Remote sensing of tundra gross ecosystem productivity and light use efficiency under varying temperature and moisture conditions

Huemmrich, K. F.; Gamon, John A.; Tweedie, C. E.; Oberbauer, Steven F.; Kinoshita, G.; Houston, S.; Kuchy, Andrea; Hollister, Robert D.; Kwon, Hyo Jung; Mano, Masayoshi

doi:10.1016/j.rse.2009.10.003

Cited by 80 publications

(87 citation statements)

References 47 publications

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“…Since vegetation covers the surface completely in the studied plots, with a moss layer closest to the ground, we assumed that all of the PPFD in that was not reflected by the surface was absorbed by vegetation (Frolking et al 1998;Huemmrich et al 2010a). For each plot we calculated fAPAR separately in 1-h intervals throughout the whole growing season.…”

Section: Data Processing and Statistical Analysismentioning

confidence: 99%

Increased photosynthesis compensates for shorter growing season in subarctic tundra—8 years of snow accumulation manipulations

et al. 2014

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This study was initiated to analyze the effect of increased snow cover on plant photosynthesis in subarctic mires underlain by permafrost. Snow fences were used to increase the accumulation of snow on a subarctic permafrost mire in northern Sweden. By measuring reflected photosynthetic active radiation (PAR) the effect of snow thickness and associated delay of the start of the growing season was assessed in terms of absorbed PAR and estimated gross primary production (GPP). Six plots experienced increased snow accumulation and six plots were untreated. Incoming and reflected PAR was logged hourly from August 2010 to October 2013. In 2010 PAR measurements were coupled with flux chamber measurements to assess GPP and light use efficiency of the plots. The increased snow thickness prolonged the duration of the snow cover in spring. The delay of the growing season start in the treated plots was 18 days in 2011, 3 days in 2012 and 22 days in 2013. Results show higher PAR absorption, together with almost 35 % higher light use efficiency, in treated plots compared to untreated plots. Estimations of GPP suggest that the loss in early season photosynthesis, due to the shortening of the growing season in the treatment plots, is well compensated for by the increased absorption of PAR and higher light use efficiency throughout the whole growing seasons. This compensation is likely to be explained by increased soil moisture and nutrients together with a shift in vegetation composition associated with the accelerated permafrost thaw in the treatment plots.

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Section: Data Processing and Statistical Analysismentioning

confidence: 99%

Increased photosynthesis compensates for shorter growing season in subarctic tundra—8 years of snow accumulation manipulations

et al. 2014

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“…As such, changes in vegetation composition and productivity are predicted to occur due to a lengthening of the growing season [4][5][6], increases in air and soil temperature and active layer depth [7,8], increased shrub cover [9,10], and acceleration of below ground microbial activity and nutrient cycling [3,11,12]. These changes influence the terrestrial carbon cycle and thus alter the relationship between arctic ecosystems and global climate.…”

Section: Introductionmentioning

confidence: 99%

“…For example, an increasing growing season length can enhance carbon uptake through photosynthesis and thereby reduce atmospheric carbon dioxide (CO 2 ) concentrations [13]. Conversely, increasing temperatures may heighten methane (CH 4 ) and CO 2 release from thawing permafrost, enhancing plant-mediated transport of CH 4 [14,15] and contributing to rising levels of greenhouse gases in the atmosphere.…”

Section: Introductionmentioning

confidence: 99%

Mapping Arctic Tundra Vegetation Communities Using Field Spectroscopy and Multispectral Satellite Data in North Alaska, USA

