DOCSLIB.ORG

Downloaded 09/29/21 01:06 AM UTC Earth Interactions D Volume 23 (2019) D Paper No

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Downloaded 09/29/21 01:06 AM UTC Earth Interactions D Volume 23 (2019) D Paper No Earth Interactions d Volume 23 (2019) d Paper No. 4 d Page 1 Ó 2019 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses). Changes in Vegetation Cover of the Arctic National Wildlife Refuge Estimated from MODIS Greenness Trends, 2000–18 Christopher Pottera NASA Ames Research Center, Moffett Field, California Received 5 October 2018; in final form 18 December 2018 ABSTRACT: Trends and transitions in the growing-season normalized dif- ference vegetation index (NDVI) from the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite sensor at 250-m resolution were analyzed for the period from 2000 to 2018 to understand recent patterns of vegetation change in ecosystems of the Arctic National Wildlife Refuge (ANWR) in Alaska. Statistical analysis of changes in the NDVI time series was conducted using the breaks for additive seasonal and trend method (BFAST). This struc- tural change analysis indicated that NDVI breakpoints and negative 18-yr trends in vegetation greenness over the years since 2000 could be explained in large part by the impacts of severe wildfires. At least one NDVI breakpoint was detected in around 20% of the MODIS pixels within both the Porcupine River and Coleen River basins of the study area. The vast majority of vegetation cover in the ANWR Brooks Range and coastal plain ecoregions was detected with no (positive or negative) growing-season NDVI trends since the year 2000. Results suggested that most negative NDVI anomalies in the 18-yr MODIS record have a Corresponding author: Christopher Potter, [email protected] DOI: 10.1175/EI-D-18-0018.1 Unauthenticated | Downloaded 09/29/21 01:06 AM UTC Earth Interactions d Volume 23 (2019) d Paper No. 4 d Page 2 been associated with early spring thawing and elevated levels of surface moisture in low-elevation drainages of the northern ANWR ecoregions. KEYWORDS: Climate records; Remote sensing; Ecosystem effects; Forest fires; Regional effects 1. Introduction The Arctic National Wildlife Refuge (ANWR) was established by the Alaska National Interest Lands Conservation Act of 1980 and covers 19 million acres (77 000 km2) in northeast Alaska. Proponents of development in the ANWR view its 1.6 million acre (6475 km2) coastal plain as a promising onshore oil reserve (Comay et al. 2018). Nonetheless, wildlife habitats in the ANWR are vulnerable to long-lasting effects from any disturbance, in part because short growing seasons in the Arctic provide limited time for species to recover. Caribou (Rangifer tarandus) are the most numerous large animals in the ANWR. The Porcupine herd (named after the Porcupine River) numbers approximately 150 000 animals. The herd’s Arctic Village–South Brooks Range spring migration route within Alaska and the ANWR crosses the East Fork of the Chandalar River, the Sheenjek River, and upper Coleen River, and follows the Firth River into Canada where it joins the Old Crow migration route. Caribou herds will use areas in the northern foothills of the Brooks Range during summer at elevations of 300– 600 m, with vegetation communities consisting of graminoid meadows, dwarf shrub, and alpine tundra communities (Nicholson et al. 2016). Caribou consume a variety of vegetation including fungi, lichens, woody browse, graminoids, and forbs (Thompson et al. 2015; Denryter et al. 2017). Barboza et al. (2018) reported that female caribou and their calves in northern Alaska select a mixture of graminoids, browse, and forbs to achieve adequate dietary concentrations of digestible energy and nitrogen requirements. Graminoids were the most abundant forage, accounting for 77% of the digestible nitrogen and 74% of the digestible energy in forage biomass. Localized patterns of vegetation growth and decline in the ANWR may be affecting the survival and reproduction of the caribou herds, which are a crucial subsistence resource for Alaska native communities in the region. Because of changing growing-season lengths, caribou migration may be increasingly out of sync with the timing of key food resources and forage availability. Parturition (birthing of calves) precedes or coincides with the onset of the Arctic growing season and is timed to maximize the period of peak nutrient availability to mother– offspring pairs (Loe et al. 2005). The trophic mismatch hypothesis for large herbivores postulates that earlier green-up will shift peak nutrient availability away from peak nutritional demand leading to lower productivity. Recent work by Gustine et al. (2017) showed that climate-related effects on forage in the summer and autumn ANWR migration ranges corresponded more closely with the demands of female caribou and their offspring to gain mass for the next reproductive cycle. Therefore, these researchers implied that the window of time to examine the mismatch hypothesis in Arctic ungulates is not at parturition, but rather