摘要
通过4～7月对人工杨树林迎风和背风区6倍树高处0.25,0.5,1,2m4个高度风速廓线的观测,定量评价了林地对不同风向及同风向不同风速的生态防护效应,探讨了林地叶面积指数的季节变化对林地生态防风效应的影响。主要结论是:(1)各月可蚀风(风速≥4m/s)的出现频率及风速特征明显不同,4月和5月可蚀风的出现频率及平均风速显著高于6月和7月。(2)各月不同风向的出现频率及风速特征明显不同,4月以SSW、NNW、NW、S、WNW、N和WSW风为主,5月以NW、NNW、W、WSW、WNW和SW风为主,6月以S、SSW、ESE和NNE风为主,7月以SSW、S和SW风为主。(3)杨树林对N、NNE、NE、ENE和NNW风的生态防护效能最好,对NW、E、SW、WSW和W风的防护效能次之,对SE、SSE、S和ESE风的防护效能最差。(4)观测期内林地叶面积指数与0.25,0.5m两个高度的平均风速减弱系数呈显著正相关,其关系可分别用对数和指数函数来描述,而与1,2m两个高度的平均风速减弱系数呈显著非完全正相关,其关系可用三次曲线来描述。
The ecological effect of an artificial poplar (Populus simonii) forest against wind was investigated by monitoring wind speeds at four heights of 0.25, 0.5, 1 and 2 m using fixed observation points placed at distances of 6H (H is mean tree height) from the forest edge of the windward side and 6H from the forest edge of the leeward side over the period from April through July 2001. The relationship between leaf area index in the poplar forest and the attenuation coefficient of wind speed was also examined by curvilinear regression. It was found that: (1) There were marked differences in the frequency of occurrence of erosive winds (wind speed≥4 m/s) among months. The frequency of occurrence of erosive wind was much higher in April and May than in June and July, suggesting that April and May are the major erosive period in the study area. (2) Significantly higher frequency of occurrence was noted in winds of SSW, NNW, NW, S, WNW, N and WSW in April, in winds of NW, NNW, W, WSW, WNW and SW in May, in winds of S, SSW, ESE and NNE in June and in winds of SSW, S and SW in July. (3) The protective effects of the poplar forest were greatest on winds with N,NNE,NE,ENE,NNE and NNW wind directions having the attenuation coefficients of wind speed of 49%~55%,intermediate on winds with NW, E, SW, WSW and W wind directions having the attenuation coefficients of wind speed of 30%~37%, and least on winds with SE,SSE,S and ESE wind directions having the attenuation coefficients of wind speed of 0.1%~12%. (4) The relationship between the leaf area index and the attenuation coefficient of wind speed at 1 m and 2 m heights can be described by a cubic curve, whereas that at 0.5m height can be described by a logarithmic curve and that at 0.25 m height can be described by an exponential curve.
出处
《水土保持学报》
CSCD
北大核心
2003年第2期62-66,共5页
Journal of Soil and Water Conservation
基金
中科院"百人计划"项目
中科院寒区旱区环境与工程研究所知识创新工程项目(210097)
国家"973"项目(G2000048704)
