selection of the most plausible distribution for flood‐frequency analysis also should be based on hydrological reasoning as opposed to the sole application of the traditional statistical goodness‐of‐fit tests. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

CTAB对改善Cr(VI)萃取的研究     

张雪乔  姚秉华  羊依金  邹长武  丁恒康 《成都信息工程学院学报》2006,(3)

以煤油为溶剂,TBP为萃取剂,研究了CTAB对于Cr(VI)萃取率的影响。结果表明,CTAB能够有效改善Cr(VI)迁移效果,且在一定条件下,可使Cr(VI)萃取率提高到98%,应用于实际电镀废液,回收率在90%以上。  相似文献   

The upper ocean response to tropical cyclones in the northwestern Pacific analyzed with Argo data   总被引：3，自引：0，他引：3  

刘增宏  许建平  朱伯康  孙朝辉  张立峰 《中国海洋湖沼学报》2007,25(2):123-131

A large number of autonomous profiling floats deployed in global oceans have provided abundant temperature and salinity profiles of the upper ocean. Many floats occasionally profile observations during the passage of tropical cyclones. These in-situ observations are valuable and useful in studying the ocean’s response to tropical cyclones, which are rarely observed due to harsh weather conditions. In this paper, the upper ocean response to the tropical cyclones in the northwestern Pacific during 2000–2005 is analyzed and discussed based on the data from Argo profiling floats. Results suggest that the passage of tropical cyclones caused the deepening of mixed layer depth (MLD), cooling of mixed layer temperature (MLT), and freshening of mixed layer salinity (MLS). The change in MLT is negatively correlated to wind speed. The cooling of the MLT extended for 50–150 km on the right side of the cyclone track. The change of MLS is almost symmetrical in distribution on both sides of the track, and the change of MLD is negatively correlated to pre-cyclone initial MLD.  相似文献   

Changes in mixed layer depth and spring bloom in the Kuroshio extension under global warming     

Ruosi Zhang  Shang-Ping Xie  Lixiao Xu  Qinyu Liu 《大气科学进展》2016,33(4):452-461

The mixed layer is deep in January–April in the Kuroshio Extension region. This paper investigates the response in this region of mixed layer depth(MLD) and the spring bloom initiation to global warming using the output of 15 models from CMIP5. The models indicate that in the late 21 st century the mixed layer will shoal, and the MLD reduction will be most pronounced in spring at about 33?N on the southern edge of the present deep-MLD region. The advection of temperature change in the upper 100 m by the mean eastward flow explains the spatial pattern of MLD shoaling in the models. Associated with the shoaling mixed layer, the onset of spring bloom inception is projected to advance due to the strengthened stratification in the warming climate.  相似文献   

The role of tidal,wave and river currents in the evolution of mixed‐energy deltas: Example from the Lajas Formation (Argentina)          下载免费PDF全文

Valentina Marzia Rossi  Ronald J. Steel 《Sedimentology》2016,63(4):824-864

Many modern deltas show complex morphologies and architectures related to the interplay of river, wave and tidal currents. However, methods for extracting the signature of the individual processes from the stratigraphic architecture are poorly developed. Through an analysis of facies, palaeocurrents and stratigraphic stacking patterns in the Jurassic Lajas Formation, this paper: (i) separates the signals of wave, tide and river currents; (ii) illustrates the result of strong tidal reworking in the distal reaches of deltaic systems; and (iii) discusses the implications of this reworking for the evolution of mixed‐energy systems and their reservoir heterogeneities. The Lajas Formation, a sand‐rich, shallow‐marine, mixed‐energy deltaic system in the Neuquén Basin of Argentina, previously defined as a tide‐dominated system, presents an exceptional example of process variability at different scales. Tidal signals are predominantly located in the delta front, the subaqueous platform and the distributary channel deposits. Tidal currents vigorously reworked the delta front during transgressions, producing intensely cross‐stratified, sheet‐like, sandstone units. In the subaqueous platform, described for the first time in an ancient outcrop example, the tidal reworking was confined within subtidal channels. The intensive tidal reworking in the distal reaches of the regressive delta front could not have been predicted from knowledge of the coeval proximal reaches of the regressive delta front. The wave signals occur mainly in the shelf or shoreface deposits. The fluvial signals increase in abundance proximally but are always mixed with the other processes. The Lajas system is an unusual clean‐water (i.e. very little mud is present in the system), sand‐rich deltaic system, very different from the majority of mud‐rich, modern tide‐influenced examples. The sand‐rich character is a combination of source proximity, syndepositional tectonic activity and strong tidal‐current reworking, which produced amalgamated sandstone bodies in the delta‐front area, and a final stratigraphic record very different from the simple coarsening‐upward trends of river‐dominated and wave‐dominated delta fronts.  相似文献   

