Spectral multichannel monitoring of radiation within a mature mixed forest

A multi-sensor system is described based on fiber optic technology and a diode array spectrometer for near-simultaneous measurement of spectral photon fluence rates (PFR) in the range of 360 nm to 1020 nm with a resolution of 0.8 nm, within a mature Norway spruce ( Picea abies [L.] Karst.) - European beech ( Fagus sylvatica L.) stand. 126 space-integrating spherical sensors, deployed in a regular grid above and within the canopy and on the forest floor, are sequentially connected to the spectrometer by means of fiber optics. About 1 s per sensor is needed to collect spectral data, store them on hard disk and move the channel multiplexer to the next fiber optic position. Data thus obtained serve to determine vertical profiles of wavelength-dependent photon extinction, especially for spectral ratios and wavebands, characterization of phenological stages, analyses of time series, and meteorological influences such as solar altitude and cloud cover. First measurements during leaf fall 2004 show a non-linear relation of the red/far-red ratio (R/FR) with relative photosynthetic PFR (PPFR (rel)). An analysis of relative PFR (PFR (rel)) quantifies the frequency of penumbral sunfleck occurrence and the fraction of incoming radiation on the forest floor. In-canopy measurements of daily means of PPFR (rel) and R/FR indicate that leaf unfolding and leaf fall can be described by a single sensor, independent of its vertical location within the canopy.     

Some observations on the spectral distribution characteristics of short-wave radiation within Pinus radiata D. Don canopies

Abstract. Measurements of the photosynthetic photon flux density (400–700 nm) and of the spectral distribution of photon flux density across the 370–800 nm waveband, were made under both clear and overcast sky conditions above and at various positions within two Pinus radiata canopies of different stocking but similar leaf area indices. The spectra obtained for the daylight conditions (i.e. above forest canopy) were generally similar to those published previously. The spectra for shadelight within the forest canopy showed no blue peak which was characteristic of previously reported measurements which were restricted to the diffuse radiation component. There was almost neutral absorption within the 400–700 nm waveband, and typical lower attenuation in the 700–800 nm waveband. The blue: red ratio was largely unchanged by either canopy type or sky conditions and varied between 0.57 and 0.81. The red: far-red ratio in shadelight was between 0.22 and 0.41 under clear sky and between 0.68 and 0.95 under overcast sky conditions. Values for daylight were between 1.16–1.22. Calculated phytochrome photoequilibrium values in shadelight were approximately 0.35 under clear sky and 0.46 under overcast sky conditions. In each case there appeared to be no differences between the two canopies with respect to these minimum values.     

A miniaturized germanium-doped silicon dioxide-based surface plasmon resonance waveguide sensor for immunoassay detection

A surface plasmon resonance (SPR) waveguide immunosensor fabricated by germanium-doped silicon dioxide was investigated in this study. The designed waveguide sensor consisted of a 10 microm SiO(2) substrate layer (n=1.469), a 10 microm Ge-SiO(2) channel guide (n=1.492) and a 50 nm gold film layer for immobilization of biomolecules and SPR signal detection. The resultant spectral signal was measured by a portable spectrophotometer, where the sensor was aligned by a custom-designed micro-positioner. The results of the glycerol calibration standards showed that the resonance wavelength shifted from 628 to 758 nm due to changes of refractive index from 1.36 to 1.418. Flow-through immunoassay on waveguide sensors also showed the interactions of protein A, monoclonal antibody (mAb ALV-J) and avian leucosis virus (ALVs) resulted in wavelength shifting of 4.17, 3.03 and 2.18 nm, respectively. The SPR dynamic interaction could also be demonstrated successfully in 4 min as the sensor was integrated with a lateral flow nitrocellulose strip. These results suggest that SPR detection could be carried out on designed waveguide sensor, and the integration of nitrocellulose strip for sample filtering and fluid carrier would facilitate applications in point-of-care portable system.     

Determination of oxygen saturation and hematocrit of flowing human blood using two different spectrally resolving sensors.

