A Study on Nature Reserve Geographic Information System in Xishuangbanna
3. Method
The framework includes the establishment of the geographic information database, the evaluation of the characteristics of natural resources and environment, and the regional plan and design or the sustainable development for the natural resources management and local village's socio-economy.
3.1 The establishment of geographic information database.
Before the geographic information system is set up, a realizable system design and analysis has been completed with the consultation of the World Wide Found for Nature's experts, the ESRI's experts, the Xishuangbanna Nature Reserve Management Bureau's officer and the some local villagers. The special database dictionary was compiled in 1994 at Redland, California, USA. Due to the natural resources surrounded by the complicate natural and social environment, the database includes twelve layers topography, hydrography, forest vegetation, traffic net, administrate boundary, soil, humid, precipitation, temperature, slop, aspect, landuse, village situation including population, nationality, income, education health, cultivated model and so on. Among them, the topography is transferred to Digital Elevation Model and the aspect and the slope can be derived from DEM. The scale of main layers is 1:50,000. The entire database has been completed in the three years by using ARC/INFO version 7.02
Because of the scare of the special forest data, at the same time, considering the significance of vegetation, obtaining vegetation and landuse data including the dynamic changes is the core object. The vegetation and landuse data mainly come from the interpretation on the panchromatic aerophotos with the scale of 1:20,000 taken in March 1989, and 28-May 1992 respectively, Spot XS data recorded on 16-Feb. 1988, etc. After image processing such as contract enhancement and synthesis, considering the TM234 susceptibility to vegetation type and partly eliminating hill shadows, we classify it by means of Maximum Likelihood. Meanwhile, the rules of the ecological law and the vertical distribution are also applied for the classification. Finally, we get 11 types such as forest, bamboo, tea, rubber woods, shrub, meadow, farmland and so on with 79% precision at the reliability 95%.
3.2. The evaluation of the characteristics of natural resources and environment.
Based on spatial database, we stared to quantitatively assess the characteristics of environment and sources in the nature reserves step by step. The content of assessment is very wide. In this paper, two typical application are reviewed.
Soil erosion is the crucial factor to influence the reforestory and the form of agriculture in tropics. Red soil, the main soil type distributed in natural resources, is not suited for intensive agriculture, even though it is supported under natural conditions of a rich and diverse plant cover. The steep and mountainous lands even accentuate these problems, as clearcutting on hillsides lead to erosion. Soil is too precious to let it be eroded away without trying to hold it in place. GIS can play a major role in the curtailment of erosion.
Two series of soil erosion have been developed. One is used for villages' erosion hazard; the other is for entire nature reserve's risk of soil loss. Both are being derived from the Universal Soil Loss Equation, in order to keep consistency.
Soil loss by water erosion can be expressed by the empirical equation (Wischmeier and Smith, 1978):
A= R*K*L*S*C*P
where A= computed soil loss per unit area, expressed in the units selected for K and for the period selected for R;
R = rainfall and runoff factor (N/hr);
K = soil erodibility factor (kg hr/N m
2)
L = slope-length factor;
S = slope-steepness factor;
C = cover and management facor;
and P = support practice factor.
Because of the limited data that were available, R and K have been estimated by the approximate method proposed by Arnoldus (1980) and K. Romkens et. al (1988), respectively. Topographic factor L and S can be derived from the DEM. C is the ratio of soil loss from the cropped land under specified conditions to the corresponding loss from clean-tilled, bare land. Cropland including paddy, dry land, fallow, tea, rubber tree, brushes, grass, bamboo, forest including rain forest, mountain rain forest, monsoon forest, evergreen broadleaf forest etc. have been estimated by field sampling and approximate method proposed by Wischemeier & Smiths. In view of the only support practice in Xishuangbanna planting rubber and tea on the contour, P varies between 0.6 and 0.9 according to the gradient of the slope. The beginning of rainy reason i.e. May and the mean level of year have been computed, respectively. The maximum and the mean of the soil erosion of May are 329.295 t/ha, 1.595 t/ha with the Standard Deviation of 9.093 respectively. The maximum and the mean of every year are 3140.85t/ha, 15.210t/ha a with the SD of 86.712. The whole reserve has been divided into 4 erosion classes according to erosion hazard for year.
The Asian Elephant habitat is obtained by means of field sampling and Multivariate Regression. In field survey, elephant trails and relevant ecological factor, biological factor and human activity have been marked. The final results can be gotten by the following formula:
Y= b0+b1X1+b2X2+b3X3
+b4X4+b5X5+b6X6
+b7X7+b8X8
Where, Y = the frequency of elephants activity (unit is trails per ha);
b0,b1,b2,b3,b4,b5,b6,b7,b8 are regression coefficients;
and X
1,X
2,X
3,X
4,X
5,X
6,X
7,X
8,X
9
represent correlative factors, i.e. vegetation, crown density, distance from water, slope, aspect, location, elevation and human activity. These can be obtained from spatial database. And the precision is obtained at 82% under the reliability of 95%.
3.3 The regional plan for natural resources management and local village socio-economy.
Based on the database and environment assessment, according to the practical needs, the detail plan and design have been applied. Two priorities have been considered, i.e. wildfire hazard and agroforestry.
According to the historic record in nature reserves such as to location, area, intensity and so on, we find that the main forest fire risk comes from the slash and burn by local villagers, and the intensity results from the inflammability of woods an dryness. So the distance form road and villages, the aspect and the inflammability of vegetation and so on which are deduced from database are clustered after they have been quantitatively normalized. A reliable classification with five wildfire hazards has been plotted. It is easy to plot the patrol lines and the fire break for the Nature Reserve Management Bureau.
There is an urgent need to apply improved agroforestry systems and ecological villages fro China's deteriorating farmlands where fertility loss exceeds crop yields. It is particularly urgent for the watersheds of the Lancang Jiang(Mekong River) in Xishuangbanna where the Farming of slash and burn is practiced on a diminishing suitable landbase.
There is an urgent need to apply improved agroforestry systems and ecological villages for China's deteriorating farmlands where fertility loss exceeds crop yields. It is particularly urgent for the watersheds of the Lancang jiang(Mekong River) in Xishuangbanna where the farming of slash and burn is practiced on a diminishing suitable landbase.
A great quantity of villages are situated around or in the nature reserves. In order to prevent people from cutting woods, hunting wildlife, destroying the nature reserves, the aims of agroforestry and ecological villages include improving the forest coverage around ecological villages, increasing the villager's incomes only in limited lands, and finally raising the fertility of soils. At the same time, some sketches have been finished to move villages out of he core zone of nature reserves. The villager's GIS for agroforestry has been implemented in Zhongtianba and Bajiazhai with the scale of 5,000. Zhongtianba ecological village has been built under the support of WWF. By means of planting nitrogen fixed woods, herb and comprehensive management, the villagers improve the incomes. Meanwhile, environment is protected.
