产量变化的主要成份分析

利用历史产量序列重构二维时变矩阵进行自然正交分解 ,得到了 3种影响产量变化的主要成份。通过分析发现 ,这些主要成份不仅包括能反映生产力变化的趋势分量和能表达气候影响效果的短期振荡分量 ,还发现了一种由气候决定的趋势作用分量 ,对产量有着不可忽视的影响。这些分量相互独立 ,无预先设定的函数模型 ,为产量分析和预报提供了较为客观和完备的历史变动序列 ,对提高产量预报精度有着重要意义。

Storage,Patterns and Controls of Soil Nitrogen in China

Soil holds the largest nitrogen(N)pool in terrestrial ecosystems,but estimates of soil N stock remain controversial. Storage and spatial distribution of soil N in China were estimated and the relationships between soil N density and environmental factors were explored using data from China's Second National Soil Survey and field investigation in northwest China and the Tibetan Plateau.China's soil N storage at a depth of one meter was estimated at 7.4 Pg,with an average density of 0.84 kg m^(-2).Soil N density appeared to be high in southwest and northeast China and low in the middle areas of the country.Soil N density increased from the arid to semi-arid zone in northern China,and decreased from cold-temperate to tropical zone in the eastern part of the country.An analysis of general linear model suggested that climate and vegetation determined the spatial pattern of soil N density for natural vegetation,which explained 75.4% of the total variance.

Spatial and Quantitative Comparison of Satellite-Derived Land Cover Products over China

Because land cover plays an important role in global climate change studies, assessing the agreement among different land cover products is critical. Significant discrepancies have been reported among satellite-derived land cover products, especially at the regional scale. Dif- ferent classification schemes are a key obstacle to the comparison of products and are considered the main fac- tor behind the disagreement among the different products. Using a feature-based overlap metric, we investigated the degree of spatial agreement and quantified the overall and class-specific agreement among the Moderate Resolution Imaging Spectoradiometer （MODIS）, Global Land Cover 2000 （GLC2000）, and the National Land Cover/Use Data- sets （NLCD） products, and the author assessed the prod- ucts by ground reference data at the regional scale over China. The areas with a low degree of agreement mostly occurred in heterogeneous terrain and transition zones, while the areas with a high degree of agreement occurred in major plains and areas with homogeneous vegetation. The overall agreement of the MODIS and GLC2000 products was 50.8% and 52.9%, and the overall accuracy was 50.3% and 41.9%, respectively. Class-specific agree- ment or accuracy varied significantly. The high-agreement classes are water, grassland, cropland, snow and ice, and bare areas, whereas classes with low agreement are shru- bland and wetland in both MODIS and GLC2000. These characteristics of spatial patterns and quantitative agree- ment could be partly explained by the complex landscapes, mixed vegetation, low separability of spectro-temporal- texture signals, and coarse pixels. The differences of class definition among different the classification schemes also affects the agreement. Each product had its advantages and limitations, but neither the overall accuracy nor the class-specific accuracy could meet the requirements of climate modeling.

Effect of Microclimatic Modification on Growth and Yield of Sesame （Sesamum indicum L.） in a Semi-Desert Region of Northern Sudan

An investigation was carried out in the semi- desert region of northern Sudan, during 2000, to study the influence of different micrometeorological parameters on growth and yield of sesame under alley cropping system. Sesame, cv. Kenana-2, was grown in 6-m wide alleys formed by 3 year old Acacia ampliceps and Acacia stenophylla. Air temperature, relative humidity, wind speed, solar energy and shade behaviour were measured throughout the growing season. Irrigation was measured by water meter and soil moisture by gravimetric sampling at depths of 15, 30, 45 and 60 cm, in alley cropping and control plots. Sesame was evaluated for growth and yield performance in southern, central and northern parts of each alley. The results showed substantial reduction in wind runs, solar radiation and air temperature, while relative humidity was increased under alley conditions. Soil moisture content, especially in the upper 045 cm soil depth, was much higher in alley cropped plots than in the control plots. A. stenophylla resulted in the highest saving of irrigation water and considerably increased （40%） sesame seed yield. In contrast, sesame seed yield was reduced by 46% under A. ampliceps-alley cropping. Competition for light and water were highly responsible for variation in sesame seed yield in the different zones of the alley. A. stenophylla tree is, therefore, recommended in an alley cropping system in the semi-desert region of northern Sudan for its superiority in optimizing radiation and saving of irrigation water.

