Calibration and Validation of Landsat Tree Cover in the Taiga−Tundra Ecotone

Montesano, P.; Neigh, C. S. R.; Sexton, Joseph O.; Feng, Min; Channan, Saurabh; Ranson, K.J.; Townshend, J. R. G.

doi:10.3390/rs8070551

Cited by 33 publications

(25 citation statements)

References 52 publications

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“…Hufkens et al [97] validated a sigmoid wave curve fitting algorithm to detect and quantify a forest-tundra ecotone based on Landsat ETM+ data in the Northwest Territories, Canada. The evaluation of a global forest cover map based on Landsat showed that forests closely matched canopies of at least 2 m in height in the tundra-taiga transition zone [98]. Apart from distinguishing forest from non-forested areas, shrubs were studied in the transition zone.…”

Section: Changing Land Cover and Transition Zonesmentioning

confidence: 99%

Land Cover Mapping in Northern High Latitude Permafrost Regions with Satellite Data: Achievements and Remaining Challenges

et al. 2016

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Most applications of land cover maps that have been derived from satellite data over the Arctic require higher thematic detail than available in current global maps. A range of application studies has been reviewed, including up-scaling of carbon fluxes and pools, permafrost feature mapping and transition monitoring. Early land cover mapping studies were driven by the demand to characterize wildlife habitats. Later, in the 1990s, up-scaling of in situ measurements became central to the discipline of land cover mapping on local to regional scales at several sites across the Arctic. This includes the Kuparuk basin in Alaska, the Usa basin and the Lena Delta in Russia. All of these multi-purpose land cover maps have been derived from Landsat data. High resolution maps (from optical satellite data) serve frequently as input for the characterization of periglacial features and also flux tower footprints in recent studies. The most used map to address circumpolar issues is the CAVM (Circum Arctic Vegetation Map) based on AVHRR (1 km) and has been manually derived. It provides the required thematic detail for many applications, but is confined to areas north of the treeline, and it is limited in spatial detail. A higher spatial resolution circumpolar land cover map with sufficient thematic content would be beneficial for a range of applications. Such a land cover classification should be compatible with existing global maps and applicable for multiple purposes. The thematic content of existing global maps has been assessed by comparison to the CAVM and regional maps. None of the maps provides the required thematic detail. Spatial resolution has been compared to used classes for local to regional applications. The required thematic detail increases with spatial resolution since coarser datasets are usually applied over larger areas covering more relevant landscape units. This is especially of concern when the entire Arctic is addressed. A spatial resolution around 30 m has been shown to be suitable for a range of applications. This implies that the current Landsat-8, as well as Sentinel-2 missions would be adequate as input data. Recent studies have exemplified the value of Synthetic Aperture Radar (SAR) in tundra regions. SAR missions may be therefore of added value for large-scale high latitude land cover mapping. Remote Sens. 2016, 8, 979 2 of 27with climate change in the upcoming decades [2]. It has been pointed out by a range of studies (e.g., Westermann et al. [1] and Ottle et al. [3]) that there is a need for accurate land cover description in the northern high latitudes. A suitable circumpolar map does not yet exist to date, although a range of studies demonstrated the suitability of satellite data for this purpose on local and regional scales.A first review on traditional Arctic land cover maps as a baseline for the development of a circumpolar map was already published in 1995 by Walker et al. [4]. The Circum-Arctic Vegetation Map (CAVM) has in the following been developed using satellite data (Advanced Very Hi...

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Section: Changing Land Cover and Transition Zonesmentioning

confidence: 99%

Land Cover Mapping in Northern High Latitude Permafrost Regions with Satellite Data: Achievements and Remaining Challenges

et al. 2016

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“…However, improved representation of tall deciduous shrubs is highly desired because of their recent expansion and associated influence on ecosystem properties in northern Alaska. Future efforts to distinguish and monitor this PFT could combine optical remote sensing predictors with canopy height models derived from emerging tools such as LiDAR and drone photogrammetry; recent work in the forest-tundra ecotone highlights the potential for the use of LiDAR in tandem with optical satellite data to map vegetation canopy properties [57].…”

