01641nas a2200157   4500008004100000245009400041210006900135300001100204490000900215520109300224100002401317700002401341700002301365700002101388856007401409       2019                        eng d00aA distributed experiment demonstrates widespread sodium limitation in grassland food webs0 adistributed experiment demonstrates widespread sodium limitation  ae026000 v71133 a<p>Sodium (Na) has a unique role in food webs as a nutrient primarily limiting for plant consumers, but not other trophic levels. Environmental Na levels vary with proximity to coasts, local geomorphology, climate, and with anthropogenic inputs (e.g., road salt). We tested two key predictions across 54 grasslands in North America: Na shortfall commonly limits herbivore abundance, and the magnitude of this limitation varies inversely with environmental Na supplies. We tested them with a distributed pulse experiment and evaluated the relative importance of Na limitation to other classic drivers of climate, macronutrient levels, and plant productivity. Herbivore abundance increased by 45% with Na addition. Moreover, the magnitude of increase on Na addition plots decreased with increasing levels of plant Na, indicating Na satiation at sites with high Na concentrations in plant tissue. Our results demonstrate that invertebrate primary consumers are often Na limited and track local Na availability, with implications for the geography of invertebrate abundance and herbivory.</p>1 aWelti, Ellen, A. R.1 aSanders, Nathan, J.1 aBeurs, Kirsten, M.1 aKaspari, Michael  uhttps://esajournals.onlinelibrary.wiley.com/doi/full/10.1002/ecy.2600