Effects of haying on vegetation communities, taxonomic diversity and sward properties in mediterranean dry grasslands: A preliminary assessment

Abstract

In the last years, the use of haying is increasing in Southwest Iberia. However, information on its effects on grassland diversity or productivity is missing for Mediterranean dry environments. We examined the short-medium term effects of haying in Alentejo region, South Portugal. Our hypotheses were: (1) haying influences plant taxonomic diversity, floristic composition, herbage productivity and quality; (2) haying effects act both at the field and surrounding of a field levels, and depend on yearly weather conditions and on the type of hay produced. Floristic inventories were conducted from 2012 to 2015 (121 fields). Vegetation samples were collected from 2012 to 2014 (130 fields) and analyzed in laboratory for determination of above-ground biomass and crude protein content. GLMMs and model averaging were used to model the relationship between vegetation parameters and grassland management variables. Redundancy analysis was used to analyse compositional changes with a special focus on the species with agronomical interest. Annual variation and land use were generally better predictors of vegetation parameters than haying management variables, with the exception of β-diversity. Fields with higher area of haying in forage crops in the previous years presented significantly lower γ-diversity and in less extent, lower α-diversity, β-diversity and leguminous richness. β-diversity was positively influenced by haying in fallow land in the surrounding of the field. Leguminous richness and proportion were lower in fields with higher area of haying in fallow land in the previous years. Crude protein content depended on the interaction between year and area of haying in fallow land. In general, communities tended to be highly similar in their species composition, but most species of agronomical interest were negatively influenced by haying. We conclude that haying has an overall moderate effect in Mediterranean dry grasslands, and that it is difficult to design management practices that simultaneously conciliate plant diversity, leguminous richness/proportion and herbage quality.