CN100510617C - Method for measuring forest gap area - Google Patents

Abstract

The invention relates to forestry science and ecology, in particular to a method for measuring the forest gap area, that is, the area between two adjacent sides from the center of the forest gap to the boundary of forest gap canopy along multiple equipartition compass directions is considered as an elliptic sector, and the forest gap area is estimated with the area sum of the elliptic sectors, which is called Equiangular Elliptic Sectors (EESs), wherein, the area of the elliptic sector is calculated as follows: firstly, determining the elliptic parameters, and calculating the specific ellipse polar equation of the area intermediate value of the elliptic sector with the standard ellipse polar equation; then calculating the elliptic sector area through integral computation of the area intermediate value of the elliptic sector. The invention has the advantages of easy operation and ability of improving the area estimation precision of the forest gap.

Description

A kind of method of measuring forest gap area

Technical field

The present invention relates to forestry with ecological, specifically a kind of method that is used for measuring forest gap area.

Background technology

Since nineteen forty-seven Watt proposes woods window (forest gap) notion, many correlative studys have been carried out abroad, it is one of focus of paying close attention to that its middle forest window upgrades, and forest cycle (forest recycle) theory that is updated to the basis with the woods window is also accepted by more scholar gradually.The formation of woods window has changed resource (light, temperature, water, the soil nutrient etc.) validity in the woods window, and causes the distribution of resource inequality; The intensity of this variation mainly is subjected to factor affecting such as woods window feature, aspect and landform.Woods window feature mainly comprises the height of forest gap area, shape, zenith angle (gap aperture) and woods window edge wood, wherein forest gap area is a woods window most important characteristic, mainly contain two kinds of definition: crown canopy woods window (canopy gap) and expansion woods window (expanded gap), the former is defined as woods window edge wood canopy vertical projection area, and the latter is defined as the diameter of a cross-section of a tree trunk 1.3 meters above the ground greater than the dried area that is surrounded of the woods window edge ebon of 20cm.Forest gap area is often used as the indirect index of the interior luminous environment of reflection woods window and other resource availability, also is the foundation of calculating forest cycle speed (forest recycle rate), and the former accuracy directly influences the latter's estimation result.Therefore, measuring forest gap area rapidly and accurately is the focus that ecologists pay close attention to.The method of measuring forest gap area at present is more, here introduce 3 kinds: (1) elliptic method (Ellipse Method), the woods window is approximated to ellipse, measures major axis on major axis of woods window and the perpendicular direction and be used as oval long and short axle respectively and estimate forest gap area; (2) (Equiangular Octagon Method EOM), measures the distance that woods window center to 8 is divided equally compass heading to isogonism 8 limit shape methods, the woods window is approximated to the isogonism octagon estimates its area; (3) (Equiangular Sixteen-gon Method ESM), measures the distance of woods window center to 16 compass heading to isogonism 16 limit shape methods, the woods window is approximated to isogonism ten hexagons estimates its area.Preceding two kinds of methods are used more, and elliptic method is the simplest, uses more, but low precision, especially when woods window shape complexity, its error is bigger.Isogonism 16 limit shape methods are developed by isogonism 8 limit shape methods, and the woods window is refined into more parts, and therefore, degree of accuracy is better than the former, but more consuming time, with these class methods can be referred to as the equiangular polygon method (Siogon Methods, SMs).There are some researches show that isogonism 8 limit shape methods and isogonism 16 limit shape methods all can underestimate the area of woods window; How to find promptly accurate easy-operating again method just to become the key of this research aspect.

Summary of the invention

The object of the present invention is to provide a kind of method of accurate and easy-operating measurement forest gap area.

