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

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.