Influence of maintenance practices on plant community properties interacting with ecosystem functions in an agricultural ditch

Maintenance practices restoring the hydraulic capacity of agricultural ditches (mowing, burning, chemical weeding or dredging) modify the plant communities in the short and medium term. However, the medium term modification of plant community composition, parameters and properties, and in turn the associated functions provided by ditches (water transport, propagules and sediment retention, biodiversity conservation) have not attracted much attention so far. Therefore, the main question raised in this study was the following : Do ditch maintenance practices affect plant community composition, parameters, and properties associated with water and particle transport processes (sediments, seeds), as well as biodiversity, in the medium term (two years)?

We designed an experiment to compare the effects of different maintenance practices in a Mediterranean agricultural ditch. We measured the plant richness, morphological parameters and properties of the plant community affecting ecosystem functions twice : before applying the maintenance practices and after two years of contrasting maintenance practices. We assessed the differences between practices using linear models and generalized linear models, followed by pairwise comparisons between means using the Tukey test.

Maintenance practices differently affected plant community composition, parameters and properties, such as richness, proportions of harmful plants, distribution of heights, densities, proportions of growth forms and total biomass. None of the maintenance strategies simultaneously improved the functions considered. After two years, mowing provided the highest alpha-diversity and had a low proportion of harmful plants. Burning was the practice that produced the highest total biomass and blockage factor, and therefore negatively influenced the water transport. However, this practice positively impacted seed retention and sedimentation. Our results suggest that associations of maintenance practices would preserve the trade-offs among the different functions in the medium term.