Allelopathic Effects Of Allelochemicals In Cunninghamia Lanceolata Root And Humus Soil On Its Seed Germination Under Different Decomposed Stage

Cunninghamia lanceolata (Lamb.) Hook. is one of the most important timber tree species in south China and widely cultivated. The self-allelopathy is one of the most important reasons for soil degradation and productivity reduction of Cunninghamia lanceolata repeated plantation. The field investigation suggested that Cunninghamia lanceolata had poor establishment and low productivity, and would lead soil degradation when is there some professornal terms for this. Decomposition in plant residues is one of the major sources of Allelochemicals. In the role of soil microorganisms, Allelochemicals of different types and contents in litters and plant residues are gradually released into the environment, which had been reported in Cunninghamia lanceolata stumps and litters. However, the type and content of allelochemicals are different among organs in Plants. Follow-up studies had been conducted on allelochemic effects of allelochemicals in Cunninghamia lanceolata roots and humus soil on its seed germination in different stages of decomposition to investigate the toxic effects of self-fir Dynamics. Thus, the self-allelopathy of Cunninghamia lanceolata would be studied for more in-depth research. The main study results were as follows:1) Residue rate of Cunninghamia lanceolata root declined with the decomposition time increased, and weight loss rate performed the opposite trend. Cobb-Douglas model was used to fit the relationship between residual rate of Cunninghamia lanceolata root and the decomposition time. The model showed that: y=99.8757t-0.0650.2) Weight of allelochemicals in Cunninghamia lanceolata root and humus soil gradually reduced in Medium-term decomposition, and rebounded slightly in Latter decomposition. Weight of allelochemicals in Cunninghamia lanceolata root dropped more greatly after 9 months′decomposition than 6 months, and the humus showed the opposite trend.3) Decomposition for 3 months, the result showed that litter-polar allelochemicals of Cunninghamia lanceolata root had positive effect on all of the indexes of its seed germination; the polar allelochemicals of Cunninghamia lanceolata root had inhibitory effect on absolute germination rate, radical length, plumular axis length and dry weight, but had positive effect on absolute germination potential and fresh weight. The litter-polar allelochemicals of Cunninghamia lanceolata humus soil had "Low to promote high-suppression" effect on all of the indexes of Cunninghamia lanceolata seed germination except absolute germination rate; and the polar allelochemicals of Cunninghamia lanceolata humus soil had inhibitory effect on absolute germination rate, radical length and dry weight absolute germination potential, and had "Low to promote high-suppression" effect on absolute germination potential, plumular axis length and fresh weight.4) Decomposition for 6 months, the result showed that litter-polar allelochemicals of Cunninghamia lanceolata root had inhibitory effect on absolute germination potential, plumular axis length and fresh weight, but had positive effect on radical length, had "Promoting high-low-suppression" effect on absolute germination rate; that polar allelochemicals of Cunninghamia lanceolata root had inhibitory effect on absolute germination potential and positive effect on plumular axis length, had "Low to promote high-suppression" effect on absolute germination rate and dry weight, had inhibitory effect on radical length and frest weight of 100mg/L control, and no significant efeect of other control. The litter-polar allelochemicals of Cunninghamia lanceolata humus soil had "Low to promote high-suppression" effect on absolute germination potential, fresh weight and dry weight, had positive on absolute germination rate, radical length and plumular length.5) Decomposition for 9 months, the polar allelochemicals of Cunninghamia lanceolata root and humus soil had inhibitory effect on all of the indexes of Cunninghamia lanceolata seed germination; the little-polar allelochemicals of Cunninghamia lanceolata root performed inhibitory impact on plumular axis length, fresh weight and dry weight; and showed a "Low to promote high-inhibition" action on the absolute germination rate, absolute germination potential and radical length. The little-polar allelochemicals of humus soil had positive effect on absolute germination rate, radical length, plumular axis length and frest weight, showed a "Low to promote high-inhibition" action on other indexs.6) Decomposition for 12 months, the little-polar allelochemicals of Cunninghamia lanceolata root showed a "Low to promote high-inhibition" action to the absolute germination potential and fresh weight, showed a "Low to inhibit high-promotion" action to the radical length and dry weight, and obvious inhibited effect on plumular axis lenght. The polar allelochemicals inhabited the absolute germination potential but promoted the radical length and dry weight, and showed a "Low to promote high-inhibition" action to the absolute germination rate, plumular axis length and fresh weight. The little-polar allelochemicals of humus soil inhibited the absolute germination potential and radical length obviously, showed a "Low to promote high-inhibition" action to the absolute germination rate and plumular axis length, showed a "Low to inhibit high-promotion" effect on fresh weight and had the strong inhibitory effect on dry weight of 100mg/L control. The polar allelochemicals appeared to be inhibited at the absolute germination rate and absolute germination potential, performed slight stimulatory impact on radical length, and showed a "Low to promote high-inhibition" action to the dry weight.7) In the dynamic of whole year, the effect of the Cunninghamia lanceolata root of the little-polar allelochemicals on seed germination when Cunninghamia lanceolata decomposition for 3 months and 9 months were mostly promotive, and almost inhibitive for 6 months and 12 months were. The polar allelochemicals were acted as inhibitory effect. Decomposition for 3 months to 9 months, in the humus soil, the promotive effect of little-polar allelochemicals on seed germination of Cunninghamia lanceolata was gradually getting stronger. But after decomposition for 12 months, the effect was changed into Inhibitory. After decomposition for 3 months to 9 months, the inhibitive effect of polar allelochemicals was getting stronger and changed into promotion after decomposition for 12 months. Overall, during the medium-term of decomposition, (after decomposition for 6 and 9 months) the effect of allelochemicals is stronger than the initial and terminal stage. Cunninghamia lanceolata root and humus soil polar allelochemicals on seed germination of the inhibitory effect is stronger than the little-polar Allelochemicals.