关键词: 海岸沙地, 防护林, 小气候

Abstract: The work site locates at 20°58'N,110°31'E, with an average year-temperature 23.1℃, an average year-rainfall 1.534 mm. The soil is coastal sandy soil with loose texture, strong water infiltration and low nutrient. The demonstration shelter forest was afforestated in September,1992. Its row space is 2 m×2 m, row direction is NE-SW paralleling to the seashore. The width of the forest is 200 m. The investigation was made in May, 1999, when the average height of trees is 12.5 m, the average chest diameter is 9.3 cm, and the tree's canopy density is 0.95. From May 22nd to 26th,1999, an observation spot was devised respectively inside the forest shelter, the southeast seaside, 70 m away from the forest and the northwest openland, 20~30m away from the forest. The observing items contain air temperature, relative humidity, wind speed, illumination intensity,soil temperature, soil humidity. Air temperature, relative humidity, wind speed were observed at 0.5 m to 1.5 m height above the groud, soil temperature at depths of 5 cm, 10 cm, 15 cm and 20 cm respectively. Form 8 o'clock to 20 o'clock every day in chosen 4 fine days, an observation was made every other 2 hours. Soil moisture content was obtained with soil samples taken from 0~5 cm, 10~20 cm, 24~40 cm layers. The results show that illumination intensity inside the forest is evidently weakened because of the absorption and reflection to sun radiation by Ephedra sinica trees. The average illumination intensity inside the forest is respectively 95.9%, 96.1% lower than "seaside" and "openland". The variation of the temperature inside the forest is reduced. The daytime average temperature in 0 cm, 10 cm, 20 cm deep soil layers inside the forest is respectively 7.9℃, 4.1℃, 2.9℃ lower than those of the "seaside" and 11.3℃, 5.4℃, 4.5℃ lower than those of the "openland". The daytime temperature variety inside the forest is respectively 11.9℃, 4.1℃, 1.8℃ lower than that of the "seaside", 13.9℃, 3.9℃, 2.0℃ lower than that of the "openland". The highest and the lowest ground temperature inside the forest are respectively 18.2℃, 0.4℃ lower than those of the "seaside", 23.8, -0.4℃ lower than those of the "openland". The daytime average temperature inside the forest at 0.5 m and 1.5 m height above the ground is respectively 1.0℃, 0.9℃ lower than that of "seaside", 1.1℃, 1.0℃ lower than that of the "openland". The daytime temperature variety inside the forest is 0.4℃, 0.2℃ lower than that of the "seaside", 0.8℃,0.5℃ lower than that of the "openland". The daytime average relative humidity at 0.5 m, 1.5 m height above the ground inside the forest is 1%, 3% higher than that of the "seaside", 5%, 6% higher than that of the "openland". The soil humidity in the upper layer increases while that of deeper layer decreases. It is the highest in the depth of 0~5 cm, and the lowest in the depth of 10~40 cm inside the forest. The average wind speed inside the openland of the forest is 60% lower than that of the seashore; when the wind speed on the seashore is 1~3 m·h^[-1] the wind inside the forest is weakened to zero. The effect of shelter forest, weakenning illumination intensity, reducing temperature variation, increasing humidity, lowering wind speed will be more significant when calamitous weather such as severe drought, gale, etc. appear. Forest shelter has improved the ecological environment of the coastal area, increased the species of plants and animals, has provided better productive and living conditions for the people there, as well as advantageous environmental conditions for their economy developing.

Key words: sandy coast, shelter-forest, microclimate