(College of Geography, Fujian Normal University, Fuzhou, 350007)
Based on the remote sensing image data of Jinjiang City in two periods (1988 and 200 1), combined with relevant statistical data and existing geoscience knowledge and experience, the interpretation marks were established, and the ecological environment classification system of Jinjiang City was established. Through the interpretation of the two images and the analysis of the present situation of land use in Jinjiang City, the ecological environment type maps of two different periods are obtained. Based on the analysis of the quantity, distribution characteristics and dynamic change law of ecological environment, a spatio-temporal analysis model for measuring the change of ecological environment is constructed. The results show that during the monitoring period, the urban residential areas and rural residential areas in Jinjiang City changed obviously, and the increase rate was very fast, while the ecological environment types of dry land decreased sharply during the monitoring period.
Keywords: ecological environment; Dynamic change; Spatial analysis model; Markov model; "3S" integration technology
Any natural ecological environment has a process of continuous evolution, which is gradually realized through the constant changes in the components that make up the ecological environment. On many different scales, the increasingly strong influence of human beings has led to different types of ecological environment. The change of ecological environment can affect many ecological phenomena, such as the migration of animals, the flow and erosion of surface water, the diversity of species and the diffusion or marginal effect of interference [1]. Therefore, it is of great significance to study the dynamic changes of ecological environment.
1 Overview of the study area
Jinjiang City is located in the southeast coast of Fujian Province, with the latitude of 24 30 ′ 23 ″ ~ 24 54 ′ 26 ″ and the latitude of118 24 ′16 ″ ~18 4/kloc. Jinjiang City is surrounded by mountains and seas, and its landform types are mainly plains and hilly platforms, with a total land area of 656.63km2..2002, the total population was about 65,438+0,026,5438+0,000. Since the reform and opening up, Jinjiang's social economy has developed rapidly. By 2002, the GDP reached 32810.60 billion yuan, and the per capita GDP reached 310.876 yuan, 23.97 times and 20.79 times of10.990 respectively. The rapid economic development has accelerated the urbanization process of Jinjiang, and the changes of its internal ecological environment are typical. Using "3S" technology to dynamically monitor the ecological environment in Jinjiang can help us understand the ecological environment changes caused by the economic development and urbanization development of small towns in China.
2 data and methods
Through GPS technology, spatial data can be quickly located, and RS technology can be used to provide aerial photos, satellite photos and other image data for aerospace and aviation remote sensing, so as to locate and quantify land parcels with high precision and intuitively interpret the features of ground objects and the current information of resources. Then, by using GIS spatial database technology, the ground object information obtained by GPS and RS and various information supplemented by other means are summarized into data with various attributes (such as graphics, images, statistical data and topological data reflecting the spatial correlation of entities, etc.). )
2. 1 data source and processing
Landsat TM data of Jinjiang City in two phases (1988 and 200 1) are taken as the basic data for obtaining ecological environment information, and the resolution is 30m×30m. At the same time, a large number of related charts and statistical data were collected, and the background database of the study area was established. Geometrical correction, multi-band synthesis and mosaic of TM image are carried out by using topographic map, and image enhancement is carried out to improve interpretation accuracy.
2.2 Eco-environmental classification system and image interpretation signs
According to the characteristics of eco-environment in Jinjiang, according to the differences of topography, soil, vegetation and land use, the eco-environment types in this area are divided into two categories (Table 1). According to the spectral characteristics of general features on TM images, combined with the corresponding land use type map, local biological growth characteristics and laws, as well as the existing knowledge and experience and the comparative analysis of similar features on images, the image features with the most significant inter-class differences and intra-class consistency are found, and the direct and indirect interpretation marks of various categories are established [2]. As far as Jinjiang City is concerned, the main surface is covered with water, green vegetation, residential areas, paddy fields, dry land and sandy land. Reflected in the true color digital remote sensing image synthesized by TM5, 4 and 3 bands: the water body is flaky blue or nearly black; Green vegetation, including forests, grasslands and crops with large canopy density, has a flaky or flaky green tone, and the difference between some biomass and the underlying soil background exposure is manifested in the change of tone depth; Residential areas are strewn at random with red and purple; Paddy fields are mottled or mottled with red, purple or blue tones; The sand is white.
Table 1 jinjiang eco-environmental classification system
2.3 Extraction of Ecological Environment Information
Using Arcview GIS software to interpret the two images, the smallest unit is determined according to different topography, soil, vegetation and land use types, and different ecological environment types are divided. ArcGIS is used to overlay the eco-environment types in 1988 and 200 1 to get the eco-environment change layers in two periods. Then, the area statistics, data information extraction and database establishment of various ecological environment types are carried out.
