Academic literature on the topic 'Carbon allocation'

To achieve the commitment of carbon emission reduction in 2030 at the climate conference in Paris, it is an important task for China to decompose the carbon emission target among regions. In this paper, entropy maximization is brought to inter-provincial carbon emissions allocation via the Boltzmann distribution method, which provides guidelines for allocating carbon emissions permits among provinces. The research is mainly divided into three parts: (1) We develop the CO2 influence factor, including per capita GDP, per capita carbon emissions, carbon emission intensity and carbon emissions of per unit industrial added value; the proportion of the second industry; and the urbanization rate, to optimize the Boltzmann distribution model. (2) The probability of carbon emission reduction allocation in each province was calculated by the Boltzmann distribution model, and then the absolute emission reduction target was allocated among different provinces. (3) Comparing the distribution results with the actual carbon emission data in 2015, we then put forward the targeted development strategies for different provinces. Finally, suggestions were provided for CO2 emission permits allocation to optimize the national carbon emissions trading market in China.

Weeds increase their dominance in a grazed plant community by avoiding herbivory and (or) by tolerating herbivory more than neighbouring plants. After defoliation, allocating carbon to shoots at the expense of roots may confer tolerance. We determined carbon allocation patterns of undefoliated and recently defoliated (75% clipping level) plants of the invasive leafy spurge (Euphorbia esula L.) growing with alfalfa (Medicago sativa L.), Kentucky bluegrass (Poa pratensis L.), or Idaho fescue (Festuca idahoensis Elmer). Plants were labeled with 13CO2 24 h after clipping to determine allocation patterns; all plants had equal access to the 13CO2. Based on relative distribution of 13C, defoliation did not affect the amount of carbon allocated to roots of E. esula. The amount of carbon allocated to shoots of E. esula was higher when growing with P. pratensis than when growing with the other species. Based on relative enrichment of 13C, defoliation increased sink strength of remaining shoots on defoliated E. esula plants. Conversely, roots of unclipped E. esula plants were stronger sinks for carbon than roots of clipped plants. Even though defoliation increased "sink strength" of remaining shoots of E. esula, the amount of carbon allocated to the root system was unaffected by defoliation, suggesting that uninterrupted allocation of carbon to its extensive root system, not increased allocation to its shoot system, confers grazing tolerance.

Effectively allocating emission control targets is critical for China to achieve its emission reduction goals. This study researched the efficiency of total carbon dioxide (CO2) emission control target allocations during the 13th Five-Year Plan period (2015–2020). The efficiency of carbon intensity reduction targets, allocated by the National Development and Reform Commission in 30 regions, was assessed using a Directional Distance Function (DDF) model. Then, a Zero-Sum Gains (ZSG)-DDF model was constructed to determine how to optimally allocate total CO2 emission, under the premise of maximizing economic benefits and minimizing CO2 emissions. The results showed that in the case of fixed total CO2 emissions, to improve the resource allocation efficiency, the quota should be increased in the regions with high efficiencies, and the quota should be reduced in the regions with low efficiencies. The results in this paper can help guide the future allocations of total CO2 emission in China.

Abstract Carbon allocation plays a key role in ecosystem dynamics and plant adaptation to changing environmental conditions. Hence, proper description of this process in vegetation models is crucial for the simulations of the impact of climate change on carbon cycling in forests. Here we review how carbon allocation modelling is currently implemented in 31 contrasting models to identify the main gaps compared with our theoretical and empirical understanding of carbon allocation. A hybrid approach based on combining several principles and/or types of carbon allocation modelling prevailed in the examined models, while physiologically more sophisticated approaches were used less often than empirical ones. The analysis revealed that, although the number of carbon allocation studies over the past 10 years has substantially increased, some background processes are still insufficiently understood and some issues in models are frequently poorly represented, oversimplified or even omitted. Hence, current challenges for carbon allocation modelling in forest ecosystems are (i) to overcome remaining limits in process understanding, particularly regarding the impact of disturbances on carbon allocation, accumulation and utilization of nonstructural carbohydrates, and carbon use by symbionts, and (ii) to implement existing knowledge of carbon allocation into defence, regeneration and improved resource uptake in order to better account for changing environmental conditions.

This paper considers a carbon emission cap and trade market, where the carbon emission cap for each entity (either government or firm) is allocated first and then the carbon trading price is decided interdependently in the carbon trading market among the non-cooperative entities which make their production decision. We assume that there are n entities emitting carbon during the production process. After allocating the carbon (emission) cap for each participating entity in the carbon cap and trade market, each participant makes a production decision using the Newsvendor model given carbon trading price determined in the carbon trading market and trades some amount of its carbon emission, if its carbon emission is below or above its own carbon cap. Here, the carbon trading price depends on how carbon caps over the entities are allocated, since the carbon trading price is determined through the carbon (emission) trading market, which considers total amount of carbon emission being equal to total carbon caps over entities and some fraction of total carbon emission should be from each entity participating in the carbon cap and trade market. Thus, we can see the interdependency among the production decision, carbon cap and carbon trading price. We model this as a non-cooperative Stackelberg game in which carbon cap for each entity is allocated in the first stage and each entity’s production quantity is decided in the second stage considering the carbon trading price determined in the carbon trading market. First, we show the monotonic property of the carbon trading price and each entity’s production over the carbon cap allocation. In addition, we show that there exists an optimality condition for the carbon cap allocation. Using this optimality condition, we provide various results for carbon cap and trade market.

Rational scheme of initial allocation of carbon emission rights is the key to the smooth running of carbon trading market. Based on the traditional carbon emission rights allocation mode, this paper combining China’s actual development of power industry and characteristics of the distribution of generation resources, put forward the impact of initial allocation of carbon emission rights on power generation replacement analysis model. By studying the impact of initial allocation of carbon emission rights on power generation rights trade, and comparing the different results of power generation rights trade, respectively, based on installed capacity allocation and power generation allocation, it is found that the mode that based on power generation allocation can better promote the power generation rights trade.

