EM38 for volumetric soil water content estimation in the root-zone of deep vertosol soils

Electromagnetic induction sensors, such as EM38, are used widely for monitoring and mapping soil attributes via the apparent electrical conductivity (EC_a) of the soil. The sensor response is the depth-integrated combination of the depth-response function of the EM38 and ‘local’ electrical conductivity (EC_az) at depth. In deep, Vertosol soils, assuming the instrument depth-response function is not perturbed by the soil and where volumetric moisture content at depth (θ_v(z)) dominates EC_az, EM38 should be capable of predicting average moisture content without recourse to mathematically complicated, and unstable profile inversion processes. Firstly a multi-height EM38 experiment was conducted over deep Vertosol soils to confirm the veracity of the EM38 depth-response function and test the concomitant hypothesis of the EM38 response being an integrated (i.e. additive) combination of depth-response function and θ_v(z). Secondly, depth profiles of moisture content were used to calibrate the EM38 to infer average θ_v(z) within the ‘root-zone’ of crop plants—here taken to be surface—0.8 m and surface—1.2 m. EM38 calibration was performed using soil samples acquired from both extracted cores and excavated pits. Mathematical summation of measured θ_v(z) from sectioned cores and the known depth-response function of the EM38 was found to explain 99% and 97% of the variance in measured EC_a for horizontal and vertical dipole configurations at multiple sensor heights above the ground. Average θ_v from surface to 0.8 m () and surface to 1.2 m () explained only 37% and 46% of the variance in on-ground EC_a for vertical dipole configuration measurements compared to 55% and 56% of the variance for horizontal dipole configuration. In a separate validation experiment, the shape of the vertical moisture profile proved highly influential in determining the ability of the calibration equations to infer underlying average moisture content, especially where the depth profile shapes differed between sensor calibration and subsequent field validation (for example following rainfall or irrigation).     

覆盖方式对干热河谷区枣园土壤温度和树体光合特性及果实品质的影响

为研究不同覆盖方式对枣园土壤温度、树体光合特性及果实品质的影响,设置清耕(CK)、人工种植花生(T_1)、黑麦草(T_2)、树枝秸秆碎屑(T_3)、人工种植黄豆(T_4)、黑膜(T_5)6种土壤管理模式处理,采用主成分分析综合评价,筛选最佳土壤管理方式。结果表明:7月份,与CK相比,各处理对不同土层土壤温度均有明显的降温作用,在5 cm土层,T_4分别较T_2、T_5、CK降低2.87%、10.96%、12.77%,而T_5较明显地增加土层土壤温度。不同覆盖方式均不同程度地提高叶片净光合速率,T_4处理最为显著,在6、7、8月份较CK分别提高21.67%、40.05%、36.08%;且T_4处理对维生素含量、可溶性糖含量、枣果横径的影响显著高于其他处理,较CK分别增加25.00%、10.70%、9.45%。对16个指标进行相关性与主成分分析,提取3个主成分后的综合分析结果表明,不同覆盖方式对枣树的效果为T_4T_1T_5T_3T_2CK。综上所述,采用人工种植黄豆覆盖处理是促进甘肃白龙江干热河区枣园最佳的土壤管理方式。     

Imaging the electrical conductivity of the soil profile and its relationships to soil water patterns and drainage characteristics

Soil water content (θ) measurement is vital for accurate irrigation scheduling. Electromagnetic induction surveys can be used to map spatial variability of θ when other soil properties are uniform. However, depth-specific θ variations, essential for precision irrigation management, have been less investigated using this method. A quasi-2-dimensional inversion model, capable of inverting apparent soil electrical conductivity (EC_a) data to calculate estimates of true electrical conductivity (σ) down the entire soil profile, was developed using EC_a data collected by a multi-coil Dualem-421S sensor. The optimal relationships between σ and volumetric water content (θv) were established using all coil arrays of the Dualem-421S, a damping factor of 0.04, an initial model of 35 mSm^?1, and with ten iterations (R²?=?0.70, bias?=?0.00 cm³cm^?3, RMSE?=?0.04 cm³cm^?3). These relationships were then used to derive soil profile images of these properties, and as expected, θv and σ follow similar trends down the soil profile. The derived soil profile images for θv have potential use for irrigation scheduling to two EC_a-derived soil management zones under a variable rate irrigation system at this case study site. They reflect the intrinsic soil differences that occur between texture, texture transitions and drainage characteristics. The method can also be used to guide placement of soil moisture sensors for in-season monitoring of spatio-temporal variations of θv. This soil imaging method showed good potential for predicting 2D depth profiles of soil texture, moisture and drainage characteristics, and supporting soil, plant and irrigation management.

