DOI: 10.5061/dryad.bnzs7h4fn
title: Landcover map for the central region of the Yukon-Kuskokwim Delta, Alaska

description: Climate change is causing an intensification in tundra fires across the
 Arctic, including the unprecedented 2015 fires in the Yukon-Kuskokwim (YK)
 Delta. The YK Delta contains extensive surface waters (∼33% cover) and
 significant quantities of organic carbon, much of which is stored in
 vulnerable permafrost. Inland aquatic ecosystems act as hot-spots for
 landscape CO2 and CH4 emissions and likely represent a
 significant component of the Arctic carbon balance, yet aquatic fluxes of
 CO2 and CH4 are also some of the most uncertain. We
 measured dissolved CH4 and CO2 concentrations
 (n = 364), in surface waters from different types of
 waterbodies during summers from 2016 to 2019. We used Sentinel-2
 multispectral imagery to classify landcover types and area burned in
 contributing watersheds. We develop a model using machine learning to
 assess how waterbody properties (size, shape, and landscape properties),
 environmental conditions (O2, temperature), and surface water chemistry
 (dissolved organic carbon composition, nutrient concentrations) help
 predict in situ observations of CH4 and
 CO2 concentrations across deltaic waterbodies.
 CO2 concentrations were negatively related to waterbody size and
 positively related to waterbody edge effects. CH4 concentrations
 were primarily related to organic matter quantity and composition.
 Waterbodies in burned watersheds appeared to be less carbon limited and
 had longer soil water residence times than in unburned watersheds. Our
 results illustrate the importance of small lakes for regional carbon
 emissions and demonstrate the need for a mechanistic understanding of the
 drivers of greenhouse gasses in small waterbodies.
description: This landcover classification was created for the purposes of
 determining watershed landcover as potential drivers of downstream
 waterbody CH<sub>4</sub> and
 CO<sub>2</sub> concentrations. The region of interest is a
 watershed in the central portion of the Yukon-Kuskokwim Delta, Alaska,
 where field observations were based. The landcover map has been clipped to
 the watershed extent, and included as a shapefile. We
 created a 10-m resolution landcover map for the region of interest to
 determine the presence and abundance of various terrestrial, wetland,
 surface waterbodies, and disturbed areas in sample watersheds. We used an
 unsupervised k-means algorithm (Google Earth Engine, “wekaKMeans”) with
 the surface reflectance raw bands, derived bands (NDWI, NDVI), slope, and
 elevation as inputs for the classification. The Alaska Interagency
 Coordination Center historical wildfire database was used for wildfire
 delineations. Wildfires in the region of interest included fire scars from
 the 1970s, 1990s, and early 2000s, collectively designated as “old fires,”
 and fire scars from the large area burned in 2015. First, the region of
 interest was divided into unburned, old fire scars, and 2015 fire scars,
 and the classification algorithm was run separately for each. We used an
 initial number of classes “k” higher than the number of known landcover
 types in order to capture the variability in the driving layers, then
 later grouped similar classes produced by the k-means algorithm.
 Landcover accuracy was assessed using 350 randomly stratified
 points from the region of interest. The classifications at these points
 were compared to higher resolution (Worldview-2) imagery using Google
 Earth Engine and reclassified using expert assessment. We used a confusion
 matrix to assess the balanced accuracy of each classification, which
 ranged from 0.75 to 0.99 (Figure S2 in Supporting Information S1 from
 Ludwig et al. 2022 (the article associated with this dataset)).
description: The data type for the landcover map is integer, with 0 = no data
 (includes areas outside the research watershed and a small area where and
 old fire scar reburned in 2015 that could not be mapped),
 1= lichen dominant tundra on peat plateaus, some graminoids and
 prostrate dwarf shrubs 2= degrading permafrost on peat
 plateaus (either sparse but productive wetland graminoid, exposed mud, or
 shallow water, depending on antecedent rainfall) 3=
 vegetated wetland (peat fens, often with small channels and adjacent
 sphagnum bog or mosses underlying graminoids), lower in elevation relative
 to peat plateaus 4= shrub tundra, often the
 'banks' or edges of peat plateaus 5= tundra
 at the edges of degrading permafrost on peat plateaus, often wetter and
 more liekly to be dominated by sphagnum species and sphagnum
 fuscum 6= vegetated wetland (fens, but darker green,
 possibly tall shrubs. This was lumped with category 3 for most analyses),
 lower in elevation relative to peat plateaus. 7=
 waterbody edges; including unvegetated shoreline and areas with emergent
 vegetation and surface water 8= sedge tundra on peat
 plateaus (often the near the edges of plateaus or more sloped areas of
 plateaus) 9= low severity 2015 fire scar (peat
 plateaus). Includes small pockets of unburned within the fire
 scar. 10= 2015 fire scar tundra at plateau edges
 (similar to category 8 in unburned) 11= 2015 fire scar
 peat plateau 12= 2015 fire scar vegetated wetland (peat
 fens) 13= 2015 fire scar degrading permafrost (similar
 to category 2 unburned) 14= Old fire scar peat plateau
 edges (similar to category 8 unburned) 15= Old fire
 scar vegetated wetland (peat fens) 16= Old fire scar
 water edge (similar to category 7 unburned) 17= Old
 fire scar degrading permafrost (similar to category 2 unburned)
 18= Old fire scar tundra peat plateau 19= Old
 fire scar tundra peat plateau, but more abundance of shrubs and
 graminoids 20= Waterbodies (includes those in unburned
 and all fire scars)