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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    Effect of nitrogen on fungal growth efficiency
    Lonardo, D.P. Di; Wal, A. van der; Harkes, P. ; Boer, W. de - \ 2020
    Plant Biosystems 154 (2020)4. - ISSN 1126-3504 - p. 433 - 437.
    C:N ratios - ergosterol - growth efficiency - respiration - saprotrophic fungi

    The contribution of fungi to carbon (C) and nitrogen (N) cycling is related to their growth efficiency (amount of biomass produced per unit of substrate utilized). The concentration and availability of N influence the activity and growth efficiency of saprotrophic fungi. When N is scarce in soils, fungi have to invest more energy to obtain soil N, which could result in lower growth efficiencies. Yet, the effect of N on the growth efficiencies of individual species of fungi in soil has not been studied extensively. In this study, we investigated the influence of different concentrations of mineral N on the growth efficiency of two common soil fungi, Trichoderma harzianum and Mucor hiemalis in a soil-like environment. We hypothesized that a higher N availability will coincide with higher biomass production and growth efficiency. We measured fungal biomass production and respiration fluxes in sand microcosms amended with cellobiose and mineral N at different C:N ratios. For both fungal species lower C:N ratios resulted in the highest biomass production as well as the highest growth efficiency. This may imply that when N is applied concurrently with a degradable C source, a higher amount of N will be temporarily immobilized into fungal biomass.

    Using a reaction-diffusion model to estimate day respiration and reassimilation of (photo)respired CO2 in leaves
    Berghuijs, Herman N.C. ; Yin, Xinyou ; Ho, Q.T. ; Retta, Moges A. ; Nicolaï, Bart M. ; Struik, Paul C. - \ 2019
    New Phytologist 223 (2019)2. - ISSN 0028-646X - p. 619 - 631.
    C photosynthesis - mesophyll conductance - photorespiration - reaction-diffusion model - reassimilation - respiration

    Methods using gas exchange measurements to estimate respiration in the light (day respiration R d ) make implicit assumptions about reassimilation of (photo)respired CO 2 ; however, this reassimilation depends on the positions of mitochondria. We used a reaction-diffusion model without making these assumptions to analyse datasets on gas exchange, chlorophyll fluorescence and anatomy for tomato leaves. We investigated how R d values obtained by the Kok and the Yin methods are affected by these assumptions and how those by the Laisk method are affected by the positions of mitochondria. The Kok method always underestimated R d . Estimates of R d by the Yin method and by the reaction-diffusion model agreed only for nonphotorespiratory conditions. Both the Yin and Kok methods ignore reassimilation of (photo)respired CO 2 , and thus underestimated R d for photorespiratory conditions, but this was less so in the Yin than in the Kok method. Estimates by the Laisk method were affected by assumed positions of mitochondria. It did not work if mitochondria were in the cytosol between the plasmamembrane and the chloroplast envelope. However, mitochondria were found to be most likely between the tonoplast and chloroplasts. Our reaction-diffusion model effectively estimates R d , enlightens the dependence of R d estimates on reassimilation and clarifies (dis)advantages of existing methods.

    The relationship between leaf area growth and biomass accumulation in Arabidopsis thaliana
    Weraduwage, S.M. ; Chen, J. ; Anozie, F.C. ; Morales Sierra, A. ; Weise, S.E. ; Sharkey, T.D. - \ 2015
    Frontiers in Plant Science 6 (2015). - ISSN 1664-462X - 21 p.
