Samstag, 27. Dezember 2014

Global greening due to CO2

From Poster Jimbo on 

Abstract – 28 June 2013
Randall J. Donohue et al
Impact of CO2 fertilization on maximum foliage cover across the globe’s warm, arid environments
Satellite observations reveal a greening of the globe over recent decades. The role in this greening of the “CO2 fertilization” effect—the enhancement of photosynthesis due to rising CO2 levels—is yet to be established. The direct CO2 effect on vegetation should be most clearly expressed in warm, arid environments where water is the dominant limit to vegetation growth. Using gas exchange theory, we predict that the 14% increase in atmospheric CO2 (1982–2010) led to a 5 to 10% increase in green foliage cover in warm, arid environments. Satellite observations, analyzed to remove the effect of variations in precipitation, show that cover across these environments has increased by 11%. Our results confirm that the anticipated CO2 fertilization effect is occurring alongside ongoing anthropogenic perturbations to the carbon cycle and that the fertilization effect is now a significant land surface process.
Geophysical Research Letters – Volume 40, Issue 12, pages 3031–3035
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Abstract – May 2013
A Global Assessment of Long-Term Greening and Browning Trends in Pasture Lands Using the GIMMS LAI3g Dataset
Our results suggest that degradation of pasture lands is not a globally widespread phenomenon and, consistent with much of the terrestrial biosphere, there have been widespread increases in pasture productivity over the last 30 years.
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Abstract – 10 April 2013
Analysis of trends in fused AVHRR and MODIS NDVI data for 1982–2006: Indication for a CO2 fertilization effect in global vegetation
…..The effect of climate variations and CO2 fertilization on the land CO2 sink, as manifested in the RVI, is explored with the Carnegie Ames Stanford Assimilation (CASA) model. Climate (temperature and precipitation) and CO2 fertilization each explain approximately 40% of the observed global trend in NDVI for 1982–2006……
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Abstract – May 2013
The causes, effects and challenges of Sahelian droughts: a critical review
…….However, this study hypothesizes that the increase in CO2 might be responsible for the increase in greening and rainfall observed. This can be explained by an increased aerial fertilization effect of CO2 that triggers plant productivity and water management efficiency through reduced transpiration. Also, the increase greening can be attributed to rural–urban migration which reduces the pressure of the population on the land…….
doi: 10.1007/s10113-013-0473-z
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Abstract – 19 March 2014
Martin Brandt et al
Local Vegetation Trends in the Sahel of Mali and Senegal Using Long Time Series FAPAR Satellite Products and Field Measurement (1982–2010)
…..Significant greening trends from 1982 to 2010 are consistently observed in both GEOV1 and GIMMS3g FAPAR datasets. Annual rainfall increased significantly during the observed time period, explaining large parts of FAPAR variations at a regional scale. Locally, GEOV1 data reveals a heterogeneous pattern of vegetation change, which is confirmed by long-term ground data and site visits……
Remote Sensing 6, pp. 2408-2434
DOI:10.3390/rs6032408
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Abstract – 2014
Forest stand growth dynamics in Central Europe have accelerated since 1870,
Forest ecosystems have been exposed to climate change for more than 100 years, whereas the consequences on forest growth remain elusive. Based on the oldest existing experimental forest plots in Central Europe, we show that, currently, the dominant tree species Norway spruce and European beech exhibit significantly faster tree growth (+32 to 77%), stand volume growth (+10 to 30%) and standing stock accumulation (+6 to 7%) than in 1960. Stands still follow similar general allometric rules, but proceed more rapidly through usual trajectories. As forest stands develop faster, tree numbers are currently 17–20% lower than in past same-aged stands. Self-thinning lines remain constant, while growth rates increase indicating the stock of resources have not changed, while growth velocity and turnover have altered. Statistical analyses of the experimental plots, and application of an ecophysiological model, suggest that mainly the rise in temperature and extended growing seasons contribute to increased growth acceleration, particularly on fertile sites.
Nat. Commun. 5:4967, DOI:10.1038/ncomms5967

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