The Quantity Of Soil Microbe And The Relation Between The Quantity And Soil Factor In Chinese Fir Plantation

Chinese fir (Cunninghamia lanceolata (Lamb) Hook) is a fast-growing native Chinese species with valuable timber attributes in subtropical area of southern China. The total area and stocking volume of Chinese Fir plantation have reached 12.39 million hm2 and 473.57 million m3, respectively, accounting for 26.55% and 46.89% of those of plantations in the whole nation. Chinese fir plantation is one of main forest types in southern forest zone and will contribute a great deal to alleviating the huge timber demand from rapid economic growth and assisting national forest conservation at the national level. The soil microorganisms was a driving force of the nutrient transforms, it was playing important role in soil organism transforms, the maintenance soil fertility and soil ecosystem function aspects. The present study tried to determine the distribution of the quantity of soil microorganisms and the relationship between it and soil factors (soil temperature, soil moisture content, soil organic carbon content, soil total N content), monthly variation of litter-fall amount, the decomposition rate of litter-fall and the relation between them and the quantity of soil microorganisms in the second rotation Chinese fir plantation. It is aimed at getting a full picture of the relationship between the quantity of soil microorganisms and environmental factors, so as to provide some theoretical basis for the development of more desirable Chinese fir plantation and sustainable management under the Chinese fir plantation. The main results of the research are as follows:In the same watershed of Chinese fir plantation and Chinese chestnut, the quantity of bacteria holded absolute superiority,0～20 cm soil layers> 20～40 cm soil layers>40-60 cm soil layers. In the different watershed of Chinese fir plantation, hillfoot> hillside> ridge, the quantity of bacteria and the total of microorganisms changed as:spring was higher, summer was minimum, the highest was in autumn, winter and summer keeped balance basically. Fungi reduced according to the law of from spring to winter, and the changes were relatively large. The quantity of actinomycetes followed:spring was comparatively high, summer was most, autumn was lowest, winter was lower. The total of soil microorganisms in Chinese chestnut changed as:spring was highest,summer was lower, autumn was higher, and winter was minimum. The quantity of bacteria, fungi, actinomycetes and the total of microorganisms in Chinese fir plantation were remarkable variant with which in Chinese chestnut(p<0.05).The quantity of bacteria, fungi, actinomycetes and the total of microorganisms were not correlated with the soil temperature of the 10 cm soil depth (p>0.05); The total of microbe was highly remarkable positive linear correlated with soil moisture content (p<0.01), the quantity of bacteria and actinomycetes were also remarkable positive linear correlated with it (p<0.05), while fungi did not correlate (p>0.05);The quantity of bacteria, fungi and the total of microbe were highly remarkable positive linear correlated with soil organic carbon and soil total nitrogen content (p<0.01), and the quantity of actinomycetes showed remarkable positive linear correlated with soil organic carbon and soil total nitrogen content (p<0.05). The contribution ratio of the soil temperature, soil moisture content, soil organic carbon content and soil total nitrogen content to the quantity of soil microorganisms in Chinese fir plantation ranged from 60% to 70%.The annual litter-fall was 1 320.68 kg/hm2 in the Chinese fir plantation, the model of monthly dynamic variety was irregulary, the quantity of needle was most. The monthly amount of litter-fall was positive correlated with the quantity of bacteria and the total of microorganisms, and negatively related to the quantity of fungi and actinomycetes, all of the trends were parabola state. The correlation coefficients ranked as:the quantity of actinomycetes (0.676)> the quantity of bacteria(0.589)> the quantity of fungi(0.514)> the total of microorganisms(0.448).The decomposition rate of needle was obviously quicker than the twig. The decomposition rate of needle was negatively correlated with the soil moisture content, soil organic carbon content and soil total N content, and positive related to the total of microorganisms and the quantity of three kinds of soil microorganisms, all of the trends were parabola state. The decomposition rate of twig was positive parabola correlated with the soil moisture content, soil organic carbon content, soil total N content, the quantity of bacteria, fungi and the total of microorganisms, and negatively parabola related to the quantity of actinomycetes. In the litter-fall decomposition process, the carbon content was basically a release process, while the nitrogen content was not a pure release process, it also contained the concentrate process. The soil environments of Chinese fir plantation showed reciprocal cause-effects relationship with the soil microorganisms. Therefore, environmental enhancement in the Chinese fir plantation not only could improve the soil microorganism services, but also could bring about a favourable cycle to the environment of the Chinese fir plantation in return, so as to diminish the negative ecological effects of Chinese fir plantation establishment.