    plant-growth - photosynthetic acclimation - nighttime transpiration - phaseolus-vulgaris - starch turnover - root-growth - model - respiration - light - maintenance
    Leaf area growth determines the light interception capacity of a crop and is often used as a surrogate for plant growth in high-throughput phenotyping systems. The relationship between leaf area growth and growth in terms of mass will depend on how carbon is partitioned among new leaf area, leaf mass, root mass, reproduction, and respiration. A model of leaf area growth in terms of photosynthetic rate and carbon partitioning to different plant organs was developed and tested with Arabidopsis thaliana L. Heynh. ecotype Columbia (Col-0) and a mutant line, gigantea-2 (gi-2), which develops very large rosettes. Data obtained from growth analysis and gas exchange measurements was used to train a genetic programming algorithm to parameterize and test the above model. The relationship between leaf area and plant biomass was found to be non-linear and variable depending on carbon partitioning. The model output was sensitive to the rate of photosynthesis but more sensitive to the amount of carbon partitioned to growing thicker leaves. The large rosette size of gi-2 relative to that of Col-0 resulted from relatively small differences in partitioning to new leaf area vs. leaf thickness.
    Methane, Carbon Dioxide and Nitrous Oxide Fluxes in Soil Profile under a Winter Wheat-Summer Maize Rotation in the North China Plain
    Wang, Y.Y. ; Hu, C.S. ; Ming, H. ; Oenema, O. ; Schaefer, D.A. ; Dong, W.X. ; Zhang, Y.M. ; Li, X.X. - \ 2014
    PLoS ONE 9 (2014)6. - ISSN 1932-6203
    forest soils - co2 efflux - gas emissions - n2o fluxes - ch4 - respiration - temperature - mitigation - diffusion - slurry
    The production and consumption of the greenhouse gases (GHGs) methane (CH4), carbon dioxide (CO2) and nitrous oxide (N2O) in soil profile are poorly understood. This work sought to quantify the GHG production and consumption at seven depths (0-30, 30-60, 60-90, 90-150, 150-200, 200-250 and 250-300 cm) in a long-term field experiment with a winter wheat-summer maize rotation system, and four N application rates (0; 200; 400 and 600 kg N ha(-1) year(-1)) in the North China Plain. The gas samples were taken twice a week and analyzed by gas chromatography. GHG production and consumption in soil layers were inferred using Fick's law. Results showed nitrogen application significantly increased N2O fluxes in soil down to 90 cm but did not affect CH4 and CO2 fluxes. Soil moisture played an important role in soil profile GHG fluxes; both CH4 consumption and CO2 fluxes in and from soil tended to decrease with increasing soil water filled pore space (WFPS). The top 0-60 cm of soil was a sink of atmospheric CH4, and a source of both CO2 and N2O, more than 90% of the annual cumulative GHG fluxes originated at depths shallower than 90 cm; the subsoil (>90 cm) was not a major source or sink of GHG, rather it acted as a 'reservoir'. This study provides quantitative evidence for the production and consumption of CH4, CO2 and N2O in the soil profile.
    Nutrients trigger carbon storage
    Vries, W. de - \ 2014
    Nature Climate Change 4 (2014). - ISSN 1758-678X - p. 425 - 426.
    nitrogen - co2 - productivity - respiration - enhancement - sink
    Analysis of data from 92 forested sites across the globe indicates that nutrient availability is the dominant driver of carbon retention in forests.
    Global cropland monthly gross primary production in the year 2000
    Chen, T. ; Werf, G.R. van der; Gobron, N. ; Moors, E.J. ; Dolman, A.J. - \ 2014
    Biogeosciences 11 (2014). - ISSN 1726-4170 - p. 3871 - 3880.
    net primary production - light-use efficiency - ecosystem exchange - constant fraction - terrestrial gross - model - forest - modis - respiration - climate
    Croplands cover about 12% of the ice-free terrestrial land surface. Compared with natural ecosystems, croplands have distinct characteristics due to anthropogenic influences. Their global gross primary production (GPP) is not well constrained and estimates vary between 8.2 and 14.2 Pg C yr-1. We quantified global cropland GPP using a light use efficiency (LUE) model, employing satellite observations and survey data of crop types and distribution. A novel step in our analysis was to assign a maximum light use efficiency estimate (¿*GPP) to each of the 26 different crop types, instead of taking a uniform value as done in the past. These ¿*GPP values were calculated based on flux tower CO2 exchange measurements and a literature survey of field studies, and ranged from 1.20 to 2.96 g C MJ-1. Global cropland GPP was estimated to be 11.05 Pg C yr-1 in the year 2000. Maize contributed most to this (1.55 Pg C yr-1), and the continent of Asia contributed most with 38.9% of global cropland GPP. In the continental United States, annual cropland GPP (1.28 Pg C yr-1) was close to values reported previously (1.24 Pg C yr-1) constrained by harvest records, but our estimates of ¿*GPP values were considerably higher. Our results are sensitive to satellite information and survey data on crop type and extent, but provide a consistent and data-driven approach to generate a look-up table of ¿*GPP for the 26 crop types for potential use in other vegetation models.
