ABSTRACT

Although the response of plant productivity and soil biogeochemical processes to nutrient addition has been widely investigated, little is known about the effects of N and P addition on soil aggregate fractions, an important indicator of soil organic C stability. We investigated the effects of exogenous N and P inputs on soil aggregates and their associated organic C in a 6-year fertilisation experiment in a subtropical Chinese fir (Cunninghamia lanceolata) plantation. A wet sieving method was used to determine the aggregate size distribution. Our results showed that the most abundant aggregate was the macroaggregate, ranging between 59% and 74%. The least abundant fraction was the smallest (silt and clay), ranging between 10% and 15%. Neither the soil aggregate fractions nor their associated organic C differed significantly after 6 years of N and P addition at the 0.05 level. In contrast, the oxalate-extractable iron Fe and pyrophosphate-extractable Fe of 0–10 cm soil were significantly decreased by P addition; this may alter aggregate formation over longer periods. Thus, future studies should examine the effects of nutrient addition on aggregates over a longer period. In particular, more attention should be paid to the effects of P addition in subtropical forests.

摘要

尽管植物生产力和土壤生物地球化学过程对养分添加的响应已被广泛研究，但关于 N 和 P 添加对土壤团聚体分数的影响知之甚少，这是土壤有机碳稳定性的重要指标。我们在亚热带杉木 ( Cunninghamia lanceolata)的 6 年施肥试验中研究了外源 N 和 P 输入对土壤团聚体及其相关有机碳的影响) 种植园。湿筛分法用于确定骨料粒度分布。我们的结果表明，最丰富的聚集体是大聚集体，介于 59% 和 74% 之间。最不丰富的部分是最小的（淤泥和粘土），范围在 10% 到 15% 之间。在添加 0.05 的氮和磷 6 年后，土壤团聚体比例及其相关有机碳均无显着差异。相比之下，0-10 cm 土壤的草酸盐可提取铁 Fe 和焦磷酸盐可提取 Fe 因 P 的添加而显着降低；这可能会在较长时期内改变聚集体的形成。因此，未来的研究应该在更长的时间内检查营养添加对聚集体的影响。尤其要关注亚热带森林中磷添加的影响。