铁对亚高山草甸不同坡向不同深度土壤有机碳矿化特征的影响

Effects of iron on organic carbon mineralization characteristics of soils at different slopes and depths in a subalpine meadow

以历山舜王坪亚高山草甸半阴坡和半阳坡土壤为研究对象,分析不同坡向不同深度土壤的理化性质和不同形态铁氧化物含量的差异,并通过室内培养实验,研究外源添加铁对土壤有机碳(SOC)累积矿化量、矿化速率和矿化效率的影响.结果表明:SOC、总氮(TN)、碳氮比(C/N)、硝态氮(NO3--N)、速效磷(AP)、酸式草酸铵提取态铁(Feo)和有机质结合态铁(Fep)均随着土层深度增加有逐渐减少的趋势.对于不同坡向和土层深度土壤,SOC矿化速率和累积碳矿化量呈现出半阴坡(NW坡)高于半阳坡(SE坡),0-20 cm土层高于20-40 cm土层.外源加入铁显著降低了SE坡和NW坡0-5 cm土层土壤20.87%和35.50%的累积矿化量,而对深层土壤(20-40 cm)无显著影响.铁的添加增大了SE坡所有土层和NW坡0-5 cm、5-10 cm及20-40 cm土层SOC的矿化效率,表明SOC中易分解有机碳组分的含量增大.此外,本研究中Fep与土壤有机碳矿化特征均显著正相关(P<0.01),表明Fep对亚高山草甸SOC积累发挥着重要作用.综上可见,阴坡土壤有机碳矿化潜力较大,外源铁添加对两坡向不同土层土壤有机碳矿化特征有不同的影响,与土壤中铁氧化还原状态紧密相关.

Soil physicochemical properties and iron(Fe)oxide characteristics under different slopes and different soil layers were analyzed using soils from the semi-shady slope(NW)and semi-sunny slope(SE)in a subalpine meadow in Lishan Shunwangping in Shanxi,China.The effect of Fe addition on the cumulative mineralization,mineralization rate,and mineralization efficiency of soil organic carbon(SOC)was studied through indoor cultivation experiments.The results showed that SOC,total nitrogen(TN),C/N,NO_(3)^(-)-N,available phosphorus(AP),poorly crystalline Fe oxyhydroxides,organically complexed Fe(Feo),and organically complexed Fe(Fep)concentrations decreased with increasing soil depth.The SOC mineralization rate and cumulative mineralization in the NW were significantly higher than those in the SE and were significantly higher in the 0–20 cm soil layer than in the 20–40 cm soil layer.The addition of Fe significantly reduced the amount of SOC mineralization in the SE and NW 0–5 cm soil layers by 20.87%and 35.50%,respectively,while it had no significant influence on SOC mineralization in the deep soil(20–40 cm).Exogenous Fe increased the SOC mineralization efficiency of all soil layers in the SE and the 0–5,5–10,and 20–40 cm soil layers in the NW,indicating that the labile fraction of SOC increased with the addition of Fe.This study showed significant positive correlations between Fep and cumulative mineralization and mineralization rate(P<0.01),indicating that Fep plays an important role in SOC accumulation in subalpine meadow soils.The addition of Fe has different effects on SOC mineralization characteristics in different soil layers,which are closely related to Fe redox conditions.