Effects of thinning on the understory light environment of different stands and the photosynthetic performance and growth of the reforestation species Phoebe bournei

Light levels determine regeneration in stands and a key concern is how to regulate the light environment of different stand types to the requirements of the understory.In this study,we selected three stands typical in south China(a Cryptomeria japonica plantation,a Quercus acutissima plantation,and a mixed stand of both)and three thinning intensities to determine the best understory light environ-ment for 3-year-old Phoebe bournei seedlings.The canopy structure,understory light environment,and photosynthe-sis and growth indicators were assessed following thin-ning.Thinning improved canopy structure and understory light availability of each stand;species composition was the reason for differences in the understory light environ-ment.Under the same thinning intensity,the mixed stand had the greatest light radiation and most balanced spectral composition.P.bournei photosynthesis and growth were closely related to the light environment;all three stands required heavy thinning to create an effective and sustained understory light environment.In a suitable understory light environment,the efficiency of light interception,absorption,and use by seedlings was enhanced,resulting in a higher carbon assimilation the main limiting factor was stomatal conductance.As a shade-avoidance signal,red/far-red radia-tion is a critical factor driving changes in photosynthesis and growth of P.bournei seedlings,and a reduction increased light absorption and use capacity and height:diameter ratios.The growth advantage transformed from diameter to height,enabling seedlings to access more light.Our findings suggest that the regeneration of shade-tolerant species such as P.bournei could be enhanced if a targeted approach to thinning based on stand type was adopted.

Heterogeneous population distribution enhances resistance to wheat lodging by optimizing the light environment

Lodging is still the key factor that limits continuous increases in wheat yields today,because the mechanical strength of culms is reduced due to low-light stress in populations under high-yield cultivation.The mechanical properties of the culm are mainly determined by lignin,which is affected by the light environment.However,little is known about whether the light environment can be sufficiently improved by changing the population distribution to inhibit culm lodging.Therefore,in this study,we used the wheat cultivar“Xinong 979”to establish a low-density homogeneous distribution treatment(LD),high-density homogeneous distribution treatment(HD),and high-density heterogeneous distribution treatment(HD-h)to study the regulatory effects and mechanism responsible for differences in the lodging resistance of wheat culms under different population distributions.Compared with LD,HD significantly reduced the light transmittance in the middle and basal layers of the canopy,the net photosynthetic rate in the middle and lower leaves of plants,the accumulation of lignin in the culm,and the breaking resistance of the culm,and thus the lodging index values increased significantly,with lodging rates of 67.5%in 2020–2021 and 59.3%in 2021–2022.Under HD-h,the light transmittance and other indicators in the middle and basal canopy layers were significantly higher than those under HD,and the lodging index decreased to the point that no lodging occurred.Compared with LD,the activities of phenylalanine ammonia-Lyase(PAL),4-coumarate:coenzyme A ligase(4CL),catechol-O-methyltransferase(COMT),and cinnamyl-alcohol dehydrogenase(CAD)in the lignin synthesis pathway were significantly reduced in the culms under HD during the critical period for culm formation,and the relative expression levels of TaPAL,Ta4CL,TaCOMT,and TaCAD were significantly downregulated.However,the activities of lignin synthesis-related enzymes and their gene expression levels were significantly increased under HD-h compared with HD.A partial least squares path modeling analysis found significant positive effects between the canopy light environment,the photosynthetic capacity of the middle and lower leaves of plants,lignin synthesis and accumulation,and lodging resistance in the culms.Thus,under conventional high-density planting,the risk of wheat lodging was significantly higher.Accordingly,the canopy light environment can be optimized by changing the heterogeneity of the population distribution to improve the photosynthetic capacity of the middle and lower leaves of plants,promote lignin accumulation in the culm,and enhance lodging resistance in wheat.These findings provide a basis for understanding the mechanism responsible for the lower mechanical strength of the culm under high-yield wheat cultivation,and a theoretical basis and for developing technical measures to enhance lodging resistance.

