Changes in management modify agro-diversity in sainfoin swards in the Eastern Pyrenees

Abstract

Management affects ecosystem structure in many ways. Structural changes in ecosystems, including shifts in vegetation composition and species diversity, will affect the goods and services provided at ecosystem and regional scales. This is relevant for agricultural production and agro-biodiversity preservation in the context of management changes currently occurring in many regions. We sampled 39 sainfoin swards in the Eastern Pyrenees to assess changes in vegetation structure with sward management and evaluated how those changes might sustain agro-diversity regionally. Three sward managements coexist in the region: (a) mown plus sheep-grazed, (b) mown plus cattle-grazed and (c) only mown. Plant species composition and richness, and various biomass variables were estimated at peak biomass on swards with the three managements and different ages. We used a synchronic approach to study time effects, in which swards of different ages are sampled simultaneously, in a space by time substitution. Multivariate analysis and similarity indices revealed strong shifts in vegetation composition with management, enhanced with sward age, when the suppressive effect of sown on unsown plants relaxed. Generally, plant species richness increased with time. Old mown swards showed the highest number of species per plot (34 in 4 m2). Cattle-grazed swards showed the highest within- and between-treatment vegetation dissimilarity with time. Biomass variables responded mainly to time effects, but total aboveground biomass decreased with unsown species and increased with species richness depending on management. Thus, the diversity of managements modified the expected outcome in local and regional agro-diversity and sward structure. Our results are novel because they demonstrate strong effects of grazing by different animals on local and regional agro-diversity and herbage composition in those ephemeral legume-based forage systems. Farmers and managers should take into account those shifts in order to achieve agricultural goals, including agro-diversity conservation and sustainable forage production at ecosystem and regional scales.