Spatial Heterogeneity Of Phytolith-occluded Organic Carbon For Typical Dendrocalamus Latiflorus Munro

As phytolith features super tolerance to high temperature,oxidation and decomposition,the organic carbon occluded inside the phytolith shell may exist and accumulate in soils and sediments for thousands of years and is hence named as Phytolith occluded organic carbon(PhytOC),which is,therefore,regarded as an important soil organic carbon pool,and contributes significantly to the carbon sink in the soil and global CO2 balance.Forest ecosystem is a mainstay of the terrestrial ecosystem.However,the area of forests on the globe is shrinking drastically today,while the area of bamboo groves is still on a rising trend.So bamboo groves are a growing carbon sink and playing a critical role in carbon cycling in the terrestrial ecosystem.So carbon storage in bamboo forest soils plays a key role in the carbon cycle of terrestrial ecosystem.As Dendrocalamus latiflorus Munro grows very fast and features large volumes of biomass,well-developed root system and outstanding ecological functions,it is favored to be one of the bamboo species extensively cultivated in South China.Nanjing County is known as “Land of Dendrocalamus latiflorus Munro in China” and one of the largest Dendrocalamus latiflorus Munro cultivation region in Fujian Province.In this paper an attempt was made to explore characteristics of the spatial distribution of PhytOC in the soil under the bamboo groves by using Geostatistic combined with GIS technologies,aiming at providing some scientific basis for assessing the pool of PhytOC in the bamboo ecosystems of China.The main results and conclusions are as follows:(1)The average contents of PhytOC in the soil layers varied from 0.30 ~0.75 g·kg-1 in Dendrocalamus latiflorus Munro stands of Nanjing County.The variation coefficients ranged from 80.38 to 87.46% which indicating a moderate degree of variability.Geostatistical analysis revealed that PhytOC contents in 10-30,60-100,and 0-100 cm soil layers fitted the Gauss model;PhytOC contents in 10-30,60-100,and 0-100 cm soil layers fitted the exponential model;the PhytOC contents in 30~60 cm fitted the spherical model.Their Nugget /Sill ratio values varied from 8.7-74.9%,displaying moderate spatial correlation.Moreover their MS/RMSS ratio values were very small which indicating fitting degree of the models was very good.(2)The average storages of PhytOC in 0-100 cm soil layer was 4.23 t·hm-2 under Dendrocalamus latiflorus Munro frorests which were significantly higher than that under Chinese fir forest,Masson pine forest,broadleaf forest,and mixed conifer-broadleaf forest.There were significant differences in the average storages of PhytOC among the sample points,and the minimum value is only 4.85% of the maximum.The variation coefficients of the average storages of PhytOC in different soil layer ranged from 0.83 to 0.96,which indicating a moderate degree of variability.(3)The contents of SOC,phytoliths and PhytOC in the soils in different areas decreased with soil depths.The ratio of PhytOC/SOC in the soils is an important indicator to characterize long-term carbon sequestration mechanism in the soils.The ratios of PhytOC/SOC in the soils increased significantly with soil depth,which was mainly attributed to that the decrease rates of organic carbon were greater than that PhytOC in the soil with the increase of soil depth.(4)The spatial distribution of total silicon,phytolith,and PhytOC contents in the soils were almost similar.There was positive significant positive correlations(P<0.01)among them.In addition,there was a significant positive correlation between PhytOC contents and bamboo age(P<0.05),whereas a significant negative correlation was found between altitude and PhytOC contents(P<0.05)which suggests that the bamboo forest age and altitude were the main factors influencing the PhytOC contents.