Nitrogen isotope enrichment predicts growth response of Pinus radiata in New Zealand to nitrogen fertiliser addition

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dc.contributor.authorGarrett, Loretta G.en
dc.contributor.authorLin, Yueen
dc.contributor.authorMatson, Amanda L.en
dc.contributor.authorStrahm, Brian D.en
dc.date.accessioned2023-05-02T13:42:26Zen
dc.date.available2023-05-02T13:42:26Zen
dc.date.issued2022-10en
dc.description.abstractThe fertiliser growth response of planted forests can vary due to differences in site-specific factors like climate and soil fertility. We identified when forest stands responded to a standard, single application of nitrogen (N) fertiliser and employed a machine learning random forest model to test the use of natural abundance stable isotopic N (delta N-15) to predict site response. Pinus radiata growth response was calculated as the change in periodic annual increment of basal area (PAI BA) from replicated control and treatment (similar to 200 kg N ha(-1)) plots within trials across New Zealand. Variables in the analysis were climate, silviculture, soil, and foliage chemical properties, including natural abundance delta N-15 values as integrators of historical patterns in N cycling. Our Random Forest model explained 78% of the variation in growth with tree age and the delta N-15 enrichment factor (delta N-15(foliage) - delta N-15(soil)) showing more than 50% relative importance to the model. Tree growth rates generally decreased with more negative delta N-15 enrichment factors. Growth response to N fertiliser was highly variable. If a response was going to occur, it was most likely within 1-3 years after fertiliser addition. The Random Forest model predicts that younger stands (< 15 years old) with the freedom to grow and sites with more negative delta N-15 isotopic enrichment factors will exhibit the biggest growth response to N fertiliser. Supporting the challenge of forest nutrient management, these findings provide a novel decision-support tool to guide the intensification of nutrient additions.en
dc.description.notesOpen Access funding enabled and organized by CAUL and its Member Institutions. Funding for this research came from the New Zealand Forest Growers Levy Trust Inc (QT-7272).en
dc.description.sponsorshipNew Zealand Forest Growers Levy Trust Inc [QT-7272]; CAULen
dc.description.versionPublished versionen
dc.format.mimetypeapplication/pdfen
dc.identifier.doihttps://doi.org/10.1007/s00374-022-01671-8en
dc.identifier.eissn1432-0789en
dc.identifier.urihttp://hdl.handle.net/10919/114882en
dc.language.isoenen
dc.publisherSpringeren
dc.rightsCreative Commons Attribution 4.0 Internationalen
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/en
dc.subjectGrowth responseen
dc.subjectFertiliseren
dc.subjectNitrogenen
dc.subjectNatural abundance nitrogen isotopeen
dc.subjectMachine learningen
dc.subjectPinus radiataen
dc.titleNitrogen isotope enrichment predicts growth response of Pinus radiata in New Zealand to nitrogen fertiliser additionen
dc.title.serialBiology and Fertility of Soilsen
dc.typeArticle - Refereeden
dc.type.dcmitypeTexten

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