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To explore whether the allelopathy of Metasequoia glyptostroboides litter is an obstacle to its natural regeneration, eight concentrations (200, 100, 50, 20, 10, 5, 2, 1 g·L-1 and CK) of aqueous extracts from fresh and natural litter of M. glyptostroboides were set to analyze the allelopathic effects of aqueous extracts of different types and concentrations on seed germination and growth of M. glyptostroboides. The results were as follows:(1)The aqueous extract of the fresh M. glyptostroboides litter had no significant effects on seed germination rate and germination energy (P>0.05), but had significant effects on germination index (P<0.05), and seed germination was significantly inhibited by 1, 100, 200 g·L-1 treatments. The effects of aqueous extracts of the natural M. glyptostroboides litter on three indexes of seed germination were not significant (P>0.05), but the inhibitory effect was reflected in 5, 10, 50, 200 g·L-1. (2)The shoot length, hypocotyl length and main root length of M. glyptostroboides seeds were significantly different between different concentrations of fresh and natural litter aqueous extracts (P<0.05), and decreased gradually with the increase of aqueous extract concentrations (≥10 g·L-1), especially in the range from 50 to 200 g·L-1. (3)Compared with seed germination, the aqueous extracts of fresh and natural M. glyptostroboides litters had stronger inhibitory effect on the growth of seeds after germination, and the allelopathic effect of fresh litter was stronger than that of natural litter. (4)The main root length was the most sensitive to allelochemicals among seeds germination and growth indexes. (5)The dynamic change of shoot length growth of M. glyptostroboides seeds accords with the “S” type growth curve (R²≥0.988). In summary, the litter of M. glyptostroboides has a certain allelopathic inhibitory effect on its own seed germination and growth, which affects the natural regeneration of its population. It is suggested that the litter under the forest should be properly cleaned to promote the natural renewal of the M. glyptostroboides population in the management of M. glyptostroboides populations. [ABSTRACT FROM AUTHOR]

To identify the key factors involved in hindering and effectively promoting the natural regeneration of Metasequoia glyptostroboides, five M. glyptostroboides mother trees in the original wild habitat were selected for this study. The sample circle was set with the M. glyptostroboides mother tree as the center. Different understory treatments (community barrier, understory living ground cover barrier, litter barrier, and non-barrier) were used to conduct the zoning experiment to study the effects of vegetation and litter on the natural regeneration of M. glyptostroboides. Different understory treatments were found to have significant effects on M. glyptostroboides seedling regeneration density, survival rate, height, base diameter, root length, leaf number, leaf area, aboveground biomass, and underground biomass (P＜0.01) . All seedling germination growth indicators reached their maximum values in the non-barrier area, followed by the litter barrier area, understory living ground cover barrier area, and community barrier area. The living ground, litter, and community environment all hindered the natural regeneration of M. glyptostroboides. The order of inhibition on its seed germination and seedling growth was community environment＞living ground＞litter. The dynamic changes in seedling height exhibited the S type growth curve (R~2≥0.893), whereas the seedling regeneration density in all four treatments displayed an inverted "V" shape distribution. The non-barrier treatment significantly promoted the natural regeneration of M. glyptostroboides, under which the survival rate, seedling height, base diameter, root length, leaf number, leaf area, growth rate, and biomass were the highest. Thus, for the conservation and management of M. glyptostroboides populations, the living ground cover and litter should be adequately cleared to provide a suitable environment for seed germination and seedling growth, and promote the natural regeneration of M. glyptostroboides populations in the future. [ABSTRACT FROM AUTHOR]

In order to clarify the regeneration status of Larix principis-rupprechtii forest in Guandi Mountain and explore the influence of environmental factors on its regeneration, the seedlings and saplings of three stands of Larix principis-rupprechtii forest were investigated by a field investigation method and the regeneration density was used to reveal the natural regeneration status. The results were as follows: Larix principis-rupprechtii was poorly regenerated, and seedlings and saplings were scarce. In the 10 square plots of 20 m X 20 m, only 17 seedlings and 44 saplings were found gathered on the edges or gaps of the forest. In contrast, there were 621 seedlings and 630 saplings of Picea spp. in the 10 plots, indicating that it regenerated well. Both altitude and slope did not significantly affect the regeneration of the two tree species. The regeneration of Larix principis-rupprechtii was significantly affected by the slope aspect. The regeneration density on the sunny slope was ( 163 ±51) tree. hm -z, which was higher than that of shady slope with only(77±35) tree.hm-2 . The regeneration density was not significantly different among the three stands. The regeneration of Larix principis-rupprechtii was affected by the canopy density of the stands. The maximum regeneration density was 250 tree. hm-2 in stands with a canopy density of 0. 25, and the regeneration density slightly decreased as the canopy density increased. There was no regeneration when the canopy density exceeded 0.80. The regeneration of Larix principis-rupprechtii was also significantly affected by the thickness of the undecomposed litter layer and the unifonnity of the thickness among the three litter layers. Larix principis-rupprechtii was prone to regenerate on plots with the thickness of each litter layer between 2 -4 cm. Light and litter were the main factors affecting the regeneration of Larix principis-rupprechtii on Guandi Mountain. [ABSTRACT FROM AUTHOR]