    Coral calcification under daily oxygen saturation and pH dynamics reveals the important role of oxygen
    Wijgerde, T.H.M. ; Silva, C.I.F. ; Scherders, V. ; Bleijswijk, J. van; Osinga, R. - \ 2014
    Biology Open 3 (2014)6. - ISSN 2046-6390 - p. 489 - 493.
    galaxea-fascicularis - scleractinian corals - carbonate chemistry - ocean acidification - photosynthesis - reefs - light - respiration - ecosystems - impacts
    Coral reefs are essential to many nations, and are currently in global decline. Although climate models predict decreases in seawater pH (~0.3 units) and oxygen saturation (~5 percentage points), these are exceeded by the current daily pH and oxygen fluctuations on many reefs (pH 7.8-8.7 and 27-241% O2 saturation). We investigated the effect of oxygen and pH fluctuations on coral calcification in the laboratory using the model species Acropora millepora. Light calcification rates were greatly enhanced (+178%) by increased seawater pH, but only at normoxia; hyperoxia completely negated this positive effect. Dark calcification rates were significantly inhibited (51-75%) at hypoxia, whereas pH had no effect. Our preliminary results suggest that within the current oxygen and pH range, oxygen has substantial control over coral growth, whereas the role of pH is limited. This has implications for reef formation in this era of rapid climate change, which is accompanied by a decrease in seawater oxygen saturation owing to higher water temperatures and coastal eutrophication.
    Data-based perfect-deficit approach to understanding climate extremes and forest carbon assimilation capacity
    Wei, S. ; Yi, C. ; Hendrey, G. ; Eaton, T. ; Rustic, G. ; Wang, S. ; Liu, H. ; Krakauer, N.Y. ; Wang, W. ; Desai, A.R. ; Moors, E.J. - \ 2014
    Environmental Research Letters 9 (2014). - ISSN 1748-9326
    net ecosystem exchange - drought - respiration - algorithm - heat - reduction - feedbacks - model
    Several lines of evidence suggest that the warming climate plays a vital role in driving certain types of extreme weather. The impact of warming and of extreme weather on forest carbon assimilation capacity is poorly known. Filling this knowledge gap is critical towards understanding the amount of carbon that forests can hold. Here, we used a perfect-deficit approach to identify forest canopy photosynthetic capacity (CPC) deficits and analyze how they correlate to climate extremes, based on observational data measured by the eddy covariance method at 27 forest sites over 146 site-years. We found that droughts severely affect the carbon assimilation capacities of evergreen broadleaf forest (EBF) and deciduous broadleaf forest. The carbon assimilation capacities of Mediterranean forests were highly sensitive to climate extremes, while marine forest climates tended to be insensitive to climate extremes. Our estimates suggest an average global reduction of forest CPC due to unfavorable climate extremes of 6.3 Pg C (~5.2% of global gross primary production) per growing season over 2001–2010, with EBFs contributing 52% of the total reduction.
    How to map soil organic carbon stocks in highly urbanized regions?
