Environmental variables and relationship with community structure
Overall, as assessed by the Permanova analysis, no farming system effect (P=0.10; F=2) was detected on chemical and physical variables, while results showed a pronounced sites effect (P<0.001; F=17), as well as a plot effect (P<0.001, F=5). A site-by-site analysis, however, reveals a farming system effect in silt site (P<0.001, t=2.9) as well as in sand site (P=0.03, t=1.9). A Permdisp analysis showed a significant heterogeneity of dispersion within the silt site group (P=0.02, t=2.6) leading to interpret carefully the farming system effect in this group. The examination of the silt plots positions on the PCO lead to conclude that conventional plots were chemically and physically more similar (red symbol at the left side) than the organic plots (green symbols at the left side) (Figure XX).
We summarize the mean and the standard deviation of environmental variables per site and farming system (Table XX).