| The phytolith-occluded organic carbon?PhytOC?has been regarded as an important long-term terrestrial carbon fraction and one of the most promising forest soil carbon sinks.It has held the balance in forest soil carbon sink.This study mainly investigated the evolution pattern of PhytOC in typical forest-soil ecosystems and compared the stability of phytoliths extracted from leaves,litters and soils among various forest types in tropics and subtropics,China.The main results of this study were as follows:1.In order to investigate the stability of PhytOC from plants to soil and estimate its storage in the forest ecosystem,variation of the PhytOC content in leaf-litter-soil ecosystem both in subtropics?Phyllostachys pubescens,Pinus massoniana,Cyclobalanopsis glauca,and Cunninghamia lanceolata stands?and in tropics?atica mangachapoi,Musa basjoo,Hevea brasiliensis,and Acacia mangium stands?was studied.The results showed that,among the four types of subtropical forests,the PhytOC contents of leaves,litter and 0-10 cm soil layer were the highest in Pinus massoniana stands(230.24,229.17 and 20.87 g·kg-1)and the lowest in Phyllostachys pubescens stands(30.55,37.37,3.38 g·kg-1),respectively.Besides,the PhytOC contents of 10-30 cm soil layer were the highest in Cyclobalanopsis glauca stands(18.54 g·kg-1),and the lowest in Phyllostachys pubescens stands(2.90 g·kg-1),respectively.For the four tropical forests,the highest and lowest PhytOC in the leaves were obtained from A.mangium stands(377.66 g·kg-1)and Vatica mangachapoi stands(46.83 g·kg-1),respectively,While the highest and lowest contents of PhytOC in the litter were observed in Hevea brasiliensis stands(218.23 g·kg-1)and Musa basjoo stands(27.66 g·kg-1),respectively.Also among the tropical forests,the highest PhytOC contents in the 0-10 cm and 10-30 cm soil layers were observed in A.mangium stands(23.84 and 24.90 g·kg-1),while the lowest values occurred in Musa basjoo stands(3.89 and 3.93 g·kg-1).Compared with 0-10 cm soil layer,the PhytOC contents of the leaves in Cunninghamia lanceolata,Cyclobalanopsis glauca,Pinus massoniana,Phyllostachys pubescens,Hevea brasiliensis,A.Mangium,Musa basjoo,and Vatica mangachapoi stands decreased by 97.4%,94.9%,90.9%,88.9%,95.9%,93.7%,93.3% and 63.7%,respectively.There was no significant difference in PhytOC contents between leaves and litter for the following five forest types?Phyllostachys pubescens,Pinus massoniana,Cunninghamia lanceolata,Vatica mangachapoi and Hevea brasiliensis stands?.However,PhytOC contents in leaves were significantly higher than that in litters in Cyclobalanopsis glauca,Musa basjoo,and A.mangium stands.The finding that significantly lower Phyt OC contents in soils than those in fresh leaves and leaf litter among eight types of forests suggested that phytolith was not stable during the pathway from plants to soil via the forest litter.2.The phytoliths in leaves,litter,and soils of Phyllostachys pubescens stands in north subtropicas,Bambusa textilis McClure stands in south subtropics,and Musa basjoo stands in tropics was extracted to study the stability of phytoliths in plants and soils among various forests.The study showed that phytoliths was extremely unstable under alkaline conditions.Each type of phytoliths had different solubility.Besides,there was some variation of stability of phytoliths extracted from leaves and litters among different forest types.Specifically,stability of phytoliths in litters of Phyllostachys pubescens stands was higher than that in leaves,whereas the stability of phytoliths in litters of Bambusa textilis McClure stands was higher than that in litters.Stability of phytoliths in leaves and litters of Musa basjoo stands was much higher than that in litters of Phyllostachys pubescens and Bambusa textilis McClure stands.The phytoliths in the soil was more stable than that in leaves and litters under the same forest type.The phytoliths of soils had strong stability in carbon sequestration and its stability in these three different forest types was in the following order: Bambusa textilis Mc Clure stands >>Musa basjoo stands > Phyllostachys pubescens stands. |
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