Theoretical and field comparison of two types of soil heat fluxmeter

Accurate measurements of soil heat flux are important for energy balance studies on bare soils. Measurements are usually made with passive transducers that transform the vertical soil heat flux into an e.m.f.. Measurement errors or bias result from differences between the calibration coefficients provided by the manufacturer and those determined in the field. These differences result from bad thermal contact between the soil and the fluxmeter and/or changes in soil thermal conductivity. New printed circuit heat fluxmeters are very thin (0.2 mm) and they provide a better thermal contact with the soil because they have an external copper layer instead of an insulating resin. We carried out a theoretical analysis to identify properties of the transducers (geometrical, thermal or electrical) most important for reducing the calibration variability. The transducer thickness was found to reduce the calibration variability due to large soil thermal conductivity variations. Transducer thermal conductivity is also important when the soil thermal conductivity is accurately known. The printed circuit transducers and classical soil heat flux transducers (thermopiles) where then compared in three different soils, a sandy loam, a loamy and a chalky soil under changing climatic conditions in spring. The outputs of both transducers were compared to reference soil heat flux measurements obtained by the heat storage method. The thermopile transducers were more sensitive (4.1 μV W⁻¹ m²) than the printed circuit transducers (1.6 μV W⁻¹ m²). Both transducers gave similar responses when the soil thermal conductivity varied over a narrow range. The total variation of the calibration coefficients of the printed circuit transducer was smaller for all three soils and for days where the soil thermal conductivity varied widely. We conclude that the printed circuit transducers should be used when field calibration is not possible, or when the calibration is not stable following large soil thermal conductivity variations. The experiment also showed that the theory does not completely describe the interaction between calibration coefficients and soil properties. We have therefore developed a new interpretation of the experimental data that takes into account the thermal contact between the soil and the transducer.     

毛竹导热系数的神经网络预测模型

为了准确测算一定范围内的毛竹导热系数,同时改进现有的竹材导热系数研究方法,笔者采用激光闪光法精确测量毛竹导热系数值,并以此为基础,建立毛竹导热系数随不同温度和密度变化的神经网络预测模型。由于原始BP算法收敛速度慢,笔者使用Trainlm函数训练神经网络模型,确定了最佳隐层神经元个数,并对该模型的输出预测值进行线性分析及误差分析。实验结果如下：毛竹导热系数神经网络模型具有很高的预测精度,能准确预测一定条件范围内毛竹的导热系数,从而节省了以往常规试验所花费的大量时间和资源。本研究初步揭示了毛竹导热系数随温度、密度等因素的变化关系,为进一步研究毛竹热物理特性提供了理论依据。     

Thermal characterization of a tropical rice soil in relation to puddling,flood-water depth and percolation rate

Effects of puddling, flood-water depth and percolation rate on the thermal properties of a tropical rice soil were studied under field and glass-house conditions. Puddling increased volumetric heat capacity (C_V), but decreased thermal conductivity (Kt), thermal diffusivity (Dt) and damping depth (D) compared to a nonpuddled soil. A percolation rate of 40 mm d⁻¹ showed higher Kt, Dt and D than zero percolation. The values of Kt, Dt and D were highest with 50 mm and lowest with 10 mm flood- water depth. The C_v did not change with different flood-water depths or percolation rates. Consequently, puddling, 40 mm d⁻¹ percolation and 50–100 mm submergence kept the maximum temperature of surface 100–150 mm soil at relatively low level under tropical conditions. These treatments also buffered soil against extreme diurnal temperature fluctuations. The time lag between maximum solar radiation and maximum temperature of submerged soil varied, on an average, between 1.2 hours at soil surface and 11.6 hours at 300 mm soil depth; which is more than that in an upland soil.     

