Reallocation of nitrogen and phosphorus from roots drives regrowth of grasses and sedges after defoliation under deficit irrigation and nitrogen enrichment

Ruzhen Wang, Tom Cresswell, Mathew P. Johansen, Jennifer J Harrison, Yong Jiang, Claudia Keitel, Timothy R. Cavagnaro, Feike A. Dijkstra

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)

Abstract

Reallocation of nutrients from roots to shoots is essential for plant regrowth in grasslands, particularly in nutrient-poor conditions. However, the response of root nutrient reallocation to changes in nitrogen (N) and water availability remains largely unknown. Using a novel 15N and 32P labelling technique, we quantified the contribution of N and phosphorus (P) to shoot regrowth from either root reallocation or direct soil uptake for perennial grasses exposed to high-frequency deficit irrigation (HFDI) and N addition. Without N addition, HFDI showed no impact on uptake and reallocation of N and P, likely due to unaffected soil N availability and a greater diffusion barrier offsetting increased accumulation in plant-available soil P. With N addition, HFDI increased plant N rather than P uptake, because of increasing soil N availability instead of P under combined HFDI and N addition. The HFDI decreased both N and P reallocation with N addition, possibly due to exhaustion of nutrient reserves in roots that were re-allocated above-ground. Reallocation contributed 48%–97% of N and 58%–79% of P required during the first 2 weeks of shoot regrowth. Synthesis. Our results highlight the importance of N and P reallocation from roots to buffer against changes in soil N and P availability and to maintain N:P ratio in shoot regrowth.

Original languageEnglish
Pages (from-to)4071-4080
Number of pages10
JournalJournal of Ecology
Volume109
Issue number12
DOIs
Publication statusPublished - Dec 2021
Externally publishedYes

Keywords

  • nitrogen deposition
  • nutrient reallocation
  • nutrient stoichiometry
  • nutrient uptake
  • plant biomass production
  • plant–soil (below-ground) interactions
  • radioactive isotope labelling
  • water stress

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