Dynamic Changes Of PhytOC Contents In Litter And Living Leaves Of Three Typical Scattered Bamboos And Estimation Of PhytOC Production Flux

Phytolith-occluded organic carbon?PhytOC?is the organic carbon occluded within phytoliths and one of the important mechanisms of long-term carbon sequestration on land.China is a big country of bamboo resources.Both bamboo species resources and bamboo forest area rank the top in the world.Plantation area of scattered bamboo stands accounts for 81%of the total area of bamboo stands in China,which plays an important role in the carbon sink of bamboo forests in the world.In this study,3 typical scattered bamboos?Phyllostachys edulis,Phyllostachys Prominens,and Pleioblastus amarus?were selected as the research object.The litter of the bamboo stands in each month and the living leaves of the Phyllostachys edulis stands in different seasons of the whole year were collected to study dynamic changes of biomass,C and N contents,phytolith contents,organic matter contents in phytoliths,and PhytOC contents in litter and living leaves.The PhytOC sequestration rate in living leaves of different months were compared with that in annual litterfall to determine the optimum sampling time of living leaves for estimating PhytOC sequestration rate of Moso bamboo.The main results of this study are as follow:1)Dynamic changes of C and N contents and C/N in litters of 3 typical scattered bamboos:The C contents in litter of Moso bamboo,Phyllostachys Prominens,and Pleioblastus amarus were 404.1⁴60.65 mg·g^-1,424.47⁴87.25 mg·g^-1,and 404.70⁴68.05 mg·g^-1,respectively;the N contents in litter of Moso bamboo,Phyllostachys Prominens,and Pleioblastus amarus were 9.33¹2.70 mg·g^-1,9.65¹5.80 mg·g^-1,and 9.80¹2.78 mg·g^-1,respectively;the C/N in litter of Moso bamboo,Phyllostachys Prominens,and Pleioblastus amarus were 31.51⁴5.97,27.47⁴7.19,and 32.93⁴5.97,respectively.The annual mean values for C and N contents as well as C/N ratio in litter of different bamboo species were similar.There were significant differences in C and N contents as well as C/N in the litter of 3 typical scattered bamboos among difference month samples?p<0.05?.The C and N contents as well as C/N in the litter of 3 typical scattered bamboos changed with seasonal,and the highest and lowest values were different from the bamboo species.2)Annual returned amounts of C and N elements in litter for 3 typical scattered bamboo stands:Litter biomass of 3 scattered bamboo species decreased in order of Phyllostachys Prominens(2063kg·hm^-2·a^-1)>Moso bamboo(1806 kg·hm^-2·a^-1)>Pleioblastusamarus(1445 kg·hm^-2·a^-1);Annual returned amounts of C elements for 3 typical scattered bamboo stands decreased in order of Phyllostachys Prominens(907 kg·hm^-2·a^-1)>Moso bamboo(763 kg·hm^-2·a^-1)>Pleioblastus amarus(610 kg·hm^-2·a^-1);Annual returned amounts of N elements for 3 typical scattered bamboo stands decreased in order of Phyllostachys Prominens(28.0 kg·hm^-2·a^-1)>Moso bamboo(21.0kg·hm^-2·a^-1)>Pleioblastus amarus(16.8 kg·hm^-2·a^-1).There were significant differences in litter biomass and annual returned amounts of C and N among different bamboo species?p<0.05?.3)Dynamic changes of litter biomass and phytolith contents in litter of 3 typical scattered bamboo stands:The phytolith contents in litter of 3 typical scattered bamboo stands were 67.72¹28.12,47.08⁹9.98,and 23.99¹12.38 g·kg^-1,respectively.The PhytOC contents in litter of 3 typical scattered bamboo stands ranged from 0.63 to 4.27 g·kg^-1.There was a significant difference in the annual mean values of PhytOC contents in the litter of different bamboo species?p<0.05?and deceased in the order of Moso bamboo(3.02 g·kg^-1)>Phyllostachys Prominens(2.02 g·kg^-1)>Pleioblastus amarus(1.89 g·kg^-1).There was a significant difference in the PhytOC contents in the litter of different months for the same bamboo species?p<0.05?.4)Study on the optimal sampling time of living leaves for estimating PhytOC sequestration rate of Moso bamboos:The PhytOC sequestration rates of Moso bamboo(0.035 t-e-CO₂ hm^-2·a^-1)and Phyllostachys Prominens(0.032 t-e-CO₂ hm^-2·a^-1)were significantly higher than that of Pleioblastus amarus(0.025t-e-CO₂ hm^-2·a^-1)?p<0.05?.The contents of phytoliths and PhytOC in living leaves of Moso bamboo were 23.45¹01.07 and 0.73¹.98 g·kg^-1,respectively and there were significant differences?p<0.05?among the contents in the living leaves of different months;The PhytOC sequestration rates of living leaves of Moso bamboos of different months ranged from 0.75 to 7.68 kg·hm^-2·a^-1.There was no difference between the PhytOC sequestration rates in living leaves of Moso bamboos in February or December and that of litter in a whole year.Therefore,February or December can be used as the optimal month of sampling living leaves for estimating the PhytOC sequestration rate of Moso bamboo stands.We concluded that the fertilization management of different bamboo species should be adjusted according to the seasonal changes of the C,N and C/N of the litter.When collecting living leaves of bamboo stands to estimate the PhytOC sequestration rate,we should study the correlation between the PhytOC sequestration rate of leaf samples in every month of a year and the PhytOC sequestration rate of litter.