Humidifying Effect of Green Space during Spring in Yuxi Park of Shijiazhuang City of China

As one of the important parts of urban ecosystem, urban green space plays an irreplaceable role in maintaining the balance of carbon and oxygen, absorbing the pollution and removing dust, killing bacteria, purifying soil and water. To analyze the spatio-temporal changes of humidifying effect of green lands at the spring daytime, the authors monitored the air humidity within 1.8 m high from various underlying surfaces, including arbor-grass lands, shrub lands, herb lands and a cement pavement, from late February to late April in 2015 and 2016, when it was sunny and windless, in the Yuxi park of Shijiazhuang. The results were compared with the monitoring data of a bare land(190 m×120 m) without environmental interventions such as vegetation and water. The results could be summarized as follows:(1) The humidifying effect of green spaces was the weakest at 8:00 a.m. during the late February, whereas it was the strongest at 10:00 a.m.; from late March to late April, the humidifying effect of green spaces strengthened with the increase of air temperature, and the strongest was noted around 12:00-16:00.(2) The humidifying effect of various types of green lands was the strongest close to the ground, and reduced from 0.2 m to 1.8 m. This vertical stratification became apparent after the plants sprouted, the vertical difference of humidifying effect was the most significant in the herb lands, less significant in arbor-grass lands, and least in the shrub lands.(3) Multiple comparison analysis of the humidity data showed that relative humidity of all green lands achieved the significant level(P < 0.05), indicating the strong effect of landscape plants in adjusting atmospheric humidity in spring.(4) The humidifying effect of the artificial lake was more remarkable before the plants sprouted, however, with the rapid growth of plant leaves, theeffect gradually reduced and became even weaker than the effect of vegetation. Although the humidifying effect in spring was weaker than that in summer and autumn, the effect of humidification was more complicated during the growth of green leaves in spring than in summer and autumn. This is useful to construct the theory system of ecological environment effect of green lands in spring, summer and autumn.

Humidifying Effect of Riparian Wetland Park of Shijiazhuang, Hebei Province in Autumn

As an important part of urban green space system, wetland parks have good ecological environment and various landscape resources, which play an irreplaceable role in adjusting the climate, beautifying the environment and maintaining regional ecological balance. Therefore, research on humidifying effect of wetland park is of great significance. Air humidity below the height of 1.5 m above various underlying surfaces was measured in Taiping Riparian Wetland Park of Shijiazhuang. Monitoring time was selected in October 10–12, 2012 and six days among September and October, 2013 which were sunny days without wind(or the speed of wind less than 0.2 m/s). By analyzing the basic distribution regularity of humidity from horizontal and vertical directions at different times in autumn days, humidifying effect of various types of plants could be summarized from the sampled data. The humidifying effect of arbor-grasses can strengthen with the increase of temperature. The humidifying effect is the strongest at 10:00–14:00, then, it weakens after noon and the reduction rate tends to be smaller. Second, the humidity above the height of 0.2 m changes at a small scale and is much lower than that close to ground, which reveals great effect of ground cover plants and soil moisture. According to the monitoring data below the height of 1.5 m, the humidifying effect of shrubs is stronger than that of arbor-grasses. Last, the humidifying effect of surfaces with different land covers from strong to weak are shrubs, arbor-grasses, river. The rational allocation on various types of wetlands with a wide variety of structures can improve the atmospheric environment more effectively.

Effects of vegetation restoration on local microclimate on the Loess Plateau

With the implementation of the Grain for Green Project,vegetation cover has experienced great changes throughout the Loess Plateau(LP).These changes substantially influence the intensity of evapotranspiration(ET),thereby regulating the local microclimate.In this study,we estimated ET based on the Penman-Monteith(PM)method and Priestley-Taylor Jet Propulsion Laboratory(PT-JPL)model and quantitatively estimated the mass of water vapor and heat absorption on the LP.We analyzed the regulatory effect of vegetation restoration on local microclimate from 2000 to 2015 and found the following:(1)Both the leaf area index(LAI)value and actual ET increased significantly across the region during the study period,and there was a significant positive correlation between them in spatial patterns and temporal trends.(2)Vegetation regulated the local microclimate through ET,which increased the absolute humidity by 2.76-3.29 g m^(-3),increased the relative humidity by 15.43%-19.31%and reduced the temperature by 5.38-6.43℃per day from June to September.(3)The cooling and humidifying effects of vegetation were also affected by the temperature on the LP.(4)Correlation analysis showed that LAI was significantly correlated with temperature at the monthly scale,and the response of vegetation growth to temperature had no time-lag effect.This paper presents new insights into quantitatively assessing the regulatory effect of vegetation on the local microclimate through ET and helps to objectively evaluate the ecological effects of the Grain for Green Project on the LP.