Imperial College London

Professor Iain Colin Prentice

Faculty of Natural SciencesDepartment of Life Sciences (Silwood Park)

Chair in Biosphere and Climate Impacts
 
 
 
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Contact

 

+44 (0)20 7594 2354c.prentice

 
 
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Location

 

1.1Centre for Population BiologySilwood Park

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Summary

 

Publications

Publication Type
Year
to

351 results found

Lin Y-S, Medlyn BE, Duursma RA, Prentice IC, Wang H, Baig S, Eamus D, Resco de Dios V, Mitchell P, Ellsworth DS, Op de Beeck M, Wallin G, Uddling J, Tarvainen L, Linderson M-L, Cernusak LA, Nippert JB, Ocheltree T, Tissue DT, Martin-St Paul NK, Rogers A, Warren JM, De Angelis P, Hikosaka K, Han Q, Onoda Y, Gimeno TE, Barton CVM, Bennie J, Bonal D, Bosc A, Loew M, Macinins-Ng C, Rey A, Rowland L, Setterfield SA, Tausz-Posch S, Zaragoza-Castells J, Broadmeadow MSJ, Drake JE, Freeman M, Ghannoum O, Hutley LB, Kelly JW, Kikuzawa K, Kolari P, Koyama K, Limousin J-M, Meir P, Lola da Costa AC, Mikkelsen TN, Salinas N, Sun W, Wingate Let al., 2015, Optimal stomatal behaviour around the world, Nature Climate Change, Vol: 5, Pages: 459-464, ISSN: 1758-678X

Stomatal conductance (gs) is a key land-surface attribute as it links transpiration, the dominant component of global land evapotranspiration, and photosynthesis, the driving force of the global carbon cycle. Despite the pivotal role of gs in predictions of global water and carbon cycle changes, a global-scale database and an associated globally applicable model of gs that allow predictions of stomatal behaviour are lacking. Here, we present a database of globally distributed gs obtained in the field for a wide range of plant functional types (PFTs) and biomes. We find that stomatal behaviour differs among PFTs according to their marginal carbon cost of water use, as predicted by the theory underpinning the optimal stomatal model1 and the leaf and wood economics spectrum2,3. We also demonstrate a global relationship with climate. These findings provide a robust theoretical framework for understanding and predicting the behaviour of gs across biomes and across PFTs that can be applied to regional, continental and global-scale modelling of ecosystem productivity, energy balance and ecohydrological processes in a future changing climate.

Journal article

Atkin OK, Bloomfield KJ, Reich PB, Tjoelker MG, Asner GP, Bonal D, Boenisch G, Bradford MG, Cernusak LA, Cosio EG, Creek D, Crous KY, Domingues TF, Dukes JS, Egerton JJG, Evans JR, Farquhar GD, Fyllas NM, Gauthier PPG, Gloor E, Gimeno TE, Griffin KL, Guerrieri R, Heskel MA, Huntingford C, Ishida FY, Kattge J, Lambers H, Liddell MJ, Lloyd J, Lusk CH, Martin RE, Maksimov AP, Maximov TC, Malhi Y, Medlyn BE, Meir P, Mercado LM, Mirotchnick N, Ng D, Niinemets U, O'Sullivan OS, Phillips OL, Poorter L, Poot P, Prentice IC, Salinas N, Rowland LM, Ryan MG, Sitch S, Slot M, Smith NG, Turnbull MH, VanderWel MC, Valladares F, Veneklaas EJ, Weerasinghe LK, Wirth C, Wright IJ, Wythers KR, Xiang J, Xiang S, Zaragoza-Castells Jet al., 2015, Global variability in leaf respiration in relation to climate, plant functional types and leaf traits, New Phytologist, Vol: 206, Pages: 614-636, ISSN: 0028-646X