Changes in human settlement environments and their drivers in valley cities located in arid and semi-arid regions:A case study of Lanzhou in Western China

Development of urban human settlement environments(HSEs)is an integral part of promoting high-quality and sustainable regional development and constructing a beautiful China.The city of Lanzhou,located at the geometric center of China,is the only provincial capital traversed by the Yellow River.Given the constraints posed by the valley topography and the need for economic development,the development of this HSE,which is located within an arid region,poses considerable challenges.Evidently,an understanding of the evolution of HSEs and drivers of changes in them contributes to high-quality,sustainable urban development in arid and semi-arid regions.An analytical model was developed using the parameters of relief degree of land surface,human comfort days,the land cover index,nighttime light index,and precipitation.This model was used in combination with population density and the gross domestic product to analyze the spatial distribution of Lanzhou's HSE and its drivers.The results showed that landscapes in Lanzhou underwent significant changes between 2000 and 2022,with an increase in building-up land(+0.946%),cultivated land(+0.134%),and forest land(+0.018%)and a decrease in grassland(-1.10%).There was significant outward expansion of the main urban zone of Lanzhou and of various county towns,with the increase in building-up land being most prominent.During this period,there were significant changes in the periphery of the core urban area and county towns in Lanzhou,with decreases moving from the urban center(the highest value)to the surrounding areas(Yongdeng County had the lowest value).The correlation between the HSE and population density grew stronger in Anning and Chengguan Districts but became weaker in Xigu and Qilihe Districts.Spatiotemporal variations in the HSE were primarily caused by climate change,followed by human activities,and were also influenced by the valley topography.Overall,the spatial distribution of population density and the HSE in Lanzhou demonstrated good consistency under the in-fluence of economic development and urbanization.

Research on color image matching method based on feature point compensation in dark light environment

Image matching refers to the process of matching two or more images obtained at different time,different sensors or different conditions through a large number of feature points in the image.At present,image matching is widely used in target recognition and tracking,indoor positioning and navigation.Local features missing,however,often occurs in color images taken in dark light,making the extracted feature points greatly reduced in number,so as to affect image matching and even fail the target recognition.An unsharp masking(USM)based denoising model is established and a local adaptive enhancement algorithm is proposed to achieve feature point compensation by strengthening local features of the dark image in order to increase amount of image information effectively.Fast library for approximate nearest neighbors(FLANN)and random sample consensus(RANSAC)are image matching algorithms.Experimental results show that the number of effective feature points obtained by the proposed algorithm from images in dark light environment is increased,and the accuracy of image matching can be improved obviously.

Tempo-Spatial Variations in Stomatal Conductance, Aperture and Density of Ligustrum sinense Acclimated to Different Light Environments

There was heterogeneous distribution in stomatal conductance (g-s) and stomatal aperture for both high- and low-light leaves of Ligustrum sinense Lour. in four designated positions within a leaf. Linear or exponential or polynomial relationships between g-s and stomatal aperture were found when regression of g-s and stomatal aperture was established. Statistical analysis revealed that the relationship between g-s and stomatal aperture for high-light leaves was more significant than that of low-light leaves. A linear relationship between g-s and stomatal aperture existed in both positions 1 and 3 for both high- and low-light leaves. The stomatal density of the low-light leaves was much lower than that of the high-light leaves. The sensitivity of stomata to changing environment for high-light leaves was higher than that for low-light leaves, which may also relate to the higher stomatal density for the high-light leaves.

Photosynthetic Gas Exchange and Leaflet Movement of Robinia pseudoacacia in Relation to Changing Light Environments

On the sunny days, there were little diurnal changes in both azimuth and directional angle for either sun_ or shade_leaflet. However, there existed a significant diurnal change in midrib angle that reflected movements regarding evasion of light stress around noon hours. On the cloudy day, a very little diurnal difference was found in azimuth, directional and midrib angle. It is suggested that changing light environment is the main factor for inducing leaflet movement of Robinia pseudoacacia , and the rhythmical movement does not attribute to the leaflet movement. Leaf orientation control test showed that the photosynthetic rate ( Pn ), stomatal conductance ( g s ) and transpiration ( Tr ) of the artificial fixed_leaflets were significantly lower than that of control_leaflets. And the leaf temperature ( Tl ) of the fixed leaflets significantly exceeded that of control_leaflets, which may attribute to the significant difference of light interception between the fixed and control_leaflets. The light_dependent leaflet movement is the morphological adjustment of maintaining optimal physiological status.

Control of light environment: A key technique for high-yield and high-quality vegetable production in protected farmland

Vegetable crops such as cucumber and tomato are grown widely through the world using not only field but also protected farmland. Sensitive responses of many vegetables have been widely reported to environmental conditions such as light, air temperature, relative humility, and CO2 concentration in the past years. Among these environmental factors, light is considered to be the most important one for vegetable growth and development, especially in protected farmland. Therefore, lots of researches on effects of light environment, including light intensity, light quality, photoperiod, and light direction, on vegetable growth and development have been done in order to optimize the environmental conditions for high-yield and high-quality vegetable production in protected farmland. In this review, recent advances in light environment control for vegetable production in protected farmland have been reviewed and the prospective for the future research has been proposed as well.