Plants spend a high proportion of their photosynthetically fixed carbon (C) belowground to root biomass, rhizodeposition or to support mycorrhizal fungi in exchange for nutrients while most of this C expenditure is associated with root and hyphal respiration. This thesis aimed to investigate the controls on plants’ C allocation belowground, and what the consequences are for microbial carbon use efficiency (CUE) of soil- vs plant-derived C and for mediating N dynamics. In module system one, four wheat genotypes with variated root traits, biomass and rhizodeposition were grown in pots under two levels of nitrogen (25 and 100 kg N ha-1) and phosphorus (10 and 40 kg P ha-1) fertiliser. Module system two was conducted in a grassland at field condition with two levels of N fertiliser (0 and 100 kg N ha-1) and two levels of clipping intensity (low and high, high applied as double). A continuous and pulse 13CO2 labelling methods was used to quantify rhizodeposition in module system 1 and 2 respectively, and H218O and 15N pool dilution technique to examine CUE and gross N mineralsiation (GNM), respectively. Results showed that plant C allocation to rhizodeposition vs. arbuscular mycorrhizal fungi (AMF) association is mediated by N and P availability. N fertilisation increased AMF association in both module systems, likely because of N-induced P limitation. Although, supporting AMF is C costly, plants sustained supporting AMF with C limitation induced by defoliation in module system 2, resulted in greater root respiration but decreased rhizodeposition. N fertilisation decreased and increased rhizodeposition in module system 1 and 2, respectively, where increased rhizodeposition increased the decomposition, did not affect GNM but contributed to reduced net N mineralisation (NNM) due to microbial N immobilisation at high N. To conclude, plants C allocation belowground is mediated by relative resource availabilities of N, P, and C interacting terrestrial biogeochemistry.

Doctor of Philosophy
Department of Agronomy
Charles W. Rice
Increasing atmospheric CO2 concentrations and other greenhouse gases have been linked to global climate change. Soil organic C (SOC) sequestration in both agricultural and native ecosystems is a plausible option to mitigate increasing atmospheric CO2 in the short term. Laboratory and field studies were conducted to (1) understand the influence of soil water content on the temperature response of SOC mineralization (2) investigate burn and nutrient amendment effects on biogeochemical properties of tallgrass prairie and (3) assess perennial and annual plant management practices on biophysical controls on SOC dynamics. The laboratory study was conducted using soils collected from an agricultural field, currently planted to corn (C4 crop), but previously planted to small grain (C3) crops. The changes in cultivated crops resulted in a δ¹³C isotopic signature that was useful in distinguishing older from younger soil derived CO2-C during SOC mineralization. Soils were incubated at 15, 25 and 35 oC, under soil water potentials of -1, -0.03 and -0.01 MPa. Soil water content influenced the effect of temperature on SOC mineralization. The impact of soil water on temperature effect on SOC mineralization was greater under wetter soil conditions. Both young and older SOC were temperature sensitive, but SOC loss depended on the magnitude of temperature change, soil water content and experiment duration. Microbial biomass was reduced with increasing soil water content. The first field experiment investigated burn and nutrient amendment effects on soil OC in a tallgrass prairie ecosystem. The main plots were burned (B) and unburned (UB) tallgrass prairie and split plots were nutrient amendments (N, P or N+P including controls). Vegetation was significantly altered by burning and nutrient amendment. Treatment effects on either TN or SOC were depth-specific with no impact at the cumulative 0-30 cm depth. The P amendment increased microbial biomass at 0-5 cm which was higher in unburned than burned. However, at 5-15 cm depth N amendment increased microbial biomass which was higher in burned than unburned. In conclusion, soil OC in both burned and unburned tallgrass prairie may have a similar trajectory however; the belowground dynamics of the burned and unburned tallgrass prairie are apparently different. Another field experiment assessed SOC dynamics under perennial and annual plant management practices. The main plots were grain sorghum (Sorghum bicolor) planted in no-tillage (NT) or continuous tillage (CT), and replanted native prairie grass, (Andropogon gerardii) (RP). The spit plots were phosphorus (+P) and control without P (-P). The P amendment was used to repress arbuscular mycorrhizal fungi (AMF), known to influence soil aggregation. The macroaggregate >250 µm, SOC and TN were higher in RP and NT than CT. The relative abundances of AMF and saprophytic fungi were greater with less soil disturbance in RP and NT than in CT. Therefore, less soil disturbance in RP and NT increased AMF and fungal biomasses. The higher relative abundances of AMF and fungi with less soil disturbance increased macroaggregate formation in RP and NT, which resulted in higher SOC sequestration in RP and NT than CT.

Carbon fluxes and allocation pattern, and their relationship with the main environmental and physiological parameters, were studied in an apple orchard for one year (2010). I combined three widely used methods: eddy covariance, soil respiration and biometric measurements, and I applied a measurement protocol allowing a cross-check between C fluxes estimated using different methods. I attributed NPP components to standing biomass increment, detritus cycle and lateral export. The influence of environmental and physiological parameters on NEE, GPP and Reco was analyzed with a multiple regression model approach. I found that both NEP and GPP of the apple orchard were of similar magnitude to those of forests growing in similar climate conditions, while large differences occurred in the allocation pattern and in the fate of produced biomass. Apple production accounted for 49% of annual NPP, organic material (leaves, fine root litter, pruned wood and early fruit drop) contributing to detritus cycle was 46%, and only 5% went to standing biomass increment. The carbon use efficiency (CUE), with an annual average of 0.68 ± 0.10, was higher than the previously suggested constant values of 0.47-0.50. Light and leaf area index had the strongest influence on both NEE and GPP. On a diurnal basis, NEE and GPP reached their peak approximately at noon, while they appeared to be limited by high values of VPD and air temperature in the afternoon. The proposed models can be used to explain and simulate current relations between carbon fluxes and environmental parameters at daily and yearly time scale. On average, the annual NEP balanced the carbon annually exported with the harvested apples. These data support the hypothesis of a minimal or null impact of the apple orchard ecosystem on net C emission to the atmosphere.