The Role of Harmattan in the Edaphic Processes in the Extreme-North-Cameroon

In the Cameroonian sudano-sahelian and sahelian zone, karal soils i.e., vertisoils and soils with vertic similarities largely spread on tropical black clay in depressions and fiat sectors. Those black cotton soils are out of season＇s sorghum loft, locally called as muskwari. As the staple diet in the Cameroonian dry areas, this crop becomes more and more an alternative to drying or better to climate changes. Till now, those soils are considered to be lacustrine or they are resulting just from weathering, according to pedologic researchs. The purpose of this communication, therefore, is to show the effects of Harmattan on the basis of our field＇s observations, investigations and superficial deposits＇ analysis： granulometry and diffractometry in the laboratory. Harmattan is a dry and stable air mass which originates from the saharian anticyclone. Its participation in edaphics process is very relevant. Indeed, dust storms take place throughout the dry season and vertisoil spreads out on various topographic locations bringing about homogeneity of texture and similarity of mineralogic spectrum. Their high kaolinite content, thin granulometric component （fine sand, silt and clay） are indicative of Aeolian loessial dust deposits. It could not be something else in this area of the most southern saharian blow of the great Saharo-Sahelian GWAS （global wind action system） in sub-equatorial latitudes, in line with the venturi formed by Ennedi and Tibesti mountains.

Impacts of climate change on agricultural water resources and adaptation on the North China Plain

Climate change is having a considerable impact on the availability of water resources for agricultural production on the North China Plain （NCP）, where the shortage of water is currently disturbing the stability and sustainability of agricultural production with respect to the drying tendency since the 1950s. However, although potential evapotranspiration （ET） has shown a decreasing trend under climate change, actual ET has slightly increased with an acceleration in hydrological cycling. Global climate model （GCM） ensemble projections predict that by the 2050s, the increased crop water demand and intensified ET resulting from global warming will reduce water resources surplus （Precipitation-ET） about 4%-24% and increase significantly the irrigation water demand in crop growth periods. This study assesses possible mitigation and adaptation measures for enabling agricultural sustainability. It is revealed that reducing the sowing area of winter wheat （3.0%-15.9%） in water-limited basins, together with improvement in crop water-use efficiency would effectively mitigate water shortages and intensify the resilience of agricultural systems to climate change.

基于2008年1月中国南方低温雨雪冰冻事件10-30天延伸期稳定分量的研究

对北半球1978—2007年1月6日—2月4日逐日500 hPa高度场资料带通滤波,得到10—30 d时间尺度分量,结合经验正交函数分解方法(empirical orthogonal function,EOF)提取出气候态基底.同样滤波北半球2008年1月冰冻雨雪事件的逐日实况资料,并将其投影到气候态基底上,利用各贡献率作为考察该EOF分量对原场的影响指标.从10—30 d延伸期预报的角度提取稳定分量进行诊断分析,探讨影响此次天气过程的主要因素.通过贡献率分析方法把10—30 d延伸期稳定分量划分为气候态稳定分量和异常型稳定分量两个部分.结果表明:气候态稳定分量在我国南方2008年1月冰冻雨雪事件中占主体地位,异常型稳定分量相当于在气候态稳定分量的基础上叠加的扰动值,但异常型稳定分量在本次过程中的作用不能忽视,甚至起到关键性的作用,并且与实况距平在太平洋地区整体环流形势有较好的对应.这些结论加深了对10—30 d时间尺度可预报性的认识,为10—30 d延伸期预报提供了一种新的思路和解决问题的途径.

