Evaluation of Asian Elephant Habitat
In the transformation, the minimum trails of each factor under different conditions are defined as 1 1.0, and the others are proportional vested , e. g. the vegetation type (see table 2). I
Table 2.
| conditions |
trails /ha |
numerical value |
| evergreen broad-leaf forest |
1120 |
4.9 |
| bamboo forest |
1380 |
6.1 |
| shrub |
300 |
1.3 |
| dry farmland |
230 |
1.0 |
The computed coefficients are as table 3.
The precision is evaluated as following :
Lyy (the total square error of a sampling)=64889577
U (the regression sum of squares)=35931762
Q(the residual sum of squares )=28957815
F(8, 62)(the test of significance of regression equation) =9. 62
FO. 01(8,62)=2.80 F > FO. 01 R=O. 76
Table 3.
factor
vegetation
crown
water
slope
aspect
location
elevation
human activity
| coefficient bj
156.40
-196.90
101.44
142.80
157.95
12. 17
115.29
132.99
| constant bo
- 1705.03
|
The test of significance of each regression coefficient is in table 4.
Table 4.
| factor |
F |
priority |
| vegetation |
4.973 |
4 |
| crown density |
1.504 |
5 |
| water |
5.731 |
3 |
| slope |
0.800 |
6 |
| aspect |
10.519 |
2 |
| location |
0.009 |
8 |
| elevation |
0.364 |
7 |
| human activity |
12.819 |
1 |
the study, we get the precision of 82% under the reliability of 95%.
3. 2 Interpretation of the habitat
Among factors, topographic factors, i.e. slope, aspect, location, elevation and distance from water, can be directly obtained from the topographic map. The human activity intensity, e.g. density of population, can be obtained from the statistics of late villages situation. And we gain vegetation type and crown density from interpret action of images. Although vegetation only take the forth place, the first place human activity intensity, the second aspect are directly or indirectly reflected by vegetation. And we regard the vegetation as the foundation of the habitat. In the interpretation, vegetation is considered as the main object.
3.2. 1 Image processing[6]
Data available for analysis are following: the black and white panchromatic aerophotos with scale of 1: 20, 000 taken in March 1989; Landsat TM data respectively recorded on 2-Feb 1988and 28-May 1992; Spot XS data recorded on 16 Feb 1988, etc. Firstly, we carry out the image processing e. g. contrast enhancement, color synthesis. The correlation coefficient matrix of TM bands in Mengyang , illuminates that minor correlation are respectively between TM2 and TM4'TM3 and TM4, TM4 and TM7. Only considering correlation, TM346 is the best, and TM234 takes second place. But, when we take further steps to consider functions of each band, the synthesis of TM234 is prior to others, for its susceptibility to vegetation type and partly eliminating hill shadows. Secondly, we use maximum likelihood for image classification. By virtue of actual situation in Mengyang nature reserve, we set up training units of 11 types, including forest, bamboo ,tea plantation, farmland, rubber woods, meadow, shrub, water and the various tansitions , e. g. from forest to farmland, from farmland to forest, from meadow to shrub. The results possess 79% precision with the reliability of 95 %. When 11 types are composed to 6 types, the precision increases to 86 %.
3.2.2 Interpretation
The objection of interpretation training is to establish marks and to set up units for computer automatic classification. In addition, the ecological law of vegetation and the vertical vegetation distribution which are formed by difference of heat and precipitation, are also applied in the interpretation. By cartological choise, boundary lines of status quo are demarcated and transformed to topographical maps one by one to form the base maps .
3. 3 Habitat Assessment
3. 3. 1 Software and Hardware
The habitat is assessed with ARC/INFO version 7.03 on SUN SPARC LX workstation, Calcomp 9500 digitizer and Calcomp 3036 plotter.
3. 3. 2 The Database Design
Based on factors analysis and interpretation, topography, hydrology, forest vegetation, density of population, road, village and administative boundary are used as layers to establish GIS.The organization of layers sees table 5. In the design, we use the special dictionary[7]to establish Mengyang nature reserve GIS.
Table 5.
| layers |
geographic data |
attribution data |
| topography |
line |
contour |
| hydrology |
line |
river type, name |
| vegetation |
polygon |
vegetation type |
| road |
line |
road, path, trail |
| village administative |
point |
name, population ,income etc. |
| bounds |
line |
county, village, reserve etc. |
3. 3. 3 The Database Establishment
The data are generally divided into two parts, geographic data and associated attributes. To establish geographic database, we capture geographic features with Calcomp 9500 digitizer (1000lpi) .Well-distributed 17 control points in Mengyang reserve are selected to ensure the accuracy. Meanwhile, the input error of points is under 0.2mm on maps (scale 1: 50,000). The graphics are transformed and compiled to for the topology. Based on geographic database , the associated attributes such as vegetation, elevation, hydrology, road, landuse, annotion, text, etc. , are defined and inputed by users, besides the automatically produced items such as area, length , perimeter. Once the input of attributes is completed , we can identify, operate and analyse the relation between geographic data and attribution and the relation among layers .
