Widespread changes in arctic and boreal Normalized Difference Vegetation Index (NDVI) values captured by satellite platforms indicate that northern ecosystems are experiencing rapid ecological change in response to climate warming. Increasing temperatures and altered hydrology are driving shifts in ecosystem biophysical properties that, observed by satellites, manifest as long-term changes in regional NDVI. In an effort to examine the underlying ecological drivers of these changes, we used field-scale remote sensing of NDVI to track peatland vegetation in experiments that manipulated hydrology, temperature, and carbon dioxide (CO 2 ) levels. In addition to NDVI, we measured percent cover by species and leaf area index (LAI). We monitored two peatland types broadly representative of the boreal region. One site was a rich fen located near Fairbanks, Alaska, at the Alaska Peatland Experiment (APEX), and the second site was a nutrient-poor bog located in Northern Minnesota within the Spruce and Peatland Responses Under Changing Environments (SPRUCE) experiment. We found that NDVI decreased with long-term reductions in soil moisture at the APEX site, coincident with a decrease in photosynthetic leaf area and the relative abundance of sedges. We observed increasing NDVI with elevated temperature at the SPRUCE site, associated with an increase in the relative abundance of shrubs and a decrease in forb cover. Warming treatments at the SPRUCE site also led to increases in the LAI of the shrub layer. We found no strong effects of elevated CO 2 on community composition. Our findings support recent studies suggesting that changes in NDVI observed from satellite platforms may be the result of changes in community composition and ecosystem structure in response to climate warming.
Bibliographical noteFunding Information:
This research was supported by the National Science Foundation grant #DEB LTREB 1354370 (to ESK and MRT) and NASA grant #NNX14AF96G to (MJF and ESK), as well as cooperative agreements between the USDA Forest Service Northern Research Station and the University of Minnesota and Michigan Tech University. RAM and MM were supported by Minnesota Agricultural Experiment Station project MIN‐42‐060. APEX is supported by funding for the Bonanza Creek LTER (funded jointly by NSF grant DEB‐0423442 and USDA Forest Service, Pacific Northwest Research grant PNW01‐JV11261952‐231). SPRUCE is sponsored by the U.S. Department of Energy Office of Science, by Office of Biological and Environmental Research, and by the Oak Ridge National Laboratory. Generous funding for M. McPartland was made possible by the University of Minnesota Department of Forest Resources. We acknowledge the research groups at both APEX and SPRUCE sites, as well as numerous contributors at each site, including Robert Nettles, Doug Kastendick, Deacon Kyllander, Danielle Rupp, Lucas Albano, Natalie Zwanenburg, Jamie Hollings-worth, Lynette Potvin, Joseph Kendrick, Samantha Radermacher, Brian Benscoter, and Steven Filippelli. Thank you to Tim Duval and two other anonymous reviewers who helped to improve this manuscript prior to publication.
U.S. Forest Service, Grant/Award Number: PNW01‐JV11261952‐231; Oak Ridge National Laboratory; National Aeronautics and Space Administration, Grant/Award Number: NNX14AF96G; Minnesota Agricultural Experiment Station, Grant/ Award Number: MIN‐42‐060; University of Minnesota Department of Forest Resources; National Science Foundation, Grant/Award Number: DEB LTREB 1354370, DEB‐ 0423442
© 2018 John Wiley & Sons Ltd
- boreal peatlands
- carbon dioxide
- climate change
- community composition
- remote sensing
- soil moisture