     

两种高质牧草不同生育期光合生理日变化及光响应特征

于2010年5月25日(拔节、分枝期)、7月6日(抽穗、结荚期)、8月25日(开花期)晴朗天气,采用LI-6400便携式光合作用测定系统对新引1号东方山羊豆和柳枝稷各项光合生理生态指标进行了测定.结果表明:(1)新引1号东方山羊豆净光合速率(Pn)日变化呈双峰曲线,存在“光合午休”现象;分枝期Pn、光能利用效率(LUE)、水分利用效率(WUE)日均值高于结荚期,而结荚期的叶温(Tl)、蒸腾速率(Tr)、气孔导度(Gs)、胞间CO2浓度(Ci)日均值高于分枝期.(2)柳枝稷的Pn日变化呈单峰曲线,拔节期Pn、Tr日均值高于抽穗期,开花期最低;WUE与Ci日均值在开花期最高,拔节期次之,抽穗期最小;Tl、LUE日均值在抽穗期最高,拔节期次之,开花期最小.(3)Pn与Tr、Gs、叶片气孔限制值(Ls)、光合有效辐射(PAR)具有极显著正相关关系,与Ci呈极显著负相关;Tr与Gs、叶温下蒸汽压亏缺(Vpdl)、气温(Ta)、Tl、PAR均呈极显著正相关关系,与大气CO2浓度(Ca)呈显著负相关;Tl、Gs与PAR呈极显著正相关.(4)通过光响应曲线的绘制及相关生理指标的计算,结合相关评价标准,得出柳枝稷为阳生植物,而新引1号东方山羊豆为耐荫植物,且柳枝稷比新引1号东方山羊豆对光环境的适应性强.     

博斯腾湖西岸湖滨带不同植被类型土壤剖面盐分特征分析

以博斯腾湖西岸湖滨带为研究区,通过野外调查采样和室内实验分析,运用聚类分析、主成分分析和相关分析等方法对5种不同植被类型土壤(柽柳地、芦苇地、裸地、杨树地、辣椒地)剖面盐分类型、含盐量变化特征及盐分离子组成特征进行分析。结果表明:土壤剖面盐分类型可以划分为表聚型、震荡型、均匀型3类。柽柳地与裸地的土壤剖面类型为表聚型,其土壤剖面变异系数为61.28%,表聚系数是底聚系数的4.45倍,表层聚集现象严重;芦苇地的土壤剖面盐分类型为震荡型,变异系数为30.05%;辣椒地和杨树地的土壤剖面盐分类型为均匀型,变异程度最小仅为表聚型剖面的47.65%。5种不同植被类型土壤剖面平均盐质量分数呈现柽柳地裸地芦苇地辣椒地杨树地,其中柽柳地平均盐质量分数为2.67g/kg,与杨树地土壤平均盐质量分数之比为2.45。5种不同植被类型土壤剖面盐分组成以Na~++K~+、SO_4~(2-)、Cl~-为主,阳离子平均质量分数呈现Na~++K~+Ca~(2+)Mg~(2+),阴离子中总体表现SO_4~(2-)Cl~-HCO-3,盐分状况的主要特征因子为Cl~-、SO_4~(2-)、Na~++K~+、总盐(St),土壤剖面盐分以氯化钾钠盐和硫酸钾钠盐为主,Cl~-与Na~++K~+相关系数为0.941,SO_4~(2-)与Na~++K~+相关系数为0.884;盐分状况因子Cl~-、SO_4~(2-)、Na~++K~+、St与电导率均呈显著正相关(P0.05),电导率与Na~++K~+回归拟合效果较好,拟合关系式为y=0.039 5x+0.218 6,R2=0.966 7,P0.05。     