2009年11月冰冻雨雪事件10-30d延伸期稳定分量提取及分析

针对2009年11月冰冻雨雪事件,通过经验正交函数分解等方法提取10—30 d稳定分量,并第一次运用计算贡献率和相似系数判定等手段把稳定分量进一步客观地分离成气候态稳定分量和异常型稳定分量.将气候态稳定分量与低通滤波分量合成气候背景场.研究发现:气候背景场环流形势持续时间较长,随时间变化缓慢,主要提供了事件发生的气候背景,指示大尺度环流调配置和调整;气候背景场空间活动范围较大,能较好地刻画永久半永久性大气活动中心变化情况,且在垂直各层有稳定一致的配置关系;异常型稳定分量重点体现了环流相对异常特征,与2009年11月冰冻雨雪事件有较好的对应关系.在气候背景场提供确定的环流大背景下,异常型稳定分量表征了对应天气系统的相对强弱变化.

基于2009年初长江中下游地区持续阴雨过程的10～30天延伸期稳定分量的提取及配置分析

2009年2月中下旬至3月上旬,中国长江中下游地区出现了持续阴雨天气,这次持续性异常事件影响范围之广、持续时间之长为历史罕见.本文利用EOF分解方法对相应时段NCEP-DOE Reanalysis2逐日位势高度场距平资料进行分析,定义了10～30天延伸期稳定分量,并根据各EOF分量的贡献率的不同变化特征进一步定义了10～30天延伸期气候态稳定分量和异常型稳定分量.气候态稳定分量主要解释气候平均信息对延伸期天气过程的影响,而异常型稳定分量则侧重体现了持续性阴雨过程的"异常"特征.研究发现,稳定分量尤其是异常型稳定分量具有如下特征:(1)时间尺度较长,能维持较长时间(10天以上)的稳定或者表现为月尺度的低频变化及超长波活动;(2)空间活动范围较大,表现为行星尺度的超长波活动,且在垂直各层有稳定一致的配置关系;(3)能够较好地反映中高纬大气环流的变化特征,体现了指数循环和超长波的移动、调整活动;(4)与地面持续性天气过程有较好的对应关系.

基于2013年8月中国中东部地区持续高温的延伸期稳定分量提取及改进研究

基于2013年8月中国中东部地区持续高温及其减弱过程,利用美国国家环境预报中心/美国国家大气研究中心逐日平均的500 h Pa高度场、风场再分析资料和美国国家海洋和大气管理局的海温重建扩展资料进行分析,通过前期海温强迫相似年的选取方法以及带通滤波和经验正交函数分解等方法提取出10—30 d的稳定分量,并通过对稳定分量的诊断分析探究了这次持续高温及其减弱过程的维持机制.研究发现:通过选取与个例前期海温强迫最相似的30年来代替常规的气候态30年(1981—2010年),所提取的气候态稳定分量所占的比重变化不大,稍有减弱,而异常型稳定分量占的比重显著性提高,且其所刻画的影响异常事件的天气系统强度及稳定性明显提高,能够更加清晰地显示延伸期天气过程的维持机制.这表明在提取稳定分量时考虑前期的海温强迫作用是非常有必要的.同时,通过对延伸期稳定分量的分析,表明此次持续高温及减退过程主要受到北极涛动、亚洲大陆中高纬纬向环流形势和西太平洋副热带高压(西太副高)强度、位置的共同影响.