To achieve these goals, technical scheme of the present invention is: regarding an elliptic sector from the woods window center as along a plurality of compass heading adjacent areas between the two to the distance at woods window crown canopy edge of dividing equally, (be called isogonism elliptic sector method with these elliptic sector area sum estimation forest gap areas, Equiangular Elliptic Sectors, EESs).The calculation procedure of elliptic sector area wherein: at first determine elliptic parameter, utilize the standard ellipse polar equation to draw the concrete oval polar equation of elliptic sector area intermediate value, again elliptic sector area intermediate value is carried out the elliptic sector area that integral and calculating draws the woods window;

The calculating of wherein said elliptic sector area, concrete parameter is: set l _iAnd l _I+1Be from woods window center point to the crown canopy edge two adjacent distances, set l _iAnd l _I+1Be from woods window center point to the crown canopy edge two adjacent distances, l _iAnd l _I+1In big value be set at oval major semi-axis a _i, little value is set at the last oval camber line radius R of this ellipse _i, adopt formula standard ellipse polar equation (1), according to major semi-axis a _iAnd radius R _iTry to achieve oval minor semi-axis b _i, determine respectively with major semi-axis a _i, minor semi-axis b _iFor the concrete oval polar equation formula (3) of parameter, can try to achieve this elliptic sector area A according to formula (4) integration again _i

${\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="C200610134136E00121.png"\; state="\{\{state\}\}">r</figure-callout>}}^2=\frac{{\mathrm{<figure-callout\; id="2"\; label="a"\; filenames="C200610134136E00121.png"\; state="\{\{state\}\}">a</figure-callout>}}^2\&CenterDot;b^2}{{\mathrm{<figure-callout\; id="2"\; label="a"\; filenames="C200610134136E00121.png"\; state="\{\{state\}\}">a</figure-callout>}}^2\&CenterDot;{\sin }^2\left(\mathrm{\&theta;}\right)+{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="C200610134136E00121.png"\; state="\{\{state\}\}">b</figure-callout>}}^2\&CenterDot;{\cos }^2\left(\mathrm{\&theta;}\right)}---\left(1\right)$

$b_i=\frac{a_i\&CenterDot;R_i\&CenterDot;\sin \left(\mathrm{\&gamma;}\right)}{\sqrt{a_i^2-R_i^2\&CenterDot;{\cos }^2\left(\mathrm{\&gamma;}\right)}}---\left(2\right)$

${r_i}^2=\frac{{a_i}^2\&CenterDot;{b_i}^2}{{a_i}^2\&CenterDot;{\sin }^2\left(\mathrm{\&theta;}\right)+{b_i}^2\&CenterDot;{\cos }^2\left(\mathrm{\&theta;}\right)}---\left(3\right)$

$A_i={\&Integral;}_0^{\mathrm{\&gamma;}}0.5{r_i}^2\&CenterDot;\mathrm{d\&theta;}---\left(4\right)$

The calculating middle forest window center measurement point of elliptic sector area definite as follows: utilize the fish-eye digital camera of assembling, it is vertically domatic to remain fish eye lens, the gauger adjusts the position of fish eye lens in the woods window, when the central point of woods window appears at digital camera LCDs central, this some note is made o ", move down a segment distance to woods window center measurement point along aspect; Described to move down a segment distance along aspect be Hsin (α), and wherein H is the height of tree of woods window edge wood, and α is the angle of gradient.

In addition, when angle of gradient α was 0, o " was a woods window center measurement point.

The present invention has following advantage:

1. propose more accurately to determine the method for woods window center point first.

2. improved forest gap area estimation precision.

3. relate to integral Calculation in the method, (Matlab) writes handling procedure by data processing software, improved the practicality of method.

Description of drawings

Fig. 1 is for determining woods window center point synoptic diagram (o ' be woods window canopy central point, o ' o " vertically domatic; that o is the vertical projection point of an o ' on surface level; H is the height of tree of woods window edge wood; α is the angle of gradient, therefore, angle ∠ oo ' o "=α, line segment oo '=H can infer line segment oo " equal Hsin (α)).

Fig. 2 determines that for elliptic sector (the O point is a measurement point to synoptic diagram, l _iAnd l _I+1Be two adjacent distances (supposition l _I+1L _i), l _I+1Set oval major semi-axis, l _iBeing set on this ellipse with the major semi-axis angle is the oval radius of curvature of γ, and b is oval minor semi-axis).

