I am a PhD student at the department of Forest Ecology and Management. My supervisors are professors Torgny Näsholm and John Marshall, and Lasse Tarvainen. My research topics revolve around the ecophysiology of boreal forest trees - their carbon use and allocation, nitrogen uptake, and mycorrhizal interactions.
I am a PhD student studying tree carbon allocation from an ecophysiological perspective. After developing a reversible method for controlling tree belowground carbon transport, “stem compression”, I am looking at how lowered carbon supply to roots, affect tree nitrogen uptake. Stem compression is a simple procedure: attach a strong steel band around a tree’s stem and tighten it to collapse the phloem, pinching it against the hard underlying sapwood. The main advantage of this technique is that the phloem recovers its function after the bands are removed. Where girdling was previously the main method for manipulating tree belowground carbon transport, the reversibility of stem compression provides exciting possibilities for future studies within a range of topics (mycorrhizal interactions, tree nutrition, root competition, root exudation, photosynthetic control).
I am also interested in root respiration, since much of the carbon that a tree allocates to belowground structures is respired without being incorporated into root or mycorrhizal biomass. Here I am focusing on the portion of root respiration that occurs via the alternative respiratory pathway (AOX, for short).
AOX does not occur in mammals’ cellular respiration, but plants and fungi both have it. Since AOX does not conserve energy, but instead dissipates it as heat. Some plant species can increase their AOX activity enough to heat up their flowers to 30°C above ambient air temperature, in order to attract pollinators.
Most plants cannot generate this amount of heat, but AOX still plays an important role in physiological stress responses. Since it does not conserve energy, AOX can potentially reduce trees’ carbon use efficiency under conditions when it is more active. Tree carbon use efficiency is directly related to net primary production and carbon sequestration.
Henriksson N, Tarvainen L, Lim H, Tor-Ngern P, Palmroth S, Oren R, et al. Stem compression reversibly reduces phloem transport in Pinus sylvestris trees. Tissue D, editor. Tree Physiol. 2015 Oct;35(10):1075–85.