Rice canopy temperature is affected by nitrogen fertilizer

Canopy temperature strongly influences crop yield formation and is closely related to plant physiological traits.However, the effects of nitrogen treatment on canopy temperature and rice growth have yet to be comprehensively examined. We conducted a two-year field experiment with three rice varieties(HD-5, NJ-9108, and YJ-805) and three nitrogen treatments(zero-N control(CK), 200 kg ha~(–1)(MN), and 300 kg ha~(–1)(HN)). We measured canopy temperature using a drone equipped with a high-precision camera at the six stages of the growth period. Generally,canopy temperature was significantly higher for CK than for MN and HN during the tillering, jointing, booting, and heading stages. The temperature was not significantly different among the nitrogen treatments between the milky and waxy stages. The canopy temperature of different rice varieties was found to follow the order: HD-5>NJ-9108>YJ-805, but the difference was not significant. The canopy temperature of rice was mainly related to plant traits, such as shoot fresh weight(correlation coefficient r=–0.895), plant water content(–0.912), net photosynthesis(–0.84), stomatal conductance(–0.91), transpiration rate(–0.90), and leaf stomatal area(–0.83). A structural equation model(SEM) showed that nitrogen fertilizer was an important factor affecting the rice canopy temperature.Our study revealed:(1) A suite of plant traits was associated with the nitrogen effects on canopy temperature,(2) the heading stage was the best time to observe rice canopy temperature, and(3) at that stage, canopy temperature was negatively correlated with rice yield, panicle number, and grain number per panicle. This study suggests that canopy temperature can be a convenient and accurate indicator of rice growth and yield prediction.

The influences of canopy temperature measuring on the derived crop water stress index

Crop water stress index(CWSI)is widely used for efficient irrigation management.Precise canopy temperature(T_(c))measurement is necessary to derive a reliable CWSI.The objective of this research was to investigate the influences of atmospheric conditions,settled height,view angle of infrared thermography,and investigating time of temperature measuring on the performance of the CWSI.Three irrigation treatments were used to create different soil water conditions during the 2020-2021 and 2021-2022 winter wheat-growing seasons.The CWSI was calculated using the CWSI-E(an empirical approach)and CWSI-T(a theoretical approach)based on the T_(c).Weather conditions were recorded continuously throughout the experimental period.The results showed that atmospheric conditions influenced the estimation of the CWSI;when the vapor pressure deficit(VPD)was>2000 Pa,the estimated CWSI was related to soil water conditions.The height of the installed infrared thermograph influenced the T_(c)values,and the differences among the T_(c)values measured at height of 3,5,and 10 m was smaller in the afternoon than in the morning.However,the lens of the thermometer facing south recorded a higher T_(c)than those facing east or north,especially at a low height,indicating that the direction of the thermometer had a significant influence on T_(c).There was a large variation in CWSI derived at different times of the day,and the midday measurements(12:00-15:00)were the most reliable for estimating CWSI.Negative linear relationships were found between the transpiration rate and CWSI-E(R^(2)of 0.3646-0.5725)and CWSI-T(R^(2)of 0.5407-0.7213).The relations between fraction of available soil water(FASW)with CWSI-T was higher than that with CWSI-E,indicating CWSI-T was more accurate for predicting crop water status.In addition,The R^(2)between CWSI-T and FASW at 14:00 was higher than that at other times,indicating that 14:00 was the optimal time for using the CWSI for crop water status monitoring.Relative higher yield of winter wheat was obtained with average seasonal values of CWSI-E and CWSI-T around 0.23 and 0.25-0.26,respectively.The CWSI-E values were more easily influenced by meteorological factors and the timing of the measurements,and using the theoretical approach to derive the CWSI was recommended for precise irrigation water management.

