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Landscape pattern MACRS analysis and the optimal utilization of Shiyang River Basin based on RS and GIS approach
Acta Ecologica Sinica 29 (2009) 216–221
Contents lists available at ScienceDirect
Acta Ecologica Sinica journal homepage: www.elsevier.com/locate/chnaes
Landscape pattern MACRS analysis and the optimal utilization of Shiyang River Basin based on RS and GIS approach Wei Wei a,*,1, Zhao Jun a, Wang Xu-feng b, Zhou Zhao-ye c, Li Hai-liang a a
College of Geography and Environmental Science, Northwest Normal University, Lanzhou 730070, China Cold and Arid Regions Environmental and Engineering Research Institute, CAS, Lanzhou 730000, China c College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou 730000, China b
a r t i c l e
i n f o
Keywords: GIS RS Accumulative cost resistance surface Landscape optimization Shiyang River Basin
a b s t r a c t Chose the arid interior district Shiyang River basin four issues of Landsat/TM images from 1986 to 2006 to visually interpret, and analyze the natural succession of ecological environment and the landscape pattern characteristic under the human activity interference. The results showed that in past 20 years, the number of landscape patch has increased, but the average patch size was decreasing, which explained that the landscape fragmentation degree was increasing, the landscape integrity was declining. The edge density of landscape remained invariable basically, which explained its stability maintained good. The diversity and evenness index continually enhanced, the diversity increased from 0.73 in 1986 to 0.84 in 2006. The mean core patch area of study area reduced from134.47 hm2 in 1994 to 127.67 hm2 in 2006, which indicated that the landscape core area was decreasing. On the one hand, it accelerated circulatory speed of species and reduced resistance of the energy flux. On the other hand it destroyed the integrity of the original landscape, easily caused the core area reducing continually, and led to vicious circle of the landscape separation. Seen from the whole study area, The utilization of landscape developed to the heterogeneous direction, indicated the proportional difference between various landscapes types was increasing, this kind of change has reflected the human activity’s influence to the whole landscape to a certain extent. It is believed that there are a series of landscape ecological problems such as low landscape ecological connectivity, simplified landscape structure and the more oasis fragmentation. In order to solve these problems, according to the principle that the movements of flow, energy and material in a landscape are related to some factors such as distance, time, impedance, etc., this study adopts the minimum accumulative resistance surface (MARS), the minimum cost resistance (MCR) model, and uses the surface diffusion technology to analyze compactness of landscape structure and the spatial difference of ecological function in Shiyang River basin. Then constructs some landscape components such as source, corridor and ecological node to strengthen the spatial connection of ecological network, and further discusses the landscape pattern optimization proposal. Ó 2009 Ecological Society of China. Published by Elsevier B.V. All rights reserved.
1. Introduction The landscape function must base on its own structure, the function is also the manifestation of the structure. The landscape structure refers to the order that their internal various essential factors interact, and the function refers to the whole effect to their outside. Therefore, different landscape structures should have the corresponding landscape functions, and the landscape functions also have the complex relations among every structural unit, each structural unit has the especially occurrent background, existent value, predominance and all kinds of relationships [1]. The land* Corresponding author. E-mail address: [email protected] (W. Wei). 1 Wei Wei (1982–), Master student, specialized in GIS, RS Application.
scape pattern is the spatially inhomogeneous performance which influences by natural factor and the artificial factor together [2]. It is the result of each complex physical, biological and the social factors interact. It is also deeply affects and determines each kind of ecological process [3]. The landscape pattern optimization is based on landscape pattern, its function and the ecological interaction. Through optimizing each kind of landscape type, adjusting the spatial and the quantitative distributed pattern to make it have the biggest landscape ecological benefit, and finally promote the region’s sustainable development. Many researches are the landscape element attribute and the interrelation through qualitative and quantitative analysis, some actual solutions still lack operation and academic support. Besides, in the landscape scale level, the corresponding relationships between landscape pattern and the process as well as the influence
1872-2032/$ - see front matter Ó 2009 Ecological Society of China. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.chnaes.2009.08.003
W. Wei et al. / Acta Ecologica Sinica 29 (2009) 216–221
to the landscape function are still very difficult to describe through quantifying. So the landscape pattern optimization research is still a difficult problem in the ecological field [4–6]. How to deal with the contradiction between the human space and the natural ecological space reasonably has become a focal point that the numerous geographers and the land superintendents must pay attention to. Therefore, how to construct significant landscape components or combinations from the ecological space, and control the ecological process through synthetically understanding the landscape pattern, function and the process to effectively promote the ecological functional continuity effectively are very difficult problems. RS and GIS technology were used to analyze landscape pattern, the landscape unit correlation in various directions and the whole spatial structure through adopting the pattern optimization approach, as well as the practical optimization measure to deal with a series of problems above. 2. Study area The Shiyang river basin is one of the three inland river basins in the Hexi corridor, lying in the east of the corridor, Gansu Province, north of the Qilian mountains and between the Badanjilin desert and the southern part of the Tenggeli desert. The basin occupies an area of 4.16 104 km2 (101°410 –104°160 E and 36°290 – 39°270 N) and consists of seven counties. The basin is located in continental temperate zone with arid climate and variable topography. The annual precipitation is 100–600 mm, whereas the annual pan evaporation is 700–2600 mm. The Shiyang River originates from the Qilian mountains with eight tributaries, which are mainly fed by rainfall, snowmelt and glacier melt in the Qilian mountains. The total water resource is 16.61 108 m3, of which surface runoff is about 15.61 108 m3 and groundwater is 1.00 108 m3. The total water consumption by different industries and sectors is 28.54 108 m3 and agricultural irrigation water accounts for 86.02%. The cultivated land is 36.85 104 hm2; effective irrigated area is 30.98 104 hm2 [7]. The main cereal crops include spring wheat, maize and potato. Due to its arid climate, limited water resources and inappropriate water-related human activities, the area has developed serious loss of natural vegetation, and gradual soil salinization and desertification, which have greatly impeded the sustainable development of agriculture and economy in this region [8]. 3. Materials and methods 3.1. Data sources The images were obtained from four issues of LandsatTM/ETM+ from 1986 to 2006, used Albers Conical Equal Area projection, the GCS_Krasovsky_1940 geographical coordinate system, the spatial resolution is 30 m. The meteorological data were obtained from 32 meteorological stations in Shiyang River basin including the monthly precipitation covering the period 1986–2006. The analysis of landscape change was carried out according to the transfer matrix of every type educed with the aid of GIS technology by overlaying the four maps from 1986 to 2006, which were interpreted from corresponding period TM/ETM+ RS images. DEM is suitable for analyzing the spatial relationships between landscape environment and terrain of the study areas. 3.2. Landscape classification system and methods The atmospheric radiation correction and geometrical emendation were completed using ERDAS9, the RMS is 0.359, which
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is in the range of precision. Stacked on 432 bands together in different period to analyze the landscape change. Based on the explanation symbol to obtain various issue of landscape type vector and the attribute data in ArcView3.3a, and then established the landscape and the component database. According to landuse characteristic, the differences of landscape types, combining the land surface and vegetation of the Shiyang River basin, landscape types were divided into 14 types such as farmland, woodland, grassland, water area and bare rock (Fig. 1). Overlaid different period landscape type to obtain various issue of landscape type classification used ArcGIS software. In order to compute landscape indexes, the ArcGIS/Patch analysis and tabulate areas in ArcView/spatial analyst models were used.
