Biomass and Nitrogen Retention in Pure and Mixed Beech-Conifer Tree Stands (Meshbag Experiment 2019)

The study was conducted in four sites (Winnefeld, Nienburg , Unterluess and Goehrde). Each site is composed of five types of forests: beech (B), douglas-fir (D), spruce (S), beech-douglas-fir (BD) and beech-spruce(BS). Hypahe ingrowth mesh bags (2.1 cm diameter x 10 cm length) with 40 g quartz sand and 2 g of ion exchange beads were installed. The ion exchange beads are composed of hydrogen and hydroxide that enable exchnage of cations and anions respectively. Two days before harvest, the mesh bags were watered (15 ml distilled water) 2 hrs before injecting 0.18 mg of 15N in form of 15-N labelled solution (2 mM) as either ammonium chloride or potassium nitrate. The control mesh bags were either injected with NH4Cl, KNO3 (2 mM) or not injected with any solution. Soil cores (5.5 cm diameter x 10 cm depth) were taken around the mesh bags. After harvest, samples were sorted into components (fine roots, soil, beads, sand) which were washed (fine roots), freeze - dried, milled and weighed in tin capsules for 15N analysis. Sand aliquotes for Lipid and fungal community analysis were kept frozen (-20C).