现代黄河三角洲30cm土壤电导率与土壤水吸力关系特征初探

对在2005年4月7日—11月23日期间获得的布设于现代黄河三角洲的18个长期野外水盐观测井的30cm土层的土壤电导率和土壤水吸力数据进行研究,结果表明：整个观测期内30cm土层的土壤电导率与土壤水吸力相关性不显著;2005年4月7日—6月6日期间（即植物生长初期、农作物播种期）,仅DZ05、DZ16和DZ17号观测井土壤电导率与土壤水吸力呈显著正线性相关关系,DZ08、DZ13和DZ15号观测井土壤电导率与土壤水吸力可用曲线方程拟合;2005年9月30日—11月23日期间（植物生长末期）,DZ01、DZ02、DZ04、DZ06、DZ10、DZ12、DZ14、DZ15和DZ18号观测井土壤电导率与土壤水吸力可用曲线方程拟合,DZ07和DZ16号观测井土壤电导率与土壤水吸力呈显著负相关,DZ03号观测井土壤电导率与土壤水吸力呈显著正相关。由此可见植物生长末期是现代黄河三角洲研究野外实测土壤电导率与土壤水吸力的最佳时期。     

Effect of Altitude on Energy Exchange Characteristics of Some Alpine Medicinal Crops from Central Himalayas

To explore the conservation and cultivation of endangered alpine medicinal crops at comparatively lower altitudes, a study on variations in morphological parameters and energy exchange characteristics was conducted on five herbaceous medicinal crops from the alpines of Central Himalayas. Plants of same age were selected from the alpine medicinal crop nursery, Tungnath (3600 m), and were planted at the nurseries at 2100 and 550 m altitudes. After well acclimatization at lower altitudes, plants were examined for morphological and energy exchange studies during their active growth period. The energy balance sheet of these plant species indicates that most of the energy absorbed by the leaves dissipates by re‐radiation, transpiration and thermal conductance across leaf surfaces. All species maintained leaf temperature below the surrounding air temperature at all altitudes and therefore gained energy by convection of heat as well as by boundary layer thermal conduction. Leaf‐to‐air temperature difference, gain of energy by convection of heat and boundary layer thermal conduction was maximum at an altitude of 2100 m in all the species. Boundary layer thermal conductivity, boundary layer thickness, thermal conductivity of the leaf and therefore, total energy absorbed by the leaves of these species increase significantly with decreasing altitude. Leaf thickness significantly decreases with decreasing altitude, which in turn enhances total energy absorption (r = ?0.975, P < 0.005) of the leaves in all the species. The results indicate that all these species absorb higher amount of energy at lower altitudes, which indicates their adaptability to warm temperatures at low altitudes (up to 550 m). Therefore, these species can be cultivated at relatively lower altitudes. However, a proper agronomic methodology needs to be developed for better yields.     

不同温湿度条件下杨树人工林土壤氮矿化特征研究

为了掌握不同温度和湿度条件下杨树人工林土壤的氮矿化过程,探明土壤在干旱条件下的氮矿化特征,采用室内培养法,将含水量分别为田间持水量的20%(重度干旱处理)、40%(轻度干旱处理)和70%(对照处理)的杨树人工林表层土壤(0~10 cm),分别置于15、20、25、30℃恒温条件下进行了8周培养试验,研究不同温湿度条件下的土壤氮矿化特征。结果表明:(1)土壤净氮矿化量与温度呈极显著正相关关系(P0.01);(2)在较低温度条件下(15、20℃),不同湿度土壤净氮矿化量表现为轻度干旱重度干旱对照,而在较高温度条件下(25、30℃),培养前期的氮矿化量变化规律与低温处理一致,但至培养后期,则表现为对照轻度干旱重度干旱;(3)各种处理土壤矿质氮主要以硝态氮为主;(4)土壤电导率与土壤硝态氮含量、净氮矿化量呈极显著正相关关系(P0.01)。研究表明适度干旱能够促进土壤氮的早期矿化,但适宜的湿度更有利于土壤氮的长期矿化。     

山西省土壤热扩散率和液态水通量密度研究

为研究山西省土壤热性质的时空分布,对各地区土壤热性质进行比较并讨论不同深度土壤层热性质的差异。利用山西省11个地市气象观测站2009年5—10月的浅层土壤温度资料,采用Gao方法研究山西省土壤热扩散率和液态水通量密度。结果表明：（1）山西省的土壤热扩散率k=0.01×10^-6~5.09×10^-6m2/s和液态水通量密度W=-13.28×10^-6~26.92×10^-6m/s。（2）山西省土壤热扩散率和液态水通量密度在垂直方向上不同性。（3）在0.025m层,大同市的k值和W值都是最小的,而晋城市的k值和W值都是最大的。液态水通量密度的最大值都出现在0.025m层。     

