Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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A methodology to derive global maps of leaf traits using remote sensing and climate data
Moreno-Martínez, Álvaro ; Camps-Valls, Gustau ; Kattge, Jens ; Robinson, Nathaniel ; Reichstein, Markus ; Bodegom, Peter van; Kramer, Koen ; Cornelissen, J.H.C. ; Reich, Peter ; Bahn, Michael ; Niinemets, Ülo ; Peñuelas, Josep ; Craine, Joseph M. ; Cerabolini, Bruno E.L. ; Minden, Vanessa ; Laughlin, Daniel C. ; Sack, Lawren ; Allred, Brady ; Baraloto, Christopher ; Byun, Chaeho ; Soudzilovskaia, Nadejda A. ; Running, Steve W. - \ 2018
Remote Sensing of Environment 218 (2018). - ISSN 0034-4257 - p. 69 - 88.
Climate - Landsat - Machine learning - MODIS - Plant ecology - Plant traits - Random forests - Remote sensing

This paper introduces a modular processing chain to derive global high-resolution maps of leaf traits. In particular, we present global maps at 500 m resolution of specific leaf area, leaf dry matter content, leaf nitrogen and phosphorus content per dry mass, and leaf nitrogen/phosphorus ratio. The processing chain exploits machine learning techniques along with optical remote sensing data (MODIS/Landsat) and climate data for gap filling and up-scaling of in-situ measured leaf traits. The chain first uses random forests regression with surrogates to fill gaps in the database (> 45% of missing entries) and maximizes the global representativeness of the trait dataset. Plant species are then aggregated to Plant Functional Types (PFTs). Next, the spatial abundance of PFTs at MODIS resolution (500 m) is calculated using Landsat data (30 m). Based on these PFT abundances, representative trait values are calculated for MODIS pixels with nearby trait data. Finally, different regression algorithms are applied to globally predict trait estimates from these MODIS pixels using remote sensing and climate data. The methods were compared in terms of precision, robustness and efficiency. The best model (random forests regression) shows good precision (normalized RMSE≤ 20%) and goodness of fit (averaged Pearson's correlation R = 0.78) in any considered trait. Along with the estimated global maps of leaf traits, we provide associated uncertainty estimates derived from the regression models. The process chain is modular, and can easily accommodate new traits, data streams (traits databases and remote sensing data), and methods. The machine learning techniques applied allow attribution of information gain to data input and thus provide the opportunity to understand trait-environment relationships at the plant and ecosystem scales. The new data products – the gap-filled trait matrix, a global map of PFT abundance per MODIS gridcells and the high-resolution global leaf trait maps – are complementary to existing large-scale observations of the land surface and we therefore anticipate substantial contributions to advances in quantifying, understanding and prediction of the Earth system.

Mapping local and global variability in plant trait distributions
Butler, Ethan E. ; Datta, Abhirup ; Flores-Moreno, Habacuc ; Chen, Ming ; Wythers, Kirk R. ; Fazayeli, Farideh ; Banerjee, Arindam ; Atkin, Owen K. ; Kattge, Jens ; Amiaud, Bernard ; Blonder, Benjamin ; Boenisch, Gerhard ; Bond-Lamberty, Ben ; Brown, Kerry A. ; Byun, Chaeho ; Campetella, Giandiego ; Cerabolini, Bruno E.L. ; Cornelissen, Johannes H.C. ; Craine, Joseph M. ; Craven, Dylan ; Vries, Franciska T. De; Díaz, Sandra ; Domingues, Tomas F. ; Forey, Estelle ; González-Melo, Andrés ; Gross, Nicolas ; Han, Wenxuan ; Hattingh, Wesley N. ; Hickler, Thomas ; Jansen, Steven ; Kramer, Koen ; Kraft, Nathan J.B. ; Kurokawa, Hiroko ; Laughlin, Daniel C. ; Meir, Patrick ; Minden, Vanessa ; Niinemets, Ülo ; Onoda, Yusuke ; Peñuelas, Josep ; Read, Quentin ; Sack, Lawren ; Schamp, Brandon ; Soudzilovskaia, Nadejda A. ; Spasojevic, Marko J. ; Sosinski, Enio ; Thornton, Peter E. ; Valladares, Fernando ; Bodegom, Peter M. Van; Williams, Mathew ; Wirth, Christian ; Reich, Peter B. ; Schlesinger, William H. - \ 2017
Proceedings of the National Academy of Sciences of the United States of America 114 (2017)51. - ISSN 0027-8424 - p. E10937 - E10946.
Bayesian modeling - Climate - Global - Plant traits - Spatial statistics
Our ability to understand and predict the response of ecosystems to a changing environment depends on quantifying vegetation functional diversity. However, representing this diversity at the global scale is challenging. Typically, in Earth system models, characterization of plant diversity has been limited to grouping related species into plant functional types (PFTs), with all trait variation in a PFT collapsed into a single mean value that is applied globally. Using the largest global plant trait database and state of the art Bayesian modeling, we created fine-grained global maps of plant trait distributions that can be applied to Earth system models. Focusing on a set of plant traits closely coupled to photosynthesis and foliar respiration - specific leaf area (SLA) and dry mass-based concentrations of leaf nitrogen (Nm) and phosphorus (Pm), we characterize how traits vary within and among over 50,000 ∼50×50-km cells across the entire vegetated land surface. We do this in several ways - without defining the PFT of each grid cell and using 4 or 14 PFTs; each model's predictions are evaluated against out-of-sample data. This endeavor advances prior trait mapping by generating global maps that preserve variability across scales by using modern Bayesian spatial statistical modeling in combination with a database over three times larger than that in previous analyses. Our maps reveal that the most diverse grid cells possess trait variability close to the range of global PFT means.
Predicting habitat affinities of plant species using commonly measured functional traits
Shipley, B. ; Belluau, M. ; Kuhn, I. ; Soudzilovskaia, N.A. ; Bahn, M. ; Penuelas, J. ; Kattge, J. ; Sack, L. ; Cavender-Bares, J. ; Ozinga, W.A. ; Blonders, B. ; Bodegom, P.M. van; Manning, P. ; Hickler, T. ; Sosinski, E. ; Pillar, V.D. ; Onipchenko, V.G. ; Poschlod, P. - \ 2017
Journal of Vegetation Science 28 (2017)5. - ISSN 1100-9233 - p. 1082 - 1095.
