MODIS-informed greenness responses to daytime land surface temperature fluctuations and wildfire disturbances in the Alaskan Yukon River Basin

Abstract

Pronounced climate warming and increased wildfire disturbances are known to modify forest composition and control the evolution of the boreal ecosystem over the Yukon River Basin (YRB) in interior Alaska. In this study, we evaluate the post-fire green-up rate using the normalized difference vegetation index (NDVI) derived from 250 m 7 day eMODIS (an alternative and application-ready type of Moderate Resolution Imaging Spectroradiometer (MODIS) data) acquired between 2000 and 2009. Our analyses indicate measureable effects on NDVI values from vegetation type, burn severity, post-fire time, and climatic variables. The NDVI observations from both fire scars and unburned areas across the Alaskan YRB showed a tendency of an earlier start to the growing season (GS); the annual variations in NDVI were significantly correlated to daytime land surface temperature (LST) fluctuations; and the rate of post-fire green-up depended mainly on burn severity and the time of post-fire succession. The higher average NDVI values for the study period in the fire scars than in the unburned areas between 1950 and 2000 suggest that wildfires enhance post-fire greenness due to an increase in post-fire evergreen and deciduous species components.

Acknowledgements

This project was funded by the USGS Geographic Analysis and Monitoring Program in support of Climate Change Network. We thank Norman Bliss and Shengli Huang (ARTS) for internal technical review. The work of Zhengxi Tan (ARTS) was performed under USGS contract G08PC91508; the works of C. B. Jenkerson (ERT), C. J. Young (ERT), and J. Oeding (SGT) were performed under USGS contract G10PC00044. Mention of trade names or commercial products does not constitute endorsement or recommendation for use by the U.S. Geological Survey.