Leaf dark respiration (Rdark) is an important yet poorly quantified component of the global carbon cycle. Given this, we analyzed a new global database of Rdark and associated leaf traits.Data for 899 species were compiled from 100 sites (from the Arctic to the tropics). Several woody and nonwoody plant functional types (PFTs) were represented. Mixed‐effects models were used to disentangle sources of variation in Rdark.Area‐based Rdark at the prevailing average daily growth temperature (T) of each site increased only twofold from the Arctic to the tropics, despite a 20°C increase in growing T (8–28°C). By contrast, Rdark at a standard T (25°C, Rdark25) was threefold higher in the Arctic than in the tropics, and twofold higher at arid than at mesic sites. Species and PFTs at cold sites exhibited higher Rdark25 at a given photosynthetic capacity (Vcmax25) or leaf nitrogen concentration ([N]) than species at warmer sites. Rdark25 values at any given Vcmax25 or [N] were higher in herbs than in woody plants.The results highlight variation in Rdark among species and across global gradients in T and aridity. In addition to their ecological significance, the results provide a framework for improving representation of Rdark in terrestrial biosphere models (TBMs) and associated land‐surface components of Earth system models (ESMs).

Journal article

Ciais P, Zhu D, Peng S, Wang T, Krinner G, Zimov S, Tagliabre A, Cuntz M, Bopp L, Prentice Iet al., 2015, An attempt to quantify terrestrial carbon storage during the last glacial maximum and the implications for deglaciation CO2 changes., Deglacial Changes in Ocean Dynamics and Atmospheric CO2 Modern, Glacial, and Deglacial Carbon Transfer between Ocean, Atmosphere, and Land, ISSN: 0369-5034

Conference paper

Togashi HF, Prentice IC, Evans BJ, Forrester DI, Drake P, Feikema P, Brooksbank K, Eamus D, Taylor Det al., 2015, Morphological and moisture availability controls of the leaf area-to-sapwood area ratio: analysis of measurements on Australian trees, ECOLOGY AND EVOLUTION, Vol: 5, Pages: 1263-1270, ISSN: 2045-7758

The leaf area-to-sapwood area ratio (LA:SA) is a key plant trait that links photosynthesis to transpiration. The pipe model theory states that the sapwood cross-sectional area of a stem or branch at any point should scale isometrically with the area of leaves distal to that point. Optimization theory further suggests that LA:SA should decrease toward drier climates. Although acclimation of LA:SA to climate has been reported within species, much less is known about the scaling of this trait with climate among species. We compiled LA:SA measurements from 184 species of Australian evergreen angiosperm trees. The pipe model was broadly confirmed, based on measurements on branches and trunks of trees from one to 27 years old. Despite considerable scatter in LA:SA among species, quantile regression showed strong (0.2 < R1 < 0.65) positive relationships between two climatic moisture indices and the lowermost (5%) and uppermost (5–15%) quantiles of log LA:SA, suggesting that moisture availability constrains the envelope of minimum and maximum values of LA:SA typical for any given climate. Interspecific differences in plant hydraulic conductivity are probably responsible for the large scatter of values in the mid-quantile range and may be an important determinant of tree morphology.

Journal article

Meng T-T, Wang H, Harrison SP, Prentice IC, Ni J, Wang Get al., 2015, Responses of leaf traits to climatic gradients: adaptive variation versus compositional shifts, BIOGEOSCIENCES, Vol: 12, Pages: 5339-5352, ISSN: 1726-4170

Journal article

Dani KGS, Jamie IM, Prentice IC, Atwell BJet al., 2015, Species-specific photorespiratory rate, drought tolerance and isoprene emission rate in plants, PLANT SIGNALING & BEHAVIOR, Vol: 10, ISSN: 1559-2316

Journal article

Li G, Harrison SP, Prentice IC, Falster Det al., 2014, Simulation of tree-ring widths with a model for primary production, carbon allocation, and growth, Biogeosciences, Vol: 11, Pages: 6711-6724, ISSN: 1726-4170

We present a simple, generic model of annual tree growth, called "T". This model accepts input from a first-principles light-use efficiency model (the "P" model). The P model provides values for gross primary production (GPP) per unit of absorbed photosynthetically active radiation (PAR). Absorbed PAR is estimated from the current leaf area. GPP is allocated to foliage, transport tissue, and fine-root production and respiration in such a way as to satisfy well-understood dimensional and functional relationships. Our approach thereby integrates two modelling approaches separately developed in the global carbon-cycle and forest-science literature. The T model can represent both ontogenetic effects (the impact of ageing) and the effects of environmental variations and trends (climate and CO2) on growth. Driven by local climate records, the model was applied to simulate ring widths during the period 1958–2006 for multiple trees of Pinus koraiensis from the Changbai Mountains in northeastern China. Each tree was initialised at its actual diameter at the time when local climate records started. The model produces realistic simulations of the interannual variability in ring width for different age cohorts (young, mature, and old). Both the simulations and observations show a significant positive response of tree-ring width to growing-season total photosynthetically active radiation (PAR0) and the ratio of actual to potential evapotranspiration (α), and a significant negative response to mean annual temperature (MAT). The slopes of the simulated and observed relationships with PAR0 and α are similar; the negative response to MAT is underestimated by the model. Comparison of simulations with fixed and changing atmospheric CO2 concentration shows that CO2 fertilisation over the past 50 years is too small to be distinguished in the ring-width data, given ontogenetic trends and interannual variability in climate.

