Abstract
Phytolith-occluded carbon (PhytOC) can be preserved in soils or sediments for thousands of years and might be a promising potential mechanism for long-term terrestrial carbon (C) sequestration. As the principal pathway for the return of organic matters to soils, the forest litter layers make a considerable contribution to terrestrial C sequestration. Although previous studies have estimated the phytolith production fluxes in the above-ground vegetations of various terrestrial ecosystems, the storages of phytoliths and PhytOC in litter layers have not been thoroughly investigated, especially in forest ecosystems. Using analytical data of silica, phytoliths, return fluxes and storages of forest litter, this study estimated the phytolith and PhytOC storages in litter layers in different forest types in southern China. The results indicated that the total phytolith storage in forest litter layers in southern China was 24.34 ± 8.72 Tg. Among the different forest types, the phytolith storage in bamboo forest litter layers (15.40 ± 3.40 Tg) was much higher than that in other forests. At the same time, the total PhytOC storage reached up to 2.68 ± 0.96 Tg CO2 in forest litter layers in southern China, of which approximately 60% was contributed by bamboo forest litter layers. Based on the current litter turnover time of different forest types in southern China, a total of 1.01 ± 0.32 Tg of PhytOC per year would be released into soil profiles as a stable C pool during litter decomposition, which would make an important contribution to the global terrestrial long-term biogeochemical C sink. Therefore, the important role of PhytOC storage in forest litter layers should be taken into account in evaluating long-term forest C budgets.
Highlights
Global warming, as one of the major challenges facing human survival and development, is mainly caused by the rapid increases in greenhouse gas (e.g., CO2) concentrations in the atmosphere (IPCC, 2013; Fang et al, 2018)
Assuming the median concentration of 3% C occluded during the formation of the phytoliths, the total Phytolith-occluded carbon (PhytOC) storage could reach up to 2.68 ± 0.96 Tg CO2 in forest litter layers in southern China, approximately 60% of which was contributed by bamboo forest litter layer but which occupied only 9.5% of the forest area in this region (Figures 2, 3)
In this study we mainly estimated the sizes of PhytOC storages in the litter layers of different forest types in southern China
Summary
As one of the major challenges facing human survival and development, is mainly caused by the rapid increases in greenhouse gas (e.g., CO2) concentrations in the atmosphere (IPCC, 2013; Fang et al, 2018). One of the most promising mechanisms of terrestrial biogeochemical C sequestration is C occlusion within phytoliths (phytolith-occluded carbon, PhytOC), which has drawn the attention of many researchers (Parr and Sullivan, 2005; Zuo and Lü, 2011; Song et al, 2012b; Li et al, 2013). Compared with nanostructures of silica bodies, the size of phytoliths mainly ranges from 5 to 250 μm and phytolith morphotypes generally vary with plant species, which makes them more stable due to their microscale internal cavities (Piperno, 1988; Strömberg, 2004; Lu et al, 2007; Song et al, 2016). As phytoliths consist mainly (66–91%) of silica (SiO2) and show a positive correlation with Si content in plant (Li B.L. et al, 2014), the phytolith content can be estimated directly or indirectly from plant Si content (Hodson et al, 2008; Parr et al, 2010; Song et al, 2012a, 2013; Anala and Nambisan, 2015)
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