不同耐盐植物对滨海盐土可溶性盐分运移的影响

为了揭示耐盐植物在生长期内对土壤盐分含量的影响,采用田间试验与室内分析相结合的方法,用电导率仪法测定土壤电导率,用玻璃电极法测定pH值。结果表明：种植耐盐植物对表层土壤具有明显的脱盐效果,其中柽柳对表层及0~80 cm土层的脱盐效果最好。8月份时,耐盐植物处理脱盐效果由高到低的顺序为T3>T1>T2>T4,其表层与对照相比脱盐率分别达到72.11%、52.16%、40.90%、23.63%。种植植物处理处理随时间的推移表层土壤盐分的变化趋势是先下降后上升,在12月份时,表层土壤脱盐顺序为T3>T2>T1>T4,其表层与对照相比脱盐率分别达到78.26%、71.91%、48.79%、40.09%,种植耐盐植物能够抑制土壤盐分累积,但同时也提高了土壤pH值。种植耐盐植物具有明显的降盐效果,但同时也应注意土壤碱化问题。     

A Simple Model for Predicting Daily Mean Soil Temperatures

Based on measurements in 3 different types of soil (clay, sand, peat) linear regression equations between daily air temperature (2 m) and soil temperature (2, 5, 10, 20, 50 cm depth) are calculated for all months of the growing season. The equations show a significant seasonal dependence and the best correlations in the upper 10 cm of soil. Differences depending on the type of soil are relatively small. Correction terms involving cloudiness and thermal inertia of the soil during a sudden warming or cooling period complete the prediction model. Standard deviations between predicted and measured values have been found within 1.5 K in most cases. Lastly a generally applicable method for calculating regression equations at any station is introduced. The application of this method to different sites and types of soil in Bavaria and other regions of Germany shows a good agreement with measured values.     

赤峰市松山区山坡地日光温室气温变化规律

为了解山坡地日光温室气温变化特征,提高设施农业气象服务水平,本研究对温室内外小气候因子进行了观测。采用相关分析和逐步回归的方法,对夏冬2季温室内外气温、湿度、地温和太阳辐射变化特征及室内温度预测模型进行了研究。结果表明：（1）夏冬2季室内温度、地温具有明显的日变化规律,冬季温室增温效果大于夏季,山坡地日光温室具有良好的保温效果;（2）5 cm、10 cm、20 cm地温变化幅度随土层深度的增加而减小,峰值出现随土层深度的增加而相应的滞后1 h左右;（3）日光温室室内温度与室内外小气候因子相关性较好。试验建立的夏冬2季室内温度预报模型,夏冬2季室内温度预报值绝对误差小于1℃,相对误差小于10%。     

不同干燥工艺对稻谷导热系数影响的研究

采用自然干燥(15℃)、热风干燥(45℃、55℃、65℃)、流化床干燥(45℃、55℃、65℃)对初始湿基含水率21.2%的稻谷进行降水处理,选取适当水分间隔测量稻谷导热系数和爆腰率,得到不同干燥工艺条件下的导热系数与含水率的拟合曲线、导热系数与爆腰率的拟合曲线,并对降水速率与爆腰增率、导热系数与爆腰率做相关分析。结果表明,降水速率与爆腰增率,导热系数与爆腰率都存在极显著相关性。干燥工艺影响稻谷降水速率,产生不同爆腰率,改变内部结构进而影响导热系数测量值。随爆腰率增大,导热系数呈非线性递增。流化床干燥对稻谷导热系数测量造成的影响大于薄层热风干燥。低温薄层热风干燥稻谷的导热系数最接近自然干燥处理值。     

Assessment of two parameter estimation techniques for the estimation of soil hydraulic characteristics

When Richard's flow equation was solved numerically two parameter estimation procedures were assessed for their applicability in the estimation of parameters of soil hydraulic characteristics, the water retention and hydraulic conductivity functions, and saturated hydraulic conductivity. The estimation procedures assessed were Taylor expansion and Marquardt (1963). The model simulated soil water content and pressure head profiles, obtained with the optimized estimates for the parameters from either method, agreed close with the corresponding measured profiles. Similar trends were observed for the water retention curve. The unsaturated hydraulic conductivities calculated, using the measured values in water content and pressure head agreed with those obtained using the established hydraulic conductivity functions. The results show that the techniques developed in this study were satisfactory to predict sufficiently accurate the hydraulic characteristics required to describe unsaturated flow of water in soil. The techniques appear promising, becuase the auxilliary information, soil water content, required for the estimation of hydraulic characteristics was minimal and relatively easy to collect.     

