Vario el analyser

Representative soil samples for the bioassays were taken from each plot by pooling five soil sub-samples (depth 10 cm, diameter 8 cm) collected from the centre of each plot and four orthogonal points 5 m from the centre. Fresh soil was sieved to 4 mm and stored at 4°C prior to analyses. KCl extractable N concentration (NO 3 --N and NH 4 + -N) was determined colorimetrically in a segmented flow stream using an AutoAnalyser (Seal-Analytical). Net N-mineralisation rate was measured as the release of mineral N after incubation of soil samples (5 g) for 14 days at 25°C (Ross 1992 ). Soil moisture content, water-holding capacity (WHC) and pH (1:2.5, soil/water) were also determined for each soil sample. Litter of each of the four grass species (A. capillaris, A. odoratum, C. flavescens subsp. Brevis and P. colensoi) was collected from each plot. For each species, at least 10 g of senesced leaves was collected from at least five individual plants. Due to the timing of collection, the majority of senescent material available from A. odoratum was stem litter and not leaf litter, so stem litter was used for all analyses of this species. All litter was processed in the same way as the standardised litter described above (that is air-dried and homogenised). Litter C and N concentrations were measured on ground samples using an automated Dumas procedure on a Vario EL analyser (Elementar).

New cores were collected from five upland ombrotrophic blanket bogs selected to represent a latitudinal gradients through Britain (Fig. 1). Triplicate adjacent cores were extracted in 2014 using both a box corer (to recover the surface vegetation and uppermost 1 m of peat) and a Russian-type corer (for peat deeper than 1 m). The sites were: Great Gnat's Head on Dartmoor (DM), Migneint (Mg) in northwest Wales, Moor House (MH) in northern England, Glensaugh (G) near the north eastern Scottish coast and Forsinard Flows (F) in the far north of mainland Scotland. Physiographical information for each site is summarised in Table 1. All cores extended down to the underlying mineral substrate, ranging in length from 95 cm (Glensaugh) to 417 cm (Forsinard).
The new cores were carefully extruded, sliced at 10 cm intervals, airdried for one week, manually sieved to 2 mm to remove large particles and roots, oven-dried at 60 °C to remove residual moisture and ball-milled to a fine, homogenous powder. Bulk densities of all samples were calculated prior to milling by dividing the dry matter mass by the original volume of wet material. Phosphorus content was measured colorimetrically using a Seal Analytical AQ2 discrete analyser after digestion in H 2 SO 4 /H 2 O 2 . After drying at 105 °C, carbon and nitrogen were determined on an Elementar Vario-EL analyser using an ISO17025 accredited method.