Root seasonal pattern, spatial distribution, and C:N ratio of matgrasspasture (Nardus stricta L.) in the Lombardy Prealps

The aim of the present study was to investigate carbon and nutrient cycling and the role of root dynamics in terrestrial
ecosystems such as large abandoned pastures and natural grasslands present in the Prealps, for which below-ground
processes are currently enigmatic. In particular, we quantified root/leaf biomass and C:N ratio throughout two growing
seasons. Additionally, root traits such as root length density (RLD), root mass density (RMD), and root diameter classes
(RDC) were also investigated with the aim of understanding the spatial distribution of roots in the soil. In our samples, we
found that the roots could be divided into three main diameter classes and hence quantified the presence of each class along
the soil profile. With regard to total root biomass, we found the occurrence of two peaks of biomass accumulation during
the growth season, and when biomass accumulation was compared with climatic data, it was impossible to obtain a clear
indication of the root turnover rate. In fact, the strong influence of grazing on the above-ground biomass could have
affected, in turn, root biomass. In future, this possible complication will be avoided by repeating the measurements within
enclosures to avoid grazing interference. We found that C:N ratio remained constant, with a single peak, suggesting a lower
root decomposition during the warmest period (August 2006). The concentration of nitrogen in roots decreased with depth
as a result of a decrease in roots with smaller diameters. The reverse was found for carbon content, which increased with
depth, probably due to an increase in roots with larger diameters. This study represents the first attempt to estimate root
turnover rates in this prealpine ecosystem, which have been analysed to date only for the above-ground biomass.