Combating climate change by increasing urban carbon storage is one of the critical issues which urban policymakers must address. Understanding the characteristics and driving factors of carbon storage changes during urbanization can assist urban managers in formulating responsive land use policies. This study employs the INVEST model to evaluate carbon storage in Shanghai from 2000 to 2020, analyzing land use changes and their carbon impacts. It analyzes the transformation of land use in Shanghai during the same period and its impact on carbon storage. Using a 1 km grid for sampling, this study examines the spatiotemporal distribution patterns of carbon storage in Shanghai. Furthermore, it employs linear regression to discuss the social and economic drivers influencing carbon storage in the city. Carbon storage in Shanghai, predominantly from cultivated land and artificial surfaces, increased from 16.78 Mt in 2000 to 18.40 Mt in 2020, with an annual rise of 0.81 Mt. The spatial distribution of carbon storage exhibited a stable southeast-northwest pattern, with variations in dispersion between the north-south and east-west directions. The distribution of carbon storage shifted from a bimodal to a unimodal pattern, indicating an overall increase. There was a significant positive correlation between carbon storage and both the per capita green space area and the industrial output value, which can be attributed to Shanghai’s policies on green industrial development. This research aids in formulating land use policies to enhance urban carbon storage.

Particulate matter (PM) in urban riparian green spaces are undesirable for human participation in outdoor activities, especially PM_2.5 and PM₁₀. The PM deposition, dispersion and modification are influenced by various factors including vegetation, water bodies and meteorological conditions. This study aimed to investigate the impact of vegetation structures and the river’s presence on PM in riparian zones. The spatial-temporal variations of PM_2.5 and PM₁₀ concentrations in three riparian vegetation communities with different structures (open grassland (G), arbor-grass (AG) and arbor-shrub-grass (ASG) woodlands) were monitored under relatively stable environment. The removal percentages (RP) and ratios of PM_2.5 and PM₁₀ were calculated and compared to identify the removal effect of vegetation structures and the river’s presence. It is found that: (1) when the wind was static (hourly wind speed < 0.2 m/s), the RP was ranked as follows: G > AG > ASG. When the wind was mild (0.2 m/s < hourly wind speed < 2 m/s), the RP was ranked as follows: G > ASG > AG. Generally, the G had the best removal effect during the monitoring period; (2) the lowest RP occurred in the middle of the G (–3.4% for PM_2.5, 1.8% for PM₁₀) while the highest RP were found in middle of the AG and ASG, respectively (AG: 2.1% for PM_2.5, 6.7% for PM₁₀; ASG: 2.4% for PM_2.5, 6.3% for PM₁₀). Vegetation cover changed the way of natural deposition and dispersion; (3) compared with static periods, PM removal percentages were significantly reduced under mild wind conditions, and they were positively correlated with wind speed during the mild-wind period. Thus, a piecewise function was inferred between wind speed and PM removal percentage; (4) for all three communities, the 1 m-to-river PM_2.5/PM₁₀ ratio was significantly lower than that at 6 m and 11 m, even lower than that in the ambient atmosphere. The river likely promoted the hygroscopic growth of PM_2.5 and the generation of larger-sized particles by coagulation effect. Based on these findings, open grassland space is preferred alongside rivers and space for outdoor activities is suggested under canopies in the middle of woodlands.

The interactions between CO₂ flux, an important component of ecosystem carbon flux, and climate change vary significantly among different ecosystems. In this research, the inter-annual variation characteristics of ecosystem respiration (RE), gross ecosystem exchange (GEE), and net ecosystem exchange (NEE) were explored in the temperate grassland (TG) of Xilinhot (2004–2010), the subtropical artificial coniferous forest (SACF) of Qianyanzhou (2003–2010), and the tropical rain forest (TRF) of Xishuangbanna (2003–2010). The main factors of climate change affecting ecosystem CO₂ flux were identified by redundancy analysis, and exponential models and temperature indicators were constructed to consider the relationship between climate change and CO₂ flux. Every year from 2003 to 2010, RE and GEE first increased and then decreased, and NEE showed no significant change pattern. TG was a carbon source, whereas SACF and TRF were carbon sinks. The influence of air temperature on RE and GEE was greater than that of soil temperature, but the influence of soil moisture on RE and GEE was greater than that of air moisture. Compared with moisture and photosynthetically active radiation, temperature had the greatest impact on CO₂ flux and the exponential model had the best fitting effect. In TG and SACF, the average temperature was the most influential factor, and in TRF, the accumulated temperature was the most influential factor. These results provide theoretical support for mitigating and managing climate change and provide references for achieving carbon neutrality.

Soil heat flux (G) not only affects the Earth’s surface energy balance but also models of calculating soil evaporation. A better understanding on the effect of timing, soil and vegetation on riparian G helps to improve energy balance closure and G simulation in riparian areas with various woodlands. This paper examined diurnal and seasonal variation patterns of soil heat flux in urban riparian areas, together with its relationship with net radiation (Rn) including midday G/Rn and the hysteresis phenomenon under the mutual influence of the timing, soil wetness and vegetation conditions. Study sites lie in the riparian areas of Shanghai with seven vegetation-covered conditions—grassland (C_H), broadleaf evergreen woodlands with shrubs (C_CO), broadleaf evergreen woodlands (C_CH), broadleaf deciduous woodlands with shrubs (C_UO), broadleaf deciduous woodlands (C_UH), conifer with shrubs (C_MO) and conifer (C_MH). Hourly data of Rn and G on typical days in four seasons starting from 11/2020 to 10/2021 were obtained with automated data-logging sensors. Diurnal variations in soil heat flux were characterized as two patterns depending on leaf area index (LAI)—unimodal curves followed cycles of Rn in woodlands with low LAI (C_CH, C_CO, C_H and C_UO) and sinusoidal ones in woodlands with high LAI (C_MO, C_MH and C_UH). Midday G/Rn was generally no more than 10% with slight variations in most woodlands across the four seasons, but upward trends in the grass and C_UO were observed in the afternoon. They were found significantly correlated with SWC. For sparse-canopied riparian sites, hourly G was found to be significantly correlated with Rn and SWC in summer, whereas, for dense sites, the role of canopy characteristics overwhelmed soil properties. Equations were derived to estimate diurnal G from Rn, SWC and LAI. The G of all riparian sites was subject to hysteresis problems to Rn. Phase shifts ranged from one to eight hours in riparian sites and were positively related with LAI and SWC, mainly accounting for the second diurnal pattern of G.

Riparian microclimate studies are gaining increasing attention due to their close ecological, climatologic and aesthetic interactions with lives in both natural and urban areas. Historically, many researchers studied thermal regimes of rivers and river temperature responses to different management strategies. Near-river microclimate characteristics and relevant energy balance were not fully understood. This review documents recent research on near-river microclimatic features and energy exchanging processes, roles of macroclimate, rivers, riparian vegetation and topography play in microclimate mitigation, their ecological importance in terms of biodiversity support and human thermal comfort promotion. It also emphasizes potentials of studies on integration of rivers and plants, as well as their controls on heat exchanging. This study is hopefully useful for river scholars to strengthen the comprehension for further research, as well as for river designers and managers to make informed decisions of sustainable urban development.