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Layer: Yellow-Cedar Decline 1986 to 2024 - Annual (ID:0)

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Name: Yellow-Cedar Decline 1986 to 2024 - Annual

Display Field: Severity2

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Geometry Type: esriGeometryPolygon

Description: <div style="text-align:Left;"><div><div><p style="margin:0 0 11 0;"><span>This dataset represents yellow-cedar decline mapped across Southeast Alaska 1986-2024 by aerial detection surveys and three remote sensing efforts in 2004, 2006, and 2020. </span><span><span>The </span></span><span style="font-weight:bold;"><span>survey type </span></span><span><span>is identified as aerial survey, photo interpretation, or satellite imagery interpretation in the attribute table. </span></span></p><p style="margin:0 0 11 0;"><span>The cumulative dataset provides the most comprehensive spatial information about the total extent of yellow-cedar decline through 2024. Aerial surveys in Alaska typically cover 10-15% of the forested area of the state each year. Aerial s</span><span>urveyors from the Alaska Division of Forestry &amp; Fire Protection and USDA Forest Service - Forest Health Protection document insect, disease, and abiotic damage in the forest from about 1000 feet altitude using a digital mobile sketch-mapping tablet and software. </span><span><span>This forest health dataset includes both </span></span><span>polygon and point data. Points have a buffered area based on tree number. Initially, aerial surveys were conducted using paper 1:250,000 USGS quadrangle maps. In 1999, aerial surveys in Alaska began mapping using tablets and software. Digital mobile sketch-mapping displays the plane’s location via GPS, allows observers to zoom to various scales, and generally improves the accuracy and resolution of polygon placement compared to paper mapping. The specific </span><span style="font-weight:bold;"><span>method</span></span><span> of mapping is capture in the attribute table. During some survey years, the spatial distribution of decline added to the cumulative decline layer exceeded the acreage added during that year's annual aerial survey, originating from continued efforts to digitize decline mapped during prior survey efforts. Decline added through these digitization efforts is identified in the </span><span style="font-weight:bold;">method</span><span> field (DigitizedOutsideAerialDetectionSurvey).</span></p><p style="margin:0 0 11 0;"><span>Remote sensing efforts to map yellow-cedar decline include two mid-scale aerial photo interpretation efforts (25,388 acres along Peril Strait in 2004 and 9,057 acres on Mt. Edgecumbe on Kruzof Island in 2006). Details about the scale and methodology of photo interpretation mapping efforts are summarized in the report by P. Hennon and D. Wittwer: </span><a href="https://research.fs.usda.gov/treesearch/43982" style="text-decoration:underline;"><span>Evaluating key landscape features of a climate-induced forest decline</span></a><span> (Project WC-EM-07-01). </span><span style="font-style:italic;">In</span><span>: Potter, Kevin M.; Conkling, Barbara L., eds. 2013. Forest Health Monitoring: national status, trends, and analysis 2010. Gen. Tech. Rep. SRS-GTR-176. Asheville, NC: U.S. Department of Agriculture Forest Service, Southern Research Station. 117-122.. The finer-scale polygons identified through photo interpretation were buffered 50 m to complement the scale of aerial survey. In 2020, decline was mapped on parts of Prince of Wales and Annette Islands using high-resolution satellite imagery (‘scan and sketch surveys’) due to the global pandemic. These details are recorded (</span><span style="font-weight:bold;"><span>method</span></span><span><span>).</span></span></p><p style="margin:0 0 11 0;"><span><span>The specific </span></span><span style="font-weight:bold;"><span>survey year </span></span><span><span>of decline detection is also provided, apart from a period in the 1980s and from 1991 to1994 during which decline data was digitized from paper aerial survey maps. The 363,000 acres mapped during this period include both active and older decline. Aerial surveys typically focus on actively damaged and dying trees, but there was a need to understand the full spatial extent of the problem while the cause was investigated and compared to broader landscape patterns. The </span></span><span style="font-weight:bold;"><span>decline type </span></span><span><span>identifies whether active decline, old decline, or a combination of old and active decline were mapped or tracked