Arctic aquatic graminoid tundra responses to nutrient availability

Abstract. Unraveling the environmental controls influencing Arctic tundra productivity is paramount for advancing our predictive understanding of the causes and consequences of warming in tundra ecosystems and associated land–atmosphere feedbacks. This study focuses on aquatic emergent tundra plants, which dominate productivity and methane fluxes in the Arctic coastal plain of Alaska. In particular, we assessed how environmental nutrient availability influences production of biomass and greenness in the dominant aquatic tundra species: Arctophila fulva and Carex aquatilis. We sampled a total of 17 sites distributed across the Barrow Peninsula and Atqasuk, Alaska, following a nutrient gradient that ranged from sites with thermokarst slumping or urban runoff to sites with relatively low nutrient inputs. Employing a multivariate analysis, we explained the relationship of soil and water nutrients to plant leaf macro- and micro-nutrients. Specifically, we identified soil phosphorus as the main limiting nutrient factor given that it was the principal driver of aboveground biomass (R2=0.34, p=0.002) and normalized difference vegetation index (NDVI) (R2=0.47, p=0.002) in both species. Plot-level spectral NDVI was a good predictor of leaf P content for both species. We found long-term increases in N, P and Ca in C. aquatilis based on historical leaf nutrient data from the 1970s of our study area. This study highlights the importance of nutrient pools and mobilization between terrestrial–aquatic systems and their potential influence on productivity and land–atmosphere carbon balance. In addition, aquatic plant NDVI spectral responses to nutrients can serve as landscape hot-spot and hot-moment indicators of landscape biogeochemical heterogeneity associated with permafrost degradation, nutrient leaching and availability.

Download Full-text

Arctic aquatic graminoid tundra responses to nutrient availability

10.5194/bg-2020-351 ◽

2020 ◽

Author(s):

Christian G. Andresen ◽

Vanessa L. Lougheed

Keyword(s):

Nutrient Availability ◽

Vegetation Index ◽

Hot Spot ◽

Soil Phosphorus ◽

The Arctic ◽

Permafrost Degradation ◽

Nutrient Inputs ◽

Nutrient Pools ◽

Environmental Controls ◽

Predictive Understanding

Abstract. Unraveling the environmental controls influencing Arctic tundra productivity is paramount for advancing our predictive understanding of the causes and consequences of warming in tundra ecosystems and associated land-atmosphere feedbacks. This study focuses on aquatic emergent tundra plants, which dominate productivity and methane fluxes in the Arctic coastal plain of Alaska. In particular, we assessed how environmental nutrient availability influences production of biomass and greenness in the dominant aquatic tundra species: Carex aquatilis and Arctophila fulva. We sampled a total of 17 sites distributed across the Barrow Peninsula and Atqasuk, Alaska following a nutrient gradient that ranged from sites with thermokarst slumping or urban runoff to sites with relatively low nutrient inputs. Employing a multivariate analysis, we explained the relationship of soil and water nutrients to plant leaf macro- and micro-nutrients. Specifically, we identified soil phosphorus as the main limiting nutrient factor given that it was the principal driver of biomass and Normalize Difference Vegetation Index (NDVI) in both species. Plot-level spectral NDVI was a good predictor of leaf P content for both species. We found long-term increases in N, P and Ca in C. aquatilis based on historical leaf nutrient data from 1970s of our study area. This study highlights the importance of nutrient pools and mobilization between terrestrial-aquatic systems and their potential influence on productivity, carbon and energy balance. In addition, aquatic plant NDVI spectral responses to nutrients can serve as landscape hot-spot and hot-moment indicator of landscape biogeochemical heterogeneity associated with permafrost degradation, nutrient leaching and availability.