Journal article

Calvo MM, Prentice IC, Harrison SP, 2014, Climate versus carbon dioxide controls on biomass burning: a model analysis of the glacial-interglacial contrast, Biogeosciences, Vol: 11, Pages: 6017-6027, ISSN: 1726-4189

Climate controls fire regimes through its influence on the amount and types of fuel present and their dryness. CO2 concentration constrains primary production by limiting photosynthetic activity in plants. However, although fuel accumulation depends on biomass production, and hence on CO2 concentration, the quantitative relationship between atmospheric CO2 concentration and biomass burning is not well understood. Here a fire-enabled dynamic global vegetation model (the Land surface Processes and eXchanges model, LPX) is used to attribute glacial–interglacial changes in biomass burning to an increase in CO2, which would be expected to increase primary production and therefore fuel loads even in the absence of climate change, vs. climate change effects. Four general circulation models provided last glacial maximum (LGM) climate anomalies – that is, differences from the pre-industrial (PI) control climate – from the Palaeoclimate Modelling Intercomparison Project Phase~2, allowing the construction of four scenarios for LGM climate. Modelled carbon fluxes from biomass burning were corrected for the model's observed prediction biases in contemporary regional average values for biomes. With LGM climate and low CO2 (185 ppm) effects included, the modelled global flux at the LGM was in the range of 1.0–1.4 Pg C year-1, about a third less than that modelled for PI time. LGM climate with pre-industrial CO2 (280 ppm) yielded unrealistic results, with global biomass burning fluxes similar to or even greater than in the pre-industrial climate. It is inferred that a substantial part of the increase in biomass burning after the LGM must be attributed to the effect of increasing CO2 concentration on primary production and fuel load. Today, by analogy, both rising CO2 and global warming must be considered as risk factors for increasing biomass burning. Both effects need to be included in models to project future fire risks.

Journal article

Wang H, Prentice I C, Davis TW, 2014, Biophysical constraints on gross primary production by the terrestrial biosphere, Biogeosciences, Vol: 11, Pages: 5987-6001, ISSN: 1726-4189

Persistent divergences among the predictions of complex carbon-cycle models include differences in the sign as well as the magnitude of the response of global terrestrial primary production to climate change. Such problems with current models indicate an urgent need to reassess the principles underlying the environmental controls of primary production. The global patterns of annual and maximum monthly terrestrial gross primary production (GPP) by C3 plants are explored here using a simple first-principles model based on the light-use efficiency formalism and the Farquhar model for C3 photosynthesis. The model is driven by incident photosynthetically active radiation (PAR) and remotely sensed green-vegetation cover, with additional constraints imposed by low-temperature inhibition and CO2 limitation. The ratio of leaf-internal to ambient CO2 concentration in the model responds to growing-season mean temperature, atmospheric dryness (indexed by the cumulative water deficit, Δ E) and elevation, based on an optimality theory. The greatest annual GPP is predicted for tropical moist forests, but the maximum (summer) monthly GPP can be as high, or higher, in boreal or temperate forests. These findings are supported by a new analysis of CO2 flux measurements. The explanation is simply based on the seasonal and latitudinal distribution of PAR combined with the physiology of photosynthesis. By successively imposing biophysical constraints, it is shown that partial vegetation cover – driven primarily by water shortage – represents the largest constraint on global GPP.

