封育与放牧对黄土高原天然草地土壤化学计量特征的影响

为揭示封育与放牧2种草地利用方式下土壤化学计量特征及其驱动因素,以宁夏固原云雾山封育草地和放牧草地为研究对象,定量分析了0—30 cm土壤化学计量特征及其影响因子。结果表明:(1)封育降低了土壤紧实度、容重和含水率,土壤孔隙度略有上升。(2)封育草地0—10 cm土层以0.25 mm水稳性团聚体为主,其中5 mm团聚体达到了46%,平均重量直径(MWD)和几何平均直径(GWD)分别为3.78,1.70,显著高于放牧草地(P0.05),但两者分形维数并无差异,封育草地土壤团聚体稳定性有所提高。(3)封育草地0—10 cm土层土壤有机碳(SOC)、全氮(TN)、全磷(TP)分别为17.714,2.018,0.659 g/kg,均高于放牧草地,其中土壤TN含量达到显著水平(P0.05)。(4)封育草地0—20 cm土层碳氮比(C/N)、碳磷比(C/P)、氮磷比(N/P)均高于放牧草地。(5)封育草地土壤SOC、TN、C/P和N/P与土壤容重和分形维数呈显著性负相关(P0.05),并且SOC和TN与MWD和GWD呈显著性正相关(P0.05),放牧草地土壤化学计量特征与物理特性相关性低于封育草地。封育与放牧相比,改善了土壤物理特性和团聚体结构,土壤养分有所提升,土壤化学计量特征与土壤物理特性密切相关,土壤物理结构可能是影响土壤化学计量特征的主控因子。

Effect of Enclosure and Grazing on the Soil Stoichiometry Characteristics of Natural Grassland on the Loess Plateau

In order to reveal the soil stoichiometric characteristics and their driving factors under the two grassland utilization modes of enclosure and grazing, the enclosed and grazing grassland of the Ningxia Yunwushan in Guyuan were used as the research object, the soil stoichiometric characteristics of 0-30 cm layer and the influencing factors were quantitatively analyzed. The results showed that: (1) Enclosure decreased the soil penetration resistance, bulk density and moisture content, while increased the soil porosity. (2) In the 0-10 cm soil layer of the enclosed grassland, the main water stable aggregates were > 0.25 mm, and of which >5 mm water-stable aggregates accounted for 46%, the mean weight diameter (MWD) and geometric mean diameter (GWD) was 3.78 and 1.70, respectively, which were significantly higher than those of grazing grassland (P<0.05), but there was not significant in fractal dimension between enclosed and grazing grassland. The soil stability of enclosed grassland was improved. (3) The content of soil organic carbon (SOC), total nitrogen (TN) and total phosphorus (TP) of the 0-10 cm soil layer in enclosed grassland was 17.714, 2.018 and 0.659 g/kg, respectively, which were all higher than those of grazing grassland, and the difference in TN was significant (P<0.05). (4) The soil carbon and nitrogen ratio (C/N), carbon and phosphorus ratio (C/P), and nitrogen and phosphorus ratio (N/P) of the 0-20 cm soil layer were all higher in enclosed grassland than those in grazing grassland. (5) SOC, TN, C/P and N/P were all significantly negative related to the soil bulk density and fractal dimension (P<0.05), and SOC and TN were significantly positive related to MWD and GWD in enclosed grassland (P<0.05). The correlation between soil stoichiometry and physical characteristics of grazing grassland was lower than that of enclosed grassland. Enclosure ameliorated soil physical properties and aggregate structure, improved soil nutrients. Soil stoichiometry was closely related to soil physical properties, and the soil physical structure might be the main control factor affecting soil stoichiometric characteristics.