Climatic and Edaphic Controls on Soil pH in Alpine Grasslands on the Tibetan Plateau,China:A Quantitative Analysis

Soil acidity is an important parameter that can regulate ecosystem structure and function.However,a quantitative understanding of the relationships between soil pH and environmental factors remains unavailable.In this study,relationships of soil pH with both climatic and edaphic factors in alpine grasslands on the Tibetan Plateau,China were quantified using data obtained from a regional soil survey during 2001-2004.Our results showed that soil pH decreased along the gradient of both mean annual temperature and precipitation.Likewise,soil pH exhibited consistent negative correlations with soil moisture and silt content.However,soil organic and inorganic carbon contents played opposite roles in shaping patterns of soil pH:the accumulation of soil organic matter led to higher soil acidity,while the existence of soil inorganic matter was favorable for maintaining higher soil alkalinity.The variation partitioning analysis indicated that the combination of climatic and edaphic variables explained 74.3%of the variation in soil acidity.These results suggest that soil pH could be predicted from routinely-measured variables,allowing a robust pedotransfer function to be developed.The pedotransfer function may facilitate land surface models to generate more reliable predictions on ecosystem structure and function around the world.

Spatio-temporal Characteristics of the Extreme Climate Events and Their Potential Effects on Crop Yield in Ethiopia

Extreme climate events exhibit an increasing spatio-temporal trend globally, and the increasing intensity and frequency may have severe impacts on the human society and natural ecosystems. This study analyzed the extreme temperature and precipitation variability from 1956 to 2016, and evaluated their potential effects on crop yield in Ethiopia. Relative extreme temperature indices exhibited a decreasing trend with low-temperature events, but a significantly upward trend with extreme high temperature events. The frequency of annual warm nights increased to a greater degree than that of cold days. The total annual wet-day precipitation decreased significantly at a rate of-46 mm/decade. Further, the succession of dry days gradually increased by 5.6 day/decade, while an opposite trend of wet days was found with a decline of 1.4 day/decade. The correlation between annual precipitation and crop production was 0.422, indicating that extreme precipitation indices may have higher explanatory power than extreme temperature indices in the crop yield variations. Moreover, the extreme climate changes have induced significant adverse impacts on crops yield particularly in Ethiopia where no proper adaptation measures have been implemented.

Latitudinal and climatic distributions of 3D craniofacial features among Holocene populations

The geographical and climatic patterning in craniofacial morphology among recent hominids has been regarded as relatively reliable evidence of environmental adaptation and natural selection,which is largely attributed to thermoregulation.However,the relative influence of genetic and environmental factors on craniofacial features is unclear.Our study employed 3D laser scanning techniques to evaluate the association between geographical(latitude),climatic(annual temperature)factors,and 3D craniofacial measurements in 18 recent populations through bivariate correlation analysis.Significant correlations were found among braincase surface area,zygomatic bone surface area,cranial-facial index(facial surface area relative to braincase surface area)and local temperature,and a clear latitudinal gradient was also found in variation of braincase surface area.No significant correlations were found between zygomatic bone surface area,cranial-facial index and latitude.Our analysis supports the idea that the braincase functions as a radiator and is closely related to direct sunlight.We also suggest that absolute/relative craniofacial surface area varies consistently with predictions derived from Bergmann’s Rule.The mosaic craniofacial traits of American Indians may reflect retention of cold-derived,ancestral features,as well as a response to a slightly warmer climate.Because different craniofacial regions preserve environmental/genetic signatures differentially,caution is suggested when craniofacial anatomy is used for phylogenetic reconstruction and functional-morphological analysis.

Analysis of observations on the urban surface energy balance in Beijing

The 1-year（2009-2010） measurements are analyzed of the urban surface energy balance（SEB） obtained from the sensors located at three vertical layers of a 325-m tower in downtown Beijing.Results show that：（1） The measurements from the 325-m tower represent the SEB characteristics of the cities located in semi-humid warm-temperate continental monsoon climate zone.In a typical hot and rainy summer,cold and dry winter,the measured Bowen ratio is minimum in summer and maximum in winter.The Bowen ratio measured at 140 m for spring,summer,autumn,and winter are 2.86,0.82,1.17,and 4.16 respectively.（2） At the height of 140-m（in the constant flux layer）,the noontime albedo is ~0.10 for summer,~0.12 for spring and autumn,and ~0.14 for winter.The ratios of daytime sensible heat flux,latent heat flux,and storage heat flux to net radiation are 0.25,0.16,and 0.59 for clear-sky days,and 0.33,0.19,and 0.48 for cloudy days respectively.（3） Under clear-sky days,the nighttime sensible heat flux is almost zero,but the latent heat flux is greater than zero.For cloudy days,the nighttime sensible heat flux is slightly greater than the latent heat flux in winter.The nighttime upward heat flux is presumably due to the anthropogenic release（mainly latent heat for summer,while latent and sensible heat for winter）.