Questions Heinz Ellenberg classically defined “indicator” scores for species representing their typical positions along gradients of key environmental variables, and these have proven very useful for designating ecological distributions. We tested a key tenent of trait-based ecology, i.e. the ability to predict ecological preferences from species’ traits. More specifically, can we predict Ellenberg indicator scores for soil nutrients, soil moisture and irradiance from four well-studied traits: leaf area, leaf dry matter content, specific leaf area (SLA) and seed mass? Can we use such relationships to estimate Ellenberg scores for species never classified by Ellenberg? Location Global. Methods Cumulative link models were developed to predict Ellenberg nutrients, irradiance and moisture values from Ln-transformed trait values using 922, 981 and 988 species, respectively. We then independently tested these prediction equations using the trait values of 423 and 421 new species that occurred elsewere in Europe, North America and Morocco, and whose habitat affinities we could classify from independent sources as three-level ordinal ranks related to soil moisture and irradiance. The traits were SLA, leaf dry matter content, leaf area and seed mass. Results The four functional traits predicted the Ellenberg indicator scores of site fertility, light and moisture with average error rates of <2 Ellenberg ranks out of nine. We then used the trait values of 423 and 421 species, respectively, that occurred (mostly) outside of Germany but whose habitat affinities we could classify as three-level ordinal ranks related to soil moisture and irradiance. The predicted positions of the new species, given the equations derived from the Ellenberg indices, agreed well with their independent habitat classifications, although our equation for Ellenberg irrandiance levels performed poorly on the lower ranks. Conclusions These prediction equations, and their eventual extensions, could be used to provide approximate descriptions of habitat affinities of large numbers of species worldwide.
Atmospheric deposition, CO2, and change in the land carbon sink
Fernández-Martínez, M. ; Vicca, S. ; Janssens, I.A. ; Ciais, P. ; Obersteiner, M. ; Bartrons, M. ; Sardans, Jordi ; Verger, Aleixandre ; Canadell, J.G. ; Chevallier, F. ; Wang, X. ; Bernhofer, C. ; Curtis, P.S. ; Gianelle, D. ; Grünwald, T. ; Heinesch, B. ; Ibrom, A. ; Knohl, A. ; Laurila, T. ; Law, Beverly E. ; Limousin, J.M. ; Longdoz, B. ; Loustau, D. ; Mammarella, I. ; Matteucci, G. ; Monson, R.K. ; Montagnani, L. ; Moors, E.J. ; Munger, J.W. ; Papale, D. ; Piao, S.L. ; Peñuelas, J. - \ 2017
Scientific Reports 7 (2017). - ISSN 2045-2322 - 13 p.

Concentrations of atmospheric carbon dioxide (CO2) have continued to increase whereas atmospheric deposition of sulphur and nitrogen has declined in Europe and the USA during recent decades. Using time series of flux observations from 23 forests distributed throughout Europe and the USA, and generalised mixed models, we found that forest-level net ecosystem production and gross primary production have increased by 1% annually from 1995 to 2011. Statistical models indicated that increasing atmospheric CO2 was the most important factor driving the increasing strength of carbon sinks in these forests. We also found that the reduction of sulphur deposition in Europe and the USA lead to higher recovery in ecosystem respiration than in gross primary production, thus limiting the increase of carbon sequestration. By contrast, trends in climate and nitrogen deposition did not significantly contribute to changing carbon fluxes during the studied period. Our findings support the hypothesis of a general CO2-fertilization effect on vegetation growth and suggest that, so far unknown, sulphur deposition plays a significant role in the carbon balance of forests in industrialized regions. Our results show the need to include the effects of changing atmospheric composition, beyond CO2, to assess future dynamics of carbon-climate feedbacks not currently considered in earth system/climate modelling.

Quantifying global soil carbon losses in response to warming
Crowther, T.W. ; Todd-Brown, K.E.O. ; Rowe, C.W. ; Wieder, W.R. ; Carey, J.C. ; Machmuller, M.B. ; Snoek, B.L. ; Fang, S. ; Zhou, G. ; Allison, S.D. ; Blair, J.M. ; Bridgham, S.D. ; Burton, A.J. ; Carrillo, Y. ; Reich, P.B. ; Clark, J.S. ; Classen, A.T. ; Dijkstra, F.A. ; Elberling, B. ; Emmett, B.A. ; Estiarte, M. ; Frey, S.D. ; Guo, J. ; Harte, J. ; Jiang, L. ; Johnson, B.R. ; Kröel-Dulay, G. ; Larsen, K.S. ; Laudon, H. ; Lavallee, J.M. ; Luo, Y. ; Lupascu, M. ; Ma, L.N. ; Marhan, S. ; Michelsen, A. ; Mohan, J. ; Niu, S. ; Pendall, E. ; Peñuelas, J. ; Pfeifer-Meister, L. ; Poll, C. ; Reinsch, S. ; Reynolds, L.L. ; Schmidt, I.K. ; Sistla, S. ; Sokol, N.W. ; Templer, P.H. ; Treseder, K.K. ; Welker, J.M. ; Bradford, M.A. - \ 2016
Nature 540 (2016)7631. - ISSN 0028-0836 - p. 104 - 108.
The majority of the Earth’s terrestrial carbon is stored in the soil. If anthropogenic warming stimulates the loss of this carbon to the atmosphere, it could drive further planetary warming. Despite evidence that warming enhances carbon fluxes to and from the soil the net global balance between these responses remains uncertain. Here we present a comprehensive analysis of warming-induced changes in soil carbon stocks by assembling data from 49 field experiments located across North America, Europe and Asia. We find that the effects of warming are contingent on the size of the initial soil carbon stock, with considerable losses occurring in high-latitude areas. By extrapolating this empirical relationship to the global scale, we provide estimates of soil carbon sensitivity to warming that may help to constrain Earth system model projections. Our empirical relationship suggests that global soil carbon stocks in the upper soil horizons will fall by 30 ± 30 petagrams of carbon to 203 ± 161 petagrams of carbon under one degree of warming, depending on the rate at which the effects of warming are realized. Under the conservative assumption that the response of soil carbon to warming occurs within a year, a business-as-usual climate scenario would drive the loss of 55 ± 50 petagrams of carbon from the upper soil horizons by 2050. This value is around 12–17 per cent of the expected anthropogenic emissions over this period. Despite the considerable uncertainty in our estimates, the direction of the global soil carbon response is consistent across all scenarios. This provides strong empirical support for the idea that rising temperatures will stimulate the net loss of soil carbon to the atmosphere, driving a positive land carbon–climate feedback that could accelerate climate change.