Carbon fluxes and allocation pattern, and their relationship with the main environmental and physiological parameters, were studied in an apple orchard for one year (2010). I combined three widely used methods: eddy covariance, soil respiration and biometric measurements, and I applied a measurement protocol allowing a cross-check between C fluxes estimated using different methods. I attributed NPP components to standing biomass increment, detritus cycle and lateral export. The influence of environmental and physiological parameters on NEE, GPP and Reco was analyzed with a multiple regression model approach. I found that both NEP and GPP of the apple orchard were of similar magnitude to those of forests growing in similar climate conditions, while large differences occurred in the allocation pattern and in the fate of produced biomass. Apple production accounted for 49% of annual NPP, organic material (leaves, fine root litter, pruned wood and early fruit drop) contributing to detritus cycle was 46%, and only 5% went to standing biomass increment. The carbon use efficiency (CUE), with an annual average of 0.68 ± 0.10, was higher than the previously suggested constant values of 0.47-0.50. Light and leaf area index had the strongest influence on both NEE and GPP. On a diurnal basis, NEE and GPP reached their peak approximately at noon, while they appeared to be limited by high values of VPD and air temperature in the afternoon. The proposed models can be used to explain and simulate current relations between carbon fluxes and environmental parameters at daily and yearly time scale. On average, the annual NEP balanced the carbon annually exported with the harvested apples. These data support the hypothesis of a minimal or null impact of the apple orchard ecosystem on net C emission to the atmosphere.

Rapid climate change in Arctic regions is of concern due to important feedbacks between the Arctic land surface and the global climate system. A large amount of organic carbon (C) is currently stored in Arctic soils; if decomposition is stimulated under warmer conditions additional release of CO2 could result in an accelerating feedback on global climate. The strength and direction of Arctic C cycle - climate feedbacks will depend on the growth response of vegetation; if plant growth increases some or all of the extra CO2 emissions may be offset. Currently the Arctic is thought to be a small net sink for CO2, the expected balance of terrestrial C sinks and sources in the future is unknown. In this thesis I explore some of the critical unknowns in current understanding of C cycle dynamics in Arctic vegetation. Quantifying gross primary productivity (GPP) over regional scales is complicated by large spatial heterogeneity in plant functional type (PFT) in Arctic vegetation. I use data from five Arctic sites to test the generality of a relationship between leaf area index (LAI) and canopy total foliar nitrogen (TFN). LAI and TFN are key drivers of GPP and are tightly constrained across PFTs in Low Arctic Alaska and Sweden, therefore greatly simplifying the task of up-scaling. I use data from Greenland, Barrow and Svalbard to asses the generality of the LAI-TFN relationship in predicting GPP at higher Arctic latitudes. Arctic ecosystems are unique among biomes in the large relative contribution of bryophytes (mosses, liverworts and hornworts) to plant biomass. The contribution of bryophytes to ecosystem function has been relatively understudied and they are poorly represented in terrestrial C models. I use ground based measurements in Northern Sweden to fill an existing data gap by quantifying CO2 fluxes from bryophytes patches in early spring and summer, and develop a simple model of bryophyte GPP. Using the model I compare bryophyte GPP to that of vascular plants before, during and after the summer growing season, finding that productive bryophyte patches can contribute up to 90 % of modelled annual GPP for typical vascular plant communities at the same site, and that the relative magnitude of bryophyte GPP is greatest in spring whilst the vascular plant canopy is still developing. Understanding how GPP relates to plant growth is important in relating remotely sensed increases in Arctic ‘greenness’ to changes in plant C stocks. I use a 13C pulselabelling techniques to follow the fate of recently fixed C in mixed vascular and bryophyte vegetation, with a focus on quantifying the contribution of bryophytes to ecosystem carbon use efficiency (CUE). I show that bryophytes contribute significantly to GPP in mixed vegetation, and act to increase ecosystem CUE. I highlight the importance of including bryophytes, which do not have roots, in aboveground: belowground partitioning schemes in C models. To further explore C turnover in bryophytes, I use the results of a second 13C labelling experiment to develop a model of C turnover in two contrasting Arctic mosses (Polytrichum piliferum and Sphagnum fuscum). I find significant differences in C turnover between Polytrichum piliferum which respires or translocates about 80 % of GPP, while Sphagnum fuscum respires 60 %. This analysis is the first to explicitly model differences in C partitioning between Arctic bryophyte species. Finally, I discuss the implications of each chapter for our understanding of Arctic C dynamics, and suggest areas for further research.

This thesis focuses on the impact of elevated ozone (O3) and/or nitrogen (N) on semi-natural vegetation, with an emphasis on C-partitioning within and between plant and soil. The project reports several studies allied to the exploration of the impacts of elevated O3 and N employing short-term studies in laboratory-based controlled-environment chambers and solardomes plus long-term studies at free-air O3 fumigation sites in the Swiss Alps and at Keenley Fell, Northumberland, UK. A solardome study indicated that both the grass Dactylis glomerata, and the forb Ranunculus acris exhibited increased senescence, and reduced C-allocation below-ground, when exposed to elevated [O3]. Furthermore, N exacerbated the O3-induced reduction in the root biomass of D. glomerata. This finding led to a mechanistic exploration of C-partitioning in response to short-term (three week) exposure of D. glomerata to a combination of elevated O3 and N inputs in self-built fumigation chambers. Plants were pulse-labelled with 14C, and the fate of the recent photosynthate then traced in nine plant and soil C-pools. The study revealed a reduction in below-ground respiration (incorporating root and soil microbial respiration) in high N treated plants, and a significant antagonistic interaction between O3 and N effects on soil microbial biomass. To relate the findings to below-ground responses in an intact ecosystem, impacts of long-term O3 and N exposure on soil microbial community diversity and C metabolism were investigated in a sub-alpine grassland. Terminal Restriction Fragment Length Polymorphism (T-RFLP) analysis and Community Level Physiological Profiling (CLPP) using 14C labelled root exudate substrates and leaf litter, revealed no effects of O3 and N on the soil bacterial diversity, and limited impacts on C substrate turnover. Moreover, in a long-term study on a traditional UK haymeadow, three years of elevated O3 and N inputs did not result in significant changes in above-ground biomass of any plant functional group. However, a significant O3 x N interaction on below-ground biomass of the sward was observed with reduced root biomass in high [O3] plots. The variation in cover of individual plant species was not explained by either O3 or N when analysed by redundancy analysis (RDA). Overall, this study suggests that N deposition subtly modifies vegetation responses to O3 stress and highlights the potentially significant role played by rising levels of N deposition and O3 as drivers of changes in carbon allocation in the natural environment. Key words: Ozone; nitrogen; carbon allocation; grassland; microbial diversity