3.3. The accumulation cost distance surface model According to the influencing degree that landscape cell to the landscape migration, the landscape units are classified different scales [9], and admeasured corresponding drag parameter for various landscape units to obtain the landscape resistance surface. Each resistance value of landscape unit can obtain through the formula (1):
Rj ¼
n X ðX i Y ij Þ ði ¼ 1; 2; . . . n; j ¼ 1; 2; . . . mÞ:
ð1Þ
i¼1
In the expressions (1) [10], Rj is cumulated obstruction of each landscape cell; Xi is the every index power; Yij is the comparative obstruction of j landscape cell which is confirmed by index i. Based on the resistance surface, used the minimum cost distance, and depended on the Spatial Analysis technology and method, the minimum cost value from source to each landscape cell was calculated. The model is as follows:
C L ¼ min
i¼1 X ðDk Rk Þ ðl ¼ 1; 2; . . . ; n; k ¼ 1; 2; . . . mÞ:
ð2Þ
n
In the expressions (2) [11], CL is the minimum cost of the Lth landscape cell to each source; n is the total counts of landscape cell; m is cell counts from the source to each cell; Dk is the distance from each cell to the source; Rk is the resistance value of the cell kth. Using grid graphical method to analyze landscape spatial patterns. The accumulative cost distance from cost surface to nearby source can be calculated based on the node/link theory and using the formula follows: n 1X ðC i þ C iþ1 Þ; 2 i¼1 pffiffiffi n 2X Acd2 ¼ ðC i þ C iþ1 Þ: 2 i¼1
Acd1 ¼
ð3Þ ð4Þ
In the two formulas: Ci expresses the ith cell cost value; Ci+1 refers to the (i + 1)th cell cost value along the move direction; n is the total cells; Acd is the cumulative cost distance from cost surface to nearby source; formula (3) is used when the cost surface moves along vertical or horizontal direction. When moves along diagonal direction, it must use formula (4).According to accumulative cost distance and cost weighted direction, the farmland, grassland, sandy and residential areas are chosen as the protected source areas [12–15]. Based on spatial analysis of GIS technology, used the accumulative cost distance model, the landscape ecological accumulative cost distance surface (Fig. 2) were obtained through synthesizing landscape sources and ecological function.
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W. Wei et al. / Acta Ecologica Sinica 29 (2009) 216–221
Fig. 1. Landscape type of study area in 1986, 1994, 2000 and 2006.
4. Results 4.1. Landscape pattern analyses in Shiyang River Basin With the landscape pattern indices (Table 1), through quantitative analysis of the landscape ecological pattern, the results show: from 1986 to 2006, the landscape patch number increased, but the mean patch size was reducing. This showed the landscape fragmentized degree was increasing and the landscape integrity was reducing. The landscape marginal density was maintained invariable basically, which explained that its stability kept normal. The diversity and homogeneous index were continually large. The diversity index enhanced from 0.73 in 1986 to 0.84 in 2006. All of these owed to the local government attached importance to the ecological environment construction, enhanced biological species protection and the biological negotiability in recent years. The core density is the main indication of the core landscape distribution. Their continuous growth shows that the separate degree of core patch area is degenerate. It indicates the disturbance factors exist in the interior part of landscape flux and material flux. The mean core patch area of study area reduced from134.47 hm2 in 1994 to 127.67 hm2 in 2006, which indicated that the landscape core area was decreasing. On the one hand, it accelerated circulatory speed of species and reduced resistance of the energy flux. On the other hand it destroyed the original landscape integrity, easily caused the core area reducing continually, and led to vicious circle of the landscape separation. From Fig. 1 and Table 2 it may known that farmland increased as a whole and the tendency was obvious, its area has increased 59,964 hm2 from 1986 to 2006. The woodland reduced slightly, but patch number increased from 1545 in 1986 to 1696 in 2006,
which has increased 151, and 7.55 per year. It explained that fragmentation degree was aggravating .The mean patch area in 1986 was 173.27 hm2, in 2006 was 158.97 hm2, it also explained fragmentation degree was increasing. Meanwhile, grassland patch number also dropped from 3146 in 1986 to 3085 in 2006. The mean patch size reduced from 361.42 hm2 in 1986 to 322.97 hm2 in 2006. Patch shape index first increased and then decreased, which showed that its change was very fierce. The fractal dimension maintained invariable. The patch index reduced 1.27, and the evenness reduced 0.12, but the fragmentation degree increased. The residential area increased more than any other landscape types except farmland. The patch number also obviously increased. The mean patch area was 9.65 hm2 in 1986 and 10.67 hm2 in 2006, which increased 1.02 hm2. The town and city expanded unceasingly, which indicated that human activity was enhanced, and the disturbance to landscape was also further enlarged. Meanwhile, its diversity indices increased 0.17, the evenness had decreasing trend (reduced 0.13), which indicated that the cities and countryside residential area expanded discretionarily, so the pressure to ecology of Minqin and Wuwei oasis was further accelerative. 4.2. The landscape spatial function and the optimization plans Some fields and segments need to be paid much attention according to the minimum clog model: The farmland interior and the fringe area need to be controlled strictly in order to avoid the soil erosion, desertification and a series of ecological degeneration (dust color and green color in Fig. 2a). The Grassland–Woodland Ecotone should be mainly protected, and the texture among the small batches must be marked out in order to reduce the obstruc-
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W. Wei et al. / Acta Ecologica Sinica 29 (2009) 216–221
Fig. 2. The normalized accumulative cost distance surface of core source.
