Fertilizer-induced soil carbon rapidly disappears after clearcutting in boreal production forests

Abstract

Forests have a substantial potential to contribute to climate change mitigation, depending on how they are managed. Forest fertilization with nitrogen is used to increase tree productivity in Fennoscandian forests, but it can also increase soil carbon stocks. However, such forests are often harvested through clearcutting, a practice known to impact soil carbon stocks, nitrogen mineralization and biodiversity. To test whether fertilizer-induced soil carbon stocks are persistent, we studied post-clearcut soil carbon and nitrogen stocks, soil respiration, tree growth, ground vegetation and soil fungal communities in 48 previously fertilized and unfertilized production forests in central Sweden. In the first year after clearcutting, clearcuts of previously fertilized forests stored 7 t (+30%) more carbon and 210 kg (+32%) more nitrogen per hectare in the soil organic layer than clearcuts of unfertilized forests. Four to 13 years after clearcutting, there was no significant difference in carbon and nitrogen stocks of the organic layer, or in soil CO2 efflux, between clearcuts of previously fertilized and unfertilized forests. Saprotrophic ascomycetes were more abundant in clearcuts of previously fertilized forests, independent of time since clearcutting. Previous fertilization did neither result in increased growth of regenerating trees nor alter understory vegetation. Synthesis and applications. Overall, the carry-over effects on biodiversity from forest fertilization into stands regenerating after clearcutting were limited. We conclude that soil organic carbon stores induced by fertilization are short-lived and do not persist after clearcutting. Consequently, the potential of forest fertilization to mitigate climate change is likely limited to increases in aboveground biomass and the products that can be produced with the harvested biomass. Our study raises questions about where the added nitrogen and the fertilizer-induced increase in soil carbon have ended up-knowledge that is essential for making well-informed decisions about future fertilization strategies.& Ouml;kad kolinlagring i skog har potential att bidra till att begr & auml;nsa klimatf & ouml;r & auml;ndringar, men omfattningen beror p & aring; hur skogen brukas. I Fennoskandien anv & auml;nds kv & auml;veg & ouml;dsling som en metod f & ouml;r att & ouml;ka skogsproduktionen. F & ouml;rutom att fr & auml;mja tr & auml;dens tillv & auml;xt kan g & ouml;dsling & auml;ven bidra till att & ouml;ka markens kollager. Den vanligaste avverkningsmetoden i Fennoskandien & auml;r kalavverkning, vilket p & aring;verkar markens kollager, kv & auml;vemineralisering och biologisk m & aring;ngfald. F & ouml;r att unders & ouml;ka de l & aring;ngsiktiga effekterna av g & ouml;dsling p & aring; kollagring studerade vi hur markens kol- och kv & auml;velager, markrespiration, tr & auml;dtillv & auml;xt samt sammans & auml;ttningen av markvegetation och svampsamh & auml;llen skilde sig efter kalavverkning mellan 24 tidigare g & ouml;dslade och 24 og & ouml;dslade produktionsskogar i centrala Sverige. Under det f & ouml;rsta & aring;ret efter avverkning inneh & ouml;ll det organiska markskiktet p & aring; hyggen fr & aring;n tidigare g & ouml;dslade skogar i genomsnitt 7 ton mer kol (+30 %) och 210 kg mer kv & auml;ve (+32 %) per hektar j & auml;mf & ouml;rt med hyggen fr & aring;n og & ouml;dslade skogar. Fyra till tretton & aring;r efter avverkning fanns det inga signifikanta skillnader i kol- och kv & auml;velager i det organiska markskiktet eller i markens CO2-avg & aring;ng mellan hyggen fr & aring;n tidigare g & ouml;dslade och og & ouml;dslade skogar. Oberoende av tid sedan avverkning var Saprotrofa spors & auml;ckssvampar mer vanligt f & ouml;rekommande p & aring; hyggen fr & aring;n tidigare g & ouml;dslade skogar. Tidigare g & ouml;dsling gav inte upphov till & ouml;kad tr & auml;dtillv & auml;xt eller f & ouml;r & auml;ndrad markvegetation i n & auml;stkommande skogsgeneration. Syntes och till & auml;mpningar. De l & aring;ngsiktiga effekterna av skogsg & ouml;dsling p & aring; biologisk m & aring;ngfald in i n & auml;sta skogsgeneration & auml;r begr & auml;nsade. P & aring; samma s & auml;tt leder g & ouml;dsling inte till en varaktig & ouml;kning av kolf & ouml;rr & aring;det i det organiska markskiktet. Vi drar d & auml;rf & ouml;r slutsatsen att potentialen f & ouml;r att l & aring;ngsiktigt & ouml;ka skogens kolf & ouml;rr & aring;d-och d & auml;rmed motverka klimatf & ouml;r & auml;ndringar-genom konventionell skogsg & ouml;dsling sannolikt & auml;r begr & auml;nsad till en & ouml;kning av kolf & ouml;rr & aring;det i ovanjordisk biomassa fram till avverkning samt i de produkter som framst & auml;lls fr & aring;n den avverkade biomassan. V & aring;r studie v & auml;cker fr & aring;gor om vart det tillsatta kv & auml;vet och den g & ouml;dselinducerade & ouml;kningen av markkolet tagit v & auml;gen - kunskap som beh & ouml;vs f & ouml;r att fatta v & auml;lgrundade beslut om framtida g & ouml;dslingsstrategier.

Keywords

boreal forests; clearcut harvesting; forest fertilization; soil carbon; soil fungi; soil respiration

Published in

Journal of Applied Ecology
2025
Publisher: WILEY

SLU Authors

• Boeraeve, Margaux

  • Department of Ecology, Swedish University of Agricultural Sciences
    

• Lindahl, Björn

  • Department of Soil and Environment, Swedish University of Agricultural Sciences
    

• Clemmensen, Karina

  • Department of Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences
    

• Strengbom, Joachim

  • Department of Ecology, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Ecology

Publication identifier

• DOI: https://doi.org/10.1111/1365-2664.70034

Permanent link to this page (URI)

https://res.slu.se/id/publ/141569