CN103075980A - Method for measuring effective leaf area index (LAI) of rubber plantation by using LAI-2000 canopy analyzer - Google Patents
Method for measuring effective leaf area index (LAI) of rubber plantation by using LAI-2000 canopy analyzer Download PDFInfo
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Abstract
The invention relates to a method for measuring an effective leaf area index (LAI) of a rubber plantation by using an LAI-2000 canopy analyzer. The method comprises the following steps of: firstly measuring an A value on an open ground close to the rubber plantation to be measured, then measuring a B value of the rubber plantation and next quickly returning to the open ground to measure the A value again; exporting and saving original experimental measurement data by using software; establishing a linear interpolation equation by using measurement time and numerical values of the two A values and interpolating to generate a corresponding A value according to the measurement time of each B value; and saving an interpolation result and calculating the effective LAI by applying FV2200. According to the design of the invention, sky solar radiation changes linearly in a short time, a linear interpolation program is established according to the A value of the rubber plantation to be measured, a corresponding A value is generated for each B value, the problem of large error of the measurement result caused by use of a fixed A value in a single-probe mode of the LAI-2000 canopy analyzer is solved, the error of the measurement result is small, and the information on a vegetation canopy structure of the rubber plantation can be reflected better.
Description
Technical field
The invention belongs to the ecological study field, relate to a kind of assay method of ecologic structure parameter of rubber forest, specifically a kind of method of utilizing the LAI-2000 Canopy Analyzer to measure the rubber forest effective leaf area index.
Background technology
Leaf area index LAI(Leaf Area Index) be often referred to the summation of all blade table areas on the land area of one unit, or the summation of the planimetric area of plant leaf blade on the unit area.Leaf area index is an important parameter of vegetation canopy structure, the size of leaf area and distribution thereof directly affect many biophysics processes of vegetation, such as the intercepting and capturing of photosynthesis respiration, transpiration and precipitation, carbon energy etc., it also is an important parameter determining terrestrial ecosystems exchanges of mass and energy size simultaneously.
China has about 1,000,000 hectares rubber forest, and Measurement accuracy rubber forest leaf area index all has great importance to actual production and scientific research.At present, the LAI-2000 Canopy Analyzer at the most widely used instrument of ground survey vegetation canopy leaf area index, it utilizes " flake " optical sensor, by at 5 different angles directions (7o, 23o, 38o, 53o, 68o) measure on the vegetation canopy radiant quantity Calculate Leaf Area index of (Blow Canopy Value, abbreviation B value) under (Above Canopy Value is called for short A value) and canopy.Because instrument is not considered the crowding effect of blade, the leaf area index of utilizing LAI-2000 to measure is called effective leaf area index (effective LAI).
Utilizing LAI-2000 to measure the optimal method of effective leaf area index is to use two probes, and one is installed in vegetation canopy top measurement A value, and another measures the B value under canopy, then calculates effective leaf area index according to A value and B value.But because rubber tree (Hevea brasiliensis) is perennial high megaphanerophyte, it is high that one-tenth rubber tree in age can reach 15-20 rice, even higher, is difficult to measure above canopy the A value.Present most widely used method is to measure with the mode of a probe, its hypothesis solar radiation in of short duration Measuring Time is invariable, measuring the A value from the nearest open area of rubber forest first, under rubber forest, measure the B value again, then calculate effective leaf area index with fixing A value and B value.Be generally 10-20 minute owing in rubber forest, measure the time of B value, add measurement A value spent time, the A value of a woods section of perfect measurement and be about half an hour the averaging time of B value.In period, even ideal measurement weather---the cloudy day, the changeless hypothesis of A value also is false at this section, and changes more violent.Therefore, no matter be that employing B value is measured A value before, or the A value calculating effective leaf area index after the B value measurement end, all can there be larger measuring error, can not truly reflect the canopy structure information of rubber forest.
