Work package 4: Integrated experiments
The biogeochemical cycle in gaps in beech forests will be studied using a chronsequence approach, i.e. by substituting time for space. The principal factor to be studied is gap size. Studies will be carried out in existing gaps (with time series measurement) and newly created gaps, so that the range of gap sizes studied can be increased. Gaps of 4 sizes, within the natural range defined by WPs 1 and 2, will be studied. Existing study sites in two partner countries in SE and NW Europe (Denmark and Slovenia) will be expanded, and an additional site is to be included to study soil water dynamics. A total of 4 gaps (co-ordinated with WP 3) will be equipped in each of the two major partner countries.
Biogeochemical experimental design, analysis and modelling. Sampling will be based on a systematic grid system covering the surrounding forest and the gap. At some of the grid intersections a suction cup lysimeter (to determination of all essential elements in soil water), through-fall collector, soil temperature sensor, TDR sensor (to estimate soil water content), and equitensiometer (to estimate soil water potential) will be set up. Decomposition and nutrient release of surface litter (using the litter bag technique), and in situ net N-mineralization (using the buried-bag technique) will be estimated. The study of soil conditions in this integrated GAP-experiment requires relatively expensive equipment to collect soil water below the root zone. Soil water is sampled by means of suction cups installed in the mineral soil. A pump driven by a solar cell panel maintains a specific suction in the ceramic cups. The water is led through plastic tubes and collected in separate glass bottles sheltered in an insulated plastic box dug into the soil. Four such sets of 1-2 pumps, 20-30 suction cups, solar cell panels, wires, tubes etc. is needed for each of the two countries (Denmark and Slovenia) involved in this intensive experiment.
The data are synthesised into a soil water model for estimation of element fluxes in leaching water and results on leaching with regard to gap -size and microclimate. The output of this WP serves as input to the modelling exercises of WPs 8-10.
Sampling and analysis of mycorrhiza. The mycorrhizal activity will be estimated in soil samples as an integral part of the systematic grid system. As a part of the integrated design of WP3 and WP4, 20 soil samples will be taken in each of 2 gaps in Denmark and 2 gaps in Slovenia by a common sampling technique (274 ml bulk-samples of 0-20 cm top-soil within a 1 m2 sampling plot). The sampling will take place during the vegetation season in year 1 and 2. Fungal fruitbodies will be mapped in the same locations, exicates will be stored at the Herbarium at SFI and KVL.
20 soil samples per plot will be taken, from which 10 or more will be used for estimation of the length, area, volume, number and diameter classes of the roots using WinRhizo programme, while the other up to 10 soil cores will be used for identification of types of ectomycorrhizae by morpho/anatomycal method and comparisons to the PCR/RFLP database from fungal fruitbodies from the same locations.
Work-package leader:
Karsten Raulund-Rasmussen, Danish Forest and Landscape Research Institute (DFLRI)
Hørsholm Kongevej 11, DK-2970 Hørsholm, DENMARK, Fax: (+45) 4576 3233, phone: (+45) 4517 8223, e-mail:
Jens Emborg, - last update:8 March 2012