in late summer–autumn, at which time the effects of small changes in forage quality are amplified by forage abundance, peak forage intake, and resultant mass gains in mother–offspring pairs. Unauthenticated | Downloaded 09/29/21 01:06 AM UTC Earth Interactions d Volume 23 (2019) d Paper No. 4 d Page 3 In a study of land-cover change using high-resolution aerial imagery for the ANWR, Jorgenson et al. (2018) estimated that 18% of the area had been altered over the past 50 years, mainly by wildfire and postfire succession, shrub and tree increase in the absence of fire, river erosion and deposition, and ice-wedge deg- radation. Changes in tundra communities tended to be related to landscape wetting, mainly from increased wet troughs caused by ice-wedge degradation. Boreal forest cover showed changes associated with landscape drying and decreases in lake area. Prior to this, Pattison and Welker (2014) found that decreasing snow cover was detrimental to tundra plants in northern Alaska, particularly for various species of shrubs and grasses, including the diamond-leaf willow (Salix pulchra) and tussock cottongrass (Eriophorum vaginatum). As snow depth declined, so too did general productivity of these species throughout the growing season. To evaluate satellite imagery for vegetation greening trends in northern Alaska, Pattison et al. (2015) reported on changes in species composition for coastal plain field plots in the ANWR from 1984 to 2009. They linked these changes to the trends in the normalized greenness vegetation index (NDVI) at both fine and coarse scales. Field plot data implied few changes in plant community compo- sition and no detectable increases in total vegetative cover. Deciduous shrub cover did not show large increases. Field-measured NDVI was positively correlated to deciduous and evergreen shrub composition, suggesting that these functional groups had a strong influence on NDVI values, but the field data showed that NDVI did not change over time on these tundra types. Although Landsat (30 m) NDVI was consistent with field-measured NDVI, NDVI at 1-km resolution from the National Oceanic and Atmospheric Administration Advanced Very High Resolution Radiometer (AVHRR) satellite record was not. AVHRR NDVI values showed increases that were in neither the field-measured nor Landsat NDVI records. This result suggested that AVHRR may be demonstrating increasing trends in NDVI that are not occurring on the ground in some Arctic tundra eco- systems. To date, most of the large-scale studies of vegetation greening or browning in Alaska have not included comprehensive structural breaks analysis, designed to simultaneously detect all major disturbances that can alter greening trend statistics and the conclusions about gradual change in vegetation cover density and tundra or shrubland health. Gradual change analysis applied to a time series is designed to test for changes in the coefficients of a regression model, and generally assumes that there is just a single change under the alternative or that the timing and the type of change are known (Zeileis et al. 2002). A structural break can occur when a time series abruptly changes at a point in time. Detection of multiple breaks or disturbances in a time series of NDVI can occur in wilderness areas as a result of periodic wildfires, insect outbreaks, and/or from repeated cycles of extreme weather events. The objective of this study was to detect both abrupt and gradual changes in vegetation cover throughout the ANWR since the year 2000 using the 250-m- resolution regional MODIS NDVI record for structural change analysis. The principal question posed in this analysis of the highest-spatial-resolution MODIS NDVI available, and the longest time series yet tested, was, Has the green vege- tation cover changed over large areas in the ANWR since the year 2000 and particularly along major caribou migration routes? Statistical analysis of changes Unauthenticated | Downloaded 09/29/21 01:06 AM UTC Earth Interactions d Volume 23 (2019) d Paper No. 4 d Page 4 Figure 1. Study area of the ANWR in northeastern Alaska showing Landsat NLCD vegetation classes (Selkowitz and Stehman 2011). in the MODIS NDVI time series was conducted using the breaks for additive seasonal and trend method (BFAST; Verbesselt et al. 2010a,b; de Jong et al. 2012). 2. Study area The ANWR covers nearly 80 000 km2 from the Beaufort Sea coast in the north, across the Brooks Range to the boreal forest and tributaries of the Yukon River in the south (Figure 1). The mean annual temperature is below freezing, and all parts of the ANWR are underlain by continuous permafrost, except for larger river valleys in the far southern portion (Jorgenson et al. 2018). Tundra vegetation predominates from the Brooks Range to the coastal plain, composed mainly of dwarf shrubs, sedges, and mosses (USFWS 2015). Boreal forest vegetation is found south of the Brooks Range. White and black spruce forests predominate in the northern portion of the subarctic lowlands, whereas the uplands support moist sedge–shrub tundra.
