Urban heat island effect as a driver for Specific Thallus Mass (STM) in lichens

The focus of community ecology has shifted from the description of taxonomic composition towards an understanding of community assembly based on species’ ‘functional traits’. The functional trait approach is well developed for vascular plants, utilising variability of continuous phenotypic characters that affect ecological fitness, such as specific leaf area, tissue nitrogen concentration or seed mass, to explain community structure. In contrast, community assembly studies for poikilohydric cryptogamic plants and fungi, such as lichens, remain focused on broad categorical traits such as growth form difference: fruticose, foliose or crustose. This study examined intra- and interspecific variability for two highly promising continuous phenotypic measurements that affect lichen physiology and ecological fitness: water-holding capacity (WHC) and specific thallus mass (STM). Values for WHC and STM were compared within and among species, and within and among key macrolichen growth forms (fruticose and green-algal and cyanolichen foliose species), asking whether these widely used categories adequately differentiate the continuous variables (WHC and STM). We show large intra- and interspecific variability that does not map satisfactorily onto growth form categories, and on this basis provide recommendations and caveats in the future use of lichen functional traits.

Cyanolichens ( Lobaria hallii , Lobaria retigera , Lobaria scrobiculata , Pseudocyphellaria anomala ) and cephalodial ( Lobaria pulmonaria ) and noncephalodial ( Platismatia glauca ) chlorolichens were sampled in dry open, mesic open, and mesic closed forests in central British Columbia. Specific thallus mass (STM), water-holding capacity (WHC), percent water content at saturation, and thickness of upper cortex, photobiont layer, and medulla plus lower cortex were measured. Whereas STM did not differ much between cyanolichens (9.8 ± 0.1 mg dry mass·cm–2) and chlorolichens (8.0 ± 0.1 mg dry mass·cm–2), cyanolichens had a WHC (20.3 ± 0.2 mg H2O·cm–2) that was nearly twice that of the chlorolichens (10.8 ± 0.2 mg H2O·cm–2). STM and WHC increased with light exposure at the studied sites, presumably as an acclimation to higher evaporation demands. Within species, WHC was strongly coupled to STM and increased substantially faster with STM in cyanolichens, compensating their inability to use humid air to restore photosynthesis. The photobiont layer was two times thicker in cyanolichens, whereas the thickest layer (the hydrophobic medulla) did not differ between cyanolichens and chlorolichens. Most interspecific variation (88.3%) in WHC could be accounted for in a multiple regression model where STM and photobiont to total thickness ratio were the most important independent variables. Photobionts thus play significant roles in the water economy of lichens.

Interspecific and intraspecific variability of water use traits in macrolichen species in a fragmented landscape along a climatic ecotone area

Green buildings are an important constituent part of the urban ecosystem; they act as an adjuster of temperature and humidity of the environment in cities, and can effectively alleviate the Urban Heat Island (UHI) effect. Existing studies on the UHI effect generally ignored the local information in the changes of the UHI effect, and the impact of the optimization of green building distribution on the UHI effect hadn’t been taken into consideration. To fill in this research gap, this paper aims to study the optimization of the distribution of green buildings based on the UHI effect. At first, this paper adopted a high-precision radiative transfer model to invert the temperature of earth surface in cities, and accurately calculate the UHI effect. Then, this paper analyzed the changes in the UHI effect caused by the optimization of the distribution of green buildings and the response of human activities, and used the time variation law of the single pixels of green buildings to reflect the spatial variation law of the UHI effect. At last, experimental results gave the optimization results of the distribution of green buildings based on the UHI effect.

