Abstract: The ecological effects of shelterbelt network result from its integrated affections on variousmeteorological factors.In semi-arid regions,it can be expressed by evaporation power:Ec=1/2[1.6(10T/I)^a+1.05(e_a-e_d)(1+0.5u)].The calculated regression equation is:Ec=246.52-12.17e+0.58t+6.58u.Because of the shelter effect,the monthly field evaporation in growing season can be reduced by 30—32.5mm maximumly,just equal to having another heavyrainfall compared with open areas.The average monthly reduction is 13.8mm,it's equal tohaving a middle rainfall in sheltered farmland.The best benefited area oceupies two third ofthe total area in networks.The non-or little benefited area occupies only 4—5%.It depends on tree height of shelterbelt and size of network,which can be regulated by rational designing.

Key words: Black soil, Farmyard manure, Microbial biomass P, Growth season, Dynamics