黄土丘陵区植被类型对土壤微生物量碳氮磷的影响

Abstract

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( 36°23'—37°17' N,108°45'—110°28' 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.