北京市典型道路防护林滞尘时空分布及其影响因子分析

Spatio-temporal Distribution and Impact Analysis on Dust-retention Effect of Typical Road Protection Forests in Beijing

[目的]研究北京海淀区3种道路防护林(油松林、圆柏林、银杏林)的滞尘能力、林内滞尘的空间分布规律、滞尘作用与气象因子和PM10浓度的相关性。[方法]滞尘量的测定用单位叶干质量滞尘量(mg·g-1)表征叶面滞尘能力。于冬、春、夏、秋4季对3种道路防护林内距道路不同距离处的滞尘量进行连续观测,比较3种道路防护林滞尘能力,分析3种道路防护林滞尘的空间分布特征及降雨等气象因子及PM10浓度与滞尘作用的相关性。[结果](1) 3种道路防护林总体单位滞尘量圆柏林(4. 20±0. 19 mg·g-1)>银杏林(1. 98±0. 07 mg·g-1)>油松林(1. 71±0. 07 mg·g-1);油松和圆柏林的单位滞尘量冬季>春季>秋季>夏季,银杏林的单位滞尘量春季和秋季基本无差异,夏季最低; 3种道路防护林的单位滞尘量在各季节均为圆柏林最高,银杏林次之,油松林最低。(2) 3种道路防护林空间分布的总体特征为:油松和圆柏林的滞尘空间分布均表现为"两端高、中间低",银杏林单位滞尘量林分中间位置略高于两侧;不同季节表现为冬季北侧高,春季南侧高,夏、秋季南北侧差异不显著。(3)降水量对3种道路防护林滞尘作用影响最大,是3种道路防护林滞尘的最主要限制因子,极大风速、气温、相对湿度和PM10浓度对3种道路防护林滞尘均具有不同程度的正的直接作用。[结论]在相同配置模式(5 m×5 m)及林龄(18年)下,林地尺度滞尘量油松林最大、圆柏林次之、银杏林最低。道路防护林迎风一侧往往具有较高滞尘量,可根据盛行风向强化迎风侧的树木配置。降雨是树木滞尘的主要限制因子,冬季和春季降雨少,树木滞尘量较大,可结合人工冲洗措施使其发挥更大滞尘作用。

[Objective]To study the dust-retention ability,spatial distribution characteristics and the relevance with meteorological and PM10 condition in three kinds of road protection forests（ Pinus tabulaeformis forest,Sabina chinensis forest and Ginkgo biloba forest）. [Method] The dust-retention amount was determined by gravimetric method and using dust-retention amount per unit dry weight（ mg·g^-1） to express the leaf dust-retention capacity.From winter to autumn,the three kinds of road protection forests were observed continuously from different distance of the road,and the dust retention ability of these road protection forests was compared. The relevance between dust-retention effect and rainfall,wind speed,relative humidity,PM10 and spatial distribution characteristics of dust retention of three kinds of road protection forests was analyzed too. [Result]（ 1） The dust retention ability among the three tree species was S. chinensis 〉G. biloba 〉P. tabulaeformis,which were 4. 20 ± 0. 19 mg·g^-1,1. 98 ±0. 07 mg·g^-1,1. 71 ± 0. 07 mg·g^-1,respectively. The dust amount of P. tabulaeformis and S. chinensis forest showed a characteristic of winter〉 spring 〉autumn 〉summer; there was no significant difference in the dust amount of G. biloba between spring and autumn,and summer was the lowest season; the dust-retention ability of 3 kinds of road protection forests in four seasons all showed S. chinensis〉 G. biloba 〉P. tabulaeformis.（ 2） The spatial distribution of the 3 kinds of road protection forests are as follows： the spatial distribution of dust in P. tabulaeformis and S. chinensis forest was ＂high at both ends and low in the middle＂,and the middle position of G. biloba forest was slightly higher than the both sides. The spatial distribution of different seasons showed that： north side was higher in winter,south side was higher in spring,and no significant differences in the north and south sides in spring and autumn.（ 3） The precipitation was the most negative factor to dust-retention,while the wind speed,temperature,relative humidity and PM10 had positive direct effect to dust-retention. [Conclusion] Under the same configuration mode（ 5 m × 5 m） and stand age（ 18 years）,Pinus tabulaeformis forest had the largest dust-retention ability,followed with Sabina vulgaris and Ginkgo biloba forest. Winward side always had more dust-retention amount,so configuration of winward trees should be optimized. Precipitation was the most nagative factor to dust-retention,and in winter and spring,which caused more dust-retention amount in winter and spring forest,and artificial rinsing measures could be taken to exert more dust-retention effect.