Journal article

Wang H, Prentice IC, Davis TW, 2014, Biophysical constraints on gross primary production by the terrestrial biosphere, Biogeosciences, Vol: 11, Pages: 5987-6001, ISSN: 1726-4170

Persistent divergences among the predictions of complex carbon-cycle models include differences in the sign as well as the magnitude of the response of global terrestrial primary production to climate change. Such problems with current models indicate an urgent need to reassess the principles underlying the environmental controls of primary production. The global patterns of annual and maximum monthly terrestrial gross primary production (GPP) by C3 plants are explored here using a simple first-principles model based on the light-use efficiency formalism and the Farquhar model for C3 photosynthesis. The model is driven by incident photosynthetically active radiation (PAR) and remotely sensed green-vegetation cover, with additional constraints imposed by low-temperature inhibition and CO2 limitation. The ratio of leaf-internal to ambient CO2 concentration in the model responds to growing-season mean temperature, atmospheric dryness (indexed by the cumulative water deficit, Δ E) and elevation, based on an optimality theory. The greatest annual GPP is predicted for tropical moist forests, but the maximum (summer) monthly GPP can be as high, or higher, in boreal or temperate forests. These findings are supported by a new analysis of CO2 flux measurements. The explanation is simply based on the seasonal and latitudinal distribution of PAR combined with the physiology of photosynthesis. By successively imposing biophysical constraints, it is shown that partial vegetation cover – driven primarily by water shortage – represents the largest constraint on global GPP.

Journal article

Kelley DI, Harrison SP, Prentice IC, 2014, Improved simulation of fire-vegetation interactions in the Land surface Processes and eXchanges dynamic global vegetation model (LPX-Mv1), Geoscientific Model Development, Vol: 7, Pages: 2411-2433, ISSN: 1991-959X

The Land surface Processes and eXchanges (LPX) model is a fire-enabled dynamic global vegetation model that performs well globally but has problems representing fire regimes and vegetative mix in savannas. Here we focus on improving the fire module. To improve the representation of ignitions, we introduced a reatment of lightning that allows the fraction of ground strikes to vary spatially and seasonally, realistically partitions strike distribution between wet and dry days, and varies the number of dry days with strikes. Fuel availability and moisture content were improved by implementing decomposition rates specific to individual plant functional types and litter classes, and litter drying rates driven by atmospheric water content. To improve water extraction by grasses, we use realistic plant-specific treatments of deep roots. To improve fire responses, we introduced adaptive bark thickness and post-fire resprouting for tropical and temperate broadleaf trees. All improvements are based on extensive analyses of relevant observational data sets. We test model performance for Australia, first evaluating parameterisations separately and then measuring overall behaviour against standard benchmarks. Changes to the lightning parameterisation produce a more realistic simulation of fires in southeastern and central Australia. Implementation of PFT-specific decomposition rates enhances performance in central Australia. Changes in fuel drying improve fire in northern Australia, while changes in rooting depth produce a more realistic simulation of fuel availability and structure in central and northern Australia. The introduction of adaptive bark thickness and resprouting produces more realistic fire regimes in Australian savannas. We also show that the model simulates biomass recovery rates consistent with observations from several different regions of the world characterised by resprouting vegetation. The new model (LPX-Mv1) produces an improved simulation of observed vege

Journal article

Dani KGS, Jamie IM, Prentice IC, Atwell BJet al., 2014, Increased Ratio of Electron Transport to Net Assimilation Rate Supports Elevated Isoprenoid Emission Rate in Eucalypts under Drought, PLANT PHYSIOLOGY, Vol: 166, Pages: 1059-1072, ISSN: 0032-0889

Journal article

Zhou S, Medlyn B, Sabate S, Sperlich D, Prentice ICet al., 2014, Short-term water stress impacts on stomatal, mesophyll and biochemical limitations to photosynthesis differ consistently among tree species from contrasting climates, Tree Physiology, Vol: 34, Pages: 1035-1046, ISSN: 1758-4469