Trends in soil solution dissolved organic carbon (DOC) concentrations across European forests
Camino-Serrano, Marta ; Graf Pannatier, Elisabeth ; Vicca, Sara ; Luyssaert, Sebastiaan ; Jonard, Mathieu ; Ciais, Philippe ; Guenet, Bertrand ; Gielen, Bert ; Peñuelas, Josep ; Sardans, Jordi ; Waldner, Peter ; Sawicka, Kasia - \ 2016
Biogeosciences 13 (2016)19. - ISSN 1726-4170 - p. 5567 - 5585.

Dissolved organic carbon (DOC) in surface waters is connected to DOC in soil solution through hydrological pathways. Therefore, it is expected that long-term dynamics of DOC in surface waters reflect DOC trends in soil solution. However, a multitude of site studies have failed so far to establish consistent trends in soil solution DOC, whereas increasing concentrations in European surface waters over the past decades appear to be the norm, possibly as a result of recovery from acidification. The objectives of this study were therefore to understand the long-term trends of soil solution DOC from a large number of European forests (ICP Forests Level II plots) and determine their main physicochemical and biological controls. We applied trend analysis at two levels: (1) to the entire European dataset and (2) to the individual time series and related trends with plot characteristics, i.e., soil and vegetation properties, soil solution chemistry and atmospheric deposition loads. Analyses of the entire dataset showed an overall increasing trend in DOC concentrations in the organic layers, but, at individual plots and depths, there was no clear overall trend in soil solution DOC. The rate change in soil solution DOC ranged between-16.8 and +23%yr-1 (median=+0.4%yr-1 across Europe. The non-significant trends (40 %) outnumbered the increasing (35 %) and decreasing trends (25 %) across the 97 ICP Forests Level II sites. By means of multivariate statistics, we found increasing trends in DOC concentrations with increasing mean nitrate (NO3 -) deposition and increasing trends in DOC concentrations with decreasing mean sulfate (SO2- 4) deposition, with the magnitude of these relationships depending on plot deposition history. While the attribution of increasing trends in DOC to the reduction of SO2- 4 deposition could be confirmed in low to medium N deposition areas, in agreement with observations in surface waters, this was not the case in high N deposition areas. In conclusion, longterm trends of soil solution DOC reflected the interactions between controls acting at local (soil and vegetation properties) and regional (atmospheric deposition of SO2- 4 and inorganic N) scales.

Improved representation of plant functional types and physiology in the Joint UK Land Environment Simulator (JULES v4.2) using plant trait information
Harper, Anna B. ; Cox, Peter M. ; Friedlingstein, Pierre ; Wiltshire, Andy J. ; Jones, Chris D. ; Sitch, Stephen ; Mercado, Lina M. ; Groenendijk, Margriet ; Robertson, Eddy ; Kattge, Jens ; Bönisch, Gerhard ; Atkin, Owen K. ; Bahn, Michael ; Cornelissen, Johannes ; Niinemets, Ülo ; Onipchenko, Vladimir ; Peñuelas, Josep ; Poorter, Lourens ; Reich, Peter B. ; Soudzilovskaia, Nadjeda A. ; Bodegom, Peter van - \ 2016
Geoscientific Model Development 9 (2016)7. - ISSN 1991-959X - p. 2415 - 2440.

Dynamic global vegetation models are used to predict the response of vegetation to climate change. They are essential for planning ecosystem management, understanding carbon cycle-climate feedbacks, and evaluating the potential impacts of climate change on global ecosystems. JULES (the Joint UK Land Environment Simulator) represents terrestrial processes in the UK Hadley Centre family of models and in the first generation UK Earth System Model. Previously, JULES represented five plant functional types (PFTs): broadleaf trees, needle-leaf trees, C3 and C4 grasses, and shrubs. This study addresses three developments in JULES. First, trees and shrubs were split into deciduous and evergreen PFTs to better represent the range of leaf life spans and metabolic capacities that exists in nature. Second, we distinguished between temperate and tropical broadleaf evergreen trees. These first two changes result in a new set of nine PFTs: tropical and temperate broadleaf evergreen trees, broadleaf deciduous trees, needle-leaf evergreen and deciduous trees, C3 and C4 grasses, and evergreen and deciduous shrubs. Third, using data from the TRY database, we updated the relationship between leaf nitrogen and the maximum rate of carboxylation of Rubisco (Vcmax), and updated the leaf turnover and growth rates to include a trade-off between leaf life span and leaf mass per unit area. Overall, the simulation of gross and net primary productivity (GPP and NPP, respectively) is improved with the nine PFTs when compared to FLUXNET sites, a global GPP data set based on FLUXNET, and MODIS NPP. Compared to the standard five PFTs, the new nine PFTs simulate a higher GPP and NPP, with the exception of C3 grasses in cold environments and C4 grasses that were previously over-productive. On a biome scale, GPP is improved for all eight biomes evaluated and NPP is improved for most biomes - the exceptions being the tropical forests, savannahs, and extratropical mixed forests where simulated NPP is too high. With the new PFTs, the global present-day GPP and NPP are 128 and 62 Pg C year-1, respectively. We conclude that the inclusion of trait-based data and the evergreen/deciduous distinction has substantially improved productivity fluxes in JULES, in particular the representation of GPP. These developments increase the realism of JULES, enabling higher confidence in simulations of vegetation dynamics and carbon storage.

