Leaf area index （LAI） is used for crop growth monitoring in agronomic research, and is promising to diagnose the nitrogen （N） status of crops. This study was conducted to develop appropriate LAI-based N diagnostic...Leaf area index （LAI） is used for crop growth monitoring in agronomic research, and is promising to diagnose the nitrogen （N） status of crops. This study was conducted to develop appropriate LAI-based N diagnostic models in irrigated lowland rice. Four field experiments were carried out in Jiangsu Province of East China from 2009 to 2014. Different N application rates and plant densities were used to generate contrasting conditions of N availability or population densities in rice. LAI was determined by LI-3000, and estimated indirectly by LAI-2000 during vegetative growth period. Group and individual plant characters （e.g., tiller number （TN） and plant height （H）） were investigated simultaneously. Two N indicators of plant N accumulation （NA） and N nutrition index （NNI） were measured as well. A calibration equation （LAI=1.7787LAI2o00-0.8816, R2=0.870＂） was developed for LAI-2000. The linear regression analysis showed a significant relationship between NA and actual LAI （R2=0.863^＊＊）. For the NNI, the relative LAI （R2=0.808-） was a relatively unbiased variable in the regression than the LAI （R^2=0.33^＊＊）. The results were used to formulate two LAI-based N diagnostic models for irrigated lowland rice （NA=29.778LAI-5.9397; NNI=0.7705RLAI＋0.2764）. Finally, a simple LAI deterministic model was developed to estimate the actual LAI using the characters of TN and H （LAI=-0.3375（THxHx0.01）2＋3.665（TH×H×0.01）-1.8249, R2=0.875＊＊）. With these models, the N status of rice can be diagnosed conveniently in the field.展开更多
Leaf area index(LAI)is one of the most important characteristics of forest stands that affects the fundamentals of tree physiological processes,biomass production,and mechanical stability.The LAI results obtained by t...Leaf area index(LAI)is one of the most important characteristics of forest stands that affects the fundamentals of tree physiological processes,biomass production,and mechanical stability.The LAI results obtained by the semi-direct and indirect methods(the needle technique and an LAI-2000 PCA)in three European beech(Fagus sylvatica L.)stands and one sycamore maple(Acer pseudoplatanus L.)stand were compared with LAI estimated by litter traps during the 2013 growing season.Seasonal LAI was estimated using an LAI-2000 PCA which showed similar trends among the stands and strongly corresponded to phenological phases of deciduous stands in Europe,with the fastest rate of leaf area increment occurring during the first month following bud break.During the growing season,maximum stand LAI value was on June 19th and reached 4.5–5.1,and 4.0 in the beech and maple stands,respectively.The needle technique significantly underestimated(p<0.05)direct LAI on average by 22.0% and 40.0% in the beech and maple stands,respectively.The LAI-2000 PCA insignificantly underestimated(p>05)LAI on average by 15.1%and 5.8%in the beech and maple stands,respectively.All methods for LAI estimation at the stand level could be applicable in deciduous forest stands(beech,maple)with similar site and stand characteristics.However,calibration by direct method is necessary to obtain the required precision.展开更多
利用光学仪器法能够快速、高效地测定森林生态系统的叶面积指数(leaf area index,LAI)。然而,评估该方法测定针阔混交林LAI季节动态准确性的研究较少。该研究基于凋落物法测定了小兴安岭地区阔叶红松(Pinus koraiensis)林LAI的季节动态...利用光学仪器法能够快速、高效地测定森林生态系统的叶面积指数(leaf area index,LAI)。然而,评估该方法测定针阔混交林LAI季节动态准确性的研究较少。该研究基于凋落物法测定了小兴安岭地区阔叶红松(Pinus koraiensis)林LAI的季节动态,其结果可代表真实的LAI。参考真实的LAI,对半球摄影法(digital hemispherical photography,DHP)和LAI-2000植物冠层分析仪测定的有效叶面积指数(effective LAI,Le)进行了评估。首先对DHP测定LAI过程中采用的不合理曝光模式(自动曝光)进行了系统校正。同时,测定了光学仪器法估测LAI的主要影响因素(包括木质比例(woody-to-total area ratio,α)、集聚指数(clumping index,E)和针簇比(needle-to-shoot area ratio,γE))的季节变化。结果表明:3种不同方法测定的LAI均表现为单峰型的季节变化,8月初达到峰值。从5月至11月,DHP测定的Le比真实的LAI低估50%–59%,平均低估55%;而LAI-2000植物冠层分析仪测定的Le比真实的LAI低估19%–35%,平均低估27%。DHP测定的Le经过自动曝光,α、E和γE校正后,精度明显提高,但仍比真实的LAI低估6%–15%,平均低估9%;相对而言,LAI-2000植物冠层分析仪测定的Le经过α、E和γE校正后,精度明显提高,各时期与真实的LAI的差异均小于9%。研究结果表明,考虑木质部和集聚效应对光学仪器法的影响后,DHP和LAI-2000植物冠层分析仪均能相对准确地测定针阔混交林LAI的季节动态,其中,DHP的测定精度高于85%,而LAI-2000植物冠层分析仪的测定精度高于91%。展开更多
