Mapping and modeling attributes of an Arctic-Boreal biome shift

Lead

Scott Goetz

Keywords

Arctic tundra, boreal forest, remote sensing, climate change, modeling, vegetation, mapping, shrub, lichen

This project, part of the Arctic Boreal Vulnerability Experiment (ABoVE), is designed to assess the evidence for vegetation changes and transitions consistent with expectations of a biome shift resulting from changing climate in the high latitudes of North America. We are investigating the implications of such a shift on both flora and fauna, and exploring options for resource management adaptation to change.

This project is part of ABoVE. More information about this project can be found here.

Determining the vulnerability and resilience of boreal forests and shrubs across Northwestern North America

Lead

Rosanne D’Arrigo (Lamont Doherty Earth Observatory)

co-lead

Scott Goetz

Keywords

Vulnerability, resilience, remote sensing, tree-ring studies, greening, browning, biome shift

This project’s integration of remote sensing and tree-ring studies of vegetation will yield a comprehensive assessment of the impact of climatic and environmental change on tree and shrub growth across the taiga and tundra ecosystems of northwestern North America, provide insight into their vulnerability and resilience, and allow inferences to be made on how they are likely to be altered in the future. Tree and shrub growth in the Arctic is important because it regulates climate through a range of feedback mechanisms that are not only complex but also rapidly changing with climate warming.

This project is funded by NSF’s Arctic Natural Sciences program and is affiliated with ABoVE. More information about this project can be found here.

Understanding the causes and implications of enhanced seasonal CO₂ exchange in Boreal and Arctic ecosystems

Lead

Brendan Rogers

co-lead

Scott Goetz

Keywords

CO₂ flux, climate change, productivity, respiration, process model, boreal, arctic

During the last half century, the magnitude of seasonal variability in CO₂ exchange has increased by 30-50% in high latitude environments, with two thirds of this change attributed to increased CO₂ flux in boreal forest and arctic tundra. Mechanisms for this change have been identified but the relative contributions of each of these mechanisms are not well understood. Given that these increases in seasonal CO₂ flux impact carbon cycling and climate feedback in boreal forest and tundra ecosystems, it is important to fully understand the underlying mechanisms.

This project is funded by the NASA Carbon Cycle and Ecosystems Project and is affiliated with ABoVE. More information about this project can be found here.

Arctic-Boreal regions (ABRs) of North America are warming at a rate almost three times higher than the global average, and the biophysical responses are acute. Most regional scale studies to date have explored consequences on biogeochemical cycling and energy balance. Far less attention has been paid to the vulnerability and resilience of wildlife throughout the ABR, despite the fact that the region hosts the planet’s most diverse neotropical migrant songbird communities; caribou, which are among the most abundant long range migratory large herbivores in the Northern Hemisphere; and intact yet threatened mammalian trophic systems. Many ABR species play unique ecological roles and are of cultural and economic significance to indigenous people. Our overarching science goal is to understand how highly mobile terrestrial fauna navigate and select habitat in the rapidly changing ABoVE Study Domain. We are using space-based wildlife tracking technology to build an integrated dataset of regional-scale and near-continuous descriptions of passerine (American robins), raptor (Golden Eagles), ungulate (caribou, moose), and predator (wolf and brown bear) locations with both static and dynamic remote sensing products and other regional-scale geospatial datasets (Obj.1). We will use this data to build empirically based statistical movement and habitat selection models for multiple groups of animals across the ABoVE Study Domain (Obj.2). The geospatial tools and products will be made accessible to natural resource agencies, wildlife managers, First Nations, Alaskan natives, and other stakeholders to aid them in management and adaptation decisions (Obj.3).

We are using time-series of VHF and GPS spatial telemetry location data from 1993 – present within the Fortymile caribou herd range to characterize how caribou use available habitats in the Fortymile caribou range.  Using spatial environmental products, we are identifying the caribou habitat features and environmental covariates that are most important to maintaining widespread and productive caribou numbers within the Fortymile caribou range using Resource Selection Functions (RSFs).  These habitat and movement models are being used across spatiotemporal scales to understand the effects of landuse change, fire, and climate change on the spatial distribution of caribou habitat over time.  We are working closely with Alaska Department of Fish and Game (ADFG) partners to link these changes in habitat to population consequences.  We are also using intensive field sampling and unmanned aerial vehicles (UAVs) to collect data on lichen and other important caribou forage plant functional types (PFTs, e.g. shrubs, graminoids, forbs) and map above-ground biomass of these PFTs across time and space.  This is done across a spatial gradient of Fortymile caribou herd density to understand potential impacts of overgrazing on this high density caribou herd.  These models will also allow us to track grazing impacts on available forage over time using historic telemetry location data.

Arctic regions are experiencing some of the fastest rates of climate warming in the world. These regions are poised for significant changes in vegetation composition and structure, which in turn affect carbon cycling. Vegetation and carbon cycle changes have the potential to impact one of the region’s most ecologically, culturally, and economically important species: barren-ground caribou.   In addition, caribou have the potential to affect tundra vegetation, creating complicated interactions among herbivore assemblages, climate, and vegetation structure and function. Of particular importance is the potential of caribou to impact ecosystem responses to climate change.

