In the present study, both aggregate stability and repellency were reduced in month 7; specifically the degree of reduction in repellency was less in the mycorrhizal soils than in the non-mycorrhizal soils. In the mycorrhizal soils, aggregate water repellency was also negatively correlated with bacterial (and fungal) TRF richness but positively correlated with root size and microbial biomass-C. It is likely that mycorrhizal hyphae contributed to the microbial biomass-C measured here which might explain why microbial biomass-C was not a factor in the model explaining repellency in the NM soils. In the mycorrhizal soils the relationship between microbial biomass-C and aggregate stability was negative, whilst it was positive for repellency. The GLM regressions used data for all 7 months but the system was dynamic across the months. For example, aggregate stability was greater in the mycorrhizal soils in month 3, yet repellency increased in months 5 and 7. The positive relationship observed between per cent root length colonised and microbial biomass-C is likely to be the result of increasing hyphal length in the soil, or possibly an enhancement of other microbial species too, since internal AMF root colonisation may not reflect the extraradical hyphal biomass. Aggregate turnover rates range from 4 to 88 days (De Gryze et al. 2005, 2006); an increase in aggregate stability observed here over a 60 day period (from the first to third month harvest) and an increase in aggregate water repellency over a 120 day period (from the first to fifth month harvest) is comparable to that observed by others.
months
7
Aggregate turnover
rates
range from 4 to 88 days
days
aggregate stability
period
over a 60 day
day
aggregate water repellency
period
over a 120 day
day