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

Wang, Ruzhen, Institute of Applied Ecology, Chinese Academy of Sciences, https://orcid.org/0000-0001-8654-6677

Cresswell, Tom, Australian Nuclear Science and Technology Organisation, https://orcid.org/0000-0002-5320-7553

Johansen, Mathew, Australian Nuclear Science and Technology Organisation

Harrison, Jennifer, Australian Nuclear Science and Technology Organisation

Jiang, Yong, Institute of Applied Ecology, Chinese Academy of Sciences

Keitel, Claudia, University of Sydney

Cavagnaro, Timothy, University of Adelaide

Dijkstra, Feike, University of Sydney

ruzhenwang@iae.ac.cn, tomc@ansto.gov.au, mjo@ansto.gov.au, jjh@ansto.gov.au, jiangyong@iae.ac.cn, claudia.keitel@sydney.edu.au, timothy.cavagnaro@adelaide.edu.au

Published Oct 09, 2021 on Dryad. https://doi.org/10.5061/dryad.dbrv15f21

Cite this dataset

Wang, Ruzhen et al. (2021). Re-allocation of nitrogen and phosphorus from roots drives regrowth of grasses and sedges after defoliation under deficit irrigation and nitrogen enrichment [Dataset]. Dryad. https://doi.org/10.5061/dryad.dbrv15f21

Abstract

1. Re-allocation of nutrients from roots to shoots is essential for plant regrowth in grasslands, particularly in nutrient-poor conditions. However, the response of root nutrient re-allocation to changes in nitrogen (N) and water availability remains largely unknown.

2. Using a novel ¹⁵N and ³²P labelling technique, we quantified the contribution of N and phosphorus (P) to shoot regrowth from either root re-allocation or direct soil uptake for perennial grasses exposed to high-frequency deficit irrigation (HFDI) and N addition.

3. Without N addition, HFDI showed no impact on uptake and re-allocation 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 re-allocation with N addition, possibly due to exhaustion of nutrient reserves in roots that were re-allocated aboveground. Re-allocation contributed 48-97% of N and 58-79% of P required during the first two weeks of shoot regrowth.

4. Synthesis. Our results highlight the importance of N and P re-allocation from roots to buffer against changes in soil N and P availability and to maintain N:P ratio in shoot regrowth.