The ABACUS (Arctic Biosphere-Atmosphere Coupling at multiple Scales) research project is a major, linked programme of plant and soil studies, atmospheric measurements, aircraft and satellite observations, and modelling, to improve our understanding of the response of the arctic terrestrial biosphere to climate change. The data collected as part of the ABACUS Work Package 1 (Studies on plant allocation and phenology, and respiration-production ratios for major community types (via harvests, root measurement and isotope tracer experiments) includes root measurements and isotope ratios of plants as follows: Plant data for WP1 harvest and ingrowth core plots, Abisko (Sweden), 15 Jul 2007 - 08 Aug 2007 - Fine Root Length, Abisko (Sweden), 15 Jul 2007 - 08 Aug 2007 - Leaf and stem C and N, Abisko (Sweden), 15 Jul 2007 - 08 Aug 2007 - Fine Root Length, Kevo (Finland), 01 Jun 2008 - 03 Sep 2008 - Leaf and stem C and N, Kevo (Finland), 01 Jun 2008 - 03 Sep 2008

The data are biomass measurements from an ozone exposure experiment, during which Trifolium repens and Lolium perenne were exposed as both monocultures and two-species mixtures to an episodic rural ozone regime in large, well-watered containers within solardomes for 12 weeks. Treatments were elevated ozone (AOT40 (Accumulated Ozone Threshold exposure of 40 parts per billion) of 12.86 ppm h) or control conditions (AOT40 of 0.02 ppm h). Measurements were dry weight, with a cutting height of 7cm above soil level. The distribution of plant material within the canopy was determined by separating material growing in the upper canopy (>14cm) from the canopy edge and the inner canopy for both species. The experiments were carried out in the CEH Bangor Air Pollution Facility. Work was funded by the Centre for Ecology & Hydrology Integrating Fund Initiative. The observed decreases in photosynthetic efficiency and capacity in elevated ozone indicate that the ability of such ubiquitous vegetation to act as a sink for atmospheric carbon may be reduced in future climates. Full details about this dataset can be found at https://doi.org/10.5285/5de90f7a-dec9-4bd5-af52-d0873a09d25d