ON THE RELATIONSHIP BETWEEN THE LAW OF GROWTH OF POPULUS TOMENTOSA CARR.AND THE SOIL CONDITION OF FOREST LAND IN THE PLAIN OF WESTERN SHANDONG PROVINCE

The study was conducted at the Poplar Forest Farm of Guan County,Shandong Province.The result demonstrated the relationship between the law of growth of P.tomentosa and different kinds of soil condition.More knowledge about the bioecological characteristics of P.tomentosa will be of help to get high yield and better cultivation.P.tomentosa is a native tree species in China.It is mainly distributed over the middle and lower reaches of the Yellow River.They are planted in different kinds of soil in the old riverbed of ,the Yellow River in the western part of Shangdong Province.Their growth is closely related with different kinds of soil condition and their increments vary greatly.According to the results in terms of annual increment:its growth in Cinnamonic Chao soil with loam texture that in Chao soil with silt loam texture that in Chao soil with the whole sand texture that in Cinnamonic Chao soil with clay texture that in Wind-sand soil.It's growth in volume in Cinnamonic Chao soil with loam texture is 4 times as much as that in Wind-sand soil.Mature age of P.tomentosa stand in Chao soil with loam texture is 13 years after plantation,but in the other kinds of impoverished soil is from 7-9 years.The fast-growing period may continue for more than 12 years for the Stand in Chao soil with loam texture,while in other kinds of soil,it may continue from 4-9 years.Observations have been made in the fixed plots.The peak growth stage in thickness is obvious,the growth in thickness appears in May every year,making up 40%-60% increase of the total in the whole year.The peak growth in height occurs from June to July every year.The increment of P.tomentosa stand raises with the increase of age of the stand.It grows fast from the second to the tenth year,then slows down gradually.It's increment slows down after 10-14 year.