Seasonal changes in soil microbial communities along a fertility gradient of temperate grasslands

• Published in: Soil biology & biochemistry Vol. 31; no. 7; pp. 1021 - 1030
• Main Authors: Bardgett, Richard D., Lovell, Roger D., Hobbs, Phil J., Jarvis, Steve C.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-07-1999; New York, NY Elsevier Science
• Subjects: Agronomy. Soil science and plant productions; Animal, plant and microbial ecology; Biochemistry and biology; Biological and medical sciences; biomass; Chemical, physicochemical, biochemical and biological properties; communities; drainage; fatty acids; fertilized versus unfertilized soils; fertilizers; Fundamental and applied biological sciences. Psychology; grassland soils; microbial community structure; Microbial ecology; Microbiology; phospholipids; Physics, chemistry, biochemistry and biology of agricultural and forest soils; ratios; seasonal variation; Soil; soil bacteria; soil fertility; soil fungi; soil management; soil management intensity; Soil science; temperate soils; England; United Kingdom; Great Britain; Europe; Silty clay loam soil; Microbial activity; Nitrogen fertilization; Soil fertility; Phospholipid; Temperate zone; Fatty acids; Microbial biomass; Permanent grassland; Carbon cycle; Drainage; Fungi; Nitrogen cycle; Pasture; Seasonal variation; Bacteria; Microbial community; Thallophyta; Grassland soil
• ISSN: 0038-0717; 1879-3428
• DOI: 10.1016/S0038-0717(99)00016-4

This study aimed to: (1) determine whether soil microbial communities along a gradient from intensive (fertilized) to low-input (unfertilized) grassland management, shift in their composition as shown by an increase in the abundance of fungi relative to bacteria and (2) whether these shifts in soil microbial communities vary depending on season. At all sample dates soil microbial biomass-C and -N, and the total abundance of phospholipid fatty acids (PLFA) were highest in unfertilized, undrained treatments and lowest in fertilized and drained grassland. Similarly, microbial activity, measured as CO
2-C respiration, was found to be at its lowest in the most intensively managed grassland. Measures of microbial biomass showed a high degree of seasonality, having summer maxima and winter minima. In contrast, PLFA measures had spring maxima and autumn minima. Seasonal and management differences were also observed within the microbial community. PLFA profiles revealed that most individual fatty acids were highest in the unfertilized treatments, and lowest in fertilized grassland. The fungal-to-bacterial biomass ratio was also highest in the unfertilized and lowest in the fertilized soils, suggesting that higher microbial biomass in former were more due to the growth of fungi than bacteria. As with total PLFA, the abundance of individual fatty acids showed a spring maximum and an autumn minimum. Seasonal differences in PLFA patterns were shown to be related to soil mineral-N and soil moisture contents. Factors controlling shifts in microbial community structure between sample dates and sites are discussed in relation to other studies. A critical assessment of the different measures of microbial biomass is also given. Overall, the findings of this study support the thesis that fungi play a more significant role in soil biological processes of low-input, unfertilized grasslands, than in intensively managed systems.