浅沟坡面红壤水分季节变化特征及其影响因子

在2007年5月到2008年1月期间,供试土壤为红壤及坡面坡度为15°条件下,利用定位观测数据,探讨了天然降雨条件下浅沟侵蚀小区土壤水分季节变化特征,分析了降雨、土壤质地、等高绿篱、浅沟地形等四个因素对土壤水分动态变化的影响。结果表明,小区坡面0-45 cm土层平均土壤水分含量季节变化规律基本与降水变化一致,降水是影响浅沟坡面土壤水分变化的主要原因;绿篱对浅沟坡面土壤水分的影响因存在季节性的差异,雨季等高绿篱措施对提高浅沟坡面0-45 cm土层含水量作用显著,旱季则相反;土壤质地和浅沟微地形也是影响土壤水分变化的重要因素,但其影响都不如降雨和绿篱的影响显著,种植绿篱有利于保持坡面水分。     

Agitated soil measurement method for integrated on-the-go mapping of soil pH, potassium and nitrate contents

Knowledge of spatial variability of soil attributes within an agricultural field is critical for successful site-specific crop management. Soil sensing techniques to assess this variability on-the-go are being developed as an alternative to tedious manual soil sampling and laboratory testing. The goal of this study was to evaluate an Agitated Soil Measurement (ASM) method for integrated on-the-go mapping of soil pH, soluble potassium and residual nitrate contents using ion-selective electrodes. To implement ASM, an Integrated Agitation Chamber Module (IACM) was developed and attached to a commercial soil pH mapping implement. Precision of the tested electrodes was assessed through the root mean squared error (RMSE) and ranged from 0.10 for pK to 0.22 for pNO₃ (units represent the negative base 10 logarithm of the molar concentration of specified ions). The accuracy of the electrodes was assessed by comparing test results against reference measurements conducted in a commercial soil laboratory using the linear regression method. Average accuracy error ranged from 0.11 for pK to 0.23 for pNO₃. In a field simulation test, neither precision nor accuracy errors obtained with ASM were lower than for a previously investigated Direct Soil Measurement (DSM) method, which produced precision errors ranging from 0.11 for pH to 0.22 for pNO₃ and accuracy errors ranging from 0.12 for pNO₃ to 0.20 for pH. The coefficients of determination (r²) of linear regressions between individual field simulation measurements and corresponding average reference measurements were 0.85–0.89 (pH), 0.50–0.54 (pK), and 0.14–0.32 (pNO₃). However, laboratory evaluation of the ASM method revealed substantially lower measurement errors and increased r² values when compared to the field simulation, indicating that the proposed ASM method retains the potential for improving on-the-go field mapping. Except for reduced electrode abuse and the ability to use less expensive half-cell ion-selective electrodes, physical implementation of ASM through the IACM did not bring substantial improvement over conventionally available DSM. This could be attributed to the design of the IACM and use of half-cell electrodes. Further research is necessary to improve the design of the solution-based measuring equipment and to develop an algorithm integrating on-the-go measurements with other sources of spatial data for an improved decision-making process.     

The impact of various sprinkler irrigation patterns on spatial soil moisture variation in Vertisols