separately during a particular survey effort. For most of the 2000s, decline mapping has been limited to actively dying trees only. </span></span></p><p style="margin:0 0 11 0;"><span style="font-weight:bold;"><span>Decline severity</span></span><span> was recorded with mapped decline starting in 2001, soon after the conversion from paper to digital mapping. Severity has been assigned in different ways over time, initially based upon the number of trees per acre affected (rated low, medium, high) and later based about the percentage of host trees affected (rated very low, low, moderate, severe, very severe). This dataset has merged these types of severity assessments into a simplified low, moderate, high system by lumping the very low and low ratings as low and the severe and very severe ratings as high. This is our first attempt to combine these systems, understanding that changes in methodology and variation in severity rankings among surveyors complicates interpretation. </span></p><p style="margin:0 0 11 0;"><span><span>Yellow-cedar decline root freezing injury can take 10-15 years to kill individual trees and is progressive within affected forests; therefore, there is overlap in the impacted areas mapped over time. About one-quarter of the decline mapped during the 1980s and from 1991 to 1994 was also captured through subsequent survey efforts. The lag between freezing injury and crown symptoms development, and the multi-year persistence of crown symptoms within affected trees and forests, makes it difficult to attribute mapped decline to specific weather events or years. It is important to note that this cumulative dataset has overlapping decline polygons that will be double-counted if the </span></span><span style="font-weight:bold;"><span>acres</span></span><span><span> column is summed, inflating the spatial extent of decline. Another dataset has been produced alongside this one that accounts for decline overlap across time, with a total extent of 728,000 acres.</span></span></p><p style="margin:0 0 11 0;"><span>This cumulative yellow-cedar decline layer was clipped/restricted to areas occurring within upland forest and forested wetland cover classes in the USGS National Land Cover Database-modified dataset (https://www.usgs.gov/node/279743, modified by Frances Biles, Geographer, PNW Research Station USDA Forest Service for the 2016 Climate Adaptation Strategy for Yellow-Cedar in Alaska). This refinement eliminates portions of mapped decline polygons that are unlikely to support yellow-cedar and reduces the total acreage of cumulative yellow-cedar by about 68,500 acres or 8.6%. This refinement has been applied to cumulative yellow-cedar decline estimates published by the USDA-FS and partners over the past decade. A significant refinement occurred in 1996 and was used to restrict mapping that occurred prior to that time such that the older errors were not reincorporated into the final dataset. </span></p><p style="margin:0 0 11 0;"><span style="font-weight:bold;"><span>SurveyType</span></span><span><span>: AerialSurvey, AerialPhotoInterpreation, SatelliteImageryInterpretation</span></span></p><p style="margin:0 0 11 0;"><span style="font-weight:bold;"><span>Method</span></span><span>: AerialSurveyMobleSketchMapping, AerialSurveyPaperMapping, DigitizedOutsideAerialDetectionSurvey, MidScaleAerialPhotoInterpretation, SatelliteImageryScanandSketch</span></p><p style="margin:0 0 11 0;"><span style="font-weight:bold;"><span>SurveyYear: </span></span><span><span>Year of detection. Assigned to a specific year except for the period spanning 1986-1987 and 1991-1994. </span></span></p><p style="margin:0 0 11 0;"><span style="font-weight:bold;"><span>DeclineType:</span></span><span><span> Active, Old, Old_and_Active</span></span></p><p style="margin:0 0 11 0;"><span style="font-weight:bold;"><span>DeclineSeverity:</span></span><span> Low, Moderate, High</span></p><p style="margin:0 0 11 0;"><span style="font-weight:bold;"><span>DeclineSeverity2:</span></span><span> Low, Moderate, High, Very Light, Light, Severe, Very Severe</span></p><p style="margin:0 0 11 0;"><span style="font-weight:bold;">Acres: </span><span>International Survey Acres, Alaska Albers Equal Area Conic, NAD83</span></p></div></div></div>

Copyright Text: USDA Forest Service Forest Health Protection and Alaska Division of Forestry and Fire Protection

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Last Edit Date: 6/4/2025 10:50:06 PM

Schema Last Edit Date: 6/4/2025 10:50:06 PM

Data Last Edit Date: 6/4/2025 10:46:03 PM

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