Effects of Elevated CO 2 and High Temperature on Single Leaf and Canopy Photosynthesis of Rice

The increase of atmospheric CO 2 concentration is indisputable. In such condition, photosynthetic response of leaf is relatively well studied, while the comparison of that between single leaf and whole canopy is less emphasized. The stimulation of elevated CO 2 on canopy photosynthesis may be different from that on single leaf level. In this study, leaf and canopy photosynthesis of rice (Oryza sativa L.) were studied throughout the growing season. High CO 2 and temperature had a synergetic stimulation on single leaf photosynthetic rate until grain filling. Photosynthesis of leaf was stimulated by high CO 2, although the stimulation was decreased by higher temperature at grain filling stage. On the other hand, the simulation of elevated CO 2 on canopy photosynthesis leveled off with time. Stimulation at canopy level disappeared by grain filling stage in both temperature treatments. Green leaf area index was not significantly affected by CO 2 at maturity, but greater in plants grown at higher temperature. Leaf nitrogen content decreased with the increase of CO 2 concentration although it was not statistically significant at maturity. Canopy respiration rate increased at flowering stage indicating higher carbon loss. Shading effect caused by leaf development reached maximum at flowering stage. The CO 2 stimulation on photosynthesis was greater in single leaf than in canopy. Since enhanced CO 2 significantly increased biomass of rice stems and panicles, increase in canopy respiration caused diminishment of CO 2 stimulation in canopy net photosynthesis. Leaf nitrogen in the canopy level decreased with CO 2 concentration and may eventually hasten CO 2 stimulation on canopy photosynthesis. Early senescence of canopy leaves in high CO 2 is also a possible cause.

A Preliminary Analysis of the Relationship between Longan Canopy Temperature and Air Temperature during Overwintering Period

[Objective] The study aimed to provide supports for developing chilling and freezing injury monitoring and disaster damage assessment of longan(Dimocarpus Longan Lour.).[Method] Based on field observation data,the relationships between longan canopy temperature and air temperature under different weather types(sunny,cloudy to sunny,cloudy,rainy,radiation chilling injury and advection chilling injury)in 2007-2008 winter were analyzed.[Result] Diurnal variations of longan canopy temperature under sunny and radiation chilling injury weather conditions were most dramatic,followed with those under cloudy to sunny condition,while variations under cloudy,rainy and advection chilling injury conditions were mild.Diurnal variations of orchard air temperature were also closely related to weather types.By using linear and curvilinear regression methods,the relationship models between longan canopy temperature and observation station air temperature were established.The models for cloudy,rainy and advection chilling injury had better effects than those for sunny,cloudy to sunny and radiation chilling injury;the models for night were better than those for daytime and the whole day.[Conclusion] To some extent,applying the relationship models between longan canopy temperature and observation station air temperature could make up the shortcoming of meteorological data which were higher than the real values.

Canopy Temperature Depression as a Potential Selection Criterion for Drought Resistance in Wheat

Field studies were conducted at Bushland, Texas, USA, in 2004 to examine usefulness of canopy temperature depression （CTD）, the difference of air-canopy temperature, in screening wheat （Triticum aestivum L.） genotypes for yield under dryland and irrigated. Forty winter wheat genotypes were grown under irrigation and dryland. CTDs were recorded after heading between 1 330 and 1 530 h on 6 clear days for dryland and 9 days for irrigation. Drought susceptible index （DSI） for each genotype was calculated using mean yield under dryland and irrigated conditions. Genotypes exhibited great differences in CTD under each environment. The dryland CTDs averaged 1.33℃ ranging from -0.67 to 2.57℃, and the average irrigation CTD were 4.59℃ ranging from 3.21 to 5.62℃. A low yield reduction was observed under dryland conditions relative to irrigated conditions for high-CTD genotypes. CTD values were highly negatively correlated with DSI under dryland, and genotypes of CTDs = 1.3℃ in dryland condition were identified as drought resistant. For 21 genotypes classified as drought resistant by DSI, their CTDs were 1.68℃ for dryland and 4.35℃ for irrigation on average; for 19 genotypes classified as drought susceptible by DSI, average CTD was 0.94℃ in dryland and 4.85℃ in irrigation. The high-yield genotypes consistently had high CTD values, and the low-yield ones had low CTD values for all measurements in dryland. After heading, genotypes maintained consistent ranking for CTD. Regression results for CTD and yield suggested that the best time for taking CTD measurement was 3-4 weeks after heading in irrigation but any time before senescence in dryland. Crop water stress index （CWSI） calculated from CTD data was highly correlated with CWSI calculated from yield, which suggesting traditional costly CWSI measurement may be improved by using portable infrared thermometers. Most importantly, grain yield was highly correlated with CTD under dryland （R^2 = 0.79-0.86） and irrigation （R^2 = 0.46-0.58） conditions. These results clearly indicated grain yield and water stress can be predicted by taking CTD values in field, which can be used by breeding programs as a potential selection criterion for grain yield and drought resistance in wheat, but a second study year is needed to confirm further.