et al. 2016

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Abstract:The Arctic is currently undergoing intense changes in climate; vegetation composition and productivity are expected to respond to such changes. To understand the impacts of climate change on the function of Arctic tundra ecosystems within the global carbon cycle, it is crucial to improve the understanding of vegetation distribution and heterogeneity at multiple scales. Information detailing the fine-scale spatial distribution of tundra communities provided by high resolution vegetation mapping, is needed to understand the relative contributions of and relationships between single vegetation community measurements of greenhouse gas fluxes (e.g.,~1 m chamber flux) and those encompassing multiple vegetation communities (e.g.,~300 m eddy covariance measurements). The objectives of this study were: (1) to determine whether dominant Arctic tundra vegetation communities found in different locations are spectrally distinct and distinguishable using field spectroscopy methods; and (2) to test which combination of raw reflectance and vegetation indices retrieved from field and satellite data resulted in accurate vegetation maps and whether these were transferable across locations to develop a systematic method to map dominant vegetation communities within larger eddy covariance tower footprints distributed along a 300 km transect in northern Alaska. We showed vegetation community separability primarily in the 450-510 nm, 630-690 nm and 705-745 nm regions of the spectrum with the field spectroscopy data. This is line with the different traits of these arctic tundra communities, with the drier, often non-vascular plant dominated communities having much higher reflectance in the 450-510 nm and 630-690 nm regions due to the lack of photosynthetic material, whereas the low reflectance values of the vascular plant dominated communities highlight the strong light absorption found here. High classification accuracies of 92% to 96% were achieved using linear discriminant analysis with raw and rescaled spectroscopy reflectance data and derived vegetation indices. However, lower classification accuracies (~70%) resulted when using the coarser 2.0 m WorldView-2 data inputs. The results from this study suggest that tundra vegetation communities are separable using plot-level spectroscopy with hand-held sensors. These results also show that tundra vegetation mapping can be scaled from the plot level (<1 m) to patch level (<500 m) using spectroscopy data rescaled to match the wavebands of the multispectral satellite remote sensing. We find that developing a consistent method for classification of vegetation communities across the flux tower sites is a challenging process, given the spatial variability in vegetation communities and the need for detailed vegetation survey data for training and validating classification algorithms. This study highlights the benefits of using fine-scale field spectroscopy measurements to obtain tundra vegetation classifications for landscape analyses and use in carbon flux scaling studies. Improved...

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“…A previous study showed that the net CO 2 uptake rates of mosses were only about 10-40% those of vascular plants on a dry mass basis 41 . Similarly, the LUE of moss in Alaskan tundra was about 18% that of the overstory canopy 42 . Apparently, more comparative studies on photosynthetic capacity and LUE of mosses and vascular plants are needed to further improve our understanding of the role of mosses in regional and global carbon cycles.…”

Section: Resultsmentioning

confidence: 92%

“…In this study, e vmax is set at 2.14 g C m À 2 MJ À 1 APAR 12,50 , and e mmax is assumed to be 30% of e vmax or 0.64 g C m À 2 MJ À 1 APAR based on previous studies 14,41,42 . K_NDVI indicates the proportional contribution of moss to the NDVI signal; PAR v and PAR m are the total photosynthetically active radiation partitioned to the vascular and moss plants, respectively.…”

Section: Methodsmentioning

confidence: 99%

Differentiating moss from higher plants is critical in studying the carbon cycle of the boreal biome

et al. 2014

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The satellite-derived normalized difference vegetation index (NDVI), which is used for estimating gross primary production (GPP), often includes contributions from both mosses and vascular plants in boreal ecosystems. For the same NDVI, moss can generate only about onethird of the GPP that vascular plants can because of its much lower photosynthetic capacity. Here, based on eddy covariance measurements, we show that the difference in photosynthetic capacity between these two plant functional types has never been explicitly included when estimating regional GPP in the boreal region, resulting in a substantial overestimation. The magnitude of this overestimation could have important implications regarding a change from a current carbon sink to a carbon source in the boreal region. Moss abundance, associated with ecosystem disturbances, needs to be mapped and incorporated into GPP estimates in order to adequately assess the role of the boreal region in the global carbon cycle.

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Remote sensing of tundra gross ecosystem productivity and light use efficiency under varying temperature and moisture conditions

Cited by 80 publications

References 47 publications

Increased photosynthesis compensates for shorter growing season in subarctic tundra—8 years of snow accumulation manipulations

Increased photosynthesis compensates for shorter growing season in subarctic tundra—8 years of snow accumulation manipulations

Mapping Arctic Tundra Vegetation Communities Using Field Spectroscopy and Multispectral Satellite Data in North Alaska, USA

Differentiating moss from higher plants is critical in studying the carbon cycle of the boreal biome

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