The gas_well system permanently installed in the soil was adopted for studying the dynamic relationship between CO 2 profiles and seedling root growth of Pinus sylvestris var. sylvestriformis (Takenouchi) Che...The gas_well system permanently installed in the soil was adopted for studying the dynamic relationship between CO 2 profiles and seedling root growth of Pinus sylvestris var. sylvestriformis (Takenouchi) Cheng et C. D. Chu. The study was conducted in the Open Research Station of Changbai Mountain Forest Ecological System, The Chinese Academy of Sciences from 1999 to 2001. Four treatments were arranged in the rectangular open_top chambers (OTCs): ambient CO 2+no_seedling, 700 μmol/mol CO 2+no_seedling, ambient CO 2 +seedlings, 700 μmol/mol CO 2+seedlings. By collecting and analyzing soil gas synchronously, it was found that the dynamics of CO 2 profiles were related to the biological activity of seedlings. There were more roots distributed in the top soil and the boundary layer across soil and sand, which made more contributions to the CO 2 profiles due to respiration root. Compared with the ambient CO 2, elevated CO 2 led to the peak of CO 2 concentration distribution shifted from soil surface layer to the boundary layer as seasonally growing of seedling roots. It is suggested the gas_well system is an inexpensive, non_destructive and relatively sensitive method for study of soil CO 2 concentration profiles.展开更多
Canopy openings have a vital role in forest structure,regeneration,and plant composition.In this study,we investigated and compared the species composition and densities of seedlings and saplings between canopy gaps(o...Canopy openings have a vital role in forest structure,regeneration,and plant composition.In this study,we investigated and compared the species composition and densities of seedlings and saplings between canopy gaps(openings)and forest understories(in dense canopies)in a sub-tropical forest of Bangladesh.We objectively identified 42 canopy openings between transect lines and 42 main plots in dense canopies,sampled for regeneration and young tree patterns.For the regeneration study,we placed 2 m×2 m four subplots in each canopy opening and the main plot of dense canopy,thus making a total of 336 subplots.The species diversity of seedlings,saplings,and trees were significantly(P≤0.05)higher in the dense canopy than in the canopy opening.Although,most dominant and frequent regenerating species such as Diospyros pilosula,Garcinia cowa,Brownlowia elata,and Lithocarpus polystachya were common in both dense canopy and openings,the canopy openings had the highest Importance Value Index,suggesting the significance of gap dynamics in the dominance of native floral species.The dense canopy played an important role in forest compositions because 12 regenerating species,including Stereospermum suaveolens and Diospyros montana,were not found in the canopy openings,implying that rain forests must maintain a high canopy cover for regeneration.展开更多
文摘The gas_well system permanently installed in the soil was adopted for studying the dynamic relationship between CO 2 profiles and seedling root growth of Pinus sylvestris var. sylvestriformis (Takenouchi) Cheng et C. D. Chu. The study was conducted in the Open Research Station of Changbai Mountain Forest Ecological System, The Chinese Academy of Sciences from 1999 to 2001. Four treatments were arranged in the rectangular open_top chambers (OTCs): ambient CO 2+no_seedling, 700 μmol/mol CO 2+no_seedling, ambient CO 2 +seedlings, 700 μmol/mol CO 2+seedlings. By collecting and analyzing soil gas synchronously, it was found that the dynamics of CO 2 profiles were related to the biological activity of seedlings. There were more roots distributed in the top soil and the boundary layer across soil and sand, which made more contributions to the CO 2 profiles due to respiration root. Compared with the ambient CO 2, elevated CO 2 led to the peak of CO 2 concentration distribution shifted from soil surface layer to the boundary layer as seasonally growing of seedling roots. It is suggested the gas_well system is an inexpensive, non_destructive and relatively sensitive method for study of soil CO 2 concentration profiles.
文摘Canopy openings have a vital role in forest structure,regeneration,and plant composition.In this study,we investigated and compared the species composition and densities of seedlings and saplings between canopy gaps(openings)and forest understories(in dense canopies)in a sub-tropical forest of Bangladesh.We objectively identified 42 canopy openings between transect lines and 42 main plots in dense canopies,sampled for regeneration and young tree patterns.For the regeneration study,we placed 2 m×2 m four subplots in each canopy opening and the main plot of dense canopy,thus making a total of 336 subplots.The species diversity of seedlings,saplings,and trees were significantly(P≤0.05)higher in the dense canopy than in the canopy opening.Although,most dominant and frequent regenerating species such as Diospyros pilosula,Garcinia cowa,Brownlowia elata,and Lithocarpus polystachya were common in both dense canopy and openings,the canopy openings had the highest Importance Value Index,suggesting the significance of gap dynamics in the dominance of native floral species.The dense canopy played an important role in forest compositions because 12 regenerating species,including Stereospermum suaveolens and Diospyros montana,were not found in the canopy openings,implying that rain forests must maintain a high canopy cover for regeneration.