Relationship Between Canopy Temperature at Flowering Stage and Soil Water Content,Yield Components in Rice

The canopy temperature of rice at the flowering stage and the soil water content were investigated under different soil water treatments （the soil water contents were 24%, 55%, 90% and 175% at the flowering stage）. The canopy temperature was lower than air temperature, and the soil water content significantly influenced the canopy temperature. The lower the soil water content, the higher the canopy temperature, the less the accumulative absolute value of canopy-air temperature difference. Moreover, the maximum difference between treatments and CK in the accumulative absolute value of canopy-air temperature difference appeared at 13：00 μm. in a day, thus, it could be considered as a suitable measuring time. Under the lowest water content treatment, the peak flowering occurred in the first three days （about 70% of panicles flowered）, resulting in shortened and lightened panicle of rice. As to the CK and the high water content treatments, the peak flowering appeared in the middle of flowering duration, with longer panicle length and higher panicle weight. Results indicated the lower the soil water content, the less the filled grain number and grain yield.

Active Management of Plant Canopy Temperature as a Tool for Modifying Plant Metabolic Activity

The relationship between a plant and its thermal environment is a major determiner of its growth and development. Since plants grow and develop within continuously variable thermal environments, they are subjected to continuous thermal variation over their life cycle. Transpiration serves to uncouple the temperature of the plant from that of its environment in a manner that reduces the occurrence of high temperature stresses that can limit plant performance. In some agriculturally important plants, there are desirable metabolic outcomes that are associated with specific stress events (e.g. wine grapes). In these plants it is often desirable to induce temperature and water stresses of known magnitude and duration at specific points in the growing season. In this study we used a computer-controlled irrigation system that used cotton canopy temperature to control irrigation in greenhouse-grown plants over a 10-day period. The system was designed to irrigate in a manner that altered the canopy temperature relative to specific temperature thresholds (28°C, 30°C, 32°C and 34°C). The results demonstrate that automated irrigation management based on canopy temperature is capable of altering the temporal pattern of canopy temperature in a desired manner using a feed-back loop. Potential limitations on this action are related to the range of air temperatures, radiation and humidity within the environment.

Continuously Monitored Canopy Temperature as a Proxy for Plant Water Status

Water deficits are major limiters of crop yield worldwide. The detection of water deficits can be difficult. Measurements of the aerial and soil environment are often used to infer the water status and detect water deficits. Since crop yield accumulates incrementally and cumulatively over seasonal time scales, continuous direct monitoring of the water status of the crop may provide needed insight into plant/environment interactions. Canopy temperature can be measured near continuously on seasonal scales in the field. Cotton was grown under 11 irrigation regimes in 2009 and 2010 with water deficits from 26% to 86% of crop evapotranspiration. Yield varied accordingly from ~500 kg·ha-1 to ~2600 kg·ha-1. Canopy temperature was measured on a 15-minute interval for ~65 days in each year. Yield was described by a linear function of total water (irrigation + rain) for each year with similar slopes and different intercepts. When canopy temperature was used as a surrogate for total water, yield was linearly related to daytime leaf-to-air VPD, mean seasonal canopy temperature, mean seasonal daytime canopy temperature, and cumulative seasonal daytime canopy temperature. Limiting the analysis to daytime periods improved the ability to account for yield variation. Mean daytime seasonal canopy temperature and cumulative seasonal daytime temperature were most effective in accounting for yield variation across the seasons with a single regression line for both years.