Remotely-sensed detection of effects of extreme droughts on gross primary production
Vicca, Sara ; Balzarolo, Manuela ; Filella, Iolanda ; Granier, André ; Herbst, Mathias ; Knohl, Alexander ; Longdoz, Bernard ; Mund, Martina ; Nagy, Zoltan ; Pintér, Krisztina ; Rambal, Serge ; Verbesselt, Jan ; Verger, Aleixandre ; Zeileis, Achim ; Zhang, Chao ; Peñuelas, Josep - \ 2016
Scientific Reports 6 (2016). - ISSN 2045-2322
Severe droughts strongly impact photosynthesis (GPP), and satellite imagery has yet to demonstrate its ability to detect drought effects. Especially changes in vegetation functioning when vegetation state remains unaltered (no browning or defoliation) pose a challenge to satellite-derived indicators. We evaluated the performance of different satellite indicators to detect strong drought effects on GPP in a beech forest in France (Hesse), where vegetation state remained largely unaffected while GPP decreased substantially. We compared the results with three additional sites: a Mediterranean holm oak forest (Puéchabon), a temperate beech forest (Hainich), and a semi-arid grassland (Bugacpuszta). In Hesse, a three-year reduction in GPP following drought was detected only by the Enhanced Vegetation Index (EVI). The Photochemical Reflectance Index (PRI) also detected this drought effect, but only after normalization for absorbed light. In Puéchabon normalized PRI outperformed the other indicators, while the short-term drought effect in Hainich was not detected by any tested indicator. In contrast, most indicators, but not PRI, captured the drought effects in Bugacpuszta. Hence, PRI improved detection of drought effects on GPP in forests and we propose that PRI normalized for absorbed light is considered in future algorithms to estimate GPP from space.
Matching the phenology of Net Ecosystem Exchange and vegetation indices estimated with MODIS and FLUXNET in-situ observations
Balzarolo, M. ; Vicca, S. ; Nguy-Robertson, A.L. ; Bonal, D. ; Elbers, J.A. ; Fu, Y.H. ; Grünwald, T. ; Horemans, J.A. ; Papale, D. ; Peñuelas, J. ; Suyker, A. ; Veroustraete, F. - \ 2016
Remote Sensing of Environment 174 (2016). - ISSN 0034-4257 - p. 290 - 300.
Net Ecosystem Exchange (NEE) - Phenology - Plant functional types (PFT's) - Start of growing season (SGS) - Start of net carbon uptake (SGS) - Vegetation indices (VI's)

Shifts in ecosystem phenology play an important role in the definition of inter-annual variability of net ecosystem carbon uptake. A good estimate at the global scale of ecosystem phenology, mainly that of photosynthesis or gross primary productivity (GPP), may be provided by vegetation indices derived from MODIS satellite image data.However, the relationship between the start date of a growing (or greening) season (SGS) when derived from different vegetation indices (VI's), and the starting day of carbon uptake is not well elucidated. Additionally, the validation of existing phenology data with in-situ measurements is largely missing. We have investigated the possibility to use different VI's to predict the starting day of the growing season for 28 FLUXNET sites as well as MODIS data. This analysis included main plant functional types (PFT's).Of all VI's taken into account in this paper, the NDVI (Normalized Difference Vegetation Index) shows the highest correlation coefficient for the relationship between the starting day of the growing season as observed with MODIS and in-situ observations. However, MODIS observations elicit a 20-21 days earlier SGS date compared to in-situ observations. The prediction for the NEE start of the growing season diverges when using different VI's, and seems to depend on the amplitude for carbon and VI and on PFT. The optimal VI for estimation of a SGS date was PFT-specific - for example the WRDVI for cropland, but the MODIS NDVI performed best when applied as an estimator for Net Ecosystem Exchange and when considering all PFT's pooled.

Intensive measurements of gas, water, and energy exchange between vegetation and troposhere during the MONTES campaign in a vegetation gradient from short semi-desertic shrublands to tall wet temperate forests in the NW Mediterranean Basin
Penuelas, J. ; Guenther, A. ; Rapparini, F. ; Llusia, J. ; Vilà-Guerau De Arellano, J. - \ 2013
Atmospheric Environment 75 (2013). - ISSN 1352-2310 - p. 348 - 364.
volatile organic-compounds - tethered balloon measurements - atmospheric boundary-layer - isoprene emission - quercus-ilex - biogenic emissions - particle formation - pinus-halepensis - field conditions - barcelona area
MONTES (“Woodlands”) was a multidisciplinary international field campaign aimed at measuring energy, water and especially gas exchange between vegetation and atmosphere in a gradient from short semi-desertic shrublands to tall wet temperate forests in NE Spain in the North Western Mediterranean Basin (WMB). The measurements were performed at a semidesertic area (Monegros), at a coastal Mediterranean shrubland area (Garraf), at a typical Mediterranean holm oak forest area (Prades) and at a wet temperate beech forest (Montseny) during spring (April 2010) under optimal plant physiological conditions in driest-warmest sites and during summer (July 2010) with drought and heat stresses in the driest–warmest sites and optimal conditions in the wettest–coolest site. The objective of this campaign was to study the differences in gas, water and energy exchange occurring at different vegetation coverages and biomasses. Particular attention was devoted to quantitatively understand the exchange of biogenic volatile organic compounds (BVOCs) because of their biological and environmental effects in the WMB. A wide range of instruments (GC–MS, PTR-MS, meteorological sensors, O3 monitors,…) and vertical platforms such as masts, tethered balloons and aircraft were used to characterize the gas, water and energy exchange at increasing footprint areas by measuring vertical profiles. In this paper we provide an overview of the MONTES campaign: the objectives, the characterization of the biomass and gas, water and energy exchange in the 4 sites-areas using satellite data, the estimation of isoprene and monoterpene emissions using MEGAN model, the measurements performed and the first results. The isoprene and monoterpene emission rates estimated with MEGAN and emission factors measured at the foliar level for the dominant species ranged from about 0 to 0.2 mg m-2 h-1 in April. The warmer temperature in July resulted in higher model estimates from about 0 to ca. 1.6 mg m-2 h-1 for isoprene and ca. 4.5 mg m-2 h-1 for monoterpenes, depending on the site vegetation and footprint area considered. There were clear daily and seasonal patterns with higher emission rates and mixing ratios at midday and summer relative to early morning and early spring. There was a significant trend in CO2 fixation (from 1 to 10 mg C m-2 d-1), transpiration (from 1–5 kg C m-2 d-1), and sensible and latent heat from the warmest–driest to the coolest–wettest site. The results showed the strong land-cover-specific influence on emissions of BVOCs, gas, energy and water exchange, and therefore demonstrate the potential for feed-back to atmospheric chemistry and climate
Patterns and controls of the variability of radiation use efficiency and primary productivity across terrestrial ecosystems
Garbulsky, M.F. ; Peñuelas, J. ; Papale, D. ; Ardö, J. ; Goulden, M.L. ; Kiely, G. ; Richardson, A.D. ; Rotenberg, E. ; Veenendaal, E.M. ; Filella, I. - \ 2010
Global Ecology and Biogeography 19 (2010). - ISSN 1466-822X - p. 253 - 267.