2.4GHz无线信号在苹果园中的衰减模型

为解决苹果园中无线传感器网络的规划和部署问题,研究2.4GHz无线信道在苹果园中的传播特性。在山东省肥城市普通的苹果园进行实地试验。选取对信号传播影响最大的一列果树,发射天线固定在两棵树之间发射信号,分别测量6个高度18个位置点的接收信号强度和丢包率。回归分析结果表明:无论发射天线多高,不同水平高度上的接收信号强度衰减均符合对数路径损耗模型,拟合的决定系数为0.927~0.987。发射天线高度不变时,衰减系数n值能用接收天线高度的二次函数曲线拟合,拟合的决定系数为0.71~0.89;模型参数A和接收天线高度符合线性关系,拟合的RMSE为0.2~1.2。建立以发射天线高度、接收天线高度和传播距离为参数的衰减模型并进行验证试验,结果表明:RMSE为2~5,94%的R2值大于0.9,预测模型能较好的估算收发天线高度不同时的信号强度损耗。     

低温胁迫时间对4种幼苗生理生化及光合特性的影响

以盐肤木(Rhus chinensis)、假连翘(Duranta repens)、老鸭嘴(Thunbergia erecta)和葛藤(Pueraria lobata)4种幼苗为试验材料,研究了人工模拟下的低温胁迫环境(6 ℃)对幼苗叶片生理生化及光合特性的影响。结果表明:(1) 随低温胁迫的延长,假连翘幼苗的叶绿素含量先升后降,其余3种幼苗持续下降,低温解除后均显著回升;4种幼苗的脯氨酸含量持续上升或波动;葛藤幼苗的可溶性蛋白质含量先升后降,其余幼苗显著上升, 且低温解除后有所增加;4种幼苗叶片可溶性糖含量以及丙二醛含量呈增加趋势,SOD活性持续上升或先升后降。低温解除后,盐肤木幼苗的SOD活性略有上升,其余幼苗显著下降。(2) 随低温胁迫的延长,4种幼苗的净光合速率(P_n)、气孔导度(G_s)、蒸腾速率(T_r)均持续下降,假连翘的胞间CO₂浓度(C_i)持续上升,其余幼苗先降后升。低温解除后4种幼苗叶片P_n、G_s、T_r均有不同程度的回升,C_i有不同程度的下降。低温胁迫和恢复48 h期间,4种幼苗的脯氨酸、可溶性糖、可溶性蛋白质含量的增加和SOD活性的稳定或增加,减轻了幼苗叶片细胞的膜脂过氧化程度, 维持了细胞膜的完整性,是幼苗对低温胁迫适应性反应的重要调节机制。恢复48 h时的P_n、G_s和Tr均有不同程度的回升,C_i有不同程度的下降,说明4种幼苗有一定的抗寒能力。(3)用主成分分析法分别对生理生化指标和光合生理指标进行分析,均得出4种幼苗的抗寒性顺序为葛藤>盐肤木>老鸭嘴>假连翘,这一结果可为采矿石废弃地生态恢复的植物筛选提供科学依据。     

Using high resolution UAV thermal imagery to assess the variability in the water status of five fruit tree species within a commercial orchard

This paper deals with the assessment of heterogeneity in water status in a commercial orchard, as a prerequisite for precision irrigation management. Remote sensing-derived indicators could be suitable for mapping water stress over large areas, and recent studies have demonstrated that high resolution airborne thermal imagery enables the assessment of discontinuous canopies as pure tree crowns can be targeted, thus eliminating the background effects. Airborne campaigns were conducted over a drip-irrigated commercial orchard in Southwestern Spain composed of five different orchard tree crops. An unmanned aerial vehicle with a thermal camera onboard was flown three times during the day on 8 July 2010, at 9, 11 and 13 h (local time). Stem water potential was measured at the same time of the flights. In some irrigation units, irrigation was stopped prior to the measurement date to induce water deficits for comparative purposes. Several approaches for using the thermal data were proposed. Daily evolution of the differential between canopy and air temperature (T _c  ? T _a ) was compared to tree water status. The slope of the evolution of T _c  ? T _a with time was well correlated with water status and is proposed as a novel indicator linked with the stomatal behavior. The Crop Water Stress Index (CWSI) was calculated with the temperature data from the 13.00 h flight using an empirical approach for defining the upper and lower limits of T _c  ? T _a . The assessment of variability in water status was also performed using differences in relative canopy temperatures. Ample variability was detected among and within irrigation units, demonstrating that the approach proposed was viable for precision irrigation management. The assessment led to the identification of water-stressed areas, and to the definition of threshold CWSI values and associated risks. Such thresholds may be used by growers for irrigation management based on crop developmental stages and economic considerations.     

