An Analysis of Urban Green Landscape Pattern in Chengdu City

Proceedings of 14th Youth Conference on Communication

An Analysis of Urban Green Landscape Pattern in Chengdu

City Based on CBERS/CCD

DAN Bo1, DAN Shang-ming2, XU Hui-xi3, XUE Wan-rong3 1. Sichuan Provincial Meteorological Observatory, Chengdu 610072, P.R.China 2. Sichuan Province Agrimeteorological Center, Chengdu 610072, P.R.China 3. Institute of Engineering Surveying, Sichuan College of Architectural Technology, Deyang 618000, P.R.China [email protected]

Abstract: Based on GIS and CBERS/CCD which was obtained on June 16, 2006, patches of urban green in the main urban areas of Chengdu are extracted using many quantitative indicators and by method of decision tree classification, according to principles and methods of landscape ecology. Patches of urban green are divided into four grades, and they are respectively small-scale patch, medium-scale patch, large-scale patch and special large-scale patch. The area proportion of small-scale patch is 3.8%, and that of medium-scale patch is 11.1%, that of large-scale patch is 22.3% and that of special large-scale patch is 62.8%.The results of fragmentation, contagion, diversity index, dominance and evenness are obtained. They are 0.854, 0.600, 0.657, 0.730 and 0.690 respectively. The research results think that scalability characteristics and divisional differences of green patches are obvious. A little number of green whose area is bigger mainly is composed of scenic spots, gardens and universities. There are many problems, for example, connectivity of urban green is low, structure of landscape is single, and spatial distribution is unbalanced. So, the government should attach importance to greening and management of urban and rural transitional zone which is being developed now. Keywords: CBERS/CCD, Urban Green, Landscape Pattern, Chengdu City

and Guangzhou City’s landscape patterns of urban green 1 INTRODUCTION based on SPOT image. Yu Xue-qin et al. [6] studied Human and nature depend on each other. Nowadays, landscape patterns of vegetation in park. SHEN Tao et it is sophisticated concept that human is in harmony with al.[7]& HAN Cong-cong et al.[8] studied extracting nature. People desire to have a good living environment methods to urban green and residential area using TM of urban to meet their survival needs, security needs and image, and WU Lu-lu et al.[9]& HUANG Shu-chun et spiritual needs. al.[10] studied extracting methods to urban green and Landscapes as visual perceptual objects, landscapes residential area using QuickBird image. Above re- as living places, landscapes as systems, landscapes as searches improved techniques and deepen the under- symbols, therefore, landscapes are aesthetic, experiential, standing of urban green landscape through quantitative scientific and meaningful[1]. Green Landscape is one of analysis. the elements of the city's ecological environment, and it This paper analyzed the status quo of green land- has become a focus of people. Now, great progress has scape in Chengdu City with a number of landscape indi- been made in characteristics of different objects and ces, which can provide the basis for analysis of urban multi-scale landscape using all kinds of remote sensing ecological environment. data, with support of GIS. For example, Li Ming-yang [2]

studied changes of forest landscape patterns of Lin’an in 2 THE STUDY AREA Zhejiang Province.HOU Wei [3] and GUO Cheng-xuan Chengdu City is located in the western Sichuan Ba- et al. [4] respectively analyzed Yantai and Guangzhou sin and hinterland of Chengdu Plain, which is the Si- City’s landscape patterns of urban green based on TM chuan Province of political, economic and cultural center. image. WANG Tian-ming et al. [5] analyzed Harbin City The geographic coordinate of the city center is 30º39.7´E

and 104º3.8´N.The line distances between the city center This research work was financial supported by “the Key Research Project of Environmental Protection Bureau of and Dujiangyan and Qingcheng Mountain which lie in Sichuan Province (2008HBY002)”. the west of the center is 55 km, and that between the city

center and Longquan Mountain which lie in the east of ter, green, building and road. About 30-40 test points are the center is 25 km.It is subtropical monsoon climate, extracted and digital number (DN) of five bands are ob-

sufficient heat, abundant rainfall, distinct seasons, more tained from image by visual judging (statistical results in clouds, little sunshine.. Annual precipitation of the city is Table 1). about 1000mm, which concentrates in July and August. The following are the sorting results of average of

