Arctic Biosphere-Atmosphere Coupling across multiple Scales (ABACUS).

Lead Research Organisation: University of Stirling
Department Name: Biological and Environmental Sciences


Climate warming is resulting from disruption of the global carbon cycle. The Arctic is already warming significantly, and warming is expected to be fastest and greatest at high latitudes, 4-7 degrees C over the next century. However, there are complex links among climate, the carbon cycle and the global energy balance which mean that the details of such global changes remain poorly understood. We propose 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. Our overall aim is to determine what controls the temporal and spatial variability of carbon, water and energy exchange between arctic ecosystems and the atmosphere. Our field sites are based at Abisko, Sweden (with one focus area in dry tundra, the other in birch forest), and Kevo, Finland (with one focus on wet tundra, the other on dry tundra). At Kevo and Abisko both satellite imagery and aircraft flights will encompass an area of 10 km x 10 km, including both focus areas. The project has eight work-packages: WP1 Studies on plant allocation and phenology, and respiration-production ratios for major community types (via harvests, root measurement and isotope tracer experiments). WP2 Turnover of litter, soil organic matter (SOM), landscape distribution of soils (via soil surveys, isotope labelled litter, bomb C dating to determine SOM age), CH4 emissions. WP3 Chamber measurements of C and water exchanges from soils and vegetation at fine scales (a resolution of ~1m). WP4 Continuous tower measurements of CO2 and water exchange between the soils/vegetation and the atmosphere at scales of ~100 m, and records of snow depth, soil moisture and climate. WP5 Aircraft measurements over the two study regions, recording CO2 and water exchanges and images of the land surface and profiles of CH4. These measurements will extend over areas of many km squared. WP6 Earth Observation via satellites. We will link observations from several satellite instruments to measurements of plant cover recorded in field campaigns. WP7 We use models to connect the information connected at different time and space scales. The models represent our best understanding of the system, and we check and improve our understanding against independent observations, whether from chambers, towers, aircraft or satellites. We test whether we can understand the data from satellites and aircraft in terms of the detail recorded at the chambers and towers and with the WP1 and WP2 experiments. WP8 We will run an international workshop to share our ideas with colleagues from around the world. We will train post-graduates with a summer-school based around field measurement, and provide undergraduates with summer field experience.
Description Objective: To quantify the turnover of soil organic matter (SOM), particularly of contrasting age, and generate improved estimates of the total C stocks of arctic soils.
We sampled soil organic matter stocks over altitudinal transects, across hydrological gradients, and using cyclic sampling approaches to determine natural scales of variation. These studies allowed us to partition variability in soil C stocks according to variation in depth versus variation in soil carbon density. Soil depth and SOM content were highly variable on a range of scales, but there was a clear pattern of greater total organic matter in tundra (~6.5 kg C m 2) compared to birch woodlands (~3.5 kg C m 2). This difference is unexpected because birch woodlands are ca. twice as productive as tundra . We found that increased C cycling in woodlands is associated with reduced C storage. Plants can increase rates of decomposition by supplying labile organic compounds below ground. This process is called priming. Using 14CO2 measurements we demonstrated that the decomposition of older SOM was stimulated by plant activity during mid summer in a subarctic birch forest. If global warming results in the treeline moving north, then priming may result in a loss of C from tundra soils.
Outcome: evidence of plant-soil interactions affecting soil C storage counter intuitively.
Exploitation Route Supporting the development of improved soil C models.
Sectors Environment

Description To support public outreach activities detailing the climate change impacts at high latitudes
Sector Education
Impact Types Societal