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Author(s): Julia K. Green [sup.1] , Sonia I. Seneviratne [sup.2] , Alexis M. Berg [sup.3] , Kirsten L. Findell [sup.4] , Stefan Hagemann [sup.5] , David M. Lawrence [sup.6] , [...], Although the terrestrial biosphere absorbs about 25 per cent of anthropogenic carbon dioxide (CO.sub.2) emissions, the rate of land carbon uptake remains highly uncertain, leading to uncertainties in climate projections.sup.1,2. Understanding the factors that limit or drive land carbon storage is therefore important for improving climate predictions. One potential limiting factor for land carbon uptake is soil moisture, which can reduce gross primary production through ecosystem water stress.sup.3,4, cause vegetation mortality.sup.5 and further exacerbate climate extremes due to land-atmosphere feedbacks.sup.6. Previous work has explored the impact of soil-moisture availability on past carbon-flux variability.sup.3,7,8. However, the influence of soil-moisture variability and trends on the long-term carbon sink and the mechanisms responsible for associated carbon losses remain uncertain. Here we use the data output from four Earth system models.sup.9 from a series of experiments to analyse the responses of terrestrial net biome productivity to soil-moisture changes, and find that soil-moisture variability and trends induce large CO.sub.2 fluxes (about two to three gigatons of carbon per year; comparable with the land carbon sink itself.sup.1) throughout the twenty-first century. Subseasonal and interannual soil-moisture variability generate CO.sub.2 as a result of the nonlinear response of photosynthesis and net ecosystem exchange to soil-water availability and of the increased temperature and vapour pressure deficit caused by land-atmosphere interactions. Soil-moisture variability reduces the present land carbon sink, and its increase and drying trends in several regions are expected to reduce it further. Our results emphasize that the capacity of continents to act as a future carbon sink critically depends on the nonlinear response of carbon fluxes to soil moisture and on land-atmosphere interactions. This suggests that the increasing trend in carbon uptake rate may not be sustained past the middle of the century and could result in accelerated atmospheric CO.sub.2 growth.Earth system models suggest that soil-moisture variability and trends will induce large carbon releases throughout the twenty-first century.

Author(s): Terry T. Isson [sup.1] , Noah J. Planavsky [sup.1] Author Affiliations:(1) Department of Geology and Geophysics, Yale University, New Haven, USAMain Stability was a hallmark feature of Earth's early [...], For the first four billion years of Earth's history, climate was marked by apparent stability and warmth despite the Sun having lower luminosity.sup.1. Proposed mechanisms for maintaining an elevated partial pressure of carbon dioxide in the atmosphere ([Formula omitted]) centre on a reduction in the weatherability of Earth's crust and therefore in the efficiency of carbon dioxide removal from the atmosphere.sup.2. However, the effectiveness of these mechanisms remains debated.sup.2,3. Here we use a global carbon cycle model to explore the evolution of processes that govern marine pH, a factor that regulates the partitioning of carbon between the ocean and the atmosphere. We find that elevated rates of 'reverse weathering'--that is, the consumption of alkalinity and generation of acidity during marine authigenic clay formation.sup.4-7--enhanced the retention of carbon within the ocean-atmosphere system, leading to an elevated [Formula omitted] baseline. Although this process is dampened by sluggish kinetics today, we propose that more prolific rates of reverse weathering would have persisted under the pervasively silica-rich conditions.sup.8,9 that dominated Earth's early oceans. This distinct ocean and coupled carbon-silicon cycle state would have successfully maintained the equable and ice-free environment that characterized most of the Precambrian period. Further, we propose that during this time, the establishment of a strong negative feedback between marine pH and authigenic clay formation would have also enhanced climate stability by mitigating large swings in [Formula omitted]--a critical component of Earth's natural thermostat that would have been dominant for most of Earth's history. We speculate that the late ecological rise of siliceous organisms.sup.8 and a resulting decline in silica-rich conditions dampened the reverse weathering buffer, destabilizing Earth's climate system and lowering baseline [Formula omitted].Elevated rates of reverse weathering within silica-rich oceans led to enhanced carbon retention within the ocean-atmosphere system, promoting a stable, equable ice-free climate throughout Earth's early to middle ages.

