Data from: Livestock activity increases exotic plant richness, but wildlife increases native richness, with stronger effects under low productivity

1.Grazing by domestic livestock is one of the most widespread land uses
worldwide, particularly in rangelands, where it co-occurs with grazing by
wild herbivores. Grazing effects on plant diversity are likely to depend
on intensity of grazing, herbivore type, coevolution with plants and
prevailing environmental conditions. 2.We collected data on climate, plant
productivity, soil properties, grazing intensity and herbivore type; and
measured their effects on plant species richness from 451 sites across 0.4
M km2 of semi-arid rangelands in eastern Australia. We used structural
equation modelling to examine the direct and indirect effects of
increasing grazing intensity by different herbivores (cattle, sheep,
kangaroos, rabbits) on native and exotic plant species richness across all
sites, and in subsets focusing on three woodland communities spanning a
gradient in productivity. 3.Direct effects of grazing by all herbivores
were strongest under low productivity but waned with increasing
productivity. Increases in the intensity of recent and historic livestock
grazing corresponded with greater exotic plant richness under low
productivity and less native plant richness under both low and moderate
productivity. Rabbit effects were greatest under moderate productivity.
Overall effects of kangaroos were benign. Grazing indirectly affected
native and exotic plant richness by increasing soil phosphorus and
reducing soil health (i.e., nutrient cycling). 4.Synthesis and
applications. Our study shows that livestock grazing increases exotic
species richness but reduces native richness, while kangaroo grazing
increases native richness in environments with low productivity. The
results provide clear messages for land managers and policy makers: (1)
the coexistence of livestock grazing and plant diversity is only possible
within more productive environments and (2) grazing under low or moderate
productivity will impact upon native and exotic plant richness.