The blood parameters oxygen saturation and hematocrit were determined by two different spectral sensors using reflectance spectra from 550 to 900 nm and partial transmission spectra centered at 660 nm. The spectra were analyzed by the method of partial least squares. One sensor consists of a miniature integrating sphere, while the other was fiber-guided. The results show that the geometry of the sensors and different blood flows do not influence the spectral analysis significantly. Independent of the sensor geometry, both hematocrit and oxygen saturation could be determined with an absolute predicted root mean square error of less than 3%. Furthermore, the analysis showed that hematocrit prediction requires eight wavelength regions and oxygen saturation prediction requires four wavelength regions using reflectance spectroscopy. This implies that if the measurement is restricted to reflectance, a spectrometer is indispensable for determining both blood parameters. Hematocrit determination could be improved using reflectance measurements in combination with transmission.     

Sensitivity of ex situ and in situ spectral surface plasmon resonance sensors in the analysis of protein arrays

We have investigated the sensitivity of ex situ (analysis under air condition) and in situ (analysis under liquid condition) spectral SPR sensors, which were self-constructed with fiber optic spectrometers. The sensitivity of SPR sensors was analyzed in the wavelength range of 550-780 nm by the interactions of streptavidin and biotinylated IgG, and the sensitivity was dependent on the wavelength of measurements. The sensitivity of an ex situ SPR sensor operated at the long wavelength range from 712 nm was approximately 2.6 times higher than that at the short wavelength range from 571 nm. In addition, the sensitivity of an ex situ spectral SPR sensor was about twice as high as that of an in situ spectral SPR sensor for the same resonance wavelength range. This was interpreted in that the difference in sensitivity between two SPR sensors was significantly caused by the evanescent field intensity at the metal/dielectric interface. Thus, it was suggested that ex situ spectral SPR sensors operated at the long wavelength range are sensitive biosensors for the high-throughput analysis of protein interactions on protein arrays.     

An apparatus for measuring photosynthetic quantum yields and quanta absorption spectra of intact plants

Abstract An apparatus is described which consists of an assimilation chamber mounted in the centre of a light-integrating Ulbricht sphere, irradiated through two fibreoptic light pipes. This arrangement provides totally diffuse radiation in the sphere. The quantum flux density in die sphere is measured by an integrating quantaspectrometer connected to the sphere by eight fibreoptic light pipes. The quantaspectrometer gives the spectral and the total quantum flux density in the sphere. By measuring the quantum flux density in the sphere before and after the insertion of a plant the number of absorbed quanta per unit time and plant area can be determined. In addition, the spectral distribution of the absorbed quantum flux density is obtained. CO₂-assimilation per unit time and plant area is determined in the same apparatus. The totally diffuse radiation within the sphere minimizes mutual shading between branches and leaves. Hence, well-defined light-responsecurves of photosynthesis can be obtained by plotting the flux density of C0₂-assimilation as a function of the absorbed quantum flux density, and the quantum yields of intact plants can be calculated. Examples of photosynthetic quantum yield determinations and quanta absorption spectra are given for some plant species.     

The energy budget of man: Variations with aspect in a downtown urban environment

The energy budget of man is computed and used to assess the microclimatic variation that can occur in a downtown urban environment through the effects of direction of exposure and open sky view factor. On sunny days the exposure to direct beam solar radiation was the most important factor in creating climatic differences. This directly contributed energy to man and warmed the radiant and air temperature environments. On a cloudy day very little variation in the radiation, temperature and humidity regimes occurred. Wind became the dominant factor with man experiencing a greater heat loss at windward locations. With the assumptions used in this study convective heat flux was responsible for the greatest heat losses in man.     

Granier树干液流测定系统在马占相思的水分利用研究中的应用

介绍了Granier热消散探针在树干液流测定中的工作原理,并利用该系统长期监测广东鹤山马占相思林14株样树的液流密度,分析了树木个体内和个体之间液流密度的差异、整树和林段水分利用的量化特征.由于树木边材结构以及周围微环境的差别,树木内和个体间的液流密度差异非常明显,变异系数的平均值分别为15.51%-37.26%、37.46%-50.73%.尽管液流密度的差异较大,但同一株树木不同方位的液流密度之间却呈现明显的线性相关（p＜0.0001）,这是重要的特征值,使得只需测定某一方位的液流密度经尺度外推计算整树和林段蒸腾成为可能.树木液流对环境因子响应的变化规律取决于所参照的时间尺度,日变化主要受光辐射、水汽压差等气候因子的控制,而土壤水份对液流的季节变化影响较大.形态特征明显影响树木的液流,高大树木由于边材较厚、树干粗壮和冠幅较宽而承载较多的辐射能量,因而水分蒸腾较高.对树木液流密度在径向和方位上进行适当的整合,可较准确地计算整树和林段蒸腾.由液流估测的马占相思整树和林段蒸腾的结果显示,该群落的水分利用在时间和空间上均有明显的分化.     