Fig. 3 is that (profile of woods window is got by the all-sky photo binaryzation of actual measurement wildwood window, and the part of solid line or dotted line is represented isogonism 8 limit shape methods and the measured area of isogonism elliptic sector 8 point-scores respectively for equiangular polygon method and isogonism elliptic sector method synoptic diagram; 8 compass headings are respectively N, NE45, and E ..., WN45).

Fig. 4 is an one embodiment of the invention handling procedure particular flow sheet.

Embodiment

(1) sample plot clicks and takes from certain forest ecology experiment centre (41 ° of 51.102 ' N, 124 ° 54.543 ' E), height above sea level 252～1116m.Weather belongs to the continental monsoon climate in warm temperate zone, winter very long cold, summer is burning hot and rainy.3.9～5.4 ℃ of average temperatures of the whole year, 36.5 ℃ of the extreme highest temperatures, minimum subzero 37.6 ℃.Greater than 2497.5～2943.0 ℃ of 10 ℃ year active accumulated temperatures, frostless season 120～139d, annual 2433h at sunshine, annual precipitation 700～850mm, rainfall concentrates on for 6～August.Vegetation is under the jurisdiction of the Changbai Mountain fauna, based on Natural Secondary Forests, constructive species has Fraxinus rhynchophylla (Fraxinus rhynchophylla), Mongolian oak (Quercus mongolica), look wood maple (Acer mono), juglans mandshurica (Juglansmandshurica) etc., and part larix olgensis (Larix olgensis) artificial forest and Korean pine (Pinuskoraiensis) artificial forest are arranged, also have the remaining neutral red pine forest of small size.

(2) field survey: the artificial forest window that varies in size and 11 wildwood windows of selecting be provided with 10 winters in 2004 are the respondent, settle forestry compass at each woods window center point, measurement is along 16 compass headings (0,22.5,45, ..., 337.5 degree) be parallel to domatic distance and angle to crown canopy edge-perpendicular subpoint.All the time operate box compass by same people in the measuring process, same people judges woods window edge wood crown canopy marginal point, thereby reduces personal error.

(3) calculating of forest gap area:

Being parallel to domatic distance transform is horizontal range, and note is done: l ₁, l ₂..., l ₁₆, l ₁Compass heading be 0 degree, the position angle of other l increases successively with 22.5 degree, to l ₁₆Compass heading is 337.5 degree.

(1) equiangular polygon method (according to example):

The computing formula of equiangular polygon method is specially:

$A=0.5\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{l}_{i+1}\&CenterDot;l_i\&CenterDot;\sin (2\mathrm{\&pi;}/n)---\left(1\right)$

When i=n, l _I+1Equal l ₁N equals 16,8 or at 4 o'clock, and A is respectively the forest gap area that isogonism 16,8 or 4 limit shape methods are calculated.In this enforcement, measured the distance of 16 compass headings altogether, therefore, isogonism 8 limit shape methods have two kinds of situations of asking forest gap area, and they are respectively (l based on 2 groups of different pieces of informations ₁, l ₃..., l ₁₅) and (l ₂, l ₄..., l ₁₆); Similarly, (EquiangularQuadrangle Method EQM) has four kinds of situations of asking forest gap area to isogonism 4 limit shape methods.

(2) isogonism elliptic sector method:

To put adjacent 2 the distance (l in crown canopy edge from the woods window center _iAnd l _I+1) in be set at oval major semi-axis a than the elder _i, it is the oval camber line radius R of γ that the shorter one is set on this ellipse with the major semi-axis angle _i, determine the elliptic sector area A _iThe computing formula derivation of elliptic sector area is as follows:

${\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="C200610134136E00121.png"\; state="\{\{state\}\}">r</figure-callout>}}^2=\frac{{\mathrm{<figure-callout\; id="2"\; label="a"\; filenames="C200610134136E00121.png"\; state="\{\{state\}\}">a</figure-callout>}}^2\&CenterDot;b^2}{{\mathrm{<figure-callout\; id="2"\; label="a"\; filenames="C200610134136E00121.png"\; state="\{\{state\}\}">a</figure-callout>}}^2\&CenterDot;{\sin }^2\left(\mathrm{\&theta;}\right)+{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="C200610134136E00121.png"\; state="\{\{state\}\}">b</figure-callout>}}^2\&CenterDot;{\cos }^2\left(\mathrm{\&theta;}\right)}---\left(2\right)$

