The effect of livestock grazing on plant diversity and productivity of
mountainous grasslands in South America - a meta-analysis
Abstract
Mountainous grasslands in South America represent highly diverse
ecosystems that offer a broad spectrum of benefits to people. These
include the regulation and purification of water, prevention of soil
erosion, provision of livestock feed, and preservation of cultural
heritage. Previous research has underscored the significant role of
grazing in shaping the diversity and productivity of grassland
ecosystems, particularly in highly productive, eutrophic systems. In
such systems, grazing has been demonstrated to restore grassland plant
diversity by reducing primary productivity. However, it remains unclear
whether these findings are applicable to South American mountainous
grasslands, where plants are adapted to different environmental
conditions. To address this gap, we conducted a meta-analysis of
experiments that excluded livestock grazing. The goal was to quantify
the impact of grazing exclusion on plant diversity and productivity
across mountainous grasslands in South America. Our findings, akin to
studies conducted in temperate grasslands, revealed that herbivore
exclusion led to an increase in aboveground biomass. Nevertheless, it
also resulted in a reduction in species richness and Shannon diversity.
Interestingly, the effects of grazing exclusion became more pronounced
with longer exclusion durations, yet remained robust to various climatic
conditions, including mean annual precipitation and mean annual
temperature, as well as the evolutionary history of grazing. In contrast
to results observed in temperate grasslands, the reduction in species
richness due to herbivore exclusion was not correlated with increased
aboveground biomass. This suggests that the processes regulating
(sub)tropical grassland plant diversity may differ from those in
temperate grasslands. Further research is imperative to better
comprehend the specific factors influencing plant diversity and
productivity in South American montane grasslands and to discern the
ecological implications of herbivore exclusion in these unique
ecosystems..