黄瓜和黑籽南瓜对肉桂酸及亚低温交叉胁迫的应答差异

为探索肉桂酸(Cinnamic acid,CA)和亚低温交叉胁迫对黄瓜和黑籽南瓜生理代谢的影响,对两种瓜类作物的水分代谢与光合作用受到CA及亚低温交叉胁迫的应答差异进行研究。结果表明:CA和亚低温单独胁迫降低了叶片的总含水量、自由水含量、自由水/束缚水、净光合速率(PN)、蒸腾速率(Tr)和气孔导度(gs),提高了叶片的渗透势;抑制了根系干物质的分配比例,增加了地上部干物质的分配比例;增加了瞬时水分利用效率(WuE)和潜在水分利用效率(WuEi),抑制了叶面积(LA)的生长速率。CA和亚低温交叉胁迫对2种作物生理活动的影响与其单独胁迫一致,交叉胁迫的影响最大,其次是亚低温单独胁迫,CA单独胁迫影响最小,黄瓜受到胁迫的程度明显高于黑籽南瓜。总之,CA和亚低温交叉胁迫对黄瓜的毒害较单一因子明显,黄瓜抵御CA和亚低温胁迫的能力明显低于黑籽南瓜。     

Relations Between Photosynthetic Parameters and Seed Yields of Adzuki Bean Cultivars (Vigna angularis

The study comparatively examined the leaf photosynthetic capacities of different adzuki bean cultivars, high-yield 2000-75 and Jihong 9218, and low-yield Hongbao 1 and Wanxuan 1 from flowering to ripening. It showed that after flowering, the leaves of the cultivars gradually aged, the leaf chlorophyll (Chl.), soluble protein (SP) contents, net photosynthetic rates (P_n), transpiration rates (T_r) and stomatal conductance (G_s) of the cultivars tended to decline, but the leaf intercellular CO₂ concentration (C_i) of the cultivars tended to rise. The leaf photosynthetic capacities of the cultivars decreased gradually from the lower to the upper nodes. The dry seed yields of the cultivars were positively correlated with their leaf Chl., SP, P_n, and T_r and G_s, and negatively associated with their leaf C_i. At the late growth stages, the high-yield cultivars maintained higher leaf Chl. contents, SP contents, P_n, T_r, and G_s than the low-yield cultivars, indicating that leaf photosynthetic capacity was one of important yield-affecting factors of adzuki bean. Therefore, it was important for a crop at the crucial stage of yield formation to maintain a high leaf chlorophyll content and a high leaf photosynthetic capacity and delay leaf aging.     

Field-scale validation of an automated soil nitrate extraction and measurement system

One of the many gaps that needs to be solved by precision agriculture technologies is the availability of an economic, automated, on-the-go mapping system that can be used to obtain intensive and accurate ‘real-time’ data on the levels of nitrate nitrogen (NO₃–N) in the soil. A soil nitrate mapping system (SNMS) has been developed to provide a way to collect such data. This study was done to provide extensive field-scale validation testing of the system’s nitrate extraction and measurement sub-unit (NEMS) in two crop (wheat and carrot) production systems. Field conditions included conventional tillage (CT) versus no tillage (NT), inorganic versus organic fertilizer application, four soil groups and three points in time throughout the season. Detailed data analysis showed that: (i) the level of agreement, as measured by root mean squared error (RMSE), mean absolute error (MAE) and coefficient of efficiency (CE), between NEMS soil NO₃–N and standard laboratory soil NO₃–N measurements was excellent; (ii) at the field-scale, there was little practical difference when using either integer or real number data processing; (iii) regression equations can be used to enable field measurements of soil NO₃–N using the NEMS to be obtained with laboratory accuracy; (iv) future designs of the SNMS’s control system can continue to use cheaper integer chip technology for processing the nitrate ion-selective electrode (NO₃ ⁻–ISE) readings; and (v) future designs of the SNMS would not need a soil moisture sensor, ultimately saving on manufacturing costs of a more simple system.     

