小麦矮秆育种中性状间关系的多元分析

以7个株高梯度系列的35个系统及5个亲本品种为材料,采用典范分析和逐步回归分析研究了株高及其构成因子与产量因子、产量生理性状间的关系。结果表明:①株高因子通过产量生理性状影响产量因子,一定的生物学产量是获得高产的基础。②矮秆品种的高化对提高产量、千粒重和收获指数有利,对蛋白质含量的影响不明显;高秆品种矮化能显著提高收获指数,对籽粒的蛋白质含量影响不大。③在主要性状符合育种目标的前提下,选择倒二节间较长、第一和第二叶间距略长、穗颈和穗部较长的类型可能对提高产量有利。     

Spatial dependence and the relationship of soil organic carbon and soil moisture in the Luquillo Experimental Forest,Puerto Rico

We used geo-spatial statistical techniques to examine the spatial variation and relationship of soil organic carbon (SOC) and soil moisture (SM) in the Luquillo Experimental Forest (LEF), Puerto Rico, in order to test the hypothesis that mountainous terrain introduces spatial autocorrelation and crosscorrelation in ecosystem and soil properties. Soil samples (n = 100) were collected from the LEF in the summer of 1998 and analyzed for SOC, SM, and bulk density (BD). A global positioning system was used to georeference the location of each sampling site. At each site, elevation, slope and aspect were recorded. We calculated the isotropic and anisotropic semivariograms of soil and topographic properties, as well as the cross-variograms between SOC and SM, and between SOC and elevation. Then we used four models (random, linear, spherical and wave/hole) to test the semi-variances of SOC, SM, BD, elevation, slope and aspect for spatial dependence. Our results indicate that all the studied properties except slope angle exhibit spatial dependence within the scale of sampling (200 – 1000 m sampling interval). The spatially structured variance (the variance due to the location of sampling sites) accounted for a large proportion of the sample variance for elevation (99%), BD (90%), SOC (68%), aspect (56%) and SM (44%). The ranges of spatial dependence (the distances within which parameters are spatially dependent) for aspect, SOC, elevation, SM, and BD were 9810 m, 3070 m, 1120 m, 930 m and 430 m, respectively. Cross correlograms indicate that SOC varies closely with elevation and SM depending on the distances between samples. The correlation can shift from positive to negative as the separation distance increases. Larger ranges of spatial dependence of SOC, aspect and elevation indicate that the distribution of SOC in the LEF is determined by a combination of biotic (e.g., litterfall) and abiotic factors (e.g., microclimate and topographic features) related to elevation and aspect. This demonstrates the importance of both elevation and topographic gradients in controlling climate, vegetation distribution and soil properties as well as the associated biogeochemical processes in the LEF.This revised version was published online in May 2005 with corrections to the Cover Date.     

基于高光谱特征参数的冬小麦氮营养指数估算

为了实现快速高精度获取冬小麦氮营养指数的高光谱监测技术，利用美国SVC HR-1024I型野外光谱辐射仪对2017-2019年关中地区的冬小麦进行遥感监测，获取“三边”参数、任意两波段光谱指数和植被指数，通过相关性分析和逐步回归分析方法筛选冬小麦氮营养指数的敏感光谱参数，结合偏最小二乘回归(PLSR)、随机森林算法(RFR)、支持向量机回归(SVR)和梯度增强回归(GBDT)建立冬小麦氮营养指数模型，并对模型估算精度进行验证。结果表明，从拔节期到灌浆期，各时期的氮营养指数与任意两波段光谱指数均呈极显著相关，其中拔节期氮营养指数与任意两波段光谱指数相关性均高于其他时期，且基于一阶导数光谱的归一化光谱指数和比值光谱指数与氮营养指数的相关系数最大，为0.66。拔节期基于梯度增强回归的冬小麦氮营养指数预测模型的决定系数(r²)和均方根误差(RMSE)分别为0.96和0.05,模型验证的r²、RMSE和相对预测偏差(RPD)分别为0.95、0.12和2.12,模型预测精度最高。因此，拔节期基于梯度增强回归的冬小麦氮营养指数估算模型可用于冬小麦氮营养监测...     