    Vasenev, V.I. ; Stoorvogel, J.J. ; Vasenev, I.I. ; Valentini, R. - \ 2014
    Geoderma 226-227 (2014). - ISSN 0016-7061 - p. 103 - 115.
    united-states - european russia - land-use - climate - systems - respiration - ecosystems - forests - balance - storage
    Urbanization is among the most impetuous current land-use change trends, resulting in a permanently increasing role of urban ecosystems in regional and global environments. Urban soil organic carbon (SOC) is probably the least understood stocks because of the lack of appropriate methodology to analyze and map it. Cities represent a small-scale patchwork of very contrasting soil features. This creates high short-term spatial variability. Urban-specific factors including size and age of the city, soil sealing and cut-off profiles dominate the anthropogenic soil forming factors. Considering these specific urban environments, our study aimed to adapt the digital soil mapping (DSM) approach to map topsoil and subsoil SOC stocks in a highly urbanized region. Field SOC data collected for different environmental conditions in the Moscow region (five soil types and five land-use types of 244 mixed samples for topsoil and subsoil) were linked to available auxiliary data, including both traditional (relief, climate, vegetation etc.) and urban-specific (functional zoning, size and history of the settlements) factors. Separate general linear models (GLM) were developed for the three different cases: i) excluding urban areas fromthe analysis (non-urbanmodel); ii) including urban areas but only considering traditional soil forming factors (conventional model); and iii) including urban factors (urban-specific model). Total and specific carbon stocks, spatial variability represented by coefficient of variance (CV %) and the determination coefficient with a validation dataset were compared for the three models. The conventional model dramatically overestimated carbon stocks and underestimated of SOC's spatial variability. Total and specific carbon stocks estimated by non-urban model were 10–15% less than ones given by urban-specific model. The urban-specific performed best and explained more than 30% of total variability. Urban areas showed the highest spatial variability and specific carbon stocks, 90% ofwhichwas stored in subsoils. Evenwhen the high uncertainty of the absolute values is considered, urban areas contributed to regional carbon stocks. Considering urban-specific factors to estimate carbon stocks and their spatial variability is thus necessary.
    Impact of Matric Potential and Pore Size Distribution on Growth Dynamics of Filamentous and Non-Filamentous Soil Bacteria
    Wolf, A.B. ; Vos, M. de; Boer, W. de; Kowalchuk, G.A. - \ 2013
    PLoS ONE 8 (2013)12. - ISSN 1932-6203 - 8 p.
    organic-matter - fungi - respiration - diversity
    The filamentous growth form is an important strategy for soil microbes to bridge air-filled pores in unsaturated soils. In particular, fungi perform better than bacteria in soils during drought, a property that has been ascribed to the hyphal growth form of fungi. However, it is unknown if, and to what extent, filamentous bacteria may also display similar advantages over non-filamentous bacteria in soils with low hydraulic connectivity. In addition to allowing for microbial interactions and competition across connected micro-sites, water films also facilitate the motility of non-filamentous bacteria. To examine these issues, we constructed and characterized a series of quartz sand microcosms differing in matric potential and pore size distribution and, consequently, in connection of micro-habitats via water films. Our sand microcosms were used to examine the individual and competitive responses of a filamentous bacterium (Streptomyces atratus) and a motile rod-shaped bacterium (Bacillus weihenstephanensis) to differences in pore sizes and matric potential. The Bacillus strain had an initial advantage in all sand microcosms, which could be attributed to its faster growth rate. At later stages of the incubation, Streptomyces became dominant in microcosms with low connectivity (coarse pores and dry conditions). These data, combined with information on bacterial motility (expansion potential) across a range of pore-size and moisture conditions, suggest that, like their much larger fungal counterparts, filamentous bacteria also use this growth form to facilitate growth and expansion under conditions of low hydraulic conductivity. The sand microcosm system developed and used in this study allowed for precise manipulation of hydraulic properties and pore size distribution, thereby providing a useful approach for future examinations of how these properties influence the composition, diversity and function of soil-borne microbial communities.