空间直线拟合的混合结构总体最小二乘算法     

邓小渊  鲁铁定  常晓涛  陶武勇 《测绘科学》2016,41(6):1-4

针对空间直线拟合不能直接采用最小二乘或总体最小二乘方法进行求解的问题,该文提出了一种基于混合结构总体最小二乘法的空间直线拟合算法。首先,由空间直线的参数方程转化成空间直线的通用函数模型;然后,根据得到的函数模型求解参数平差值,求解过程考虑了系数矩阵中常数列对平差结果的影响,顾及了系数矩阵中不同位置的重复元素得到相同改正数的事实,符合实际情况;最后,通过实例验证了算法的有效性。  相似文献   

Gender and local soil knowledge: Linking farmers' perceptions with soil fertility in two villages in the Philippines          下载免费PDF全文

Maria Elisa Christie  Mary Parks  Michael Mulvaney 《Singapore journal of tropical geography》2016,37(1):6-24

Scientists often turn to farmers to understand soil management. This process reveals differences and overlaps between local and scientific soil knowledge but rarely considers women and gender issues. This paper examines men's and women's local knowledge of soils in upland, smallholder farms in two villages in Mindanao, the Philippines, using focus group discussions, semi‐structured household interviews, field visits, GIS and soil testing. Farmers' field areas were calculated and delineated based on their perceptions of the different types of soils on their land. Men and women chose the same plots for what they considered their best soil but differed on what they felt were their worst. The fertility of the soils that women considered to be the best and worst was not significantly different from that of the men's respective choices. There was a difference in fertility, however, between the best and worst soils regardless of gender. Although soil fertility analyses showed that the women's chosen soils were similar to men's, analyses of qualitative data showed that their knowledge of soils was different and was based in part on a gendered division of labour. A multidisciplinary approach helped bridge the gap between sociocultural and physical research.  相似文献   

成都市混合层厚度的计算及方法对比   总被引：1，自引：0，他引：1  

周燕秋  倪长健  刘培川 《成都信息工程学院学报》2015,30(1):102-105

为揭示近年来成都市混合层厚度的变化特征,明晰不同混合层厚度计算方法之间的差异,利用成都市2004~2013年地面常规气象数据及同期探空数据,应用国标法、联合频率法以及干绝热法对该地大气混合层厚度进行计算分析。结果表明:国标法和联合频率法计算得到的混合层厚度年变化特征均呈下降趋势,干绝热法变化趋势平缓;国标法结果显示混合层厚度在夏季最高、冬季最低,联合频率法和干绝热法则是春季最高、秋冬季最低;就日变化而言,国标法的混合层厚度在14时最大、02时最小,此与联合频率法08时混合层厚度值最小不同。3种方法对比得到,国标法计算结果偏低,干绝热法和联合频率法计算精度较高。  相似文献   

成都市混合层厚度的计算及方法对比     

周燕秋  倪长健  刘培川 《成都信息工程学院学报》2015,30(2)

为揭示近年来成都市混合层厚度的变化特征,明晰不同混合层厚度计算方法之间的差异,利用成都市2004～2013年地面常规气象数据及同期探空数据,应用国标法、联合频率法以及干绝热法对该地大气混合层厚度进行计算分析.结果表明:国标法和联合频率法计算得到的混合层厚度年变化特征均呈下降趋势,干绝热法变化趋势平缓;国标法结果显示混合层厚度在夏季最高、冬季最低,联合频率法和干绝热法则是春季最高、秋冬季最低;就日变化而言,国标法的混合层厚度在14时最大、02时最小,此与联合频率法08时混合层厚度值最小不同.3种方法对比得到,国标法计算结果偏低,干绝热法和联合频率法计算精度较高.  相似文献