Changes in carbon storages of Fagus forest ecosystems along an elevational gradient on Mt. Fanjingshan in Southwest China

Aims There are different components of carbon(C)pools in a natural forest ecosystem:biomass,soil,litter and woody debris.We asked how these pools changed with elevation in one of China’s ecologically important forest ecosystem,i.e.beech(Fagus L.,Fagaceae)forests,and what were the underlying driving factors of such variation.Methods The four C pools in nine beech forests were investigated along an elevational gradient(1095–1930 m)on Mt.Fanjingshan in Guizhou Province,Southwest China.Variance partitioning was used to explore the relative effects of stand age,climate and other factors on C storage.In addition,we compared the four C pools to other beech forests in Guizhou Province and worldwide.Important Findings The total C pools of beech forest ecosystems ranged from 190.5 to 504.3 Mg C ha^(–1),mainly attributed to biomass C(accounting for 33.7–73.9%)and soil C(accounting for 23.9–65.5%).No more than 4%of ecosystem C pools were stored in woody debris(0.05–3.1%)and litter(0.2–0.7%).Ecosystem C storage increased significantly with elevation,where both the biomass and woody debris C pools increased with elevation,while those of litter and soil exhibited no such trend.For the Guizhou beech forests,climate and stand age were found to be key drivers of the elevational patterns of ecosystem and biomass C storage,while for beech forests globally,stand age was the most important predictor.Compared to beech forests worldwide,beech forests in Guizhou Province displayed a relatively higher biomass C accumulation rate,which may be explained by a much higher precipitation in this area.The present study provides basic data for understanding the C budgets of Chinese beech forests and their possible roles in regional C cycling and emphasizes the general importance of stand age and climate on C accumulation.

Spatial distribution of surface energy fluxes over the Loess Plateau in China and its relationship with climate and the environment

China's Loess Plateau is located at the edge of the Asian summer monsoon in a transition zone of climate and ecology. In the Loess Plateau, climate and environments change along with space, which has an obvious impact on the spatial distribution of surface energy fluxes. Because of scarce land-surface observation sites and short observation time in this area, previous studies have failed to fully understand the land-surface energy balance characteristics over the entire the Loess Plateau and their effect mechanisms. In this paper, we first test the simulation ability of the Community Land Model(CLM) model by comparing its simulated data with observed data. Based on the simulation data for the Loess Plateau over the past thirty years, we then analyze the spatial distribution of surface energy fluxes and compare the pattern differences between the area averages for the driest year and wettest year. Furthermore, we analyze the relationship between the spatial distribution of the components of the surface energy balance with longitude, latitude, altitude, precipitation and temperature. The main results are as follows: the spatial distribution of surface energy fluxes are significantly different, with the surface net radiation and sensible heat flux increasing from south to north and latent heat flux and soil heat flux decreasing from southeast to northwest. The sensible heat flux at the driest point is nearly twice as high as that at the wettest point, whereas the latent heat flux and soil heat flux at the driest point are half as much as that at the wettest point. The impact of variations of annual precipitation on the components of the surface energy balance is also obvious, and the maximum magnitude of the changes to the sensible heat flux and latent heat flux is nearly 30%. To a certain extent, geographical factors(including longitude, latitude, and altitude) and climate factors(including temperature and precipitation) affect the surface energy fluxes. However, the surface net radiation is more closely related to latitude and altitude, sensible heat flux is more closely related to the monsoon rainfall and latitude, and latent heat flux and soil heat flux are more closely related to the monsoon rainfall.