Print PageCompositional stability in agronomic systems may be affected by several factors including species identity, temporal variation and climatic effects. To measure these effects, a large agro-diversity experiment was conducted at 31 sites across Europe and 1 site in Canada over a three year period. At each site two grasses and two legumes were sown in either monoculture or in four-species mixtures and at either low or high density according to a simplex design. The two species within the grass and legume functional groups were comprised of one fast and one slow establishing species. The sown proportions of the four-species mixtures were either equal proportions of each species, domination by one species or co-domination by two species. The biomass (dry matter production) of each species and of unsown species was recorded at each site for a three year period. Relative growth rate difference mixed model analysis was used to examine how community compositions (the biomass and growth rates of the species and of the functional groups) changed over the three year period and how compositions were affected by the climatic gradient of the wide geographic experimental region.
Results/Conclusions
For mixtures plots, grasses became the dominant functional group on average across sites, attaining 50% at sown and 58%, 68% and 74% of total biomass at year 1, 2 and 3 respectively. The growth of the fast-growing grass species was largely the cause of this domination of grasses by year 3. Extreme air temperature conditions had an effect on the growth rates of species; lower annual minimum air temperature favoured the growth rate of unsown species over each of the sown species. Higher annual rainfall favoured the growth of legumes over both grasses and unsown species. Knowledge of how agronomic systems are affected by climate may lead to enhanced management practices to increase stability of community compositions over time and give indications of how these systems will respond to climate projected for the future.