A portable soil nitrogen detector based on NIRS

As one of the most important soil nutrient components, soil total nitrogen (TN) content needs to be measured in precision agriculture. A portable soil TN detector based on the 89S52 microcontroller was developed, and a Back Propagation Neural Network (BP-NN) estimation model embedded in the detector was established using near-infrared reflectance spectroscopy with absorbance data at 1550, 1300, 1200, 1100, 1050, and 940 nm wavelengths. The detector consisted of two parts, an optical unit and a control unit. The optical unit included six near-infrared lamp-houses, a shared lamp-house drive circuit, a shared incidence and reflectance Y-type optical fiber, a probe, and a photoelectric sensor. The control unit included an amplifier circuit, a filter circuit, an analog-to-digital converter circuit, an LCD display, and a U-disk storage component. All six absorbance data as inputs were used to calculate soil TN content by means of the estimation model. Finally, the calculated soil TN content was displayed on the LCD display and at the same time stored in the U-disk. A calibration experiment was conducted. The soil TN content correlation coefficient (R ²) of the BP-NN estimation model was 0.88, and the validation R ² was 0.75. This result indicated that the developed detector had a stable performance and a high precision.     

生物质种类和添加量对肥液灌溉土壤入渗特征和养分运移的影响

目的 探究添加不同生物质和添加量对肥液灌溉土壤入渗特征与养分运移的影响，为提升肥液灌溉效率提供理论依据。方法 以生物炭(BC)、咖啡渣(CF)和甘蔗渣(SC)作为生物质添加材料，设置4个添加量(质量分数)水平T₁(0.5%)、T₂(1.0%)、T₃(1.5%)、T₄(2.0%)。测量肥液在不同生物质添加土壤中的运移特征及养分分布，评估不同生物质添加对土壤结构的影响。结果 3种生物质对湿润锋运移与土壤累积入渗量抑制效果均表现为SC>CF>BC，各处理组内抑制效果随生物质添加量增加有所提升；和CK组相比, SCT₄、CFT₄和BCT₄组湿润锋运移距离分别降低了38.33%、37.00%和34.00%；SCT₄、CFT₄和BCT₄组土壤累积入渗量分别降低了31.01%、30.00%和26.60%。和CK组相比，肥液灌溉下3种生物质添加均能提升土壤中3种主要无机养分，且随生物质添加量增加土壤肥力提升；3种生物质对土壤硝态氮截留总体表现为BC>CF>SC，其中，BCT₄、CFT₄和SCT₄组的土壤硝态氮含量分别提升了74.32%、56.00%和51.00%；3种生物质对土壤速效磷截留总体表现为CF>SC>BC，其中，CFT₄、SCT₄和BCT₄组的土壤速效磷含量分别提升了140.70%、139.20%和30.25%；3种生物质对土壤速效钾截留总体表现为CF>BC>SC，其中，CFT₄、BCT₄和SCT₄组的土壤速效钾含量分别提升了143.87%、126.85%和104.03%。结论 3种生物质对肥液入渗均有抑制效果，其中，生物炭效果最佳；3种生物质对肥力均有截留效果，生物炭对硝态氮截留效果最佳，咖啡渣对速效磷与速效钾截留效果最佳。     

干湿季节下基于遥感和电磁感应技术的塔里木盆地北缘绿洲土壤盐分的空间变异性

土壤盐渍化问题是制约干旱半干旱区植被生长最主要的生态环境地质问题,也是影响绿洲农业生产的障碍性问题。而将遥感与近感技术相结合,是当前评价、监测及预报土壤盐渍化程度的先进方法。以新疆塔里木盆地北缘的渭干河-库车河三角洲绿洲为例,以遥感数据和解译后的电磁感应数据为基础数据源,利用解译后的数据结合GIS和地统计学知识以及野外实测所得到的土壤电导率和盐分资料,分别采用泛克里格(Universal Kriging)、光谱指数回归(Spectral Index Regression)和回归残差泛克里格(Regression-Universal Kriging)3种方法研究了该地区两个关键季节(干季和湿季)土壤盐分的空间变异特征。研究结果表明:研究区的土壤浸提液电导率EC_1:5和土壤盐分呈现显著相关,可以用EC_1:5来代替土壤的全盐量进行分析;电磁感应仪(EM38)所测各季节土壤表观电导率与EC_1:5的相关系数均达到1%显著水平,以表观电导率垂直读数(EM_V) 和水平读数(EM_H)为自变量的多元回归模型拟合效果较好;研究区各季节的表层土壤电导率的空间分布均表现为强相关性,说明土壤采样点间的内部结构性良好,采用能够充分考虑到干旱区表层土壤电导率空间变异的尺度依赖性的球状套合模型,能够更好的拟合土壤表观电导率的空间结构;经过精度比较,回归残差泛克里格法为最优预测方法,这表明将遥感和电磁感应技术相结合,能够有效的提高预测与评估土壤盐分空间分布的精度,为精确地进行土壤盐分预测以及土壤次生盐渍化的防控提供了一定的依据。     