Summary of the invention
The objective of the invention is to provide for the deficiencies in the prior art a kind of method of the LAI-2000 of utilization Canopy Analyzer measurement rubber forest effective leaf area index, the A value causes the larger problem of measuring result error because using fixedly when having solved LAI-2000 Canopy Analyzer use single probe pattern.
Know-why of the present invention: because the A value changes more violent in whole measuring process, (on April 26th, 2012 is when measuring effective leaf area index in the rubber forest use LAI-2000 of Chinese Academy of Tropical Agricultural Sciences experimental plot Canopy Analyzer such as Fig. 1, the A value that first angle ring direction (7o) of instrument records is situation over time, measuring weather is the cloudy day), no matter be to adopt the B value to measure beginning A value before, or the B value is measured the A value after finishing, and all has very large measuring error.The present invention's hypothesis is within the of short duration time (less than 30 minutes), it aerial solar radiation is linear change, measure before the B value A value with latter two time point of end by being recorded in rubber forest to be measured, can determine the variation tendency of A value and set up the linear fit equation of A value.According to Measuring Time and the A value fit equation of each B value in the rubber forest to be measured, can generate a corresponding A value for each B value, its computing formula is as follows:
T wherein
s, t
eRepresent the B value measure before, measure twice A value Measuring Time after finishing,
,
Measured value (j=1,2,3,4,5) for corresponding j ring direction.Measuring Time according to i B value is t
i, then can calculate corresponding five A values of encircling directions by equation
Its interpolation synoptic diagram such as Fig. 2.
The advantage of using the B value to measure former and later two A values is the variation tendency of clear and definite A value.Even the incomplete linear variation of A value in the time range of measuring B value, the true horizon of A value when the A value that obtains according to the variation tendency interpolation still more can represent measurement B value.Therefore adopt the effective leaf area index of interpolation calculation more accurate than directly using constant A value.
The technical solution adopted in the present invention:
A kind of method of utilizing the LAI-2000 Canopy Analyzer to measure the rubber forest effective leaf area index, its step is as follows:
1, select the diffuse radiation sky of homogeneous or the weather of less sun altitude to measure, such as the 6:00-8:00 in morning of fine day, the 6:00-7:30 in afternoon perhaps the cloudy day, avoids cloudy weather as far as possible, and sky radiation changes very greatly.
2, near rubber forest to be measured, select the open ground to measure the A value, the position angle of A value measured in record simultaneously.The alternative condition of open ground: centered by measurement point, take 60 meters as radius (the rubber height of tree take 20 meters as example, 3 times of vegetation height radiuses are 60 meters), Jing Gai (View cap) angle of visibility is without pile or vegetation in the sector region of angle.
3, according to rubber forest sample area size to be measured, survey the B value of varying number.Measure route along rubber forest two row band diagonal line, distance is not less than 5 meters between two B value measurement points, and the position angle of measuring simultaneously the B value is identical with the A value.If direct sunlight is arranged, utilize the shade of the shade of the person or vegetation to block the optical lens of LAI-2000, avoid the sunshine direct projection.
4, after rubber forest B value was measured and finished, the A value was measured again with identical position angle in the open ground of return measurement A value rapidly.
5, use FV2000 or FV2200 software to derive measured data of experiment, preserve raw measurement data.
6, (program can be selected C++ according to linear interpolation equation design batch interpolation procedure, the development languages such as Java are realized at corresponding platform), start in batches interpolation procedure, open raw measurement data and carry out in batches interpolation (program reads the B value on each rubber forest sample ground and the Measuring Time of two A values of correspondence automatically, is that each B value interpolation generates corresponding A value).Interpolation saves as the text data file identical with raw data format with interpolation result after finishing.The linear interpolation equation is as follows:
T wherein
s, t
eRepresent the B value measure before, measure twice A value Measuring Time after finishing,
,
Measured value (j=1,2,3,4,5) for corresponding j ring direction.Measuring Time according to i B value is t
i, then can calculate respectively corresponding five A values of encircling directions by equation
7, utilize data file after FV2000 or FV2200 software are opened interpolation, calculate effective leaf area index.
