| Phytoliths also referred to as ‘plantstones’ or ‘plant opal’ are found in many plants speciesbut are particularly prolific in grasses such as bamboo species. It formed in living plants throughsilicification of cell walls, cell lumina or intercellular spaces are amorphous silicon dioxideminerals. The phytolith-occluded carbon (PhytOC) is a substantial component of soil organiccarbon occluded within phytoliths that form as a result of biomineralization within plants and ishighly resistant(for several thousand years) to decomposition in the soil environment,demonstrating the potential of phytoliths in the long-term biogeochemical sequestration ofatmospheric carbon dioxide (CO2).Lei bamboo (Phyllostachy praecox) belongs to the genus of Phyllostachys Bambusoideae andis an excellent bamboo species for producing edible bamboo shoots. It is widely distributed in vastregions of Yangtze River southward due to its good economic benefit and has become a goodmodel of the economic bamboo species in China. Lei bamboo is typical graminaceous plants andone of plant species with the highest contents of phytoliths. Study on the phytoliths in Lei bambooplants has an important significance for measurement and control of carbon sink in the forest soilin China. In the light of this, a experiment study was conducted to (1) investigate spatialdistribution of PhytOC in Lei bamboo ecosystem,(2) explore return dynamic of PhytOC throughbamboo litter, and (3) determine the accumulation characteristics of PhytOC in Lei bamboo standswith long-term intensive cultivation. The main results of this study are as follow:1. Spatial distribution of Phytolith and PhytOC in different organs of Lei bambooThere were significant variations in the Phytolith contents between different organs of Leibamboo plants. Average phytolith contents in the different organs of Lei bamboo plants were inthe following order: bamboo rhizome (34.58g·kg-1)≈bamboo stump (33.28g·kg-1)> leaves(26.03g·kg-1)≈branches (24.77g·kg-1)> culms (3.82g·kg-1). The carbon contents in thePhytolith of the different organs of Lei bamboo plants ranged from2.65%to6.98%, whereas thePhytOC contents in different organs of Lei bamboo ranged from0.12g·kg-1to2.12g·kg-1.ThePhytOC stocks in leaves, branches, culms, bamboo rhizome, and bamboo stump of bamboo plantswith different ages were5.73,3.11,4.16,4.11, and8.70kg·ha-1, respectively, while the PhytOC stock in these five organs accounted for22.2,12.1,16.1,15.9, and33.7%of the total stock in allthe organs of Lei bamboo, respectively. The PhytOC sink in underground parts of Lei bambooaccounted for49.6%of the total one. The PhytOC sink in the0~60cm soil depth (8883kg·ha-1)was the largest one in the whole Lei bamboo ecosystem, which accounting for97.4%of totalstock in Lei bamboo ecosystem. The PhytOC accumulate rate of Lei bamboo ecosystem was277kg·CO2-e·ha-1·yr-1.2. Return dynamic of PhytOC from bamboo leaf litterMonthly leaf litter amounts under Lei bamboo stands ranged from148.1to1311.8kg·ha-1, inwhich the largest litter amount occurred in May. Annually leaf litter amounts under Lei bamboostand was3476.1kg·ha-1. The Phytolith contents in the leaf litter collected from the differentmonths ranged from47.21g·kg-1to101.68g·kg-1, in which the highest Phytolith content in thelitter occurred in April. The carbon contents in the Phytolith of leaf littler collected from thedifferent months ranged from29.4g·kg-1to44.9g·kg-1, whereas The PhytOC contents in the leaflittler collected from the different months ranged from1.8g·kg-1to3.6g·kg-1. Annual returnamount of litter phytolith was292.2±69.1kg·ha-1. Phytolith-occluded carbon accumulate rate byleaf litter was41.45±9.32kg·CO2-e·ha-1·yr-1.3. Accumulation characteristics of PhytOC in Lei bamboo stands with long-term intensivecultivationLei bamboo stand was transformed from paddy field. There were significant differences inthe phytolith contents in the0~20cm and20~40cm of soil depths in Lei bamboo stand withoutwinter mulching between the first five years. The phytolith contents in the0~20cm soil depth inLei bamboo stand with winter mulching markedly increased with increasing mulching ages afterfive years of cultivation (p<0.05). The changes in PhytOC content and sink in the20~40cm ofsoil depth with cultivation were similar to one in phytolith content. The PhytOC sink in the0~40cm soil depth increased by1.58Mg·C·ha-1after20years of mulching, in which86%of totalPhytOC sink coming from mulching materials including bamboo leaves and rice straw. ThePhytOC accumulation rate in the soil under Lei bamboo stand studied was79kg·C·ha-1·yr-1,which was greater than that in the known long term average accumulation rate (24kg·C·ha-1·yr-1)on a global scale. |
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