    Comparison of static chambers to measure CH4 emissions from soils
    Pihlatie, M.K. ; Christiansen, J.R. ; Aaltonen, H. ; Korhonen, J.F.J. ; Nordbo, A. ; Rasilo, T. ; Benanti, G. ; Giebels, M. ; Helmy, M. ; Sheehy, J. ; Jones, S. ; Juszczak, R. ; Klefoth, R.R. ; Lobo-do-Vale, R. ; Rosa, A.P. ; Schreiber, P. ; Serca, D. ; Vicca, S. ; Wolf, B. ; Pumpanen, J. - \ 2013
    Agricultural and Forest Meteorology 171-172 (2013). - ISSN 0168-1923 - p. 124 - 136.
    gas-exchange - flux measurements - co2 efflux - atmosphere - respiration - apparatus - biases
    The static chamber method (non-flow-through-non-steady-state chambers) is the most common method to measure fluxes of methane (CH4) from soils. Laboratory comparisons to quantify errors resulting from chamber design, operation and flux calculation methods are rare. We tested fifteen chambers against four flux levels (FL) ranging from 200 to 2300 mu g CH4 M-2 II-1. The measurements were conducted on a calibration tank using three quartz sand types with soil porosities of 53% (dry fine sand, S1), 47% (dry coarse sand, S2), and 33% (wetted fine sand, S3). The chambers tested ranged from 0.06 to 1.8 m in height, and 0.02 to 0.195 m(3) in volume, 7 of them were equipped with a fan, and 1 with a vent-tube. We applied linear and exponential flux calculation methods to the chamber data and compared these chamber fluxes to the reference fluxes from the calibration tank. The chambers underestimated the reference fluxes by on average 33% by the linear flux calculation method (R-Iin), whereas the chamber fluxes calculated by the exponential flux calculation method (R-exp) did not significantly differ from the reference fluxes (p
    Complete genome sequence of Dehalobacter restrictus PER-K23T
    Kruse, T.K. ; Maillard, J. ; Goodwin, L.A. ; Woyke, T. ; Teshima, H. ; Bruce, D.C. ; Detter, J.C. ; Tapia, R. ; Han, C. ; Huntemann, M. ; Wei, C.L. ; Han, J. ; Chen, A. ; Kyrpides, N. ; Szeto, E. ; Markowitz, V. ; Ivanova, N. ; Pagani, I. ; Pati, A. ; Pitluck, S. ; Nolan, M. ; Holliger, C. ; Smidt, H. - \ 2013
    Standards in Genomic Sciences 8 (2013)3. - ISSN 1944-3277 - p. 375 - 388.
    tetrachloroethene reductive dehalogenase - hafniense strain tce1 - desulfitobacterium-hafniense - dehalococcoides-ethenogenes - rna genes - bacteria - respiration - geobacter - protein - halorespiration
    Dehalobacter restrictus strain PER-K23 (DSM 9455) is the type strain of the species Dehalobacter restrictus. D. restrictus strain PER-K23 grows by organohalide respiration, coupling the oxidation of H2 to the reductive dechlorination of tetra- or trichloroethene. Growth has not been observed with any other electron donor or acceptor, nor has fermentative growth been shown. Here we introduce the first full genome of a pure culture within the genus Dehalobacter. The 2,943,336 bp long genome contains 2,826 protein coding and 82 RNA genes, including 5 16S rRNA genes. Interestingly, the genome contains 25 predicted reductive dehalogenase genes, the majority of which appear to be full length. The reductive dehalogenase genes are mainly located in two clusters, suggesting a much larger potential for organohalide respiration than previously anticipated
    Leaf litter quality drives litter mixing effects through complementary resource use among detritivores
    Vos, V.C.A. ; Ruijven, J. van; Berg, M.P. ; Peeters, E.T.H.M. ; Berendse, F. - \ 2013
    Oecologia 173 (2013)1. - ISSN 0029-8549 - p. 269 - 280.
