摘要：
In this paper, the characteristics of changes in negative air ion concentration were investigated at forest edge of Jiulong mountain.We monitored the diurnal dynamic of negative air ion concentration and its variations along with the altitudinal gradient at forest edge and in the forest interior in September and October, 2017.Meantime, the mean, maximum, and minimum values of air temperature, air humidity, wind speed, saturated vapor pressure, net radiation, and effective radiation of photosynthesis were concurrently measured, and a path analysis was applied to quantitatively explore the relationships between meteorological factors and negative air ion concentration.The results showed that: (1) The average concentration of negative air ions in October was 80％higher than that in September.The diurnal variation of negative air ions concentration presented a trendency of decrease in September.The diurnal change showed a single peak curve in the early October, but it presented a curve of power function and had a downward trend in the mid and late October. (2) The concentration of negative air ions was 4％higher at forest edge than that in the forest interior.The concentration of negative air ions showed a wave shape along with the altitudinal gradient at forest edge;in contrast, it presented a clear single peak type along with the elevation gradient in the forest interior. (3) By using stepwise regression analysis, the minimum air humidity, saturated vapor pressure, and air temperature were extracted from all the meteorological factors to conduct the path analysis.The direct path coefficients of these three selected meteorological factors were 1.064, -0.817, and 0.468, respectively.Therefore, the lowest air humidity was the dominantly direct factor that affected the concentration of negative air ions.The minimum air temperature was the main indirect factor via influencing the minimum air humidity and saturated vapor pressure.We highlight the importance of forest edge area in forest health planning by contrasting the concentration of negative air ions at forest edge and in the forest interior.%文章以九龙山林缘地区空气负离子浓度变化特征为研究对象, 通过观测9月和10月北京九龙山林缘地区空气负离子浓度, 研究空气负离子浓度日变化和林缘、林内海拔梯度变化.通过观测空气温度、湿度、风速、饱和水汽压、净辐射、光合有效辐射等指标的平均值、极大值和极小值, 采用通径分析方法定量化研究气象因素和空气负离子浓度的关系.结果表明: (1) 九龙山林缘地区10月空气负离子浓度平均值比9月的空气负离子浓度高80％;9月的空气负离子浓度日变化整体呈下降趋势, 10月上旬日变化呈单峰曲线型上升趋势, 10月中旬和下旬空气负离子浓度日变化为幂函数曲线型, 整体为下降趋势; (2) 林缘地区空气负离子浓度比林内空气负离子浓度高4％, 林缘地区空气负离子浓度随海拔变化成波浪形, 对应林内空气负离子浓度随着海拔梯度变化成显著单峰型, 变化趋势与林缘地区相反; (3) 在所有气象因素指标中, 通过逐步回归分析提取空气湿度最低值, 饱和水汽压最低值和空气温度最低值进行通径分析, 其直接通径系数分别为1.064, -0.817和0.468.因此空气湿度最低值是影响空气负离子浓度的最大直接因素.空气温度最低值通过空气湿度最低值和饱和水汽压的作用, 成为空气负离子浓度的最大间接影响因素.通过研究林缘地区空气负离子情况并与林内进行对比, 揭示了林缘地区在森林康养规划中的重要性.
