CN106767561A - A kind of method that utilization terrestrial optical instrument estimates canopy leaf area index indirectly - Google Patents
A kind of method that utilization terrestrial optical instrument estimates canopy leaf area index indirectly Download PDFInfo
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- CN106767561A CN106767561A CN201611156786.1A CN201611156786A CN106767561A CN 106767561 A CN106767561 A CN 106767561A CN 201611156786 A CN201611156786 A CN 201611156786A CN 106767561 A CN106767561 A CN 106767561A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/28—Measuring arrangements characterised by the use of optical techniques for measuring areas
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- G—PHYSICS
- G16—INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR SPECIFIC APPLICATION FIELDS
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Abstract
The present invention discloses a kind of method that utilization terrestrial optical instrument estimates canopy leaf area index indirectly, and step is：First, effective leaf area index L is estimated using hemisphere photographic instrumente；2nd, the Leave gathering degree index Ω on sunray direction is estimated using TRAC instrumentsE(θs)；3rd, by the Leave gathering degree index Ω on sunray directionE(θs) it is corrected to Leave gathering degree index Ω when solar zenith angle is 0 °E(0)；4th, according to effective leaf area index LeWith the Leave gathering degree index Ω in vertical directionE(0) canopy leaf area index LAI is calculated.The present invention relates to a kind of Crown canopy parametre method of estimation, the method for referring in particular to estimate canopy leaf area index jointly using hemisphere photographic instrument and TRAC instruments.The present invention can avoid leaf area index during due to Instrument observation caused by the change of solar zenith angle from being underestimated problem, i.e., the accurate leaf area index estimated in vertical direction.More accurate leaf area index estimate can be obtained in terms of forest inventory control, Forestry Investigation and scientific research using this method.
Description
【Technical field】
The present invention relates to a kind of ground method of estimation of canopy leaf area index, refer in particular to utilize optical instrument on the ground
The size and number of hole between observation blade, and then the method for estimating the unit level ground blade gross area.It is of the invention main
Solve under different time or site condition, because the different caused leaf area index of solar zenith angle are underestimated problem.
【Background technology】
Leaf area index is the fundamental physical quantity for representing canopy leaves quantity, is also top vegetation biochemical process, plants
By the key input parameter of the research fields such as effectively photosynthetic absorption and Global Carbon water circulation faults.Jingming Chen and
Leaf area index definition was the half of all blade optical cross section products on unit ground in 1992 by Black, T.A..
Compared with all blade areas in actually measurement canopy, using optical instrument in the big of ground observation canopy hole
Small and quantity, and then estimate that the benefit of canopy leaf area index is that speed is fast, saves substantial amounts of man power and material.At present, ground
Up to tens kinds of leaf area index optical observation instrument, wherein the optical instrument based on hemisphere photographic process is more commonly used, it is representative
Instrument has WinSCANOPY (production of Quebec, CAN Regent instrument companies), HemiView (Britain Camb Delta-T equipment
Company produces) and LAI-2000 (production of Nebraska,USA Li-Cor companies).Hemisphere photographic process inverting leaf area index is
According to the blade volume density (m that Miller set up in 19672/m3) formula and design, the method is it is not intended that blade is true
Bunching effect in canopy, thus only by hemisphere photographic process observation can not inverting obtain real leaf area index
(LAI) effective leaf area index (L of the blade in space under the conditions of random distribution, is assumed thate).Therefore, Jingming
Chen proposes the method for description Leave gathering degree in nineteen ninety-five, and devises the Leave gathering degree on sunray direction and refer to
Number (ΩE(θs)), while having invented optical instrument TRAC (the Canadian Ottawa Third- matched with concentration class exponentiation algorithm
Wave mechanical ＆ electrical corporations produce).In conventional practical application, the method for calculating leaf area index is LAI=Le/ΩE(θs)。
However, that obtained by TRAC Instrument observation data inversions is sunray direction θsOn concentration class index, with
The increase concentration class index of solar zenith angle can typically increase, and effective leaf area index expression is that hemisphere photographic instrument is hanging down
The Nogata blade quantity that (zenith angle is 0 °) obtains upwards, therefore, the true value calculating method of leaf area index should be LAI=
Le/ΩE(0).As used Ω in computing formulaE(θs) rather than ΩE(0) leaf area index can be caused to be underestimated.Do not have still at present
There is theoretical method to correct this error.The present invention proposes one using hemisphere photographic instrument and the observation data of TRAC instruments
Plant the theoretical method for calculating leaf area index actual value, it is to avoid to the shadow of calculating leaf area index under the conditions of different solar zenith angles
Ring.
【The content of the invention】
The concentration class index Ω for obtaining is calculated by the observation data of TRAC instrumentsE(θs) sunray direction can only be expressed
On Leave gathering, when combining TRAC instruments and hemisphere photographic instrument and estimating leaf area index, in order to solve solar zenith angle
For caused by 0 ° leaf area index underestimated problem, the present invention proposes a kind of new leaf area index method of estimation.