$b_i=\frac{a_i\&CenterDot;R_i\&CenterDot;\sin \left(\mathrm{\&gamma;}\right)}{\sqrt{a_i^2-R_i^2\&CenterDot;{\cos }^2\left(\mathrm{\&gamma;}\right)}}---\left(3\right)$

${r_i}^2=\frac{{a_i}^2\&CenterDot;{b_i}^2}{{a_i}^2\&CenterDot;{\sin }^2\left(\mathrm{\&theta;}\right)+{b_i}^2\&CenterDot;{\cos }^2\left(\mathrm{\&theta;}\right)}---\left(4\right)$

$A_i={\&Integral;}_0^{\mathrm{\&gamma;}}0.5{r_i}^2\&CenterDot;\mathrm{d\&theta;}---\left(5\right)$

Formula (2) is the standard ellipse polar equation, according to formula (2) and a _iAnd R _iCan try to achieve oval minor semi-axis b _i, therefore, can determine respectively with a _iAnd b _iBe the concrete oval polar equation (formula 4) of long and short semiaxis, can try to achieve the area of this elliptic sector according to formula (5).Be divided into 16 or 8 parts as the fruit-bearing forest window, the present invention is referred to as isogonism elliptic sector 16 point-scores (16-Equiangular Elliptic Sector to these two kinds of split plot designs respectively, 16EES) and isogonism elliptic sector 8 point-scores (8-Equiangular Elliptic Sector, 8EES).In this enforcement, measured the distance of 16 compass headings altogether, therefore, isogonism elliptic sector 8 point-scores have two kinds of situations of asking forest gap area, and they are respectively (l based on 2 groups of different pieces of informations ₁, l ₃..., l ₁₅) and (l ₂, l ₄..., l ₁₆).

(4) result and analysis:

Calculate the area (A of isogonism 16 limit shape methods respectively _ESM), the area and the average (A thereof of two isogonism 8 limit shape methods _{EOM_1}, A _{EOM_2}, A _{EOM_m}), the average (A of four isogonism 4 limit shape method areas _{EQM_m}), the area (A of isogonism elliptic sector 16 point-scores _16EES), the area (A of two isogonism elliptic sector 8 point-scores _{8EES_1}, A _{8EES_2}).Because isogonism elliptic sector method relates to integral Calculation, therefore, adopt data processing software Matlab (v7.2) (prior art) to finish integral Calculation, and write the handler file of Matlab.(SPSS, v13.0) (prior art) is with the difference between more above-mentioned each method of paired t-test (paired t-test) by expert data statistical analysis software Statistical Product and ServiceSolutions.The calculated in various ways forest gap area the results are shown in table 1, paired t-test the results are shown in Table 2.

As shown in Figure 4, described handling procedure idiographic flow (is example with elliptic sector 8 point-scores) is: at first read in from the woods window center along 8 distance (l that divide equally compass heading to woods window crown canopy edge ₁, l ₂..., l ₈) data, whether the judgment data form is correct, and incorrect then reporting an error and terminator correctly then enters next step; Judge whether l _iGreater than l _I+1, correct a then _i=l _i, R _i=l _I+1, circulate 8 times; With oval major semi-axis ai and oval camber line radius R _iSubstitution standard ellipse polar equation is asked oval minor semi-axis b _iAccording to oval major semi-axis a _iWith minor semi-axis b _iDetermine concrete oval polar equation r _iAccording to concrete oval polar equation, utilize the Matlab integral function semiaxis a that rectificates _iWith radius of curvature R _iBetween the elliptic sector area A _i, circulate and ask the elliptic sector area A 8 times _iAnd, last assignment is given forest gap area A.

The forest gap area that table 1. the whole bag of tricks is calculated

The paired t-test result of table 2. forest gap area

Annotate: as p 0.05 the time, show as no significant difference between two data; When p＜0.05, show as significant difference between two data; When p＜0.01, show as utmost point significant difference between two data.