We study the economics of carbon storage using a model that includes forest size structure and determines the choice between rotation forestry and continuous cover forestry. Optimal harvests may rely solely on thinning, implying infinite rotation and continuous cover forestry, or both thinning and clearcuts, implying finite rotation periods. Given several carbon prices and interest rates, we optimize the timing and intensity of thinnings along with the choice of management regime. In addition to the carbon storage in living trees, we include the carbon dynamics of dead trees and timber products. Forest growth is specified by an empirically validated transition matrix model for Norway spruce (Picea abies (L.) Karst.). The optimization problem is solved in its general dynamic form by applying bilevel optimization with gradient-based interior point methods and a genetic algorithm. Carbon pricing postpones thinnings, increases stand density by directing harvests to larger trees, and typically yields a regime shift from rotation forestry to continuous cover forestry. In continuous cover solutions, the steady-state harvesting interval and the diameter distribution of standing and harvested trees are sensitive to carbon price, implying that carbon pricing increases the sawlog ratio of timber yields. Additionally, we obtain relatively inexpensive stand-level marginal costs of carbon storage. Key words: carbon sequestration, carbon subsidy, continuous cover forestry, management regimes, optimal rotation, uneven-aged forestry. Nous etudions l'economie du stockage de carbone en utilisant un modele qui inclut la structure de la foret et qui permet de choisir entre des rotations forestieres et un couvert forestier permanent. Les recoltes optimales peuvent dependre uniquement de l'eclaircie, ce qui implique une rotation infinie, creant ainsi un couvert forestier permanent, ou de l'eclaircie et de la coupe totale, ce qui implique des periodes de rotation finies. Etant donne plusieurs prix de carbone et differents taux d'interet, nous optimisions le calendrier et l'intensite des eclaircies, de meme que le choix du regime d'amenagement. En plus du stockage de carbone dans les arbres vivants, nous incluons la dynamique du carbone dans le bois mort et dans les produits du bois. La croissance forestiere est specifiee par un modele matriciel de transition valide empiriquement pour l'epinette de Norvege (Picea abies (L.) Karst.). Le probleme d'optimisation est resolu selon la forme dynamique generale en appliquant une optimisation a deux niveaux avec des methodes basees sur des gradients de point interieur et un algorithme genetique. La tarification du carbone retarde les eclaircies, augmente la densite du peuplement en dirigeant la recole vers de plus gros arbres, et provoque generalement un changement d'approche d'une foresterie a rotations finies vers un couvert forestier permanent. Dans les alternatives a couvert continu, l'intervalle de recolte pour atteindre l'etat d'equilibre et la distribution des diametres des arbres sur pied et recoltes sont sensibles au prix du carbone, ce qui implique que la tarification du carbone augmente le ratio de sciage dans les rendements en bois. De plus, nous obtenons des couts marginaux de stockage du carbone relativement faibles a l'echelle du peuplement. [Traduit par la Redaction] Mots-cles: sequestration de carbone, subvention pour le carbone, couvert forestier permanent, regimes d'amenagement, rotation optimale, structure forestiere inequienne., 1. Introduction Forest ecosystems, holding more than double the amount of carbon in the atmosphere, are a crucial part of the global carbon cycle (Food and Agriculture Organization of the [...]

Author(s): Sebastiaan Luyssaert [sup.1] [sup.2] , Guillaume Marie [sup.1] , Aude Valade [sup.3] [sup.5] , Yi-Ying Chen [sup.2] [sup.6] , Sylvestre Njakou Djomo [sup.4] , James Ryder [sup.2] [sup.7] , [...], The Paris Agreement promotes forest management as a pathway towards halting climate warming through the reduction of carbon dioxide (CO.sub.2) emissions.sup.1. However, the climate benefits from carbon sequestration through forest management may be reinforced, counteracted or even offset by concurrent management-induced changes in surface albedo, land-surface roughness, emissions of biogenic volatile organic compounds, transpiration and sensible heat flux.sup.2-4. Consequently, forest management could offset CO.sub.2 emissions without halting global temperature rise. It therefore remains to be confirmed whether commonly proposed sustainable European forest-management portfolios would comply with the Paris Agreement--that is, whether they can reduce the growth rate of atmospheric CO.sub.2, reduce the radiative imbalance at the top of the atmosphere, and neither increase the near-surface air temperature nor decrease precipitation by the end of the twenty-first century. Here we show that the portfolio made up of management systems that locally maximize the carbon sink through carbon sequestration, wood use and product and energy substitution reduces the growth rate of atmospheric CO.sub.2, but does not meet any of the other criteria. The portfolios that maximize the carbon sink or forest albedo pass only one--different in each case--criterion. Managing the European forests with the objective of reducing near-surface air temperature, on the other hand, will also reduce the atmospheric CO.sub.2 growth rate, thus meeting two of the four criteria. Trade-off are thus unavoidable when using European forests to meet climate objectives. Furthermore, our results demonstrate that if present-day forest cover is sustained, the additional climate benefits achieved through forest management would be modest and local, rather than global. On the basis of these findings, we argue that Europe should not rely on forest management to mitigate climate change. The modest climate effects from changes in forest management imply, however, that if adaptation to future climate were to require large-scale changes in species composition and silvicultural systems over Europe.sup.5,6, the forests could be adapted to climate change with neither positive nor negative climate effects.Simulations of commonly proposed forest-management portfolios for Europe show that no single portfolio would meet all the requirements of the Paris Agreement, and climate benefits from forest management would be modest and local.