Download Full-text

Determining the terrain characteristics related to the surface expression of subsurface water pressurization in permafrost landscapes using susceptibility modelling

The Cryosphere ◽

10.5194/tc-11-1403-2017 ◽

2017 ◽

Vol 11 (3) ◽

pp. 1403-1415 ◽

Cited By ~ 6

Author(s):

Jean E. Holloway ◽

Ashley C. A. Rudy ◽

Scott F. Lamoureux ◽

Paul M. Treitz

Keyword(s):

Active Layer ◽

Vegetation Index ◽

Normalized Difference Vegetation Index ◽

Additive Model ◽

The Arctic ◽

Subsurface Water ◽

Permafrost Degradation ◽

Topographic Wetness Index ◽

Landscape Degradation ◽

Terrain Characteristics

Abstract. Warming of the Arctic in recent years has led to changes in the active layer and uppermost permafrost. In particular, thick active layer formation results in more frequent thaw of the ice-rich transient layer. This addition of moisture, as well as infiltration from late season precipitation, results in high pore-water pressures (PWPs) at the base of the active layer and can potentially result in landscape degradation. To predict areas that have the potential for subsurface pressurization, we use susceptibility maps generated using a generalized additive model (GAM). As model response variables, we used active layer detachments (ALDs) and mud ejections (MEs), both formed by high PWP conditions at the Cape Bounty Arctic Watershed Observatory, Melville Island, Canada. As explanatory variables, we used the terrain characteristics elevation, slope, distance to water, topographic position index (TPI), potential incoming solar radiation (PISR), distance to water, normalized difference vegetation index (NDVI; ME model only), geology, and topographic wetness index (TWI). ALDs and MEs were accurately modelled in terms of susceptibility to disturbance across the study area. The susceptibility models demonstrate that ALDs are most probable on hill slopes with gradual to steep slopes and relatively low PISR, whereas MEs are associated with higher elevation areas, lower slope angles, and areas relatively far from water. Based on these results, this method identifies areas that may be sensitive to high PWPs and helps improve our understanding of geomorphic sensitivity to permafrost degradation.

Download Full-text

Determining the terrain characteristics related to the surface expression of subsurface water pressurization in permafrost landscapes using susceptibility modelling

10.5194/tc-2016-183 ◽

2016 ◽

Author(s):

Jean E. Holloway ◽

Ashley C. A. Rudy ◽

Scott F. Lamoureux ◽

Paul Treitz

Keyword(s):

Active Layer ◽

Vegetation Index ◽

Normalized Difference Vegetation Index ◽

Additive Model ◽

The Arctic ◽

Subsurface Water ◽

Permafrost Degradation ◽

Topographic Wetness Index ◽

Landscape Degradation ◽

Terrain Characteristics

Abstract. Warming of the Arctic in recent years has led to changes in the active layer and uppermost permafrost. In particular, thick active layer formation results in more frequent thaw of the ice-rich transient layer. This addition of moisture, as well as infiltration from late season precipitation, results in high pore-water pressures (PWPs) at the base of the active layer and can potentially result in landscape degradation. To predict areas that have the potential for subsurface pressurization, we use susceptibility maps generated using a generalized additive model (GAM). As model response variables, we used active layer detachments (ALDs) and mud ejections (MEs), both formed by high PWP conditions at the Cape Bounty Arctic Watershed Observatory, Melville Island, Canada. As explanatory variables, we used the terrain characteristics elevation, slope, distance to water, topographic position index (TPI), potential incoming solar radiation (PISR), distance to water, normalized difference vegetation index (NDVI; ME model only), geology, and topographic wetness index (TWI). ALDs and MEs were accurately modelled in terms of susceptibility to disturbance across the study area. The susceptibility models demonstrate that ALDs are most probable on hill slopes with gradual to steep slopes and relatively low PISR, whereas MEs are associated with higher elevation areas, lower slope angles and in areas relatively far from water. Based on these results, this method identifies areas that may be sensitive to high PWPs, and helps improve our understanding of geomorphic sensitivity to permafrost degradation.

