Year-round rhythms: alpine plant species modulate soil and microbial dynamics during the growing season and under the snow.

Abstract

O_LISoil-plant-microbe interactions are integral throughout most terrestrial ecosystems, yet the importance of plant phenology and seasonal dynamism upon these relationships remains unknown. Given the pronounced seasonality of alpine environments, we sampled 8 plant species occurring in two habitats (alpine meadow and subnival zone) across four seasons (including snow-covered winter) in the Central Eastern Alps to determine the plant growth strategies and plant nutrient parameters which closely couple with rhizosphere microbial parameters. C_LIO_LIIn subnival locations, plants exhibited stronger seasonal changes among leaf and root tissue nutrient concentrations and non-structural carbohydrates (NSCs) compared to those in lower elevation alpine meadows. However, rhizosphere microbial parameters (microbial biomass (MBC), extracellular enzymes, and community composition) demonstrated more seasonal changes in the alpine meadow locations. C_LIO_LIA phenological delay was observed in bacterial and fungal communities of the subnival zone, with peak plant rhizosphere differentiation occurring later in the season than in alpine meadows. Therefore, the prolonged cold conditions and shorter growing season in higher elevations likely add a temporal aspect to the commonly used elevational gradient approach, which is not often considered. C_LIO_LIMBC and enzymatic potential within the rhizosphere were high across all plant species in the alpine meadow during the winter sampling, despite notable differences in microbial community composition. In contrast, winter rhizosphere communities did not differ between plant species in subnival locations, although one species, Oxyria digyna, demonstrated much higher microbial activity along with higher NSCs and root N, suggesting some alpine plant species may acquire nutrients through microbial interactions during snow-covered winter periods. C_LIO_LISynthesis: This study provides the first look at the annual phenology of multiple alpine plant species and their associated rhizosphere microbiome. Our results demonstrate that seasonal microbial dynamics are highly influenced by abiotic factors (soil and microclimatic conditions), but plants are able to modulate these conditions through growth and nutrient acquisition strategies. Taken together, seasonality and independent plant species effects cannot be overlooked when assessing habitat nutrient cycling and ecosystem stability. C_LI