Systemic regulation of photosynthetic function in maize plants at graining stage under a vertically heterogeneous light environment

To cope with a highly heterogeneous light environment,photosynthesis in plants can be regulated systemically.Currently,the majority of studies are carried out with various plants during the vegetative growth period.As the reproductive sink improves photosynthesis,we wondered how photosynthesis is systemically regulated at the reproductive stage under a vertically heterogeneous light environment in the field.Therefore,changes of light intensity within canopy,chlorophyll content,gas exchange,and chlorophyll a fluorescence transient were carefully investigated at the graining stage of maize under various planting densities.In this study,a high planting density of maize drastically reduced the light intensities in the lower canopy,and increased the difference in vertical light distribution within the canopy.With the increase of vertical heterogeneity,chlorophyll content,light-saturated photosynthetic rate and the quantum yield of electron transport in the ear leaf(EL) and the fourth leaf below the ear(FLBE) were decreased gradually,and the ranges of declines in these parameters were larger at FLBE than those at EL.Leaves in the lower canopy were shaded artificially to further test these results.Partial shading(PS) resulted in a vertically heterogeneous light environment and enhanced the differences in photosynthetic characteristics between EL and FLBE.Removing the tassel and top leaves(RTL) not only improved the vertical light distribution within the canopy,but also reduced the differences in photosynthetic characteristics between the two leaves.Taken together,these results demonstrated that maize plants could enhance the vertical heterogeneity of their photosynthetic function to adapt to their light environment;slight changes of the photosynthetic function in EL at the graining stage under a vertically heterogeneous light environment indicated that the systemic regulation of photosynthesis is weak at the graining stage.

Responses of fractal dimensions of Picea koraiensis seedlings to different light environments

The changes of fractal dimension ofPicea koraiensis seedlings under different light intensities in natural secondary forests was studied. The results showed that with the change of light environment, crown characters ofPicea koraiensis seedlings exhibited a greater plastic in lateral number, lateral increment, lateral dry weight, and specific leaf area. The range of calculated fractal dimensions of seedling crowns was confined between 2.5728 and 2.1036, but maximum of fractal dimension achieved in term moderate shading and in extreme low light conditions fractal dimension was least.

Measuring Light and Geometry Data of Roadway Environments with a Camera

Evaluation of the conspicuity of roadway environments for their environmental impact on driving performance is vital for roadway safety. Existing meters and tools for roadway measurements cannot record light and geometry data simultaneously in a high resolution. This study introduced a new method that adopted recently developed high dynamic range (HDR) photogrammetry to measure the luminance and XYZ coordinates of millions of points across a road scene with the same device—a camera, and a MatLab code for data treatment and visualization. To validate this method, the roadway environments of a straight and flat section of Jayhawk Boulevard (482.8 m long) at Lawrence, KS and a roundabout (15.3 m in diameter) at its end were measured under clear and cloudy sky in the daytime and at nighttime with dry and wet pavements. Eight HDR images of the roadway environments under different viewing conditions were generated using the HDR photogrammetric techniques and calibrated. From each HDR image, synchronous light and geometry data were extracted in Radiance and further analyzed to identify potential roadway environmental hazards using the MatLab code (http://people.ku.edu/~h717c996/research.html). The HDR photogrammetric measurement with current equipment had a margin of errors for geometry measurement that varied with the measuring distance, averagely 23.1% - 27.5% for the Jayhawk Boulevard and 9.3% - 16.2% for the roundabout. The accuracy of luminance measurement was proven in the literature as averagely 1.5% - 10.1%. The camera-aided measurement is fast, non-contact, non-destructive, and off the road, thus, it is deemed more efficient and safer than conventional ways using meters and tools. The HDR photogrammetric techniques with current equipment still need improvements on accuracy and speed of the data treatment.

