1 research outputs found
Plant diversity and botanical composition in an Atlantic heather-gorse dominated understory after horse grazing suspension: Comparison of a continuous and rotational management
Floristic diversity changes substantially depending on the type of land management. We
evaluated the impact of a continuous (CG) and rotational (RG) grazing system on the
dynamics of plant diversity and community composition in a heather-gorse understory
after a two and six-year pause from horse grazing. Previously grazed sites had higher total
and rare species richness and diversity than ungrazed (UN), regardless the type of grazing
system. The positive impact of previous grazing on species richness was higher in CG and
continued after six years in both grazing systems. Seven species of high conservation interest in heathlands were present in the studied areas. Most of them were associated to CG
management and none was exclusively in RG. The reduction of the shrub component by
previous horse grazing led to a decrease of gorse dominance, thus potentially reducing fire
risk and increasing plant diversity. The extent of the positive effect of horse grazing controlling excessive accumulation of combustible material and favoring species richness
differed when relative abundance of species, and not solely the number of species, was
taken into account (Simpson’s dominance increased and Pielou’s evenness decreased after
six years). Overall, the effects of previous rotational and continuous grazing on plant diversity in an Atlantic heather-gorse dominated plant community were still apparent 2 or 6
years after grazing interruption, although declined after the six-year grazing interlude.
Rotational management revealed a slight advantage upon the control of gorse biomass
long term, and assisted to maintain the relative abundance of species more evenly over
time. The alpha and beta diversity indices confirmed that plant diversity similarity between rotational and continuous management increased after six yearsConstantino Arce provided valuable assistance in developing contingency tables for analyzing statistic associations of plant species with experimental conditions. The authors would like to thank the anonymous reviewers for their highly valuable comments that significantly helped to improve this manuscript.The previous grazing experiment, from which the current study was later developed, was funded by the Spanish ComisiĂłn Interministerial de Ciencia y TecnologĂa (AGF 98-0368) and by the Rural Development Galician Government (Xunta de Galicia).S