ALBERT

Description: We measured the following vascular plant functional traits: plant height (cm), leaf size (LS, cm2), specific leaf area (SLA, cm2 g-1), leaf dry matter content (LDMC, mg g-1) and leaf moisture content (g g-1) from the most common species in each research unit. We measured the following Sphagnum traits: capitulum density (number of shoots cm-2), fascicle density (number cm-1), surface density (mg cm-3), capitulum dry mass (mg) and capitulum moisture content (cap_wc, g g-1). In addition, rate of net photosynthesis was measured at four light levels. The data was collected from Lakkasuo mire complex located in Southern Finland (61° 47' N; 24° 18' E). The study includes three sites called rich fen, poor fen, and bog. At each site two experimental units were established in 2000/2001: an undrained control unit and a Water level drawdown (WLD) unit that was surrounded by a 30 cm-deep ditches after a control year. Photosynthesis measurements were carried out during summer 2016, while other traits were sampled during August 2016. We measured vascular plant vegetative height (cm), leaf area (LA, cm2 leaf-1) with a leaf area scanner (LI-3000, LI-COR Inc.), leaf fresh mass and leaf dry mass after the sample was dried at 40 °C for at least 48h (mg leaf-1). Leaf dry matter content (LDMC mg g-1) was calculated from fresh and dry mass, while specific leaf area (SLA, cm2 g-1) was calculated from LA and dry mass. Leaf traits were measured from five replicate plants as an average of a sample of ten fully grown healthy leaves from each plant. Sphagnum moss traits were measured from five replicates of single-species samples. Each sample consisted of two parts: a volume-specific sample collected with a core (diameter 7 cm, area 38.5 cm2, height 3 cm) to maintain the natural density of the stand and an additional sample of ca. 10 individuals, with stems more than 5 cm at length. Before collecting the core in the field, the number of shoots was counted from a 4 × 4 cm square for capitulum density (cap_dens, number of shoots cm-2). The volume-specific sample was cleaned of litter and unwanted species before drying at 40 °C for at least 48h to determine the surface density (surf_dens, mg cm-3). The additional sample of ten moss individuals was divided into capitula and stems (4 cm below capitula). We counted the number of fascicles on the 4 cm stem segments (fasc_dens, number cm-1). The capitula were thoroughly moistened and placed on top of tissue paper for 2 minutes to drain, before weighing them for water-filled fresh mass (cap_fw, mg). The samples were dried at 60 °C for at least 48h to measure the capitulum dry masses (cap_dw, mg). The moisture contents of capitula (cap_mc, g g-1) were then calculated as the ratio of water-filled to dry mass. Height growth (mm growing season-1) was measured in the field with the modified cranked wire method (Clymo 1970) as a difference in height between the beginning (mid-May) and end (mid-October) of the growing season 2017. For both vascular plants and mosses, we measured net photosynthesis rate, with a fully controlled, flow-through gas-exchange fluorescence measurement systems (GFS-3000, Walz, Germany; LI6400, LI-COR, USA). For mosses the living apical parts (~0.5 to 1 cm) were harvested right before the measurement and placed on a custom-made cuvette. For vascular plants, leaves, or in the case of shrubs, segments of branches were enclosed within the cuvette without disturbing the connection to the rooting system. Net photosynthesis rate (A, µmol m-2 g-1 s-1) was measured at 1500, 250, 35, and 0 µmol m-2 s-1 photosynthetic photon flux density (PPFD). The cuvette conditions were kept constant (temperature 20°C, CO2 concentration 400 ppm, flow rate 500, impeller in level 5). Relative humidity (Rh) of incoming air was set to 40% for vascular plants and 60% for mosses; for mosses this setting retained the cuvette Rh at around 80%. The setting enabled mosses to remain moist to ensure photosynthesis but protected the device from excess moisture. The data was collected to find out the impact of long-term WLD on functional traits of vascular plants and mosses, and how this impact is modulated by nutrient status (rich fen, poor fen, bog). We first assess (i) how peatland species differ in their traits and their intraspecific trait variability, to quantify (ii) how WLD impacts community level traits at different peatland sites.

