黄土丘陵区植被类型对土壤微生物量碳氮磷的影响

Effects of vegetation types on soil microbial biomass C,N,P on the Loess Hilly Area

选择黄土丘陵区延河流域4种典型植被类型下的土壤为研究对象,测定了土壤微生物量碳、氮、磷和相关基本理化性质。结果表明,在此流域的典型天然草地、人工灌木林、人工乔木林和农地中土壤微生物量碳(MBC)的含量范围分别为315.15—400.89、246.56—321.25、267.76—347.05和118.96—245.14 mg/kg,土壤微生物量氮(MBN)的含量范围分别为35.87—47.63、27.63—42.89、24.66—36.20和15.64—22.56 mg/kg,土壤微生物量磷(MBP)的含量范围分别为14.14—22.96、12.89—19.75、11.54—14.40和7.23—11.59 mg/kg;土壤微生物量总体呈现出天然草地最高、人工乔、灌木林次之,且均显著高于农地的趋势,表明退耕还林还草对土壤微生物生物量有明显的促进作用。不同植被类型下,土壤微生物量碳氮比和碳磷比的变化范围分别为7.49—10.87和16.27—24.11,土壤微生物量碳、氮、磷占土壤有机碳(SOC)、全氮(TN)、全磷(TP)百分比的范围分别为2.70%—4.85%、2.56%—4.45%、2.08%—5.34%。其中天然草地、人工灌木林和农地土壤的微生物量碳氮比、碳磷比均显著小于人工乔木林(P<0.05);MBC/SOC在不同植被类型下的差异不显著,MBN/TN和MBP/TP均呈现出天然草地>人工灌木林>人工乔木林和农地的趋势,且差异显著(P<0.05)。微生物量碳、氮、磷与土壤有机碳、全氮和土壤含水率呈现极显著或显著相关性,与土壤pH值呈现出不同程度的负相关性,表明植被类型对这些与土壤微生物量紧密相关的理化性质也有显著影响。

The Loess Plateau is an important site for many ecological restoration studies in China. Different vegetation types change the soil environment to different extents, influencing the biogeochemical cycles of materials such as soil microbial biomass carbon, nitrogen and phosphorus. Determining the relationship between soil physicochemical properties and soil microbial biomass under different vegetation types can provide useful information for vegetation restoration in the Loess Plateau. Soil profiles under four typical vegetation types （ natural grassland, artificial shrub land, artificial timber forest and crop land） were collected in the Yanhe River catchment in a hilly area of the Loess Plateau. The Yanhe River catchment （36023＇-37017＇ N, 108045＇-110028＇ E） is situated in the north of the Shaanxi Province. It belongs to the continental monsoon climate. The basic soil physicochemical properties and microbial biomass carbon （MBC） , nitrogen （MBN） , and phosphorus （MBP） were measured. The results indicated that the MBC of natural grassland, artificial shrub land, artificial timber forest and crop land ranged from 315.15-400.89, 246.56-321.25,267.76-347.05 and 118.96-245.14 mg/kg, respectively and the MBN ranged from 35.87-47.63, 27.63-42.89, 24.66-36.20 and 15.64-22.56 mg/kg,respectively and the MBP ranged from 14.14-22.96, 12.89-19.75, 11.54-14.40 and 7.23-11.59 mg/kg, respectively. Natural grassland showed the highest soil microbial biomass, followed by artificial timber forest, artificial shrub land and crop land, indicating that returning crop land to forests or grassland had a significant promoting impact on the soil microbial biomass. Under the different types of vegetation, the MBC/MBN ranged from 7.49 to 10.87, and the MBC/MBP ranged from 16.27 to 24.11. The ratio of MBC/soil organic C was 2.70%-4.85%, the ratio of MBN/total N was 2.56%-4.45% and the ratio of MBP/total P was 2.08%-5.34%. The MBC/MBN and MBC/MBP of natural grassland, artificial timber forests and crop land were all significantly less than the artificial shrub land （P 〈 0.05） , but the MBC/soil organic C showed no significant differences between vegetation types. The MBN/total N and MBP/total P of natural grasslands were significantly more than the artificial shrub land, followed by the artificial timber forest and the crop land （P 〈 0.05）. The soil microbial biomass correlated or significantly correlated with soil organic C, total N and soil moisture, but negatively correlated with the soil pH. This showed that the vegetation types had a significant impact on the physical and chemical properties of soil that are closely associated with the soil microbial biomass.