As one of only two large herbivores present in the North American Arctic, caribou play an important role in shaping future Arctic climate and vegetation communities. They will also be acutely affected by changes in climate and vegetation. To understand these interactions, and make accurate predictions about Arctic response to climate change, it is important to both quantify these effects, and explicitly include herbivory in models of Arctic climate and carbon – to “animate” the carbon cycle.

Our work seeks to bridge the gap between small-scale experimental research on arctic herbivore-vegetation interactions, and coarse spatial resolution remote sensing efforts examining these same impacts.  We are using a combination of field data, UAV imagery, airborne imagery and satellite imagery to quantifying plant functional type biomass at 30 m resolution across barren-ground caribou ranges in Arctic Alaska and Northwest Canada.  Products such as these can be used in conjunction with caribou location data to assess caribou-vegetation interactions.

New remote sensing methods and instruments for topographic mapping have greatly increased the availability of gridded elevation datasets covering Earth’s surface. This wave of new data will be particularly impactful for high northern latitudes (> 60 degrees N) which currently lack a singular, extensive high-resolution dataset (such as the Shuttle Radar Topography Mission [SRTM] for low- to mid-latitudes). Our work is initially focused on creating a gap-free digital surface model (DSM) composite for the NASA ABoVE study domain which covers Arctic and Boreal regions of North America. Existing publicly available datasets covering this domain include Alaska airborne IFSAR, ArcticDEM, ALOS World 3D 30m, SRTM, Canada DEM (CDEM), ASTER GDEM, and GMTED2010. None of the existing datasets provide full (gap-free) coverage over the entire study domain at moderate- to high-spatial resolution. When attempting to simply mosaic these source datasets together complications arise due to different datums, acquisition timeframes, and inherent artifacts. We use a combination of GDAL and the NASA Ames Stereo Pipeline (ASP) to process the source datasets and combine them into a single composite DSM for the entire NASA ABoVE study domain at 10m spatial resolution. GDAL is used to transform all datasets so that they reference the same horizontal and vertical reference frames. ASP is used to co-register and composite the datasets using a prioritization scheme. Vertical accuracy of the new composite DSM is assessed using a variety of datasets including airborne lidar (LVIS), spaceborne lidar (GLAS), and airport runway elevations.

Lead

Michelle Mack (NAU)

Co-Lead

Scott Goetz

Keywords

Legacy carbon, climate change, fire, soil organic layer, carbon cycle, permafrost

Climate warming is resulting in increased fire frequency, extent and severity at northern latitudes.  A significant amount of organic carbon in Arctic and boreal regions is stored in the soil organic layer, and thus carbon released from wildfires as a result of soil organic layer combustion is an important component of the Arctic-boreal ecosystem carbon balance.  Of particular importance is “legacy carbon” – soil organic layer carbon pools that have survived previous fires.  Combustion of this legacy carbon has the potential to cause a dramatic shift in Arctic-boreal carbon cycling – from a net sink, to a net source.  We are identifying ecosystem, landscape and regional factors that control legacy carbon consumption.  This will allow us to assess the effect loss of legacy carbon has on permafrost, soil drainage, carbon cycling, and post fire vegetation recovery.

For more information on this project, see Dr. Mack’s website.

Climate as a driver of shrub expansion and tundra greening

Lead

Isla Meyers-Smith (University of Edinburgh)

Co-Lead

Scott Goetz

Keywords

Shrub expansion, climate change, arctic greening, plant productivity, remote sensing

Global warming is happening faster at the poles than anywhere else on Earth. This has implications for vegetation dynamics in arctic tundra. Research has noted trends of increasing plant productivity and biomass, dubbed arctic “greening.”  Shrubs in particular appear to be expanding in arctic systems.  Shrubs are an important part of the Arctic carbon cycle and major contributors to feedbacks facilitating high-latitude climate warming.  Our goal is to quantify the role of climate in arctic “greening” and shrub expansion.  We are combining field data and remotely-sensed imagery (drone and satellite based) to quantify the strength of climate drivers on shrub expansion, and the rate and extent of shrub expansion.

For more information on this project, see here and here.

Winter respiration in the Arctic: Constraining current and future estimates of CO₂ emissions during the non-growing season

Lead

Susan Natali (Woods Hole Research Center)

Co-Lead

Scott Goetz

Keywords

Winter respiration, CO₂ emissions, climate change, remote sensing, CO₂ flux

Air temperatures in the Arctic have increased at approximately twice the global rate, with the greatest warming occurring during the winter months. This increase in winter temperature might lead to permafrost thaw, increased winter microbial respiration, and thus increased release of CO₂ to the atmosphere.  Non-growing season (winter, fall and spring) CO₂ emissions are therefore an important aspect of annual CO₂ emissions, but current estimates of non-growing season CO₂ have large associated uncertainties.  We are using site level CO₂ flux measurements, along with satellite remote sensing data, to measure winter respiration and produce regional estimates of CO₂ emissions during the non-growing season.  These improved estimates will allow us to better understand carbon flux in Arctic regions.

More information about this project can be found here.