Abiotic and Biotic Factors Impacting Tundra Productivity in Alaska

Authors: ZHANG, QINGYUAN - University Of Maryland; Zhang, Xuesong; LARA, MARK - University Of Illinois; LI, ZHENGPENG - Collaborator; XIAO, JINGFENG - University Of New Hampshire

Submitted to: Environmental Research Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/8/2023
Publication Date: 9/18/2023
Citation: Zhang, Q., Zhang, X., Lara, M.J., Li, Z., Xiao, J. 2023. Abiotic and Biotic Factors Impacting Tundra Productivity in Alaska. Environmental Research Letters. 18. https://doi.org/10.1088/1748-9326/acf7d6.
DOI: https://doi.org/10.1088/1748-9326/acf7d6

Interpretive Summary: Satellite imagery can provide valuable information to document and elucidate changes in ecosystems. Here, we analyzed the MOoDerate resolution Imaging Spectrometer (MODIS) satellite data to derive multiple biotic and abiotic factors [(e.g., fractional covers by vegetation, snow, water, and soil, normalized difference vegetation index (NDVI), and fraction of absorbed photosynthetically active solar radiation by canopy chlorophyll (fAPARchl)]) indicating changes in the tundra ecosystems near the town of Utqiagvik in northern Alaska from 2001-2014. We found that warmer temperatures and earlier snowmelt, along with rodents’ boom-bust cycles, were the major drivers of the changes in the tundra ecosystem productivity. In addition, the use of fAPARchl can better reflect changes in ecosystem productivity than the widely used NDVI. The methods demonstrated here provide a novel means to analyze and understand changes in the global ecosystems (e.g., forests, agricultural, and grassland)

Technical Abstract: High-latitude tundra productivity is influenced by a range of abiotic and biotic factors, including earlier snowmelt, warmer temperatures and rodent population booms as observed near the town of Utqiagvik in northern Alaska during the summer of 2008. We used satellite observations from the Moderate Resolution Imaging Spectrometer (MODIS) to determine cover fractions of vegetation (VGCF), snow (SNOWCF), standing water (WaterBodyCF), and soil (SOILCF), and the fractional absorption of photosynthetically active solar radiation (PAR) by canopy chlorophyll (fAPARchl), the absorbed PAR by vegetation chlorophyll (APARchl), and the normalized difference vegetation index (NDVI). This region experienced large interannual variability in all productivity metrics, which were explainable by abiotic and biotic factors. We found that earlier snowmelt was associated with higher SOILCF, higher VGCF, higher fAPARchl, higher NDVI and higher APARchl in June. We observed that monthly temperature had a significant impact on monthly fAPARchl, APARchl, and NDVI. The severe lemming outbreak in 2008 was noticeable in the MODIS records. Relative to 2007, we found a reduction in live vegetation and increase in bare ground during August of 2008. However, two years after the lemming population outbreak, the tundra ecosystem completely recovered to attain a “greener” landscape (higher fAPARchl in 2010 and 2011 than in 2007)