Prediction of Photosynthetic Carbon Assimilation Rate of Individual Rice Leaves under Changes in Light Environment Using BLSTM-Augmented LSTM

A model to predict photosynthetic carbon assimilation rate(A)with high accuracy is important for forecasting crop yield and productivity.Long short-term memory(LSTM),a neural network suitable for time-series data,enables prediction with high accuracy but requires mesophyll variables.In addition,for practical use,it is desirable to have a technique that can predict A from easily available information.In this study,we propose a BLSTM augmented LSTM(BALSTM)model,which utilizes bi-directional LSTM(BLSTM)to indirectly reproduce the mesophyll variables required for LSTM.The most significant feature of the proposed model is that its hybrid architecture uses only three relatively easy-to-collect external environmental variables—photosynthetic photon flux density(Q_(in)),ambient CO_(2) concentration(C_(a)),and temperature(T_(air))—to generate mesophyll CO_(2) concentration(C_(i))and stomatal conductance to water vapor(g_(sw))as intermediate outputs.Then,A is predicted by applying the obtained intermediate outputs to the learning model.Accordingly,in this study,1)BALSTM(Q_(in),C_(a),T_(air))had a significantly higher A prediction accuracy than LSTM(Q_(in),C_(a),T_(air))in case of using only Q_(in),C_(a),and T_(air);2)BALSTMC_(i),g_(sw),which had C_(i) and g_(sw) as intermediate products,had the highest A prediction accuracy compared with other candidates;and 3)for samples where LSTM(Q_(in),C_(a),T_(air))had poor prediction accuracy,BALSTMC_(i),g_(sw)(Q_(in),C_(a),T_(air))clearly improved the results.However,it was found that incorrect predictions may be formed when certain factors are not reflected in the data(e.g.,timing,cultivar,and growth stage)or when the training data distribution that accounts for these factors differs from the predicted data distribution.Therefore,a robust model should be constructed in the future to improve the prediction accuracy of A by conducting gasexchange measurements(including a wide range of external environmental values)and by increasing the number of training data samples.

Approach to the Zoning and Management for the Function of Light Environment

Light pollution becomes more and more serious, but the study on this field is far from enough. In this paper, light environment is defined as light-free area, dark area, intermediate sight area, and bright area. In addition, it is marked with index value by index system, which includes average brightness, brightness evenness, glare index, and background brightness.

Effects of Plant Density on Yield and Canopy Micro Environment in Hybrid Cotton

A rational plant population is an important attribute to high yield of cotton, because it can provide a beneficial micro environment within the canopy for plant growth and development as well as yield formation. A 2-yr field experiment was conducted to determine the optimal plant density based on cotton yield in relation to the canopy micro environment （canopy temperature, relative humidity and light transmittance）. Six plant densities （1.2-5.7 plants m^-2） were arranged with a completely randomized block design. The highest cotton yield （1 507 kg ha^-1） was obtained at 3.0 plants m^-2 due to more bolls per unit ground area （79 bolls m2）, while the lowest yield （1 091 kg ha1） was obtained at 1.2 plants m^-2. Under the moderate plant density （3.0 plants m^-2）, there was a lower mean daily temperature （MDT, 27. 1℃） attributing to medium daily minimum temperature （Train, 21.9℃） and the lowest daily maximum temperature （Tmax, 35.8℃）, a moderate mean canopy light transmittance of 0.51, and lower mean daily relative humidity （MRH） of 79.7% from June to October. The results suggest that 3.0 plants m^-2 would be the optimal plant density because it provides a better canopy micro environment.

Radiation Use Efficiency of Cotton in Contrasting Environments

Crop growth and yield varies among locations due to differences in environmental parameters, such as temperature, relative humidity, solar radiation and vapor pressure deficit. Previous research has shown that increasing vapor pressure deficit has a negative effect on radiation use efficiency of many crops. In this study, the radiation use efficiency of cot-ton (Gossypium hirsutum L.) grown in two contrasting production environments, Arkansas and California, was evaluated for two years, in 2006 and 2007. Temperature, relative humidity, vapor pressure deficit and photosyntheti-cally active radiation were recorded at both locations. Although the crop in California accumulated more dry matter during the period of the study, the radiation use efficiency was found to be lower compared to Arkansas. Radiation use efficiency for the Arkansas and California locations was estimated at 2.060 and 1.518 g?MJ–1 of intercepted photosynthetically active radiation, respectively. The higher productivity observed in California can be attributed to larger amounts of incident and intercepted radiation in this location. Radiation use efficiency of cotton was estimated to decrease with increasing vapor pressure deficit by a slope of –0.47 g?MJ–1?kPa–1.

Visible Light Communication for Vehicular Applications: A Novel Architecture with Proof-of-Concept Prototype

When there is an increasing interest in visible light communication(VLC), outdoor vehicle VLC has emerged as a promising candidate technology for future intelligent transportation systems. However, in VLC based vehicular applications, several challenges impede successful commercial application of VLC based products. This article first provides a thorough overview of the existing challenges. To overcome these challenges, we propose a novel architecture with tracking and environment sensing ability for practical vehicular applications. Moreover, a proof-ofconcept prototype is implemented to validate the feasibility of the proposed system. Experimental and simulation results show that the proposed VLC system can provide reliable communications with a bit-error rate less than 10-4for vehicles under strong interference lights. Finally, based on the evaluations, we propose some key design issues for future studies in this research area.

