Predicting agronomical and ecological effects of shifting from sheep to cattle grazing in highly dynamic Mediterranean dry grasslands

Abstract

AbstractIn the recent decades, cattle numbers strongly increased whereas sheep numbers decreased in south Portugal. This paper aims to predict the potential agronomical and ecological effects of these trends and clarify about the versatility of cattle and sheep systems in adapting to climate changes in the Mediterranean basin. We monitored livestock management in the dry grasslands of Évora (2012 to 2016) and investigated for the effect of livestock type (TLivest) on (a) sward's characteristics, (b) vegetation taxonomic diversity, and (c) in conforming vegetation communities and promoting species of agronomical interests (SAIs). Generalized linear mixed models were used to link management descriptors and vegetation parameters with TLivest. Redundancy analysis was used to analyse the changes due to TLivest on floristic composition and SAIs. Sheep fields presented (a) higher number of days under grazing and lower instantaneous stocking rates than cattle or mixed fields and (b) lower vegetation height in April in wet years and higher green vegetation cover in May; α‐ and γ‐diversity were poorly related with TLivest, but β‐diversity was lower under mixed grazing than under sheep or cattle grazing. The highest richness of legume species was found in permanent grasslands grazed by sheep. Redundancy analysis provided a good discrimination of TLivest but a poor segregation of vegetation communities. As a conclusion, sheep grazing can be seen as a more powerful tool to increase sward heterogeneity, and thus, a loss of grassland heterogeneity can be expected under cattle grazing. The lower versatility of cattle systems suggests narrower opportunities in adapting to climate change.