Canopy reflectance models illustrate varying NDVI responses to change in high latitude ecosystems

Huemmrich, K. F.; Zesati, S. A. Vargas; Campbell, P. K. E.; Tweedie, C. E.

doi:10.1002/eap.2435

Cited by 15 publications

(12 citation statements)

References 45 publications

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“…It is also likely that important ecological responses to climate change could be occurring in areas where remotely sensed metrics of vegetation greenness show no long‐term trend. For example, spruce or larch recruitment might minimally affect vegetation greenness in shrubby landscapes (Huemmrich et al, 2021 ; Loranty et al, 2018 ), as might low levels of tree mortality where the growth of surviving trees is enhanced by reduced competition (Boyd et al, 2021 ). To better understand variability in boreal forest resilience to future climatic changes, it will be necessary to further develop and apply mechanistic ecological models that simulate species‐specific responses to changes at fine spatial scales (Foster et al, 2019 ).…”

Section: Discussionmentioning

confidence: 99%

“…Changes in Landsat NDVI have been linked with spatial or temporal variation in ecosystem productivity, forest productivity, tree growth, shrub growth, aboveground biomass, and vegetation mortality at field sites in high northern latitudes (Table 2 ). However, Landsat NDVI can saturate in dense forests, likely hindering detection of greening and biasing observed trends toward browning under such conditions (Huemmrich et al, 2021 ). We therefore also used three newer vegetation indices that are likely less prone to saturation and better indicators of vegetation dynamics, though their performance has not been thoroughly evaluated in high northern latitudes (Badgley et al, 2017 ; Camps‐Valls et al, 2021 ; Jiang et al, 2008 ).…”

Section: Discussionmentioning

confidence: 99%

“…After masking out (Olson et al, 2001) 1a). We processed geospatial data with the raster (Hijmans, 2019) and gdalUtilities (O'Brien, 2019) packages in the statistical software R (version 4.0) (R Core Team, 2021), with subsequent data handling and visualization facilitated by the packages data.table (Dowle & Srinivasan, 2021), dplyr (Wickham et al, 2021), tidyr (Wickham, 2021), ggplot2 (Wickham, 2016), and ggpubr (Kassambara, 2020).…”

Section: Identifying Recently Undisturbed Areas In the Boreal Forestmentioning

confidence: 99%

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Satellite observations document trends consistent with a boreal forest biome shift

Berner

Goetz

2022

Global Change Biology

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The boreal forest biome is a major component of Earth's biosphere and climate system that is projected to shift northward due to continued climate change over the coming century. Indicators of a biome shift will likely first be evident along the climatic margins of the boreal forest and include changes in vegetation productivity, mortality, and recruitment, as well as overall vegetation greenness. However, the extent to which a biome shift is already underway remains unclear because of the local nature of most field studies, sparsity of systematic ground‐based ecological monitoring, and reliance on coarse resolution satellite observations. Here, we evaluated early indicators of a boreal forest biome shift using four decades of moderate resolution (30 m) satellite observations and biogeoclimatic spatial datasets. Specifically, we quantified interannual trends in annual maximum vegetation greenness using an ensemble of vegetation indices derived from Landsat observations at 100,000 sample sites in areas without signs of recent disturbance. We found vegetation greenness increased (greened) at 38 [29, 42] % and 22 [15, 26] % of sample sites from 1985 to 2019 and 2000 to 2019, whereas vegetation greenness decreased (browned) at 13 [9, 15] % and 15 [13, 19] % of sample sites during these respective periods [95% Monte Carlo confidence intervals]. Greening was thus 3.0 [2.6, 3.5] and 1.5 [0.8, 2.0] times more common than browning and primarily occurred in cold sparsely treed areas with high soil nitrogen and moderate summer warming. Conversely, browning primarily occurred in the climatically warmest margins of both the boreal forest biome and major forest types (e.g., evergreen conifer forests), especially in densely treed areas where summers became warmer and drier. These macroecological trends reflect underlying shifts in vegetation productivity, mortality, and recruitment that are consistent with early stages of a boreal biome shift.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Identifying Recently Undisturbed Areas In the Boreal Forestmentioning

confidence: 99%

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Satellite observations document trends consistent with a boreal forest biome shift

Berner

Goetz

2022

Global Change Biology

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“…Recent studies have highlighted the spatial heterogeneity in Arctic ecosystem responses to climate change that not only includes greening trends, but notable vegetation-browning signals (Bhatt et al 2013, Appenzeller 2015, Myers-Smith et al 2020, Huemmrich et al 2021, Berner and Goetz 2022. The seemingly inconsistent responses to increasing temperatures are attributed to significant climate events and physical and biological forces that could result from the changes in water availability between the onset and ending of the photosynthetic period (Park et al 2019).…”

Section: Introductionmentioning

confidence: 99%

Climate change is enforcing physiological changes in Arctic Ecosystems

Madani

Parazoo

Miller

2023

Environ. Res. Lett.