The coastal ocean consists of several distinct but tightly connected ecosystems that include rivers, estuaries, tidal wetlands and the continental shelf. Carbon cycling in the coastal waters that connect terrestrial [...], The carbon cycle of the coastal ocean is a dynamic component of the global carbon budget. But the diverse sources and sinks of carbon and their complex interactions in these waters remain poorly understood. Here we discuss the sources, exchanges and fates of carbon in the coastal ocean and how anthropogenic activities have altered the carbon cycle. Recent evidence suggests that the coastal ocean may have become a net sink for atmospheric carbon dioxide during post-industrial times. Continued human pressures in coastal zones will probably have an important impact on the future evolution of the coastal ocean's carbon budget.

Byline: P. Ciais (1), P. Rayner (1), F. Chevallier (1), P. Bousquet (1), M. Logan (1), P. Peylin (1,2), M. Ramonet (1) Abstract: We provide a review description of atmospheric inversion methods for the determination of fluxes of long-lived trace gases based on measurements of atmospheric concentration. Emphasis is given to technical aspects of inversion settings, which are crucial to inter-compare and understand inversion results. We briefly sketch the formalism used in such methods, then provide a summary of major currents in research and contemporary problems. Most attention is given to carbon dioxide (CO.sub.2) which poses the threat of future climate change. Therefore, there is keen interest in better understanding where and when CO.sub.2 emitted by the combustion of fossil fuels is reabsorbed by land ecosystems and oceans. Using the information contained in concentration fields observed from ground-based networks and from upcoming satellite observations in order to constrain the geographic distribution of surface fluxes is an inverse problem it consists of finding a set of fluxes that optimally matches the observations available. We review the application of inverse methods to quantify the distribution of the sources and sinks of CO.sub.2 at the surface of the Earth based on global measurements of atmospheric concentration and three-dimensional models of atmospheric transport. We describe the use of top--down atmospheric inversion methods in terms of numerical transport modeling and atmospheric observation networks, and detail some of the currently important issues in assigning uncertainties. Author Affiliation: (1) Unite Mixte de Recherche LSCE, CEA-CNRS-UVSQ, Batiment 709, CE Orme des Merisiers, 91191, Gif sur Yvette, France (2) Unite Mixte de Recherche BioMCo, INRA-CNRS-INAPG, Universite Paris 6, Batiment EGER, 78850, Thivernal-Grignon, France Article History: Registration Date: 22/06/2010 Received Date: 05/01/2009 Accepted Date: 15/06/2010 Online Date: 20/07/2010