Section: Correspondence Of Pfts and Environmental Gradientsmentioning

confidence: 99%

“…Future modeling efforts should focus on identifying predictors or modeling approaches to improve the representation of low and high cover values for each PFT. A linear adjustment to the estimates is one approach that has been applied to reduce the bias of cover estimates in the taiga-tundra ecotone [57].…”

Section: Model Validationmentioning

confidence: 99%

Regional Quantitative Cover Mapping of Tundra Plant Functional Types in Arctic Alaska

et al. 2017

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Ecosystem maps are foundational tools that support multi-disciplinary study design and applications including wildlife habitat assessment, monitoring and Earth-system modeling. Here, we present continuous-field cover maps for tundra plant functional types (PFTs) across~125,000 km 2 of Alaska's North Slope at 30-m resolution. To develop maps, we collected a field-based training dataset using a point-intercept sampling method at 225 plots spanning bioclimatic and geomorphic gradients. We stratified vegetation by nine PFTs (e.g., low deciduous shrub, dwarf evergreen shrub, sedge, lichen) and summarized measurements of the PFTs, open water, bare ground and litter using the cover metrics total cover (areal cover including the understory) and top cover (uppermost canopy or ground cover). We then developed 73 spectral predictors derived from Landsat satellite observations (surface reflectance composites for~15-day periods from May-August) and five gridded environmental predictors (e.g., summer temperature, climatological snow-free date) to model cover of PFTs using the random forest data-mining algorithm. Model performance tended to be best for canopy-forming PFTs, particularly deciduous shrubs. Our assessment of predictor importance indicated that models for low-statured PFTs were improved through the use of seasonal composites from early and late in the growing season, particularly when similar PFTs were aggregated together (e.g., total deciduous shrub, herbaceous). Continuous-field maps have many advantages over traditional thematic maps, and the methods described here are well-suited to support periodic map updates in tandem with future field and Landsat observations.

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“…Methods that capitalize on the new features of these data will provide a means for resolving detailed patterns of vertical and horizontal vegetation structure across remote portions of the boreal forest (Montesano et al, ). Structural parameters, such as height, cover, stem density, and aboveground biomass, can be informed by textural characteristics, which quantify the variation in contrast according to the illumination of image features and their scattering (Berner et al, ; Kayitakire et al, ; Montesano et al, ; Wood et al, ; Wulder et al, ; Wulder et al, ). These fine‐scale properties will provide new insight into the distribution of plant functional types, disturbances, productivity, land‐atmosphere interactions, and their changes through time.…”

Section: Observing Properties Of the Abz Landmentioning

confidence: 99%

Space‐Based Observations for Understanding Changes in the Arctic‐Boreal Zone

Duncan

Ott

Abshire

et al. 2020

Reviews of Geophysics

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Observations taken over the last few decades indicate that dramatic changes are occurring in the Arctic‐Boreal Zone (ABZ), which are having significant impacts on ABZ inhabitants, infrastructure, flora and fauna, and economies. While suitable for detecting overall change, the current capability is inadequate for systematic monitoring and for improving process‐based and large‐scale understanding of the integrated components of the ABZ, which includes the cryosphere, biosphere, hydrosphere, and atmosphere. Such knowledge will lead to improvements in Earth system models, enabling more accurate prediction of future changes and development of informed adaptation and mitigation strategies. In this article, we review the strengths and limitations of current space‐based observational capabilities for several important ABZ components and make recommendations for improving upon these current capabilities. We recommend an interdisciplinary and stepwise approach to develop a comprehensive ABZ Observing Network (ABZ‐ON), beginning with an initial focus on observing networks designed to gain process‐based understanding for individual ABZ components and systems that can then serve as the building blocks for a comprehensive ABZ‐ON.

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Calibration and Validation of Landsat Tree Cover in the Taiga−Tundra Ecotone

Cited by 33 publications

References 52 publications

Land Cover Mapping in Northern High Latitude Permafrost Regions with Satellite Data: Achievements and Remaining Challenges

Land Cover Mapping in Northern High Latitude Permafrost Regions with Satellite Data: Achievements and Remaining Challenges

Regional Quantitative Cover Mapping of Tundra Plant Functional Types in Arctic Alaska

Space‐Based Observations for Understanding Changes in the Arctic‐Boreal Zone

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