Study Of The Effect Of Different Tree Species On The Negative Effect Of Farmland Shelterbelts

In order to analyze the effect of different tree species on the negative effect of farmland shelterbelts and relationship between shelterbelts and different crops,we select these Shelterbelts located in Gannan County,Qiqihaer City,Heilongjiang Province,which can be the western Shelterbelts' representative,as trial field.These Shelterbelts in question including:4 lines Populus simonii×P.nigra shelterbelts,4 lines Larix gmelinii shelterbelts,single line Pinus sylvestris L.var.mongolica Litv shelterbelts.Using high of trees(H) for determine the location of the measuring point within Zea mays L.,Helianthus annuus,Glycine max L.plots within the scope of protection of each shelterbelts,for indicators of soil nutrients and physiological indicators.And 25H away from shelterbelt as the control points.Analysis of the effect of different tree species on the negative effect of farmland shelterbelt and relationship between shelterbelts and different crops shows that:In these three types of shelterbelts,obvious regular changes in soil moisture and in physiological indicators of Zea mays L.,Helianthus annuus,Glycine max L.do exist.While conventional indicators of soil nutrients had no significant changes.The actual threat on agricultural production and the phenomenon kowned as negative effect is mainly due to competition between shelterbelts and crop root for soil moisture instead of soil nutrients.When compare the change of the soil moisture depanded on distance from three shelterbelts,respective.we find:Populus simonii×P.nigra has the most negative effect on the soil moisture of Glycine max L,Larix gmelinii has the least.Populus simonii×P.nigra has the most negative effect on the soil moisture of Zea mays L.,Larix gmelinii has the least.Pinus sylvestris L.var.mongolica Litv has the most negative effect on the soil moisture of Helianthus annuus,Larix gmelinii has the least.This study of the 4 line Populus simonii×P.nigra shelterbelts shows they can makes a more serious threat than other two,the scope of negative effect up to 1.6H,within the scope of negative effect,the photosynthetical indicators of Glycine max L.is better than the photosynthetical indicators of Helianthus annuus,and the photosynthetical indicators of Helianthus annuus is better than the photosynthetical indicators of Zea mays L.Outside the scope of the negative effect the photosynthetical indicators of Glycine max L.is slightly better than the photosynthetical indicators of Zea mays L.,the photosynthetical indicators of Zea mays L.is better than photosynthetical indicators of Glycine max L.This study of the 4 line Larix gmelinii shelterbelts shows that:the scope of negative effect up about 0.8H.Within the scope of negative effect,photosynthetical indicators of Zea mays L. slightly better than Glycine max L.and Glycine max L.,Outside the scope of the negative effect,the three are similar in photosynthetical indicators.This study of single line Pinus sylvestris L.var.mongolica Litv shelterbelts shows that:the scope of negative effect up about 0.8H.Within the scope of negative effect.The three are similar in photosynthetical physiology,and outside the scope of the negative effect,the photosynthetic physiological indicators of Zea mays L.is the best of the three,and the photosynthetic physiological indicators of Glycine max L.is the wrost of the three.When compare the change of the photosynthetic indicators,depanded on distance from three shelterbelts,respective.Populus simonii×P.nigra has the most negative effect on photosynthetic indicators of Zea mays L.,Larix gmelinii has the least.Populus simonii×P.nigra has the most negative effect on photosynthetic indicators of Helianthus annuus,Pinus sylvestris L.var.mongolica Litv has the least.The three are similar in their negative effect on the photosynthetical indicators of Glycine max L.