Predicting the large-scale consequences of drought in contrasting environments requires that we understand how drought effects differ among species originating from those environments. A previous meta-analysis of published experiments suggested that the effects of drought on both stomatal and non-stomatal limitations to photosynthesis may vary consistently among species from different hydroclimates. Here, we explicitly tested this hypothesis with two short-term water stress experiments on congeneric mesic and xeric species. One experiment was run in Australia using Eucalyptus species and the second was run in Spain using Quercus species as well as two more mesic species. In each experiment, plants were grown under moist conditions in a glasshouse, then deprived of water, and gas exchange was monitored. The stomatal response was analysed with a recently developed stomatal model, whose single parameter g1 represents the slope of the relationship between stomatal conductance and photosynthesis. The non-stomatal response was partitioned into effects on mesophyll conductance (gm), the maximum Rubisco activity (Vcmax) and the maximum electron transport rate (Jmax). We found consistency among the drought responses of g1, gm, Vcmax and Jmax, suggesting that drought imposes limitations on Rubisco activity and RuBP regeneration capacity concurrently with declines in stomatal and mesophyll conductance. Within each experiment, the more xeric species showed relatively high g1 under moist conditions, low drought sensitivity of g1, gm, Vcmax and Jmax, and more negative values of the critical pre-dawn water potential at which Vcmax declines most steeply, compared with the more mesic species. These results indicate adaptive interspecific differences in drought responses that allow xeric tree species to continue transpiration and photosynthesis for longer during periods without rain.

Journal article

Bistinas I, Harrison SP, Prentice IC, Pereira JMCet al., 2014, Causal relationships versus emergent patterns in the global controls of fire frequency, Biogeosciences, Vol: 11, Pages: 5087-5101, ISSN: 1726-4170

Global controls on month-by-month fractional burnt area (2000–2005) were investigated by fitting a generalised linear model (GLM) to Global Fire Emissions Database (GFED) data, with 11 predictor variables representing vegetation, climate, land use and potential ignition sources. Burnt area is shown to increase with annual net primary production (NPP), number of dry days, maximum temperature, grazing-land area, grass/shrub cover and diurnal temperature range, and to decrease with soil moisture, cropland area and population density. Lightning showed an apparent (weak) negative influence, but this disappeared when pure seasonal-cycle effects were taken into account. The model predicts observed geographic and seasonal patterns, as well as the emergent relationships seen when burnt area is plotted against each variable separately. Unimodal relationships with mean annual temperature and precipitation, population density and gross domestic product (GDP) are reproduced too, and are thus shown to be secondary consequences of correlations between different controls (e.g. high NPP with high precipitation; low NPP with low population density and GDP). These findings have major implications for the design of global fire models, as several assumptions in current models – most notably, the widely assumed dependence of fire frequency on ignition rates – are evidently incorrect.

Journal article

Harrison SP, Bartlein PJ, Brewer S, Prentice IC, Boyd M, Hessler I, Holmgren K, Izumi K, Willis Ket al., 2014, Climate model benchmarking with glacial and mid-Holocene climates, CLIMATE DYNAMICS, Vol: 43, Pages: 671-688, ISSN: 0930-7575

Journal article

Morfopoulos C, Sperlich D, Penuelas J, Filella I, Llusia J, Medlyn BE, Niinemets U, Possell M, Sun Z, Prentice ICet al., 2014, A model of plant isoprene emission based on available reducing power captures responses to atmospheric CO2, New Phytologist, Vol: 203, Pages: 125-139, ISSN: 0028-646X

We present a unifying model for isoprene emission by photosynthesizing leaves based on the hypothesis that isoprene biosynthesis depends on a balance between the supply of photosynthetic reducing power and the demands of carbon fixation.We compared the predictions from our model, as well as from two other widely used models, with measurements of isoprene emission from leaves of Populus nigra and hybrid aspen (Populus tremula × P. tremuloides) in response to changes in leaf internal CO2 concentration (Ci) and photosynthetic photon flux density (PPFD) under diverse ambient CO2 concentrations (Ca).Our model reproduces the observed changes in isoprene emissions with Ci and PPFD, and also reproduces the tendency for the fraction of fixed carbon allocated to isoprene to increase with increasing PPFD. It also provides a simple mechanism for the previously unexplained decrease in the quantum efficiency of isoprene emission with increasing Ca.Experimental and modelled results support our hypothesis. Our model can reproduce the key features of the observations and has the potential to improve process‐based modelling of isoprene emissions by land vegetation at the ecosystem and global scales.