Download Full-text

Remote sensing assessment of glacial loss and vegetation change from 1989 to 2016: Pond Inlet, Nunavut

10.32920/ryerson.14667960.v1 ◽

2021 ◽

Author(s):

Ruby R. Pennell

Keyword(s):

Vegetation Change ◽

Vegetation Index ◽

Normalized Difference Vegetation Index ◽

Relevant Literature ◽

Arctic Tundra ◽

The Arctic ◽

Landscape Changes ◽

Storm Events ◽

Time Period ◽

Induced Changes

The climate change phenomenon occurring across the globe is having an increasingly alarming effect on Canada’s Arctic. Warming temperatures can have wide spanning impacts ranging from more rain and storm events, to increasing runoff, thawing permafrost, sea ice decline, melting glaciers, ecosystem disruption, and more. The purpose of this MRP was to assess the climate-induced landscape changes, including glacial loss and vegetation change, in Pond Inlet, Nunavut. A time series analysis was performed using the intervals 1989-1997, 1997-2005, and 2005-2016. The two methods for monitoring change were 1) the Normalized Difference Snow Index (NDSI) to detect glacial change, and 2) the Normalized Difference Vegetation Index (NDVI) to detect vegetation change, both utilizing threshold and masking techniques to increase accuracy. It was found that the percent of glacial loss and vegetation change in Pond Inlet had consistently increased throughout each time period. The area of glacial loss grew through each period to a maximum of 376 km2 of glacial loss in the last decade. Similarly, the area of the Arctic tundra that experienced vegetation change increased in each time period to a maximum of 660 km2 in the last decade. This vegetation change was characterized by overall increasing values of NDVI, revealing that many sections of the Arctic tundra in Pond Inlet were increasing in biomass. However, case study analysis revealed pixel clustering around the lower vegetation class thresholds used to classify change, indicating that shifts between these vegetation classes were likely exaggerated. Shifts between the higher vegetation classes were significant, and were what contributed to the most change in the last decade. The observations of higher glacial melt and increases in biomass are occurring in parallel with the increasing temperatures in Pond Inlet. Relevant literature in the Arctic agrees with the findings of this MRP that there are significant trends of glacial loss and vegetation greening and many studies attribute this directly to climate warming. The results of this study provide the necessary background with regards to landscape changes which could be used in future field studies investigating the climate induced changes in Pond Inlet. This study also demonstrates that significant landscape modifications have occurred in the recent decades and there is a strong need for continued research and monitoring of climate induced changes.

Download Full-text

Patterns of Arctic Tundra Greenness Based on Spatially Downscaled Solar-Induced Fluorescence

Remote Sensing ◽

10.3390/rs11121460 ◽

2019 ◽

Vol 11 (12) ◽

pp. 1460 ◽

Cited By ~ 1

Author(s):

Dongjie Fu ◽

Fenzhen Su ◽

Juan Wang ◽

Yijie Sui

Keyword(s):

Satellite Remote Sensing ◽

Vegetation Index ◽

Normalized Difference Vegetation Index ◽

Gross Primary Production ◽

Remote Sensing Data ◽

Arctic Region ◽

Arctic Tundra ◽

The Arctic ◽

Global Inventory ◽

The Arctic Region

A general greening trend in the Arctic tundra biome has been indicated by satellite remote sensing data over recent decades. However, since 2011, there have been signs of browning trends in many parts of the region. Previous research on tundra greenness across the Arctic region has relied on the satellite-derived normalized difference vegetation index (NDVI). In this research, we initially used spatially downscaled solar-induced fluorescence (SIF) data to analyze the spatiotemporal variation of Arctic tundra greenness (2007–2013). The results derived from the SIF data were also compared with those from two NDVIs (the Global Inventory Modeling and Mapping Studies NDVI3g and MOD13Q1 NDVI), and the eddy-covariance (EC) observed gross primary production (GPP). It was found that most parts of the Arctic tundra below 75° N were browning (–0.0098 mW/m2/sr/nm/year, where sr is steradian and nm is nanometer) using SIF, whereas spatially and temporally heterogeneous trends (greening or browning) were obtained based on the two NDVI products. This research has further demonstrated that SIF data can provide an alternative direct proxy for Arctic tundra greenness.

