53 research outputs found
Spectral Callibration of High Arctic Primary Production Estimation (SCHAPPE).<em> </em>:<em>In</em>: Rasch, M. and Caning, K. (eds.). Zackenberg Ecological Research Operations, 10th Annual Report, 2004. - Copenhagen, Danish Polar Center, Ministry of Science, Technology and Innovation
Ecosystem-atmosphere interactions in the Arctic: using data-model approaches to understand carbon cycle feedbacks
The terrestrial CO2 exchange in the Arctic plays an important role in the global carbon (C) cycle. The
Arctic ecosystems, containing a large amount of organic carbon (C), are experiencing ongoing warming in
recent decades, which is affecting the C cycling and the feedback interactions between its different
components. To improve our understanding of the atmosphere-ecosystem interactions, the Greenland
Ecosystem Monitoring (GEM) program measures ecosystem CO2 exchange and links it to biogeochemical
processes. However, this task remains challenging in northern latitudes due to an insufficient number of
measurement sites, particularly covering full annual cycles, but also the frequent gaps in data affected by
extreme conditions and remoteness. Combining ecosystem models and field observations we are able to study
the underlying processes of Arctic CO2 exchange in changing environments. The overall aim of the research is
to use data-model approaches to analyse the patterns of C exchange and their links to biological processes in
Arctic ecosystems, studied in detail both from a measurement and a modelling perspective, but also from a
local to a pan-arctic scale.
In Paper I we found a compensatory response of photosynthesis (GPP) and ecosystem respiration (Reco),
both highly sensitive to the meteorological drivers (i.e. temperatures and radiation) in Kobbefjord, West
Greenland tundra. This tight relationship led to a relatively insensitive net ecosystem exchange (NEE) to the
meteorology, despite the large variability in temperature and precipitations across growing seasons. This tundra
ecosystem acted as a consistent sink of C (-30 g C m-2), except in 2011 (41 g C m-2), which was associated with
a major pest outbreak. In Paper II we estimated this decrease of C sink strength of 118-144 g C m-2 in the
anomalous year (2011), corresponding to 1210-1470 tonnes C at the Kobbefjord catchment scale. We
concluded that the meteorological sensitivity of photosynthesis and respiration were similar, and hence
compensatory, but we could not explain the causes. Therefore, in Paper III we used a calibrated and validated
version of the Soil-Plant-Atmosphere model to explore full annual C cycles and detail the coupling between
GPP and Reco. From this study we found two key results. First, similar metrological buffering to growing season
reduced the full annual C sink strength by 60%. Second, plant traits control the compensatory effect observed
(and estimated) between gross primary production and ecosystem respiration. Because a site-specific location
is not representative of the entire Arctic, we further evaluated the pan-Arctic terrestrial C cycling using the
CARDAMOM data assimilation system in Paper IV. Our estimates of C fluxes, pools and transit times are in
good agreement with different sources of assimilated and independent data, both at pan-Arctic and local scale.
Our benchmarking analysis with extensively used Global Vegetation Models (GVM) highlights that GVM
modellers need to focus on the vegetation C dynamics, but also the respiratory losses, to improve our
understanding of internal C cycle dynamics in the Arctic.
Data-model approaches generate novel outputs, allowing us to explore C cycling mechanisms and
controls that otherwise would not have been possible to address individually. Also, discrepancies between data
and models can provide information about knowledge gaps and ecological indicators not previously detected
from field observations, emphasizing the unique synergy that models and data are capable of bringing together
The Arctic plant aboveground biomass synthesis dataset
Abstract
Plant biomass is a fundamental ecosystem attribute that is sensitive to rapid climatic changes occurring in the Arctic. Nevertheless, measuring plant biomass in the Arctic is logistically challenging and resource intensive. Lack of accessible field data hinders efforts to understand the amount, composition, distribution, and changes in plant biomass in these northern ecosystems. Here, we present The Arctic plant aboveground biomass synthesis dataset, which includes field measurements of lichen, bryophyte, herb, shrub, and/or tree aboveground biomass (g m−2) on 2,327 sample plots from 636 field sites in seven countries. We created the synthesis dataset by assembling and harmonizing 32 individual datasets. Aboveground biomass was primarily quantified by harvesting sample plots during mid- to late-summer, though tree and often tall shrub biomass were quantified using surveys and allometric models. Each biomass measurement is associated with metadata including sample date, location, method, data source, and other information. This unique dataset can be leveraged to monitor, map, and model plant biomass across the rapidly warming Arctic
Transitions in high-Arctic vegetation growth patterns and ecosystem productivity tracked with automated cameras from 2000 to 2013
Growth season dynamics of methane emission from arctic tundra:a comparison of chamber measurements over ten years
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