Distribution and elevational controls on soil aggregate‐associated organic carbon (OC) and nitrogen (N) in alpine soils are not well known, but may be critical to the stabilization of soil C and N pools in alpine areas. In this study, we determined the variability in aggregate associated OC and N concentration and aggregate‐stability in 0 to 20 cm layers along the elevation gradient in an alpine forest (2,600–3,200 m) of the Qilian Mountains. The results showed that 1–2 mm macroaggregate accounted for the largest proportion (33.9%) of all aggregate fractions, and also contributed greater proportions (33.2 and 32.6%) to OC and N in bulk soils. Concentrations of OC and N, and C to N ratio increased with increasing aggregate size across all elevations. With increasing elevation, the proportion of >1 mm macroaggregates, mean weight diameter (MWD) and geometric mean diameter (GMD) increased significantly (p < .01). Aggregate OC and N concentration and C to N ratios, and the contribution of > 1 mm aggregate OC and N to OC and N in bulk soils also increased significantly (p < .01), while the contribution of 0.25–1 mm and 0.053–0.25 mm aggregates decreased with increasing elevation. In addition, MWD, GMD, OC and N concentration in aggregate decreased with mean annual temperature (MAT) and increased with mean annual precipitation (MAP). Our results demonstrated that the stability of soil structure improved, and accumulation of OC was mainly due to increases in the contribution of OC in the >1 mm macroaggregate with increasing elevation. Given that higher elevations in this alpine forest support large concentrations of SOC and macroaggregate OC, which may be vulnerable to climate warming.

中文翻译：

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高山森林生态系统中伴生有机碳和氮的累积梯度和分布与稳定性

高山土壤中与土壤团聚体相关的有机碳（OC）和氮（N）的分布和海拔控制尚未广为人知，但对于稳定高山地区土壤C和N的库可能至关重要。在这项研究中，我们确定了祁连山高寒森林（2,600–3,200 m）中海拔高度梯度上0至20 cm层中总的相关OC和N浓度以及总稳定性的变化。结果表明，1-2 mm的大型骨料在所有骨料中所占比例最大（33.9％），并且在散装土壤中对OC和N的贡献更大（33.2和32.6％）。OC和N的浓度以及C与N的比例随所有海拔高度的聚集体尺寸的增加而增加。随着海拔的升高，> 1 mm的大骨料的比例，p  <.01）。块状土壤中总的OC和N浓度以及C与N的比率以及大于1 mm的OC和N对OC和N 的贡献也显着增加（p <.01），而贡献度为0.25–1 mm和0.053– 0.25 mm的骨料随高度的增加而减少。另外，MWD，GMD，OC和N的总浓度随年平均温度（MAT）降低而随年平均降水量（MAP）升高。我们的结果表明，土壤结构的稳定性得到了改善，并且OC的积累主要是由于> 1 mm的大型骨料中OC的贡献随着海拔的升高而增加。由于该高山森林海拔较高，因此支持大量的SOC和大量聚集的OC，这可能易受气候变暖的影响。