Download Full-text

The relative importance of environmental factors on the interannual variability of carbon fluxes in the boreal forest

10.5194/egusphere-egu2020-12470 ◽

2020 ◽

Author(s):

Mariam El-Amine ◽

Alexandre Roy ◽

Pierre Legendre ◽

Oliver Sonnentag

Keyword(s):

Environmental Factors ◽

Boreal Forest ◽

Vegetation Index ◽

Normalized Difference Vegetation Index ◽

Carbon Sink ◽

Growing Season ◽

Carbon Uptake ◽

Net Ecosystem Productivity ◽

Ecosystem Productivity ◽

Environmental Controls

<p>As climate change will cause a more pronounced rise of air temperature in northern high latitudes than in other parts of the world, it is expected that the strength of the boreal forest carbon sink will be altered. To better understand and quantify these changes, we studied the influence of different environmental controls (e.g., air and soil temperatures, soil water content, photosynthetically active radiation, normalized difference vegetation index) on the timing of the start and end of the boreal forest growing season and the net carbon uptake period in Canada. The influence of these factors on the growing season carbon exchanges between the atmosphere and the boreal forest were also evaluated. There is a need to improve the understanding of the role of the length of the growing season and the net carbon uptake period on the strength of the boreal forest carbon sink, as an extension of these periods might not necessarily result in a stronger carbon sink if other environmental factors are not optimal for carbon sequestration or enhance respiration.</p><p>Here, we used 31 site-years of observation over three Canadian boreal forest stands: Eastern, Northern and Southern Old Black Spruce in Qu&#233;bec, Manitoba and Saskatchewan, respectively. Redundancy analyses were used to highlight the environmental controls that correlate the most with the annual net ecosystem productivity and the start and end of the growing season and the net carbon uptake period. Preliminary results show that the timing at which the air temperature becomes positive correlates the most strongly with the start of the net carbon uptake period (r = 0.70, p < 0.001) and the start of the growing season (r = 0.55, p < 0.01). Although the increase of the normalized difference vegetation index also correlates with the start of these periods, a thorough examination of this result shows that the latter happens well before the former. No dependency between any environmental control and the end of the net carbon uptake period was identified. Also, the annual net ecosystem productivity is highly correlated with the length of the net carbon uptake period (r = 0.54, p < 0.01). Other environmental controls such as annual precipitations, the mean annual soil temperature or the maximum yearly normalized difference vegetation index have a smaller impact on the annual net ecosystem productivity. By extending the dataset to include forest stands that represent a wider climate and permafrost variability, we will examine the generalizability of these results.</p>

Download Full-text

Disturbance Mapping in Arctic Tundra Improved by a Planning Workflow for Drone Studies: Advancing Tools for Future Ecosystem Monitoring

Remote Sensing ◽

10.3390/rs13214466 ◽

2021 ◽

Vol 13 (21) ◽

pp. 4466

Author(s):

Isabell Eischeid ◽

Eeva M. Soininen ◽

Jakob J. Assmann ◽

Rolf A. Ims ◽

Jesper Madsen ◽

...

Keyword(s):

Vegetation Index ◽

Normalized Difference Vegetation Index ◽

Predictive Ability ◽

Ground Cover ◽

Arctic Tundra ◽

The Arctic ◽

Ecosystem Monitoring ◽

Selection Of Variables ◽

State Changes ◽

Study Sites

The Arctic is under great pressure due to climate change. Drones are increasingly used as a tool in ecology and may be especially valuable in rapidly changing and remote landscapes, as can be found in the Arctic. For effective applications of drones, decisions of both ecological and technical character are needed. Here, we provide our method planning workflow for generating ground-cover maps with drones for ecological monitoring purposes. The workflow includes the selection of variables, layer resolutions, ground-cover classes and the development and validation of models. We implemented this workflow in a case study of the Arctic tundra to develop vegetation maps, including disturbed vegetation, at three study sites in Svalbard. For each site, we generated a high-resolution map of tundra vegetation using supervised random forest (RF) classifiers based on four spectral bands, the normalized difference vegetation index (NDVI) and three types of terrain variables—all derived from drone imagery. Our classifiers distinguished up to 15 different ground-cover classes, including two classes that identify vegetation state changes due to disturbance caused by herbivory (i.e., goose grubbing) and winter damage (i.e., ‘rain-on-snow’ and thaw-freeze). Areas classified as goose grubbing or winter damage had lower NDVI values than their undisturbed counterparts. The predictive ability of site-specific RF models was good (macro-F1 scores between 83% and 85%), but the area of the grubbing class was overestimated in parts of the moss tundra. A direct transfer of the models between study sites was not possible (macro-F1 scores under 50%). We show that drone image analysis can be an asset for studying future vegetation state changes on local scales in Arctic tundra ecosystems and encourage ecologists to use our tailored workflow to integrate drone mapping into long-term monitoring programs.

