JOURNAL OF NANJING FORESTRY UNIVERSITY ›› 2020, Vol. 44 ›› Issue (3): 133-141.doi: 10.3969/j.issn.1000-2006.201811056

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Multi⁃scale analysis of the effects of green space pattern on the urban surface thermal environment

ZHOU Wen1(), CAO Fuliang1(), ZHANG Rui2, WANG Guibin1   

  1. 1.College of Forestry, Nanjing Forestry University, Nanjing 210037, China
    2.College of Landscape Architecture, Nanjing Forestry University, Nanjing 210037, China
  • Received:2018-11-28 Revised:2019-04-23 Online:2020-05-30 Published:2020-06-11
  • Contact: CAO Fuliang E-mail:wenzhou0305@hotmail.com;fuliangcaonjfu@163.com

Abstract: Objective

Urban greenspace can be an effective contributor to mitigation of the urban heat island (UHI) effect and adaption to urban climate change. Previous studies have confirmed that the relationship between urban green pattern and land surface temperature (LST) is sensitive to spatial resolution of applied remote sensing imagery; however, little is known about spatial extent, another scaling issue. This study examined the effects of greenspace pattern on urban cooling and the influence of spatial extent when applied to derive landscape metrics. Understanding how the spatial pattern of urban greenspace affects the cooling intensity at different spatial extents is essential for creating a more scientific urban green network to better counteract the UHI effect.

Method

The study applied Landsat?8 TIRS imagery to derive LST data and Spot 6 imagery to retrieve the land-use and land-cover (LULC) map. The spatial pattern of woodland was measured by landscape metrics over four spatial extents/scales (90 m × 90 m, 180 m × 180 m, 360 m × 360 m and 720 m × 720 m) using a moving-window approach based on the LULC map. The relationship between landscape metrics and LST was established using correlation analyses and regression analyses.

Result

At patch level, the size, shape and connectivity with neighboring greenspaces all affect the cooling intensity of woodland. Meanwhile, patch area (PA) is the main factor influencing the LST of grassland. An increase in size and shape complexity can effectively reduce the LST within the greenspace. Compared with different LULC types, water performs best in urban cooling, followed by woodland and grassland, respectively. At class level, areas with a higher percentage of woodland cover experience a greater cooling effect, and a 10% increase of woodland resulted in a decrease in LST of 1.03 ℃. When given a fixed amount of woodland cover, aggregated distribution provides a stronger cooling effect than relative fragmented distribution. This study has suggested that landscape composition is more important than spatial configuration in determining the magnitude of LST. Moreover, results also demonstrated that changing spatial extent had significant impacts on the relationship between spatial pattern of urban greenspace and LST. Specifically, the significance of correlation between percentage of landscape (PLAND), mean patch size (MPS), largest patch index (LPI), and LST decreased as the spatial extent increased, and increased as the spatial extent increased between number of patches (NP), aggregation index (AI) and LST. The relationship between mean patch shape index (Shape_MN) and LST is not as sensitive as other landscape metrics to spatial extent. The findings in this study indicate that multi-scale analysis is required to fully explore the relationship between urban green pattern and LST.

Conclusion

Quantifying the relationship between spatial patterns of greenspaces and cooling intensity will provide a better prediction of the optimal pattern required to cool the urban environment, thus providing practical suggestions for urban greenspace planning and sustainable development.

Key words: urban greenspace, multi-scale analysis, landscape pattern, cooling effect, land surface temperature (LST)

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