The objective of this research was to assess the effect of soil cracks on soil moisture distribution under various sprinkler irrigation applications and to identify the optimal irrigation strategy that enhances soil moisture distribution and reduces water drainage for the upper soil layer 0–250 mm. The assessment was made for six irrigation events: the first two were for 10 and 46 mm water applications using a hand shift-set sprinkler system. The second set was for 43 and 19 mm water applications using the lateral move system with fixed sprayer heads and the third pair of events were for 43 and 32 mm water applications using the lateral move system with rotating sprinklers. The experiments were conducted on two adjacent fields at the University of Queensland, Gatton, Australia. Each field was divided into 2 m × 2 m grids that covered 62 sampling locations. For each event, the initial soil moisture content (SMC) was measured at each sampling location before irrigation. After irrigation, catch can readings were recorded for each sampling location. After 12 h overnight, the second set of soil moisture measurements was taken at each location. The area1 distribution of SMC for the studied applications was quantified. An attempt was made to identify the relationship between the applied water uniformity using catch cans and the soil moisture uniformity using gravimetric water content measurements. The study also took into consideration variables that could affect the soil physical and hydrological properties including the field slope, the soil texture, the infiltration rate, the salt content and the soil organic matter content of the two fields. Since the soils were cracking clay Vertisols, further analyses were conducted on the crack dynamics, size and distribution using image analysis techniques. The research findings demonstrated that the cracks were the main contributors to water drainage below 250 mm soil depth due to the micro-run off from the crust surface to the cracks. The cracks ranged from a few millimeters to more than 40 mm in width. It was observed that the cracks which were wider than 15 mm remained open after irrigation for the specified application rates. Improving the irrigation system application uniformity did not always result in higher uniformity of the surface SMC (0–250 mm). The event that best enhanced soil moisture distribution and thus improved soil moisture recharging was observed after the sixth irrigation event when the field received 32 mm water application. The soil was at a relatively high initial SMC of 25%, (which represented 43.3% of the plant available water range) and the sprinkler water uniformity was rather high above 87% Christiansen coefficient of uniformity (CUc). At this SMC, the extent of soil cracking is limited.     

DZN2型自动土壤水分仪数据错误的原因分析

土壤水分观测仪是一种较为先进的土壤水分自动化测量仪器。它产生的土壤水分自动化观测资料可用于向农业、水利、气象等部门和公众提供土壤墒情等决策服务材料,指导农业生产和灾害评估。本文针对自动土壤水分观测仪周边观测环境变化以及站址迁移等问题导致自动土壤水分数据错误的原因进行了分析并提出相关解决方案。     

基于NIR-SlopeSWIR1-NIR特征散点图的盐渍化土壤水盐动态分析

研究以Landsat8 OLI数据的近红外(NIR)值表征土壤盐分含量,以该数据短波红外(SWIR1)与近红外值之间的斜率(Slope SWIR1-NIR)表征土壤水分含量。利用分段统计绘制NIR和相应Slope SWIR1-NIR的关系散点图,获取了玛纳斯河绿洲内部盐渍化土壤完整的水、盐年内动态变化规律。研究结果对今后基于地面试验的盐渍化土壤水盐动态分析具有一定参考价值。     

Sensor data fusion to predict multiple soil properties

The accuracy of a single sensor is often low because all proximal soil sensors respond to more than one soil property of interest. Sensor data fusion can potentially overcome this inability of a single sensor and can best extract useful and complementary information from multiple sensors or sources. In this study, a data fusion was performed of a Vis?CNIR spectrometer and an EM38 sensor for multiple soil properties. Stepwise multiple linear regression (SMLR), partial least squares regression (PLSR) and principal components analysis combined with stepwise multiple linear regression (PCA?+?SMLR) methods were used in three different fields. Soil properties investigated for data fusion included soil texture (clay, silt and sand), EC, pH, total organic carbon (TOC), total nitrogen (TN) and carbon to nitrogen ratio (CN). It was found that soil property models based on fusion methods significantly improved the accuracy of predictions of soil properties measureable by both sensors, such as clay, silt, sand, EC and pH from those based on either of the individual sensors. The accuracy of predictions of TOC, TN and CN was also improved in some cases, but was not consistent in all fields. Among data fusion methods, PLSR outperformed both SMLR and PCA?+?SMLR methods because it proved to have a better ability to deal with the multi-collinearity among the predictor variables of both sensors. The best data fusion results were found in a clayey field and the worst in a sandy field. It is concluded that sensor data fusion can enhance the quality of soil sensing in precision agriculture once a proper set of sensors has been selected for fusion to estimate desired soil properties. More efficient statistical data analysis methods are needed to handle a large volume of data effectively from multiple sensors for sensor data fusion.     