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Remote sensing and site-level observations have shown unprecedented changes in Arctic ecosystems owing to climate warming. These observations include greening and browning trends in Arctic vegetation as well as changes in species composition both in the tundra and the boreal forests. Here, we leveraged solar induced chlorophyll fluorescence (SIF) to study changes in ecosystem phenology across the pan-Arctic domain from 2000–2020. Ecoregions, as a proxy for plants’ functional traits, were the single most important variable to explain the spatial and phenological heterogeneity in observed SIF trends. We observed unique regional trends in ecosystems responses to climate change affecting the timing of spring photosynthesis onset, magnitude of peak productivity during the growing season and fall senescence. While, Photosynthetic activity in the early growing season showed increasing trends across the vast majority of the pan-Arctic, it tends to decline at the end of the season for nearly half of the land area, including parts of North America but more significantly in central Siberia. The observed changes in phenology highlight the role of biodiversity in regional climate sensitivity and emphasizes the need for better representations of sub-biomes to community level information in Arctic ecosystem process models and projections. These results also highlight the importance of phenology information in ecosystem models for better understanding of the timing and magnitude of carbon uptake towards better understanding and predicting ecosystem dynamics in the arctic domain with accelerated changes in climate.

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“…Variations in greening/browning over different years have most commonly been attributed to climate warming (e.g., Berner et al., 2020; Bhatt et al., 2021; Cooper, 2014), herbivory by small mammals (Olofsson et al., 2012), and vegetation disturbance and subsequent recovery after extreme warming events (Bokhorst et al., 2012). However, there are significant limitations of the sensitivity of NDVI to high latitude ecosystem change (Huemmrich et al., 2021). For example, recent evidence suggests that some of these changes' impacts are fine‐scale in nature (i.e., <5–30 m), making many common remote sensing platforms impractical for studying these dynamics (Myers‐Smith et al., 2020; Niittynen et al., 2020).…”

Section: Uses Of Spectroscopy For Tundra Studiesmentioning

confidence: 99%

Remote Sensing of Tundra Ecosystems Using High Spectral Resolution Reflectance: Opportunities and Challenges

et al. 2022

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Observing the environment in the vast regions of Earth through remote sensing platforms provides the tools to measure ecological dynamics. The Arctic tundra biome, one of the largest inaccessible terrestrial biomes on Earth, requires remote sensing across multiple spatial and temporal scales, from towers to satellites, particularly those equipped for imaging spectroscopy (IS). We describe a rationale for using IS derived from advances in our understanding of Arctic tundra vegetation communities and their interaction with the environment. To best leverage ongoing and forthcoming IS resources, including NASA's Surface Biology and Geology mission, we identify a series of opportunities and challenges based on intrinsic spectral dimensionality analysis and a review of current data and literature that illustrates the unique attributes of the Arctic tundra biome. These opportunities and challenges include thematic vegetation mapping, complicated by low-stature plants and very fine-scale surface composition heterogeneity; development of scalable algorithms for retrieval of canopy and leaf traits; nuanced variation in vegetation growth and composition that complicates detection of long-term trends; and rapid phenological changes across brief growing seasons that may go undetected due to low revisit frequency or be obscured by snow cover and clouds. We recommend improvements to future field campaigns and satellite missions, advocating for research that combines multi-scale spectroscopy, from lab studies to satellites that enable frequent and continuous long-term monitoring, to inform statistical and biophysical approaches to model vegetation dynamics.

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Canopy reflectance models illustrate varying NDVI responses to change in high latitude ecosystems

Cited by 15 publications

References 45 publications

Satellite observations document trends consistent with a boreal forest biome shift

Satellite observations document trends consistent with a boreal forest biome shift

Climate change is enforcing physiological changes in Arctic Ecosystems

Remote Sensing of Tundra Ecosystems Using High Spectral Resolution Reflectance: Opportunities and Challenges

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