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

Aims Trait-mediated legacy effects of plants subject to land use history can strongly influence tolerance and growth dynamics of grassland plants, thus impacting ecosystem functioning. Long-term overgrazing has strong effects on plant growth and carbon assimilation via asexual propagation. However, the links between nitrogen (N) cycling and grazing-induced plant legacy effects are largely unknown.
Methods We tested the strength of plant legacy effects of long-term overgrazing on N 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 N utilization efficiency, indicating that the N dynamics were impacted by plant legacy effects. The response ratios of root traits 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 to cope with grazing-induced N heterogeneity. Moreover, the observed plant legacy effect slightly decreased N absorbability in roots but significantly increased N assimilation capacity, by increasing N resorption efficiency in particular, 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 nutrient uptake, which offers insights into the potential resilience of grasslands to overgrazing.