七星湖景区典型护路生态带内春季土壤物理特性研究

对防护带的白沙蒿带、旱柳-白沙蒿带和沙障-白沙蒿带3个部位以及附近裸沙区60 cm土层内的土壤含水率、容重以及机械组成进行了测定和对比分析。结果表明,各观测区土壤含水率均表现出随深度的增加而增大的趋势,30和60 cm土层含水率均为2%~3%;土壤平均含水率各样地间差异不显著。裸沙区土壤容重随深度增加略微增大,生态带内规律相反;沙障-白沙蒿带、白沙蒿带和旱柳-白沙蒿带的平均土壤容重分别比裸沙区减小了4.0%、6.4%、9.0%。表层土壤内小于0.1 mm的极细沙和粉沙含量均高于地下2层;细颗粒平均含量排序为旱柳-白沙蒿带（7.67%）〉白沙蒿带（7.56%）〉沙障-白沙蒿带（7.11%）〉裸沙区（5.03%）。观测区内土壤可为现有不同植被的萌发提供相同水平的水分条件,植被明显改善了土壤容重,增加了细物质含量,旱柳-白沙蒿这种乔灌混合模式的效果最好。     

不同灌水定额条件下土壤含水率变化试验研究

[目的]研究不同灌水定额条件下土壤含水率变化。[方法]利用时域反射仪,对不同灌水定额入渗的土壤含水率进行测定;结合土壤质地特性,分析不同灌水定额下的土壤含水率随深度变化的曲线特征。[结果]不同土层深度土壤水分变化因灌溉水量不同而不同。不灌水时,0-70 cm土层土壤含水率为9.88%;70-100 cm土层土壤含水率逐渐增大,达17.00%;100-120 cm土层含水率达25.00%;120-180 cm土层土壤含水率为24.45%。灌水量为0.029 99 m^3/m^2时,0-30 cm土层土壤含水率逐渐增大,达30.00%;30-60 cm土层土壤含水率逐渐下降,降至25.00%,60-180 cm土层土壤含水率为25.00%;灌水量为0.059 97 m^3/m^2时,0-30 cm土层土壤含水率逐渐增大,达26.00%,30-100 cm土层土壤含水率为32.50%,120-180 cm土层土壤含水率恢复到未灌溉前状态;灌水量为0.089 96 m^3/m^2时,0-180 cm土层土壤含水率为25.86%。[结论]该研究结果对经济合理地利用水资源具有重要意义。     

Cultivation Influences on Soil Organic Carbon Associated with Texture in Seasonally Frozen Zones

[Objective] This study aimed to examine indicative roles of texture representing soil organic carbon presence and variability subsequent to cultivation under cold temperate climates with seasonal freeze-thaw events.[Method] Three chronosequences were selected for paired comparisons.Soil samples were collected at six depths with a 10 cm increment.Analysis of variance with general linear model and regression was performed for statistical analysis.[Result] In seasonally frozen soils where fragmentation of macroaggregates was stimulated,soil organic carbon level was positively associated with clay ＋ silt proportion due to a wider textural range,better than sole clay content.Exponential function better fitted the experimental data to present progressively increased effectiveness of clay ＋ silt content in maintaining carbon.Clay content explained 12％-41％ and 14％-43％ of variation via linear and exponential functions,respectively.Accordingly,clay ＋ silt content explained 47％-65％ and 46％-70％.[Conclusion] Texture reflected soil organic carbon occurrence as consequences of reclamation.For seasonally frozen soils with wider textural ranges,it is robust to adapt clay ＋ silt content as dependent variable and exponential function.The generated algorithms provided an available pathway to estimate soil organic carbon losses following cultivation and to evaluate soil fertility.     

红壤水分条件对花生萌发出苗及地上部生长动态的影响

用室内培养和田间测坑试验结果:红壤的花生萌发和出苗土壤含水量分别为0.18 g/g和0.24 g/g,土壤低于萌发含水量时,种子处于低级萌发阶段,出苗率为0;土壤含水量在萌发含水量与出苗含水量之间时,种子只处在高级萌发阶段,不能出苗;土壤高于出苗含水量种子才能出苗,但出苗率并不随土壤水分的增加而增加,最适出苗含水量为0.30 g/g.长期低土壤水分对花生的株高、分枝数、叶片数及单叶面积均有不利影响,在苗期就有明显表现,在始花前后各处理间差异达到最大.     

