中国亚热带5种林分凋落物层植硅体碳的封存特性

Phytolith-Occluded Carbon in Litters of Different Stands in the Subtropics of China

【目的】森林生态系统的植硅体碳是一种长期（数千年）封存的土壤有机碳,对全球固碳有重要意义。本研究旨在估测中国亚热带森林凋落物层的植硅体碳贮量。【方法】以中国亚热带5种常见林分类型（毛竹林、杉木林、马尾松林、阔叶林和针阔混交林）的凋落物为研究对象,收集地表凋落物并采集0-10 cm土层土样,用微波消解法提取凋落物及土壤中的植硅体,并测定植硅体中的碳含量。【结果】不同森林凋落物Si O2含量表现为毛竹林（152.50 g·kg^-1）〉阔叶林（13.96 g·kg^-1）〉针阔混交林（12.55 g·kg^-1）〉杉木林（7.62 g·kg^-1）〉马尾松林（6.59 g·kg^-1）;凋落物植硅体含量表现为毛竹林（180.20 g·kg^-1）〉阔叶林（14.67 g·kg^-1）〉针阔混交林（11.49 g·kg^-1）〉马尾松林（11.36 g·kg^-1）〉杉木林（5.58 g·kg^-1）;凋落物中植硅体碳含量表现为毛竹林（4.34 g·kg^-1）〉阔叶林（1.07 g·kg^-1）〉针阔混交林（1.04 g·kg^-1）〉马尾松林（0.67 g·kg^-1）〉杉木林（0.50 g·kg^-1）;凋落物现存生物量表现为阔叶林（3.20 kg·m^-2）〉马尾松林（2.51 kg·m^-2）〉针阔混交林（2.38kg·m^-2）〉杉木林（1.88 kg·m^-2）〉毛竹林（1.45 kg·m^-2）;5种林分凋落物中的Si O2含量与植硅体含量极显著正相关（R2=0.940 5,P〈0.01）;植硅体含量与植硅体碳含量（R2=0.950 0,P〈0.01）以及植硅体碳中有机碳含量与凋落物中植硅体碳含量（R2=0.7018,P〈0.01）均极显著相关;毛竹林、杉木林、马尾松林、阔叶林和针阔混交林凋落物层中的植硅体碳贮量分别为0.231,0.034,0.062,0.125和0.090 tCO2·hm^-2;毛竹林、杉木林、马尾松林、阔叶林和针阔混交林0-10 cm土层的植硅体碳贮量分别为0.492,0.217,0.352,0.362和0.448tCO2·hm^-2。【结论】5种林分均能通过凋落物植硅体将植硅体碳封存到土壤中;毛竹林凋落物中植硅体碳含量、凋落物和土壤的植硅体碳贮量在5种林分中都表现为最高;若以中国亚热带毛竹林年凋落物量3.6 t·hm^-2a^-1计算,毛竹林凋落物的植硅体碳封存速率为0.057 tCO2·hm^-2a^-1。本研究得到的中国亚热带中5种林分凋落物的植硅体碳贮量数据为进一步评价中国亚热带森林生态系统植硅体碳封存潜力提供科学依据。

【Objective 】 Phytolith-occluded organic carbon（ Phyt OC） in forest ecosystem is a long-term（ decades to millennia） mechanism for sequestrating soil organic carbon and has a vital significance to the global carbon sequestration. This study aims to estimate Phyt OC stocks in the forest litter layer under China＇s subtropical forests. 【Method】Liters of 5 common types of China＇s subtropical stands were studied,by collecting litters under forests and samples of 0 - 10 cm of topsoil.Furthermore,we calculated current litter biomass and determined soil density. The phytolith in the litter and soils were extracted by microwave digestion method,and the phytolith occluded carbon（ Phyt OC） content in the litter and soils were determined.【Result】The Si O2 contents in the litter under different stands were in the following order： Moso bamboo（ Phyllostachys edulis）（ 152.50 g·kg^-1）〉 broad leaved（ 13. 96 g·kg^-1） 〉mixed coniferous and broad-leaved（ 12. 55 g·kg^-1）〉 Chinese fir（ Cunninghamia lanceolata）（ 7. 62 g·kg^-1） 〉Masson pine（ Pinus massoniana）（ 6. 59 g·kg^-1）. The phytolith contents in the litters under different forests were in the following order： Moso bamboo（ 180. 20 g·kg^-1）〉 broad leaved（ 14. 67g·kg^-1） 〉mixed coniferous and broad-leaved（ 11. 49 g·kg^-1）〉 Masson pine（ 11. 36 g·kg^-1）〉 Chinese fir（ 5. 58 g·kg^-1）. The Phyt OC contents in the litters under different stands were in the following order ： Moso bamboo（ 4. 34 g·kg^-1） 〉broad leaved（ 1. 07 g·kg^-1） 〉mixed coniferous and broad-leaved（ 1. 04 g·kg^-1）〉 Masson pine（ 0. 67 g·kg^-1） 〉Chinese fir（ 0. 50 g·kg^-1）. The current litter biomass under 5 stand types was in the following order：broad leaved（ 3. 20 kg·m^-2）〉 Masson pine（ 2. 51kg·m^-2）〉 mixed coniferous and broad-leaved（ 2. 38 kg·m^-2） 〉Chinese fir（ 1. 88 kg·m^-2）〉 Moso bamboo（ 1. 45 kg·m^-2）. There were strong linear relationships between Si O2 contents and phytolith contents in the litter under different forest types（ R2= 0. 940 5,P〈0. 01）,phytolith contents and Phyt OC contents in the litters under 5 stands（ R2= 0. 950 0,P〈0. 01） as well as occluded carbon contents in phytolith and Phyt OC contents in the litters under 5 stand types（ R2= 0. 701 8,P〈0. 01）. The Phyt OC stocks in the litter layer under forests of Moso bamboo,Chinese fir,Masson pine,broad leaved,and mixed coniferous and broad-leaved were0. 231,0. 034,0. 062,0. 125,and 0. 090 tCO2·hm^-2,respectively; the Phyt OC stocks in 0 - 10 cm soil layer for Moso bamboo,Chinese fir,Masson pine,broad leaved,and mixed coniferous and broad-leaved stand were 0. 492,0. 217,0. 352,0. 362,and 0. 448 tCO2·hm^-2,respectively; 【Conclusion】The above-mentioned results showed that Phyt OC was returned to the soil through litterfall of all the 5 stand types,and the largest Phyt OC content in the litter as well as the largest Phyt OC stock in litter and the soils was obtained from Moso bamboo. Assuming a litter biomass of 3. 6 t·hm^- 2a^- 1under Moso bamboo,the Phyt OC sequestration rate in the litter layer under subtropical Moso bamboo forest in China＇s subtropics to be 0. 057 tCO2·hm^-2a^- 1. The Phyt OC stock data of the litters of 5 stand types provided a scientific basis for evaluation of Phyt OC sequestration potentials in China＇s subtropical forest ecosystem.