红壤区土壤有机质和全氮含量的空间预测方法

如何利用有限的土壤采样点准确预测土壤属性一直是研究的热点。近些年来,结合辅助信息的克里格空间插值应用广泛,但将土地利用类型信息作为辅助变量提高预测精度的研究鲜有报道。以中国南方红壤丘陵区的余江县为案例区,用网格法采集254个土壤样品,通过普通克里格(OK)和以土地利用方式为辅助变量的克里格(KLU)方法对土壤有机质(SOM)和土壤全氮(STN)进行空间预测,并通过102个验证点比较了两种方法的预测精度。分析表明KLU对SOM和STN的预测值与实测值的相关系数(rSOM=0.786,rSTN=0.803)明显高于OK(rSOM′=0.224,rSTN′=0.307);OK对SOM和STN的预测RMSE分别为12.48g.kg-1和0.64g.kg-1,而KLU的预测RMSE分别为6.86g.kg-1和0.37g.kg-1,仅为前者的55%和58%。可见,KLU对研究区SOM和STN的预测精度均大幅提高。同时分析也表明,KLU对不同土地利用方式SOM和STN预测精度的提高幅度存在差异,其中对旱地预测精度的提高幅度最大,对林地预测精度的提高幅度最小,水田则介于两者之间。研究表明,KLU是南方红壤丘陵区进行SOM和STN空间预测的现实和高效方法。     

A semi-parametric gap-filling model for eddy covariance CO2 flux time series data

This paper introduces a method for modelling the deterministic component of eddy covariance CO₂ flux time series in order to supplement missing data in these important data sets. The method is based on combining multidimensional semi-parametric spline interpolation with an assumed but unstated dependence of net CO₂ flux on light, temperature and time. We test the model using a range of synthetic canopy data sets generated using several canopy simulation models realized for different micrometeorological and vegetation conditions. The method appears promising for filling large systematic gaps providing the associated missing data do not overerode critical information content in the conditioning data used for the model optimization.     

白鹤中途停歇地主要食物藨草球茎密度的空间插值方法研究

扁杆藨草(Scirpus planiculmis)和三江藨草(S.nipponicus)的球茎是迁徙白鹤(Grus leucogeranus)在莫莫格中途停歇地的主要食物。2010年9月15～25日,对莫莫格白鹤集中停歇地鹅头泡湿地的20条样线上100 m等间隔470个取样点进行了地下0～20 cm的藨草球茎的取样工作。基于此,采用反距离权重、4种径向基函数和普通克里格共6种空间插值方法模拟了该区域藨草球茎密度。交叉验证和插值结果的空间分布图对比,径向基函数中的张力样条插值效果最佳,是最适于该区域挺水植物藨草球茎密度的空间插值方法。张力样条插值结果表明:研究区内藨草球茎密度均值为(46.0±44.3)个/m2。其中,<25个/m2的面积占研究区的41.7%,25～100个/m2的面积占45.9%,而>100个/m2的面积仅占12.4%。研究结果为下一步分析白鹤迁徙种群与环境因子的生态关系、预测该地区白鹤的环境容纳量提供十分重要的基础数据。     

A Comparison Between Elastic Network Interpolation and MD Simulation of 16S Ribosomal RNA

Abstract

In this paper a coarse-grained method called elastic network interpolation (ENI) is used to generate feasible transition pathways between two given conformations of the core central domain of 16S Ribosomal RNA (16S rRNA). The two given conformations are the extremes generated by a molecular dynamics (MD) simulation, which differ from each other by 10Å in root-mean-square deviation (RMSD). It takes only several hours to build an ENI pathway on a 1.5GHz Pentium with 512 MB memory, while the MD takes several weeks on high-performance multi-processor servers such as the SGI ORIGIN 2000/2100. It is shown that multiple ENI pathways capture the essential anharmonic motions of millions of timesteps in a particular MD simulation. A coarse-grained normal mode analysis (NMA) is performed on each intermediate ENI conformation, and the lowest 1% of the normal modes (representing about 40 degrees of freedom (DOF)) are used to parameterize fluctuations. This combined ENI/NMA method captures all intermediate conformations in the MD run with 1.5Å RMSD on average. In addition, if we restrict attention to the time interval of the MD run between the two extreme conformations, the RMSD between the closest ENI/NMA pathway and the MD results is about 1Å. These results may serve as a paradigm for reducedDOF dynamic simulations of large biological macromolecules as well as a method for the reduced-parameter interpretation of massive amounts of MD data.     

基于辅助环境变量的土壤有机碳空间插值——以黄土丘陵区小流域为例

利用普通克里格法(OK)、反距离加权法(IDW)、径向基函数法(RBF)、基于土地利用类型修正的普通克里格法(OK_LU)4种插值方法,对黄土丘陵羊圈沟小流域的土壤有机碳含量进行空间插值。预测结果的准确性通过Pearson相关系数(R),平均绝对误差(MAE),均方根误差(RMSE),准确度(AC)来评价。研究结果表明:(1)在前3种常规空间插值方法中,OK对刻画区域土壤有机碳的空间分布趋势效果最佳,其预测MAE值和RMSE值均为最小,Pearson相关系数(R)和准确度(AC)最大,说明其预测结果的准确性最好、预测的极端误差也最小;其次为RBF;IDW预测的效果最差。(2)OK_LU在空间特征表达方面能够更好地反映复杂地形区的局部变异,其插值结果的精度相比OK有一定程度的提高,其平均绝对误差(MAE)从0.900%降到了0.567%,均方根误差(RMSE)从1.101%降到了0.777%,Pearson相关系数(R)从0.4026提高到0.5589,准确度(AC)从0.9081提高到0.9505。综合比较,在黄土丘陵地区,OK_LU能使插值结果的精度有较大提高,是土壤有机碳空间制图的有效途径。     