The Effects of Farmyard Manure and Mulch on Soil Physical Properties in a Reclaimed Coastal Tidal Flat Salt-Affected Soil

Careful soil management is important for the soil quality and productivity improvement of the reclaimed coastal tidal flat saline land in northern Jiangsu Province, China. Farmyard manure（ FYM） and mulch applications, which affect soil characteristics and plant significantly, are regard as an effective pattern of saline land improvement. As a conventional management in the study region, FYM and mulch are used for the amendment of the new reclaimed tidal flat regularly, but little is known about their effects on soil physical properties functioning. A study was conducted on a typical coastal tidal flat saline land, which was reclaimed in 2005, to evaluate the effects of FYM, polyethylene film mulch（PM）, straw mulch（SM）, FYM combined with PM（FYM＋PM）, FYM combined with SM（FYM＋SM）, on soil hydraulic properties and soil mechanical impedance. CK represented conventional cultivation in study area without FYM and mulch application and served as a control. The experiment, laid out in a randomized complete block design with three replications, was studied in Huanghaiyuan Farm, which specialized in the agricultural utilization for coastal tidal flat. Result showed that capillary water holding capacity（CHC）, saturated water content（SWC）, saturated hydraulic conductivity（ Ks） and bulk density（BD）, cone index（CI） were affected significantly by the FYM and mulch application, especially in the 0-10 cm soil layer. FYM and mulch management increased CHC, SWC and Ks over all soil depth in the order of FYM＋SM〉FYM＋PM〉FYM〉SM〉PM〉CK. With the contrary sequence, BD and CI decreased significantly; however, FYM and mulch application affected BD and CI only in the upper soil layers. CHC, SWC and Ks decreased significantly with the increasing of soil depth, BD and CI, and a significant liner equation was found between CHC, SWC, Ks and BD, CI. With the highest CHC（38.15%）, SWC（39.55%）, Ks（6.00 mm h-1） and the lowest BD（1.26 g cm-3） and CI（2.71 MPa）, the combined man     

秸秆和植被覆盖对江苏滨海盐土土壤盐分变化的影响

研究秸秆覆盖和植被（田菁）覆盖条件下滨海盐土土壤水盐的动态变化规律,为沿海滩涂盐碱地脱盐改良提供依据。本研究以含盐量6.98 g·kg^-1的滨海盐土为研究对象,设置秸秆覆盖和种植田菁2种覆盖处理,以裸地为对照,研究不同覆盖处理对滨海盐土土壤含水量和土壤盐分动态变化的影响。结果表明：秸秆覆盖下的土壤含水量（27.58%）显著高于田菁覆盖（26.70%）和裸地（26.61%）,后两者差异未达显著水平。处理1年后0~20、20~40 cm土层的秸秆覆盖、田菁覆盖和裸地不同处理间土壤含盐量的差异均达显著或极显著水平;秸秆覆盖处理的脱盐率为田菁覆盖处理的2倍。回归分析表明裸地和田菁覆盖下土壤盐分含量与累积降雨量的关系可用二次多项式拟合,田菁覆盖下的淋洗方程（EC_a/EC_i与D_w/D_s间的关系）可用三次多项式拟合;而秸秆覆盖条件下土壤盐分含量与累积降雨量的关系、淋洗方程均表现为指数函数关系y=ae^bx（P<0.01）。秸秆覆盖条件下滨海滩涂0~40 cm土层脱盐80%需要386.8 mm的累积降雨量。结果表明秸秆和植被覆盖技术在江苏滨海盐土可获得较好的脱盐效果,具有较好的应用前景。     

广西猫儿山不同海拔常绿树种和落叶树种光合速率与氮的关系

分析广西猫儿山不同海拔常绿和落叶树种的光合作用-氮关系,探讨光合氮利用效率(PNUE)是否受到叶片习性和海拔的影响。落叶树种的PNUE都显著高于常绿树种,这与前者有较低的比叶重(LMA)和较高的单位叶重光合速率(A_mass)、氮含量和气孔导度(g_s)有密切关系。高海拔树种的PNUE显著低于中低海拔树种的PNUE,这与前者较高的LMA和较低的A_mass和g_s相关。PNUE和相关的叶片特征的主成分分析表明常绿-落叶树种和低海拔-中海拔-高海拔树种的分布是一个自然过渡的过程。此外,PNUE与土壤碳:氮比没有显著相关性,但与年均温正相关,这表明温度气候是调节PNUE沿海拔变化的主要环境因素。因此,这种叶片习性和温度气候调节的PNUE变化可能是调节猫儿山常绿树种沿海拔形成双峰分布的一种机制。     

