蒙古高原草地不同深度土壤碳氮磷化学计量特征对气候因子的响应

Stoichiometric characteristics of soil carbon, nitrogen and phosphorus along soil depths in response to climatic variables in grasslands on the Mongolia Plateau

研究不同深度土壤碳(C)、氮(N)、磷(P)含量及其化学计量比对气候因子(年降水量(MAP)和年平均气温(MAT))的响应差异,对于理解气候变化如何影响生态系统功能具有重要意义。通过对蒙古高原干旱半干旱草地44个样点的野外调查,探讨了不同深度(0–20、20–40、40–60、60–80 cm)土壤C、N、P含量及其化学计量比与MAP和MAT的关系。主要结果:(1)随土壤深度的增加,土壤C和N含量逐渐减少,土壤P含量不变;土壤C:P和N:P逐渐降低,土壤C:N相对稳定。(2)土壤C、N、P含量以及土壤C:P、N:P与MAP显著正相关,与MAT显著负相关,土壤C:N与MAP显著负相关,与MAT无相关性;随着土壤深度的增加,土壤C、N、P含量及其化学计量比与气候因子的相关性均逐渐减弱。(3) MAP和MAT对不同深度土壤C、N、P含量和化学计量比的影响存在显著差异;随着土壤深度的增加, MAP和MAT对土壤C、N、P含量及其化学计量特征变化的总解释度逐渐减少。该研究表明气候因子对土壤元素化学计量特征具有自上而下的调控作用,蒙古高原草地土壤表层C、N、P含量及其化学计量比与MAP和MAT的关系更为密切。

Aims Responses of soil carbon(C), nitrogen(N), and phosphorus(P) contents and their stoichiometric ratios to climatic variables(mean annual precipitation(MAP) and mean annual air temperature(MAT)) along soil depths are important for understanding the effects of climate change on terrestrial ecosystem functions. Methods To explore the responses of soil C, N, and P contents and their stoichiometric ratios along soil profile to MAP and MAT at a regional scale, we investigated these variables for four soil layers(0–20, 20–40, 40–60, and 60–80 cm) at 44 sites in grasslands on the Mongolia Plateau. Important findings(1) Soil C and N contents decreased while soil P did not change with increasing soil depth. Soil C:P and N:P decreased while soil C:N was relatively stable with increasing soil depth.(2) Soil C, N, and P contents, as well as C:P and N:P, were positively correlated with MAP, but negatively correlated with MAT. Soil C:N was negatively correlated with MAP but did not correlate with MAT. The correlations between climate variables and soil C, N, and P contents and their stoichiometric ratios were weakened with increasing soil depth.(3) The effect of MAP or MAT on soil C, N, and P contents and their stoichiometric ratios were different among four soil depths. The total interpretation of the variations in soil C, N, and P contents and their stoichiometric ratios explained by MAP or MAT decreased with increasing soil depth. These results indicate that climatic variables had a top-down regulation on soil C, N, P contents and their stoichiometric ratios, and the effect of MAP was more important than that of MAT on soil C, N, P contents and their stoichiometric ratios in grasslands on the Mongolia Plateau.