Soil physical and chemical characteristic

soil nutrient contents

soil enzyme activity

soil microbes distribution and forest growth of tree diameter at breast height (DBH)

tree height and single tree volume of continuous cropping poplar plantation

were investigated along Shu river in Ju County in Shandong. Result showed that

with the planting generation increased

tree height

DBH and log volume decreased. By means of multiple comparisons

it was found that the differences among tree height

DBH and log volume of three generations were different

significantly. With the generation increased

soil volume weight increased

while soil pH value decreased

water-holding capacity of capillary and hole degree of capillary have no law. Compaired with the 2nd generation plantation

besides Mn and Fe

all the other mineral elements

such as available N

P

K trace-element Cu and Zn in top soil layer decreased dramatically. Soil urea enzyme

polyphenol oxidase enzyme

peroxide enzyme decreased with the planting generation increased

while the hydrogen enzyme increased. Continuous cropping has a notable effect on the quantity of microbe of poplar population

and with the generation increased

the quantity of the soil bacterium

fungi and actinomyces decreased obviously.