The high-density development of urban centers has worsened outdoor thermal comfort in many cities. In this study, ENVI-met was used to simulate thermal comfort, and the universal thermal climate index (UTCI) and eight urban morphological indicators were calculated at 348 sampling points in the urban center. The correlation results are shown as follows: (1) Thermal comfort is significantly and positively correlated with impervious surface, green area ratio, and sky openness, showing a strong negative correlation with building density, floor area ratio, and shadow hours. (2) The UTCI value decreases by 0.998 °C for every 1 h increase in shadow hours, increases by 0.746 °C for every 10% increase in sky view factor, decreases by 0.462 °C when the building density increases by 10%, and decreases by 0.596 °C for every 10% increase in the impervious area ratio. (3) The sampling points with better thermal comfort have similar spatial characteristics such as higher building density, higher volume ratio, smaller green area ratio, longer shadow hours, and smaller sky openness. (4) In the planning and design of urban centers, increasing shade can improve the shadow hours in the environment. Specifically, large open sites should be avoided.

Michelia crassipes is a great ornamental plant, the flowers of which have high economic value. In this study, we employed headspace solid-phase microextraction (HS–SPME) combined with gas chromatography high-resolution mass spectrometry (GC–HRMS) for the first time to identify the volatile compounds emitted from different organs of M. crassipes flowers at different flowering stages. M. crassipes flower odor comprises 69 volatile compounds that are dominated by terpenes constituting 84% of collected volatiles. It was found that α-guaiene, β-caryophyllene and germacrene B had the highest relative amounts, while ethyl 3-methyl valerate, methyl benzoate and β-damascone had the highest odor activity values (OAVs). This contributed to the complex fruity, woody and floral aromas of M. crassipes. Total odor emission increased along the flower blooming, which was most abundant in the pistil followed by tepals and stamens. Paraffin sections of M. crassipes flower organs showed the highest density of oil secretory cells in the pistil at the full flowering stage, which was positively correlated with total odor release. The scent of the pistil and tepals was characterized by terpenes, whereas stamens was characterized by benzenoids. We suggest that the benzenoids in stamens might contribute to pollinator attraction in M. crassipes.

In this study, one-year-old seedlings of Paeonia ostii ‘Fengdan’ were used as materials. The method of spraying exogenous salicylic acid (SA), calcium chloride (CaCl₂) and abscisic acid (ABA) was used. The effects of different concentrations of SA, CaCl₂ and ABA on the heat tolerance of peony seedlings under high temperature stress were studied. The optimum concentration and mechanism of SA-, CaCl₂- and ABA-induced heat tolerance of peony seedlings under high temperature stress were discussed. The results showed that 100 μmol/L SA, 40 mmol/L CaCl₂ and 40 mg/L ABA had the best induction effect on the heat tolerance of peony. The effects of three exogenous substances on the heat resistance of peony seedlings were ranked as SA > CaCl₂ > ABA. The three exogenous substances mainly alleviated high temperature damage by alleviating the degradation of chlorophyll (Chl), relative electrical conductivity (Rec) content, increasing superoxide dismutase (SOD) activity, soluble proteins (SPs), free proline (Pro) and soluble sugars (SSs) content, and reducing SSs content under high temperature stress. The five indices had the most significant effect on the three exogenous substances in improving the heat resistance of peony seedlings. These could be used as an index to identify the heat resistance.

The RNA-Seq and gene expression data of mature leaves under high temperature stress of Paeonia suffruticosa ‘Hu Hong’ were used to explore the key genes of heat tolerance of peony. The weighted gene co-expression network analysis (WGCNA) method was used to construct the network, and the main modules and core genes of co-expression were screened according to the results of gene expression and module function enrichment analysis. According to the correlation of gene expression, the network was divided into 19 modules. By analyzing the expression patterns of each module gene, Blue, Salmon and Yellow were identified as the key modules of peony heat response related functions. GO and KEGG functional enrichment analysis was performed on the genes in the three modules and a network diagram was constructed. Based on this, two key genes PsWRKY53 (TRINITY_DN60998_c1_g2, TRINITY_DN71537_c0_g1) and PsHsfB2b (TRINITY_DN56794_c0_g1) were excavated, which may play a key role in the heat shock response of peony. The three co-expression modules and two key genes were helpful to further elucidate the heat resistance mechanism of P. suffruticosa ‘Hu Hong’.

Urban spatial expansion affects almost every dimension of sustainable urban development. A good grasp of the relationship between urban spatial evolution and carbon emissions can be the key to urban spatial governance. As a central city in the central region and a national low-carbon pilot city, Changsha has experienced a rapid expansion of construction land and growing carbon emissions. In this paper, four variable factors and five variable factors of carbon emission were used for the case city Changsha in 1979, 1996, 2003, 2008, 2013 and 2016. Based on the “double carbon” constraint target, the total carbon emissions, carbon-emission intensity and per capita carbon emission constraint indices were forecasted until 2030. They are 87.29 million t-CO₂, 0.45 t-CO₂/CNY10⁴ and 8.73 t-CO₂/person, respectively. The scale of urban land is controlled at 889.61; the constraint indices of residential, commercial service land, industrial land and road square land scales are 231.3 km², 143.88 km², 150.17 km² and 135.83 km², respectively. The land expansion intensity, urban compactness and shortest travel distance constraint indices are 6.19, 0.236 and 96,086.76 km, respectively. The results of this analysis can provide scientific guidance for the next step in territorial spatial master planning and low-carbon governance.

Global warming and the urban heat island (UHI) phenomenon have significant impacts on human activities, against which it is necessary to develop effective coping strategies. Based on the local climate zone (LCZ) system, this study used the land-cover and surface temperature data on the Chang–Zhu–Tan (CZT) urban agglomeration in China in 2006, 2010, 2016, and 2020 to analyze the impact of climate change on the land surface temperature (LST) under different land-cover types. The results illustrate that the LCZ map generated on the basis of the improved World Urban Database and Access Portal Tools (WUDAPT) is more accurate and efficient than the traditional method. The accuracy is increased by more than 15%. From 2006 to 2020, the main built-up types in the CZT urban agglomeration were the sparsely built, the large low-rise, and the compact mid-rise types. The low-plant type represents the most significant proportion of the natural types, followed by the water and the dense-tree types. The built-up types in the CZT urban agglomeration tend to be the high-rise, dense, and industrial types. Urban construction land is taken mainly from the sparsely built type of land. The average LST of the large low-rise and heavy-industry zones is significantly higher than the average LST of the three cities. The average LST values for the water and dense-tree zones are significantly lower than the other average LST values. The LST is stable in each LCZ, showing little correlation with the size of the LCZ area. Compact low-rise land use is ineffective against climate warming and inhibits economic growth. Compact high-rise and open high-rise land can not only effectively deal with climate warming but can also significantly stimulate economic growth. This paper helps us to understand the effect of land cover on climate warming and the economic benefits of LCZs in the CZT urban agglomeration and provides strategies to optimize the use of land resources.