Concrete technical scheme of the invention is：
(1) hemisphere photographic instrument observation hemisphere day void porosity, and estimate that the Efficient leaf area in vertical direction refers to accordingly
Number Le.Illustrate that hemisphere photographic instrument obtains the technical scheme of hemisphere day void porosity by taking LAI-2000 as an example, it is excellent in practical operation
Select but be not limited to LAI-2000.LAI-2000 is placed in below-canopy by operator, is seen according to the operational procedure of LAI-2000
Survey.The hemisphere sky that LAI-2000 instruments will be observed that automatically is divided into 5 rings, the zenith angular region of each ring cover by zenith angle
Respectively 0 °~13 °, 16 °~28 °, 32 °~43 °, 47 °~58 ° and 61 °~74 °.This 5 porositys of ring are counted respectively, and
L is estimated according to the algorithm that Miller set up in 1967e。
Wherein,Wi=cos (θi)·sin(θi)·d(θi)。θiIt is i-th center zenith angle of ring,It is average value that each ring statistics obtains porosity, if carry out n using hemisphere photographic means in a sample ground
Secondary observation, thenRepresent and the average value for obtaining porosity is measured n times to i-th ring.
(2) pore sizes and distribution of the using TRAC Instrument observation canopies, and the blade in sunray direction is calculated accordingly
Concentration class index ΩE(θs).Operator is observed according to the use code of TRAC instruments in below-canopy, and instrument is according to blade
The concentration class index of the automatic calculating observation moment solar direction of size and distributed data of hole, computational methods are by Jingming
Chen in nineteen ninety-five propose, i.e.,
Wherein, Pc(θs) it is in solar zenith angle θsThe true canopy porosity obtained by TRAC Instrument observations on direction (has
Leave gathering occurs).Pr(θs) it is preferable canopy porosity (the blade random distribution, nothing that algorithm calculating is carried according to TRAC instruments
Aggregation ΩE(θs) represent solar zenith angle θsLeave gathering degree on direction.
(3) is by solar zenith angle θsLeave gathering degree Ω on directionE(θs) it is corrected to leaf when solar zenith angle is 0 °
Piece concentration class ΩE(0).Generally, solar zenith angle θsThe canopy porosity comprising Leave gathering effect is expressed as on direction
Wherein, G (θs) it is solar zenith angle θsDirection blade projection function on direction.Therefore, θsBlade on direction gathers
Intensity is
Solar zenith angle is that the Leave gathering degree on 0 ° of direction is
Wherein, Pc(0) can be approximate with a minimum porosity for ring in hemisphere photographic process, for example use LAI-2000 instruments
In 0 °~13 ° of this rings porosity it is approximate.Direction blade projection function G (0) when solar zenith angle is 0 ° can be according to LeAnd Pc
(0) it is calculated
By G (0) and θs=0 substitution Wilson is set up in nineteen sixty blade mean obliquity α (plane blade normal direction and
Angle between horizontal plane) in some directions with Leaf inclination function G (θs) relation
G(θs)=cos (α) cos (θs) α+θs≤90°
G(θs)=cos (α) cos (θs)·{1+2/π·(tan(γ)-γ)} α+θs90 ° of ＞
Wherein, γ=arccos (cot (α) cot (θs)).Because α spans are between 0 °~90 °, according to above formula
Obtain α=arccos (G (0)).By known θsAbove formula is substituted into α, G (θ are obtaineds).Further obtain ΩE(0)。
(4) is according to the effective leaf area index L in vertical directioneWith the Leave gathering degree index Ω in vertical directionE(0)
Calculate canopy leaf area index
LAI=Le/ΩE(0)
The present invention is advantageous in that the leaf area index in vertical direction can be calculated.Using hemisphere observation instrument and
During the observation data of TRAC instruments calculate leaf area index, the blade face caused when solar zenith angle is not 0 ° can be solved
Product index is underestimated problem.
【Brief description of the drawings】
Fig. 1 is flow chart of the invention.
【Specific embodiment】
The present invention combines examples below and specific embodiment is described in detail with reference to the attached drawings：
This example gathers hemisphere photographic data using the LAI-2000 instruments of Nebraska,USA Li-Cor companies production.Root
According to technical scheme steps (1) Suo Shu, operator is placed on below-canopy according to the operational procedure of LAI-2000, chooses different
Position carries out n measurement.LAI-2000 will be calculated on the direction of level ground automatically according to the method described in step (1)
Effective leaf area index Le.The L for obtaining such as is observed by LAI-2000eBe worth is 3.