The annual average temperature is 16.3℃ . DN. For band1, building>road>water>green, the DN of Chengdu City includes 19 counties. The population green is close to that of water; for band2, building>road> of Chenghua District, Jinjiang District, Wuhou District, green > water; for band3, building>road> green > water,

Qingyang District and Jinniu District is 0.48 million, the DN of green is close to that of water; for band4, 0.39 million, 0.66 million, 0.65 million and 0.59 million green >building>road>water; for band5, building>road> respectively [11].The area within the First Circuit Road, green > water.

the Second Circuit Road and the Third Circuit Road re- NDVI (Normalized Difference Vegetation Index) spectively is 30km2, 62km2 and 200km2.The research was defined as the following: NDVI= (NIR-RED)/ areas are above five districts, which locate within the (NIR-RED), Where RED represents the red wave band of

Third Circuit Road. The area of above five districts re- the visible light, and NIR represents the near-infrared

2 2 2 2 spectively is 64km , 29km , 47km , 25km and wave band. If NDVI<0, the NDVI value was regard as 0. 35km 2(Figure 1.). Statistical of NDVI occur in Table 1. There is distinct difference between green and oth-

The Second Circuit Road Jinniu ers objects according to above comparative analysis. For Chenghua band4, the DN of water is the smallest. So, water can be The First Qingyang judged above all. In most cases, for band4, the DN of Circuit Road green is bigger than that of building and road. But, for Wuhou band1, 2, 3 and 5, the DN of building and road is bigger

The Third Circuit Road Jinjiang than that of green. Above rules of DN can regard as the

one of the judging conditions of green. At the same time,

Figure 1. St udy area-Chengdu City the NDVI of green greatly is bigger than that of others objects, so, NDVI can also regard as the judging condi-

3 DATA AND METHODOLOGY tions of green.

3.1Data of remote sensing 3.3 Method to data processing

CBERS/CCD data are applied into this study, which Green information is extracted by decision tree were obtained on June 16, 2006.It’s spatial resolution is classification module of ENVI software. Figure 2.reflects 19.5m.The spectral scope of band1-5 is 0.45～0.52μm, technical flow of decision tree classification. After test again and again, judging valve value between water and 0.52 ～ 0.59μm, 0.63 ～ 0.69μm, 0.77 ～ 0.89μm and shade is 72, and judging valve value of NDVI is 0.43. 0.51 ～0.73μm respectively. Area of patches is obtained according to the number 3.2Analysis of spectrum and NDVI of objects of pixel. That is ,Area equals to the number of There are four types of typical objects according to pixel×19.5×19.5÷10000 （ hm2 ） .According to area, characteristic of CBERS/CCD.They are respectively wa- patches of green are divided into four grades, and they

Table 1. Typical objects’ Digital Number (DN) of five bands and their NDVI

Band1 Band 2 Band 3 Band 4 Band 5 NDVI Type of objects Scope Average Scope Average Scope Average Scope Average Scope Average Scope Average Water 52-76 64.6 58-109 84.0 29-56 43.2 20-98 56.3 35-71 53.7 ＜0.0-0.39 0.173 Green 55-88 64.4 72-134 89.9 34-63 44.7 122-232 159 49-88 58.8 0.36-0.66 0.557 Building 70-104 84.8 91-179 132 52-100 70.4 78-156 109 60-117 81.0 0.12-0.29 0.216 Road 65-93 79.9 86-148 116 47-76 61.6 75-121 101 59-93 73.6 0.12-0.36 0.241

are respectively small-scale patch( ＜ 0.2 hm2), me- The results of quantity, area, average area and den- dium-scale patch(0.2～1 hm2), large-scale patch(1～5 sity of green patches within the ring road occur in Table

2 2 hm ) and special large-scale patch(＞5 hm ). 2. The area of green within the First Circuit Road and The results of fragmentation, contagion, diversity that between the First Circuit Road and the Second Cir- index, dominance and evenness of green landscape are cuit Road is about 30km2.The number of green patches is obtained according to reference [5] and [12]. all about 260, but the total area of green is respectively 158.8hm2 and 192.9 hm2,the difference of area among RS Data them is about 20%.From the First Circuit Road to the

