Organic carbon is known to increase aggregate stability and according to Dal Ferro et al. (2012), ultramicropores enhanced aggregate stability and organic carbon influenced pore size distribution in their study using a 3D network model. This corroborates the data here since the 10−6 dilution (bare soil) had a larger proportion of organic C, smaller and more uniform pore distribution and greater aggregate stability. Since microbial biomass-C was similar in those two treatments, it can be concluded that (fungal) species richness was the primary cause

of the increased porosity and of reduced aggregate stability in the bare 10−1 soil, probably because of increased metabolic activity of the fungi and of the bacterial constituents. In the planted selleck inhibitor systems, root activity changed the dynamic, so that larger pores were observed in the 10−6 dilution amended soils with greater distances between them than in the 10−1 treatments. This affected porosity of the mycorrhizal planted soils but not of the NM planted soils,

where porosity was similar irrespective of dilution. Overall (all data combined), the AM planted soils had smaller pore sizes and lower total porosity than the NM planted soils, but greater aggregate stability. This is in agreement with Bearden (2001) who concluded that AMF hyphae led to soils with groups of small pores. There is a trend in this study between smaller pore sizes and increased aggregate stability. Feeney et al. (2006) reported increased Antidiabetic Compound Library research buy soil porosity within bulk and rhizosphere soil over a 30 day period and concluded that the soil biota altered their

habitat in favour of a more porous and aggregated structure. The findings here for porosity in the unplanted (bare) soils are in agreement with Feeney et al. (2006), although data relating to porosity in the rhizosphere and mycorrhizosphere do not corroborate Feeney et al. (2006). Total porosity in planted soils with AMF was consistently lower than that of the NM planted HSP90 and bare soils from months 3 to 7. Feeney et al. (2006) worked at a resolution of 4.4 μm, whilst the smallest pores imaged here were 65 μm. Whilst the coarser resolution here may have been a factor in explaining the different findings, the complexity of soil-plant-microbial dynamics in influencing soil structural properties should be highlighted and caution applied when interpreting data from pot experiments. Changes in porosity generally take place over much longer periods than aggregate turn over, particularly at a field scale, where the development of soil structure can take many months to years (Elliott and Coleman, 1988 and Boersma and Kooistra, 1994). The dilution method used here resulted in altered microbial species richness, which was influenced primarily by planting regime and mycorrhizal colonisation. The design of the experiment made it possible to determine the relative influences of these parameters on soil porosity and aggregate stability in addition to soil organic carbon.