Functional traits prolonging photosynthetically active periods in epiphytic cephalolichens during desiccation

Global warming has obtained more and more attention because the global mean land surface temperature (LST) has increased since the late 19th century. Urban heat island (UHI) effect and its thermal environment are the most important themes in urban climatology and environment researches. One of the possible causes to UHI effect is the drastic reduction in the green space in cities. The coastal cities of southeast Fujian province is the most economically developed and densely populated areas of Fujian province, even in China, and also it is experiencing rapid urbanlization that has resulted in remarkable UHI effect, which will be sure to inference the regional and urban climate, environment, and socio-ecomomic development. In this study, MODIS data of July to August acquired from 2001 to 2007 in coastal cities of southeast Fujian province were elaborately selected out to retrieve the metrics of, land surface tempertuare, normalized difference vegetation index (NDVI) and albedo so as to investigate the intensity, the spatial-temporal pattern, the tendency of UHI effect, monitor annual changes and evaluate the UHI effect though urban radio index (URI) over the study period. Additionally, a new methodology and analysis techniques what was called Urban Thermal Environment Information TuPu(UTEITP) was introduced to detect and measure within-class changes of LST from the spatial, temporal and processes view, try to find the conversion mechanism and analyze the relationship between LST, albedo and NDVI qualitatively. Morever, a correlation model was built to quantitatively analyze and better understanding the relationships between LST and NDVI, LST and albedo.The results showed that UHI effect was keeping on strengthening during the whole study period with a increase tendency overall.UTEITP provided a systematic and effective way to derive comparable changes and processes. Our analysis based on UTEITP and correlation model indicates that there was a linear relationship among surface temperature, NDVI and albedo for all study years, whereas the relationship between LST and NDVI was negative, but positive correlation was shown between NDVI and albedo. These result evidence reminds us to take some instructive measures to weaken the effect of urban heat island, improve the city's thermal and habitat environment and urban sustainable development.

The shortage of vegetation cover alongside urban structures and land hardscape in cities causes an artificial temperature increase in urban environments known as the urban heat island (UHI) effect. The artificial heat stress in cities has a particular threat for usability and health-safety of outdoor living in public space. Australia may face a likely 3.8°C increase in surface temperature by 2090. Such an increase in temperature will have a severe impact on regional and local climate systems, natural ecosystems, and human life in cities. This paper aims to determine the patterns of the UHI effect in micro-scale of Adelaide metropolitan area, South Australia. The urban near-surface temperature profile of Adelaide was measured along a linear east-west cross-section of the metropolitan area via mobile traverse method between 26 July 2013 and 15 August 2013. Results indicate that the while the maximum UHI effect occurs at midnight in the central business district (CBD) area in Adelaide, the afternoon urban warmth has more temperature variations (point-to-point variation), especially during the late afternoon when local air temperature is normally in its peak. Thus, critical measurement of heat-health consequences of the UHI effect need to be focused on the afternoon heat stress conditions in UHIs rather than the commonly known night time phenomenon. This mobile traverse urban heat study of Adelaide supports the hypothesis that the UHI effect varies in the built environment during daily cycles and within short distances. Classical UHI measurements are commonly performed during the night – when the urban-rural temperature differences are at their maximum. Thus, they fall short in addressing the issue of excess heat stress on human participants. However, having thermally comfortable urban microclimates is a fundamental characteristic of healthy and vibrant public spaces. Therefore, urban planning professionals and decision makers are required to consider diurnal heat stress alongside nocturnal urban heat islands in planning healthy cities. The results of this article show that the diurnal heat stress varies in the built environment during daily cycles and within short distances. This study confirms that the maximum urban heat stress occurs during late afternoon when both overall temperature and daily urban warmth are at their peak. Literature indicates that diurnal heat stress peaks in hard-landscapes urban settings while it may decrease in urban parklands and near water bodies. Therefore, urban greenery and surface water can assist achieving more liveable and healthy urban environments (generalisation requires further research). A better understanding of daily urban warmth variations in cities assists urban policy making and public life management in the context of climate change.

Impacts of land use/ land cover types on interactions between urban heat island effects and heat waves

Effects of urban form on the urban heat island effect based on spatial regression model

Epiphytic lichen growth in Mediterranean forests: Effects of proximity to the ground and reproductive stage

The urban heat island (UHI) effect is becoming an influential factor on the city's environment along with the rapid development of urbanization process. This paper uses Landsat-5 TM RS image of the year 1988, 2007 and 2010 based on NDVI <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TEM</sup> model and land temperature retrieval method to obtain Beijing land surface temperature distribution map through digital image processing and land surface temperature (LST) retrieval calculating using thermal infrared (TIR) remotely sensed satellite observation. The analysis showcases that urban heat island effect in Beijing has been dramatically intensified since 1988. Especially in recent years, the urban heat island effect has become increasingly apparent and seriously affected human's health in the way of changing temperature, barometric pressure, humidity, wind as well as air.

