Most of the plant diversity in European forests is found in the understorey, and despite its relatively low biomass compared to the forest overstorey, its functional importance is high (nectar source for pollinators, habitat for small mammals, affects tree regeneration, invasion resistance, decomposition and nutrient cycling (Gilliam 2007). Relationships between overstorey and understorey diversity and composition will be tackled. At the Satakunta sites in Finland, plots of 20m x 20m were established in 1999 in which the desired species mixture was achieved by mixing the species tree by tree (so no pattern of small monocultures next to each other) at planting. Vegetation was first monitored in 2003 by the team of Julia Koritcheva. In each plot 3 frames of 1m x 1m (= subplots)were randomly spread and the cover of each species within these frames was recorded. The exact location of these subplots was NOT determined nor marked. This experimental set-up was repeated in July 2011 by Evy Ampoorter and Kris Ceunen: 3 frames of 1m x 1m (vegetation subplots) were randomly located within each plot (however, big rocks were avoided) and following characteristics were recorded: percentage cover per species in the understorey layer (< 1.3m), total cover by understorey layer, other cover (litter, bare soil moss). A biomass sample was also taken: within the frame of 1m x 1m a smaller frame of 0.5m x 0.5m was placed at a location where vegetation was relatively abundant and composition was representative for the bigger frame (biomass subplot). All aboveground biomass within this smaller frame was clipped. Dead vegetation was removed from each biomass sample. For each first subplot per plot the biomass sample was also further subdivided into following groups: Epilobium angustifolium, Rubus idaeus, dwarf shurbs, grasses, seedlings, ferns, other herbs. After removal of death vegetation and eventual subdivision into groups, the biomass samples were dried for 24h at 70°C (samples were already dry when collecting). Then they were weighed and analysed for P, Ca, K, Mg (Forest & Nature Lab, Ghent University) and C/N (Institut für Walbau, Universität Freiburg). In each plot at 6 randomly spread locations a soil sample was also taken from the upper 10cm of the mineral layer (if possible; namely, very rocky soil and often very thick layer of accumulated organic material that could not be removed so that mineral soil layer could not be reached ; soil sampler could only sample to a depth of 10cm). These 6 samples per plot were thoroughly mixed and dried at 40°C for about a week (very wet!). Then they were analyzed for pH, K, Ca, Mg, C, N, S, total P and Olsen P (Forest & Nature Lab, Ghent University).

In each plot at 6 randomly spread locations a soil sample was also taken from the upper 10cm of the mineral layer (if possible; namely, very rocky soil and often very thick layer of accumulated organic material that could not be removed so that mineral soil layer could not be reached ; soil sampler could only sample to a depth of 10cm). These 6 samples per plot were thoroughly mixed and dried at 40°C for about a week (very wet!). Then they were analyzed for pH, CEC, C, N, Na, K, Ca, Mg, Al, P ****(fractie?)****. Preparation of soil samples: soil samples are dried at 40°C and sieved (2mm sieve). Analysis for content of exchangeable cations (Ca, K, Mg): the soil sample is saturated and three times extracted wih 0.1 mol/l BaCl2. On this extract concentrations of exchangeable cations are determined by means of AAS. Analysis for total P content: 0.2g of soil is added to a solution of HNO3, HClO4 and H2SO4 in a teflon pot. The pots are heated to 150°C for 4 hours. Afterwards 50ml of the solution is poured into a volumetric flask. The total P content is then determined colometrically with malachite green. Analysis for Olsen P content: a 1/20 extract is made: one unit soil and 20 units NaHCO3 (0.5M, brought to pH 8.5 with NaOH); this extract is then stirred for 30 minutes and afterwards filtered. Then the Olsen P content is determined colometrically with malachite green. Analysis for pH: a 1/5 extract is made: one unit soil and 5 units KCl (1M); this extract is then stirred for 5 minutes and then the solution rests for 2 hours. Afterwards, pH is measured with a pH elektrode. Analyses for C,N,S: analysis is done using an Elementar analyzer, type Vario Macro Cube in configuration CNS, with Argon as carrier gas. Catalytic combustion of the sample (1.5g) is carried out at a permanent temperature of up to 1200°C. This is followed by reduction of the combustion gasses on hot copper in the refuction tube. The formed gasses N2, CO2, H2O, SO2 are separated via purge and trep chromatography and afterwards detected on a thermal conductivity detector (TCD). A connected PC computes the element concentration from the detector signal, and the sample weight on the basis of stored calibration curves.

Satakunta,Finland: 3 sites: areas 1 and 2 near Pomarkku, area 3 near Lankoski (vegetation was only monitored at sites 1 and 3)

Summer 2011

understorey vegetation: woody and non-woody vascular species (herbs, seedlings) < 1.3m

Overall very warm, sunny weather. In 2011, no mowing activities took place. In 2010, mowing of non-sown tree species took place