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Microbial growth rate measurements reveal that land-use abandonment promotes a fungal dominance of SOM decomposition in grazed Mediterranean ecosystems

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Author

Summary, in English

The present study investigated the effects of land-use abandonment on the soil decomposer community of two grazed Mediterranean ecosystems (an annual grassland with scattered holm oaks and a low-density shrubland). To test the influence of grazing abandonment, a set of plots within each site were fenced and kept undisturbed during 4-5 years, during which above-ground plant community structure was monitored. After that, soil samples were collected from grazed and abandoned plots corresponding to the three different soil conditions: away from ("grass") and below tree canopies ("oak") within the annual grassland, and from the shrubland ("shrub"). Soil samples were split into two different layers (0-5 and 5-15 cm) and then analyzed for saprotrophic fungal (acetate into ergosterol incorporation) and bacterial (leucine incorporation) growth rates. Ergosterol content (as a fungal biomass estimator) and a standard set of soil chemistry variables were also measured. After 5 years of grazing exclusion, saprotrophic fungal growth rate clearly increased in both grass and oak surface layers whereas bacterial growth rate was not altered. This translated into significantly higher fungal-to-bacterial (F/B) growth rate ratios within the ungrazed plots. Similar trends were observed for the shrub soils after 4 years of exclusion. On the contrary, abandonment of grazing had negligible effects on the ergosterol content, as well as on the soil chemical variables (soil organic carbon, total N, C/N ratio, and pH), in all the three soil conditions assessed. These results indicated a shift toward a more fungal-dominated decomposer activity in soils following cessation of grazing and highlighted the sensitivity of the microbial growth rate parameters to changes associated with land use. Moreover, there were evidences of a faster fungal biomass turnover in the ungrazed plots, which would reflect an accelerated, though not bigger, fungal channel in soil organic matter mineralization.

Publishing year

2011

Language

English

Pages

129-138

Publication/Series

Biology and Fertility of Soils

Volume

47

Issue

2

Document type

Journal article

Publisher

Springer

Topic

  • Biological Sciences

Keywords

  • Grazing exclusion
  • Mediterranean
  • Decomposer ecology
  • Fungal growth
  • rate
  • Bacterial growth rate
  • Ergosterol

Status

Published

Project

  • Effect of environmental factors on fungal and bacterial growth in soil

Research group

  • Microbial Ecology

ISBN/ISSN/Other

  • ISSN: 0178-2762