The present invention (measures rubber forest A value and used time of B value by hypothesis a perfect measurement time period, being generally less than 30 minutes kinds) sky radiation is the mode of linear change, measure former and later two A value variation relations according to rubber forest to be measured, design linear interpolation procedure, utilize the method for linear interpolation to generate a corresponding A value for each B value, the A value causes the larger problem of measuring result error because using fixedly when having solved LAI-2000 Canopy Analyzer use single probe pattern, measuring result error is little, can reflect better rubber forest vegetation canopy structure information.
Description of drawings
Fig. 1 is with the A value temporal evolution figure of LAI-2000 Canopy Analyzer the 1st angle ring orientation measurement.
Fig. 2 is the A value interpolation synoptic diagram of LAI-2000 Canopy Analyzer DATA REASONING.
Embodiment
Below in conjunction with embodiment, the specific embodiment of the present invention is described in further detail.Following examples are used for explanation the present invention, but are not used for limiting the scope of the invention.The experimental technique of unreceipted actual conditions in the following example, usually according to normal condition, or the condition of advising according to manufacturer.
Result of study both domestic and external shows, has obvious correlationship between the red spectral band of vegetation leaf area index and remote sensing image, near-infrared band, NDVI, SR and the SAVI vegetation index.Therefore, can and not adopt the leaf area index of the inventive method and the correlativity between the remote sensing image data to weigh effect of the present invention by the contrast employing.
Embodiment
1, experiment content
The pass that the ruddiness (B3) of contrast rubber forest leaf area index and environmental satellite remote sensing image, near infrared (B4), normalized differential vegetation index (NDVI), ratio vegetation index (SR) and soil are regulated between the vegetation index (SAVI) is example, and the difference between the inventive method is adopted and do not adopt in comparative analysis.
2, experimental data
The rubber forest leaf area index data of Danzhou City, Hainan Province Chinese Academy of Tropical Agricultural Sciences experimental plot, concrete acquisition time is respectively in March, 2012 and 4 the end of month, wherein be 21 sampling points March, increased by 4 sampling points, totally 25 sampling points April on the basis in March.
Two scape environmental satellite CCD image datas, acquisition time are respectively on March 23rd, 2012 and on May 3rd, 2012, and are basically identical with the acquisition time of ground leaf area index.Two scape remote sensing images being carried out the FLAASH atmospheric correction processes.
3, LAI computing method
FV2200 insertion: according to the Measuring Time of B value under the rubber forest and the outer A value of woods section, for each B value is inserted one in batches from the nearest A value of Measuring Time.The result that the method is inserted is that each rubber forest will use at most two fixing A values and B value coupling Calculate Leaf Area index (FV2200 has realized this function, directly uses Import Records module to finish).Import complete rear namely automatically calculating and demonstration leaf area index numerical value.
Dynamic method of interpolation (the inventive method): start the LAI batch interpolation procedure of having developed, open the raw data file that LAI-2000 measures, program is according to the B value of each rubber forest and the Measuring Time of A value, generate in batches the A value of a correspondence for the dynamic interpolation of each B value, and interpolation result is saved as the text identical with raw data format.Use FV2200 to open the interpolation text after interpolation finishes, can automatically calculate and show the leaf area index data.
4, experimental result
Experimental result sees Table 1.
Pearson correlation coefficient between the different leaf area index computing method of table 1 and the HJ star CCD image data relatively
Illustrate: " insertion " in the method row shows when calculating, directly utilizes FV2200 by the rear Calculate Leaf Area index of the nearest A value of temporal interpolation that " method of interpolation " expression adopts the inventive method that the A value is carried out dynamic interpolation.* show to reach the level of signifiance that * * shows and reaches the utmost point level of signifiance.