Reciprocal Analysis of Sensible and Latent Heat Fluxes in a Forest Region Using Single Height Temperature and Humidity Based on the Bowen Ratio Concept

Evapotranspiration in forests has been researched for a long time because it serves an important role in water resource issues and biomass production. By applying the reciprocal analysis based on the Bowen ratio concept to the canopy surface, the sum result of sensible and latent heat fluxes, i.e., actual evapotranspiration (ET), is estimated from engineering aspect using the net radiation (Rn) and heat flux into the ground (G). The new method uses air temperature and humidity at a single height by determining the relative humidity (rehs) using the canopy temperature (Ts). The validity of the method is confirmed by the latent heat flux (lE) and sensible heat flux (H) observed by mean of eddy covariance method. The heat imbalance is corrected by multiple regression analysis. The temporal change of lE and H at the canopy surface is clarified using hourly and yearly data. Furthermore, the observed and estimated monthly evapotranspiration of the sites are compared. The research is conducted using hourly data and the validation of the method is conducted using observed covariance at five sites in the world using FLUXNET.

Effects of shrubs and precipitation on spatial-temporal variability of soil temperature in microhabitats induced by desert shrubs

Soil temperatures at 0, 5, 10 and 20 cm depths were monitored cominuously at different microhabitats （beneath shrub canopy （BSC）; bare intershrub spaces （BIS）） induced by xerophytic shrub （Caragana korshinskii Kom.） canopy, respectively. We mainly aimed to assess the effects of shrub canopy and precipitation on the spatial-temporal variability of soil temperature. Results indi- cate that both precipitation and vegetation canopy significantly affect soil temperature. In clear days, soil temperatures within the BSC area were significantly lower than in the BIS at the same soil depth due to shading effects of shrub canopy. Diurnal variations of soil temperature show a unimoclal sinusoidal curve. The amplitude of soil temperature tended to decrease and a hysteresis of di- urnal maximum soil temperature existed at deeper soil layers. Vertical fluctuations of soil temperature displayed four typical curves. In the nighttime （approximately from sunset to sunrise）, surface temperature within the BSC area was higher than in the BIS. In rainy days, however, soil temperatures were affected mainly by precipitation and the shrub canopy had a negligible effect on soil temperature, and little difference in soil temperature at the same soil depth was found between the BSC area and in the BIS. Diurnal variations in soil temperature decreased exclusively as rainfall continued and the vertical fluctuations of soil tempera~＇e show an increased tendency with increasing soil depth.

The Effect of Organ Temperature on Total Yield of Transplanted and Direct-Seeded Rice(Oryza sativa L.)

The canopy temperature of rice is an important index that directly reflects the growth and physiological state of rice,and affects the yield of rice plants to a great extent.The correlation between the temperatures of different rice organs and canopy in different growth stages and the grain yield is complex.The stability and universality of these correlations must be verified.We conducted a pot experiment using two rice varieties and two temperature treatments(high temperature treatment was carried out at the beginning of heading stage for 10 days).We measured rice organ temperature during seven stages of growth using a high-precision infrared thermal imager.Results showed that the optimal observation period for the rice canopy temperature was 13:00.Although the rice variety did not significantly impact the canopy or organ temperature(p>0.05),the different organs and canopy exhibited significantly different temperatures(p<0.05).The correlations between the leaf,stem,panicle,canopy–air temperature differences and seed setting rate,theoretical and actual yields were the strongest during the milk stage.Among them,the correlation coefficient betweenΔT_(s) and theoretical and actual yields was the highest,the relationship between theoretical yield(Y)andΔT_(s)(X)was Y=−5.6965X+27.778,R^(2)=0.9155.Compared withΔT_(l),ΔT_(p) andΔTc,ΔT_(s) was closely related to the main traits of plants.ΔT_(s) could better reflect the growth characteristics of rice thanΔT_(c),such as dry matter accumulation(r=−0.931),SPAD(r=0.699),N concentration(r=0.714),transpiration rate(r=−0.722).In conclusion,stem temperature was more important indicator than canopy temperature.Stem temperature is a better screening index for rice breeding and cultivation management in the future.