Second Circuit Road and the Third Circuit Road, the area Y B4＜72 Water, Shade of green gradually increase, and the average area of green increase from 0.618hm2 to 0.739hm2 and 1.347hm2. N The trend of patch density is that slightly reducing first, Non-water, Non-shade and then increasing. The number and area proportion of four types of Y B4＞B1, B2, B3 and B5 Building, Road green patches occur in Table 3. The number proportion

N refers to the number of this type green patches take up Non-building, Non-road the total number of green patches, and the area proportion refers to the total area of this type green patches take

Y up the total area of green patches. In research area, the Non-green NDVI＜0.43 number proportion of four types of green patches dou- N bled increase from special large-scale patch to

Green small-scale patch, but the area proportion of four types of green patches is in contrast.Esepecially, the number pro- Figure 2. The flow chart of green extracted using decision tree portion of special large-scale patch is only 4.9%，but the classification area proportion is 62.8%, which shows that large-scale 4 Results patch and special large-scale patch are main body of ur- Two aspects of research: according to the character- ban green. istics of urban spatial layout, the study area is divided 4.2Characteristics of green patch in five districts into three levels from inside to outside taking main ring The number, total area, average area and density of road of Chengdu City as the border (Figure 1. (left)). The green patches in five districts occur in Table 4. Among study area is divided into five districts according to ad- them, the number of green patches in Chenghua District ministrative divisions (Figure.1 (right)). is a maximum, that is 637, total area and average area of 4.1 Spatial distribution of all kinds of green green patches is a maximum, that is respectively 910.6 patches hm2and 1.430hm2.The density of green patches in Qin- Above comprehensive analysis shows that reservoir -2 inundation will give little influence upon ecological en- gyang district is a maximum, that is 10.48•km . The vironment.

Table 2. The results of quantity, area, average area and density of green patches within the ring road

Between the First Between the Second Within the First Items Circuit Road Circuit Road Total Circuit Road and the Second Circuit Road and the third Circuit Road Quantity of green patches 257 261 1437 1955 Total Area (hm2) 158.8 192.9 1935.8 2287.5 2 Average Area(hm ) 0.618 0.739 1.347 1.170 Density of Green Patches (n•km-2) 8.57 8.16 10.41 9.78

Table 3. The number and area proportion (%) of four types of green patches within the ring road

Types of Within the First Circuit Between the First Between the Second In study area green patches Road Circuit Road Circuit Road and the Second Circuit Road and the third Circuit Road Number Area pro- Number Area pro- Number Area pro- Number Area proportion proportion portion proportion portion proportion portion proportion Small-scale 62.3 8.2 65.9 7.7 48.9 3.0 52.9 3.8 Medium-scale 28.4 21.4 21.4 12.2 30.6 10.1 29.1 11.1 Large-scale 5.8 27.5 10.0 24.1 14.9 21.7 13.1 22.3 Special 3.5 42.9 2.7 56.0 5.6 65.2 4.9 62.8 Large-scale Total 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0

Items Chenghua Jinjiang Wuhou Qingyang Jinniu Quantity of green patches 637 265 490 262 301 Total Area (hm2) 910.6 378.4 494.6 283.6 231.8

Average Area(hm2) 1.430 1.428 1.009 1.083 0.770

Density of Green Patches (n• 9.95 9.14 10.43 10.48 8.60 km-2)

Table 4. Distribution statistics of green patches in five districts

number, total area, average area and density of green The number and area proportion of special large-scale

patches in Jinniu district is a minimum, among which, patch green in Jinniu District is a minimum; the result is the average area and density of green patches is only respectively only 2.3% and 43.8%.From above analysis, 54% of Chenghua and Jinjiang Districts’, and the density there is obvious difference in spatial distribution of -2 of green patches is only 8.6•km . Green types. The number and area proportion of four types of

Table 3. The number and area proportion (%) of four types of green patches within the ring road green patches in fiver districts occur in Table 5 Discussions 5.Compared with small-scale and medium-scale patch green, the results in Chenghua District, Jinjiang District, Analyze Spatial Structure of green landscape Using