Table 1 Landscape pattern index in 1986, 1994, 2000 and 2006. Year
NumP
MPS
ED
AWMSI
MPFD
SDI
SEI
CAD
MCA
TCAI
1986 1994 2000 2006
12,017 12,008 12,311 12,158
337.63 336.6 329.54 333.69
20.15 20.34 20.3 20.04
18.98 20.74 18.74 20.45
1.08 1.07 1.08 1.07
1.83 1.89 1.93 1.96
0.73 0.72 0.83 0.84
0.57 0.55 0.59 0.63
129.09 134.47 127.17 127.67
73.75 74.4 73.66 74
NumP: Number of patches; MPS: Mean patch size; ED: Edge density; AWMSI: Area weighted mean shape index; MPFD: Mean patch fractal dimension; SDI: Shannon diversity index; SEI, Shannon evenness index; CAD: Core area density; MCA: Mean core area; TCAI: Total core area index.
tion where species travel the boundary (yellow and red spots chiasm area in Fig. 2b). The saddle point around cost isoclines layers in the central of grassland (dust color spot in Fig. 2c) must be taken care of. It must prevent the interferences caused by human activities in the ecotone, and improve the using efficiency of physical flows and circulation efficiency of nutritional elements (Fig. 2d). The isolated habitat batches and big landscapes must be joined together to keep species continuous and bio-diversity increasing. The essence of landscape function is that the landscape elements produce ecological functional efficiency through the landscape flux interacting. It has impetus or hindrance to the material circulation and energy flux. Besides, the spatial function of the abutted landscape element and respective edge effect has important influence to the maintenance and exertion of landscape function [16]. Looked from the resistance, grassland and woodland can be promoted mutually in the maintenance of landscape ecological function. Resistance of farmland and the residential area are the biggest. In order to avoid the direct conflict of landscape function in the spatial pattern, some landscape components such as protective forest, interdictory grassland and artificial treelawn
are often configured. These landscape components have cushioning effect to the high resistance landscape, and are very helpful for the ecology functional maintenance and their harmony. In addition, some landscape factors have the slight obstructive function to other landscapes such as sandy land and farmland. Using the landscape accumulative cost distance surface, depending on the GIS spatial analysis module to separate cost value of landscape cell, the spatial neighborhood analysis to obtain the mutual restrictive classification of landscape spatial function is carried on through analyzing landscape component characteristics (Fig. 3). According to the obstructive and controllable ability of the core area to the entire region, the abilities can be divided into eight parts: All of these controllable areas of ecological function have the characteristics of interlaced distribution, mutual infiltration and interaction. They compose the integrated spatial function. Aiming at problems of the ecological functional connection, combining programming theory and landscape ecological principle, under the goal of strengthening ecological functional spatial connection, some approaches such as protecting core ecological patches, adjusting vegetation structure, building stepping-stone,
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W. Wei et al. / Acta Ecologica Sinica 29 (2009) 216–221
Table 2 Characteristic parameter statistical value of different landscape type in 1986, 1994, 2000 and 2006. Class
NumP
MPS
AWMSI
MPFD
SDI
SEI
a
1 2 3 4 5 6 7 8 9 10 11 12 13 14
1559 1545 3146 53 132 1 3764 553 158 282 67 318 386 53
411 173.27 361.42 94.34 73.71 64 9.65 1682.41 2844.75 732.59 455.87 63.18 649.96 1372.13
37 8.43 18.73 3.68 7.27 2.06 1.52 22.76 10.99 5.16 3.46 2.85 6.35 8.75
1.08 1.09 1.09 1.14 1.11 1.11 1.04 1.09 1.11 1.09 1.09 1.1 1.09 1.11
1.83 1.68 1.65 1.71 1.78 1.70 1.66 1.74 1.65 1.73 1.67 1.69 1.72 1.71
0.73 0.86 0.89 0.69 0.71 0.70 0.73 0.74 0.73 0.69 0.71 0.75 0.80 0.78
b
1 2 3 4 5 6 7 8 9 10 11 12 13 14
1597 1606 3189 70 133 21 3767 601 188 286 33 322 385 40
265.69 317.46 257.67 61.06 76.20 4.33 9.29 1576.21 1497.66 685.09 382.03 114.45 634.49 2173.57
17.19 30.99 26.17 1.49 1.42 1.2 1.08 24.17 10.95 5.56 2.51 2.19 6.15 11.64
1.08 1.09 1.07 1.04 1.04 1.03 1.06 1.09 1.09 1.04 1.09 1.09 1.07 1.12
1.89 1.69 1.74 1.67 1.79 1.68 1.75 1.78 1.70 1.72 1.71 1.75 1.74 1.71
0.72 0.84 0.88 0.79 0.75 0.68 0.66 0.76 0.79 0.73 0.71 0.76 0.69 0.74
Class
NumP
MPS
AWMSI
MPFD
SDI
SEI
c
1 2 3 4 5 6 7 8 9 10 11 12 13 14
1631 1571 3293 80 131 1 3818 577 164 286 67 313 386 53
424.45 170.62 339.49 60.47 76.15 64 10.11 1599.4 2723.4 701.74 455.87 59.82 650.06 1373.2
34.05 8.39 18.55 3.59 7.31 2.06 1.54 23.19 11.06 5.26 3.46 2.91 6.35 8.75
1.08 1.09 1.09 1.11 1.11 1.11 1.04 1.09 1.11 1.09 1.09 1.1 1.09 1.11
1.93 1.76 1.74 1.78 1.77 1.78 1.76 1.86 1.78 1.76 1.69 1.78 1.76 1.83
0.83 0.78 0.78 0.86 0.76 0.86 0.59 0.78 0.71 0.71 0.78 0.74 0.76 0.79
d
1 2 3 4 5 6 7 8 9 10 11 12 13 14
1669 1696 3085 71 136 1 3869 631 181 288 50 387 394 31
481.22 158.97 322.97 59.79 76.09 64 10.67 1512.8 2383.9 613.66 525.86 161.43 673.37 2327.2
38.56 7.5 20.14 3.69 7.23 2.06 1.65 22.96 11.47 5.07 3.61 2.92 6.48 8.81
1.08 1.09 1.09 1.11 1.11 1.11 1.04 1.09 1.11 1.08 1.09 1.09 1.09 1.14
1.96 1.79 1.80 1.71 1.77 1.66 1.83 1.82 1.67 1.27 1.73 1.78 1.77 1.79
0.84 0.76 0.77 0.81 0.76 0.73 0.60 0.76 0.83 0.69 0.76 0.79 0.71 0.73
1. Farmland; 2. woodland; 3. grassland; 4. water area; 5. overflow land; 6. glacier and snow; 7. residential area; 8. sandy desert; 9. godi; 10. salinized land ; 11. marsh land; 12. bare soil; 13. bare rock; 14. cold desert; (a) 1986; (b) 1994; (c) 2000 and (d) 2006.
