In-depth insight into the short-term effect of floor management practice on young apple trees development and soil microbial biodiversity and activity

PLOS One | https://doi.org/10.1371/journal.pone.0329979 August 7, 2025 7 / 15 Living mulches impact on soil microbiome The comparison of microbial activity level (AWCD), biodiversity Index (H’) and substrate richness (S) of the soil samples collected across the 2022 vegetative season are presented in Table 3. The two plant mixtures induced different effects on the soil microbiome. Mix1 did not affect microbial activity throughout the vegetative season, until the last sampling time, when it was reduced compared to control. However, the opposite pat- tern was observed for the biodiversity and richness indexes, which were both higher in spring time compared to control, but then returned similar to it in the following periods. Mix2 induced a different pattern dynamic for the bacterial activity compared to control, showing a lower activity in spring, higher in summer and similar in autumn. On the other hand, a pos- itive steadily increasing pattern was observed for the other two indices, with lower values in spring, and higher in autumn than control (S2 Table). Irrespective of the different dynamic patterns observed for the three indices (AWCD, H and S), all classes of C-sources utilised by the bacterial community for its metabolism resulted to be significantly more exploited during summer (S2 Table and Fig 3). Compared to both spring and autumn (only for phenolic compounds the difference was not statistically sig- nificant). However, the two living mulches induced some modifications in the level of use of few classes of C-sources.

In spring the metabolism of carboxylic acid and phenolic compounds was decreased by Mix2, while Mix1 induced an Fig 2. PCA based on the leaves total nutrients content. Each point represents a replicate for the specific treatment. https://doi.org/10.1371/journal.pone.0329979.g002 Table 3. The impact of two kinds of living mulches on soil bacterial activity and biodiversity indices. Treatment AWCD H S Spring Summer Autumn Spring Summer Autumn Spring Summer Autumn Control 0.93 a 1.53 b 1.11 a 2.98 b 3.31 a 2.93 b 17.67 b 29.33 a 17.67 b Mix1 1.00 a 1.55 b 0.82 b 3.08 a 3.27 a 2.87 b 20.67 a 27.67 a 16.33 b Mix2 0.75 b 1.73 a 1.07 a 2.86 c 3.32 a 3.12 a 15.00 b 30.00 a 22.00 a Timepoint 0.89 b 1.60 a 1.00 b 2.97 b 3.30 a 2.97 b 17.78 b 29.00 a 18.67 b Different letters show statistically significant differences between treatments within each sampling point for p ≤ 0.05. https://doi.org/10.1371/journal.pone.0329979.t003