花蓮七星潭海岸防風林功效之探討

七星潭位於花蓮機場東側，為一新月形海灣，經縣政府劃定為風景特定區，以提供民眾 遊憩所需。為了解七星潭海岸防風林之功效，本研究以多層風速計與微氣候記錄儀觀測林帶 內外風速、鹽份及微氣候之差異；經由研究結果得知，位於防風林帶內67m 處平均減風與減 鹽效果已達70%左右，而至140m 處則可高達約90%；再者，葉片與土壤鹽份量及空中飄鹽 量之分佈，隨水平距離增加而遞減，在150m 處皆已降至10 mg/100ml 以下；至於林帶內平 均氣溫與地溫則較林帶外高約2℃，土壤含水量較林帶外高約0.4%，而氣壓及相對濕度亦有 相同之趨勢，但光照度則僅為林帶外1/215，輻射亦只有1/20；整體而言，由於海岸防風林 帶具有調節微氣候之功效，因此在冬季期間，林帶內感覺溫暖而舒適，對於營造提供優質的 天然遊憩環境有實質助益。Qixingtan is located on the eastern side of Hualien Airport, forming a crescent-shaped bay. It was designated as a Special Scenic Area by the county government to provide recreational spaces for the public. To assess the protective efficacy of the coastal windbreak forest at Qixingtan, this study deployed multi-layer anemometers and microclimate recorders to monitor the differences in wind speed, salt content, and microclimate between inside and outside the forest belt. The results showed that at 67 meters within the windbreak forest belt, the average wind and salt reduction effects reached approximately 70%, while at 140 meters, the effects could be as high as around 90%. Moreover, the salt content in leaves, soil and airborne salt decreased with increasing horizontal distance, dropping below 10 mg/100ml at 150 meters. Additionally, the average air temperature and ground temperature inside the forest belt were approximately 2℃ higher than those outside, and the soil moisture content was about 0.4% higher. Atmospheric pressure and relative humidity exhibited similar trends. However, the illuminance inside the forest belt was only 1/215 of that outside, and the radiation level was just 1/20 of the external value. Overall, as the coastal windbreak forest belt has the function of regulating microclimate, the area inside the forest belt feels warm and comfortable during winter months, which substantially contributes to creating a high-quality natural recreational environment.