用便携式光谱仪同步测定和计算光强和光质的新方法

外界光强和光质对植物的影响在植物生理生态研究领域中一直受到高度关注。而测定光强的光量子计不能测定光质; 测定光质的光谱仪不能直接测定光强, 两者均不能同步测定光强和光质。该文作者建立了一个基于光谱仪测定条件的能量与光量子的经验转换公式, 用4只不同波长的窄带发光二极管(LED)光源结合光量子计(LI-190SB)对便携式光谱仪(AvaSpec-ULS2048×64)所获得的光谱进行了快速标定, 实现了用便携式光谱仪同步直接测定光量子通量密度和光质的目的。在自然光照条件下, 采用转换公式计算出光量子通量密度(PPFD)与实测的PPFD之间误差在-2%-5%范围内, 证实了这种方法的可靠性。通过这个新方法, 可以极大地拓宽便携式光谱仪的适用范围: 1)实验室内或野外只需用便携式光谱仪即可对光源及植物生长的光强和光质环境进行同步精确测定和计算; 2)可以计算光谱仪测定范围内任意波长区段的光量子通量密度; 3)无需采用标准光源即可获得绝对辐射(光)通量值。因此, 这项技术在植物生理生态研究领域具有广阔的应用前景。     

A new method to measure and calculate light intensity and light quality simultaneously by using portable spectrometer

The influence of light intensity and light quality on plants is highly concerned in the field of plant physiology and ecology. However, the calibrated quantum meter for measurement of light intensity cannot measure light quality, and vice versa. Here we developed an empirical formula to convert light energy to photon flux density, based on the measurement conditions of spectrometer. Under the guide of the formula, a portable spectrometer (AvaSpec-ULS2048×64) was calibrated by using four narrowband light emitting diode (LEDs) in combination with a calibrated quantum meter (LI-190SB). After calibration of the spectrometer, we can calculate photosynthetic photon flux density (PPFD or PAR) and measure spectrum of radiation flux simultaneously. Under natural light conditions, the errors between measured and calculated PPFDs are in the range from -2% to 5%, indicating the reliability of the method. With this new approach, the application of portable spectrometer can be greatly broadened: 1) the light intensity and quality of light source and plant growth light environment can be obtained simultaneously, 2) PPFD can be obtained within any specified wavelength range, and 3) there is no need to use standard light source to obtain the absolute light/radiation flux of a spectrum measured by spectrometer. In conclusion, this method has potential applications for the study of plant physiology and ecology.     

Intensity and spectral emission as factors affecting the efficacy of an insect electrocutor trap towards the house-fly

Competitive tests were used to determine how the quantitative and spectral characteristics of an electrocutor trap light source affected the attraction of the house-fly, Musca domestica L. It was found that an increase in the radiant flux (F_e) of the trap lamps due to an increase in radiant area (A), caused a much larger increase in catch than if radiant flux was increased through higher radiant emittance (M_c). The results from electroretinograms recorded in response to different levels of M_e were consistent with the idea that at a given wavelength the attractiveness of a lamp is attributable to the quantitative output perceived by the fly. Of nine fluorescent lamps, the most attractive had peak emission at 340 nm. A blue lamp (peak emission 419 nm) attracted less than a third as many flies as the UV emitting lamps, and a white lamp (peak emission 585 nm) attracted fewer than a quarter as many. The corresponding photoreceptor responses were measured using the electroretinogram. At wavelengths above 400 nm the attractiveness of a lamp to a fly appears to be lower relatively than the photoreceptor response. Within the ultraviolet region (300 nm–400 nm) attractiveness is again attributable to the quantitative output perceived by the fly. It is concluded that there is a genuine behavioural preference for lamp emissions in the ultraviolet region.     