核电站控制棒驱动机构Canopy焊缝焊接温度场和应力-应变场模拟

目的研究机加工和拉拔2种成形方式下得到的填充环对Canopy焊缝的影响,获取焊接焊缝成形、焊接残余应力和变形的相关数据,以指导Canopy焊缝焊接工艺。方法采用数值模拟的方法,建立Canopy焊缝焊接数值分析模型,模拟焊接温度场、焊接残余应力和焊接残余变形。结果拉拔成形环焊接熔池高度为9 mm,机加工成形环焊接熔池高度为8.3 mm;机加工成形环焊接最大残余应力为255.6 MPa,而拉拔成形环焊接最大残余应力为277.8 MPa,均出现在管座紧贴焊缝的位置;机加工成形环焊接残余变形为0.19 mm,拉拔成形环焊接残余变形为0.186 mm,最大残余变形均出现在焊接起始位置附近,在焊缝与管座交接的位置。结论熔池形貌直接影响了热影响区域的大小,拉拔Y型环焊接熔池高度更大,焊接的热影响区域更大;拉拔Y型环焊接残余应力略大于机加工Y型环焊接残余应力;机加工成形环和拉拔成形环焊接残余变形相近。

Ca(NO3)2 canopy spraying during physiological fruit drop period has a better influence on the tree character and fruit quality of Newhall navel orange(Citrus sinensis Osbeck)

This study aimed to provide a theoretical basis for adopting suitable cultivation measures to tackle calcium （Ca） deficiency in citrus leaves. The Newhall navel orange （Citrus sinensis Osbeck） canopy was sprayed with 20.0 mmol L-1 of Ca（NO3）2 during physiological fruit drop period, fruit expanding period, and fruit maturing period on 30, 90, and 210 days after full bloom （DAFB）, respectively, and its effects on leaf gas exchange parameters and leaf mineral nutrition and fruit quality were analyzed. The results showed that： （1） The photosynthetic rate （ACO2） at 9：00 a.m. and 16：00 p.m. of fruit expanding period with 30 and 90 DAFB Ca（NO3）2treatments slightly or significantly improved mainly by decreasing stomatal limitation and nonstomatal limitation, respectively. （2） Compared with control （CK）, the Ca concentration in leaves with 30, 90, and 240 DAFB Ca（NO3）2 treatments increased by 127.16; 97.53, and 33.33%, respectively, and the leaf magnesium concentra- tion also increased by more than 32.26%. However, Ca（NO3）2 canopy spraying on 30 DAFB significantly reduced the leaf potassium concentration, by 22.14% compared with CK. （3） Ca（NO3）2 canopy spraying on 30 DAFB decreased the second fruit drop rate by 30.55% and increased the weight per fruit by 25.04%, thus resulting in a significant increase in citrus yield. （4） Spraying Ca（NO3） on 30 DAFB mainly affected the metabolism of titratable acid （TA） to improve the maturity of citrus fruits. Whilst it improved the external quality and the coloring of citrus fruit significantly. Therefore, Ca（NO3）2 canopy spraying during physiological fruit drop period has a better influence on the tree character and fruit quality of Newhall navel orange （Citrus sinensis Osbeck）.

Mobile Open-Source Plant-Canopy Monitoring System

Many agricultural applications, including improved crop production, precision agriculture, and phenotyping, rely on detailed field and crop information to detect and react to spatial variabilities. Mobile farm vehicles, such as tractors and sprayers, have the potential to operate as mobile sensing platforms, enabling the collection of large amounts of data while working. Open-source hardware and software components were integrated to develop a mobile plant-canopy sensing and monitoring system. The microcontroller-based system, which incorporated a Bluetooth radio, GPS receiver, infrared temperature and ultrasonic distance sensors, micro SD card storage, and voltage regulation components, was developed at a cost of US$292. The system was installed on an agricultural vehicle and tested in a soybean field. The monitoring system demonstrates an application of open-source hardware to agricultural research and provides a framework for similar or additional sensing applications.