The result of table 1 shows, no matter is to adopt insertion or method of interpolation, and the ruddiness (B3) of rubber forest leaf area index and environmental satellite CCD image, near infrared (B4) wave band are remarkable linear dependence between NDVI, SR, SAVI and the WDVI vegetation index.The result also shows simultaneously, being relevant between the leaf area index of employing interpolation calculation and the image data obviously is better than insertion, the lifting amplitude does not wait from 1%-11%, wherein the related coefficient of the near-infrared band on May 1 promotes the most obvious, rise to 0.678 by original 0.567, the lifting amplitude is 11.1%.The difference degree of the correlativity between two kinds of disposal routes and the remote sensing image is different, mainly is because the sky radiation situation of change difference during the leaf area index field survey causes.If sky solar radiation variations amplitude is little when measuring, the difference between two kinds of computing method is little, if instead sky radiation changes greatly, adopts the inventive method just more can be near actual value.
The above only is preferred implementation of the present invention; should be pointed out that for those skilled in the art, under the prerequisite that does not break away from the technology of the present invention principle; can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.
Claims (2)
1. method of utilizing the LAI-2000 Canopy Analyzer to measure the rubber forest effective leaf area index is characterized in that its step is as follows:
1), select the diffuse radiation sky of homogeneous or the weather of less sun altitude to measure;
2), near rubber forest to be measured, select the open ground to measure A value, the position angle of simultaneously record measurement A value;
3), according to rubber forest sample area size to be measured, the B value of survey varying number; Measure route along rubber forest two row band diagonal line, distance is not less than 5 meters between two B value measurement points, and the position angle of measuring simultaneously the B value is identical with the A value;
4), after rubber forest B value measure to finish, the A value is measured again with identical position angle in the open ground of return measurement A value rapidly;
5), use FV2000 or FV2200 software derivation measured data of experiment, preservation raw measurement data;
6), according to linear interpolation equation design interpolation procedure in batches, start in batches interpolation procedure, open raw measurement data and carry out the batch interpolation; Interpolation saves as the text data file identical with raw data format with interpolation result after finishing; The linear interpolation equation is as follows:
T wherein
s, t
eRepresent the B value measure before, measure twice A value Measuring Time after finishing,
,
Be the measured value (j=1,2,3,4,5) of corresponding j ring direction, the Measuring Time of i B value is t
i, corresponding A value is
7), utilize the data file after FV2000 or FV2200 software are opened interpolation, calculating effective leaf area index.
2. method according to claim 1 is characterized in that: the alternative condition of open ground: centered by measurement point, take 60 meters as radius, mirror lid angle of visibility is without pile or vegetation in the sector region of angle.
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Cited By (3)
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| CN107067433A (en) * | 2017-04-24 | 2017-08-18 | 电子科技大学 | A kind of leaf area index ground survey method based on digital image processing techniques |
| CN109373937A (en) * | 2018-12-10 | 2019-02-22 | 中国气象局兰州干旱气象研究所 | Vegetation canopy leaf area index measurement method |
| CN110702166A (en) * | 2019-09-29 | 2020-01-17 | 北京农业信息技术研究中心 | Device for measuring plant canopy parameters |
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| CN102829739A (en) * | 2012-08-21 | 2012-12-19 | 北京农业信息技术研究中心 | Object-oriented remote sensing inversion method of leaf area index of crop |
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| JP2011133451A (en) * | 2009-11-27 | 2011-07-07 | Kyushu Univ | Optical vegetation index sensor |
| CN102829739A (en) * | 2012-08-21 | 2012-12-19 | 北京农业信息技术研究中心 | Object-oriented remote sensing inversion method of leaf area index of crop |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN107067433A (en) * | 2017-04-24 | 2017-08-18 | 电子科技大学 | A kind of leaf area index ground survey method based on digital image processing techniques |
| CN107067433B (en) * | 2017-04-24 | 2019-09-24 | 电子科技大学 | A kind of leaf area index ground survey method based on digital image processing techniques |
| CN109373937A (en) * | 2018-12-10 | 2019-02-22 | 中国气象局兰州干旱气象研究所 | Vegetation canopy leaf area index measurement method |
| CN110702166A (en) * | 2019-09-29 | 2020-01-17 | 北京农业信息技术研究中心 | Device for measuring plant canopy parameters |
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Application publication date: 20130501 |