Journal article

Dani KGS, Jamie IM, Prentice IC, Atwell BJet al., 2014, Evolution of isoprene emission capacity in plants, TRENDS IN PLANT SCIENCE, Vol: 19, Pages: 439-446, ISSN: 1360-1385

Journal article

Foster PN, Prentice IC, Morfopoulos C, Siddall M, van Weele Met al., 2014, Isoprene emissions track the seasonal cycle of canopy temperature, not primary production: evidence from remote sensing, Biogeosciences, Vol: 11, Pages: 3437-3451, ISSN: 1726-4170

Isoprene is important in atmospheric chemistry, but its seasonal emission pattern – especially in the tropics, where most isoprene is emitted – is incompletely understood. We set out to discover generalized relationships applicable across many biomes between large-scale isoprene emission and a series of potential predictor variables, including both observed and model-estimated variables related to gross primary production (GPP) and canopy temperature. We used remotely sensed atmospheric concentrations of formaldehyde, an intermediate oxidation product of isoprene, as a proxy for isoprene emission in 22 regions selected to span high to low latitudes, to sample major biomes, and to minimize interference from pyrogenic sources of volatile organic compounds that could interfere with the isoprene signal. Formaldehyde concentrations showed the highest average seasonal correlations with remotely sensed (r = 0.85) and model-estimated (r = 0.80) canopy temperatures. Both variables predicted formaldehyde concentrations better than air temperature (r= 0.56) and a "reference" isoprene model that combines GPP and an exponential function of temperature (r = 0.49), and far better than either remotely sensed green vegetation cover, fPAR (r = 0.25) or model-estimated GPP (r = 0.14). Gross primary production in tropical regions was anti-correlated with formaldehyde concentration (r = −0.30), which peaks during the dry season. Our results were most reliable in the tropics, where formaldehyde observational errors were the least. The tropics are of particular interest because they are the greatest source of isoprene emission as well as the region where previous modelling attempts have been least successful. We conjecture that positive correlations of isoprene emission with GPP and air temperature (as found in temperate forests) may arise simply because both covary with canopy temperature, peaking during the relatively short growing season. The lack of a gener

Journal article

De Kauwe MG, Medlyn BE, Zaehle S, Walker AP, Dietze MC, Wang Y-P, Luo Y, Jain AK, El-Masri B, Hickler T, Warlind D, Weng E, Parton WJ, Thornton PE, Wang S, Prentice IC, Asao S, Smith B, McCarthy HR, Iversen CM, Hanson PJ, Warren JM, Oren R, Norby RJet al., 2014, Where does the carbon go? A model-data intercomparison of vegetation carbon allocation and turnover processes at two temperate forest free-air CO2 enrichment sites, NEW PHYTOLOGIST, Vol: 203, Pages: 883-899, ISSN: 0028-646X

Elevated atmospheric CO2concentration (eCO2) has the potential to increase vegetationcarbon storage if increased net primary production causes increased long-lived biomass.Model predictions of eCO2effects on vegetation carbon storage depend on how allocationand turnover processes are represented. We used data from two temperate forest free-air CO2enrichment (FACE) experiments toevaluate representations of allocation and turnover in 11 ecosystem models. Observed eCO2effects on allocation were dynamic. Allocation schemes based on func-tional relationships among biomass fractions that vary with resource availability were best ableto capture the general features of the observations. Allocation schemes based on constantfractions or resource limitations performed less well, with some models having unintendedoutcomes. Few models represent turnover processes mechanistically and there was wide vari-ation in predictions of tissue lifespan. Consequently, models did not perform well at predictingeCO2effects on vegetation carbon storage. Our recommendations to reduce uncertainty include: use of allocation schemes constrainedby biomass fractions; careful testing of allocation schemes; and synthesis of allocation andturnover data in terms of model parameters. Data from intensively studied ecosystem manip-ulation experiments are invaluable for constraining models and we recommend that suchexperiments should attempt to fully quantify carbon, water and nutrient budgets.

Journal article

Zaehle S, Medlyn BE, De Kauwe MG, Walker AP, Dietze MC, Hickler T, Luo Y, Wang Y-P, El-Masri B, Thornton P, Jain A, Wang S, Warlind D, Weng E, Parton W, Iversen CM, Gallet-Budynek A, McCarthy H, Finzi AC, Hanson PJ, Prentice IC, Oren R, Norby RJet al., 2014, Evaluation of 11 terrestrial carbon-nitrogen cycle models against observations from two temperate Free-Air CO2 Enrichment studies, NEW PHYTOLOGIST, Vol: 202, Pages: 803-822, ISSN: 0028-646X