3 dynamic change analysis of ecological environment
3. 1 Spatio-temporal modeling of ecological environment evolution
Considering that the classification system of ecological environment is based on various natural elements, the spatio-temporal evolution model of ecological environment emphasizes its three-dimensional changes in time and space, so the dynamic changes of ecological environment are divided into unchanged parts, transferred parts and newly changed parts in the model [3]. From t 1 (S (i, t 1)) at the beginning of the study to t2 (S (i, t2)), the spatial pattern change of type I ecological environment can be divided into: ① Invariant part (USi), that is, the ecological environment and spatial position are consistent at the beginning and end of the study; (2) Transfer the changed part (CSI = S (I, T 1)-USI), and the type I ecological environment will be transformed into other non-type I ecological environment types; (3) Adding a new change part (NSI = S (I, T2)-USI), other non-I eco-environment types will be transformed into I eco-environment types.
In order to describe and measure the spatial process and intensity of the dynamic change of ecological environment more accurately, a spatial analysis model of the dynamic change of ecological environment in an ideal state is established:
TRSi=CSi/USi/(t2 -t 1)
IRSi=NSi/USi/(t2 -t 1)
CCSi =(CSi+NSi)/USi/(T2-t 1)= TRSi+IRSi
In the formula, TRSi is the transfer rate of Class I ecological environment type from t 1 to t2 in the monitoring period; IRSi is its new rate of change; CCSi is its total rate of change; N is the classification number of ecological environment types in this area, i∈( 1, n).
3.2 Dynamic changes of ecological environment in Jinjiang City
Fig. 1 and fig. 2 show the distribution of eco-environment types in jinjiang city in 1988 and 200 1 year. Through the superposition analysis of the two, it can be concluded that the area of Jinjiang city with unchanged ecological environment is 38 163.438+0hm2, accounting for 4 1% of the total land area of Jinjiang city. The transfer area is 27499.5hm2；; The newly-increased area is 27499.5hm2, and the two areas are equivalent, accounting for 29.5% of the total land area of Jinjiang City respectively. Table 2 is the calculation result of the ecological environment change degree in Jinjiang city from 1988 to 200 1 year according to the ecological environment spatial change analysis model. It can be seen that the change rate of platform ecological environment is the highest, and the transfer area and share are the largest, which are 5046.0hm2 and 87.9% respectively. The water ecological environment has the smallest change rate, and its transfer area and share are also the smallest, which are 104.2hm2 and 9. 1% respectively. On the contrary, the newly-increased area of artificial building ecological environment is the largest, which is 6876.7hm2.
As can be seen from Table 2, the ecological environment changes in the dry land of the platform are particularly prominent. During this monitoring period, this type of transfer area accounts for nearly half of the total transfer area of all eco-environmental types in this area, and its transfer speed is obviously faster than other types, and its transfer speed is 2.5 times of its new increase rate. The ecological environment type of platform dry land is the main source of the new increase of other ecological environment types. In the artificial building ecological environment, the increased area of urban residential ecological environment accounts for 68% of the total increased area, and if the increased area of rural residential ecological environment is added, it accounts for 99.6% of the total increased area. Therefore, during this monitoring period, almost all the transfer areas of ecological types have been transformed into new areas of this ecological environment type.
Figure 1 1988 Eco-environment Type Map of Jinjiang City
Figure 2200 1 Eco-environment Type Map of Jinjiang City
Table 2 Dynamic change rate of ecological environment in Jinjiang City (1988 ~ 200 1 year)
3.3 Spatial changes of eco-environmental types in Jinjiang City
Through the analysis of Arcview buffer zone, it is found that the urban expansion of Jinjiang presents the characteristics of radiation and diffusion along the original old city, and small towns and villages are dragged down by the urbanization process of big towns and villages and tend to be merged by them. Therefore, in Figure 1 and Figure 2, some types of urban ecological environment and rural ecological environment with abnormal development, such as longhu town, Yinglin Town and jinjing town, all present long and narrow shapes, and the changes of rural settlements around them have similar shapes, and the expansion direction of this change tends to the location of major towns or areas with relatively developed social economy, such as the extension of Dongshi Town to Anhai Town. This expansion mainly occupies agricultural land, in which the net area of ecological environment of platform dry land decreases the most. From 1988 to 200 1 year, the dry land ecological environment of * * platform decreased by 88 16.4hm2 and shifted by/kloc-0 12556.5hm2 The main destination of the transfer is the artificial building ecological environment, which transferred 7446.6hm2, accounting for 59.3% of the transferred part, of which 746.6hm2 was transferred to construction land. Through the analysis of this area change matrix, it can be concluded that the main source of the new part is the ecological environment with forest land on the platform. The new area is 3740. 1hm2, and the new growth rate is only 1%. The area of the transfer part is much larger than that of the newly added part. In addition, the ecological environment position and quality of the newly-added platform dry land are obviously not as good as that of the transferred part. However, due to the large original area of dry land ecological environment, its transfer rate and change rate are small, which are 3% and 4% respectively (Figure 3).