基于颜色参数和BP神经网络的紫叶李叶片花青素含量估算

目前对植物叶片花青素含量的测定主要是湿化学法和高效液相色谱法(high performance liquid chromatography,HPLC),为简化测定方法,降低成本和提高精度,提出一种利用数码相机获取照片提取的颜色参数构建模型无损估测植物叶片花青素含量的方法。试验测定166份紫叶李叶片的花青素含量及其RGB特征值,对15种颜色参数进行皮尔逊相关分析,构建逐步多元线性回归（stepwise multiple linear regression,SMLR）、一元线性回归（single linear regression,SLR）和BP神经网络（BP neural network,BPNN）估算模型;同时对模型进行验证和比较。结果表明,1）BP神经网络模型建模集的R²、RMSE和MAE分别为0.883、0.412、0.323,验证集的R²、RMSE和MAE分别为0.796、0.462和0.353,相关系数均达到极显著水平;一元线性回归模型中,参数G-B与花青素含量的线性相关性最强,相关系数为-0.820,达到极显著水平;逐步多元线性回归模型的相关系数均达极显著水平,其中建模集的R²、RMSE和MAE分别为0.724、0.630、0.459,验证集的R²、RMSE和MAE分别为0.643、0.616和0.509。2）颜色参数与花青素含量之间具有明显的相关性,利用数码相机获取的颜色特征值估测紫叶李叶片花青素含量具有可行性;3）3种模型中,BP神经网络模型的估测效果最好,能有效地估测紫叶李叶片花青素含量,其次为逐步多元线性回归,一元线性回归模型的预测效果相对较差。     

Effect of probability-distance based Markovian texture extraction on discrimination in biological imaging

The effect of probability-distance based re-weighting of image texture features on their discrimination ability was evaluated in this study. A quadratic surface smoothing function was developed from the Bhattacharyya probability distance between two classes of images. The function was used as a re-weighting function for standard grey level co-occurrence matrix (GLCM) textural features in two cases. Case 1 involved 42 images of health and smokers’ lungs. Case 2 involved 144 images of well watered; partially water stressed and dry Rhacomitrium canescens plants. Multilayer perception (MLP) neural networks (NN) classifiers based on standard weighted and probabilistic-distance based re-weighted GLCM textural features were developed for each case. The classifiers were trained and tested using the leave-one-out and the cross-validation evaluation strategies.Probability-distance based re-weighting of GLCM textural features resulted in 37% and 39.22% reduction in true classification error for cases 1 and 2, respectively. It was concluded that re-weighting image texture features based on the probability distance between the classes involved, makes the GLCM texture analysis technique more discriminative and adaptive. This modification will help to overcome the fixed nature of GLCM features which is an area of weakness open to further improvement. Although GLCM features were used in this study, the method can be extended to other co-occurrence-based methods.     

不同改造方式对大兴安岭低质林土壤理化性质及重金属影响

对大兴安岭低质林进行带状和块状改造,分析不同方式改造后土壤理化性质及重金属的变化。结果表明:改造样地的土壤密度低于对照样地,而土壤含水率高于对照样地,土壤孔隙度也有所提高,林地土壤的物理性质得到了改善。各改造样地土壤pH值升高,土壤有机质质量分数在带宽较宽及面积较大的改造样地中更高;带状改造样地和中等采伐面积样地(225～400 m2)土壤全N质量分数高于对照样地;改造样地的土壤全P、全K以及水解N质量分数并没有得到改善;带状改造样地土壤有效P质量分数升高,块状改造样地土壤有效P质量分数下降;改造样地土壤速效K质量分数高于对照样地。样地S1、G4、G5土壤Cd质量分数高于对照样地,且与对照样地差异显著(P<0.05);各样地土壤Cu质量分数与对照样地差异不显著(P>0.05);各带状改造样地之间土壤Pb质量分数差异显著(P<0.05),样地S3土壤Pb质量分数最高。土壤Cd与Pb质量分数之间呈极显著正相关,土壤3种重金属质量分数与土壤总孔隙度正相关,与土壤有机质及水解N质量分数负相关。     

