The Effects Of Allelochemicals Of Chinese-fir Leaf Litter Treated By Different Nitrogen Sources On Chinese-fir Seed In Different Decomposition Stages

Chinese fir, one of the most important fast-growing timber species in southern China, has the largest plantation area and growing stock among all timber species in China. Continuously plantation of Chinese fir has been shown to lead to soil degradation, which has serious impacts on the sustainable management of Chinese fir plantation and base construction of fast growing fir forest. Many studies indicated that a major factor for these consequences is the self-poisoning effects of Chinese fir. In this study, by treating with different nitrogen sources and different levels of nitrogen, we evaluated the effects on Chinese fir seed germination by polar and litter-polar allelochemicals that were produced in different decomposition stages of Chinese fir leaf litter. Our results show that:1,By treating with ammoniacal nitrogen, the litter-polar allelochemicals of different decomposition stages of Chinese fir leaf litter have different allelopathic effects on seed germination. With treatment of different levels of ammoniacal nitrogen, we found that:after 3 months of decomposition, the litter-polar allelochemicals of Chinese fir leaf litter that was treated with 50g NH4Cl have stronger inhibitory effects on all seed germination indexes than that with 100g NH4Cl; after 6 to 9 months of decomposition, the litter-polar allelochemicals of Chinese fir leaf litter that was treated with 50g NH4Cl have stronger inhibition effects than by 100g NH4Cl on seed radicle length, hypocotyl length, fresh weight and dry weight, but have stronger promotion effects on absolute seed germination rate and absolute performance. By treating with different concentration of allelochemicals, we observed a basically positive correlation between the concentration of allelochemicals and their inhibitory effect on seed germination rates.2,By treating with ammoniacal nitrogen, the polar allelochemicals of different decomposition stages of Chinese fir leaf litter have different allelopathic effects on seed germination. With treatment of different levels of of ammoniacal nitrogen, we found that:after 3 months of decomposition, the polar allelochemicals of Chinese fir leaf litter that was treated with 100g NH4C1 have stronger inhibitory effects on all seed germination indexes than that with 50g NH4Cl;after 6 months of decomposition, the polar allelochemicals of Chinese fir leaf litter that was treated with 50g NH4C1 have stronger inhibitory effects than by 100g NH4Cl on seed hypocotyl length, fresh weight and dry weight, but have stronger promotion effects on absolute seed germination percentage and radicle length; after 9 months of decomposition, the polar allelochemicals of Chinese fir leaf litter that was treated with 50g NH4Cl have stronger inhibitory effects on all seed germination indexes than that with 100g NH4Cl. By treating with different concentration of allelochemicals, we observed a basically positive correlation between the concentration of allelochemicals and their inhibitory effect on seed germination rates.3,By treating with nitric nitrogen, the litter-polar allelochemicals of different decomposition stages of Chinese fir leaf litter have different allelopathic effects on seed germination. With treatment of different levels of nitric nitrogen, we found that:after 3 months of decomposition, the litter-polar allelochemicals of Chinese fir leaf litter that was treated with 50g NaNO3 have stronger inhibitory effects on seed germination percentage and radicle length than that with 100g NaNO3 but have stronger promotion effects seed germination rate, hypocoty1 length, fresh weight and dry weight; after 6 to 9 months of decomposition, the litter-polar allelochemicals of Chinese fir leaf litter that was treated with 50g NaN03 have stronger promotion effects than by 100g NaNO3 on all seed germination indexes. By treating with different concentration of allelochemicals, we observed a positive correlation between the concentration of allelochemicals and their inhibitory effect on seed germination with different treatment of nitric nitrogen.4,By treating with nitric nitrogen, the polar allelochemicals of different decomposition stages of Chinese fir leaf litter have different allelopathic effects on seed germination. With treatment of different levels of nitric nitrogen, we found that:after 3 months of decomposition, the polar allelochemicals of Chinese fir leaf litter that was treated with 50g NaNO3 have stronger inhibitory effects on hypocotyl length, fresh weight and dry weight than that with 100g NaNO3, but have stronger promotion effects on seed germination rates,germination performance and radicle length; after 6 to 9 months of decomposition, the polar allelochemicals of Chinese fir leaf litter that was treated with 50g NaNO3 have stronger inhibition effects than by 100g NaNO3 on fresh weight and dry weight, but have stronger promotion effects on absolute seed germination rate, absolute performance, seed radicle length and hypocotyl length. By treating with different concentration of allelochemicals, we observed a basically positive correlation between the concentration of allelochemicals and their inhibitory effect on seed germination rates with different treatment of nitric nitrogen.