Trenching-experiment
Near tower in three replicate locations, trenching plot experiment was established in the summer-autumn 2012. The principle of the experiment is to limit energy flow, in form of photosynthetically fixed carbon, in the trenching plots and by doing that, separate soil autotrophic and heterotrophic respiration. Additionally, it is possible to investigate how changes in plant-derived energy flow in soil affect production of other ghses, like methane and VOCs. In total, 36 trenched plots and 24 controls were established.
In trenched plots, 40 cm deep trenches were dug to cut the great majority of living tree root connections to the 90 cmx 90cm plots. In many cases, bed rock was reached. In the trenches, either a fabric consisting of 1 µm mesh or 50 µm mesh were installed to prevent any root in-growth. 50 µm mesh allows fungal hyphae to grow throuhg but this is prevented by 1 µm mesh. After installing the fabrics, the trenches were re-filled and removed ground vegetation re-planted.
In addition to two different kinds of mesh size used, three different vegetation treatments were established. As in most trenching experiment, one of the vegetation treatment is the complete removal of any photosynthetically active ground vegetation (mosses, dwarf shrubs etc.). By removing all vegetation, also other than tree-derived carbon flux to the plots will be removed. In the second vegetation treatment, all other plants but dwarf shrubs (e.g. Calluna vulgaris, Vaccinium vitis-ideae and V. myrtillus) were removed and in the third treartment, all ground vegetatios was left intact in the plot. With corresponding non-trenched controls, alltogether nine (9) different kinds of plots were establised, the replicate number being 6-12. Soil temperature and moisture will be measured during growing season to allow estimation of their influence on gas fluxes.
The experiment will be continuing for several years, the summer 2013 being the first one when any CO2- or other gas measurement will be conducted. During the experiment, CO2 will be measured continuously, CH4, VOCs and N2O and NOx in campaigns.