Nils Henriksson

I am a researcher at the department of Forest Ecology and Management (SLU, Umeå). I am a forest ecophysiologist, which means that I use element fluxes to study biological processes related to forest growth and ecosystem functioning. Because of this basis on physiological processes, like photosynthetic carbon assimilation, cellular respiration, root and mycorrhizal nitrogen acquisition and water uptake, stable isotope techniques are very useful.  My focus is tree carbon/nitrogen dynamics and interactions with mycorrhizal fungi, and I have used stable isotope tracers (13C, 15N, 2H) to study tree carbon partitioning, competition for nitrogen within common mycorrhizal networks, as well as tree water/nitrogen uptake strategies. I combine field experiments in various boreal forest systems, including long-term nitrogen addition experiments, with laboratory or greenhouse experiments where specific processes can be targeted with a greater degree of experimental control. 

Currently I am involved in several projects. One project makes use of an established long-term forest fertilization and tree-girdling experiment to quantify the impact of forest dieback (e.g. such as may be caused by an outbreak of bark beetles) on ecosystem carbon dynamics. Forest fertilization generally increases both forest biomass and soil carbon stock. The current project will test how much of this fertilization-induced soil carbon sequestration is retained in the case of forest dieback.
 
A second project is a small-scale study looking at how mycorrhizal fungi distribute their resources among multiple host trees. My colleagues and I recently showed that trees can compete within a mycorrhizal network by supplying the fungus with additional carbon (Henriksson et al., 2021a). The current study will test if there is also a spatial component to the distribution of mycorrhizal nitrogen. 
 
Other projects involve forest ecosystem responses to varying forms of nitrogen. Specifically, how the chemical and physical properties of organic and inorganic nitrogen affect the growth patterns and uptake strategies of trees. This is based on recent work that that showed how root uptake strategies were fundamentally different in a forest which received annual doses of inorganic nitrogen, compared to an untreated boreal forest where organic nitrogen forms dominate in the soil (Henriksson et al., 2021b).

2018-2021 - Post-doctoral researcher at the department of forest ecology and management, SLU, Umeå.

2013-2017 - Ph.D. student at the department of forest ecology and managment, SLU, Umeå. My supervisors were professors Torgny Näsholm, John Marshall, and Lasse Tarvainen. Thesis title: "Tree carbon partitioning, respiratory efficiency, and nitrogen acquisition"

Lutter, R., Henriksson, N., Lim, H., Blaško, R., Magh, R., Näsholm, T., Nordin, A.,
Lundmark, T., Marshall, J. (2021). Belowground resource utilization in monocultures and mixtures of Scots pine and Norway spruce. For Ecol Man 2021.

Henriksson, N., Franklin, O., Tarvainen, L., Marshall, J., Lundberg‐Felten, J., Eilertsen, L., Näsholm, T., 2021a. The mycorrhizal tragedy of the commons. Ecology Letters 24, 1215–1224. 
Henriksson, N., Lim, H., Marshall, J., Franklin, O., McMurtrie, R.E., Lutter, R., Magh, R., Lundmark, T., Näsholm, T., 2021b. Tree water uptake enhances nitrogen acquisition in a fertilized boreal forest – but not under nitrogen‐poor conditions. New Phytologist 
Henriksson, N., Marshall, J., Lundholm, J., Boily, Å., Boily, J., Näsholm, T., 2019. Improved in vivo measurement of alternative oxidase respiration in field‐collected pine roots. Physiol Plantarum 167, ppl.12910.
Henriksson, N., Tarvainen, L., Lim, H., Tor-Ngern, P., Palmroth, S., Oren, R., Marshall, J., Näsholm, T., 2015. Stem compression reversibly reduces phloem transport in Pinus sylvestris trees. Tree Physiol 35, 1075–1085.