Mechanisms of nitrogen conservation at the leaf-level in annual and perennial desert forbs: Implications for perennial crops domestication

•Internal N cycling is relevant for yield stability and low addition of fertilizers.•We evaluated differences in N conservation between annual and perennial Physaria.•Perennials (low-SLA) lost 50% less N by senescence and had higher NUE than annuals.•This conservative strategy was linked to interannual biomass stability in perennials.•Annuals had more N productivity and PNUE, but both decreased in the dry year.