Fig. 3. Landscape functional resistance classification.
intensifying connected corridor, establishing buffer ,promoting landscape heterogeneity and increasing greenbelt are taken to improve biologic diversity, material circulation and landscape pattern stability. But the spatial function of the landscape type and the conflicted scope of the landscape function must be considered in the actual space optimizing. Therefore, the landscape pattern optimization must follow the ecology suitability and the biological circulation principle. Existing ecological source such as grassland, woodland and water area must be treated seriously. Ecological corridor and ecological node should also be constructed and perfected. The concrete optimization programs are as follows:
(1) Farmland in Wuwei and Minqin oasis must be developed synthetically and managed scientifically. The grassland in Tianzhu alpine and woodlands on Qilian Mountain should be protected, strengthen ecological construction, and increased its core patch area to improve the ecological functions of landscape. The fragmentary distributed region such as residential areas must be controlled in order to reduce the indirect resistance to the ecological energy flux and destruction to the ecological source core area. (2) The ecological corridor is the link between each source area patch. It is also the main road of species and the energy circulation. So whether it is connected or not is an important factor which estimates correlation between ecological function and efficiency. The functional grade of corridor is usually mensurated by the connectivity. The essential of corridor effect lies in the existent gradient benefit field around certain scale corridors. The corridor benefit weakens gradually from center to periphery, and follows the distance attenuated rate [17]. This article uses accumulative cost distance model to build ecological corridor between Minqin and Wuwei oasis, northern desert of Minqin and farmland, Tianzhu alpine and Wuwei, Gulang County residential area and industrial area, various greenbelt, source areas and core patches according to the landscape ecological pattern situation of the study area. The width is general controlled between 200 and 300 m and combining patulous characteristic of artificial corridor such as shelter belt, virescenced zone in the downstream basin to build the corridor buffer in order to strengthen the ecological effect of the corridor. Meanwhile, the original landscape incision that was caused by the path corridor and river branches can be weaken by the constructed corridors. These corridors can also weaken the impact to the water ecosystem caused by the residential area.
W. Wei et al. / Acta Ecologica Sinica 29 (2009) 216–221
Fig. 4. Distribution range of landscape pattern optimized units.
(3) Ecological node is built on certain landscape dielectric surface. It provides moved and backtracked stack points. This article fully considered the correlated influence factors of landscape pattern and built ecological node in the spatial landscape to connect various ecological corridors between each source area. In order to supervise the landscape ecological construction practically, basing on the landscape component construction, the distribution range which contained the main optimized units and was waiting for optimized units were established according to the spatial distribution characteristic of landscape type and the conflict ponderance of landscape units nearby space (Fig. 4). Because of these landscape cells are badly impacted by landscape types such as the roads, the residential area and the sandy desert, some relational landscape types must be adjusted or changed to avoid the high ecological function to join the low functional component which can lead to the vicious circle of ecological environment. 5. Conclusions and discussion (1) Using landscape ecological theory, combining the time and space changes of landscape pattern, the basic ecological safety, compactness and spatial difference of ecological function were analyzed. The results show: In the past 20 years, farmland increased 79,964 hm2, woodland decreased 11094.97 hm2, grassland decreased 65,875 hm2, and the residential area increased 40,889 hm2. The landscape patch number has increased, but the average patch size was decreasing, explained that the landscape fragmentation degree was increasing, the landscape integrity was declining. The landscape marginal density maintained invariable basically, explained that its stability maintained good. The diversity and evenness indexes continually enhanced, the diversity increased from 0.73 in 1986 to 0.84 in 2006. The mean core patch area fell from 134.47 hm2in 1994 to 127.67 hm2 in 2006, explained the holistic core area of the landscape was reducing. Seen from the whole study area, the landscape developed to the heterogeneous direction, this indicated that the proportional difference among various landscapes types was increasing, this kind of change has reflected the human activity’s influence to the whole landscape to a certain extent.
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(2) Basing on functional spatial theory of landscape ecology and the GIS spatial analysis technology, using the minimum accumulative resistance surface and the cost surface model, with the aid of the surface diffusion technology, the ecological corridor and ecological node are built from the idiographic landscape space to strengthen ecological network compactness and connectivity through identifying ecological source area. It can solve some problems such as low landscape ecological connectivity, simplified landscape structure, the more oasis fragmentation, desert expanding and farmland increasing. Its method and the conclusion may supervise the landscape ecological construction and the ecological programming effectively. (3) At present, the landscape pattern optimization research is still in the initial period and does not have the accredited conclusion and the mature method. The optimized theory and method are still at the exploration stage. Besides, the mechanism of landscape pattern and its internal interaction are very complex to be understudied and put into practice. In addition, the underground landscape elements need to be anatomized filtrated and measured if using the accumulative cost distance model. Therefore, the landscape optimized research need further deepen and perfect in order to provide consummate rationale and method. Acknowledgements Foundation: National Key Project of Scientific and Technical Supporting Programs, No. 40671067; key subject of physical geography in Gansu Province; NWNU knowledge and science innovative project Programs, No. NWNU-KJCXGC-03-23. References [1] R.T.T. Forman, M. Godron, Landscape Ecology, John Wiley & Sons, New York, 1986. pp. 3–45. [2] P.R. Ehrlich, D. Wheye, Non-adaptive hilltopping behavior in male checkerspot butterflies (Euphydryas editha), American Naturalist 127 (1986) 477–483. [3] L.D. Harris, The Fragmented Forest: Island Biogeography Theory and the Preservation of Biotic Diversity, University of Chicago Press, Chicago, 1984. pp. 5–40. [4] Duning Xiao, The development and perspective of contemporary landscape ecology, in: D.N. Xiao (Ed.), Progress in Landscape Ecology, Hunan Science and Technology Press, Changsha, 1999, pp. 1–7. [5] R.T.T. Forman, Land Mosaics: The Ecology of Landscapes and Regions, Cambridge University Press, Cambridge, 1995. pp. 8–23. [6] M.G. Turner, Landscape ecology: the effect of pattern on process, Annual Review of Ecology and Systematics 20 (1989) 171–197. [7] S. Tong, X. Kang, Yang, et al., Spatial distribution of reference crop evapotranspiration in Shiyang River Basin, Journal of Shenyang Agriculture University 35 (6) (2004) 432–435. [8] X. Kang, L. Su, P. Tong, et al., The impacts of water-related human activities on the water–land environment of Shiyang River Basin, an arid region in Northwest China, Hydrological Sciences Journal 49 (3) (2004) 413–427. [9] Depeng Yue, Jiping Wang, Yongbing Liu, Landscape pattern optimization based on RS and GIS in Northwest of Beijing, Acta Geographica Sinica 62 (11) (2007) 1223–1231. [10] P.H. Lewis, Quality corridors for Wisconsin, Landscape Architecture 54 (2) (1964) 100–107. [11] I.L. McHarg, Human ecological planning at Pennsylvania, Landscape Planning (8) (1981) 109–120. [12] Qiuju Zhang, FuBojie, Liding Chen, Several problems about landscape pattern change research, Scientia Geographica Sinica 23 (3) (2003) 264–270. [13] Liding Chen, Bojie Fu, Source-sink landscape theory and its ecological significance, Acta Ecologica Sinica 26 (5) (2006) 1444–1449. [14] Duning Xiao, Linsheng Zhong, Ecological principles of landscape classification and assessment, Chinese Journal of Applied Ecology 9 (2) (1998) 217–221. [15] Kongjian Yu, Ecologically strategic points in landscape and surface model, Acta Geographica Sinica 53 (1998) 12–20. [16] A. Farina, Principles and Methods in Landscape Ecology, Chapman & Hall, 1998. pp. 12–30. [17] Yueguang Zong, The corridor of effects in urban ecological landscape planning—a case study on Beijing, Acta Ecologica Sinica 19 (2) (1999) 145–150.