In order to test the accuracy of the usually-used fixed calibration factor of the canopy scanner of LAI-2000 for measuring the leaf area index(LAI),a Larix principis-rupprechtii plantation was chosen in the small wate...In order to test the accuracy of the usually-used fixed calibration factor of the canopy scanner of LAI-2000 for measuring the leaf area index(LAI),a Larix principis-rupprechtii plantation was chosen in the small watershed of Xiangshuihe located at the Liupan Mountains of Ningxia Hui Autonomous Region of NW China,the LAI was measured in October 2010,a period from full canopy to the total fall of needles,by using both the LAI- 2000 and litterfall collection method.Then,a comparison was made between the LAI values determined by the litter-fall collection and that calculated based on the figures read from LAI-2000 and the fixed calibration factor(1.49).It showed that the average of LAI measurements of the 2 methods was very close,with a difference of only 5%.However,the calculated LAI from LAI-2000 was obviously higher than the true values determined by litter-fall collection when the canopy was full of needles;and obviously lower than the true value when the canopy was sparse after needle falling.The reason may be that LAI-2000 takes the projection of twigs as needles.So,a dynamic calibration factor is needed,especially in the seasons when the needle amount and the percentage of twigs projection in crown projection change quickly.Therefore,a statistic relation in a quadratic polynomial form between the 2 series of LAI data was well fitted. This relation can be used for a more accurate estimation of LAI based on the data read from the easilyused canopy scanners like LAI-2000.展开更多
基金supported by the Special Program for Agriculture Science and Technology from the Ministry of Agriculture of China (201303109)the National Key Research & Development Program of China (2016YFD0300604+3 种基金 2016YFD0200602)the Fundamental Research Funds for the Central Universities,China (262201602)the Priority Academic Program Development of Jiangsu Higher Education Institutions of China (PAPD)the 111 Project of China (B16026)
文摘Leaf area index （LAI） is used for crop growth monitoring in agronomic research, and is promising to diagnose the nitrogen （N） status of crops. This study was conducted to develop appropriate LAI-based N diagnostic models in irrigated lowland rice. Four field experiments were carried out in Jiangsu Province of East China from 2009 to 2014. Different N application rates and plant densities were used to generate contrasting conditions of N availability or population densities in rice. LAI was determined by LI-3000, and estimated indirectly by LAI-2000 during vegetative growth period. Group and individual plant characters （e.g., tiller number （TN） and plant height （H）） were investigated simultaneously. Two N indicators of plant N accumulation （NA） and N nutrition index （NNI） were measured as well. A calibration equation （LAI=1.7787LAI2o00-0.8816, R2=0.870＂） was developed for LAI-2000. The linear regression analysis showed a significant relationship between NA and actual LAI （R2=0.863^＊＊）. For the NNI, the relative LAI （R2=0.808-） was a relatively unbiased variable in the regression than the LAI （R^2=0.33^＊＊）. The results were used to formulate two LAI-based N diagnostic models for irrigated lowland rice （NA=29.778LAI-5.9397; NNI=0.7705RLAI＋0.2764）. Finally, a simple LAI deterministic model was developed to estimate the actual LAI using the characters of TN and H （LAI=-0.3375（THxHx0.01）2＋3.665（TH×H×0.01）-1.8249, R2=0.875＊＊）. With these models, the N status of rice can be diagnosed conveniently in the field.
