Comparison Of Environmental Benefits Of Two Landscape Trees Of Towns (Suburbs)

Urban（suburban）landscape forests are an important part of urban forests.In this study,two kinds of landscape forests of Pinus tabulaeformis and Prunus cerasifera cv.Atropurpurea in Caijiapo Town,Baoji City,Shaanxi Province were selected,and a large number of literatures were consulted to conduct field surveys and laboratory experiments.On the basis of this,the research focused on the sulphur content,nitrogen content,dust abatement ability,and anion-releasing ability of two types of landscape forest leaves under clean,lightly polluted and polluted three different pollution conditions,and passed the AHP method.Both of them evaluated the environmental benefits under different pollution conditions,and made reasonable suggestions on the selection and configuration of tree species.The study draws the following conclusions:（1）Changes in sulfur content and nitrogen content of leaves of Pinus tabulaeformis and Prunus cerasifera cv.Atropurpurea under different pollution conditionsUnder the same pollution conditions,the content of sulfur in leaves of Prunus cerasifera cv.Atropurpurea and P.tabulaeformis varied significantly with seasons（P<0.001）.Taking clean conditions as an example,the sulfur content of Prunus cerasifera cv.Atropurpurea leaves varied seasonally:Autumn（0.0921%）)>Spring（0.0735%）Summer>（0.0651%）,the trend of sulfur content in leaves of Pinus tabulaeformis was seasonal:autumn（0.0123%）>spring（0.0058%）>summer（0.0054%）.Under the other pollution conditions,the sulfur content of the two tree species showed the same seasonal trend as the cleaning conditions.Under different pollution conditions,the nitrogen content of the two tree species changed seasonally with the same trend as the sulfur content of the leaves.In the same season,the contents of sulfur in leaves of Prunus cerasifera cv.Atropurpurea and P.tabulaeformis differed significantly with pollution conditions（P<0.05）.Taking spring as an example,the variation trend of sulfur content of Prunus cerasifera cv.Atropurpurea leaves with pollution conditions was:clean area（0.0735%）>Contaminated area（0.0354%）>Light polluted area（0.0277%）.The change trend of P.tabulaeformis and P.purpurea was opposite,which was contaminated area（0.124%）>light polluted area（0.0379%）>clean area（0.0058%）.The seasonal changes of nitrogen content in leaves of the two tree species and the different trends with the pollution conditions are similar to those of the leaves.（2）Changes in the amount of dust held by leaves of Pinus tabulaeformis and Prunus cerasifera cv.Atropurpurea with pollution conditions and seasonsWithout considering seasonal changes and pollution levels,there was a significant difference in the total dust-removing amount of total unit leaf of Pinus tabulaeformis and Prunus cerasifera cv.Atropurpurea（P<0.001）,and the dust-removing capacity of Prunus cerasifera cv.Atropurpurea leaves（1.87±0.05 mg/g）.It is higher than the pine leaf（1.58±0.05 mg/g）.From the seasonal change trend of dust-removing amount of leaves of two tree species,the dust-removing amount of spring leaves of Pinus tabulaeformis was the highest（1.32±0.09 mg/g）,and the dust-removing amount of autumn leaves of purple-leaf plum was the highest（2.42±0.12 mg/g）.（3）Change of PM₁₀ concentration in Pinus tabulaeformis and Prunus cerasifera cv.Atropurpurea forestsIn the same season,the diurnal variations of PM₁₀ concentration in the two kinds of landscape forests under different pollution conditions were significantly different（P<0.05）.For example,in the case of Prunus cerasifera cv.Atropurpurea forests under clean conditions,the highest concentration of PM₁₀ in forest stands appeared at 16:00 pm（38.6 grains/cubic foot）,the lowest value was at 8:00 in the morning（27.6 grains/cubic foot）.The change trend of PM₁₀ concentration in Pinus tabulaeformis forest stands is the same as that of Prunus cerasifera cv.Atropurpurea,but the PM₁₀ concentration in Pinus tabulaeformis forest is higher than that in the whole Prunus cerasifera cv.Atropurpurea forestry.（4）Changes in the concentration of negative ions in Pinus tabulaeformis and Prunus cerasifera cv.Atropurpurea forestsIn the same season,the diurnal variation of air negative ion concentration in Prunus cerasifera cv.Atropurpurea and P.tabulaeformis forests under different pollution conditions was significantly different（P<0.05）.For example,the highest concentration of negative ion concentration in forests appeared at 10:00 a.m.with clean conditions.（1525/cm³）The lowest value was 8:00（986/cm³）in the morning.The trend of negative ion concentration in Pinus tabulaeformis forests was the same as that of Prunus cerasifera cv.Atropurpurea,but the overall concentration was lower than that of Prunus cerasifera cv.Atropurpurea.There was a significant difference in the negative ion concentration in the two tree species with seasonal changes（P<0.05）.The seasonal variation tendency of negative ion concentration in the Prunus cerasifera cv.Atropurpurea was:summer（1162.83/cm³）>autumn（1047.83/cm³）>spring（866.83）./cm³);The concentration of negative ions in Pinus tabulaeformis plantation was similar to that of Prunus cerasifera cv.Atropurpurea,but the concentration of negative ions in Pinus tabulaeformis was lower than that of Prunus cerasifera cv.Atropurpurea.（5）Evaluation of AHP model for environmental benefits of two landscape forestsThe environmental benefit AHP evaluation showed that the highest score was 7.11 points for Prunus cerasifera cv.Atropurpurea and 3.89 points for P.tabulaeformis under polluted conditions,and 6.78 points and 6.22 points for the three conditions.6.67 points.The benefit stability of Pinus tabulaeformis forest is higher than that of Prunus cerasifera cv.Atropurpurea.It is better to choose Prunus cerasifera cv.Atropurpurea as a landscape tree afforestation species in the field of clean conditions,and it is better to use Pinus tabulaeformis as a landscape tree afforestation species under the pollution conditions.