基于变量灌溉动态分区管理的冬小麦产量与节水效果

喷灌机机载式红外温度传感器系统是动态监测农田作物水分亏缺状况、构建变量灌溉(variable rate irrigation,VRI)决策支持系统的重要工具。为了评估圆形喷灌机机载式红外温度传感器系统在变量灌溉动态分区管理中的应用效果,该研究以气象参数和土壤水分传感器网络构建的均一灌溉(uniform rate irrigation, URI)决策方法为对照,评估了基于气象参数、土壤水分传感器网络和作物冠层温度的变量灌溉决策方法对华北平原冬小麦灌溉制度、土壤含水率空间分布均匀性和节水增产效果的影响。在河北省邢台市大曹庄中国水利水电科学研究院智慧灌溉技术与装备创新示范推广基地开展试验,试验区为三跨加悬臂圆形喷灌机控制灌溉面积7.07 hm^(2),2021年试验区等分为2个子区,布置URI和VRI处理,2022年试验区等分为4个子区,布置URI处理、基于等间隔法进行管理区聚类划分的VRI(T1)处理、基于“Jenks”自然断点法进行管理区聚类划分的VRI(T2)处理和基于几何间隔断点法进行管理区聚类划分的VRI(T3)处理。结果表明,在冬小麦生育期内,URI和VRI处理灌水7~10次,2 a平均灌水量分别为201和173 mm。开展VRI管理后,冬小麦主根区的土壤含水率空间分布均匀性和产量均匀性提高。2021年URI和VRI处理的冬小麦产量分别为9 470和9 574 kg/hm^(2),2022年的冬小麦产量较2021年分别降低6.7%和6.0%。变量灌溉处理的管理区聚类划分方法未对灌溉制度和产量产生显著影响。与URI处理相比,VRI处理能够减少灌溉水量,且对产量和水分利用效率无显著影响。研究结果可为基于喷灌机机载式红外温度传感器系统的变量灌溉动态分区管理方法的建立提供指导,为变量灌溉决策支持系统的开发升级提供技术支持。

六盘山区华北落叶松人工林小气候特征

【目的】实测华北落叶松(Larixgmelinii var.principis-rupprechtii)人工林的林内和林窗小气候特征,认识森林的小气候调节作用,为促进林下更新和森林多种功能利用提供科学依据。【方法】在宁夏六盘山南部半湿润区,建立林内(林龄40 a,郁闭度0.52)和林窗(面积750 m^(2))小气候观测样地,用自动气象站从2022年12月起连续一年监测气象指标和10 cm深土壤温度湿度,并依据标准气象站数据与海拔的关系线性插值得到林外气象数据作为对照。【结果】与林外相比,林内和林窗有明显的小气候调节作用,这表现在:1)年均太阳辐射日累积值(MJ/m^(2))为林内(4.53)<林窗(8.87)<林外(13.99),林内和林窗仅为林外的32.4%和63.4%;林内和林窗与林外的月均太阳辐射累积值的差在生长季大于非生长季。2)年均气温(℃)为林内(7.2)<林外(7.5)<林窗(7.8),气温日较差(℃)为林内(6.1)<林窗(6.3)<林外(8.0),林内和林窗的气温变化更平缓;林内、林窗、林外之间的气温差平均值在生长季小于非生长季。3)年均空气相对湿度(%)为林内(69.1)>林窗(64.7)>林外(62.5),林内和林窗比林外提高了6.6%和2.2%,林内和林窗在生长季提高空气湿度的能力大于非生长季。4)10 cm深土壤温度年均值(℃)为林内(6.8)<林窗(8.8)<林外(9.1),林内和林窗比林外低2.3℃和0.3℃;土壤温度日较差(℃)为林内(0.7)<林窗(1.5)<林外(4.5);林内和林窗土壤温度与林外相比在生长季降低但在冬季提高。5)10 cm深土壤湿度年均值(%)为林内(24.4)<林窗(29.8)<林外(33.8),林内和林窗比林外降低了9.4%和4.0%,林内与林外土壤湿度差在生长季小于非生长季,林窗与林外土壤湿度差在生长季大于非生长季。【结论】华北落叶松人工林的小气候调节作用明显,且在生长季大于非生长季。与林外相比,林内和林窗大幅降低了太阳辐射、土壤温度、土壤湿度,但显著提高了空气湿度,还减小了各指标变幅、调节了峰值时间,对空气温度有良好的调控缓冲作用。