Journal article

Walker AP, Hanson PJ, De Kauwe MG, Medlyn BE, Zaehle S, Asao S, Dietze M, Hickler T, Huntingford C, Iversen CM, Jain A, Lomas M, Luo Y, McCarthy H, Parton WJ, Prentice IC, Thornton PE, Wang S, Wang Y-P, Warlind D, Weng E, Warren JM, Woodward FI, Oren R, Norby RJet al., 2014, Comprehensive ecosystem model-data synthesis using multiple data sets at two temperate forest free-air CO2 enrichment experiments: Model performance at ambient CO2 concentration, Journal of Geophysical Research: Biogeosciences, Vol: 119, Pages: 937-964, ISSN: 2169-8961

Free‐air CO2 enrichment (FACE) experiments provide a remarkable wealth of data which can be used to evaluate and improve terrestrial ecosystem models (TEMs). In the FACE model‐data synthesis project, 11 TEMs were applied to two decadelong FACE experiments in temperate forests of the southeastern U.S.—the evergreen Duke Forest and the deciduous Oak Ridge Forest. In this baseline paper, we demonstrate our approach to model‐data synthesis by evaluating the models' ability to reproduce observed net primary productivity (NPP), transpiration, and leaf area index (LAI) in ambient CO2 treatments. Model outputs were compared against observations using a range of goodness‐of‐fit statistics. Many models simulated annual NPP and transpiration within observed uncertainty. We demonstrate, however, that high goodness‐of‐fit values do not necessarily indicate a successful model, because simulation accuracy may be achieved through compensating biases in component variables. For example, transpiration accuracy was sometimes achieved with compensating biases in leaf area index and transpiration per unit leaf area. Our approach to model‐data synthesis therefore goes beyond goodness‐of‐fit to investigate the success of alternative representations of component processes. Here we demonstrate this approach by comparing competing model hypotheses determining peak LAI. Of three alternative hypotheses—(1) optimization to maximize carbon export, (2) increasing specific leaf area with canopy depth, and (3) the pipe model—the pipe model produced peak LAI closest to the observations. This example illustrates how data sets from intensive field experiments such as FACE can be used to reduce model uncertainty despite compensating biases by evaluating individual model assumptions.

Journal article

Prentice IC, Dong N, Gleason SM, Maire V, Wright IJet al., 2013, Balancing the costs of carbon gain and water transport: testing a new theoretical framework for plant functional ecology, Ecology Letters, Vol: 17, Pages: 82-91, ISSN: 1461-023X

A novel framework is presented for the analysis of ecophysiological field measurements and modelling. The hypothesis ‘leaves minimise the summed unit costs of transpiration and carboxylation’ predicts leaf‐internal/ambient CO2 ratios (ci/ca) and slopes of maximum carboxylation rate (Vcmax) or leaf nitrogen (Narea) vs. stomatal conductance. Analysis of data on woody species from contrasting climates (cold‐hot, dry‐wet) yielded steeper slopes and lower mean ci/ca ratios at the dry or cold sites than at the wet or hot sites. High atmospheric vapour pressure deficit implies low ci/ca in dry climates. High water viscosity (more costly transport) and low photorespiration (less costly photosynthesis) imply low ci/ca in cold climates. Observed site‐mean ci/ca shifts are predicted quantitatively for temperature contrasts (by photorespiration plus viscosity effects) and approximately for aridity contrasts. The theory explains the dependency of ci/ca ratios on temperature and vapour pressure deficit, and observed relationships of leaf δ13C and Narea to aridity.

Journal article

Bistinas I, Oom D, Sa ACL, Harrison SP, Prentice IC, Pereira JMCet al., 2013, Relationships between Human Population Density and Burned Area at Continental and Global Scales, PLOS ONE, Vol: 8, ISSN: 1932-6203

We explore the large spatial variation in the relationship between population density and burned area, usingcontinental-scale Geographically Weighted Regression (GWR) based on 13 years of satellite-derived burned areamaps from the global fire emissions database (GFED) and the human population density from the gridded populationof the world (GPW 2005). Significant relationships are observed over 51.5% of the global land area, and the areaaffected varies from continent to continent: population density has a significant impact on fire over most of Asia andAfrica but is important in explaining fire over < 22% of Europe and Australia. Increasing population density isassociated with both increased and decreased in fire. The nature of the relationship depends on land-use: increasingpopulation density is associated with increased burned are in rangelands but with decreased burned area incroplands. Overall, the relationship between population density and burned area is non-monotonic: burned areainitially increases with population density and then decreases when population density exceeds a threshold. Thesethresholds vary regionally. Our study contributes to improved understanding of how human activities relate to burnedarea, and should contribute to a better estimate of atmospheric emissions from biomass burning.

