Our research deals with nitrogen nutrition of plants in general and of forest plants in particular. Nitrogen, being the mineral element needed in largest amounts by plants is also, in most terrestrial ecosystems, limiting for plant growth. In boreal forest ecosystems, this limitation is in spite of large stocks of organic nitrogen in the soil. Thus, the production of plant available nitrogen sources is a key process in these forests.
But which are the plant available nitrogen sources? What sources of nitrogen do plants actually use? Using a broad array of techniques, we are trying to answer this question. With the help of dual (C-13, N-15) labelled amino acids we have quantified uptake of intact amino acids in various plants directly in the field. Many researchers in various ecosystems now use this technique. We have characterized the mechanisms enabling for plants to absorb amino acids. These findings enable for us to produce plants with drastically altered capacities for amino acid uptake, plants that can be used to study the importance of amino acids as nitrogen sources in various soils. Our research deals also with carbon-nitrogen interactions in plants and the role of nitrogen for root:shoot allocation. It is well known that nitrogen availability is a strong determinant of root:shoot allocation of plants. But what roles do the different nitrogen compounds in the soil play for allocation of carbon between above- and belowground compartments and in shaping plant structures? These questions are targeted in new projects within the ecophysiology subject area.
Because of the strong nitrogen limitation of forests in our part of the world, nitrogen fertilization usually results in substantial growth increases. The practice of adding nitrogen to forests has received increased attention recently, an interest driven by the strong demand for biomass from different sectors. Our research will provide the basic knowledge for understanding how trees react to increased nitrogen availability and help develop new fertilizers and new forests nitrogen management practises.