北亚热带麻栎林土壤植硅体碳储量研究

  目的  研究北亚热带麻栎Quercus acutissima林土壤植硅体碳(PhytOC)质量分数及剖面分布规律，探讨不同林龄麻栎林土壤植硅体碳储量的差异。  方法  以江苏省句容市不同林龄麻栎林土壤为研究对象，按照0~10、10~20、20~40、40~60 cm分层取土壤样品，测定植硅体和植硅体碳质量分数，并估算麻栎林土壤植硅体碳储量。  结果  土壤有效硅质量分数为45.7~153.3 mg·kg?1，随土层深度增加而增大，各分层之间有效硅质量分数差异不显著，不同林龄麻栎林土壤有效硅质量分数差异显著(P＜0.05)。幼龄林和成熟林土壤植硅体、植硅体碳和植硅体中有机碳质量分数均随土层深度增加先增大后减小，而中龄林则随土层深度增加而减小；不同林龄之间土壤植硅体、植硅体碳、植硅体中有机碳质量分数差异显著(P＜0.05)，而各土层之间差异均不显著。土壤植硅体碳和总有机碳质量分数比值(PhytOC/TOC)为0.36%~1.49%，大致随土层深度的增加而增大；不同土层之间PhytOC/TOC差异不显著，但各林龄之间差异显著(P＜0.05)。土壤植硅体与植硅体碳质量分数之间呈极显著正相关关系(P＜0.01)，植硅体碳与有效硅质量分数之间无相关性；麻栎林土壤植硅体碳储量为1.15~1.47 t·hm?2，幼龄林、中龄林、成熟林土壤的植硅体碳储量占有机碳储量的比例分别为0.80%~1.50%、0.73%~1.10%、0.36%~0.67%，占比较小。  结论  受土壤理化性质、淋溶作用等的影响，植硅体和植硅体碳质量分数在不同林龄麻栎林土壤剖面中的分布具有一定的差异性。植硅体碳储量占有机碳储量的比例较小，但随土层深度的增加而增大，表明植硅体碳较其他形式的碳更加稳定。从时间尺度上来讲，植硅体碳汇是森林长期碳汇的重要组成部分。图3表4参41

Soil PhytOC sequestration in Quercus acutissima forest in northern subtropics

  Objective  The purpose is to investigate the content and profile distribution of soil PhytOC in northern subtropical Quercus acutissima forest, and discuss the difference of PhytOC sequestration in Q. acutissima forest at different ages.  Method  Taking soil samples from Q. acutissima forest of different ages in Jurong City, Jiangsu Province as the research object, the soil samples were collected in layers of 0?10, 10?20, 20?40 and 40?60 cm to determine the content of phytolith, PhytOC, and the PhytOC sequestration in soil of Q. acutissima forest.  Result  The available silicon content of soil ranged from 45.74 to 153.32 mg·kg?1, which increased with the increase of soil depth. There was no significant difference in the content of soil available silicon among different layers, but there existed significant difference in soil available silicon content among different forest ages (P＜0.05). The content of soil phytolith, PhytoOC and organic carbon in phytolith in young forest and mature forest increased first and then decreased with the increase of soil depth, whereas that in half-mature forest decreased with the increase of soil depth. The content of organic carbon in soil phytoliths, PhytoOC and phytoliths was significantly different among different forest ages (P＜0.05), but difference was not significant among layers. In addition, the ratio of PhytOC/TOC ranged from 0.36% to 1.49%, which increased with the increase of soil depth. There was no significant difference in the ratio of phytoc/TOC among different soil layers, but there was significant difference among different forest ages (P＜0.05). There was an extremely significant positive correlation between soil phytolith content and PhytOC content (P＜0.01), but there was no correlation between PhytOC content and available silicon content. The PhytOC sequestrations in the soil of Q. acutissima forest ranged from 1.15 to 1.47 t·hm?2, and the proportions of PhytOC sequestrations to organic carbon storage in young forest, middle-aged forest and mature forest soil accounted for 0.80%?1.50%, 0.73%?1.10% and 0.36%?0.67%, respectively.  Conclusion  Affected by soil physical and chemical properties, and leaching, etc., the distribution of phytolith and PhytOC in soil profiles of Q. acutissima forest at different ages is different to some extent. The proportion of PhytOC sequestration to organic carbon storage was small, but it increased with the increase of soil depth, indicating that PhytOC is more stable than other forms of carbon. In terms of time scale, PhytOC sink is an important component of long-term carbon sinks in forests. Ch, 3 fig. 4 tab. 41 ref.]