Study on some groups of microorganism during the forest rehabilitation process in Song Ma district, Son La province

Abstract

The paper has made assessement on changes of some soil microorganism groups during the process of forest rehabilitation after shifting cultivation and after clear cutting in Song Ma district, Son La province. Sampling has been made in forest areas naturally regenerated for 4-6; 9-11; 14-16 and above 20 years after shifting cultivation and after clear cutting. The results have shown that the total aerobic bacteria, the total actinomycetes and the total microfungi have increased from the rehabilitation stage of 4-6 years (3.12×10²; 1.23×10³ and 8.05×10² CFU/g respectively in forest areas after shifting cultivation and 4.25×10⁴; 2.32×10³ and 7.32×10³CFU/g respectively in forest areas after clear cutting) to the rehabilitation stage of ≥ 20 years (3.54×10⁵; 2.23×10⁴ and 2.51×10⁴ CFU/g respectively in forest areas after shifting cultivation and 4.35×10⁶; 2.72×10⁵ and 5.46×10⁵ CFU/g respectively in forest areas after clear cutting). The capacity in free nitrogen fixation, in cellulose decomposition, in phosphates decomposition, and in polysaccharide production of the aerobic bacteria, of actinomycetes, and of microfungi is lowest during the first forest rehabilitation stage (4-6 years), then it grows and reaches the highest value during the stage of≥20 years (5.60×10³; 2.75×10⁴; 2.10×10³; 1.36×10⁴ CFU/g respectively in forest areas after shifting cultivation and 5.24×10³; 3.14×10⁵; 4.27×10⁴; 5.39×10⁴ CFU/g respectively in forest areas after clear cutting).