Browning of the landscape of interior Alaska based on 1986-2009 Landsat sensor NDVI
Abstract:We used a time series of 1986–2009 Landsat sensor data to compute the Normalized Difference Vegetation Index (NDVI) for 30 m pixels within the Bonanza Creek Experimental Forest of interior Alaska. Based on simple linear regression, we found significant (p < 0.05) declining trends in mean NDVI of three dominant landscape types of floodplains, lowlands, and uplands. At smaller patch sizes, similar declining trends occurred among topographic classes of north- and south-facing slopes and valley bottoms and among forest classes, including black spruce (Picea mariana (Mill.) B.S.P.). Significant positive trends in mean NDVI occurred only in areas that were recently burned, whereas wetlands had no significant trend. The greatest departure from the NDVI trend line occurred following the 2004 drought for all forest classes except black spruce, which dominates the coldest sites, and balsam poplar (Populus balsamifera L.), which occurs on low, moist terraces within the Tanana River floodplain. The consistent long-term declining trend at several spatial scales may be due to a regional climatic regime shift that occurred in the mid-1970s.
Document Type: Research Article
Affiliations: 1: Department of Forest Sciences, University of Alaska Fairbanks, Fairbanks, AK 99775, USA. 2: Boreal Ecology Cooperative Research Unit, USDA Forest Service Pacific Northwest Research Station, Fairbanks, AK 99775, USA.
Publication date: July 1, 2012
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