| Mountainous cities have unique topographic features and urban forms,which lead to the difference of urban thermal environment spatial pattern.Compared with other cities,the local microclimate environment of mountain cities is often diverse and complex due to the urban mountains.With the rapid development of urbanization,abundant cone-shaped or tower-shaped karst peaks and peak forests were surrounded by human-dominated urban matrix,forming urban remnant natural mountains(URNMs).URNMs,as the precious ecological resources,could provide a variety of ecosystem services in cities.In order to study the temporal and spatial differentiation of thermal environment in mountainous cities and the regulation effect of URNMs on urban microclimate,taking the built-up area of the Guiyang city center as the study area and the URNMs as the research object,the change of landscape pattern and its influence on urban thermal environment in Guiyang City under the background of urbanization were analyzed through a land surface temperature(LST)inversion,landscape pattern analysis and Pearson correlation analysis.The effect of cold island effect of URNMs on the cooling of surrounding communities and its influencing factors were analyzed through buffer analysis and regression analysis.Objective to understand the diurnal variation characteristics of microclimate and its regulation on human comfort through field microclimate measurement.The results are as follows:(1)The land use and landscape pattern of Guiyang city changed dramatically in the past 12 years,with the increase of patch number,fragmentation of patch and complexity of patch landscape structure.The spatial distribution of urban thermal environment changed from the central agglomeration in 2007 to the multi-core heat island distribution trend in 2019,and the heat island gradually spread from the center to the suburbs.The suitable scale of landscape pattern and LST was 600×600 m,which could reflect the correlation between land use types and LST.Impervious surface was the most dominant patch in the city,which was also the contribution source of the rise of LST,and URNMs were the main contribution source of the decline of LST.The cultivated land area decreased sharply,which mainly changed into impervious surface and urban green space.The four types of land use,URNMs,cultivated land,urban green space and water body,all had the effect of reducing urban LST.The cooling effect of water body was the strongest,and the LST decreased by0.39?for every 10%increase of water body area,the effect of urban green space on urban cooling was the worst.Among all kinds of ecological land,the proportion of URNMs area(PLAND)had the strongest correlation with surface temperature,and the correlation of cultivated land was the weakest.(2)The average temperature of 23 sample mountains was 32.8?,lower than the average surface temperature of built-up area,which was 33.6?.The temperature inside the mountain was lower at the top than at the waist and the foot of the mountain,the south slope and southeast slope was higher than that of other slopes.Compared with the surrounding environment,the mountain formed a local cold source and had a cool island effect,the cooling range was 0.2-2.5°C,the cooling distance was 30-330m,and the average cooling distance was approximately 170 m.At a buffer of 30 m,the URNMs cooled the surrounding environment most significantly,with a cooling range of 0.5°C,with the increased of distance,the cooling range decreased.In mountain landscape and terrain features,Planimetric Area(PA),landscape shape index(LSI),relief degree of land surface(RDLS),mean slope(Slope?MN)were significant positive correlation with cold island effect.When the PA of the mountain decreased to about 0.30 hm~2,the enhancement trend of cool island effect began to weaken.Therefore,the best threshold of vertical projection area for judging the intensity of cool island effect of URNMs in Guiyang city was 0.30 hm~2.Vegetation?Pl AND,Building?PD,Road?PD and Vegetation?PD had a significant impact on the mountain cool island(MCI)intensity in the range of 330 m.(3)The URNMs had the effect of cooling and humidification in summer,the cooling rate was between 1.02-6.63%,the cooling range was 0.3-2.2?,the humidification rate was between 0.2-13.2%,and the most effective was from 14:00 to16:00.In addition,the URNMs could adjust the comfort of human body in the range of 0.1-2.6.Because of different underlying surface types and vegetation coverage,mountain space had different effects on temperature and human comfort.Therefore,it is suggested that the composition of underlying surface of different space types and the collocation of plant communities should be considered when making use of mountain park. |
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