基于特征筛选算法的数字土壤制图研究

平缓地带数字土壤制图中，环境协变量的选择是提高制图精度的关键。已有研究证明遥感影像可作为推理制图的辅助因子，而如何确定环境因子推理制图时各自的权重已成为现阶段研究的重点。选取湖北省麻城市乘马岗镇为研究区，采用3种特征筛选方法进行有效环境变量筛选，探索参与平原-丘陵混合区域制图的因子并确定其重要性，依据选择的相对稳定的指标，进一步探索提高土壤类型制图准确性的途径。根据141个野外独立样点的检验结果表明：在推理制图中，遥感因子在平原区域的重要性程度高于丘陵区域，且遥感因子中归一化植被指数(NDVI)和均值(Mean)较为稳定；基于递归特征算法的按地形推理制图精度最高为75.89%，分别高于ReliefF算法和基于Tree的特征筛选算法13.48%和4.97%；此外3种特征筛选算法制图结果中，按地形因子分区制图的精度均高于整体区域制图。因此，遥感因子作为辅助手段参与推理过程可有效提高制图精度。本研究采用的特征挖掘与机器学习算法对提升土壤制图精度具有一定的理论意义。     

Effects of past, present and future atmospheric CO2 concentrations on soil organic matter dynamics in a chaparral ecosystem

Owing to the continuously increasing concentration of atmospheric CO₂, it has become a priority to understand if soil organic matter (SOM) will behave as a sink or a source of CO₂ under future environmental changes. Although many studies have addressed this question, a clear understanding is still missing, particularly with respect to long-term responses. In this study, we quantified soil C stores and dynamics in relationship to soil aggregation and pool composition in a Californian chaparral ecosystem exposed for 6 years to a gradient of atmospheric CO₂ concentrations, ranging from pre-industrial levels 250 to 750 μl l⁻¹ CO₂. Fossil fuel-derived CO₂ depleted in ¹³C was used for the fumigation, thus providing a tracer of C input from the vegetation to the soil.Long-term CO₂ exposure invariably affected soil aggregation, with a significant decrease in the macroaggregate fraction at highest CO₂ levels relative to the other two size fractions (i.e. microaggregates and silt and clay). This soil structural change most likely reduced the stability and protection of SOM, and C content generally decreased in most fractions over the CO₂ treatments, and induced faster turnover of recently fixed C at high CO₂ levels. The strongest response was found in the C content of the microaggregates, which decreased significantly (P<0.05) with rising levels of CO₂. We conclude that increasing atmospheric CO₂ concentrations will decrease soil C in chaparral ecosystems, and that the microaggregate fraction is the most responsive to increasing concentrations of atmospheric CO₂.     

Isolation and biological properties of virulent subpopulations from lentogenic Newcastle disease virus strains

From each of two lentogenic Newcastle disease virus (NDV) strains of the type LaSota and Hitchner B1 a virulent subpopulation could be obtained. The two subpopulations were—in comparison to the two parent viruses—more resistant to the lipid solvent chloroform and more stable against thermal degradation. Also, the glycoproteins haemagglutinin and F (fusion) were more stable against thermal inactivation. Electron microscopic observations revealed in terms of size and morphology all of the characteristics of NDV. Both subpopulations possessed, however, the same elution kinetics as their respective parent strains. The intracerebral and intravenous pathogenicity indices as well as the mean death times of the two subpopulations allow to classify these viruses as virulent Newcastle disease viruses.     

山西高原草地景观格局分析

在GIS的支持下,以《山西高原草地分类现状图》(1∶50万)为基础,通过对底图进行矢量化处理,设置样带并对其进行抽样,应用景观指数对山西高原草地景观格局特征进行研究。结果表明:①山西高原草地具有明显的纬度和经度梯度分布规律,即由南到北草地类型多样性呈现出由简单—最多—较多的变化特点。在山西中南部(34°52'～37°07'N)以喜暖灌木类草丛为优势草地类型,中部地区(37°07'～38°01'N)以喜暖灌木草丛和山地灌丛为优势草地类型,中北部(38°01'～39°22'N)草地景观多样性达到最大(6种草地类型均见于该区),最北部(39°22'～40°16'N)草地种类较少且面积有限。②草地斑块数量由西到东具有由极少—较多—少—极多的特点,且草地分布与海拔高度具有密切关系,最西边低地与中间盆地,基本无草地覆盖;在中海拔(1 000～1 400 m)地带,斑块数量最多、草地类型最为丰富;在高海拔(1 400～2 200 m)地带,草地成片出现。     