基金supported by the Specific University Research Fund of the Faculty of Forestry and Wood Technology(FFWT)at Mendel University in Brno(Grant No.LDF_VP_2016017)the Ministry of Agriculture of the Czech Republic,institutional support MZE-RO0118。
文摘Leaf area index(LAI)is one of the most important characteristics of forest stands that affects the fundamentals of tree physiological processes,biomass production,and mechanical stability.The LAI results obtained by the semi-direct and indirect methods(the needle technique and an LAI-2000 PCA)in three European beech(Fagus sylvatica L.)stands and one sycamore maple(Acer pseudoplatanus L.)stand were compared with LAI estimated by litter traps during the 2013 growing season.Seasonal LAI was estimated using an LAI-2000 PCA which showed similar trends among the stands and strongly corresponded to phenological phases of deciduous stands in Europe,with the fastest rate of leaf area increment occurring during the first month following bud break.During the growing season,maximum stand LAI value was on June 19th and reached 4.5–5.1,and 4.0 in the beech and maple stands,respectively.The needle technique significantly underestimated(p<0.05)direct LAI on average by 22.0% and 40.0% in the beech and maple stands,respectively.The LAI-2000 PCA insignificantly underestimated(p>05)LAI on average by 15.1%and 5.8%in the beech and maple stands,respectively.All methods for LAI estimation at the stand level could be applicable in deciduous forest stands(beech,maple)with similar site and stand characteristics.However,calibration by direct method is necessary to obtain the required precision.
文摘利用光学仪器法能够快速、高效地测定森林生态系统的叶面积指数(leaf area index,LAI)。然而,评估该方法测定针阔混交林LAI季节动态准确性的研究较少。该研究基于凋落物法测定了小兴安岭地区阔叶红松(Pinus koraiensis)林LAI的季节动态,其结果可代表真实的LAI。参考真实的LAI,对半球摄影法(digital hemispherical photography,DHP)和LAI-2000植物冠层分析仪测定的有效叶面积指数(effective LAI,Le)进行了评估。首先对DHP测定LAI过程中采用的不合理曝光模式(自动曝光)进行了系统校正。同时,测定了光学仪器法估测LAI的主要影响因素(包括木质比例(woody-to-total area ratio,α)、集聚指数(clumping index,E)和针簇比(needle-to-shoot area ratio,γE))的季节变化。结果表明:3种不同方法测定的LAI均表现为单峰型的季节变化,8月初达到峰值。从5月至11月,DHP测定的Le比真实的LAI低估50%–59%,平均低估55%;而LAI-2000植物冠层分析仪测定的Le比真实的LAI低估19%–35%,平均低估27%。DHP测定的Le经过自动曝光,α、E和γE校正后,精度明显提高,但仍比真实的LAI低估6%–15%,平均低估9%;相对而言,LAI-2000植物冠层分析仪测定的Le经过α、E和γE校正后,精度明显提高,各时期与真实的LAI的差异均小于9%。研究结果表明,考虑木质部和集聚效应对光学仪器法的影响后,DHP和LAI-2000植物冠层分析仪均能相对准确地测定针阔混交林LAI的季节动态,其中,DHP的测定精度高于85%,而LAI-2000植物冠层分析仪的测定精度高于91%。
文摘In order to test the accuracy of the usually-used fixed calibration factor of the canopy scanner of LAI-2000 for measuring the leaf area index(LAI),a Larix principis-rupprechtii plantation was chosen in the small watershed of Xiangshuihe located at the Liupan Mountains of Ningxia Hui Autonomous Region of NW China,the LAI was measured in October 2010,a period from full canopy to the total fall of needles,by using both the LAI- 2000 and litterfall collection method.Then,a comparison was made between the LAI values determined by the litter-fall collection and that calculated based on the figures read from LAI-2000 and the fixed calibration factor(1.49).It showed that the average of LAI measurements of the 2 methods was very close,with a difference of only 5%.However,the calculated LAI from LAI-2000 was obviously higher than the true values determined by litter-fall collection when the canopy was full of needles;and obviously lower than the true value when the canopy was sparse after needle falling.The reason may be that LAI-2000 takes the projection of twigs as needles.So,a dynamic calibration factor is needed,especially in the seasons when the needle amount and the percentage of twigs projection in crown projection change quickly.Therefore,a statistic relation in a quadratic polynomial form between the 2 series of LAI data was well fitted. This relation can be used for a more accurate estimation of LAI based on the data read from the easilyused canopy scanners like LAI-2000.