Contents lists available at ScienceDirect
Acta Ecologica Sinica journal homepage: www.elsevier.com/locate/chnaes
Landscape pattern MACRS analysis and the optimal utilization of Shiyang River Basin based on RS and GIS approach Wei Wei a,*,1, Zhao Jun a, Wang Xu-feng b, Zhou Zhao-ye c, Li Hai-liang a a
College of Geography and Environmental Science, Northwest Normal University, Lanzhou 730070, China Cold and Arid Regions Environmental and Engineering Research Institute, CAS, Lanzhou 730000, China c College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou 730000, China b
a r t i c l e
i n f o
Keywords: GIS RS Accumulative cost resistance surface Landscape optimization Shiyang River Basin
a b s t r a c t Chose the arid interior district Shiyang River basin four issues of Landsat/TM images from 1986 to 2006 to visually interpret, and analyze the natural succession of ecological environment and the landscape pattern characteristic under the human activity interference. The results showed that in past 20 years, the number of landscape patch has increased, but the average patch size was decreasing, which explained that the landscape fragmentation degree was increasing, the landscape integrity was declining. The edge density of landscape remained invariable basically, which explained its stability maintained good. The diversity and evenness index continually enhanced, the diversity increased from 0.73 in 1986 to 0.84 in 2006. The mean core patch area of study area reduced from134.47 hm2 in 1994 to 127.67 hm2 in 2006, which indicated that the landscape core area was decreasing. On the one hand, it accelerated circulatory speed of species and reduced resistance of the energy flux. On the other hand it destroyed the integrity of the original landscape, easily caused the core area reducing continually, and led to vicious circle of the landscape separation. Seen from the whole study area, The utilization of landscape developed to the heterogeneous direction, indicated the proportional difference between various landscapes types was increasing, this kind of change has reflected the human activity’s influence to the whole landscape to a certain extent. It is believed that there are a series of landscape ecological problems such as low landscape ecological connectivity, simplified landscape structure and the more oasis fragmentation. In order to solve these problems, according to the principle that the movements of flow, energy and material in a landscape are related to some factors such as distance, time, impedance, etc., this study adopts the minimum accumulative resistance surface (MARS), the minimum cost resistance (MCR) model, and uses the surface diffusion technology to analyze compactness of landscape structure and the spatial difference of ecological function in Shiyang River basin. Then constructs some landscape components such as source, corridor and ecological node to strengthen the spatial connection of ecological network, and further discusses the landscape pattern optimization proposal. Ó 2009 Ecological Society of China. Published by Elsevier B.V. All rights reserved.
1. Introduction The landscape function must base on its own structure, the function is also the manifestation of the structure. The landscape structure refers to the order that their internal various essential factors interact, and the function refers to the whole effect to their outside. Therefore, different landscape structures should have the corresponding landscape functions, and the landscape functions also have the complex relations among every structural unit, each structural unit has the especially occurrent background, existent value, predominance and all kinds of relationships [1]. The land* Corresponding author. E-mail address: [email protected] (W. Wei). 1 Wei Wei (1982–), Master student, specialized in GIS, RS Application.
scape pattern is the spatially inhomogeneous performance which influences by natural factor and the artificial factor together [2]. It is the result of each complex physical, biological and the social factors interact. It is also deeply affects and determines each kind of ecological process [3]. The landscape pattern optimization is based on landscape pattern, its function and the ecological interaction. Through optimizing each kind of landscape type, adjusting the spatial and the quantitative distributed pattern to make it have the biggest landscape ecological benefit, and finally promote the region’s sustainable development. Many researches are the landscape element attribute and the interrelation through qualitative and quantitative analysis, some actual solutions still lack operation and academic support. Besides, in the landscape scale level, the corresponding relationships between landscape pattern and the process as well as the influence
1872-2032/$ - see front matter Ó 2009 Ecological Society of China. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.chnaes.2009.08.003
W. Wei et al. / Acta Ecologica Sinica 29 (2009) 216–221
to the landscape function are still very difficult to describe through quantifying. So the landscape pattern optimization research is still a difficult problem in the ecological field [4–6]. How to deal with the contradiction between the human space and the natural ecological space reasonably has become a focal point that the numerous geographers and the land superintendents must pay attention to. Therefore, how to construct significant landscape components or combinations from the ecological space, and control the ecological process through synthetically understanding the landscape pattern, function and the process to effectively promote the ecological functional continuity effectively are very difficult problems. RS and GIS technology were used to analyze landscape pattern, the landscape unit correlation in various directions and the whole spatial structure through adopting the pattern optimization approach, as well as the practical optimization measure to deal with a series of problems above. 2. Study area The Shiyang river basin is one of the three inland river basins in the Hexi corridor, lying in the east of the corridor, Gansu Province, north of the Qilian mountains and between the Badanjilin desert and the southern part of the Tenggeli desert. The basin occupies an area of 4.16 104 km2 (101°410 –104°160 E and 36°290 – 39°270 N) and consists of seven counties. The basin is located in continental temperate zone with arid climate and variable topography. The annual precipitation is 100–600 mm, whereas the annual pan evaporation is 700–2600 mm. The Shiyang River originates from the Qilian mountains with eight tributaries, which are mainly fed by rainfall, snowmelt and glacier melt in the Qilian mountains. The total water resource is 16.61 108 m3, of which surface runoff is about 15.61 108 m3 and groundwater is 1.00 108 m3. The total water consumption by different industries and sectors is 28.54 108 m3 and agricultural irrigation water accounts for 86.02%. The cultivated land is 36.85 104 hm2; effective irrigated area is 30.98 104 hm2 [7]. The main cereal crops include spring wheat, maize and potato. Due to its arid climate, limited water resources and inappropriate water-related human activities, the area has developed serious loss of natural vegetation, and gradual soil salinization and desertification, which have greatly impeded the sustainable development of agriculture and economy in this region [8]. 3. Materials and methods 3.1. Data sources The images were obtained from four issues of LandsatTM/ETM+ from 1986 to 2006, used Albers Conical Equal Area projection, the GCS_Krasovsky_1940 geographical coordinate system, the spatial resolution is 30 m. The meteorological data were obtained from 32 meteorological stations in Shiyang River basin including the monthly precipitation covering the period 1986–2006. The analysis of landscape change was carried out according to the transfer matrix of every type educed with the aid of GIS technology by overlaying the four maps from 1986 to 2006, which were interpreted from corresponding period TM/ETM+ RS images. DEM is suitable for analyzing the spatial relationships between landscape environment and terrain of the study areas. 3.2. Landscape classification system and methods The atmospheric radiation correction and geometrical emendation were completed using ERDAS9, the RMS is 0.359, which
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is in the range of precision. Stacked on 432 bands together in different period to analyze the landscape change. Based on the explanation symbol to obtain various issue of landscape type vector and the attribute data in ArcView3.3a, and then established the landscape and the component database. According to landuse characteristic, the differences of landscape types, combining the land surface and vegetation of the Shiyang River basin, landscape types were divided into 14 types such as farmland, woodland, grassland, water area and bare rock (Fig. 1). Overlaid different period landscape type to obtain various issue of landscape type classification used ArcGIS software. In order to compute landscape indexes, the ArcGIS/Patch analysis and tabulate areas in ArcView/spatial analyst models were used.