The ratio of transmitted near-infrared radiation to photosynthetically active radiation (PAR) increases in proportion to the adsorbed PAR in the canopy

The daily total photosynthetically active radiation (400??00?nm, PAR) and near-infrared radiation (700??000?nm, NIR) were measured in the understory beneath the canopy (PARt and NIRt) and above the canopy (PARi and NIRi) of a Japanese cool-temperate deciduous broad-leaved forest during the snow-free period (May to November). The integration of spectral radiation for NIR and that for PAR, and the daily integrations of instantaneous NIR and PAR, reduced the noises from the optical difference in spectrum and from canopy structure heterogeneity, sky condition and solar elevation. PARi/PARt was linearly related to NIRt/PARt (R2?=?0.96). The effect of cloudiness was negligible, because the fluctuation of NIRi/PARi was quite small regardless of season and weather conditions compared with the range of NIRt/PARt in the forest. The ratio of NIRt/PARt beneath the canopy was log-linearly related to the in situ leaf area index (LAI) with a wide range from 0 to 5.25 (R2?=?0.97). We conclude that seasonal changes in fAPAR (=?1???PARt/PARi) and LAI of a canopy can be estimated with high accuracy by transmitted NIRt and PARt beneath the canopy.     

Design and fabrication development of a micro flow heated channel with measurements of the inside micro-scale flow and heat transfer process

The current work provides a design and fabrication technique for a micro channel system that can provide a uniform heat flux boundary condition on the channel wall and a well insulation on the wall to prevent heat loss from the channel to the outside ambient. Therefore, detailed micro-scale flow and heat transfer process and information along the channel can be studied. Semiconductor sensor material was selected to fabricate both the heaters and the arrays of temperature sensors on a silicon substrate. These heaters and sensors were then moved to a low thermal conductivity epoxy-glass substrate for fabrication of the channel. Design consideration and fabrication techniques involved in this processes will be discussed. A final measurement for the validation of the heaters and the sensors fabricated and a study of the flow friction behavior and the heat transfer coefficient distributions inside the micro channel will be presented. The local Nusselt number distrubution inside the micro channel is reported the first time in the open literature.     

Modelling radiation fluxes in simple and complex environments: basics of the RayMan model

Short- and long-wave radiation flux densities absorbed by people have a significant influence on their energy balance. The heat effect of the absorbed radiation flux densities is parameterised by the mean radiant temperature. This paper presents the physical basis of the RayMan model, which simulates the short- and long-wave radiation flux densities from the three-dimensional surroundings in simple and complex environments. RayMan has the character of a freely available radiation and human-bioclimate model. The aim of the RayMan model is to calculate radiation flux densities, sunshine duration, shadow spaces and thermo-physiologically relevant assessment indices using only a limited number of meteorological and other input data. A comparison between measured and simulated values for global radiation and mean radiant temperature shows that the simulated data closely resemble measured data.     

Some approaches for measuring and modelling riparian shade

The radiation environment of streams is of major ecological importance because it controls stream thermal regime and light availability for photosynthesis. Therefore, methods are needed for measuring stream shade in practical riparian management. The quantity ‘diffuse non-interceptance’ (difn), defined as the proportion of incident lighting received under a sky of uniform brightness and best estimated from fish-eye images, is useful for general specification of light exposure. For routine measurement of difn along stream reaches we recommend using a matched pair of simple light sensors (e.g. photosynthetically available radiation sensors) under conditions of complete overcast (which has almost uniform brightness). Methods are also needed for predicting future light exposure as riparian plantings grow and increasingly shade the stream. A simple model is outlined for predicting difn at the channel centre as a function of channel dimensions (stream width, w) and riparian plant character (foliage density, canopy height, h). The model reproduces the broad empirical trend of increasing shade with increasing h/w ratio. Future model refinement will aim to quantify the increase in shade moving from channel centre to edge under an overhanging canopy.     

Is there a representative wavelength for photosynthetically active radiation in the terrestrial environment?

Abstract The spectral quality of photosynthetically active radiation (PAR; 400–700 nm) incident at an open site and on a forest floor was analysed to determine whether narrowband (1 nm) wavelengths could be used to estimate total incident PAR. The narrowband estimates were not as good as the broadband estimates based on silicon photovoltaic sensors, but the variance at 530 nm was sufficiently small for narrowband sensors to be considered as low‐cost and light‐weight alternatives to broadband sensors.     

