Data from: Contrasting responses of nitrogen: phosphorus stoichiometry in plants and soils under grazing: a global meta-analysis

<p>1. Grazing by ungulate herbivores can greatly alter nitrogen ([N]) and phosphorus ([P]) concentrations in plants and soils. It is not clear, however, how grazing might affect N:P co-limitation in grasslands depending on soil N and P availability.</p> <p>2. Here we selected 173 peer-reviewed studies, which measured 12 key variables associated with changes in [N], [P] and N:P ratios (i.e. N:P stoichiometry) in soils and plants in the presence or absence of herbivore grazing. Subsequently, we addressed the magnitude and direction of grazing effects on these variables using a meta-analysis approach.</p> <p>3. Grazing increased leaf [N] and [P] but decreased total and available soil [N] and [P]. Grazing also increased leaf N:P ratios while decreasing root and total soil N:P ratios.</p> <p>4. The response ratio (RR) of leaf N:P was negatively correlated with RR of plant-available soil [P] and positively correlated with RR of available soil N:P ratio (rather than with RR of total soil N:P).</p> <p>5. Intensive grazing (e.g., heavy grazing or long-term grazing) had in general more positive effects on plant N:P stoichiometry and negative effects on soil N:P stoichiometry than light grazing. Responses of plant-soil N:P stoichiometry to grazing greatly varied depending on plant functional group identity, plant organizational level (i.e. species and community) and grassland type.</p> <p>6. Synthesis and applications. Our study suggests that understanding changes in available soil N:P stoichiometry (rather than total soil N:P) in response to grazing is crucial to predict nutrient co-limitation in grassland biomes. Our findings show that P is more important for plant growth than generally thought due to greater reduction of plant-available soil [P] under grazing. A better mechanistic understanding of the relationships between plant and available soil N:P stoichiometry under grazing will greatly help improve the sustainability of natural and semi-natural grassland ecosystems.</p>