Fig. 3 Dynamic changes of ecological environment types in Jinjiang City (1998 ~ 200 1 year)
4 Markov process simulation and prediction of ecological environment change
4. Determination of transition probability of1Markov process
Markov process is a special random motion process, that is, every state transition is only related to the state of the previous moment, but has nothing to do with the past state, or it is a state transition process without aftereffect [4]. The change of ecological environment is divided into a series of discrete evolution states. The transformation rate from one state to another, that is, the transition probability, can be obtained from the annual average transformation rate of a certain type of ecological environment during the period of 1988 ~ 200 1 year. Its mathematical expression is:
p 1 1 p 12 p 13……p 1n
P2 1 P22 P23 …… P2n
… … … …… …
Pn 1 Pn2 Pn3 …… Pnn
In the above formula, n is the number of eco-environmental types in the study area, and Pij is the probability that I type will be transformed into J type from beginning to end. And meet the following two conditions:
Innovation of Land Information Technology and Development of Land Science and Technology: Proceedings of the 2006 Annual Conference of china land science Institution.
4.2 Trend of Eco-environmental Pattern in Jinjiang City
The transition probability is determined by the time period from1988 to 2001year (Table 3). According to the area percentage of 200 1 each ecological environment type, the initial state probability is obtained, and Markov process operation is carried out with the help of Matlab and Excel. Every 13 years is a step. When n = 1, the forecast year is 20 14 years. When n = 2, the forecast year is 2027, and so on. The prediction results are shown in Table 4.
The forecast results show that the change trend of eco-environment in Jinjiang City in the next 26 years is that the area of eco-environment types such as paddy field and dry land will decrease gradually, and the eco-environment of dry land will decrease obviously. The ecological environment of rural residential areas gradually decreases after increasing to a certain extent; The ecological environment of urban residential areas is gradually increasing, while other types are gradually decreasing, but the speed is quite slow. This change will last for a long time until it reaches a relatively stable state, which shows that the artificial building ecological environment is gradually annexing other ecological environment types, and finally forms a new ecological environment pattern of urban-rural economic integration.
Table 3 Change and Transfer Probability Matrix of Ecological Environment Types in Jinjiang City (1988 ~ 200 1) Unit:%
Table 4 Predicted value of Markov process of eco-environmental change in Jinjiang City Unit: hm2
5 conclusion
(1) The ecological environment types of Jinjiang City, such as woodland, garden, urban residential area and rural residential area, all belong to the expansion type, and their increasing speed is generally faster than the transfer speed in the same period, and the total area is increasing. Among them, during the monitoring period, the ecological environment of urban residential areas and rural residential areas increased rapidly, while the types of ecological environment such as paddy fields, dry land and forest land decreased, and the total area decreased, among which the types of ecological environment in dry land decreased sharply during the monitoring period.
(2) According to the changing characteristics of Jinjiang's ecological environment, Jinjiang's ecological environment is divided into northeast development zone, southwest development zone and central new development zone. The ecological environment changes in the Northeast and Southwest Development Zones are the most dynamic, and the expansion of construction land is the fastest. The change of ecological environment mainly radiates to the periphery of the two sides of the main traffic trunk lines (along the Yangtze River and along the road), especially the main traffic trunk lines such as Quanan Highway (Quanzhou to Anhai, Jinjiang) and century avenue (Qingyang to Luoshan), which are dumbbell-shaped, and integrate Jinjiang City and Anhai Town. The newly-born areas in central China are dominated by agricultural land, and the protection of cultivated land is relatively good, and the land use changes dramatically, and the unit space capacity is far from being fully utilized [5]. Its outstanding feature is that the mutation of a single ecological environment unit is the main factor, and then the mutation unit is the center to radiate and spread around.
(3) According to the forecast results of Markov process, the ecological environment pattern of Jinjiang City is in a changing state, the ecological environment of dry land and paddy field is gradually decreasing, and the ecological environment of artificial buildings, especially the ecological environment of urban residents, is gradually increasing. This change will last for a long time, but it will eventually reach a relatively stable state, which indicates that Jinjiang City will eventually form a new ecological environment pattern of urban-rural economic integration.
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