A STUDY ON HEAT AND MOISTURE STATE OF HULL LAYER FOR THERMAL INSTULATION OF A COLD STORAGE

This paper analyses the thermal moist characteristics of the hull layer beside an air layer at lower temperature in an envelope for a cold storage and presents a new method of waterproof by air layer. With test data from engineering practice, the theory on the barrier of self moisture proof at the surface sublayer of the hull layer in an attic on a cold storage is proven. The dried zone about three phase point is confirmed. It is a new knowledge for thermophysics on thermal design of a cold storage with an optimum thermal performance.     

A frequency-domain image registration algorithm using the improved polar transform

The influence of applying different heat transfer models coupled different data processing methods on determining the ground thermal properties and borehole resistance is analyzed and studied in allusion to constant heating flux method of thermal response test. Results indicate that the calculated thermal properties and borehole resistance are different when applying line heat source model and cylindrical heat source model respectively; volume specific heat barely affects the unknown thermal conductivity, but affects the borehole resistance. Three-parameter estimation has good credibility in determination of thermal properties and borehole resistance. However, the stability of three-parameter estimation on the determination of thermal diffusivity is not good. Finally, the approach of three parameters estimation coupled the line heat source model and cylindrical heat source model is proposed to determine the thermal properties and borehole resistance based on the analysis of the minimum average error on the two heat transfer models.     

基于EM38的玛纳斯县土壤剖面盐分的解译模型构建

大地电导率仪(EM38)是快速无损测定土壤盐分的有效方法。为建立新疆农田土壤EM38测试值与土壤盐分关系模型，以新疆玛纳斯县农田土壤为研究对象，利用EM38在野外实地测定土壤表观电导率，并挖掘土壤剖面进行分层采样，室内测定土壤盐分含量，据此构建基于EM38的土壤盐分解译模型。结果表明：（1）利用土壤实测盐分和EM38电导率数据，分别建立不同土壤深度下EM38垂直模式和水平模式以及两者联用的二元线性回归土壤盐分解译模型。（2）3种EM38盐分解译模型的R2随着土壤深度增加而增加，并且在土壤深度小于20 cm时，垂直模式的解译精度大于水平模式，深度大于20 cm后，解译精度则刚好与之相反。（3）二元线性回归模型的解译精度明显优于一元线性回归模型。本研究所构建的EM38土壤盐分解译模型，将为绿洲农田土壤盐分快速调查和动态监测提供可靠的反演参数和模型。     

不同种植密度对寒地水稻浅土层热效应的影响

为了提高人们对寒地水稻浅土层热效应特征变化的认知度。试验在大田条件下,以‘空育131’为试验材料,设置行株距30×8 cm (D₁)、30×10 cm (D₂)、30×12 cm (D₃)、30×14 cm (D₄)、30×16 cm (D₅) 5个密度水平,分析不同种植密度对浅土层热效应的影响。结果表明,各土层温度在抽穗期达最高值,灌浆后开始下降,且温差缩小,其中以10 cm土层温度稳定性最高。受种植密度影响,高密度处理下土温白天增温快,夜间最低,昼夜温差大,最高日平均温度出现的早,其中D₁、D₂处理在10 cm、15 cm土温变化上几乎同步。相比之下,各土层T_max、T_min出现时间随土层的加深而向后推迟,生育期内T_avg、T_max、T_min与气温极显著正相关,而T_max-_min则随密度的增加有减小的趋势,主要表现在分蘖期和成熟期,且作用效果随密度增加而增大。产量以D₂处理最高,表现为9.27 t/hm ²,较D₁、D₅处理增幅13.5%~14.6%。说明适宜密度条件能够实现对浅土层热效应的科学调控,并获得产量的提高。     

Soil compaction around a small penetrating cylindrical body and its consequences

Penetrometer probes as well as roots and earthworms push soil particles (grains or small aggregates) radially during penetration and/or thickening due to growth. By this, the adjacent soil within a concentric layer is compacted. The degree of compaction depends on soil texture and soil physical properties that are influenced by soil moisture status. In the present study an estimate of the mean but constant increase of the initial bulk density and of the outer radius of this concentrically compacted zone, which are interdependent, is given. For instance, an increase from 1.2 g/cm³ to 1.6 g/cm³ yields a compacted zone of radius 0.5 mm when a body of radius 0.25 mm penetrates into a soil. This estimation is less laborious, but also less exact than that of Dexter (1987: Comparison of soil around roots. Plant Soil, 97: 401–406). This study shows that the distance between adjacent penetrations, when measuring resistance to penetration, should be ⪖ 10 times the probes radius. It is moreover supposed that the compaction produced by roots and earthworms makes it easier for them to anchor within (loose) soil. However, it possibly diminishes infiltration and exchange of soil solution.     