逐日气象要素空间插值方法的比较

采用距离反比权重法(IDW)、协克里格法(CK)和薄盘样条法(TPS) 3种不同的空间插值方法,对我国1951-2005年气象数据完整的559个气象站点逐月第15日的平均基本气象要素(最高气温、最低气温、日照时数和降水量)进行了插值分析与评价.结果表明：3种插值方法中,TPS法对最高气温和最低气温插值的根均方差（RMSE）最小(1.02 ℃和1.12 ℃)、R²最大(0.9916和0.9913);不同季节中,TPS法对秋季最高气温、夏季最低气温进行插值的RMSE均最小(0.83℃、0.86 ℃),R²均为秋季最高.对于日照时数和降水量而言,TPS法的RMSE最小(0.59 h和1.01 mm)、R²最大(0.9118和0.8135);不同季节中,TPS法对冬季日照时数进行插值的RMSE最小(0.49 h)、R²最大(0.9293),TPS法对冬季降水量进行插值的RMSE最小(0.33 mm),IDW法对夏季降水量进行插值的RMSE最小(2.01 mm),CK法对春季降水量进行插值的R²最大(0.8781).TPS法可作为我国大量逐日基本气象要素的最优空间插值方法.     

杉木种子涩籽地理分布的空间插值法研究

应用距离反比插值法进行杉木种子涩籽率的空间插值,并提出一种改进的距离反比插值法(MID),其包含了距离反比法(ID)和距离平方反比法(IDS)。根据福建省25个杉木种子产地的涩籽率观察值,建立了杉木种子涩籽率的改进距离反比插值模型。改进距离反比插值法经交叉验证,其平均误差及平均误差平方的平方根均较距离反比法和距离平方反比法更小,具有较高的精度,平均精度达88．91％,可应用于杉木种子涩籽的空间内插。这不仅为杉木种子涩籽的空间插值提供了一种新方法,而且为地理信息系统(Geographic information system,GIS)辅助的杉木种子涩籽区域分布与流行趋势研究提供了理论依据,为福建省杉木种子园的合理布局与优化奠定基础。     

近144年来秦岭太白山林线区3-6月平均气温的重建

秦岭太白山林线植被因海拔较高且受人为扰动较轻,对气候变化的响应尤为敏感,为获取过去气候变化信息提供了可靠代用资源。然而,结合树木年代学方法及Arcgis空间插值功能进行秦岭林线气候变化重建的工作至今仍处于空白。利用采自太白山林线地带太白红杉(Larix chinensis)所建立的树轮宽度资料,与提取自太白山保护区气温栅格数据中的采样点位置气象数据进行相关分析。结果表明,太白红杉与3—6月平均气温相关性最显著,采用线性回归建立了两者的拟合模型,剔除重建方程中的1997、1998年之后,方差解释量达57.2%(调整自由度后为55.5%);重建气温序列显示偏冷时段平均跨度(16年)较偏暖时段平均跨度(10.8年)长,偏冷时段有:1870—1881年、1903—1918年和1977—1996年;偏暖的时段有:1882—1892年、1919—1929年和1997—2013年;在1931—1978年这一时期,气温相对稳定,1988年之后升温强烈;周期分析显示近144年以来3—6月气温存在22—31 a,18—22 a以及10—13 a的3个振荡周期,可能与大尺度气候驱动及太阳活动存在联系。以上结果均得到历史记录以及周边重建结果的支持。     

The impact of global climate change on tropical forest biodiversity in Amazonia

Aim To model long‐term trends in plant species distributions in response to predicted changes in global climate. Location Amazonia. Methods The impacts of expected global climate change on the potential and realized distributions of a representative sample of 69 individual Angiosperm species in Amazonia were simulated from 1990 to 2095. The climate trend followed the HADCM2GSa1 scenario, which assumes an annual 1% increase of atmospheric CO₂ content with effects mitigated by sulphate forcing. Potential distributions of species in one‐degree grid cells were modelled using a suitability index and rectilinear envelope based on bioclimate variables. Realized distributions were additionally limited by spatial contiguity with, and proximity to, known record sites. A size‐structured population model was simulated for each cell in the realized distributions to allow for lags in response to climate change, but dispersal was not included. Results In the resulting simulations, 43% of all species became non‐viable by 2095 because their potential distributions had changed drastically, but there was little change in the realized distributions of most species, owing to delays in population responses. Widely distributed species with high tolerance to environmental variation exhibited the least response to climate change, and species with narrow ranges and short generation times the greatest. Climate changed most in north‐east Amazonia while the best remaining conditions for lowland moist forest species were in western Amazonia. Main conclusions To maintain the greatest resilience of Amazonian biodiversity to climate change as modelled by HADCM2GSa1, highest priority should be given to strengthening and extending protected areas in western Amazonia that encompass lowland and montane forests.