In order to further understand the changing laws of environmental factors in large multi-span greenhouses under natural ventilation conditions and the internal relations between various environmental factors,and ultimately improve the precision of microclimate regulation of large multi-span greenhouses.Taking the multi-span greenhouse with a small spire structure in the Demonstration Base of Guangdong Agricultural Technology Extension Station as the research object,under the condition of natural ventilation with butterfly-shaped windows,the changes in temperature,humidity,wind speed and solar light intensity of different monitoring planes in the greenhouse were monitored.After analyzing the monitoring data,it was found that:1)The temperature gradient in the vertical direction in the large multi-span greenhouse is more obvious than that in the small greenhouse,and the highest average temperature difference monitored can reach 7.9℃.The velocity field in the multispan greenhouse is always maintained within the range of 0.3-0.4 m/s,and the ambient wind speed has no effect on the airflow speed in the greenhouse.The humidity and speed in the multi-span greenhouse show good uniformity.2)In a large multi-span greenhouse,the secondary radiation generated by the internal shading has less impact on the area near the ground,which can effectively reduce the ground temperature.3)Under the conditions studied in this research,the temperature and humidity in the greenhouse follow the external environment as well,showing that the greenhouse design is reasonable,and the air renewal and heat exchange inside and outside the greenhouse are good during natural ventilation.
Urban greenery is widely recognised as a strategy to mitigate urban overheating,and its shading capacity is crucial for improving microclimate and thermal comfort.Nevertheless,research on modelling the vegetation canopy radiation transfer(VCRT)process for the microscale is lacking,and most existing VCRT models are taken out from mesoscale models.In this study,we used canopy morphology and structure as an entry point to construct a VCRT model for the microscale,from the mesoscale model.Firstly,100 m and 1000 m were defined as the critical scales by scaling,and the effect of leaf distribution on VCRT was analysed.The VCRT model was made applicable to the microscale by introducing a scattered radiation source term and 6 leaf inclination distribution(LID)functions,and the results showed that the proposed model could improve the accuracy of canopy radiation absorptivity by about 11%.In addition,both leaf area index(LAI)and LID had significant effects on VCRT,and vegetation with LAI above 2 and spreading leaves had better shading effects.It is worth noting that urban greenery has an exciting potential for thermal comfort improvement,with the potential to regulate even extremely hot weather from near"very hot"(148 W/m2)to almost"comfortable"(69 W/m2).This study is a catalyst for improving the predictability of the VCRT process for microclimate and thermal comfort,providing theoretical support and implications for mitigating urban overheating and enhancing urban thermal resilience.
Junru YanLihua ZhaoXiufeng SunHuihui ZhaoHaichao ZhengYu Wang
Although the importance of forest margins in ecology is recognized, no study has been carried out in the Slătioara Secular Forest Reserve with reference to the variability of abiotic parameters along forest margins. With this study, we investigate to what extent microclimatic variables (air temperature—T_air, air humidity—H_air, soil temperature—T_soil, soil humidity—H_soil wind intensity (WIND) and photosynthetically active radiation intensity (PAR)) are correlated with the distance from the edge to the forest interior and the habitat type (forest interior, inner and outer edge and meadow) in the Slătioara Secular Forest Reserve. In order to measure these microenvironment variables we used the strip transect method, positioned perpendicular to the forest edge. Differences in the microenvironment variables considered in the analysis between the four habitat types were assessed using one-way ANOVA followed by Tukey-test post-hoc. To assess differences along transects, each of the six measurements went through a one-way ANOVA against distance to edge, followed by a Levene’s test for variances and finally a Tukey-test post-hoc. The results indicate that the values of microclimatic variables were significantly different in relation to the gradient of distance from the edge and to the habitat type (interior-exterior forest) and that edge habitats are significantly more susceptible to lower humidity, high winds, lower light and higher air temperatures than forest interior habitats. The ecological study of the edge areas in this reserve provides the basis for future research on forest dynamics and can guide conservation efforts to maintain the diversity and endemism of species in the Slătioara Secular Forest.
