Search Results - (Author, Cooperation:I. A. Janssens)

2018-01-25

Wiley-Blackwell

1354-1013

1365-2486

Biology

Energy, Environment Protection, Nuclear Power Engineering

Geography

2013-09-06

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Carbon/metabolism ; Carbon Cycle ; Carbon Dioxide/metabolism ; Cell Respiration ; Circadian Rhythm ; *Darkness ; Ecosystem ; *Geography ; *Global Warming ; Photosynthesis/radiation effects ; Plants/*metabolism/radiation effects ; Sunlight ; Temperature

2011-10-08

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Bioengineering ; Carbon/*metabolism ; *Carbon Cycle ; Charcoal/metabolism ; Climate Change ; *Ecosystem ; Freezing ; Organic Chemicals/*analysis/metabolism ; Plant Roots/metabolism ; Plants/metabolism ; Soil/*chemistry ; Soil Microbiology

2015-09-30

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Cold Temperature ; Europe ; *Global Warming ; Models, Biological ; Photoperiod ; Plant Leaves/*growth & development ; *Seasons ; Time Factors ; Trees/*growth & development

1365-2486

Blackwell Publishing Journal Backfiles 1879-2005

Biology

Energy, Environment Protection, Nuclear Power Engineering

Geography

This paper presents CO2 flux data from 18 forest ecosystems, studied in the European Union funded EUROFLUX project. Overall, mean annual gross primary productivity (GPP, the total amount of carbon (C) fixed during photosynthesis) of these forests was 1380 ± 330 gC m−2 y−1 (mean ±SD). On average, 80% of GPP was respired by autotrophs and heterotrophs and released back into the atmosphere (total ecosystem respiration, TER = 1100 ± 260 gC m−2 y−1). Mean annual soil respiration (SR) was 760 ± 340 gC m−2 y−1 (55% of GPP and 69% of TER).Among the investigated forests, large differences were observed in annual SR and TER that were not correlated with mean annual temperature. However, a significant correlation was observed between annual SR and TER and GPP among the relatively undisturbed forests. On the assumption that (i) root respiration is constrained by the allocation of photosynthates to the roots, which is coupled to productivity, and that (ii) the largest fraction of heterotrophic soil respiration originates from decomposition of young organic matter (leaves, fine roots), whose availability also depends on primary productivity, it is hypothesized that differences in SR among forests are likely to depend more on productivity than on temperature.At sites where soil disturbance has occurred (e.g. ploughing, drainage), soil espiration was a larger component of the ecosystem C budget and deviated fromthe relationship between annual SR (and TER) and GPP observed among the less-disturbed forests. At one particular forest, carbon losses from the soil were so large, that in some years the site became a net source of carbon to the atmosphere. Excluding the disturbed sites from the present analysis reduced mean SR to 660 ± 290 gC m−2 y−1, representing 49% of GPP and 63% of TER in the relatively undisturbed forest ecosystems.

Electronic Resource

1365-2486

Blackwell Publishing Journal Backfiles 1879-2005

Biology

Energy, Environment Protection, Nuclear Power Engineering

Geography

The temperature sensitivity of soil respiration (SR) is often estimated from the seasonal changes in the flux relative to those in soil temperature, and subsequently used in models to interpolate or predict soil fluxes. However, temperature sensitivities derived from seasonal changes in SR (from here on denoted seasonal Q10) may not solely reflect the temperature sensitivity of SR, because seasonal changes in SR can also be affected by other seasonally fluctuating conditions and processes. In this manuscript, we present a case study of how the seasonal Q10 of SR can be decoupled from the temperature sensitivity of SR. In a mixed temperate forest, we measured SR under vegetations with different leaf strategies: pure evergreen, pure deciduous, and mixed. Seasonal Q10 was much higher under deciduous than under evergreen canopies. However, at a shorter time scale, both vegetation types exhibited very similar Q10 values, indicating that the large differences in seasonal Q10 do not represent differences in the temperature sensitivity of the soil metabolism. The seasonal Q10 depends strongly on the amplitude of the seasonal changes in SR (SRs), which, under the particular climatic and edaphic conditions of our forest study site, were significantly larger in deciduous forest. In turn, SRs was positively correlated with the seasonal changes in leaf area index (LAIs), a measure of the deciduousness of the vegetation. Thus, in this temperate maritime forest, seasonal Q10 of SR was strongly influenced by the deciduousness of the vegetation. We conclude that the large differences in seasonal Q10 were not entirely due to different temperature sensitivities, but also to different seasonal patterns of plant activity in the evergreen and deciduous plants of this site. Some coniferous forests may be more seasonal than the one we studied, and the deciduous–evergreen differences observed here may not be broadly applicable, but this case study demonstrates that variation of plant phenological process can significantly contribute to the seasonality of SR, and, hence, calculated Q10 values. Where this occurs, the seasonal Q10 value for SR does not accurately represent temperature sensitivity. Because the strong seasonal correlation between SR and temperature does not necessarily imply a causal relationship, Q10 values derived form annual patterns of SR should be used with caution when predicting future responses of SR to climatic change.

Electronic Resource