复合表面活性剂（SDS/Tw-80）对长链烷烃的增溶和柴油污染土壤的洗脱作用

表面活性剂能够快速高效处理石油污染土壤,但由于所选用表面活性剂的类型和配比、土壤性质、污染物种类的差异,洗脱效果和作用原理不尽相同。通过研究复合表面活性剂SDS/Tw-80对石油烷烃的表观增溶和从受试土壤中的洗脱过程,探讨和阐释影响洗脱过程的各种因素。结果表明,复合表面活性剂对污染土壤中的石油烷烃洗脱效果较单一表面活性剂更好,且随复合表面活性剂SDS/Tw-80中的组分配合比例的增大而显著提高,同时能够降低胶束的成束浓度要求,扩大目标物在单位胶束内的容纳量,促使各目标长链烷烃进入胶束内部的趋势加大。复合表面活性剂的适用不仅能够改善胶束构成,且组分间表现出显著的协同作用,从而使在保证较高洗脱效率的同时能够大幅降低试剂用量,有效地克服土壤的吸附作用,把对土壤性状的影响降低,对土壤质量的恢复具有积极意义。     

Estimating aboveground biomass of Pinus densata-dominated forests using Landsat time series and permanent sample plot data

Southwest China is one of three major forest regions in China and plays an important role in carbon sequestration.Accurate estimations of changes in aboveground biomass are critical for understanding forest carbon cycling and promoting climate change mitigation.Southwest China is characterized by complex topographic features and forest canopy structures,complicating methods for mapping aboveground biomass and its dynamics.The integration of continuous Landsat images and national forest inventory data provides an alternative approach to develop a long-term monitoring program of forest aboveground biomass dynamics.This study explores the development of a methodological framework using historical national forest inventory plot data and Landsat TM timeseries images.This method was formulated by comparing two parametric methods:Linear Regression for Multiple Independent Variables(MLR),and Partial Least Square Regression(PLSR);and two nonparametric methods:Random Forest(RF)and Gradient Boost Regression Tree(GBRT)based on the state of forest aboveground biomass and change models.The methodological framework mapped Pinus densata aboveground biomass and its changes over time in Shangri-la,Yunnan,China.Landsat images and national forest inventory data were acquired for 1987,1992,1997,2002 and 2007.The results show that:(1)correlation and homogeneity texture measures were able to characterize forest canopy structures,aboveground biomass and its dynamics;(2)GBRT and RF predicted Pinus densata aboveground biomass and its changes better than PLSR and MLR;(3)GBRT was the most reliable approach in the estimation of aboveground biomass and its changes;and,(4)the aboveground biomass change models showed a promising improvement of prediction accuracy.This study indicates that the combination of GBRT state and change models developed using temporal Landsat and national forest inventory data provides the potential for developing a methodological framework for the long-term mapping and monitoring program of forest aboveground biomass and its changes in Southwest China.     

环丙唑醇对映体的反相高效液相色谱分离及其热力学研究

在高效液相色谱反相条件下,利用手性色谱柱Lux Cellulose-1(纤维素-三(3,5-二甲基苯基氨基甲酸酯,粒径分别为3μm和5μm)对环丙唑醇4个对映异构体进行了直接手性拆分研究。考察了不同粒径、流动相组成和柱温对环丙唑醇对映体色谱保留及分离的影响;并采用在线旋光检测器研究了环丙唑醇对映体的洗脱顺序;同时,利用热力学方法对对映体与固定相之间的色谱保留和分离的热力学机理进行了探讨。结果表明:以乙腈-水为流动相比甲醇-水具有更好的拆分效果,柱温降低有利于对映体的拆分;在以V(乙腈)∶V(水)=60∶40为流动相、柱温为20℃的条件下,环丙唑醇对映体在3μm(流速0.3 m L/min)和5μm(流速1.0 m L/min)色谱柱上均可得到较好分离,在满足对映体完全分离的情况下,建议优先使用3μm色谱柱,异构体洗脱顺序为(+/+/-/-);而当流动相由乙腈-水变为甲醇-水时,对映体的洗脱顺序则变为(+/-/+/-)。热力学研究结果表明:在5~40℃试验温度范围内,van't Hoff方程的线性关系良好(R20.92);以乙腈-水作为流动相时,环丙唑醇对映体的拆分过程受焓驱动;而以甲醇-水为流动相时,对映体的拆分过程既受焓驱动又受熵驱动。