light-use efficiency - net primary production - gross primary production - carbon-dioxide exchange - comparing global-models - eddy covariance data - co2 exchange - pine forest - interannual variability - mediterranean forest
Aim The controls of gross radiation use efficiency (RUE), the ratio between gross primary productivity (GPP) and the radiation intercepted by terrestrial vegetation, and its spatial and temporal variation are not yet fully understood. Our objectives were to analyse and synthesize the spatial variability of GPP and the spatial and temporal variability of RUE and its climatic controls for a wide range of vegetation types. Location A global range of sites from tundra to rain forest. Methods We analysed a global dataset on photosynthetic uptake and climatic variables from 35 eddy covariance (EC) flux sites spanning between 100 and 2200 mm mean annual rainfall and between -13 and 26°C mean annual temperature. RUE was calculated from the data provided by EC flux sites and remote sensing (MODIS). Results Rainfall and actual evapotranspiration (AET) positively influenced the spatial variation of annual GPP, whereas temperature only influenced the GPP of forests. Annual and maximum RUE were also positively controlled primarily by annual rainfall. The main control parameters of the growth season variation of gross RUE varied for each ecosystem type. Overall, the ratio between actual and potential evapotranspiration and a surrogate for the energy balance explained a greater proportion of the seasonal variation of RUE than the vapour pressure deficit (VPD), AET and precipitation. Temperature was important for determining the intra-annual variability of the RUE at the coldest energy-limited sites. Main conclusions Our analysis supports the idea that the annual functioning of vegetation that is adapted to its local environment is more constrained by water availability than by temperature. The spatial variability of annual and maximum RUE can be largely explained by annual precipitation, more than by vegetation type. The intra-annual variation of RUE was mainly linked to the energy balance and water availability along the climatic gradient. Furthermore, we showed that intra-annual variation of gross RUE is only weakly influenced by VPD and temperature, contrary to what is frequently assumed. Our results provide a better understanding of the spatial and temporal controls of the RUE and thus could lead to a better estimation of ecosystem carbon fixation and better modelling.
Carbon and nitrogen balances for six shrublands across Europe
Beier, C. ; Emmett, B.A. ; Tietema, A. ; Schmidt, I.K. ; Penuelas, J. ; Lang, E.K. ; Duce, P. ; Angelis, P. de; Gorissen, A. ; Estiarte, M. ; Dato, G.D. de; Sowerby, A. ; Kroel-Dulay, G. ; Lellei-Kovacs, E. ; Kull, O. ; Mand, P. ; Petersen, H. ; Gjelstrup, P. ; Spano, D. - \ 2009
Global Biogeochemical Cycles 23 (2009). - ISSN 0886-6236 - 13 p.
microbial biomass-c - climate-change - terrestrial ecosystems - soil respiration - forest ecosystems - extraction method - global patterns - elevated co2 - drought - responses
Shrublands constitute significant and important parts of European landscapes providing a large number of important ecosystem services. Biogeochemical cycles in these ecosystems have gained little attention relative to forests and grassland systems, but data on such cycles are required for developing and testing ecosystem models. As climate change progresses, the potential feedback from terrestrial ecosystems to the atmosphere through changes in carbon stocks, carbon sequestration, and general knowledge on biogeochemical cycles becomes increasingly important. Here we present carbon and nitrogen balances of six shrublands along a climatic gradient across the European continent. The aim of the study was to provide a basis for assessing the range and variability in carbon storage in European shrublands. Across the sites the net carbon storage in the systems ranged from 1,163 g C m(-2) to 18,546 g C m(-2), and the systems ranged from being net sinks (126 g C m(-2) a(-1)) to being net sources (-536 g C m(-2) a(-1)) of carbon with the largest storage and sink of carbon at wet and cold climatic conditions. The soil carbon store dominates the carbon budget at all sites and in particular at the site with a cold and wet climate where soil C constitutes 95% of the total carbon in the ecosystem. Respiration of carbon from the soil organic matter pool dominated the carbon loss at all sites while carbon loss from aboveground litter decomposition appeared less important. Total belowground carbon allocation was more than 5 times aboveground litterfall carbon which is significantly greater than the factor of 2 reported in a global analysis of forest data. Nitrogen storage was also dominated by the soil pools generally showing small losses except when atmospheric N input was high. The study shows that in the future a climate-driven land cover change between grasslands and shrublands in Europe will likely lead to increased ecosystem C where shrublands are promoted and less where grasses are promoted. However, it also emphasizes that if feedbacks on the global carbon cycle are to be predicted it is critically important to quantify and understand belowground carbon allocation and processes as well as soil carbon pools, particularly on wet organic soils, rather than plant functional change as the soil stores dominate the overall budget and fluxes of carbon
Carbon and nitrogen cycles in European ecosystems respond differently to global warming
Beier, C. ; Emmett, B.A. ; Penuelas, J. ; Schmidt, I.K. ; Tietema, A. ; Estiarte, M. ; Gundersen, P. ; Llorens, L. ; Riis-Nielsen, T. ; Sowerby, A. ; Gorissen, A. - \ 2008
Science of the Total Environment 407 (2008)1. - ISSN 0048-9697 - p. 692 - 697.
