Sammanfattning

Global vegetation regimes vary in belowground carbon (C) and nitrogen (N) dynamics. However, disentangling large-scale climatic controls from the effects of intrinsic plant-soil-microbial feedbacks on belowground processes is challenging. In local gradients with similar pedo-climatic conditions, effects of plant-microbial feedbacks may be isolated from large-scale drivers. Across a subarctic-alpine mosaic of historic grazing fields and surrounding heath and birch forest, we evaluated whether vegetation-specific plant-microbial feedbacks involved contrasting N cycling characteristics and C and N stocks in the organic topsoil. We sequenced soil fungi, quantified functional genes within the inorganic N cycle, and measured N-15 natural abundance. In grassland soils, large N stocks and low C : N ratios associated with fungal saprotrophs, archaeal ammonia oxidizers, and bacteria capable of respiratory ammonification, indicating maintained inorganic N cycling a century after abandoned reindeer grazing. Toward forest and heath, increasing abundance of mycorrhizal fungi co-occurred with transition to organic N cycling. However, ectomycorrhizal fungal decomposers correlated with small soil N and C stocks in forest, while root-associated ascomycetes associated with small N but large C stocks in heath, uncoupling C and N storage across vegetation types. We propose that contrasting, positive plant-microbial feedbacks stabilize vegetation trajectories, resulting in diverging soil C : N ratios at the landscape scale.

Nyckelord

forest; fungal saprotrophs; grassland; heathland; mycorrhiza; N cycling; vegetation gradients

Publicerad i

New Phytologist
2023, Volym: 238, nummer: 6, sidor: 2621-2633

SLU författare

• Castaño Soler, Carles

  • Institutionen för skoglig mykologi och växtpatologi, Sveriges lantbruksuniversitet
    

• Hallin, Sara

  • Institutionen för skoglig mykologi och växtpatologi, Sveriges lantbruksuniversitet
    

• Lindahl, Björn

  • Institutionen för mark och miljö, Sveriges lantbruksuniversitet
    

• Clemmensen, Karina

  • Institutionen för skoglig mykologi och växtpatologi, Sveriges lantbruksuniversitet
    

Associerade SLU-program

SLU Nätverk växtskydd
SLU Skogsskadecentrum


Globala målen

SDG15 Ekosystem och biologisk mångfald


UKÄ forskningsämne

Ekologi


Publikationens identifierare

DOI: https://doi.org/10.1111/nph.18679

Permanent länk till denna sida (URI)

https://res.slu.se/id/publ/120378