3.3. The accumulation cost distance surface model According to the influencing degree that landscape cell to the landscape migration, the landscape units are classified different scales [9], and admeasured corresponding drag parameter for various landscape units to obtain the landscape resistance surface. Each resistance value of landscape unit can obtain through the formula (1):
Rj ¼
n X ðX i Y ij Þ ði ¼ 1; 2; . . . n; j ¼ 1; 2; . . . mÞ:
ð1Þ
i¼1
In the expressions (1) [10], Rj is cumulated obstruction of each landscape cell; Xi is the every index power; Yij is the comparative obstruction of j landscape cell which is confirmed by index i. Based on the resistance surface, used the minimum cost distance, and depended on the Spatial Analysis technology and method, the minimum cost value from source to each landscape cell was calculated. The model is as follows:
C L ¼ min
i¼1 X ðDk Rk Þ ðl ¼ 1; 2; . . . ; n; k ¼ 1; 2; . . . mÞ:
ð2Þ
n
In the expressions (2) [11], CL is the minimum cost of the Lth landscape cell to each source; n is the total counts of landscape cell; m is cell counts from the source to each cell; Dk is the distance from each cell to the source; Rk is the resistance value of the cell kth. Using grid graphical method to analyze landscape spatial patterns. The accumulative cost distance from cost surface to nearby source can be calculated based on the node/link theory and using the formula follows: n 1X ðC i þ C iþ1 Þ; 2 i¼1 pffiffiffi n 2X Acd2 ¼ ðC i þ C iþ1 Þ: 2 i¼1
Acd1 ¼
ð3Þ ð4Þ
In the two formulas: Ci expresses the ith cell cost value; Ci+1 refers to the (i + 1)th cell cost value along the move direction; n is the total cells; Acd is the cumulative cost distance from cost surface to nearby source; formula (3) is used when the cost surface moves along vertical or horizontal direction. When moves along diagonal direction, it must use formula (4).According to accumulative cost distance and cost weighted direction, the farmland, grassland, sandy and residential areas are chosen as the protected source areas [12–15]. Based on spatial analysis of GIS technology, used the accumulative cost distance model, the landscape ecological accumulative cost distance surface (Fig. 2) were obtained through synthesizing landscape sources and ecological function.
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Fig. 1. Landscape type of study area in 1986, 1994, 2000 and 2006.
4. Results 4.1. Landscape pattern analyses in Shiyang River Basin With the landscape pattern indices (Table 1), through quantitative analysis of the landscape ecological pattern, the results show: from 1986 to 2006, the landscape patch number increased, but the mean patch size was reducing. This showed the landscape fragmentized degree was increasing and the landscape integrity was reducing. The landscape marginal density was maintained invariable basically, which explained that its stability kept normal. The diversity and homogeneous index were continually large. The diversity index enhanced from 0.73 in 1986 to 0.84 in 2006. All of these owed to the local government attached importance to the ecological environment construction, enhanced biological species protection and the biological negotiability in recent years. The core density is the main indication of the core landscape distribution. Their continuous growth shows that the separate degree of core patch area is degenerate. It indicates the disturbance factors exist in the interior part of landscape flux and material flux. The mean core patch area of study area reduced from134.47 hm2 in 1994 to 127.67 hm2 in 2006, which indicated that the landscape core area was decreasing. On the one hand, it accelerated circulatory speed of species and reduced resistance of the energy flux. On the other hand it destroyed the original landscape integrity, easily caused the core area reducing continually, and led to vicious circle of the landscape separation. From Fig. 1 and Table 2 it may known that farmland increased as a whole and the tendency was obvious, its area has increased 59,964 hm2 from 1986 to 2006. The woodland reduced slightly, but patch number increased from 1545 in 1986 to 1696 in 2006,
which has increased 151, and 7.55 per year. It explained that fragmentation degree was aggravating .The mean patch area in 1986 was 173.27 hm2, in 2006 was 158.97 hm2, it also explained fragmentation degree was increasing. Meanwhile, grassland patch number also dropped from 3146 in 1986 to 3085 in 2006. The mean patch size reduced from 361.42 hm2 in 1986 to 322.97 hm2 in 2006. Patch shape index first increased and then decreased, which showed that its change was very fierce. The fractal dimension maintained invariable. The patch index reduced 1.27, and the evenness reduced 0.12, but the fragmentation degree increased. The residential area increased more than any other landscape types except farmland. The patch number also obviously increased. The mean patch area was 9.65 hm2 in 1986 and 10.67 hm2 in 2006, which increased 1.02 hm2. The town and city expanded unceasingly, which indicated that human activity was enhanced, and the disturbance to landscape was also further enlarged. Meanwhile, its diversity indices increased 0.17, the evenness had decreasing trend (reduced 0.13), which indicated that the cities and countryside residential area expanded discretionarily, so the pressure to ecology of Minqin and Wuwei oasis was further accelerative. 4.2. The landscape spatial function and the optimization plans Some fields and segments need to be paid much attention according to the minimum clog model: The farmland interior and the fringe area need to be controlled strictly in order to avoid the soil erosion, desertification and a series of ecological degeneration (dust color and green color in Fig. 2a). The Grassland–Woodland Ecotone should be mainly protected, and the texture among the small batches must be marked out in order to reduce the obstruc-
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Fig. 2. The normalized accumulative cost distance surface of core source.
