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- Thomas, HS, et al.
(författare)
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- 2019
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swepub:Mat__t
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- Magnani, F, et al.
(författare)
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The human footprint in the carbon cycle of temperate and boreal forests
- 2007
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Ingår i: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885. ; 447, s. 848-850
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Tidskriftsartikel (refereegranskat)abstract
- Temperate and boreal forests in the Northern Hemisphere cover an area of about 2 times 107 square kilometres and act as a substantial carbon sink (0.6–0.7 petagrams of carbon per year)1. Although forest expansion following agricultural abandonment is certainly responsible for an important fraction of this carbon sink activity, the additional effects on the carbon balance of established forests of increased atmospheric carbon dioxide, increasing temperatures, changes in management practices and nitrogen deposition are difficult to disentangle, despite an extensive network of measurement stations2, 3. The relevance of this measurement effort has also been questioned4, because spot measurements fail to take into account the role of disturbances, either natural (fire, pests, windstorms) or anthropogenic (forest harvesting). Here we show that the temporal dynamics following stand-replacing disturbances do indeed account for a very large fraction of the overall variability in forest carbon sequestration. After the confounding effects of disturbance have been factored out, however, forest net carbon sequestration is found to be overwhelmingly driven by nitrogen deposition, largely the result of anthropogenic activities5. The effect is always positive over the range of nitrogen deposition covered by currently available data sets, casting doubts on the risk of widespread ecosystem nitrogen saturation6 under natural conditions. The results demonstrate that mankind is ultimately controlling the carbon balance of temperate and boreal forests, either directly (through forest management) or indirectly (through nitrogen deposition).
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- Pendall, E, et al.
(författare)
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Below-ground process responses to elevated CO2 and temperature: a discussion of observations, measurement methods, and models
- 2004
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Ingår i: New Phytologist. - : Wiley. - 1469-8137 .- 0028-646X. ; 162:2, s. 311-322
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Forskningsöversikt (refereegranskat)abstract
- Rising atmospheric CO2 and temperatures are probably altering ecosystem carbon cycling, causing both positive and negative feedbacks to climate. Below-ground processes play a key role in the global carbon (C) cycle because they regulate storage of large quantities of C, and are potentially very sensitive to direct and indirect effects of elevated CO2 and temperature. Soil organic matter pools, roots and associated rhizosphere organisms all have distinct responses to environmental change drivers, although availability of C substrates will regulate all the responses. Elevated CO2 increases C supply below-ground, whereas warming is likely to increase respiration and decomposition rates, leading to speculation that these effects will moderate one another. However, indirect effects on soil moisture availability and nutrient supply may alter processes in unexpected directions. Detailed, mechanistic understanding and modelling of below-ground flux components, pool sizes and turnover rates is needed to adequately predict long-term, net C storage in ecosystems. In this synthesis, we discuss the current status of below-ground responses to elevated CO2 and temperature and potential feedback effects, methodological challenges, and approaches to integrating models and measurements.
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