The Optimal Design of Lighting Systems for Designated Office Building in Thailand

This paper proposes the financial index of payback period analysis in order to evaluate the economic performance of lighting system. Conventional designs and proposed optimal design using the Energy Conversation Promotion Act （No. 2） B.E. 2550 of Ministry of Energy （Section--The Type or Size of Building Standards and Rules and Procedures, Building Design for Energy Conservation, Act B.E. 2552） are compared based on illumination standard for office building in term of energy consumption, return of investment and environmental impact. Firstly, the Type or Size of Building Standards and Rule and Procedures, Building Design for Energy Conservation, Act B.E. 2552 is reviewed and compared with the conventional designs of lighting system for office building. Next, the lifetime energy consumption of fluorescent lamp T5 with electronic ballast, fluorescent lamp T8 with standard ballast and fluorescent lamp T8 with electronic ballast are simulated using DIALux software program in three sizes office buildings. Then, the payback period and CO2 emission of lighting system for selected office building are simulated by various scenarios, which the analytical results show are the optimal lighting system for office building under the present situation. Finally, the optimal design of lighting system for designated office building in Thailand will be discussed with respect to the energy performance with environmental friendly.

Comparison of Illuminance in Different Environments: A Case Study on Subway Stations

With urbanization and the rapid development of social economy,China’s rail transit industry has developed rapidly in recent years.In order to alleviate the pressure of road network,subways provide convenience as they are fast and space-saving.Subway stations are major energy consumers of urban power grid due to their large traffic volume and long operation time.On the premise of ensuring operation safety,reducing the energy consumption of subway helps in energy conservation and emission reduction as proposed in the 13th Five-Year Plan.According to the statistics of the energy-saving evaluation report of rail transit engineering,the lighting system accounts for 20%-30%of the total power consumption of the subway station.Due to the single lighting control mode of the lighting system in the subway station,the actual station illumination cannot be reported and adjusted in time,resulting in the waste of lighting energy and high power consumption of the system.Through in-depth research on the intelligent lighting system of subway station,this paper improves the system control,and finally summarizes the optimization scheme of subway station lighting design which can effectively save the power consumption of lighting system.The main contents of this paper are as follows:The research results of this paper can provide effective measures for energy saving of electric lighting in subway stations and reduce electric energy consumption;on the other hand,as an integral part of building lighting energy-saving system,it also has certain guiding significance for the research of building lighting energy-saving.

新伊高速毗邻隧道遮阳棚光环境及降碳分析

为减少由光照强度差异引发的交通事故,以新伊高速公路工程为依托,在宋家凹—水沟河毗邻隧道连接段设置钢筋混凝土与钢结构组合形式的遮阳棚,计算限行速度下遮阳棚的长度,运用DIALux仿真软件对不同时间点下的2种工况进行研究,并采用碳排放因子法分析不同工况下的碳排放量。结果表明:该毗邻隧道连接段遮阳棚长度为100 m。设置遮阳棚后,路面照度降低率达到57.97%,照度总均匀度大于0.4,现场实测值与模拟值误差在10%范围内,均满足相关标准的要求。此外,设置遮阳棚后,每年减少碳排放量82.56 t CO_(2)e,运营2.8 a后可弥补建造时产生的碳排放,建设成本将在3.7 a后收回。在使用寿命期内,可减少碳排放量3 795.74 t CO_(2)e,节约成本577.31万元,实现了减排和节约成本的双重效果。

艺术照明在适老光环境设计中的应用研究

随着我国进入老龄化社会,提升适老居住与生活环境品质成为一项重要社会课题。本文针对二十一世纪以来照明技术和前沿视觉科学的进展,探讨了光环境对老年人生物节律的影响,特别是心理、生理健康方面的变化。同时,本文还探讨了艺术照明与传统照明设计的差异,强调利用光艺术改善空间的视觉表现和光环境氛围的同时,还可对老年人的感知和情绪调节等方面产生积极影响。本文聚焦艺术照明在实现适老光环境中的作用,探讨其设计方法、媒介形式及指标参数等对老年人心理、生理健康的影响,提出具有实践及社会意义的设计方法和建议。