Table 1 Landscape pattern index in 1986, 1994, 2000 and 2006. Year
NumP
MPS
ED
AWMSI
MPFD
SDI
SEI
CAD
MCA
TCAI
1986 1994 2000 2006
12,017 12,008 12,311 12,158
337.63 336.6 329.54 333.69
20.15 20.34 20.3 20.04
18.98 20.74 18.74 20.45
1.08 1.07 1.08 1.07
1.83 1.89 1.93 1.96
0.73 0.72 0.83 0.84
0.57 0.55 0.59 0.63
129.09 134.47 127.17 127.67
73.75 74.4 73.66 74
NumP: Number of patches; MPS: Mean patch size; ED: Edge density; AWMSI: Area weighted mean shape index; MPFD: Mean patch fractal dimension; SDI: Shannon diversity index; SEI, Shannon evenness index; CAD: Core area density; MCA: Mean core area; TCAI: Total core area index.
tion where species travel the boundary (yellow and red spots chiasm area in Fig. 2b). The saddle point around cost isoclines layers in the central of grassland (dust color spot in Fig. 2c) must be taken care of. It must prevent the interferences caused by human activities in the ecotone, and improve the using efficiency of physical flows and circulation efficiency of nutritional elements (Fig. 2d). The isolated habitat batches and big landscapes must be joined together to keep species continuous and bio-diversity increasing. The essence of landscape function is that the landscape elements produce ecological functional efficiency through the landscape flux interacting. It has impetus or hindrance to the material circulation and energy flux. Besides, the spatial function of the abutted landscape element and respective edge effect has important influence to the maintenance and exertion of landscape function [16]. Looked from the resistance, grassland and woodland can be promoted mutually in the maintenance of landscape ecological function. Resistance of farmland and the residential area are the biggest. In order to avoid the direct conflict of landscape function in the spatial pattern, some landscape components such as protective forest, interdictory grassland and artificial treelawn
are often configured. These landscape components have cushioning effect to the high resistance landscape, and are very helpful for the ecology functional maintenance and their harmony. In addition, some landscape factors have the slight obstructive function to other landscapes such as sandy land and farmland. Using the landscape accumulative cost distance surface, depending on the GIS spatial analysis module to separate cost value of landscape cell, the spatial neighborhood analysis to obtain the mutual restrictive classification of landscape spatial function is carried on through analyzing landscape component characteristics (Fig. 3). According to the obstructive and controllable ability of the core area to the entire region, the abilities can be divided into eight parts: All of these controllable areas of ecological function have the characteristics of interlaced distribution, mutual infiltration and interaction. They compose the integrated spatial function. Aiming at problems of the ecological functional connection, combining programming theory and landscape ecological principle, under the goal of strengthening ecological functional spatial connection, some approaches such as protecting core ecological patches, adjusting vegetation structure, building stepping-stone,
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Table 2 Characteristic parameter statistical value of different landscape type in 1986, 1994, 2000 and 2006. Class
NumP
MPS
AWMSI
MPFD
SDI
SEI
a
1 2 3 4 5 6 7 8 9 10 11 12 13 14
1559 1545 3146 53 132 1 3764 553 158 282 67 318 386 53
411 173.27 361.42 94.34 73.71 64 9.65 1682.41 2844.75 732.59 455.87 63.18 649.96 1372.13
37 8.43 18.73 3.68 7.27 2.06 1.52 22.76 10.99 5.16 3.46 2.85 6.35 8.75
1.08 1.09 1.09 1.14 1.11 1.11 1.04 1.09 1.11 1.09 1.09 1.1 1.09 1.11
1.83 1.68 1.65 1.71 1.78 1.70 1.66 1.74 1.65 1.73 1.67 1.69 1.72 1.71
0.73 0.86 0.89 0.69 0.71 0.70 0.73 0.74 0.73 0.69 0.71 0.75 0.80 0.78
b
1 2 3 4 5 6 7 8 9 10 11 12 13 14
1597 1606 3189 70 133 21 3767 601 188 286 33 322 385 40
265.69 317.46 257.67 61.06 76.20 4.33 9.29 1576.21 1497.66 685.09 382.03 114.45 634.49 2173.57
17.19 30.99 26.17 1.49 1.42 1.2 1.08 24.17 10.95 5.56 2.51 2.19 6.15 11.64
1.08 1.09 1.07 1.04 1.04 1.03 1.06 1.09 1.09 1.04 1.09 1.09 1.07 1.12
1.89 1.69 1.74 1.67 1.79 1.68 1.75 1.78 1.70 1.72 1.71 1.75 1.74 1.71
0.72 0.84 0.88 0.79 0.75 0.68 0.66 0.76 0.79 0.73 0.71 0.76 0.69 0.74
Class
NumP
MPS
AWMSI
MPFD
SDI
SEI
c
1 2 3 4 5 6 7 8 9 10 11 12 13 14
1631 1571 3293 80 131 1 3818 577 164 286 67 313 386 53
424.45 170.62 339.49 60.47 76.15 64 10.11 1599.4 2723.4 701.74 455.87 59.82 650.06 1373.2
34.05 8.39 18.55 3.59 7.31 2.06 1.54 23.19 11.06 5.26 3.46 2.91 6.35 8.75
1.08 1.09 1.09 1.11 1.11 1.11 1.04 1.09 1.11 1.09 1.09 1.1 1.09 1.11
1.93 1.76 1.74 1.78 1.77 1.78 1.76 1.86 1.78 1.76 1.69 1.78 1.76 1.83
0.83 0.78 0.78 0.86 0.76 0.86 0.59 0.78 0.71 0.71 0.78 0.74 0.76 0.79
d
1 2 3 4 5 6 7 8 9 10 11 12 13 14
1669 1696 3085 71 136 1 3869 631 181 288 50 387 394 31
481.22 158.97 322.97 59.79 76.09 64 10.67 1512.8 2383.9 613.66 525.86 161.43 673.37 2327.2
38.56 7.5 20.14 3.69 7.23 2.06 1.65 22.96 11.47 5.07 3.61 2.92 6.48 8.81
1.08 1.09 1.09 1.11 1.11 1.11 1.04 1.09 1.11 1.08 1.09 1.09 1.09 1.14
1.96 1.79 1.80 1.71 1.77 1.66 1.83 1.82 1.67 1.27 1.73 1.78 1.77 1.79
0.84 0.76 0.77 0.81 0.76 0.73 0.60 0.76 0.83 0.69 0.76 0.79 0.71 0.73
1. Farmland; 2. woodland; 3. grassland; 4. water area; 5. overflow land; 6. glacier and snow; 7. residential area; 8. sandy desert; 9. godi; 10. salinized land ; 11. marsh land; 12. bare soil; 13. bare rock; 14. cold desert; (a) 1986; (b) 1994; (c) 2000 and (d) 2006.