Load more

Recommended publications
  • Public Use Summary Arctic National Wildlife Refuge
    U.S. Fish & Wildlife Service Public Use Summary Arctic National Wildlife Refuge April 2010 Arctic National Wildlife Refuge 907/456-0250 800/362-4546 [email protected] http://arctic.fws.gov/ Report Highlights: This report contains a summary of historic visitor use information compiled for the area now designated within the Arctic National Wildlife Refuge boundary (up to 1997); depicts a general index of recent visitor use patterns (1998-2009) based upon available data; summarizes available harvest data for general hunting and trapping; and discusses current trends in public use with implications for future management practices. Recent visitor use patterns include: Visitation has generally remained steady since the late 1980s, averaging around 1000 visitors, yet at the same time there has been a steady increase in the number of commercial permits issued. The Dalton Highway serves as a significant access corridor to the Refuge. The highway passes less than a mile from Atigun Gorge, which has experienced a steady increase in visitation. The majority of visitors float rivers, while hiking/backpacking and hunting comprise other major user activities. Across activity types, more than half of the commercially-supported visitation is guided. On average, where locations are known, about 77% of overall commercially-supported visitation occurs north of the Brooks Range, while about 23% occurs on the south side. Nearly one-quarter (21%) of the commercially-supported visitors to the Refuge visit the Kongakut River drainage on the north side of the Brooks Range. Commercially guided or transported recreational visitors spend, on average, about nine days in the Refuge, in groups that average around five individuals.
    [Show full text]
  • Porcupine River
    draft wild and scenic river study february 1984 PORCUPINE RIVER ALASKA I I I I I I I I I I I I I I I I I I I I I DRAFT I­ WILD AND SCENIC RIVER STUDY I PORCUPINE RIVER ALASKA I I Abstract: The study finds that although the Porcupine River is eligible for the National Wild and Scenic Rivers System, it is nonsuitable for inclusion. The report describes and evaluates four alternatives, I including the recommendation of no action. Comments: Comments on this draft study are invited from all interested parties and should be forwarded to the following official no later I than Regional Director I Alaska Regional Office National Park Service 2525 Gambell Street I Anchorage, Alaska 99503-2892 I I I I I I I U. S. Department of the Interior / National Park Service I I I I I I I I I I I I I I I" I I I. I I I I SUMMARY I Study of the Porcupine River to determine its eligibility and suitability for possible inclusion by Congress in the National Wild and Scenic Rivers System was mandated in the Alaska National Interest Lands Conservation I Act of December 2, 1980 (PL 96-487). The Porcupine River is a 472-mile-long free-flowing, unpolluted river that originates in Canada. The study area comprises the 212-mile segment I from the Canadian-U .S. border to its mouth on the Yukon River. This entire river segment is eligible for inclusion in the National Wild and Scenic Rivers System.
    [Show full text]
  • Caribou Management Report of Survey and Inventory Activities 1 July 2012–30 June 2014
    SPECIES Alaska Department of Fish and Game Division of Wildlife Conservation MANAGEMENT REPORT (907) 465-4190 – PO Box 115526 Juneau, AK 99811-5526 CHAPTER 15: CARIBOU MANAGEMENT REPORT From: 1 July 2012 To: 30 June 20141 LOCATION 2 GAME MANAGEMENT UNITS: 25A, 25B, 25D, and 26C (59,400 mi ) HERD: Porcupine GEOGRAPHIC DESCRIPTION: Eastern portions of the Arctic Slope, Brooks Range, and northeastern Interior Alaska BACKGROUND The Porcupine caribou herd (PCH) migrates between Alaska and the Yukon and Northwest Territories in Canada. Most of the herd’s 130,000 mi2 range is remote, roadless wilderness. The PCH is an important subsistence resource for Native people of Alaska and Canada. In addition, PCH provides valued hunting and wildlife viewing opportunities for nonlocal Alaska residents and nonresidents. Because the PCH often calves in promising onshore petroleum prospects in Alaska (Clough et al. 1987), various state and federal agencies and their Canadian counterparts cooperated to carry out baseline ecological studies of the PCH in the 1980s and 1990s (Fancy and Whitten 1991, Whitten and Fancy 1991, Whitten et al. 1992, Fancy et al. 1994, Griffith et al. 2002). These studies are expected to provide baseline information for development of additional studies, planning, and mitigation should petroleum development occur in the future. Since these studies, research of the PCH has been substantially reduced and efforts have been focused on monitoring population parameters to evaluate management objectives. In 1987 the United States and Canada established the International Porcupine Caribou Board (IPCB) to coordinate management and research among government and user groups. IPCB includes a representative from the Alaska Department of Fish and Game (ADF&G), representatives of the governments of the United States, Canada, Yukon and Northwest Territories, and members of communities and Native organizations in Alaska and Canada.
