Allelopathy Of Chinese Fir Stump By Bioassay In Diferent Decomposition Stage

Chinese fir,recommended as one of the most important planting tree species in southern China,but most of which them grew on continuous plantation land.The long-term forestry production practice indicated that Chinese-fir continuous plantation caused soil degeneration and productivity declining,which had become more and more evident along with the increasing times of pure plantation cultivation.Chinese fir continuous planting obstacle was one of the most important reasons of the sustainable development of Chinese fir stand.Many scholars had researched Mechanism of soil degeneration of Chinese fir forestry from different factors,such as biology characteristic,cultivation system,but Lin Sizu ect.discovered that the autointoxication was one of the key factors accounting for continuous planting obstacle.So far,autointoxication has achieved fruitful results,mainly researched autointoxication effect at a certain point time,but allelochemicals of plant residues and litter were gradually released to the environment under the effect of soil microbe,which was a dynamic process,and in different decomposition stage,the kinds of allelochemicals were different.Therefore,the allelopathy of Chinese fir stump had been mensurated unceasing by bioassay in different decomposition process,in expectation of the provision of theoretic basis for settling Chinese fir continuous planting obstacle.The results of the experiment were followed:1.In the experiments of Chinese fir stump decomposition,the residual rate of Chinese fir stump gradually decreased,the weightless rates of Chinese fir stump gradually increased along with decomposed for one year,2.The weight of allelochemicals extracted from Chinese fir stump gradually decreased from decomposed for 3 monthes to decomposed for 9 monthes,The weight of allelochemicals decomposed for 6 monthes decreased 43.89%compaired with that of decomposed for 3 monthes,which decomposed for 9 monthes decreased 48.44%compared with that of decomposed for 6 monthes.However,when decomposed for 12 monthes,the weight of allelochemicals increased 24.51%compared with that of decomposed for 9 monthes.3.Allelochemicals extracted from Chinese fir stump had different allelopathic effects on Chinese fir seeds germinated indexes,as far as three concentrations(50 mg·L^-1,100 mg·L^-1和200 mg·L^-1),in general the low concentration had positive effects and the high concentration had inhabited effects.4.In the process of Chinese fir stump decomposition,from decomposed for 3 months to 9 months,the trend of positive effect of allelochemicals extracted from Chinese fir stump increased with the decomposition proplong,when decomposed for 9 months,the positive effect of allelochemicals was the strongest,but when decomposed for 12 months,the positive effect reduced or transfered inhibited effect.5.After decomposed for 3 months,the litter-polar allelochemicals extracted from Chinese fir stump had positive effects on plumular axis length in the low concentration,and had inhibited effects on absolute germination rate,absolute germination power,plumular root length,fresh weight and dry weight.The polar allelochemicals had positive effects on plumular axis length,and which had positive effects on plumular root length and fresh weight in the low concentration,and in the high concentration which had positive effects on absolute germination rate.After decomposed for 6 months,the litter-polar allelochemicals extracted from Chinese fir stump had positive effects on plumular axis length and plumular root length, and the polar allelochemicals had positive effects on plumular root length in the low concentration,and the litter-polar and polar allelochemicals had inhibited effects on other indexes.After decomposed for 9 months,the litter-polar and polar allelochemicals had positive effects on all the germination indexes of Chinese fir seeds.After decomposed for 12 months,the litter-polar and polar allelochemicals had obviously inhibited effects,the litter-polar allelochemicals only had positive effects on absolute germination rate in the concentration of 50 mg·L^-1and 100 mg·L^-1,but the polar allelochemicals had positive effects on absolute germination rate,absolute germination rate and dry weight in the concentration of 50 mg·L^-1.