1 ABSTRACT Negli oceani attuali, il fitoplancton è principalmente dominato dalle microalghe della linea rossa, con clorofilla a e c, mentre le microalghe della linea verde, con clorofilla a e b, contribuiscono solo in misura minore. Tuttavia, la composizione specifica del fitoplancton è cambiata nel corso dei tempi geologici e le microalghe della linea verde dominavano gli oceani dell’Era Paleozoica, mentre, a partire dall’Era Mesozoica, le alghe della linea rossa diventarono dominanti e diedero origine ai gruppi che sono più importanti negli oceani attuali. Questo cambiamento di dominanza del fitoplancton è stato messo in relazione con la variazione della chimica degli oceani che si è verificata lungo la scala dei tempi geologici. La concentrazione di SO42- negli oceani è aumentata in maniera monotonica dall’Era Paleozoica (~1-10 mmol L-1 SO42-) a oggi (28 mmol L-1 SO42-). Nonostante sia difficile avere informazioni dettagliate sull’abbondanza di NO3- e PO4- negli oceani del passato, ci sono evidenze che anche il rapporto N:P sia cambiato lungo la scala dei tempi geologici, e che gli oceani siano passati dalla limitazione da P a quella da N, dall’Era Paleozoica al presente. Inoltre, il cambiamento dello stato redox degli oceani causato dall’accumulo di O2 rilasciato dalla fotosintesi dal Neo-Proterozoico alla fine del Paleozoico, ha determinato il cambiamento dell’abbondanza di alcuni metalli in tracce, come Fe, Cu, Mn, Mo, Cd e Zn. È stato ipotizzato che la stechiometria elementale media possa essere il link tra il cambiamento della chimica degli oceani e il successo evolutivo delle microalghe della linea rossa. È stato riportato che le microalghe della linea rossa hanno una maggiore richiesta di quegli elementi (S, P, Mn) la cui disponibilità è aumentata quando gli oceani sono diventati più ossidati; il contrario è stato 2 osservato per le microalghe della linea verde, che hanno una maggiore richiesta di nutrienti meno abbondanti in condizioni ossidate (N, Fe, Cu, Zn). Questo suggerirebbe che le alghe della linea rossa siano meglio dotate per far fronte alle condizioni chimiche degli oceani ricchi di ossigeno. Dato che gli organismi della stessa linea evolutiva condividono la stechiometria elementale e i percorsi metabolici, dovrebbero rispondere in maniera simile alla variazione di disponibilità di nutrienti, allocando il C nelle stesse categorie di composti. Le modalità di allocazione del C influiscono sulla biologia delle microalghe attraverso l’impatto che il contenuto energetico esercita sulla palatabilità della cellula e mediante l’effetto della densità cellulare complessiva sulle velocità di affondamento. I differenti composti organici in cui viene allocato il C (proteine, lipidi e carboidrati) non sono equivalenti in termini di densità e di richiesta di energia. Dunque, nella scala dei tempi geologici, le modalità di allocazione del C possono aver avuto un ruolo rilevante sulle traiettorie evolutive del fitoplancton. Può essere ipotizzato che, negli oceani ossigenati e permissivi dal punto di vista ecologico che emersero dall’estinzione di massa Permo-Triassica, le alghe della linea rossa si siano avvantaggiate delle modalità di allocazione del C che ne diminuirono la palatabilità e permisero loro un miglior controllo della galleggiabilità. Lo scopo di questa tesi è valutare l’impatto della variazione della disponibilità dei macro- e micro-nutrienti sulle traiettorie evolutive del fitoplancton. Al fine di perseguire questo scopo, ho pianificato quattro esperimenti per investigare il ruolo potenziale dei seguenti fattori: 3  Disponibilità di NO3-  Rapporto N:P  Disponibilità di SO42-  Disponibilità di Fe, Cu e Mn Il primo esperimento è stato condotto su dieci differenti specie di microalghe appartenenti alle linee evolutive verde e rossa (Amphidinium klebsii, Chlorella marina, Cyclotella meneghiniana, Dunaliella parva, Dunaliella salina, Phaeodactylum tricornutum, Skeletonema marinoi, Tetraselmis suecica, Thalassiosira pseudonana, Thalassiosira weissflogii) e su un cianobatterio (Synechococcus sp.), mentre, per gli altri esperimenti è stato selezionato un numero minore di specie. In parziale disaccordo con l’ipotesi, le modalità di allocazione del C e la loro variazione in risposta ai cambiamenti della disponibilità dei nutrienti (NO3-, SO42- e metalli) erano differenti in alghe che condividono le medesime traiettorie evolutive. Anche gli organismi appartenenti allo stesso genere (Dunaliella parva e Dunaliella salina, Thalassiosira pseudonana e Thalassiosira weissflogii) avevano diverse modalità di allocazione del C in risposta a differenti concentrazioni di NO3-. D’altra parte, le modalità di allocazione del C erano fortemente influenzate dalla taglia cellulare. Quando la biomassa è stata caratterizzata in termini di livello di riduzione complessivo, l’ipotesi è stata verificata, dato che le alghe appartenenti alle due linee evolutive erano marcatamente distinte. Le specie della linea rossa mostravano un livello di riduzione più basso in condizioni che mimano gli oceani attuali, mentre il contrario era vero per le alghe della linea verde. Il maggiore livello di riduzione delle alghe negli oceani attuali si può tradurre in un maggiore contenuto energetico e quindi in 4 una maggiore palatabilità delle cellule per i pascolatori. Questo può aver avuto un ruolo nel favorire l’ascesa alla dominanza delle alghe della linea rossa. Il tasso di crescita della diatomea Thalassiosira pseudonana è stato saturato a un N:P di 13, mentre il tasso di crescita delle alghe della linea verde Dunaliella salina è stato saturato a un N:P di 76. La diatomea non ha cambiato il tasso di assimilazione del NO3- in funzione del rapporto N:P. L’alga verde, invece, ha mostrato una maggiore sensibilità alla disponibilità di NO3- e ha cambiato in maniera apprezzabile il tasso di assimilazione del NO3- in risposta al rapporto N:P. La composizione organica di T. pseudonana è rimasta inalterata in un intervallo di N:P compreso tra 2.6 e 13; per valori di N:P superiori, la diatomea ha modificato la sua composizione e ha aumentato il costo di produzione della biomassa (entrambi sono rimasti costanti quando il rapporto N:P era tra 38 e 152). Dunaliella salina ha cambiato le modalità di allocazione del C in ogni condizione di coltura e ha diminuito il contenuto energetico delle cellule quando è stata coltivata a maggiori rapporti N:P. Dunque, la diatomea ha speso meno energia per produrre la sua biomassa in condizioni di disponibilità di N che mimavano quelle degli oceani moderni; l’alga verde, invece, ha speso meno energia quando è stata cresciuta in condizioni simili al Paleozoico. La disponibilità di SO42- ha influenzato i tassi di crescita delle diatomee P. tricornutum e T. pseudonana e dell’alga verde D. salina: quando queste specie sono state coltivate alla concentrazione di 28 mmol L-1 di SO42- (che 5 mima quella degli oceani attuali), i loro tassi di crescita erano più alti di quando sono state coltivate a una concentrazione di 3 mmol L-1 di SO42- (che mima quella degli oceani del Paleozoico). I tassi di crescita di T. suecica non sono stati interessati dalla disponibilità di SO42-. Nelle alghe verdi, l’efficienza di uso dell’N non è cambiata in funzione della disponibilità di SO42-, mentre quella delle diatomee era maggiore quando la concentrazione di SO42- era alta (28 mmol L-1). La produttività di C delle alghe verdi era più alta a basso SO42- (3 mmol L-1), ma era più bassa ad alto SO42-. Il contrario era vero per le due diatomee. In P. tricornutum e T. pseudonana, il tasso di sintesi delle proteine normalizzato per unità di RNA era considerevolmente maggiore a 28 mmol L-1 di SO42- piuttosto che a 3 mmol L-1 di SO42-. Questo non era vero per le alghe verdi, per le quali non è stato notato nessun cambiamento significativo di questo parametro in funzione delle concentrazioni di SO42-. Le due alghe verdi e le due diatomee usate nei precedenti esperimenti sono state coltivate anche in presenza di differenti concentrazioni di Fe, Cu e Mn. Secondo l’ipotesi che suggerisce che le alghe della linea rossa hanno una maggiore abilità a crescere in ambienti più ossidati, un aumento della disponibilità di Cu e una diminuzione della disponibilità di Fe e Mn dovrebbero favorire queste alghe su quelle della linea verde. I nostri risultati non sembrano confermare pienamente questa ipotesi, dato che le risposte in termini di crescita delle quattro specie alla disponibilità di questi metalli non sono coerentemente correlate alla linea evolutiva. Infatti, la maggior disponibilità di Cu ha stimolato la crescita di P. tricornutum e delle due alghe verdi, ma non di T. pseudonana; la maggior disponibilità di Fe non ha avuto effetto sulle diatomee, ma ha stimolato la crescita di D. salina; il Mn ha stimolato la crescita delle diatomee, ma non quella di D. salina e T. suecica. 6 In conclusione, gli esperimenti riassunti sopra mostrano che:  La diminuzione della disponibilità di NO3- nel corso della storia della terra può aver favorito le alghe della linea rossa  Il declino del rapporto N:P osservato attraverso il Mesozoico può aver avuto un impatto positivo sull’ascesa alla dominanza delle alghe della linea rossa  I cambiamenti secolari dell’abbondanza di SO42- sono compatibili con un ruolo di questo nutriente nell’aver facilitato la predominanza della linea rossa negli oceani moderni  Il cambiamento dello stato redox per se non ha avuto un impatto sull’evoluzione del fitoplancton.
