Characteristics Of Air Ions In Typical Stands Of Beijing Songshan National Nature Reserve

Air anion is an important index to measure ecological environment It has the functions of purifying air,regulating body and mind,and has higher ecological significance.The variation law of air ion concentration and monthly variation of typical stand types in this area were summarized.The evaluation parameters of air quality in different stands and the main factors influencing the variation of air ion concentration were studied.The research results are as follows:(1)There were differences in daily variations of air ions in different seasons.The diurnal variation of air ion concentration in summer is relatively violent,and the fluctuation is relatively stable in spring.The daily variation of air ion concentration was not obvious in autumn.The diurnal variation of air ion concentration in various typical forests in the Yanqing Division of the Beijing Winter Olympics was measured It was found that in addition to the daily variation law of the air anion in the summer birch forest,the daily variation law of air ion concentration in the forests was generally two peaks.The daily change law of air positive ion concentration has no obvious change rule of air negative ion concentration.(2)The monthly variation of air ion concentration in different stands increased gradually and then decreased The highest concentrations of air negative ions in typical stands were in July,August and September.The mean concentration of negative air ions is in turn:Mongolia oak(796 ion·cm-3)>Juglans mandshurica(793 ion·cm-3)>Mongolia(738 ion·cm-3)>poplar(711 ion·cm-3)>black birch(670 ion cm-3)>no woodland(422 ion·cm-3).The average concentration of positive air ions is in turn:Hu Taoqiu(770 ion cm-3)>Mongolia oak(764 ion·cm-3)>Mongolia(743 ion·cm-3)>poplar(722 ion·cm-3)>black birch(679 ion·cm-3)>no woodland(570 ion·cm-3).(3)The diurnal variation rule of unipolar coefficient and air quality evaluation coefficient is consistent with the variation rule of air ion concentration.The average value of the monopole coefficient from small to large was Mongolia oak(0.97)<Juglans mandshurica(0.98)<Mongolia Tilia(1.01)<black birch(1.02)<aspen(1.03)>no woodland(1.35).The monthly variation of monopole coefficient decreased first and then increased to a single trough.The average value of air quality evaluation coefficient from large to small was Mongolia oak(0.85)>Juglans mandshurica(0.83)>Mongolia Linden(0.74)>poplar(0.71)>black birch(0.67)>no woodland(0.32).The monthly variation rule of air quality evaluation coefficient of different stand is single peak type.(4)There was a significant difference in air anion concentration between different stands,and the difference between woodland and non woodland was the most obvious.There was also a difference in the concentration of positive ions between different stands.The difference between the positive ions of air in each stand was less than that of air in each stand.The difference between woodland and non woodland was the most obvious.Meteorological factors had the greatest influence on air ion concentration.Air ion concentration was negatively correlated with air temperature and relative humidity was positively correlated.The correlation between air ion concentration and soil physical and chemical properties was not significant.There was a positive correlation between air ion concentration and photosynthetic rate,transpiration rate and stomatal conductance in different stands,but negatively correlated with intercellular CO2 concentration.Except for chlorophyll B,air ion concentration was positively correlated with other pigments.