Intra-specific multi-trait approach reveals scarce ability in the variation of resource exploitation strategies for a dominant tall-grass under intense disturbance

Mowing is a suitable practice to restore the grassland coenological composition after invasion of tall-grasses. However, how it affects the tall-grass intraspecific variation is still unknown. We investigated if mowing decreases the competitive ability of the tall-grass Brachypodium rupestre, and if this reduction is due to its poor ability to adapt to the new conditions by reducing resource investment in leaf and flower production, resource storage in belowground organs, increasing seed output and reducing seed mass. In 2017, we measured vegetative and reproductive traits of B. rupestre in two fenced areas in central Apennines (Italy). Half of each area had been mown twice a year since 2010 and half remained unmown. To investigate the effect of mowing on B. rupestre's functional strategies, we used linear mixed-effects modelling and correlation analysis. Mowing significantly reduced the trait values related to competitive ability/resource acquisition (vegetative height and leaf traits), resource storage (mature hypogeogenous rhizome), and sexual reproduction (mean seed mass, number of flowers, reproductive height), but increased seed output. We did not find significant variation of dry matter content in epigeogenous rhizomes and in the shoot number. B. rupestre is not prone to endure a prolonged disturbance, not being able to reallocate resources from acquisitive and retentive to reproductive structures. However, it is able to guarantee the presence of individuals to a certain degree by changing the reproductive strategies, such as decreasing the seed mass and increasing the seed output.