Phytoplankton in the extant oceans is mainly dominated by microalgae of the red lineage, with chlorophyll a and c, whereas microalgae of the green lineage, with chlorophyll a and b, only contribute to a minor extent. However, the species composition of phytoplankton changed over geological time scale and microalgae of the green lineage dominated the oceans of the Paleozoic Era, whereas from the Mesozoic Era the red lineage rose to dominance and gave origin to the groups of algae that dominate the extant oceans. This shift in dominance of the phytoplankton has been put in relation with the change of ocean chemistry that occurred over a geological time scale. The oceanic concentration of SO42- increased monotonically from the Paleozoic Era (~1-10 mmol L-1 SO42-) to the present (28 mmol L-1 SO42-). Although it is difficult to have detailed information about the abundances of NO3- and PO4- in the oceans of the past, there are evidences that also the N:P ratios changed over geological time scale, and the oceans passed from P- to N-limitation, from the Paleozoic Era to date. Moreover, the change of the redox state of the oceans caused by the accumulation of the O2 released by photosynthesis from the Neo-Proterozoic to the end of the Paleozoic, determined a change in the abundance of some trace metals, such as Fe, Cu, Mn, Mo, Cd and Zn. It has been hypothesized that the link between the change of ocean chemistry and the evolutionary success of the microalgae of the red lineage is the average cell elemental stoichiometry. The microalgae of the red lineage have been reported to have higher requirement for those elements (S, P, Mn) whose availability increased when the oceans became more oxidized; the opposite was observed for microalgae of the green lineage, which have higher requirement for nutrients less abundant in oxidized conditions (N, Fe, Cu, Zn). This would suggest that the algae of the red lineage are better equipped to cope with the chemical conditions of oxygenated oceans. Because organisms of the same evolutionary lineage share elemental stoichiometry and biosynthetic pathways, they should respond similarly to the variation of nutrient availability, allocating C to the same pools. The pattern of C allocation affects the biology of microalgae through the impact that the energy content exerts on cell palatability and through the effect of the overall cell density on sinking rates. Different organic pools to which C is allocated (i.e. proteins, lipids and carbohydrates) are not equivalent in terms of density and energy requirement. Therefore, on a geological time scale, the patterns of C allocation may have had a relevant role on the evolutionary trajectories of phytoplankton. It can be hypothesized that, in the oxygenated and ecologically permissive oceans that emerged from the Permo-Triassic mass extintction, the algae of the red lineage took advantage of patterns of C allocation that decreased their palatability and allowed a better buoyancy control. The aim of this thesis is to evaluate the impact of the variation of macro- and micro-nutrients availability on the evolutionary trajectories of phytoplankton. In order to pursue this aim, I designed four experiments to investigate the potential role of the following:  Availability of NO3-;  N:P ratio;  Availability of SO42-;  Availability of Fe, Cu and Mn. The first experiment was conducted on ten different species of microalgae belonging to the green and to the red lineage (Amphidinium klebsii, Chlorella marina, Cyclotella meneghiniana, Dunaliella parva, Dunaliella salina, Phaeodactylum tricornutum, Skeletonema marinoi, Tetraselmis suecica, Thalassiosira pseudonana, Thalassiosira weissflogii) and one cyanobacterium (Synechococcus sp.), whereas, for the other experiments a smaller number of species was selected. In partial disagreement with the hypothesis, the patterns of C allocation and their variation in response to changes in the availability of nutrients (NO3-, SO42- and metals) were different in algae sharing the same evolutionary trajectories. Also organisms belonging to the same genus (i.e. Dunaliella parva and Dunliella salina, Thalassiosira pseudonana and Thalassiosira weissflogii) had different patterns of C allocation in response to different NO3- concentrations. On the other hand, the allocation patterns were strongly affected by the cell size. When biomass was characterized in terms of the overall level of reduction, the hypothesis was verified, since the algae belonging to the two evolutionary lineages were consistently distinct. The species of the red lineage showed a lower level of biomass reduction in conditions mimicking the extant oceans, whereas the opposite was true for algae of the green lineage. The higher level of reduction of the green algae in today’s oceans may also translate to a higher energy content and thus a higher palatability of cells to grazers. This may have played a role in favoring the rise to dominance of the algae of the red lineage. The growth rate of the diatom Thalassiosira pseudonana was saturated at a N:P of 13, whereas, the growth rate of the green alga Dunaliella salina was saturated at a N:P of 76. The diatom did not change the rate of assimilation of NO3- as a function of the N:P ratio. The green alga, instead, showed a greater sensitivity to the availability of NO3- and appreciably changed the rate of NO3-assimilation in response to the N:P ratio. The organic composition of T. pseudonana was unaltered in a range of N:P ratio between 2.6 and 13; above this N:P ratio, the diatom modified its composition and increased the cost of biomass production (both remained constant when the N:P ratio was between 38 and 152). Dunaliella salina changed the pattern of C allocation in each culture condition and tended to decrease the energy content of the cell when cultured at higher N:P ratios. Therefore, the diatom spent less energy to produce its biomass in conditions of N availability mimicking those of extant oceans; the green alga, instead, spent less energy when growth in Paleozoic-like conditions. The availability of SO42- affected the growth rates of the diatoms P. tricornutum and T. pseudonana and of the green alga D. salina: when these species were cultured at a SO42- concentration of 28 mmol L-1 (mimicking that of the extant oceans), their growth rates was higher than when they were cultured at a SO42- concentration of 3 mmol L-1 (mimicking that of the Paleozoic oceans). The growth rates of T. suecica was not affected by the availability of SO42-. In the green algae, The N-use efficiency did not change as a function of SO42- availability, whereas that of the diatoms was higher when SO42- concentration was high (28 mmol L-1). Green algae C productivity was higher at low SO42- (3 mmol L-1), but it was lower a high SO42-. The opposite was true for the two diatoms. In P. tricornutum and T. pseudonana, the rate of protein synthesis normalized on RNA amount was appreciably higher at 28 mmol L-1 SO42- than at 3 and 14 mmol L-1 SO42-. The same was not true for the green algae, for which no significant change of this parameter as a function of SO42- concentrations was detected. The two green algae and the two diatoms used in the previous experiment were also cultured in the presence of different Fe, Cu and Mn concentrations. According to the hypothesis that suggests a higher ability of algae of the red lineage to grow in more oxidized environments, an increased availability of Cu and a decreased availability of Fe and Mn should favor these algae over those of the green lineage. Our results do not appear to fully confirm this hypothesis, as the growth response of the four species to the availability of these metals is not consistently related to the evolutionary lineage. In fact, higher Cu availability stimulates the growth of P. tricornutum and of the two green algae, but not of T. pseudonana; higher Fe availability had no effect on the diatoms, but stimulated growth of D. salina; Mn stimulates diatoms growth, but not that of D. salina and T. suecica. In conclusions, the experiments summarized above show that:  The decrease of NO3- availability in the course of Earth history may have favored the algae of the red lineage  The observed decline of the N:P ratio in the oceans across the Mesozoic may also have had a positive impact on the rise to dominance of the algae of the red lineage.  The secular changes in sulfate are compatible with a role of this nutrient in facilitating the prevalence of the red lineage in modern oceans  The change of redox state per se did not impact the evolution of phytoplankton.