climate-change - soil respiration - drought - temperature - forests - feedbacks - gradient - dioxide - impacts - plants
The global climate is predicted to become significantly warmer over the next century. This will affect ecosystem processes and the functioning of semi natural and natural ecosystems in many parts of the world. However, as various ecosystem processes may be affected to a different extent, balances between different ecosystem processes as well as between different ecosystems may shift and lead to major unpredicted changes. In this study four European shrubland ecosystems along a north¿south temperature gradient were experimentally warmed by a novel nighttime warming technique. Biogeochemical cycling of both carbon and nitrogen was affected at the colder sites with increased carbon uptake for plant growth as well as increased carbon loss through soil respiration. Carbon uptake by plant growth was more sensitive to warming than expected from the temperature response across the sites while carbon loss through soil respiration reacted to warming in agreement with the overall Q10 and response functions to temperature across the sites. Opposite to carbon, the nitrogen mineralization was relatively insensitive to the temperature increase and was mainly affected by changes in soil moisture. The results suggest that C and N cycles respond asymmetrically to warming, which may lead to progressive nitrogen limitation and thereby acclimation in plant production. This further suggests that in many temperate zones nitrogen deposition has to be accounted for, not only with respect to the impact on water quality through increased nitrogen leaching where N deposition is high, but also in predictions of carbon sequestration in terrestrial ecosystems under future climatic conditions. Finally the results indicate that on the short term the above-ground processes are more sensitive to temperature changes than the below ground processes
Response of plant species richness and primary productivity in shrublands along a north-south gradient in Europe to seven years of experimental warming and drought: reductions in primary productivity in the heat and drought year of 2003
Penuelas, J. ; Prieto, P. ; Beier, C. ; Cesaraccio, C. ; Angelis, P. de; Dato, G. de; Emmett, B.A. ; Estiarte, M. ; Garadnai, J. ; Gorissen, A. ; Lang, E.K. ; Kroel-Dulay, G. ; Llorens, L. ; Pellizzaro, G. ; Riis-Nielsen, T. ; Schmidt, I.K. ; Sirca, C. ; Sowerby, A. ; Spano, D. ; Tietema, A. - \ 2007
Global Change Biology 13 (2007)12. - ISSN 1354-1013 - p. 2563 - 2581.
evergreen mediterranean forest - climate-change - quercus-ilex - terrestrial ecosystems - environmental-change - phillyrea-latifolia - arctic ecosystems - cistus-albidus - carbon-cycle - soil
We used a nonintrusive field experiment carried out at six sites - Wales (UK), Denmark (DK), the Netherlands (NL), Hungary (HU), Sardinia (Italy - IT), and Catalonia (Spain - SP) - along a climatic and latitudinal gradient to examine the response of plant species richness and primary productivity to warming and drought in shrubland ecosystems. The warming treatment raised the plot daily temperature by ca. 1 degrees C, while the drought treatment led to a reduction in soil moisture at the peak of the growing season that ranged from 26% at the SP site to 82% in the NL site. During the 7 years the experiment lasted (1999-2005), we used the pin-point method to measure the species composition of plant communities and plant biomass, litterfall, and shoot growth of the dominant plant species at each site. A significantly lower increase in the number of species pin-pointed per transect was found in the drought plots at the SP site, where the plant community was still in a process of recovering from a forest fire in 1994. No changes in species richness were found at the other sites, which were at a more mature and stable state of succession and, thus less liable to recruitment of new species. The relationship between annual biomass accumulation and temperature of the growing season was positive at the coldest site and negative at the warmest site. The warming treatment tended to increase the aboveground net primary productivity (ANPP) at the northern sites. The relationship between annual biomass accumulation and soil moisture during the growing season was not significant at the wettest sites, but was positive at the driest sites. The drought treatment tended to reduce the ANPP in the NL, HU, IT, and SP sites. The responses to warming were very strongly related to the Gaussen aridity index (stronger responses the lower the aridity), whereas the responses to drought were not. Changes in the annual aboveground biomass accumulation, litterfall, and, thus, the ANPP, mirrored the interannual variation in climate conditions: the most outstanding change was a decrease in biomass accumulation and an increase in litterfall at most sites during the abnormally hot year of 2003. Species richness also tended to decrease in 2003 at all sites except the cold and wet UK site. Species-specific responses to warming were found in shoot growth: at the SP site, Globularia alypum was not affected, while the other dominant species, Erica multiflora, grew 30% more; at the UK site, Calluna vulgaris tended to grow more in the warming plots, while Empetrum nigrum tended to grow less. Drought treatment decreased plant growth in several studied species, although there were some species such as Pinus halepensis at the SP site or C. vulgaris at the UK site that were not affected. The magnitude of responses to warming and drought thus depended greatly on the differences between sites, years, and species and these multiple plant responses may be expected to have consequences at ecosystem and community level. Decreases in biodiversity and the increase in E. multiflora growth at the SP site as a response to warming challenge the assumption that sensitivity to warming may be less well developed at more southerly latitudes; likewise, the fact that one of the studied shrublands presented negative ANPP as a response to the 2003 heat wave also challenges the hypothesis that future climate warming will lead to an enhancement of plant growth and carbon sequestration in temperate ecosystems. Extreme events may thus change the general trend of increased productivity in response to warming n the colder sites.
Challenges in quantifying biosphere-atmosphere exchange of nitrogen species.
Sutton, M.A. ; Nemitz, E. ; Erisman, J.W. ; Beier, C. ; Butterbach-Bahl, K. ; Cellier, P. ; Vries, W. de; Cotrufo, F. ; Skiba, U. ; Marco, C. Di; Jones, S. ; Laville, P. ; Soussana, J.F. ; Loubet, B. ; Twigg, M. ; Famulari, D. ; Whitehead, J. ; Gallagher, M.W. ; Neftel, A. ; Flechard, C.R. ; Herrmann, B. ; Calanca, P.L. ; Schjoerring, J.K. ; Daemmgen, U. ; Horvath, L. ; Tang, Y.S. ; Emmet, B.A. ; Tietema, A. ; Penuelas, J. ; Kesik, M. ; Brueggemann, N. ; Pilegaard, K. ; Vesala, T. ; Campbell, C.L. ; Olesen, J.E. ; Dragosits, U. ; Theobald, M.R. ; Levy, P. ; Mobbs, D.C. ; Milne, R. ; Viovy, N. ; Vuichard, N. ; Smith, J.U. ; Smith, P. ; Bergamaschi, P. ; Fowler, D. ; Reis, S. Dos - \ 2007
Environmental Pollution 150 (2007)1. - ISSN 0269-7491 - p. 125 - 139.