Simulating the effects of possible environmental changes on the forest carbon budget requires the use of calibrated and tested models of ecosystem processes. A recently proposed simulation approach based on the use of the BIOME-BGC model was applied to yield estimates of present carbon fluxes and pools in Tuscany forests (central Italy). After the validation of these estimates against existing ground data, the simulation approach was used to assess the impact of plausible climate changes (+2 °C and increased [CO.sub.2] concentration) on forest carbon dynamics (gross primary production (GPP), net primary production (NPP), and relevant allocations). The results indicate that the temperature change tends to inhibit all production and allocation processes, which are instead enhanced by the [CO.sub.2] concentration rise. The combination of the two factors leads to a general increase in both GPP and NPP that is higher for deciduous oaks and chestnut (+30% and 24% for GPP and +42% and 31% for NPP, respectively). Additionally, vegetation carbon is slightly increased, while total soil carbon remains almost unchanged with respect to the present conditions. These findings are analyzed with reference to the Tuscany forest situation and previous studies on the subject. Resume: Pour simuler les effets de changements environnementaux potentiels sur le bilan du carbone des forets, il faut utiliser des modeles de processus des ecosystemes qui ont ete calibres et testes. Une approche de simulation proposee recemment et basee sur l'utilisation du modele BIOME-BCG a ete appliquee pour produire des estimations des flux actuels et des reservoirs de carbone dans les forets de la Toscane, dans le centre de l'Italie. Apres avoir valide ces estimations avec les donnees terrain existantes, la simulation a ete utilisee pour evaluer l'impact de changements climatiques plausibles (+2 °C et augmentation de la concentration de [CO.sub.2]) sur la dynamique du carbone de la foret (production primaire brute (PPB), production primaire nette (PPN) et les locations pertinentes). Les resultats indiquent que le changement de temperature a tendance a inhiber tous les processus de production et d'allocation qui sont par contre stimules par l'augmentation de la concentration de [CO.sub.2]. La combinaison des deux facteurs se traduit par une augmentation generale de la PPB et de la PPN qui est plus elevee chez les chenes caducifolies et le chataignier (respectivement +30% et 24% pour la PPB et +42% et 31% pour la PPN). De plus, la quantite de carbone dans la vegetation est legerement plus elevee tandis que la quantite totale de carbone dans le sol demeure pratiquement inchangee par rapport aux conditions actuelles. Ces resultats sont analyses a la lumiere de la situation de la foret toscane et des etudes precedentes sur le sujet. [Traduit par la Redaction], Introduction The increasing level of atmospheric [CO.sub.2] and consequent global climate change are enhancing the need for assessing the amount of carbon stored by terrestrial ecosystems as well as for [...]

Little information exists regarding the effects of intermediate stand management activities (e.g., thinning) on C storage. This lack of information has created uncertainty regarding trade-offs between the benefits observed following thinning and C storage. Using long-term growth data, this study examines the effect of thinning on C storage while controlling for the effects of site quality in yellow-poplar (Liriodendron tulipifera L.) forests throughout the southern Appalachian Mountains. In 1960, one hundred and eighteen 0.1 ha plots were established in yellow-poplar forests throughout the southern Appalachians and subsequently thinned to a randomly assigned residual basal area (RBA) (square metres per hectare). Carbon storage increased through time across all levels of RBA. RBA had a long-term effect on C storage with greater C storage occurring at greater RBA. On average-quality sites, thinning to 30 [m.sup.2]*[ha.sup.-1] stored 84% more C than thinning to 10 [m.sup.2]*[ha.sup.-1]. At no time did plots with progressively lower RBA store more C than plots with progressively higher RBA. The results from this study provide information about the effects of intermediate silvicultural disturbance on C dynamics of the aboveground live tree pool in a complex landscape and may be used to inform decisions regarding trade-offs between active management and C storage. Resume: Il existe peu d'informations sur les effets des activites intermediaires d'amenagement forestier (p. ex. l'eclaircie) sur l'entreposage de C. Ce manque d'informations est a la source d'incertitudes concernant les compromis entre les benefices observes a la suite d'une eclaircie et l'entreposage de C. A l'aide de donnees de croissance a long terme, cette etude evalue l'effet de l'eclaircie sur l'entreposage de C en tenant compte de l'effet de la qualite de station dans des forets domine es par le tulipier de Virginie (Liriodendron tulipifera L.) dans le sud des Appalaches. En 1960, 118 parcelles de 0,1 ha ont ete etablies dans des forets de tulipier du sud des Appalaches et elles ont ensuite ete eclaircies en leur assignant aleatoirement une surface terriere residuelle (STR) (metres carres par hectare). L'entreposage de C a augmente avec le temps pour toutes les valeurs de STR. La STR a eu un effet a long terme sur l'entreposage de C: l'entreposage de C etait plus eleve pour les plus grandes valeurs de STR. Sur les stations de qualite moyenne, une eclaircie laissant une STR de 30 [m.sup.2]*[ha.sup.-1] entreposait 84% plus de C qu'une eclaircie laissant une STR de 10 [m.sup.2]*[ha.sup.-1]. Les parcelles dont les valeurs de la STR etaient progressivement plus faibles n'ont jamais entrepose plus de C que les parcelles dont les valeurs de la STR etaient progressivement plus elevees. Les resultats de cette etude fournissent des informations sur les effets d'une perturbation sylvicole intermediaire sur la dynamique du C de la partie aerienne des arbres etablis dans un paysage complexe. Ces informations peuvent etre utilisees pour eclairer les decisions concernant les compromis entre l'amenagement actif et l'entreposage du C. [Traduit par la Redaction], Introduction Intermediate stand management activities (e.g., thinning) are implemented to achieve numerous resource management objectives including, but not limited to, the improvement and maintenance of wildlife habitat, wildfire hazard reduction, [...]

