中国重要丛生竹土壤植硅体碳积累特征与稳定性机制

Phytolith, also called plant opal, is highly resistant to oxidation, decomposition, high temperature, and corrosion. It has been regarded as the soil C with long-term stability. The concentraiton for the C ocluded in soil phytolith (PhytOC) is 0.1%-6%. When plants die and subsequently decompose, the phytolith is released into soils and sediments, and the PhytOC can be reserved and accumulated for a long time. Therefore, PhytOC plays a very important role in long-term terrestrial C sequestration, and it has a very important significance in regulation of C balance and mitigation of global climate change. Six important sympodial bamboo species in China will be selected in this study. The PhytOC storage and distribution in forest ecosystem, C accumulation characteristic in bamboo forests with different durations under intensive management, effects of site condtions on soil PhytOC content, relationship between management practices and soil PhytOC accumulation, and effects of site conditions and management practices on the stability of soil PhytOC will be intensively investigated in this study. The objectives of this study were to elucidate the accumulation characterisitc and stability mechansism of soil PhytOC in important sympodial bamboo species in China, develop the new methods to determine the PhytOC concentration and phytate stability, and establish the soil PhytOC calculation model. This study will provide the technological support for the evaluation of soil PhytOC sequestration potential in sympodial bamboo systems in China, which has very important significance in the calculation and regulation of soil PhytOC in Chinese forests.

植硅体俗称植物蛋白石，具有很强的抗氧化性、抗分解能力和耐高温、抗腐蚀特性，是长期稳定的土壤有机碳。植硅体含有0.1%- - 6%有机碳（即植硅体碳，PhytOC），植物死亡后PhytOC可以在土壤中长期保存和累积。因此，植硅体碳对陆地生态系统长期碳固定具有重要作用，对调节碳平衡和缓解全球气候变化具有十分重要的意义。本项目选择中国6种重要丛生竹为研究对象，开展竹林生态系统植硅体碳储量及分配规律、竹林不同栽培历史土壤植硅体碳累积特征、立地条件对土壤植硅体碳含量的影响、人为经营措施与土壤植硅体碳积累关系和栽培历史、立地条件及人为经营对PhytOC稳定性影响等方面研究，以探明中国重要丛生竹土壤植硅体碳积累特征与稳定性机制，研建植硅体碳含量和植硅体稳定性测定的新方法，建立丛生竹土壤植硅体碳计量模型，为准确估测中国丛生竹系统土壤植硅体碳封存潜力提供技术支持，对中国森林土壤植硅体碳汇计量与调控具有重要意义。

植硅体具有很强的抗氧化性、抗分解能力，受植硅体保护，植物死亡后植硅体碳可以在土壤中长期保存和累积，对调节碳平衡和缓解全球气候变化具有十分重要的意义。我国丛生竹有160 余种，共计80万公顷。丛生竹以生长快、生物量大著称，又是典型的富硅植物，因此，中国丛生竹系统很可能是一个重要的植硅体碳库。中国丛生竹品种多样、生物量及经营差异大、说明不同丛生竹之间植硅体碳可能有较大差异。.项目通过中国8种重要丛生竹品种硅储量及其差异、碳储量品种差异及其空间分配规律、植硅体碳的差异与空间分布等研究，估算了中国丛生竹生态系统植硅体碳总储量，研究明确了重要丛生竹植硅体碳稳定性及其趋势，选定特定区域，研究了丛生竹土壤植硅体碳空间变异及其受人为经营与立地条件的影响结果。结果表明： 8种丛生竹生态系统碳总储量介于86.295~181.811 Mg C ha-1之间，其顺序为：龙竹> 慈竹> 绿竹> 缅甸竹> 黄竹> 粉单竹> 青皮竹> 麻竹。不同丛生竹生态系统中植硅体碳储量的变化范围为0.33~2.74 t•ha-1，不同丛生竹生态系统中的大小依次为慈竹>黄竹>龙竹>青皮竹>粉单竹>麻竹>缅甸竹>绿竹，中国重要丛生竹生态系统植硅体碳总储量约为9.17×105 t•C。不同丛生竹竹种植硅体溶解度和植硅体碳释放量存在显著性差异，不同丛生竹竹种植硅体浸提后占浸提前植硅体含碳量范围为9%-82%。丛生竹竹林年龄和海拔是影响土壤植硅体碳的主要因子。采用0.01 mol/L硫酸作为浸提剂提取的土壤有效硅含量与丛生竹叶中植硅体碳含量具有显著的相关性。.项目研究的科学意义在于，（1）明确了不同丛生竹生态系统植硅体碳储量的差异，得到了中国丛生竹植硅体碳的总储量。（2）证实了植硅体碳具有不稳定性，不同丛生竹之间稳定性存在差异。（3）发现了土壤有效硅含量、竹龄和海拔是影响土壤植硅体碳的主要因子。