Paired t-test is the result show, there is utmost point significant difference (p＜0.001) in the result of three kinds of polygon methods (isogonism 16 limit shape methods, isogonism 8 limit shape methods, isogonism 4 limit shape methods), the forest gap area that isogonism 16 limit shape methods are determined is respectively than isogonism 8 limit shape methods and isogonism 4 limit shape methods high 10.96% and 61.66%, and isogonism 8 limit shape methods are higher by 45.68% than isogonism 4 limit shape methods.Also there is utmost point significant difference (p＜0.01) between two isogonism 8 limit shape methods.

There is utmost point significant difference (p＜0.001) in the result of isogonism elliptic sector 16 point-score gained forest gap areas and isogonism 16 limit shape methods, also there is significant difference (p=0.0132,0.0005) in the forest gap area of two corresponding isogonism 8 limit shape method gained with it of isogonism elliptic sector 8 point-scores.Forest gap area (the A that isogonism elliptic sector 16 point-scores are determined _16EES) than the area (A of isogonism 16 limit shape methods _ESM) area (A of high 10.16%, two isogonism elliptic sector 8 point-score _{8EES_1}, A _{8EES_2}) than the area (A of its corresponding isogonism 8 limit shape methods _{EOM_1}, A _{EoM_2}) difference high 15.84% and 34.78%.

Forest gap area (the A of isogonism elliptic sector 16 point-score gained _16EES) with the result (A of two isogonism elliptic sector 8 point-scores _{8EES_1}, A _{8EES_2}) no significant difference, the forest gap area of isogonism elliptic sector 16 point-scores is than two isogonism elliptic sector 8 point-scores slightly little (1.17%, 2.74%); Result between two isogonism elliptic sector 8 point-scores does not have significant difference yet.

Isogonism 8 limit shape methods are to measure one of forest gap area method commonly used.Green points out that the forest gap area of isogonism 8 limit shape method estimations is littler by 10～20% than isogonism 16 limit shape methods.Result of study of the present invention is supported this conclusion: isogonism 16 limit shape methods are bigger by 10.96% than the average of two isogonisms, 8 limit shape methods.Isogonism 16 limit shape methods are divided the woods window carefullyyer than isogonism 8 limit shape methods, so estimated value is more near true value.Even so, but isogonism 16 limit shape methods are more consuming time, so isogonism 8 limit shape methods still are used widely at present.In addition, the present invention has calculated the value of isogonism 4 limit shape methods, and its result is little more a lot of than isogonism 8 limit shape methods and isogonism 16 limit shape methods, is respectively 31.36% and 38.14%, so also there is not human to cross this method.From the result of three kinds of equiangular polygon methods as can be known: along with the increase of limit number, measured area result is also increasing, and the result of deducibility isogonism 16 limit shape methods is littler than true value thus.Existing isogonism 8 limit shape methods and the isogonism 16 limit shape methods of studies show that all can be underestimated the area of woods window.

When investigating, the wildwood window finds that the woods window shape more is similar to the figure of being made up of a plurality of elliptic sectors, rather than polygon.Therefore the present invention proposes that the woods window is divided into a plurality of elliptic sectors and measures forest gap area, is referred to as isogonism elliptic sector method.Isogonism elliptic sector method shows with the comparative result of equiangular polygon method: the measured forest gap area of isogonism elliptic sector 16 point-scores and two isogonism elliptic sector 8 point-scores is bigger than its corresponding equiangular polygon method, is respectively 10.16%, 15.84% and 34.78%.Fig. 3 reflects isogonism elliptic sector method may be more accurate than polygon method.Deducibility isogonism elliptic sector 16 point-scores of the present invention are more accurate than isogonism 8 limit shape methods comparatively commonly used at present at least, because these two kinds of methods are respectively than isogonism 16 limit shape methods big 10.16% and little by 10.96%, the result who is isogonism 16 limit shape methods is positioned between the two, and isogonism 16 limit shape methods in known road are also little than woods window true value, thus isogonism elliptic sector 16 point-scores than isogonism 8 limit shape methods more near true value.In addition, the t assay shows: the result of isogonism elliptic sector 8 point-scores and isogonism elliptic sector 16 point-scores does not have difference, thereby deducibility isogonism elliptic sector 8 point-scores are more accurate than isogonism 8 limit shape methods.The field trial of isogonism elliptic sector 8 point-scores and isogonism 8 limit shape methods is measured identical, is the computation process difference, and there is utmost point significant difference in the forest gap area that both estimated.In addition, do not have significant difference between the result of two isogonism elliptic sector 8 point-scores, difference only is-2.63 ± 9.22; And utmost point significant difference (p＜0.01) is arranged between the result of two isogonism 8 limit shape methods, and difference is up to 17.66 ± 5.5, and this result who shows isogonism elliptic sector 8 point-scores of the present invention is more stable.

