Search

The predicted increase in frequency and intensity of boreal forest fires is considered a significant source of carbon dioxide emissions and linked with the degradation of permafrost covering more than half of Russia. Here we analyzed the stand structure and growth of East Siberian larch forests in response to fire severity. We measured 23 sites in the southern part of eastern Siberia along a latitudinal transect with a length of more than 1500 km. Live tree volume differed significantly across geographical regions (p < 0.05), decreasing from south to north (76-250 [m.sup.3]*[ha.sup.-1]), with higher values in forests burnt with low severity. Similarly, volume of coarse woody debris decreased from south to north. The volume of dead standing trees, on the other hand, increased from south to north. The distribution of trees by diameter class in some areas showed clear evidence of fires, with small trees being absent to rare in forests burnt at high severity. The impact of severe fires on stand volume was negligible at the southern sites, potentially associated with rapid regeneration of birch. Birch is an important component of larch forests near the southern boundary of the permafrost, which may contribute to larch forests in the southern part of the study transect being less vulnerable to wildfires compared to northern larch forests. Key words: Larix gmelinii, wildfire, mortality, carbon emissions, coarse woody debris, permafrost, Yakutia, Pinus sylvestris, Pinus pumila, Picea obovata, Betula platyphylla L'augmentation prevue de la frequence et de l'intensite des incendies de foret boreale est consideree comme une source importante d'emissions de dioxyde de carbone et est liee a la degradation du pergelisol couvrant plus de la moitie de la Russie. Nous avons analyse ici la structure et la croissance des peuplements de melezes de Siberie orientale en fonction de la gravite des incendies. Nous avons mesure 23 sites dans la partie sud de la Siberie orientale le long d'un transect latitudinal de plus de 1500 km de long. Le volume des arbres vivants differait significativement entre les regions geographiques (p < 0,05), diminuant du sud au nord (76-250 [m.sup.3]*[ha.sup.-1]), avec des valeurs plus elevees dans les forets brulees avec une faible severite. De meme, le volume des debris ligneux grossiers a diminue du sud au nord. Le volume des arbres morts sur pied, en revanche, a augmente du sud au nord. La distribution des arbres par classe de diametre dans certaines zones a montre des signes evidents d'incendies, les petits arbres etant absents ou rares dans les forets brulees avec une severite elevee. L'impact des incendies graves sur le volume des peuplements etait negligeable sur les sites du sud, ce qui pourrait etre associe a une regeneration rapide du bouleau. Le bouleau est une composante importante des forets de melezes pres de la limite sud du pergelisol, ce qui pourrait contribuer a rendre les forets de melezes de la partie sud du transect etudie moins vulnerables aux incendies que les forets de melezes du nord. [Traduit par la Redaction] Mots-cles : Larix gmelinii, feu de foret, mortalite, emissions de carbone, debris ligneux grossiers, pergelisol, Yakoutie, Pinus sylvestris, Pinus pumila, Picea obovata, Betula platyphylla, Introduction In the 21st century, the crucial role of forest ecosystems in maintaining and regulating the processes and structures of the biosphere has been recognized at the level of policy [...]

