Historic grazing enhances root-foraging plasticity rather than nitrogen absorbability in clonal offspring of Leymus chinensis

Abstract

Aims Plants with a history of overgrazing show trait-mediated legacy effects. These legacy effects strongly influence the growth dynamics and stress tolerance of plants, thus affecting ecosystem functioning. Long-term overgrazing has dramatic effects on plant growth and carbon assimilation via asexual propagation. However, the link between nitrogen (N) absorbability and assimilation with grazing-induced plant legacy effects remains largely unknown. Methods We investigated the strength of legacy effects induced by long-term overgrazing on N uptake and metabolism in the clonal plant Leymus chinensis, and its associated changes at the physiological and molecular levels. These tests were conducted in both field and greenhouse experiments. Results The clonal offspring of overgrazed L. chinensis were significantly smaller than the control offspring, with lower individual N uptake and utilisation efficiency, indicating that the N dynamics were affected by plant legacy effects. The response ratios of root length and biomass to N patches in the clonal offspring of overgrazed L. chinensis were significantly higher than those of the control, indicating that root nutrient foraging plasticity increased in response to grazing-induced N heterogeneity. Moreover, the observed plant legacy effects decreased N acquirement but significantly increased N assimilation by increasing N resorption efficiency, with biotic stress memory activated at the enzymatic and transcriptional levels. Conclusions We propose that multigenerational exposure of perennial plants to herbivore foraging can produce a legacy effect on N uptake, which offers insights into the potential resilience of grasslands to overgrazing.