%0 Articles
%T Linking water and carbon cycles: modeling latent heat exchange and dissolved organic carbon
%A Kasurinen, Ville
%D 2016
%J Dissertationes Forestales
%V 2016
%N 215
%R doi:10.14214/df.215
%U http://dissertationesforestales.fi/article/1999
%X Water and carbon cycles of the Earth are tightly linked to each other. One linkage of these cycles is through the water use efficiency of photosynthetic production its interactions with drought, and its possible changes. A second linkage between the water and carbon cycles: the transport of terrestrial carbon as dissolved organic carbon (DOC) to aquatic ecosystems has received much less attention and is, therefore, the subject of this thesis.

The thesis shows that latent heat exchange in boreal and arctic biomes differs, under similar climatic conditions, between different land cover types in the boreal and arctic climatic zones. Furthermore, we found that there are large differences in the way ecosystems are exchanging water in the winter and the summer. Winter time surface resistances were much higher and the transition between the winter and summer phenological stages was slow.

Similarly, stream water DOC concentrations show high temporal and spatial variability between different catchments in boreal landscapes and globally between big river systems. The model, developed
here and applied to a boreal catchment simulates stream water DOC concentrations as a function of catchment water storage, soil temperature and runoff. The model is parsimonious, i.e. all parameters
could be estimated statistically and it its performed better than previous models for the 18 partially nested sub-catchments of the Kryckland research area.

Finally, the contribution of terrestrial DOC promoting heterotrophic food webs in coastal waters was quantified after receiving a radiation dose corresponding UV-radiation absorbed by Earth’s surface in a month. Irradiation removed approximately half from the initial terrestrial chromophoric dissolved organic matter (tCDOM) suggesting that sun-light induced photochemistry is a significant sink of tCDOM
in coastal waters. Tropical rainforest covered large basins of Amazon and Congo Rivers contributed the highest production of biologically labile photoproducts (BLPs) and the highest tCDOM fluxes of investigated rivers, which might be linked to large water fluxes and carbon sequestration in their basins.

A strong relationship between photobleaching of tCDOM and bacterial production based on bioavailable labile photoproducts (BLPs) was found and used to estimate BLP production globally. Extrapolation
of production revealed that the majority of tDOC will be mineralized to CO2 either directly or through bacterial respiration in coastal waters. In these research articles, I have investigated biogeochemical
cycles of water and carbon focusing to latent heat exchange and DOC dynamics in landscapes, as well as, in coastal waters, describing their variability across space and time.