Forest managers are seeking strategies to create stands that can adapt to new climatic conditions and simultaneously help mitigate increases in atmospheric [CO.sub.2]. Adaptation strategies often focus on enhancing resilience by maximizing forest complexity in terms of species composition and size structure, while mitigation involves sustaining carbon storage and sequestration. Altered stand age is a fundamental consequence of forest management, and stand age is a powerful predictor of ecosystem structure and function in even-aged stands. However, the relationship between stand age and either complexity or carbon storage and sequestration, especially trade-offs between the two, are not well characterized. We quantified these relationships in clearcut-origin, unmanaged pine and aspen chronosequences ranging from 130 years in northern Minnesota. Complexity generally increased with age, although compositional complexity changed more over time in aspen forests and structural complexity changed more over time in pine stands. Although individual carbon pools displayed various relationships with stand age, total carbon storage increased with age, whereas carbon sequestration, inferred from changes in storage, decreased sharply with age. These results illustrate the carbon and complexity consequences of varying forest harvest rotation length to favor younger or older forests and provide insight into trade-offs between these potentially conflicting management objectives. Resume: Les amenagistes forestiers cherchent des strategies pour creer des peuplements capables de s'adapter aux nouvelles conditions climatiques tout en contribuant a attenuer l'augmentation de [CO.sub.2] atmospherique. Les strategies d'adaptation sont souvent axees sur l'amelioration de la resilience en maximisant la complexite de la foret en termes de composition et de structure de dimension des especes tandis que les mesures d'attenuation visent l'accumulation et la sequestration soutenues du carbone. La modification de l'age du peuplement est une consequence fondamentale de l'amenagement forestier et l'age du peuplement est un puissant predicteur de la fonction et de la structure de l'ecosysteme dans les peuplements equiennes. Cependant, les relations entre l'age et la complexite de la foret ou l'accumulation et la sequestration du carbone et plus particulierement les compromis entre les deux ne sont pas bien caracterises. Nous avons quantifie ces relations dans des chronosequences non amenagees de pin et de peuplier issues de coupes a blanc et allant de 130 ans dans le nord du Minnesota. La complexite de la foret augmentait generalement avec l'age, quoiqu'avec le temps la complexite compositionnelle variait plus dans les forets de peuplier alors qu'avec le temps la complexite structurelle variait davantage dans les peuplements de pin. Bien que les reservoirs individuels de carbone aient montre differentes relations avec l'age du peuplement, l'accumulation totale de carbone augmentait avec l'age tandis que la sequestration du carbone, deduite a partir des changements dans l'accumulation, diminuait brusquement avec l'age. Ces resultats illustrent les consequences sur le carbone et la complexite de differents ages d'exploitabilite selon qu'on favorise des forets plus jeunes ou plus vieilles et donnent une idee des compromis entre ces objectifs d'amenagement potentiellement contradictoires. [Traduit par la Redaction], Introduction As the reality of climate change becomes increasingly apparent (IPCC 2007), forest managers are urgently seeking strategies to create stands that can both adapt to new climatic conditions and [...]

Author(s): Kiona OgleAuthor Affiliations:Hyperactive soil microbes might weaken the terrestrial carbon sink A variety of processes underlie the exchange of CO[sub.2] between the land surface and the atmosphere. Bond-Lamberty et [...], The rate at which carbon dioxide is lost from soil has risen faster than the rate at which it is used by land plants, because soil microbes have become more active -- possibly weakening the land surface's ability to act as a carbon sink.The rate at which carbon dioxide is lost from soil has risen faster than the rate at which it is used by land plants, because soil microbes have become more active -- possibly weakening the land surface's ability to act as a carbon sink.

China's terrestrial biosphere constitutes a net carbon sink comparable to Europe and roughly two-thirds that of the continental U.S. Another research found that moderately and extensively thawed permafrost sites served as net carbon sinks during the summer but released more carbon than minimally thawed sites. Research on a flood resistant rice is also discussed.

The sequestration of organic matter in marine sediments is a primary mechanism by which carbon is removed from the atmosphere and stored over geological periods of time. Only a tiny [...]