University of Oulu

May JL, Hollister RD, Betway KR, Harris JA, Tweedie CE, Welker JM, Gould WA and Oberbauer SF (2020) NDVI Changes Show Warming Increases the Length of the Green Season at Tundra Communities in Northern Alaska: A Fine-Scale Analysis. Front. Plant Sci. 11:1174. doi: 10.3389/fpls.2020.01174

NDVI changes show warming increases the length of the green season at tundra communities in Northern Alaska : a fine-scale analysis

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Author: May, Jeremy L.1; Hollister, Robert D.2; Betway, Katlyn R.2;
Organizations: 1Department of Biological Sciences, Florida International University, Miami, FL, United States
2Department of Biological Sciences, Grand Valley State University, Allendale, MI, United States
3Department of Biological Sciences, University of Texas at El Paso, El Paso, TX, United States
4Ecology and Genetics Research Unit, University of Oulu, Finland & UArctic, Oulu, Finland
5Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK, United States
6USDA Forest Service International Institute of Tropical Forestry, Rio Piedras, Puerto Rico
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 1.2 MB)
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Language: English
Published: Frontiers Media, 2020
Publish Date: 2020-09-08


A warming Arctic has been associated with increases in aboveground plant biomass, specifically shrubs, and changes in vegetation cover. However, the magnitude and direction of changes in NDVI have not been consistent across different tundra types. Here we examine the responsiveness of fine-scale NDVI values to experimental warming at eight sites in northern Alaska, United States. Warming in our eight sites ranged in duration from 2‑23 seasons. Dry, wet and moist tundra communities were monitored for canopy surface temperatures and NDVI in ambient and experimentally-warmed plots at near-daily frequencies during the summer of 2017 to assess the impact of the warming treatment on the magnitude and timing of greening. Experimental warming increased canopy-level surface temperatures across all sites (+0.47 to +3.14˚C), with the strongest warming effect occurring during June and July and for the southernmost sites. Green-up was accelerated by warming at six sites, and autumn senescence was delayed at five sites. Warming increased the magnitude of peak NDVI values at five sites, decreased it at one site, and at two sites it did not change. Warming resulted in earlier peak NDVI at three sites and no significant change in the other sites. Shrub and graminoid cover was positively correlated with the magnitude of peak NDVI (r=0.37 to 0.60) while cryptogam influence was mixed. The magnitude and timing of peak NDVI showed considerable variability across sites. Warming extended the duration of the summer green season at most sites due to accelerated greening in the spring and delayed senescence in the autumn. We show that in a warmer Arctic (as simulated by our experiment) the timing and total period of carbon gain may change. Our results suggest these changes are dependent on community composition and abundance of specific growth forms and therefore will likely impact net primary productivity and trophic interactions.

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Series: Frontiers in plant science
ISSN: 1664-462X
ISSN-E: 1664-462X
ISSN-L: 1664-462X
Volume: 11
Article number: 1174
DOI: 10.3389/fpls.2020.01174
Type of Publication: A1 Journal article – refereed
Field of Science: 1181 Ecology, evolutionary biology
Funding: This study was conducted with support from National Science Foundation grants PLR-1504381 and PLR-1836898.
Copyright information: © 2020 May, Hollister, Betway, Harris, Tweedie, Welker, Gould and Oberbauer. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.