The use of exogenous silicon (Si) amendments, such as Si fertilizers and biochar, can effectively increase crop Si uptake and the formation of phytoliths, which are siliceous substances that are abundant in numerous plant species. Phytolith-occluded carbon (C) (PhytOC) accumulation in soil plays an important role in long-term soil organic C (SOC) storage. Nevertheless, the effects of both Si fertilizer and biochar application on PhytOC sequestration in forest plant-soil systems have not been studied. We investigated the impact of Si fertilizer and biochar applications on 1) the PhytOC pool size, the solubility of plant and soil phytoliths, and soil PhytOC in soil physical fractions (light (LFOM) and heavy fractions of organic matter (HFOM)) in Moso bamboo (Phyllostachys pubescens) forests; and 2) the relationships among plant and soil PhytOC concentrations and soil properties. We used a factorial design with three Si fertilizer application rates: 0 (S0), 225 (S1) and 450 (S2) kg Si ha-1, and two biochar application rates: 0 (B0) and 10 (B1) t ha-1. The concentrations of PhytOC in the bamboo plants and topsoil (0-10 cm) increased with increasing Si fertilizer addition, regardless of biochar application. Biochar addition increased the soil PhytOC pool size, as well as the LFOM- and HFOM-PhytOC fractions, regardless of Si fertilizer application. The Si fertilizer application increased or had no effect on soil phytolith solubility with or without biochar application, respectively. Soil PhytOC was correlated with the concentration of soil organic nitrogen (R2 = 0.32), SOC (R2 = 0.51), pH (R2 = 0.28), and available Si (R2 = 0.23). Furthermore, Si fertilizer application increased plant and soil PhytOC by increasing soil available Si. Moreover, biochar application increased soil PhytOC concentration in LFOM-PhytOC and the unstable fraction of PhytOC. We conclude that Si fertilizer and biochar application promoted PhytOC sequestration in the plant-soil system and changed its distribution in physical fractions in the Moso bamboo plantation in subtropical China.

中文翻译：

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硅肥和生物炭对亚热带竹林植物和土壤PhytOC浓度以及土壤PhytOC稳定性和分馏的影响。

使用诸如硅肥和生物炭之类的外源性硅（Si）改良剂可以有效地增加农作物对硅的吸收和植硅石的形成，而硅石是许多植物物种中丰富的硅质物质。土壤中的植烷吸附碳（PhytOC）积累在长期土壤有机碳（SOC）存储中起着重要作用。然而，尚未研究硅肥和生物炭施用对植物植物-土壤系统中PhytOC螯合的影响。我们研究了硅肥和生物炭的施用对1）毛草中PhytOC池大小，植物和土壤植石的溶解度以及土壤PhytOC在土壤物理组分（轻质（LFOM）和有机质重质组分（HFOM））中的影响竹林（Phyllostachys pubescens）；2）植物和土壤PhytOC浓度与土壤特性之间的关系。我们使用的因子设计采用三种Si肥料施用量：0（S0），225（S1）和450（S2）kg Si ha-1，以及两种生物炭施用量：0（B0）和10（B1）t ha- 1。不论施用生物炭如何，竹肥和表土（0-10 cm）中PhytOC的浓度均随硅肥添加量的增加而增加。无论使用何种硅肥，添加生物炭都会增加土壤PhytOC库的大小，以及LFOM-和HFOM-PhytOC的比例。施用或不施用生物炭分别增加或不影响硅藻土溶解度。土壤PhytOC与土壤有机氮（R2 = 0.32），SOC（R2 = 0.51），pH（R2 = 0.28）和有效Si（R2 = 0.23）的浓度相关。此外，硅肥的施用通过增加土壤可利用的硅来增加植物和土壤的PhytOC。此外，生物炭的施用增加了LFOM-PhytOC中土壤PhytOC的浓度以及PhytOC的不稳定部分。我们得出的结论是，硅肥和生物炭的施用促进了植物-土壤系统中的PhytOC隔离，并改变了亚热带毛竹种植园中其物理组分的分布。