As we know, Alberta is experiencing a long-term change in climate. The last 100 years has already seen an increase of about 1.4oC in average annual temperature, and it’s predicted that, over the next 40 years, the average temperature will increase at an even faster rate.[1] The ABMI has been working to understand climate change impacts on Alberta’s species and ecosystems and identify potential responses.
But the impacts of climate change can be difficult to define. In the north, a warming climate has already led to earlier snowmelt and longer growing seasons in arctic and boreal ecosystems. However, it’s not clear what longer growing seasons will mean for ecosystem function and productivity in the north: there is evidence for both increased[2] and decreased[3] productivity with an earlier snowmelt. Scientists have also observed both “greening” and “browning” of boreal and arctic areas in recent years when they look at satellite images of the north.[4]
To explore these changes and their implications, NASA has announced a long-term field campaign, the Arctic Boreal Vulnerability Experiment (ABoVE). Climate change is happening in the arctic and boreal region faster than anywhere else on the planet. Impacts of climate change – like reduced sea ice in the Arctic Ocean, warming and thawing of permafrost, and increases in climate-driven disturbances – affect local residents of the Arctic and boreal region, and may also further accelerate global climate change by releasing currently sequestered carbon. As part of the ABoVE project, Dr. John Gamon, Professor in the Departments of Earth & Atmospheric Sciences and Biological Sciences at the University of Alberta, is leading a 20-person multidisciplinary team of collaborators, including the ABMI’s own Dr. Jahan Kariyeva, to study ecosystem changes in the arctic and boreal regions of Alaska and western Canada.
Gamon and his team are employing a variety of remote sensing technologies, including satellite imagery and automated field methods, to evaluate the relationship between growing season length and productivity. A commonly used metric is the satellite-derived Normalized Difference Vegetation Index (NDVI), a vegetation greenness index that is a measure of photosynthetic capacity of the land surface cover. NDVI allows the team to measure and assess land surface productivity and phenology (timing of plant growth). But, NDVI is best at detecting growth in annuals and deciduous vegetation, not the evergreens that live in the pine and spruce forests of the boreal region. NDVI patterns alone aren’t sufficient to understand the cause and ecosystem implications of trends in the satellite record for northern regions.
View trends in vegetation greening and browning across the ABoVE Study Domain here.
So, the team is using a newer version of satellite imagery: MODIS Collection 6, with new and improved science algorithms and bands of spectral reflectance that are capable of measuring chlorophyll – carotenoid values that can help capture the “invisible” photosynthetic and phenological signals of evergreens. Using combinations of new MODIS and carbon flux data, the team will develop a new model and compare it with existing models to evaluate the dynamics of growing season length and productivity in arctic and boreal ecosystems. This will allow the team to investigate reported “browning and greening,” their causes, and their implications for different ecosystems.
The team’s hypothesis is that hydrology, or the presence and movement of water, influences ecosystem function and productivity across the arctic and boreal regions of the ABoVE study and that the relationship between season length and productivity can largely be explained by looking at hydrology. This is based on an emerging body of evidence suggesting strong hydrological controls on northern ecosystem productivity.[5] In recent years, disturbance due to drought, fire, and human activity is increasing, and likely will be an additional influence on productivity patterns, especially in the boreal. As a result, these factors will be considered when evaluating model results, partly by working with collaborators studying disturbance.
That’s where the ABMI comes in! Already hard at work assessing human disturbance in Alberta through our human footprint monitoring program, ABMI will provide the ABoVE team with our data about how various human activities are affecting vegetation cover and productivity. Dr. Jahan Kariyeva, manager of ABMI’s Geospatial Centre, will also be involved in model development and validation for the boreal region of Alberta. ABMI’s work on analyzing ecosystem impact due to human disturbance will help the team to isolate direct human influences from natural disturbance, like fire and the long-term effects of climate change.
ABMI monitoring objectives are synergetic with the ABoVE research objectives to understand cumulative impacts of global change in northern ecosystems. Linking Canadian and U.S. efforts to study how these impacts will affect often coupled ecological and socio-economic systems represents timely and needed collaboration opportunities. I am excited for the new research and technology capacities that this project will contribute to support more effective environmental monitoring in northern ecosystems. I am also looking forward to working with Dr. Gamon on the development and application of these emerging capacities specifically for the boreal regions of Alberta to support ABMI’s biodiversity and human footprint monitoring efforts. – Dr. Jahan Kariyeva, Geospatial Centre Manager
Providing an improved assessment of both growing season and productivity trajectories allows the team to examine the relationships between ecosystem responses to dynamics in hydrology and carbon balance. An improved understanding of how these are affected by climate and anthropogenic pressure will enable new insights into ecological functioning of arctic and boreal biomes.
References:
[1] Schneider, R. R. 2013. Alberta’s natural subregions under a changing climate: past, present, and future. Alberta Biodiversity Monitoring Institute, Alberta, Canada.
[2] Sweet, S.K. et al. 2014. Tall decidulous shrubs offset delayed start of growing season through rapid leaf development in Alaskan arctic tundra. Arctic, Antarctic, and Alpine Research 46.3: 682-697.
[3] Humphreys, E.R., Lafleur, P.M. 2011. Does earlier snowmelt lead to greater CO2 sequestration in two low Arctic tundra ecosystems? Geophysical Research Letters 38. doi: L0970310.1029/2011gl047339
[4] Goetz, S.J., et al. 2005. Satellite-observed photosynthetic trends across boreal North America associated with climate and fire disturbance. Proceedings of the National Academy of Sciences of the United States of America 102.38 : 13521-13525.
[5] Dagg, J., Lafleur, P. 2011. Vegetation Community, Foliar Nitrogen, and Temperature Effects on Tundra CO2 Exchange across a Soil Moisture Gradient. Arctic Antarctic and Alpine Research 43:189-197. doi: 10.1657/1938-4246-43.2.189
Huemmrich, K.F. et al. 2010. Remote sensing of tundra gross ecosystem productivity and light use efficiency under varying temperature and moisture conditions. Remote Sensing of Environment 114:481-489. doi: 10.1016/j.rse.2009.10.003
Huemmrich, K.F. 2010. Tundra carbon balance under varying temperature and moisture regimes. Journal of Geophysical Research-Biogeosciences 115. doi: G00i02 10.1029/2009jg001237
Ma, Z. et al. 2012. Regional drought-induced reduction in the biomass carbon sink of Canada’sboreal forests. Proceedings of the National Academy of Sciences of the United States of America 109:2423-2427. doi: 10.1073/pnas.1111576109
Yi, Y., Kimball, J.S., Reichle, R.H. 2014. Spring hydrology determines summer net carbon uptake in northern ecosystems. Environmental Research Letters 9. doi: 10.1088/1748-9326/9/6/064003