Download Full-text

Fire-induced changes in soil and vegetation in the forest-tundra of Western Siberia

E3S Web of Conferences ◽

10.1051/e3sconf/202022303001 ◽

2020 ◽

Vol 223 ◽

pp. 03001

Author(s):

Oleg Sizov ◽

Leya Brodt ◽

Andrey Soromotin ◽

Nikolay Prikhodko ◽

Ramona Heim

Keyword(s):

Vegetation Index ◽

Normalized Difference Vegetation Index ◽

Western Siberia ◽

The Arctic ◽

Fire Scars ◽

Forest Tundra ◽

The North ◽

Tundra Vegetation ◽

Lichen Cover ◽

The Face

Wildfires are one of the main factors for landscape change in tundra ecosystems. In the absence of external mechanical impacts, tundra plant communities are relatively stable, even in the face of climatic changes. In our study, lichen cover was degraded on burnt tundra sites, which increased the permafrost thaw depth from 100 to 190 cm. In old fire scars (burnt 1980 – 1990) of the forest-tundra, vegetation cover was dominated by trees and shrubs. The soil temperature on burnt forest-tundra sites was higher in comparison to conditions of the unburnt control sites and permafrost was was not found at a depth of 2-2,3m. Dynamics of the Normalized Difference Vegetation index (NDVI) from 1986-2020 reveal that immediately after fires, vegetation recovered and biomass increased due to the development of Betula nana shrubs. In old fire scars of the forest-tundra (burnt 1980-1990), a significant increase in NDVI values was evident, in contrast to the unburnt tundra vegetation where this trend was less pronounced. We conclude that "greening" in the north of Western Siberia may occur due to fire-induced transformation processes. The role of wildfires in the advance of the treeline to the north, driven by climate change and active economic development of the Arctic, will gradually increase in future.

Download Full-text

Vegetation phenology in Greenland and links to cryospheric change

Annals of Glaciology ◽

10.1017/aog.2018.24 ◽

2018 ◽

Vol 59 (77) ◽

pp. 59-68 ◽

Cited By ~ 2

Author(s):

Jeffery A. Thompson ◽

Lora S. Koenig

Keyword(s):

Vegetation Index ◽

Normalized Difference Vegetation Index ◽

Greenland Ice Sheet ◽

The Arctic ◽

Growing Degree Days ◽

Degree Days ◽

Hydrologic Change ◽

Moderate Resolution Imaging Spectroradiometer ◽

Cryospheric Change ◽

Dry Out

ABSTRACTRecent greening of vegetation across the Arctic is associated with warming temperatures, hydrologic change and shorter snow-covered periods. Here we investigated trends for a subset of arctic vegetation on the island of Greenland. Vegetation in Greenland is unique due to its close proximity to the Greenland Ice Sheet and its proportionally large connection to the Greenlandic population through the hunting of grazing animals. The aim of this study was to determine whether or not longer snow-free periods (SFPs) were causing Greenlandic vegetation to dry out and become less productive. If vegetation was drying out, a subsequent aim of the study was to determine how widespread the drying was across Greenland. We utilized a 15-year time-series obtained by the MODerate Resolution Imaging Spectroradiometer (MODIS) to analyze the Greenland vegetation by deriving descriptors corresponding with the SFP, the number of cumulative growing degree-days and the time-integrated Normalized Difference Vegetation Index. While the productivity of most vegetated areas increased in response to longer growing periods, there were localized regions that exhibited signs consistent with the drying hypothesis. In these areas, vegetation productivity decreased in response to longer SFPs and more accumulated growing degree-days.

Download Full-text