Les processus physiologiques déterminant la productivité forestière and l’allocation du carbone (C) entre les différents organes de l’arbre restent mal connus. La croissance forestière a longtemps été considérée comme limitée par le C, à travers un lien causal entre photosynthèse et croissance (contrôle de la croissance par la source de C). Ce paradigme C-centré est à l’origine des règles gouvernant l’allocation du C dans la plupart des modèles à base de processus (MBP). Cependant, le contrôle de la croissance forestière par la source de C a été remis en cause par un certain nombre d’études mettant en lumière que l’activité des méristèmes est plus sensible aux stress environnementaux (stress hydrique, température basse) que ne l’est l’assimilation du C (contrôle de la croissance par l’activité du puits). De plus, l’effet de la gestion, qui influe fortement sur le fonctionnement de la forêt and sa croissance, n’est pas pris en compte dans la plupart des MBP utilisés pour projeter le futur puits de C terrestre. Notre objectif principal dans cette thèse est d’améliorer notre connaissance des contraintes qui affectent - ou affecteront- la productivité ligneuse des forêts européennes, depuis l’époque actuelle jusqu’à la fin du 21ème siècle. Nous avons abordé cet objectif à travers l’amélioration du modèle CASTANEA, sur la base d’une analyse détaillée des déterminants de la productivité ligneuse annuelle des forêts françaises sur les 30 dernières années. Les espèces étudiées sont Fagus sylvatica, Quercus ilex, Quercus petraea, Quercus robur et Picea abies. Nos résultats suggèrent que la croissance annuelle des espèces étudiées est soumise à un contrôle complexe, impliquant des limitations par la source de C et par l’activité du puits. La variabilité inter-site de la fraction de C allouée à la croissance est principalement expliquée par un déclin lié à l’âge. La croissance annuelle à l’échelle de l’arbre est bien prédite par la taille des individus. Nous avons montré que l’asymétrie de la croissance, i.e., l’avantage des gros arbres dans la compétition pour les ressources, augmente avec la productivité, aux échelles inter-site et inter-annuelle. Sur la base de ces résultats, nous avons développé un nouveau schéma d’allocation du C dans le modèle CASTANEA. Le nouveau modèle a été capable de reproduire de manière satisfaisante la variabilité inter-annuelle et inter-site dans la croissance ligneuse aérienne le long de gradients environnementaux à l’échelle nationale. Le modèle a également été validé en utilisant une méta-analyse de mesure de réserves carbonées et des estimations satellitaires d’indices foliaires. Nos résultats indiquent que la représentation du contrôle de la croissance par l’activité du puits n’affecte pas les prédictions qualitatives de l’évolution de la productivité forestière européenne précédemment obtenues par les MBP C-centrés. Cependant, les MBP C-centrés sous-estiment certainement l’hétérogénéité spatiale des effets du changement climatique.Nous avons enfin utilisé notre nouvelle connaissance des déterminants de la croissance ligneuse annuelle à l’échelle de l’arbre (i.e., les règles empiriques de la compétition) pour calibrer un module simulant la croissance individuelle dans CASTANEA. Le modèle couplé a été utilisé pour évaluer l’effet potentiel de la gestion sur le fonctionnement des forêts et la croissance ligneuse à l’échelle de la France. Nous avons identifié les zones où la gestion pourrait être intensifiée pour réduire l’impact du changement climatique sur la productivité forestière nationale. Environ un quart des forêts françaises en hêtre et chênes tempérés sont en zone de forte vulnérabilité, zone dans laquelle la gestion pourrait donc être utilisée à profit pour limiter l’impact du changement climatique sur la récolte de bois
The processes that underlie forest productivity and C allocation dynamics in trees are still poorly understood. Forest growth has for long been thought to be C limited, through a hypothesized causal link between C supply and growth (source control). This C-centric paradigm underlies most of the C allocation rules formalized in process-based models (PBMs). However, the source limitation of growth has been questioned by several authors, arguing that meristem activities are more sensitive than C assimilation to environmental stresses (e.g., water deficit and low temperatures). Moreover, the effect of management, which strongly affects forest functioning and wood growth, is not accounted for in most of the PBMs used to project the future terrestrial C sink. Our main objective in this thesis was to move forward into our understanding of the constraints that affect - or will affect - the wood productivity in European forests, from present to the end of the 21 st century. We addressed this objective through the improvement of the representation of the forest productivity and C allocation in the CASTANEA PBM, building on a detailed analysis of the key drivers of annual wood productivity in French forests over the last 30 years (the species studied are Fagus sylvatica, Quercus ilex, Quercus petraea, Quercus robur and Picea abies). Our results supported the premise that the annual wood growth of the studied species is under a complex control including both source and sink limitations. The inter-site variability in the fraction of C allocatedto stand wood growth was predominantly driven by an age-related decline. At the tree level, we showed that annual wood growth was well predicted by the individual size. The size-asymmetry of growth, i.e., the advantage of big trees in the competition for resources, increased consistently with the whole stand productivity at both inter-site and inter-annual scales. On the basis of our findings, we developed a new C allocation scheme in the CASTANEA PBM, which integrate a combined source-sink limitation of wood growth. The new calibrated model captured both the inter-annual and inter-site changes in stand wood growth that was observed across national environmental gradients. The model was also successfully evaluated against a meta-analysis of carbohydrate reserve pools in trees and satellite-derived leaf area index estimates. Our results indicated that the representation of the environmental control of sink activity does not affect the qualitative predictions of the future of the European forest productivity previously obtained from source-driven PBMs. However, the current, source-driven generation of PBMs probably underestimates the spatial heterogeneity of the effects of climate change on forest growth that arise from sink limitations.Further, we successfully used our findings regarding the dependences of annual wood growth at tree level (i.e., empirical rules of tree growth competition) to calibrate a module for the simulation of the individual growth of trees in the CASTANEA model. The coupled model was used to assess the potential effects of management on forest functioning and wood growth across France. We identified the areas where management efforts may be concentrated in order to mitigate near-future drought impact on national forest productivity. Around a quarter of the French temperate oak and beech forests are currently in zones of high vulnerability, where management could thus mitigate the influence of climate change on forest yield