Evaluating the usefulness of hemispherical photographs as a means to estimate photosynthetic photon flux density during a growing season in the understorey of Nothofagus pumilio forests

Abstract

Old-growth Nothofagus pumilio forests in Chile are managed employing a shelterwood system. A wide range of canopy openings can be found in old-growth and managed forests. Plant survival and growth in the understorey are influenced by the light available. There are limitations (practical and economic) to monitoring the light in the understorey. The aim of this study was to assess the options to estimate the forest understorey photosynthetic photon flux density (PPFD) measured during the growing season (GS) using canopy openness (CO) estimated by means of hemispherical photographs (HP). PPFD was measured using 31 sensors (Li-190SA quantum sensor) over the course of three GSs (October to March). The sensors were installed in an old-growth stand and another subjected to a regeneration felling under a shelterwood system. One HP was taken above each sensor (during the final GS) and the CO estimated. A comparison of the three seasons revealed that the sum of the PPFD during the GSs did not differ significantly. The CO could be used to effectively predict the sum of the PPFD during a GS (R ² = 0.959). These results demonstrate the usefulness of HPs as a means to estimate the sum of the PPFD during a GS.     

Insects could exploit UV-green contrast for Landmark navigation

Illumination-invariant detection of landmark features is a prerequisite for landmark navigation in insects. It is suggested that a contrast mechanism involving the UV and green receptors of insect eyes could guarantee a robust separation between natural objects as foreground and sky as background. Using a sensor with a UV and a green channel that in their spectral characteristics are close to the corresponding insect photoreceptors, data of natural objects and sky were collected. The data show that the two classes can be separated by a fixed threshold in the UV-green color space, offering an advantage over a purely UV-based separation that would require a dynamic threshold. Based on a numerical method, UV-green antagonism is shown to guarantee a more reliable discrimination than UV-blue antagonism.     

Photosynthetic action spectra and adaptation to spectral light distribution in a benthic cyanobacterial mat.

We studied adaptation to spectral light distribution in undisturbed benthic communities of cyanobacterial mats growing in hypersaline ponds at Guerrero Negro, Baja California, Mexico. Microscale measurements of oxygen photosynthesis and action spectra were performed with microelectrodes; spectral radiance was measured with fiber-optic microprobes. The spatial resolution of all measurements was 0.1 mm, and the spectral resolution was 10 to 15 nm. Light attenuation spectra showed absorption predominantly by chlorophyll a (Chl a) (430 and 670 nm), phycocyanin (620 nm), and carotenoids (440 to 500 nm). Blue light (450 nm) was attenuated 10-fold more strongly than red light (600 nm). The action spectra of the surface film of diatoms accordingly showed activity over the whole spectrum, with maxima for Chl a and carotenoids. The underlying dense Microcoleus population showed almost exclusively activity dependent upon light harvesting by phycobilins at 550 to 660 nm. Maximum activity was at 580 and 650 nm, indicating absorption by phycoerythrin and phycocyanin as well as by allophycocyanin. Very little Chl a-dependent activity could be detected in the cyanobacterial action spectrum, even with additional 600-nm light to excite photosystem II. The depth distribution of photosynthesis showed detectable activity down to a depth of 0.8 to 2.5 mm, where the downwelling radiant flux at 600 nm was reduced to 0.2 to 0.6% of the surface flux.     

Computed tomography-based spectral imaging for fluorescence microscopy

The computed tomography imaging spectrometer (CTIS) is a non-scanning instrument capable of simultaneously acquiring full spectral information (450-750 nm) from every position element within its field of view (75 microm x 75 microm). The current spatial and spectral sampling intervals of the spectrometer are 1.0 microm and 10 nm, respectively. This level of resolution is adequate to resolve signal responses from multiple fluorescence probes located within individual cells or different locations within the same cell. Spectral imaging results are presented from the CTIS combined with a commercial inverted fluorescence microscope. Results demonstrate the capability of the CTIS to monitor the spatiotemporal evolution of pH in rat insulinoma cells loaded with SNARF-1. The ability to analyze full spectral information for two-dimensional (x, y) images allows precise evaluation of heterogeneous physiological responses within cell populations. Due to low signal levels, integration times up to 2 s were required. However, reasonable modifications to the instrument design will provide higher system transmission efficiency with increased temporal and spatial resolution. Specifically, a custom optical design including the use of a larger format detector array is under development for a second-generation system.