Description: The presented dataset contains chamber measurements of methane transport (mg CH₄ g dry plant mass-1 day-1) through individual aerenchymous peatland plants and the ancillary data for these measurements. Chamber measurements were performed for 7 plant species at two peatland sites, an oligotrophic fen and an ombrotrophic bog part of Siikaneva peatland complex in Southern Finland (61.8249° N, 24.1390° E, altitude 170 m a.s.l.) , during growing seasons 2013 and 2014 (between 1st of May and 28th of October). The ancillary data contains measurements of water table depth from the moss surface, air and peat temperature during the measurement as well as leaf area, dry mass of plant material, specific leaf area, number of leaves and the proportion of brown leaves in each sample that was measured. The dataset was collected to quantify the impact of plant species, plant properties and environmental factors on methane transport through aerenchymous plants. Plant CH₄ transport rate was measured using custom-made cylinder-shaped chambers that varied in volume between 0.7 and 5.0 liters. A plant sample of 2–104 leaves (depending on the growth form of the measured plant) belonging to the same species was separated from the peat and moss underneath by two plexiglass plates that were attached together with a hinge and had a smooth rubber seal between them to avoid compression of the plant. The proportion of green leaves in the sample varied from 0 to 100 % depending on the phase of the growing season. The sample was then covered with an opaque plastic chamber that was sealed with the plate by a smooth rubber seal attached to the bottom of the chamber. Airtightness of the system was ensured by tightening a belt that extended from one plate to the other over the chamber. Finally, a rubber stopper was used to seal a vent hole in the top of the chamber. Each plant sample was measured for 35 minutes, during which four 20 ml air samples were drawn from the chamber with a syringe through the rubber stopper in the top of the chamber at 5, 15, 25 and 35 minutes after chamber closure. The air samples were then injected into evacuated 12 ml glass vials (Labco Limited, UK). Simultaneous to the flux measurements, temperatures in the chamber (air) and peat at 5, 15 and 30 cm depth were recorded. WT was measured from a perforated plastic tube installed into the peat next to the sample after the WT level in the tube had stabilized for at least 30 minutes. After the flux measurement, the plant sample was cut with scissors and transported to the laboratory in a plastic bag. In each plant sample, the number of leaves was counted, the leaf area of brown and green leaf parts was measured with a scanner, and the dry weight was obtained for brown and green leaf parts separately after oven drying the sample at 60 °C for 24 hours. Using these data, specific leaf area (SLA, m²/g) was calculated for each sample. CH₄ concentration in the glass vials was analyzed with an Agilent Technologies 7890A gas chromatograph and Gilson GX-271 liquid handler. The CH₄ flux was calculated as the linear change in CH~4~ concentration in relation to time, chamber volume and temperature. Nonlinear changes in CH₄ concentration that were visually detected, were surmised to have resulted from a leak in the chamber or in the vial and were excluded from the analysis. In total 6 % of the measurements were excluded from the final dataset due to such nonlinearities.

Description: This study aimed at investigating the role of vegetation components, sedges, dwarf shrubs, and Sphagnum mosses, in methane fluxes of a boreal fen under natural and experimental water level drawdown conditions. We measured the fluxes during growing seasons 2001-2004 using the static chamber technique in a field experiment where the role of the ecosystem components was assessed via plant removal treatments. The first year was a calibration year after which the water level drawdown and vegetation removal treatments were applied. Under natural water level conditions, plant-mediated fluxes comprised 68 %-78% of the mean growing season flux (1.73 +/- 0.17 g CH4 m-2 month-1 from June to September), of which Sphagnum mosses and sedges accounted for one-fourth and three-fourths, respectively. The presence of dwarf shrubs, on the other hand, had a slightly attenuating effect on the fluxes. In water level drawdown conditions, the mean flux was close to zero (0.03 +/- 0:03 g CH4 m-2 month-1) and the presence and absence of the plant groups had a negligible effect.

Description: This study aimed at investigating the role of vegetation components, sedges, dwarf shrubs, and Sphagnum mosses, in methane fluxes of a boreal fen under natural and experimental water level drawdown conditions. We measured the fluxes during growing seasons 2001-2004 using the static chamber technique in a field experiment where the role of the ecosystem components was assessed via plant removal treatments. The first year was a calibration year after which the water level drawdown and vegetation removal treatments were applied. Under natural water level conditions, plant-mediated fluxes comprised 68 %-78% of the mean growing season flux (1.73 +/- 0.17 g CH4 m-2 month-1 from June to September), of which Sphagnum mosses and sedges accounted for one-fourth and three-fourths, respectively. The presence of dwarf shrubs, on the other hand, had a slightly attenuating effect on the fluxes. In water level drawdown conditions, the mean flux was close to zero (0.03 +/- 0:03 g CH4 m-2 month-1) and the presence and absence of the plant groups had a negligible effect.