采煤对油松人工林土壤物理性质与水分的影响

以太原市西山油松人工林地为研究对象,对三个开采强度下油松林不同深度土壤物理属性和水分状况进行调查和分析测定,对比分析煤炭开采的影响。结果表明:随着煤炭开采强度的加大,土壤总孔隙度、毛管孔隙度、非毛管孔隙度下降,土壤上层和下层容重趋于一致,土壤饱和含水量下降。说明随着煤炭开采强度的加大,导致林地土壤结构变化,损害了林地土壤的保水性能。     

土壤游离氧化铁高光谱特征与定量反演

【目的】建立基于可见-近红外光谱的土壤游离铁精确预测模型,简单、快速、经济地预测土壤游离铁,有助于研究土壤发生和分类。【方法】采集广西壮族自治区的铁铝土、富铁土、淋溶土和雏形土等82个旱地土壤剖面的B层土壤,进行室内土壤化学分析、光谱测定,分析不同光谱变换后的光谱反射率与土壤游离铁含量的相关性。基于特征波段利用偏最小二乘回归(PLSR)和逐步多元线性回归(SMLR)法建立土壤游离铁含量光谱预测模型,通过决定系数(R2)、均方根误差(RMSE)和相对预测偏差(PRD)确定最优模型。【结果】土壤光谱曲线分别在457、800和900 nm波段附近有明显的游离铁吸收和反射峰特征;土壤游离铁含量与原始光谱反射率呈负相关;原始光谱经过微分变换后,游离铁含量与光谱反射率相关性显著提高;基于400～580和760～1 300 nm特征波段和一阶微分光谱变换的SMLR模型预测精度最高,其验证集的R2和RPD分别为0.85和2.62,RMSE为8.41 g·kg~(-1)。【结论】将可见近红外光谱技术应用于土壤游离铁含量高效快速地预测具有良好的可行性。广西旱地土壤光谱反射率与土壤游离铁含量具有高度的相关性,应用逐步多元线性回归方法可以很好地建立土壤游离铁含量反演模型。     

Apparent electrical conductivity measurements in an olive orchard under wet and dry soil conditions: significance for clay and soil water content mapping

Mediterranean olive trees traditionally grow under rainfed conditions, on poor soils with steep slopes. Rainfall is mainly concentrated during autumn and winter and is characterized by intense rain pulses, separated by dry periods. The use of electromagnetic induction (EMI) techniques in these olive orchards might be questioned since EMI surveys are generally recommended to be performed under moist soil conditions. A 6.7 ha olive orchard was surveyed for EMI-based apparent electrical conductivity (ECa), both under wet and dry soil conditions. In addition, 48 soil samples were analyzed for soil texture and for soil water content (SWC) under both soil conditions. The relationships between ECa, soil texture and SWC, under both soil conditions were evaluated. Despite the significantly larger ECa values measured during the wet survey as compared to the dry survey, a similar spatial correlation structure was found, indicating temporally stable ECa patterns. Significant correlations (r) were found between both surveys for ECa (r = 0.67) and for SWC (r = 0.63). The correlation between SWC and clay content exceeded 0.60 for both surveys, and the correlation between ECa and clay content was twice as high under wet soil conditions as compared to dry soil. In both situations, the ECa surveys revealed the same patterns of soil texture, indicating that moist soil conditions are not an absolute prerequisite for the use of EMI to map the spatial variability of these soil properties. Nonetheless, measuring the ECa under different moisture conditions can provide additional information about soil moisture dynamics.     

