As a major part of the urban green space system, street trees play a corresponding role in adjusting the thermal comfort of the environment and alleviating heat island effects. The correlation between the morphological structure and microclimate factors in the lower canopy of street trees was studied, using data that were captured with vehicle-borne LiDAR to model the morphological structure and geometric canopy features of six key street tree species in the built-up area of Zhumadian City, Henan Province. The regulating ability and differences of canopy geometry on cooling, humidification, shading, and Physiologically Equivalent Temperature (PET) were studied. Research shows that: (1) Canopy Volume (CV), Canopy Area (CA), Canopy Diameter (CD), and Tree Height (TH) have a linear negative correlation with air temperature, relative humidity, and luminosity. TH had significant effects on the air temperature and relative humidity (R² = 0.90, 0.96), and CV and CD had significant effects on luminosity (R² = 0.70, 0.63). (2) The oval-shaped plant (Platanus acerifolia (Aiton) Willdenow) had a strong cooling and shading ability, with an average daily cooling of 2.3 °C and shading of 318 cd/m². The spire-shaped plant (Cedrus deodara (Roxb.) G. Don) had a strong ability to humidify, with an average daily humidification of 4.5%. (3) The oval-shaped and spire-shaped plants had a strong regulation ability on PET, and the daily average regulation values were 40.5 °C and 40.9 °C, respectively. (4) The CD of the oval-shaped plant had a significant effect on PET (R² = 0.49), and the TH of the spire-shaped plant had a significant effect on PET (R² = 0.80), as well as a significantly higher CV and Leaf Area Index (LAI) than other street tree species. Therefore, selecting oval and spire canopy-shaped plants with a thick canopy, dense leaves, and high CD and TH values as street trees can provide significant advantages in cooling, humidifying, and shading, and can effectively adjust human comfort in the lower canopy understory. This study is the first to apply LiDAR technology to the regulation of urban microclimate. The research results provide a theoretical basis and quantitative reference for street tree design from the perspective of outdoor thermal comfort evaluation and play a guiding role in the application of LiDAR to urban forestry research.

In order to study the leaching of exogenous nitrogen during green space management and maintenance, the parameters of the model were calibrated through field monitoring and grow box simulation experiments, and the Model for Studying Nitrogen Transport in Green Space Ecosystems was established by using HYDRUS-2D software. Results showed that the model is highly reliable for simulating nitrogen transport in microtopography, with R² values greater than 0.9 and RMSE values below 5. Slope gradient was positively correlated with horizontal nitrogen differences (ammonium and nitrate nitrogen) and negatively correlated with vertical differences (p < 0.05), while nitrogen application was positively correlated with both horizontal and vertical differences in nitrate nitrogen and negatively correlated with ammonium nitrogen (p < 0.05). The vertical differences of soil ammonium nitrogen exhibited a significant negative correlation with slope (−0.837 to −0.851), while the horizontal differences of nitrate nitrogen showed a significant positive correlation, with correlation coefficients of 0.965 and 0.967 for surface and subsurface soils, respectively. The increasing nitrogen application rate exacerbated these discrepancies, with the highest nitrogen treatment (0.312 g) exhibiting the most pronounced differential effects. Notably, the horizontal variation in nitrate nitrogen reached 6.9-fold that of ammonium nitrogen, while the vertical discrepancy demonstrated a 7.0-fold magnitude relative to ammonium nitrogen levels.

Plant communities serve as the fundamental components of urban green spaces and play a critical role in mitigating climate change by reducing atmospheric CO₂ concentrations. The structural characteristics of plant communities have a significant impact on their carbon sequestration function. This study utilized aboveground carbon storage, soil carbon storage, and maintenance carbon emissions as quantifiers of carbon income and expenditure and examined 106 plant communities (20 m×20 m) in Zhengzhou Green Expo Park. The aim was to establish a statistical relationship model between the plant community structural characteristics and total annual carbon sequestration, providing a quantitative basis for regulating community structure to improve the carbon sequestration ability of urban green spaces. The results showed that density and coverage characteristics were significant factors positively correlated with the annual carbon sequestration of the plant communities. The fastest increase in annual carbon sequestration in the plant community reached 44%, from 183.04 kg CO₂-eq/y^− 1 to 327.67 kg CO₂-eq/y^− 1/400 m², with density ranging from 0.1 to 0.15 and coverage from 0.5 to 1. The carbon sequestration amount did not increase significantly following continuous increases in density and coverage characteristics. Density played a key structural role in regulating the total carbon sequestration of the plant communities, being 27.24 times more effective than coverage. This study provides valuable data for increasing the carbon sink ability of urban green spaces through plant structure regulation and supporting low-carbon development strategies in urban management and also has positive implications for reducing the atmospheric carbon content and mitigating climate warming potentials in urban green spaces.