Predicting photosynthetic acclimation to elevated C[O.sub.2] and warming is difficult because they have opposite effects. We investigated physiological and morphological responses in white birch (Betula papyrifera Marshall) to a combination of C[O.sub.2] and temperature (ACT--400 [micro]mol*[mol.sup.-1] C[O.sub.2], current temperature; ECT--750 [micro]mol*[mol.sup.-1] C[O.sub.2], current + 4[degrees]C temperature). ECT reduced photosynthesis, maximum Rubisco carboxylation ([V.sub.cmax]), maximum electron transport rate ([J.sub.max]), photorespiration, daytime respiration, leaf N, and stomatal and mesophyll conductance, but increased biomass, height, total leaf area, electron partitioning to carboxylation and oxygenation ratio, and C[O.sub.2] compensation point. The photosynthetic acclimation is consistent with the optimal carbon gain theory (carbon gain drives the coordination of carboxylation, electron transport, and respiration). While the photosynthetic acclimation was similar to acclimation to elevated C[O.sub.2], ECT reduced [J.sub.max]/[V.sub.cmax], which is consistent with the response to warming but opposite to the response to elevated C[O.sub.2], suggesting that thermal acclimation may be the primary mechanism of photosynthetic acclimation to ECT and ECT probably altered N allocation between machinery for carboxylation and that for ribulose-1,5-bisphosphate regeneration. The increase in total leaf area by ECT more than offset the negative effect of photosynthetic downregulation on carbon sequestration, resulting in faster growth and greater biomass under ECT. Key words: white birch (Betula papyrifera Marshall), elevated C[O.sub.2], photosynthetic acclimation, electron transport, leaf area, carbon gain Il est difficile de predire l'acclimatation photosynthetique a un taux eleve de C[O.sub.2] et au rechauffement, car ils ont des effets opposes. Nous avons etudie les reponses physiologiques et morphologiques du bouleau gris (Betula papyrifera Marshall) a une combinaison de C[O.sub.2] et de temperature (ACT : 400 [micro]mol*[mol.sup.-1] C[O.sub.2], temperature actuelle; ECT : 750 [micro]mol*[mol.sup.-1] C[O.sub.2], temperature actuelle + 4[degrees]C). L'ECT a reduit la photosynthese, la carboxylation maximale de la Rubisco ([V.sub.cmax]), la vitesse maximale de transport des electrons ([J.sub.max]), la photorespiration, la respiration diurne, l'azote foliaire, la conductance stomatique et mesophylle, mais a augmente la biomasse, la hauteur, la surface foliaire totale, le ratio de partage des electrons vers la carboxylation et l'oxygenation et le point de compensation du C[O.sub.2]. L'acclimatation photosynthetique est conforme a la theorie du gain optimal de carbone (le gain de carbone determine la coordination de la carboxylation, du transport d'electrons et de la respiration). Alors que l'acclimatation photosynthetique etait similaire a l'acclimatation au C[O.sub.2] eleve, l'ECT a reduit [J.sub.max]/[V.sub.cmax], ce qui est coherent avec la reponse au rechauffement mais oppose a la reponse au C[O.sub.2] eleve, suggerant que l'acclimatation thermique peut etre le mecanisme principal de l'acclimatation photosynthetique a l'ECT et que l'ECT a probablement modifie l'allocation de l'azote entre la machinerie pour la carboxylation et celle pour la regeneration du RuBP (<< ribulose-1,5- bisphosphate >>). L'augmentation de la surface foliaire totale par l'ECT a plus que compense l'effet negatif de la deregulation photosynthetique sur la sequestration du carbone, ce qui a entraine une croissance plus rapide et une plus grande biomasse sous l'ECT. [Traduit par la Redaction] Mots-cles: bouleau gris (Betulapapyrifera Marshall), C[O.sub.2] eleve, acclimatation photosynthetique, transport d'electrons, surface foliaire, gain de carbone, Introduction Atmospheric C[O.sub.2] is expected to continue to increase in the foreseeable future, along with increasing temperature (Kurepin et al. 2018). The associated climate change will have far-reaching impacts on [...]

>22%--THE INCREASE in the global social cost of carbon attributable to tropical cyclones (TCs), according to new research published in Nature Communications. The study highlights the long-term cost of TCs [...]

We study the effect of human capital on C[O.sub.2] emissions using the Chinese provincial panel over the period 1997-2016. Allowing for cross-sectional dependence and structural breaks, we find a negative association between human capital and C[O.sub.2] emissions in the long run and attribute it to the influences from younger workers and workers with advanced human capital. In particular, our results suggest that a one-year increase in average schooling reduces C[O.sub.2] emissions by 12 per cent. Using disaggregated emission dataset by energy sources and end emitters, we demonstrate this negative association is likely to manifest through technology effect and the improvement in energy efficiency. These manifestations are limited to production sector. Our finding suggests a promising avenue for abating greenhouse gases without impeding economic growth. Keywords: Human capital, C[O.sub.2] emissions, Climate change, China, Panel model, 1. INTRODUCTION Investing in human capital has been shown to generate various benefits. For instance, human capital is conducive to labor productivity and facilitates economic growth (Schultz, 1961; Romer, 1990; [...]

Strengthen markets, measures and definitions for removing carbon dioxide from the atmosphere to fight climate change. Strengthen markets, measures and definitions for removing carbon dioxide from the atmosphere to fight climate change., Author(s): Lucas Joppa, Amy Luers, Elizabeth Willmott, S. Julio Friedmann, Steven P. Hamburg, Rafael Broze Author Affiliations: Microsoft's million-tonne CO[sub.2] -removal purchase -- lessons for net zero Climeworks' plant for [...]