Evaluation of a wireless infrared thermometer with a narrow field of view

Many agricultural studies rely on infrared sensors for remote measurement of surface temperatures for crop status monitoring and estimating sensible and latent heat fluxes. Historically, applications for these non-contact thermometers employed the use of hand-held or stationary industrial infrared thermometers (IRTs) wired to data loggers. Wireless sensors in agricultural applications are a practical alternative, but the availability of low cost wireless IRTs is limited. In this study, we designed prototype narrow (10°) field of view wireless infrared sensor modules and evaluated the performance of the IRT sensor by comparing temperature readings of an object (T_obj) against a blackbody calibrator in a controlled temperature room at ambient temperatures of 15 °C, 25 °C, 35 °C, and 45 °C. Additional comparative readings were taken over plant and soil samples alongside a hand-held IRT and over an isothermal target in the outdoors next to a wired IRT. The average root mean square error (RMSE) and mean absolute error (MAE) between the collected IRT object temperature readings and the blackbody target ranged between 0.10 and 0.79 °C. The wireless IRT readings also compared well with the hand-held IRT and wired industrial IRT. Additional tests performed to investigate the influence of direct radiation on IRT measurements indicated that housing the sensor in white polyvinyl chloride provided ample shielding for the self-compensating circuitry of the IR detector. The relatively low cost of the wireless IRT modules and repeatable measurements against a blackbody calibrator and commercial IR thermometers demonstrated that these wireless prototypes have the potential to provide accurate surface radiometric temperature readings in outdoor applications. Further studies are needed to thoroughly test radio frequency communication and power consumption characteristics in an outdoor setting.     

Effects of salinity on the soil microbial community and soil fertility

Saline area is an important reserve resource of arable land, however, the effects of soil microorganisms on the soil fertility in saline coastal ecosystems remain poorly understood. The salinity effects on soil microorganisms, nutrient availabilities and their relationships were studied in soils along a salinity gradient. A total of 80 soil samples were collected from 16 sites at four salinity levels(non-saline soil, salt content1 g kg–1; low salinity soil, salt content=1–2 g kg–1; middle salinity soil, salt content=2–4 g kg–1; high salinity soil, salt content4 g kg–1). The results showed that the salinity increased soil pH and exchangeable Na percent, but decreased soil organic matter, soil exchangeable K, and soil microbial biomass. Both the abundance and community composition of soil bacteria and fungi were significantly different between the non-saline and the saline soils. The predominant genera of soil bacteria(Planctomyces and Archangium, positive for carbon fixation) and fungi(Hydropisphaera, efficient in lignin degradation) changed with the increasing soil salinity and the decreasing soil organic matter. In summary, soil salinity changed the abundances of soil bacterial, fungal, and arbuscular mycorrhizal communities and, subsequently, affected their function in saline coastal ecosystems.     

A mobile lab-on-a-chip device for on-site soil nutrient analysis

In this paper, a mobile sensor for on-site analysis of soil sample extracts is presented. As a versatile tool for scanning ion concentrations in liquid samples, it especially allows the analysis of NO₃, NH₄, K and PO₄. The sensor mainly consists of a microfluidic chip in which the sample ions are separated in an electric field (capillary electrophoresis) and the individual ion concentrations are detected by a conductivity measurement. For the adaption of the device to field conditions, two major concerns were addressed. Firstly, nano-porous material was used as a barrier between the sample container and the analysis channel of the microfluidic chip. This prevents pressure driven leakage of the sample into the chip due to non-horizontal orientation of the device. Secondly, a new method for the injection of the sample into the chip was used. It reduces the number of fluidic connections between chip and operation device to three instead of the commonly used four connections. The sensor performance was tested on multi-ion solutions with calibration series for NO₃, NH₄, K and PO₄. For the first on-site test, a quick soil nutrient extraction procedure with water was used. The sensor data was compared to standard laboratory results. The potential of the sensor for soil nutrient analysis is discussed together with required improvements of the sensor performance and of the nutrient extraction procedure.