gas-particle interactions - surface-exchange - simulation-model - ammonia exchange - dutch heathland - climate-change - oxide fluxes - trace gases - deposition - soil
Recent research in nitrogen exchange with the atmosphere has separated research communities according to N form. The integrated perspective needed to quantify the net effect of N on greenhouse-gas balance is being addressed by the NitroEurope Integrated Project (NEU). Recent advances have depended on improved methodologies, while ongoing challenges include gas¿aerosol interactions, organic nitrogen and N2 fluxes. The NEU strategy applies a 3-tier Flux Network together with a Manipulation Network of global-change experiments, linked by common protocols to facilitate model application. Substantial progress has been made in modelling N fluxes, especially for N2O, NO and bi-directional NH3 exchange. Landscape analysis represents an emerging challenge to address the spatial interactions between farms, fields, ecosystems, catchments and air dispersion/deposition. European up-scaling of N fluxes is highly uncertain and a key priority is for better data on agricultural practices. Finally, attention is needed to develop N flux verification procedures to assess compliance with international protocols.
Fluorescence explorer (FLEX): An optimised payload to map vegetation photosynthesis from space
Moreno, J.F. ; Asner, G.P. ; Bach, H. ; Belenguer, T. ; Bell, A. ; Buschmann, C. ; Calera, A. ; Calpe, J. ; Campbell, P. ; Cecchi, G. ; Colombo, R. ; Corp, L.A. ; Court, A. ; Cutter, M.A. ; Disney, M. ; Dudelzak, A. ; Urso, G. D'; Fernandes, R. ; Flexas, J. ; Gege, P. ; Gielen, B. ; Gitelson, A. ; Gloor, E.U. ; Gower, J. ; Green, R.O. ; Hill, J. ; Jacquemoud, S. ; Jia, L. ; Kneubühler, M. ; Laurila, T. ; Lewis, P. ; Lobb, D. ; Magnani, F. ; Maier, S.W. ; Martinez, A. ; Marek, M.V. ; Martinez Cobo, P. ; Mazzinghi, P. ; Menenti, M. ; Merton, R. ; Middleton, E. ; Miguel, E. De; Miller, J. ; Mohammed, G. ; Milton, E.J. ; Morales, F. ; Moya, I. ; Nedbal, L. ; Knorr, W. ; Ottle, C. ; Olioso, A. ; Pace, S. ; Palucci, A. ; Pedros, R. ; Peltoniemi, J. ; Penuelas, J. ; Plaza, A.J. ; Polcher, J. ; Rascher, U. ; Reuter, R. ; Rosema, A. ; Roujean, J.L. ; Saito, Y. ; Saugier, B. ; Schaepman, M.E. ; Serrano, J.B. ; Settle, J.J. ; Sierra, M. ; Sobrino, J. ; Stoll, M.P. ; Su, Z. ; Tobehn, C. ; Tremblay, N. ; Valcke, R. ; Verhoef, W. ; Veroustraete, F. ; Verstraete, M. ; Zarco Tejada, P. - \ 2006
In: Proceedings AIAA 57th International Astronautical Congress, 2 - 6 October, 2006, Valencia, Spain. - Valencia : AIAA - p. 2065 - 2074.
European phenological response to climate change matches the warming pattern
Menzel, A. ; Sparks, T. ; Estrella, N. ; Koch, E. ; Aasa, A. ; Ahas, R. ; Alm-Kübler, K. ; Bissolli, P. ; Braslavska, O. ; Briede, A. ; Chmielewski, F.M. ; Crepinsek, Z. ; Curnel, Y. ; Dahl, A. ; Defila, C. ; Donnelly, A. ; Filella, Y. ; Jatczak, K. ; Mage, F. ; Mestre, A. ; Nordli, O. ; Penuelas, J. ; Pirinen, P. ; Remisova, V. ; Scheifinger, H. ; Striz, M. ; Susnik, A. ; Vliet, A.J.H. van; Wielgolaski, F.E. ; Zach, S. ; Zust, A. - \ 2006
Global Change Biology 12 (2006)10. - ISSN 1354-1013 - p. 1969 - 1976.
klimaatverandering - temperatuur - fenologie - ecologie - climatic change - temperature - phenology - ecology - phytophenological trends - season - plants
Global climate change impacts can already be tracked in many physical and biological systems; in particular, terrestrial ecosystems provide a consistent picture of observed changes. One of the preferred indicators is phenology, the science of natural recurring events, as their recorded dates provide a high-temporal resolution of ongoing changes. Thus, numerous analyses have demonstrated an earlier onset of spring events for mid and higher latitudes and a lengthening of the growing season. However, published single-site or single-species studies are particularly open to suspicion of being biased towards predominantly reporting climate change-induced impacts. No comprehensive study or meta-analysis has so far examined the possible lack of evidence for changes or shifts at sites where no temperature change is observed. We used an enormous systematic phenological network data set of more than 125000 observational series of 542 plant and 19 animal species in 21 European countries (1971-2000). Our results showed that 78% of all leafing, flowering and fruiting records advanced (30% significantly) and only 3% were significantly delayed, whereas the signal of leaf colouring/fall is ambiguous. We conclude that previously published results of phenological changes were not biased by reporting or publication predisposition: the average advance of spring/summer was 2.5 days decade-1 in Europe. Our analysis of 254 mean national time series undoubtedly demonstrates that species' phenology is responsive to temperature of the preceding months (mean advance of spring/summer by 2.5 days °C-1, delay of leaf colouring and fall by 1.0 day °C-1). The pattern of observed change in spring efficiently matches measured national warming across 19 European countries (correlation coefficient r = -0.69, P <0.001)
Nonintrusive Field Experiments Show Different Plant Responses to Warming and Drought Among Sites, Seasons, and Species in a North-South European Gradient
Peñuelas, J. ; Gordon, C. ; Llorens, L. ; Nielsen, T. ; Tietema, A. ; Beier, J.C. ; Bruna, P. ; Emmett, B. ; Estiarte, M. ; Gorissen, A. - \ 2004
Ecosystems 7 (2004)6. - ISSN 1432-9840 - p. 598 - 612.