基于冠气温差的温室黄瓜蒸散量模拟

通过建立基于不同时刻冠气温差(T c-T a)的温室黄瓜日蒸散量(ET c)估算模型,分析了基于不同时刻T c-T a对估算ET c的准确性;同时,基于T c-T a构建了估算黄瓜不同生育期ET c的Jackson模型,并将模型估算结果与基于冠层阻力参数(r c)的Penman-Monteith模型及蒸渗仪实测数据进行比较,结果显示,基于14:00的T c-T a构建的Jackson模型,估算温室黄瓜ET c的精确度最高(R 2为0.937),误差最小(RMSE为0.722 mm/d);相比Penman-Monteith模型(R 2为0.964),基于T c-T a的Jackson经验模型对黄瓜ET c估算结果与实测值相关性更高(R 2为0.967),误差更小(RMSE为0.735 mm/d).研究结果可为温室ET c模拟以及节水灌溉智能决策提供科学依据.

施钾对夏花生产量、品质及光温生理特性的影响

【目的】探究不同施钾水平对夏花生产量、品质及生育期钾素积累动态、光温生理特性和根系形态的影响,为花生合理施钾提供科学依据。【方法】2021—2022年在河南省温县进行钾肥用量田间试验,供试品种为豫花22,设施钾量0(K0)、45 kg·hm^(-2)(K45)、90 kg·hm^(-2)(K90)、135 kg·hm^(-2)(K135)和180 kg·hm^(-2)(K180)5个处理,于成熟期测定夏花生荚果产量和品质,并分别于苗期、花针期、结荚期、饱果期测定叶片SPAD值、冠层光合有效辐射和冠层温度,分析植株钾积累量和根系形态。【结果】随施钾量增加,两年度花生荚果产量可分别用“线性+平台”和“一元二次方程”拟合,适宜施钾量分别为164和135 kg·hm^(-2),施钾处理平均增产17%。成熟期籽粒粗蛋白、含油量和氨基酸含量均随施钾量增加呈先升高后趋于稳定趋势。与不施钾相比,施钾处理籽粒粗蛋白、含油量和氨基酸含量两年度平均增幅分别为7.85%、3.98%和13.97%,效果显著。运用Logistic方程对夏花生钾素积累量进行非线性回归拟合,得出施钾主要提高了花生钾素最大积累速率(Vmax)和平均积累速率(Vmean),推迟吸收峰值的出现(Tmax),延长快速积累期(Δt)与活跃积累期(Taas),促进夏花生持续快速生长发育。此外,各生育时期冠层最高温、最低温与平均温度均随施钾量的增加显著降低;施钾135 kg·hm^(-2)可显著增加花生叶片SPAD值与冠层光合有效辐射量(APAR)和分量(FPAR),并对根系形态具有积极影响。【结论】合理施钾可显著提高夏花生产量、改善品质、促进钾素积累利用并显著改善生育期光温生理性能。本试验条件下夏花生推荐施钾量为135—160 kg·hm^(-2)。