不同油葵种植方式对银北灌区盐碱地土壤温度、含水率和电导率的影响

为了探究油葵不同种植方式对盐碱地土壤水、热、盐分布状况的影响,以平播（T1）为对照,开展了半膜平播（T2）、半膜平播+膜间覆秸秆（T3）、起垄沟播（T4）、起垄沟播+沟覆秸秆（T5）、垄膜沟播（T6）、垄膜沟播+沟覆秸秆（T7）等6种种植方式对油葵田土壤温度、水分和电导率的影响研究。结果表明：与对照相比,不同种植方式均提高了早上7:00时5cm深度的土温,但油葵花期土壤增温效果明显弱于苗期,垄膜沟播种植方式更有利于减缓地 表5cm深度土温的剧烈变化。与对照相比,在油葵苗期,T7和T6的0~20cm土层土壤含水率分别提高了6.30%和5.01%,20~40cm土层分别提高了6.00%和3.38%,在油葵开花期,土壤含水率较对照提高幅度有所降低。与播种前0~20cm土层土壤电导率相比,T6在苗期和开花期均有所下降,其中开花期下降了33.81%,T7在苗期略有增加,在开花期则略有下降,其他处理在苗期增加幅度较大。因此,在银北灌区油葵生产中,垄膜沟播是一种适宜的油葵种植方式。     

黄土高原南部水平梯田的土壤水分特征分析

以淳化试区的水平梯田为系统研究对象,休闲坡地为对照,对其剖面土壤水分变化进行动态监测。发现由于作物对梯田土壤水分的吸收利用,以及蒸发散的原因,导致水平梯田的土壤贮水量比休闲坡地小。梯田土壤水分季节变化分为蓄墒期、快速失墒期、补充期和缓慢消耗失墒期4个时期,其剖面分为剧变、活跃、相对稳定4个层次。降水、地形地貌部位、土地利用方式以及梯田宽度与种植年限均对土壤含水量有着不同程度的影响。观测期间,除在梯田表层土壤含水量出现低于有效水的现象外,其它层次都在有效水范围内,无论在丰水、枯水年,梯田土壤中的有效水或中效、易效水都可以满足作物的生长和非生长耗水的需求。     

滴灌条件下富士苹果树茎流速率变化规律研究

摘 要：旨在了解矮砧密植富士苹果树体内茎流速率变化规律,为其制定合理的旱作节水灌溉制度提供理论基础。利用热扩散式探针法实时采集树体茎流速率数据,结合自动气象站监测所得各气象因子数据,设计不同灌水下限滴灌试验,进行气象因子等对茎流速率影响的试验研究。富士苹果树在4月份茎流速率最低平均值为2.07 mL/(cm2?h)],到了6—7月份最大,平均值为9.56 mL/(cm2?h)];生育期内茎流速率有明显昼夜变化规律,在晴天时变化规律呈单峰曲线,阴天时变化较平缓,多云天气时呈多峰曲线变化趋势。茎流速率变化规律与太阳辐射强度、大气温度和土壤温度变化均呈极显著正相关,相关系数分别为：0.9746、0.9389、0.9119;与大气湿度为显著负相关性;相关系数为-0.7526;茎流速率与土壤水分相关性不显著,但是降低土壤含水量会造成树体茎流速率的降低。富士苹果树干茎流速率与各气象因子间相关性由高到低排序为：太阳辐射强度＞大气温度＞土壤温度＞大气湿度＞土壤水分。以茎流速率为因变量,各个气象因子为自变量,经逐步回归线性分析得出茎流速率与太阳辐射强度和大气温度之间的回归方程：Y=-8.81+0.013X1+0.52X2。太阳辐射强度是影响树体茎流速率即蒸腾耗水的直接因素。