梭梭林下土壤结皮对土壤水分空间分布格局的影响

为了解土壤结皮对土壤水分空间分布格局的影响过程,以梭梭林下不同类型结皮下样地土壤水分为研究对象,采用分层取样的方法,分别对无结皮(NSC)、物理结皮(PSC)和生物结皮(BSC)样地0~0.5、0.5~10、10~20、20~40、40~60cm土层的土壤进行采集,并对各层土壤含水量进行测定,分析对比2种结皮发育对土壤水分分布格局的影响作用。结果表明:1)物理结皮与无结皮样地各层土壤含水量变化趋势基本一致,0~20cm土层的土壤含水量季节性变化幅度都较大,但略低于无结皮样地。而20~60cm土层的变化幅度较小,无结皮样地长期保持在1.0%~1.3%,物理结皮样地长期保持在0.6%~1.1%之间,显著<无结皮样地(P<0.05),深层土壤渐趋干化。2)生物结皮样地只有0~10cm土层的变化幅度较大,而10~60cm土层的变化幅度都较小,长期维持在0.4%~0.8%,土壤严重趋于干化。3)由于生物结皮对入渗水分的截留和阻碍作用,0~0.5cm土层的土壤含水量显著高于无结皮和物理结皮样地(P<0.05);而0.5~20cm土层显著低于无结皮和物理结皮样地(P<0.05);同时,20~60cm土层略<物理结皮样地,且显著<无结皮样地(P<0.05)。由此可见,相对于无结皮样地,物理结皮和生物结皮的覆盖不同程度地影响着土壤水分的空间分布格局,二者的存在不利于水分入渗,并使深层土壤渐趋干化。     

桂林喀斯特地区干湿循环过程中土壤水含量的空间变异

[目的]研究桂林喀斯特地区干湿循环过程中土壤水含量的空间分布变化,为解决该地区农田水土流失及农作物防旱抗旱提供理论依据.[方法]选取种植有大豆、梨树和甘蔗3种不同农作物的耕作地为试验地,分析3种试验地在干湿交替条件下土壤表层0~6 cm土壤水含量的空间变异,并利用地统计方法研究不同土地利用方式下的土壤空间分布变异.[结果]大豆、梨树和甘蔗3种试验地的土壤质地差异不显著(P>0.05),土壤容重表现为梨树地最小,但土壤有机质含量和总孔隙度均以梨树地最高.3种试验地湿润阶段的土壤水含量是干旱阶段土壤水含量的2~3倍.在整个干旱—湿润循环过程中,3种试验地的土壤水含量均表现为梨树地>甘蔗地>大豆地,土壤水含量空间分布比为37.18%~95.99%,呈中等偏上的空间相关性,说明试验地的空间分布在一定范围内表现稳定,但因不同的土地利用方式存在一定变异性,变异强度也因其耕作方式或管理方式的不同而异.[结论]桂林喀斯特地区土壤自身具有维持其土壤水含量空间分布稳定的能力,但耕作方式、灌溉等人为因素在一定程度上会削弱土壤水含量的空间稳定性.     

鹤大公路匝道区的土壤理化性质

对鹤大公路(牡丹江-佳木斯)的11个匝道区内16个混合土样样品的表土进行了理化性质分析,测试了不同土壤的土壤质地、pH值、含水率、有机质、铵态氮、速效磷、速效钾,结果表明:鹤大公路整个研究路段匝道区内,土壤pH值都能维持在6.5～7.5之间,呈微酸性至中性,能保证植物正常生长所需要的pH值;土壤含水率变化范围在31%～...     

两种园林用FDR土壤水分传感器的精度校正

利用质地差异较大的园土及草炭∶陶粒∶园土=3∶1∶1（体积比）的混合基质对2种土壤水分频域反射仪（FDR）进行了室内标定.结果显示,在目前园林应用的测量精度内,土壤质地对两种FDR土壤水分传感器的测量影响不显著,但FDR测量值较烘干法明显偏高,校正斜率介于0.68～0.70之间.相关分析表明FDR测量值与真实值之间有极显著的相关性,相关系数大于0.97.利用获得的线性函数进行校正,校正后的土壤水分值与采用传统的烘干称重法测得的值相符.基于以上结果,FDR土壤水分传感器能准确、快速测定土壤含水量,在城市园林节水灌溉管理中发挥重要作用.