Ecologists traditionally regard time as part of the background against which ecological interactions play out. This book argues that time should be treated as a resource used by organisms for growth, maintenance, and offspring production. The book uses insights from phenology—the study of the timing of life-cycle events—to present a theoretical framework of time in ecology that casts long-standing observations in the field in an entirely new light. Combining conceptual models with field data, the book demonstrates how phenological advances, delays, and stasis, documented in an array of taxa, can all be viewed as adaptive components of an organism's strategic use of time. The book shows how the allocation of time by individual organisms to critical life history stages is not only a response to environmental cues but also an important driver of interactions at the population, species, and community levels. To demonstrate the applications of this exciting new conceptual framework, the book uses meta-analyses of previous studies as well as the author's original data on the phenological dynamics of plants, caribou, and muskoxen in Greenland.

The function of the 30-kilodalton movement protein (MP) of tobacco mosaic virus (TMV) is to facilitate cell-to-cell movement of viral progeny in infected plants. Our earlier findings have indicated that this protein has a direct effect on plasmodesmal function. In addition, these studies demonstrated that constitutive expression of the TMV MP gene (under the control of the CaMV 35S promoter) in transgenic tobacco plants significantly affects carbon metabolism in source leaves and alters the biomass distribution between the various plant organs. The long-term goal of the proposed research was to better understand the factors controlling carbon translocation in plants. The specific objectives were: A) To introduce into tobacco and potato plants a virally-encoded (TMV-MP) gene that affects plasmodesmal functioning and photosynthate partitioning under tissue-specific promoters. B) To introduce into tobacco and potato plants the TMV-MP gene under the control of promoters which are tightly repressed by the Tn10-encoded Tet repressor, to enable the expression of the protein by external application of tetracycline. C) To explore the mechanism by which the TMV-MP interacts with the endogenous control o~ carbon allocation. Data obtained in our previous project together with the results of this current study established that the TMV-MP has pleiotropic effects when expressed in transgenic tobacco plants. In addition to its ability to increase the plasmodesmal size exclusion limit, it alters carbohydrate metabolism in source leaves and dry matter partitioning between the various plant organs, Expression of the TMV-MP in various tissues of transgenic potato plants indicated that sugars and starch levels in source leaves are reduced below those of control plants when the TMV-MP is expressed in green tissue only. However, when the TMV-MP was expressed predominantly in PP and CC, sugar and starch levels were raised above those of control plants. Perhaps the most significant result obtained from experiments performed on transgenic potato plants was the discovery that the influence of the TMV-MP on carbohydrate allocation within source leaves was under developmental control and was exerted only during tuber development. The complexity of the mode by which the TMV-MP exerts its effect on the process of carbohydrate allocation was further demonstrated when transgenic tobacco plants were subjected to environmental stresses such as drought stress and nutrients deficiencies, Collectively, these studies indicated that the influence of the TMV-MP on carbon allocation L the result of protein-protein interaction within the source tissue. Based on these results, together with the findings that plasmodesmata potentiate the cell-to-cell trafficking of viral and endogenous proteins and nucleoproteins complexes, we developed the theme that at the whole plant level, the phloem serves as an information superhighway. Such a long-distance communication system may utilize a new class of signaling molecules (proteins and/or RNA) to co-ordinate photosynthesis and carbon/nitrogen metabolism in source leaves with the complex growth requirements of the plant under the prevailing environmental conditions. The discovery that expression of viral MP in plants can induce precise changes in carbon metabolism and photoassimilate allocation, now provide a conceptual foundation for future studies aimed at elucidating the communication network responsible for integrating photosynthetic productivity with resource allocation at the whole-plant level. Such information will surely provide an understanding of how plants coordinate the essential physiological functions performed by distantly-separated organs. Identification of the proteins involved in mediating and controlling cell-to-cell transport, especially at the companion cell-sieve element boundary, will provide an important first step towards achieving this goal.

