哀牢山(西南季风山地)焚风效应的农业意义

AGRICULTURAL SIGNIFICANCE OF THE FOEHN EFFECT IN THE SW MONSOON:A CASE STUDY IN THE AILAO MOUNTAIN

根据哀牢山北段向风(西南)坡与背风(东北)坡共8个测站资料和农业资料,讨论了西南季风翻越哀牢山后的焚风效应——光温增加和水湿减少。这对作物、果树发育有促进作用,对农业有增产效益。当地的农业布局应考虑到焚风效应。

The Ailao Mountain lies in the central Yunnan Province at NNW-SSE direction,being more than 500km long in China. It is a geographical limit between of the longitudinal valley areas in West Yunnan and of the Yunnan-Guizhou Plateau in East Yunnan.8 mountainous meteorological observation stations, were set up in the northern part (24°26′-24°38′N,100°52′-101°08′E) of Ailao Mountain,and the agriculture in the neighbourhood was investigated on the spot.After the SW monsoon flows over the Ailao Mountain,a foehn is bron with both decreases in precipitation and humidity and increases in solar radiation and temperature, on the leeward (NE) slope. Comparing with the windward (SW) slope,the annual precipitation and relative humidity was reduced by ca. 280mm and by ca. 7 %, respectively, on the leeward slope, while there are increases of both ca. 400MJ/m2 in annual total solar radiation and ca. 0. 9℃ in average annual air temperature.The significance of the foehn effect on the mountain agriculture were as follows: 1. the agricultural upper limit altitude was raised by 100-200m,thus it expanded the land-use;2. the sowing and transplanting dates of crops were postponed, while the mature or harvest periods were moved up or shortened,and the crop yields increased clearly;and 3. the increasing yield benefits of agricultural crops variate with the altitude.Considering the agricultural arrangement in the SW monsoon mountain (such as in Ailao Mountain),it should develop forestry as the key on the windward,while take agriculture as the key on the leeward. Meanwhile it is suitable to adopt an agroforestry way on the two slopes aiming at reducing the soil erosion.