The TRAC instruments produced using Canadian Ottawa Third-Wave mechanical ＆ electrical corporations are gathered canopy pore size and divided
Cloth data.According to the operational procedure of TRAC, in below-canopy, hand-held TRAC's operator is expert in the plane of solar direction
It is observed during walking.TRAC in operator's walking process by hole between automatic Observation and record blade, and according to technology
The Leave gathering degree index Ω on the automatic calculating observation moment solar zenith angle direction of method described in protocol step (2)E(θs)。
The blade porosity P on solar zenith angle direction can also be automatically calculated by TRAC instruments simultaneouslyc(θs).Such as pass through TRAC instrument
The P that device observation is obtainedc(θs) it is 0.1, ΩE(θs) it is 0.6.
According to the computational methods of technical scheme steps (3)
In order to obtain ΩE(0) need to be known a priori by ΩE(θs)、G(θs)、G(0)、Pc(0)、Pc(θs) and θs.Wherein, ΩE
(θs) and Pc(θs), it is known that solar zenith angle θsCan be according to the warp residing for observation moment (GMT) and observation place
Latitude (using compass survey) is obtained, such as now solar zenith angle θsIt is 45 °, Pc(0) in a minimum ring of LAI-2000 observations
Obtained in reading, such as Pc(0) it is 0.9.According to above known quantity, the method according to technical scheme steps (3) calculates G (0) and G
(θs), now G (0) is 0.0351, G (θs) it is 0.4502.Therefore, Ω is calculatedE(0) it is 0.8284.
According to technical scheme steps (4), the true leaf area index LAI=L of canopy is calculatede/ΩE(0)=3/0.8284=
3.6214。
Claims (3)
1. a kind of method that utilization terrestrial optical instrument estimates canopy leaf area index indirectly, mainly includes the following steps that：
(1) hemisphere day void porosity is gathered using hemisphere photographic instrument, and estimates the effective leaf area index L in vertical directione；
(2) gathered using the blade on the pore size and quantity, and calculating observation moment solar direction of TRAC Instrument observation canopies
Intensity index ΩE(θs)；
(3) by the Leave gathering degree index Ω in solar directionE(θs) the Leave gathering degree that is corrected to when solar zenith angle is 0 ° refers to
Number ΩE(0)；
(4) result according to step (1) and step (3) calculates the leaf area index in horizontal direction.
2. the method that a kind of utilization terrestrial optical instrument according to claim 1 estimates canopy leaf area index indirectly, its
It is characterised by including and observing moment solar direction blade concentration class index Ω in step (3)E(θs) it is corrected to solar zenith angle
For 0 ° when Leave gathering degree index ΩE(0) method.
3. the method that a kind of utilization terrestrial optical instrument according to claim 1 estimates canopy leaf area index indirectly, its
The method for being characterised by calculating leaf area index in step (4) is LAI=Le/ΩE(0)。
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Citations (7)
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|---|---|---|---|---|
| CN101916438A (en) * | 2010-07-20 | 2010-12-15 | 浙江大学 | Method for obtaining leaf area index and average leaf inclination of rice canopy by using hemisphere photographic process |
| CN102538717A (en) * | 2010-12-30 | 2012-07-04 | 北京师范大学 | Automatic leaf area index observation system and method |
| CN104330057A (en) * | 2014-11-25 | 2015-02-04 | 东北林业大学 | Correction method for measuring leaf area index by use of hemispherical photography |
| US9207072B2 (en) * | 2010-12-02 | 2015-12-08 | Nec Corporation | Leaf area index measurement system, device, method, and program |
| CN105259179A (en) * | 2015-11-26 | 2016-01-20 | 河南中原光电测控技术有限公司 | Leaf area index instrument based on radiation measurement principle |
| JP2016131494A (en) * | 2015-01-15 | 2016-07-25 | 株式会社日立ソリューションズ | Growth management device |
| CN106124049A (en) * | 2016-06-20 | 2016-11-16 | 福州大学 | A kind of implementation method of Vegetation canopy multi-optical spectrum imaging system |
-
2016
- 2016-12-07 CN CN201611156786.1A patent/CN106767561A/en active Pending
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101916438A (en) * | 2010-07-20 | 2010-12-15 | 浙江大学 | Method for obtaining leaf area index and average leaf inclination of rice canopy by using hemisphere photographic process |
| US9207072B2 (en) * | 2010-12-02 | 2015-12-08 | Nec Corporation | Leaf area index measurement system, device, method, and program |
| CN102538717A (en) * | 2010-12-30 | 2012-07-04 | 北京师范大学 | Automatic leaf area index observation system and method |
| CN104330057A (en) * | 2014-11-25 | 2015-02-04 | 东北林业大学 | Correction method for measuring leaf area index by use of hemispherical photography |
| JP2016131494A (en) * | 2015-01-15 | 2016-07-25 | 株式会社日立ソリューションズ | Growth management device |
| CN105259179A (en) * | 2015-11-26 | 2016-01-20 | 河南中原光电测控技术有限公司 | Leaf area index instrument based on radiation measurement principle |
| CN106124049A (en) * | 2016-06-20 | 2016-11-16 | 福州大学 | A kind of implementation method of Vegetation canopy multi-optical spectrum imaging system |
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