    [Show full text]
  • Arctic Region Human Use of Fish and Wildlife
    Alasha Habitat Management Guide Arctic Region Volume II: Distribution, Abtrndance, and Human Use of Fish and Wildlife Produced by State of Alasha Department of Fish and @me Division of Habitat Iun@u, Alasha r986 @Tgge BYTHE AI ASKA DEPARTMENT OF FISH AT.ID GA}TE Contents DISTRIBUTION AT{D ABUNDAIICE OF SELECTED FISH AI{D WILDLIFE Wildlife Marine Marmals wtral e 3 Regionwide 3 -B'eTuTh-aBeaufort Sea 3 Chukchi and Bering seas 4 Bowhead wha'le 11 Regionwide 11 Pacific walrus 19 Regionwide 19 Pol ar bear 27 Regionwide 27 Northern Alaska subpopulation 31 Western Alaska subpopulation 32 Ri nged sea'l 35 Regionwide 35 wTerrestrial Mammals Regionwide 41 Caribou 49 Regionwide 49 Porcupine Herd (PH) 91 Centra'l Arctic Herd (CAH) 93 Western Arct'ic Herd (I,JAH) 95 Teshepuk Herd (TH) 97 Dal I sheep Regionwide 1O7 GMU 23 110 GMU 24 LIz GMU 25A 113 GMU 26C 114 GMU 268 115 GMU 26A 115 Moose Regionwide 119 GMU 22 L22 GMU 23 L23 GMU 26 I24 ut Contents (contjnued) Bi rds Ducks and geese 13i Regionwide 131 Arctjc slope area 136 Seward Peninsula/Kotzebue Sound 143 Fish Freshwater/Anadromous Fi sh en 153 Regionwide 153 Seward Peninsula-Norton Sound Area I57 Northwest Alaska Area 157 North Slope Brooks Range Area 159 Arctic arayl ing Regionwide 173 Seward Peninsula-Norton Sound Area 176 Northwest Alaska Area 176 North Slope Brooks Range Area 177 Broad whitefish 181 Regionwide 181 Seward Peninsula-Norton Sound Area 787 Northwest Alaska Area I87 North S'lope Brooks Range Area I87 Lake trout 193 Reg i onw'i de 193 Seward Peninsula-Norton Sound Area 195 Northwest
    [Show full text]
  • Lower Sheenjek ~River, Alaska
    Final Wild and Scenic River Study and Legislative Environmental Impact Statement Lower Sheenjek ~River, Alaska ,,,,,,: . t!:~~~,Department of the Inte~ltJr ,, .,;,r' · ··· ·· National Park Service Fish and Wildlife Service United States Department of the Interior NATIONAL PARK SERVICE 2525 Gambell Street, Room 107 Anchorage, Alaska 99503-2892 L'>: REPLY REFER TO, L32 (RTCA-Sheenjek) OCT 2 0 IS'99 Dear Reviewer: Enclosed for your information is the combined final Lower Sheenjek Wild and Scenic River Study and Legislative Environmental Impact Statement (final study/LEIS). The final study/LEIS was required by Section 5(a) of the Wild and Scenic Rivers Act as amended by Section 604 of the Alaska National Interest Lands Conservation Act. It evaluates the segment of the Sheenjek River from its mouth to the northern boundary of the Yukon Flats National Wildlife Refuge, a distance of about 99 river miles. · The final study/LEIS was done cooperatively by the US Fish and Wildlife Service and National Park Service, as the latter agency was delegated Wild and Scenic River study responsibility by the Secretary of the Interior. The study began in the early 1980's with a draft study/LEIS mailed out for public comment in the fall of 1984. It recommended designation of the study segment by Congress that was supported by the majority of comments received. Funding and administrative constraints, however, prevented completion of the Study/LEIS process. The effort resumed in 1997, but the intervening time required updating the earlier work and additional public involvement to ensure that information was accurate and up-to-date.
    [Show full text]