terrestrial ecosystems - environmental-change - cistus-albidus - climate-change - temperature - nutrient - quercus - tundra - winter - life
We used a novel, nonintrusive experimental system to examine plant responses to warming and drought across a climatic and geographical latitudinal gradient of shrubland ecosystems in four sites from northern to southern Europe (UK, Denmark, The Netherlands, and Spain). In the first two years of experimentation reported here, we measured plant cover and biomass by the pinpoint method, plant 14C uptake, stem and shoot growth, flowering, leaf chemical concentration, litterfall, and herbivory damage in the dominant plant species of each site. The two years of approximately 1°C experimental warming induced a 15% increase in total aboveground plant biomass growth in the UK site. Both direct and indirect effects of warming, such as longer growth season and increased nutrient availability, are likely to be particularly important in this and the other northern sites which tend to be temperature-limited. In the water-stressed southern site, there was no increase in total aboveground plant biomass growth as expected since warming increases water loss, and temperatures in those ecosystems are already close to the optimum for photosynthesis. The southern site presented instead the most negative response to the drought treatment consisting of a soil moisture reduction at the peak of the growing season ranging from 33% in the Spanish site to 82% in The Netherlands site. In the Spanish site there was a 14% decrease in total aboveground plant biomass growth relative to control. Flowering was decreased by drought (up to 24% in the UK and 40% in Spain). Warming and drought decreased litterfall in The Netherlands site (33% and 37%, respectively) but did not affect it in the Spanish site. The tissue P concentrations generally decreased and the N/P ratio increased with warming and drought except in the UK site, indicating a progressive importance of P limitation as a consequence of warming and drought. The magnitude of the response to warming and drought was thus very sensitive to differences among sites (cold-wet northern sites were more sensitive to warming and the warm-dry southern site was more sensitive to drought), seasons (plant processes were more sensitive to warming during the winter than during the summer), and species. As a result of these multiple plant responses, ecosystem and community level consequences may be expected.
Novel approaches to study climate change effects on terrestrial ecosystems: drought and passive nighttime warming
Beier, J.C. ; Emmett, B. ; Gundersen, P. ; Tietema, A. ; Peñuelas, J. ; Estiarte, M. ; Gordon, C. ; Gorissen, A. ; Llorens, L. ; Roda, F. ; Williams, D.G. - \ 2004
Ecosystems 7 (2004)6. - ISSN 1432-9840 - p. 583 - 597.
global change - nitrogen dynamics - forest ecosystems - southern norway - carbon balance - climex project - upland soils - temperature - responses - microclimate
This article describes new approaches for manipulation of temperature and water input in the field. Nighttime warming was created by reflection of infrared radiation. Automatically operated reflective curtains covered the vegetation at night to reduce heat loss to the atmosphere. This approach mimicked the way climate change, caused by increased cloudiness and increased greenhouse gas emissions, alters the heat balance of ecosystems. Drought conditions were created by automatically covering the vegetation with transparent curtains during rain events over a 2-5-month period. The experimental approach has been evaluated at four European sites across a climate gradient. All sites were dominated (more than 50%) by shrubs of the ericaceous family. Within each site, replicated 4-m × 5-m plots were established for control, warming, and drought treatments and the effect on climate variables recorded. Results over a two-year period indicate that the warming treatment was successful in achieving an increase of the minimum temperatures by 0.4-1.2°C in the air and soil. The drought treatment resulted in a soil moisture reduction of 33%-82% at the peak of the drought. The data presented demonstrate that the approach minimizes unintended artifacts with respect to water balance, moisture conditions, and light, while causing a small but significant reduction in wind speed by the curtains. Temperature measurements demonstrated that the edge effects associated with the treatments were small. Our method provides a valuable tool for investigating the effects of climate change in remote locations with minimal artifacts.
Climate change affects carbon allocation to the soil in shrublands
Gorissen, A. ; Tietema, A. ; Joosten, N.N. ; Estiarte, M. ; Peñuelas, J. ; Sowerby, A. ; Emmett, B. ; Beier, J.C. - \ 2004
Ecosystems 7 (2004)6. - ISSN 1432-9840 - p. 650 - 661.
lolium-perenne - calluna-vulgaris - plant - temperature - rhizosphere - decomposition - photosynthesis - translocation - respiration - dioxide
Climate change may affect ecosystem functioning through increased temperatures or changes in precipitation patterns. Temperature and water availability are important drivers for ecosystem processes such as photosynthesis, carbon translocation, and organic matter decomposition. These climate changes may affect the supply of carbon and energy to the soil microbial population and subsequently alter decomposition and mineralization, important ecosystem processes in carbon and nutrient cycling. In this study, carried out within the cross-European research project CLIMOOR, the effect of climate change, resulting from imposed manipulations, on carbon dynamics in shrubland ecosystems was examined. We performed a 14C-labeling experiment to probe changes in net carbon uptake and allocation to the roots and soil compartments as affected by a higher temperature during the year and a drought period in the growing season. Differences in climate, soil, and plant characteristics resulted in a gradient in the severity of the drought effects on net carbon uptake by plants with the impact being most severe in Spain, followed by Denmark, with the UK showing few negative effects at significance levels of p 0.10. Drought clearly reduced carbon flow from the roots to the soil compartments. The fraction of the 14C fixed by the plants and allocated into the soluble carbon fraction in the soil and to soil microbial biomass in Denmark and the UK decreased by more than 60%. The effects of warming were not significant, but, as with the drought treatment, a negative effect on carbon allocation to soil microbial biomass was found. The changes in carbon allocation to soil microbial biomass at the northern sites in this study indicate that soil microbial biomass is a sensitive, early indicator of drought- or temperature-initiated changes in these shrubland ecosystems. The reduced supply of substrate to the soil and the response of the soil microbial biomass may help to explain the observed acclimation of CO2 exchange in other ecosystems.
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