Fig. 3. Landscape functional resistance classification.
intensifying connected corridor, establishing buffer ,promoting landscape heterogeneity and increasing greenbelt are taken to improve biologic diversity, material circulation and landscape pattern stability. But the spatial function of the landscape type and the conflicted scope of the landscape function must be considered in the actual space optimizing. Therefore, the landscape pattern optimization must follow the ecology suitability and the biological circulation principle. Existing ecological source such as grassland, woodland and water area must be treated seriously. Ecological corridor and ecological node should also be constructed and perfected. The concrete optimization programs are as follows:
(1) Farmland in Wuwei and Minqin oasis must be developed synthetically and managed scientifically. The grassland in Tianzhu alpine and woodlands on Qilian Mountain should be protected, strengthen ecological construction, and increased its core patch area to improve the ecological functions of landscape. The fragmentary distributed region such as residential areas must be controlled in order to reduce the indirect resistance to the ecological energy flux and destruction to the ecological source core area. (2) The ecological corridor is the link between each source area patch. It is also the main road of species and the energy circulation. So whether it is connected or not is an important factor which estimates correlation between ecological function and efficiency. The functional grade of corridor is usually mensurated by the connectivity. The essential of corridor effect lies in the existent gradient benefit field around certain scale corridors. The corridor benefit weakens gradually from center to periphery, and follows the distance attenuated rate [17]. This article uses accumulative cost distance model to build ecological corridor between Minqin and Wuwei oasis, northern desert of Minqin and farmland, Tianzhu alpine and Wuwei, Gulang County residential area and industrial area, various greenbelt, source areas and core patches according to the landscape ecological pattern situation of the study area. The width is general controlled between 200 and 300 m and combining patulous characteristic of artificial corridor such as shelter belt, virescenced zone in the downstream basin to build the corridor buffer in order to strengthen the ecological effect of the corridor. Meanwhile, the original landscape incision that was caused by the path corridor and river branches can be weaken by the constructed corridors. These corridors can also weaken the impact to the water ecosystem caused by the residential area.
W. Wei et al. / Acta Ecologica Sinica 29 (2009) 216–221
Fig. 4. Distribution range of landscape pattern optimized units.
(3) Ecological node is built on certain landscape dielectric surface. It provides moved and backtracked stack points. This article fully considered the correlated influence factors of landscape pattern and built ecological node in the spatial landscape to connect various ecological corridors between each source area. In order to supervise the landscape ecological construction practically, basing on the landscape component construction, the distribution range which contained the main optimized units and was waiting for optimized units were established according to the spatial distribution characteristic of landscape type and the conflict ponderance of landscape units nearby space (Fig. 4). Because of these landscape cells are badly impacted by landscape types such as the roads, the residential area and the sandy desert, some relational landscape types must be adjusted or changed to avoid the high ecological function to join the low functional component which can lead to the vicious circle of ecological environment. 5. Conclusions and discussion (1) Using landscape ecological theory, combining the time and space changes of landscape pattern, the basic ecological safety, compactness and spatial difference of ecological function were analyzed. The results show: In the past 20 years, farmland increased 79,964 hm2, woodland decreased 11094.97 hm2, grassland decreased 65,875 hm2, and the residential area increased 40,889 hm2. The landscape patch number has increased, but the average patch size was decreasing, explained that the landscape fragmentation degree was increasing, the landscape integrity was declining. The landscape marginal density maintained invariable basically, explained that its stability maintained good. The diversity and evenness indexes continually enhanced, the diversity increased from 0.73 in 1986 to 0.84 in 2006. The mean core patch area fell from 134.47 hm2in 1994 to 127.67 hm2 in 2006, explained the holistic core area of the landscape was reducing. Seen from the whole study area, the landscape developed to the heterogeneous direction, this indicated that the proportional difference among various landscapes types was increasing, this kind of change has reflected the human activity’s influence to the whole landscape to a certain extent.
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(2) Basing on functional spatial theory of landscape ecology and the GIS spatial analysis technology, using the minimum accumulative resistance surface and the cost surface model, with the aid of the surface diffusion technology, the ecological corridor and ecological node are built from the idiographic landscape space to strengthen ecological network compactness and connectivity through identifying ecological source area. It can solve some problems such as low landscape ecological connectivity, simplified landscape structure, the more oasis fragmentation, desert expanding and farmland increasing. Its method and the conclusion may supervise the landscape ecological construction and the ecological programming effectively. (3) At present, the landscape pattern optimization research is still in the initial period and does not have the accredited conclusion and the mature method. The optimized theory and method are still at the exploration stage. Besides, the mechanism of landscape pattern and its internal interaction are very complex to be understudied and put into practice. In addition, the underground landscape elements need to be anatomized filtrated and measured if using the accumulative cost distance model. Therefore, the landscape optimized research need further deepen and perfect in order to provide consummate rationale and method. Acknowledgements Foundation: National Key Project of Scientific and Technical Supporting Programs, No. 40671067; key subject of physical geography in Gansu Province; NWNU knowledge and science innovative project Programs, No. NWNU-KJCXGC-03-23. References [1] R.T.T. Forman, M. Godron, Landscape Ecology, John Wiley & Sons, New York, 1986. pp. 3–45. [2] P.R. Ehrlich, D. Wheye, Non-adaptive hilltopping behavior in male checkerspot butterflies (Euphydryas editha), American Naturalist 127 (1986) 477–483. [3] L.D. Harris, The Fragmented Forest: Island Biogeography Theory and the Preservation of Biotic Diversity, University of Chicago Press, Chicago, 1984. pp. 5–40. [4] Duning Xiao, The development and perspective of contemporary landscape ecology, in: D.N. Xiao (Ed.), Progress in Landscape Ecology, Hunan Science and Technology Press, Changsha, 1999, pp. 1–7. [5] R.T.T. Forman, Land Mosaics: The Ecology of Landscapes and Regions, Cambridge University Press, Cambridge, 1995. pp. 8–23. [6] M.G. Turner, Landscape ecology: the effect of pattern on process, Annual Review of Ecology and Systematics 20 (1989) 171–197. [7] S. Tong, X. Kang, Yang, et al., Spatial distribution of reference crop evapotranspiration in Shiyang River Basin, Journal of Shenyang Agriculture University 35 (6) (2004) 432–435. [8] X. Kang, L. Su, P. Tong, et al., The impacts of water-related human activities on the water–land environment of Shiyang River Basin, an arid region in Northwest China, Hydrological Sciences Journal 49 (3) (2004) 413–427. [9] Depeng Yue, Jiping Wang, Yongbing Liu, Landscape pattern optimization based on RS and GIS in Northwest of Beijing, Acta Geographica Sinica 62 (11) (2007) 1223–1231. [10] P.H. Lewis, Quality corridors for Wisconsin, Landscape Architecture 54 (2) (1964) 100–107. [11] I.L. McHarg, Human ecological planning at Pennsylvania, Landscape Planning (8) (1981) 109–120. [12] Qiuju Zhang, FuBojie, Liding Chen, Several problems about landscape pattern change research, Scientia Geographica Sinica 23 (3) (2003) 264–270. [13] Liding Chen, Bojie Fu, Source-sink landscape theory and its ecological significance, Acta Ecologica Sinica 26 (5) (2006) 1444–1449. [14] Duning Xiao, Linsheng Zhong, Ecological principles of landscape classification and assessment, Chinese Journal of Applied Ecology 9 (2) (1998) 217–221. [15] Kongjian Yu, Ecologically strategic points in landscape and surface model, Acta Geographica Sinica 53 (1998) 12–20. [16] A. Farina, Principles and Methods in Landscape Ecology, Chapman & Hall, 1998. pp. 12–30. [17] Yueguang Zong, The corridor of effects in urban ecological landscape planning—a case study on Beijing, Acta Ecologica Sinica 19 (2) (1999) 145–150.