Contrasting patterns along tall grass dominance in mowed mountain grasslands

Semi-natural grasslands are a perfect system to study how biotic interactions influence coexistence thanks to their high species diversity in small areas resulting from millennia of anthropogenic management. Management cessation led to the increase of highly competitive tall-perennial tussock species with a marked drop of tax-onomical (TD) and functional diversity (FD). The effect of highly competitive tall-perennial tussock species on plant community under management condition is largely understudied. In this study, we try to shed light on the effect of Brachypodium genuense which dominates sub-Mediterranean abandoned mountain grasslands TD and FD. For FD, we selected as traits plant height (H), specific leaf area (SLA) and leaf area (LA). We hypothesized i) TD decreases as the cover of B. genuense increases; ii): H converges towards higher values resulting from weaker competitive exclusion; iii) SLA and LA diverge resulting from limiting similarity. TD and FD were calculated using Rao's Quadratic Entropy. We computed the community weighted mean (CWM) that we analysed with fourth corner approach and built linear models using B. genuense as a predictor. We found that B. genuense ability in dominating the grassland plant community is altered by mowing in two different ways. On one hand, increase of B. genuense lead to a drop in TD whereas for FD the increase showed contrasting patterns with divergence for H and convergence for SLA. On the other, there were changes in the main dominant strategies with an overall increase in mean trait values of both H and SLA indicating species taller in size and more fast-growing. Overall, our results highlighted how tall-perennial tussock species under mowing conditions lead to a more stratified plant community convergent towards resource acquisition strategies. A multifaceted approach should be adopted to have a better understanding of the biotic drivers on different aspect of plant community.

Automated summary

Semi-natural grasslands are a suitable system for studying the effects of biotic interactions on coexistence. However, the cessation of management has led to the dominance of highly competitive tall-perennial tussock species, resulting in a decrease in both taxonomic and functional diversity. This study examines the impact of Brachypodium genuense on plant community, and finds that it alters the community dynamics in terms of both diversity and dominant strategies, leading to a more stratified and resource-based plant community under mowing conditions.