Under the trend of rapid urbanization, the urban heat island (UHI) effect has become a hot issue for scholars to study. In order to better alleviate UHI effect, it is important to understand the effect of landuse/landcover (LULC) and landscape patterns on the urban thermal environment from perspective of landscape ecology. This research aims to quantitatively investigate the effect of LULC landscape patterns on UHI effects more accurately based on a landscape metrics analysis. In addition, we also explore the complex relationship between land surface temperature (LST) and vegetation cover. Taking Zhengzhou City of China as a case study, an integrated method which includes the geographic information system (GIS), remote-sensing (RS) technology, and landscape metrics was employed to facilitate the analysis. Landsat data (2000–2014) were applied to investigate the spatiotemporal evolution patterns of LST and LULC. The results indicated that the mean LST value increased by 2.32°C between 2000 and 2014. The rise of LST was consistent with the trend of rapid urbanization in Zhengzhou City, which resulted in sharp increases in impervious surfaces (IS) and substantial losses of vegetation cover. Furthermore, the investigation of LST and vegetation cover demonstrated that fractional vegetation cover (FVC) had a stronger negative effect on LST than normalized differential vegetation index (NDVI). In addition, LST was obviously correlated with LULC landscape patterns, and both landscape composition and spatial configuration affected UHI effects to varying degrees. This study not only illustrates a feasible way to investigate the relationship between LULC and urban thermal environment but also suggests some important measures to improve urban planning to reduce UHI effects for sustainable development.

Impact of the 2008 Olympic Games on urban thermal environment in Beijing, China from satellite images

With the development of urbanization, the spatial and temporal distribution characteristics of the urban landscape pattern play a decisive role in the intensity of the urban heat island (UHI) effect. A panel data model was constructed to study the relationship between the UHI effect and landscape pattern in Kunming from 1995 to 2020 at four different scales. The results indicate: (1) The landscape pattern of Kunming changed obviously with time, the artificial patch increased, the natural patch decreased, and the UHI effect became more and more obvious; (2) With an increase in scale, the number of influencing variables continues to grow, and the impact of artificial patches gradually intensifies; (3) The normalized difference water index (NDWI) has the greatest influence on the UHI, and the cooling effect is more obvious with the increase in scale. Unlike previous studies, the spatial configuration of the landscape in Kunming City had a stronger effect on the UHI effect than the landscape grouping and vegetation index; (4) This paper introduces the panel data model into the discussion of the UHI for the first time, providing a new method for better understanding the changing patterns of the urban thermal environment.

Rapid urbanization has aggravated the urban thermal risk and highlighted the urban heat island (UHI) effect. To improve understanding on the effect of urbanization on the UHI effect, it is essential to determine the relationship between the UHI effect and the complexities of urban function and landscape structure. For this purpose, 5116 urban function zones (UFZs), representing the basic function units of urban planning, were identified in Beijing. Land cover and land surface temperature (LST) values were extracted based on remote sensing data. UFZ, land cover, and LST were used to represent the urban function, landscape, and UHI characteristics, respectively. Then, the effects of urban function and landscape structure on the UHI effect were examined. The results indicated that the urban thermal environment exhibited obvious spatiotemporal heterogeneity due to the variation of urban function and landscape complexity: (1) UFZs showed significantly different LST characteristics for different functions and seasons, and the mean LST gap among different types of UFZ can reach 1.72–3.85 °C. (2) During warm seasons, the UHI region is mainly composed of residential, industrial, and commercial zones, while recreational zones contribute as an important UHI source region during cold seasons. (3) Urban developed land and forest are the most important landscape factors contributing to the UFZ effect in the urban thermal environment. These findings have useful implications for urban landscape zoning to mitigate the UHI effect.