Soil microbial communities resistant to changes in plant functional group composition
Marshall, C. B., J. R. McLaren, and R. Turkington. 2011. Soil Biology and Biochemistry. 43:78-85
Abstract
The soil community is an often ignored part of research which links plant biodiversity and ecosystem
functioning despite their influence on numerous functions such as decomposition and nutrient cycling.
Few consistent patterns have been detected that link plant and soil community composition. We used
a removal experiment in a northern Canadian grassland to examine the effects of plant functional group
identity on soil microbial community structure and function. Plant functional groups (graminoids,
legumes and forbs) were removed independently from plots for five growing seasons (2003-2007) and
in the fifth year effects on the soil microbial community were examined using substrate-induced
respiration (SIR - a measure of metabolic diversity) and phospholipid fatty acid analysis (PLFA -
a measure of microbial community composition). Removal treatments were also crossed with both
a fertilizer treatment and a fungicide treatment to determine if effects of functional group identity on the
soil community were context dependent. Plant functional group identity had almost no effect on the soil
microbial community as measured by either SIR or PLFA. Likewise, soil properties including total carbon,
pH, moisture and nutrients showed a limited response to plant removals in the fifth year after removals.
We found a direct effect of fertilizer on the soil community, with fertilized plots having decreased
metabolic diversity, with a decreased ability to metabolize amino acids and a phenolic acid, but there was
no direct soil microbial response to fungicide. We show that in this northern Canadian grassland the soil
microbial community is relatively insensitive to changes in plant functional group composition, and
suggest that in northern ecosystems, where plant material is only slowly incorporated into the soil, five
growing seasons may be insufficient to detect the impact of a changing plant community on the soil
microbes.
Key Words
Soil microbial community, Removal experiment, Biodiversity, Ecosystem function, Fertilization, AMF, PLFA, Substrate-induced respiration