Journal article

Medlyn BE, Duursma RA, De Kauwe MG, Prentice ICet al., 2013, The optimal stomatal response to atmospheric CO2 concentration: Alternative solutions, alternative interpretations, AGRICULTURAL AND FOREST METEOROLOGY, Vol: 182, Pages: 200-203, ISSN: 0168-1923

Journal article

Zhou S, Duursma RA, Medlyn BE, Kelly JWG, Prentice ICet al., 2013, How should we model plant responses to drought? An analysis of stomatal and non-stomatal responses to water stress, AGRICULTURAL AND FOREST METEOROLOGY, Vol: 182, Pages: 204-214, ISSN: 0168-1923

Journal article

Morfopoulos C, Prentice IC, Keenan TF, Friedlingstein P, Medlyn BE, Penuelas J, Possell Met al., 2013, A unifying conceptual model for the environmental responses of isoprene emissions from plants, ANNALS OF BOTANY, Vol: 112, Pages: 1223-1238, ISSN: 0305-7364

Background and AimsIsoprene is the most important volatile organic compound emitted by land plants in terms ofabundance and environmental effects. Controls on isoprene emission rates include light, temperature, water supplyand CO2concentration. A need to quantify these controls has long been recognized. There are already models thatgive realistic results, but they are complex, highly empirical and require separate responses to different drivers.This study sets out to find a simpler, unifying principle.†MethodsA simple model is presented based on the idea of balancing demands for reducing power (derived fromphotosynthetic electron transport) in primary metabolism versus the secondary pathway that leads to the synthesisof isoprene. This model’s ability to account for key features in a variety of experimental data sets is assessed.†Key resultsThe model simultaneously predicts the fundamental responses observed in short-term experiments,namely: (1) the decoupling between carbon assimilation and isoprene emission; (2) a continued increase in isopreneemission with photosynthetically active radiation (PAR) at high PAR, after carbon assimilation has saturated; (3) amaximum of isoprene emission at low internal CO2concentration (ci) and an asymptotic decline thereafter with in-creasingci; (4) maintenance of high isoprene emissions when carbon assimilation is restricted by drought; and (5) atemperature optimum higher than that of photosynthesis, but lower than that of isoprene synthase activity.†ConclusionsA simple model was used to test the hypothesisthat reducing poweravailable to the synthesis pathwayfor isoprene varies according to the extent to which the needs of carbon assimilation are satisfied. Despite its simpli-city the model explains much in terms of the observed response of isoprene to external drivers as well asthe observeddecoupling between carbon assimilation and isoprene emission. The concept has the potential to improve global-scale

Journal article

Mackey B, Prentice IC, Steffen W, House JI, Keith DLH, Berry Set al., 2013, Untangling the confusion around land carbon science and climate change mitigation policy (vol 3, pg 552, 2013), NATURE CLIMATE CHANGE, Vol: 3, Pages: 847-847, ISSN: 1758-678X

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Li G, Harrison SP, Bartlein PJ, Izumi K, Prentice ICet al., 2013, Precipitation scaling with temperature in warm and cold climates: An analysis of CMIP5 simulations, GEOPHYSICAL RESEARCH LETTERS, Vol: 40, Pages: 4018-4024, ISSN: 0094-8276

Journal article

Stocker BD, Roth R, Joos F, Spahni R, Steinacher M, Zaehle S, Bouwman L, Xu-Ri, Prentice ICet al., 2013, Multiple greenhouse-gas feedbacks from the land biosphere under future climate change scenarios, NATURE CLIMATE CHANGE, Vol: 3, Pages: 666-672, ISSN: 1758-678X

Journal article

Mackey B, Prentice IC, Steffen W, House JI, Lindenmayer D, Keith H, Berry Set al., 2013, Untangling the confusion around land carbon science and climate change mitigation policy, NATURE CLIMATE CHANGE, Vol: 3, Pages: 552-557, ISSN: 1758-678X

Journal article

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