Preventing the materialization of climate change is one of the main challenges of our time. The involvement of the financial sector is a fundamental pillar in this task, which has led to the emergence of a new field in the literature, climate finance. In turn, the use of Machine Learning (ML) as a tool to analyze climate finance is on the rise, due to the need to use big data to collect new climate-related information and model complex non-linear relationships. Considering the proliferation of articles in this field, and the potential for the use of ML, we propose a review of the academic literature to assess how ML is enabling climate finance to scale up. The main contribution of this paper is to provide a structure of application domains in a highly fragmented research field, aiming to spur further innovative work from ML experts. To pursue this objective, first we perform a systematic search of three scientific databases to assemble a corpus of relevant studies. Using topic modeling (Latent Dirichlet Allocation) we uncover representative thematic clusters. This allows us to statistically identify seven granular areas where ML is playing a significant role in climate finance literature: natural hazards, biodiversity, agricultural risk, carbon markets, energy economics, ESG factors & investing, and climate data. Second, we perform an analysis highlighting publication trends; and thirdly, we show a breakdown of ML methods applied by research area.

Various unicellular algae produce omega-3 (w3) very-long-chain polyunsaturated fatty acids (VLC-PUFA), which are rarely found in higher plants. In this research and other studies from our laboratories, it has been demonstrated that the marine unicellular alga Nannochloropsis (Eustigmatophyceae) can be used as a reliable and high quality source for the w3 VLC-PUFA eicosapentaenoic acid (EPA). This alga is widely used in mariculture systems as the primary component of the artificial food chain in fish larvae production, mainly due to its high EPA content. Furthermore, w3 fatty acids are essential for humans as dietary supplements and may have therapeutic benefits. The goal of this research proposal was to understand the physiological and biochemical mechanisms which regulate the synthesis and accumulation of glycerolipids enriched with w3 VLC-PUFA in Nannochloropsis. The results of our studies demonstrate various aspects of lipid synthesis and its regulation in the alga: 1. Variations in lipid class composition imposed by various environmental conditions were determined with special emphasis on the relative abundance of the molecular species of triacylglycerol (TAG) and monogalactosyl diacylglycerol (MGDG). 2. The relationships between the cellular content of major glycerolipids (TAG and MGDG) and the enzymes involved in their synthesis were studied. The results suggested the importance of UDP-galactose diacylglycerol galactosyl (UDGT) in regulation of the cellular level of MGDG. In a current effort we have purified UDGT several hundredfold from Nannochloropsis. It is our aim to purify this enzyme to near homogeneity and to produce antibodies against this enzyme in order to provide the tools for elucidation of the biochemical mechanisms that regulate this enzyme and carbon allocation into galactolipids. 3. Our in vitro and in vivo labeling studies indicated the possibility that phosphatidylcholine (PC) and phosphatidylethanolamine (PE) are associated with desaturation of the structural lipids, whereas shorter chain saturated fatty acids are more likely to be incorporated into TAG. 4. Isolation of several putative mutants of Nannochloropsis which appear to have different lipid and fatty acid compositions than the wild type; a mutant of a special importance that is devoid of EPA was fully characterized. In addition, we could demonstrate the feasibility of Nannochloropsis biomass production for aquaculture and human health: 1) We demonstrated in semi-industrial scale the feasibility of mass production of Nannochloropsis biomass in collaboration with the algae plant NBT in Eilat; 2) Nutritional studies verified the importance algal w3 fatty acids for the development of rats and demonstrated that Nannochloropsis biomass fed to pregnant and lactating rats can benefit their offspring.