Wuhou District and Qingyang District are close. The landscape pattern indices. number proportion of small-scale and medium-scale 5.1Spatial distribution characteristics of green patch green is respectively about 50% and 30%. The area landscape proportion of small-scale and medium-scale patch green Landscape pattern indices of green within the ring is respectively from 2.8% to 4.4% and from 9.9% to road occur in Table 6. Fragmentation reflects the number 12.3%. The number proportion of small-scale patch of patches per unit area. Fragmentation of green land- green in Jinniu District is 58.5% and that of me- scape in research area is 0.854. Fragmentation of green dium-scale is 25.5%, but the area proportion is bigger landscape within the First Circuit Road is 1.618 , greater than that of others districts. The number proportion of degree of fragmentation, and that between the Second large-scale patch green in five districts is close. There is Circuit Road and the third Circuit Road is 0.742, smaller great difference in the area proportion, that of Chenghua degree of fragmentation. There is obvious difference in an Jinjiang District is lower than 20%, but that of Jinniu evenness inside and outside of the Second Circuit Road, District is 35.6%. The number and area proportion of the result inside of he Second Circuit Road does not ex- special large-scale patch green in Chenghua District is a ceed 0.54 and the result outside of the Second Circuit maximum; the result is respectively 5.5% and 68.5%.

Road is 0.74, which shows that spatial distribution of 5.2Characteristics of green landscape in five districts green landscape is uneven. There is great difference in contagion, diversity index and dominance. Landscape pattern indices of green in five districts occur in Table 7.The minimum fragmentation of green

Table 6. Landscape pattern indices of green within the ring road Between the First Between the Second The whole research Items Within the First Circuit Road Circuit Road Circuit Road area and the Second Circuit Road and the third Circuit Road Fragmentation 1.618 1.353 0.742 0.854

Contagion 0.663 0.664 0.583 0.600 Diversity Index 0.633 0.583 0.667 0.657

Dominance 0.753 0.803 0.720 0.730 Evenness 0.540 0.513 0.740 0.690

Table 7. Landscape pattern indices of green in five districts

Items Chenghua Jinjiang Wuhou Qingyang Jinniu

Fragmentation 0.700 0.700 0.991 0.924 1.299

Contagion 0.593 0.588 0.601 0.598 0.632 Diversity Index 0.661 0.670 0.650 0.660 0.639 Dominance 0.724 0.717 0.736 0.727 0.748 Evenness 0.709 0.729 0.682 0.693 0.614

Table 5. The number and area proportion (%) of four types of green patches in five districts

Chenghua Jinjiang Wuhou Qingyang Jinniu Types of green Number Area pro- Number Area pro- Number Area pro- Number Area pro- Number Area pro- patches proportion portion proportion portion proportion portion proportion portion proportion portion

Small-scale 51.3 2.9 49.4 2.8 53.9 4.4 52.3 4.1 58.5 6.7

Medium-scale 30.1 9.9 30.9 10.5 28.2 12.3 30.5 12.3 25.6 13.9 Large-scale 13.0 18.8 14.7 19.9 12.9 25.3 11.1 22.6 13.6 35.6 Special Large-scale 5.5 68.5 4.9 66.7 5.1 58.0 6.1 61.0 2.3 43.8 Total 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0

landscape occurs in Chenghua and Jinjiang District, The research results obviously reflect scalability and that is 0.854. The maximum fragmentation of green characteristics and divisional differences of green landscape occurs in Jinniu District, and that is 1.299. The patches in Chengdu City. There is obvious difference in maximum contagion of green landscape occurs in Jinniu spatial distribution of green patch types. Green structure

District, and that is 0.632. The minimum Contagion of in Jinjiang District is relatively reasonable, but that in green landscape occurs in Jinjiang District, and that is Jinniu District need further improvement. 0.588. The Contagion of green landscape occurs in Wu- Large-scale patch and special large-scale patch are hou, Chenghua and Qingyang District range between the main body of urban green. In recent ten years, compre- maximum and the minimum. There is no obvious differ- hensive improvements for Fu River, Nan River and Sha ence in diversity index and dominance in five districts. River improve the green landscape in city, but the green

The maximum evenness of green landscape occurs in patches look scarce. A little number of green whose area Jinjiang District, and that is 0.729, which shows that is bigger mainly is composed of scenic spots, gardens green structure is relatively reasonable. The evenness in and universities. There are many problems, for example,

Jinniu District is only 0.614, which shows that green urban green lands connectivity is low, structure of land- structure need further improvement. scape is single, and spatial distribution is unbalanced. So, the government should attach importance to greening and 6 Conclusions

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