Generally speaking, isogonism elliptic sector 8 point-scores are more accurate, more stable than the isogonism 8 limit shape methods of measurement forest gap area commonly used at present, and field trial is measured identical.

The forest gap area that calculated in various ways obtains is referring to table 3.

Table 3: the forest gap area (m that calculated in various ways obtains ²)

Claims (4)

1. method of measuring forest gap area, it is characterized in that: regarding an elliptic sector as along a plurality of compass heading adjacent areas between the two to the distance at woods window crown canopy edge of dividing equally, with these elliptic sector area sums estimation forest gap areas from the woods window center; The calculation procedure of elliptic sector area wherein: at first determine elliptic parameter, try to achieve the concrete oval polar equation of elliptic sector area intermediate value in the polar equation of substitution standard ellipse then, again elliptic sector area intermediate value is carried out the elliptic sector area that integral and calculating draws the woods window.

2. according to the method for the described measurement forest gap area of claim 1, it is characterized in that: the calculating of described elliptic sector area is specially: set l _iAnd l _I+1Be from woods window center point to the crown canopy edge two adjacent distances, l _iAnd l _I+1In big value be set at oval major semi-axis a _i, little value is set at the last oval camber line radius R of this ellipse _i, adopt the standard ellipse polar equation, according to described major semi-axis a _iAnd radius R _iTry to achieve oval minor semi-axis b _i, adopt major semi-axis a respectively _i, minor semi-axis b _iBring into and try to achieve concrete oval polar equation r in the standard ellipse polar equation _i ², again elliptic sector area intermediate value is carried out integration and tries to achieve major semi-axis a _iAnd radius R _iBetween the elliptic sector area A _iWherein:

Concrete oval polar equation is:

$r_i^2=\frac{{a_i}^2\&CenterDot;{b_i}^2}{{a_i}^2\&CenterDot;{\sin }^2\left(\mathrm{\&theta;}\right)+{b_i}^2\&CenterDot;{\cos }^2\left(\mathrm{\&theta;}\right)}$

Minor semi-axis b in the formula _iFor:

$b_i=\frac{a_i\&CenterDot;R_i\&CenterDot;\sin \left(\mathrm{\&gamma;}\right)}{\sqrt{{a_i}^2-{R_i}^2\&CenterDot;{\cos }^2\left(\mathrm{\&gamma;}\right)}}$

Wherein: γ is the oval radius of curvature R of going up _iWith major semi-axis a _iAngle;

The elliptic sector area A _iIntegral formula be:

$A_i={\&Integral;}_0^{\mathrm{\&gamma;}}0.5r_i^2\&CenterDot;\mathrm{d\&theta;}.$

3. according to the method for the described measurement forest gap area of claim 1, it is characterized in that: the calculating middle forest window center measurement point of elliptic sector area definite as follows: utilize the fish-eye digital camera of assembling, it is vertically domatic to remain fish eye lens, the gauger adjusts the position of fish eye lens in the woods window, when the central point of woods window appears at digital camera LCDs central, this some note is made o ", move down a segment distance to woods window center measurement point along aspect; Described to move down a segment distance along aspect be Hsin (α), and wherein H is the height of tree of woods window edge wood, and α is the angle of gradient.

4. according to the method for the described measurement forest gap area of claim 3, it is characterized in that: when angle of gradient α was 0, o " was a woods window center measurement point.

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