Herbaceous plant species and their combinations positively affect soil microorganisms and processes and modify soil physicochemical properties in a mesocosm experiment

Abstract

Although herbaceous plant species have the potential to affect soil abiotic and biotic properties, and thus ecosystem processes, they still remain an underappreciated component of forest ecosystems. We performed an outdoor pot experiment to assess the influence of four herbaceous plant species and their combinations on beech and riparian forest soils. The following plant cover treatments were used in the experiment: (1) bare (unplanted) soil, (2) Aegopodium podagraria, (3) Allium ursinum, (4) Anemone nemorosa, (5) Ficaria verna, (6) two-species combination (A. podagraria + A. ursinum), and (7) four-species combination. After 15 months of the experiment, the soils were collected from the pots and analyzed for microbiological properties, i.e., basal respiration, substrate-induced respiration (SIR), phospholipid fatty acid (PLFA) concentrations, enzymatic activity, and physicochemical properties, including moisture, pH, total and available nutrient contents. Herbaceous plants strongly influenced beech and riparian forest soils. Plant growth, either in monocultures or in combinations, resulted in high microbial performance. On the contrary, bare soils were characterized by the lowest values of many microbial indices. Overall, species combinations and A. podagraria had the strongest positive effects on microbes and processes, though the latter mainly in riparian soil; they increased PLFA-biomass (total, bacteria, G+ and G- bacteria, saprotrophic fungi), SIR-biomass, soil respiration, acid phosphatase, alkaline phosphatase, arylsulfatase, and/or urease activity. Plant species combinations and A. podagraria (in riparian soil) also stood out from other treatments in their effects on soil physicochemical properties, decreasing soil water content and the availability of some nutrients (N-NO3, P-PO4). Moreover, A. podagraria increased organic C and total N in riparian soil. Concluding, our experiment showed that the presence of herbaceous plant species positively influences microbes in beech and riparian forest soils, and this effect becomes stronger as plant species diversity increases. Herbaceous plant species are an important component of temperate forests because they play a significant role in supporting soil microorganisms and processes, maintaining soil health in these ecosystems. As such, they should be included in forest management practices.