城市森林结构多样性预测冠下地面温度的潜力研究

城市森林冠层具有调控城市森林微气候的能力,但现有研究尚未阐明冠层结构对冠下地面温度的影响及其预测潜力。文章基于无人机机载激光雷达(UAV-LiDAR)提取哈尔滨林业示范基地的城市森林冠层结构多样性特征指标,探究单一结构多样性特征对冠下地面温度的影响,以及结构多样性多因子组合对温度的预测潜力。结果表明:1)城市森林结构多样性的8个特征因子与冠下地面温度呈显著相关关系(P<0.05),其中深间隙(DG)、深间隙分数(DGF)、覆盖分数(CF)、间隙分数分布(GFP)表征了结构多样性的覆盖/开放度特征;冠层高度标准差(H_(std))、冠层高度最大值(H_(max))、95%分位点高度(ZQ_(95))表征了高度特征;垂直复杂指数(VCI)表征了异质性特征。2)城市森林冠层结构多样性的覆盖/开放度特征对冠下地面温度的响应更强(R^(2)为0.15~0.5),强于高度指标(R^(2)为0.14~0.19)以及异质性指标(R^(2)=0.14)。3)结合高度指标、覆盖/开放度指标以及异质性指标的多因子预测模型2(R^(2)=0.61,RMSE=0.51,MSE=0.26,AIC=62.74),对于冠下地面温度的预测性能更优。研究明晰了城市森林结构多样性的多因子变量及其特征组合预测冠下地面温度的潜力,为城市森林冠层结构调控内部小气候环境研究提供了科学参考。

基于水稻冠层多信息融合的监测褐飞虱种群大小的BP神经网络方法

【目的】褐飞虱Nilaparvata lugens种群监测的自动化和智能化尚未实现。本研究旨在探究水稻受褐飞虱危害后冠层光谱和温度以及叶片叶绿素相对含量与为害虫量的关系,建立基于高光谱、热成像和叶绿素等多信息融合的误差反向传播(back propagation,BP)神经网络监测褐飞虱的方法,为田间褐飞虱种群监测向自动化与智能化方向发展提供方法支持。【方法】在可控条件下利用方形塑料框培育水稻,并在分蘖期接入雌雄1∶1配对的不同对数(0,1,2,3,4,5,6和7对)的褐飞虱雌、雄成虫,然后连续多次(接虫后16,27,32,44和60 d时)调查接虫区水稻上褐飞虱虫量(每4穴稻上个体数),并采用高光谱仪和热成像仪分别测定水稻冠层光谱反射率和冠层温度,利用土壤和植物分析仪器开发(soil and plant analyzer development,SPAD)叶绿素仪测定叶片叶绿素的相对含量(SPAD值);采用Pearson相关法分析各测量指标与褐飞虱虫量的相关性;采用多元散射校正对光谱反射率数据进行降噪处理;采用连续投影算法对高光谱反射率数据进行降维和敏感波段筛选;分别以光谱反射率单一信息及其与冠层温度和SPAD值融合后的多源信息为输入量,采用普通和加入粒子群算法优化的BP神经网络建模,构建褐飞虱为害不同时段后种群大小的神经网络监测模型。【结果】褐飞虱为害后水稻冠层光谱在近红外的730-930 nm波段反射率、水稻冠层温度与气温的差值(冠气温差)和叶片的SPAD值均与褐飞虱虫量呈显著负相关。利用连续投影算法筛选出的冠层光谱敏感波段处反射率并降噪后建立的BP神经网络监测5个危害时段褐飞虱虫量的预测集决定系数R^(2)在0.504~0.892之间;融合冠层光谱、冠气温差和叶片SPAD值等多信息建立的BP神经网络监测褐飞虱虫量的预测集R^(2)提升到0.640~0.975;在多源信息基础上再选用粒子群优化(particle swarm optimization,PSO)算法优化BP神经网络后监测褐飞虱虫量的精度提高,预测集R^(2)提升到0.931~0.991,模型预测效果好。【结论】基于水稻冠层高光谱与热成像和叶片SPAD值等多信息融合的PSO-BP神经网络方法监测褐飞虱虫量的精度高、效果好,有望用于田间褐飞虱种群的自动监测。