Volume 97, January 2016, Pages 112–124
Highlights
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- Application of fourteen biological indicators at 76 sites across Europe.
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- Land use intensification lowered density networks and reduced in the average number of neighbours.
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- Basal respiration, molecular microbial biomass and fungal richness describe soil carbon cycling.
Abstract
Soil
organisms are considered drivers of soil ecosystem services (primary
productivity, nutrient cycling, carbon cycling, water regulation)
associated with sustainable agricultural production. Soil biodiversity
was highlighted in the soil thematic strategy as a key component of soil
quality. The lack of quantitative standardised data at a large scale
has resulted in poor understanding of how soil biodiversity could be
incorporated into legislation for the protection of soil quality. In
2011, the EcoFINDERS (FP7) project sampled 76 sites across 11 European
countries, covering five biogeographical zones (Alpine, Atlantic,
Boreal, Continental and Mediterranean) and three land-uses (arable,
grass, forestry). Samples collected from across these sites ranged in
soil properties; soil organic carbon (SOC), pH and texture. To assess
the range in biodiversity and ecosystem function across the sites,
fourteen biological methods were applied as proxy indicators for these
functions. These methods measured the following: microbial diversity:
DNA yields (molecular biomass), archaea, bacteria, total fungi and
arbuscular mycorrhizal fungi; micro fauna diversity: nematode trophic
groups; meso fauna diversity: enchytraeids and Collembola species;
microbial function: nitrification, extracellular enzymes, multiple
substrate induced respiration, community level physiological profiling
and ammonia oxidiser/nitrification functional genes. Network analysis
was used to identify the key connections between organisms under the
different land use scenarios. Highest network density was found in
forest soils and lowest density occurred in arable soils. Key taxomonic
units (TUs) were identified in each land-use type and in relation to SOC
and pH categorisations. Top-connected taxonomic units (i.e. displaying
the most co-occurrence to other TUs) were identified for each land use
type. In arable sites this was dominated by bacteria and fungi, while in
grassland sites bacteria and fungi were most connected. In forest soils
archaeal, enchytraeid and fungal TUs displayed the largest number of
neighbours, reflecting the greatest connectivity. Multiple regression
models were applied to assess the potential contribution of soil
organisms to carbon cycling and storage and nutrient cycling of
specifically nitrogen and phosphorus. Key drivers of carbon cycling were
microbial biomass, basal respiration and fungal richness; these three
measures have often been associated with carbon cycling in soils.
Regression models of nutrient cycling were dependent on the model
applied, showing variation in biological indicators.
Graphical abstract
Keywords
- Soil biodiversity;
- Ecosystem function;
- Carbon cycling and storage;
- Nitrogen;
- Phosphorus;
- Nutrient cycling;
- Network analysis
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