    species-diversity - ecosystem function - soil processes - decomposition - biodiversity - mixtures - forest - respiration - millipedes - richness
    To comprehend the potential consequences of biodiversity loss on the leaf litter decomposition process, a better understanding of its underlying mechanisms is necessary. Here, we hypothesize that positive litter mixture effects occur via complementary resource use, when litter species complement each other in terms of resource quality for detritivores. To investigate this, monocultures and mixtures of two leaf litter species varying in quality were allowed to decompose with and without a single macro-detritivore species (the terrestrial woodlice Oniscus asellus). Resource quality of the mixture was assessed by the mean concentration, the dissimilarity in absolute and relative concentrations, and the covariance between nitrogen (N), phosphorus (P) and calcium (Ca) supply. Our results clearly show that litter mixing effects were driven by differences in their resource quality for detritivores. In particular, complementary supply of N and P was a major driver of litter mixing effects. Interestingly, litter mixing effects caused by the addition of woodlice were predominantly driven by N dissimilarity, whereas in their absence, increased P concentration was the main driver of litter mixing effects. These results show that ultimately, litter diversity effects on decomposition may be driven by complementary resource use of the whole decomposer community (i.e., microbes and macro-detritivores).
    Oxygen and Heterotrophy Affect Calcification of the Scleractinian Coral Galaxea fascicularis
    Wijgerde, T.H.M. ; Jurriaans, S. ; Hoofd, M. ; Verreth, J.A.J. ; Osinga, R. - \ 2012
    PLoS ONE 7 (2012)12. - ISSN 1932-6203
    stylophora-pistillata - skeletal growth - artemia-salina - photosynthesis - zooxanthellae - reef - respiration - light - water - starvation
    Heterotrophy is known to stimulate calcification of scleractinian corals, possibly through enhanced organic matrix synthesis and photosynthesis, and increased supply of metabolic DIC. In contrast to the positive long-term effects of heterotrophy, inhibition of calcification has been observed during feeding, which may be explained by a temporal oxygen limitation in coral tissue. To test this hypothesis, we measured the short-term effects of zooplankton feeding on light and dark calcification rates of the scleractinian coral Galaxea fascicularis (n = 4) at oxygen saturation levels ranging from 13 to 280%. Significant main and interactive effects of oxygen, heterotrophy and light on calcification rates were found (three-way factorial repeated measures ANOVA, p
    CO2 in geventileerde bewaarplaatsen
    Lukasse, L.J.S. ; Verschoor, J.A. ; Otma, E.C. - \ 2012
    Wageningen UR Food & Biobased Research : Wageningen UR - Food & Biobased Research (Rapport / Wageningen UR Food & Biobased Research nr. 1315) - 13
    opslag - ademhaling - kooldioxide - groenten - fruit - akkerbouw - fruitteelt - storage - respiration - carbon dioxide - vegetables - fruit - arable farming - fruit growing
    Dit document beschrijft een eenvoudig model voor voorspelling van het verloop van de CO2 concentratie in bewaarplaatsen. Het model is tevens geïmplementeerd in een gebruiksvriendelijk excel-programma. Doel van dit programma is om in het ontwerp van bewaarplaatsen beter gefundeerde beslissingen te kunnen nemen over te installeren luchtverversingscapaciteit. Ter verificatie van belangrijke modelparameters is de ademhalingsactiviteit van een vijftal product/opslagtemperatuur-combinaties bepaald.
    Light intensity, photoperiod duration, daily light flux and coral growth of Galaxea fascicularis in an aquarium setting: a matter of photons?
    Schutter, M. ; Ven, R.M. ; Janse, M. ; Verreth, J.A.J. ; Wijffels, R.H. ; Osinga, R. - \ 2012
    Journal of the Marine Biological Association of The United Kingdom 92 (2012). - ISSN 0025-3154 - p. 703 - 712.
    reef-building corals - great-barrier-reef - stylophora-pistillata - scleractinian coral - hermatypic coral - carbonate chemistry - tissue retraction - calcification - photosynthesis - respiration
    Light is one of the most important abiotic factors influencing the (skeletal) growth of scleractinian corals. Light stimulates coral growth by the process of light-enhanced calcification, which is mediated by zooxanthellar photosynthesis. However, the quantity of light that is available for daily coral growth is not only determined by light intensity (i.e. irradiance), but also by photoperiod (i.e. the light duration time). Understanding and optimizing conditions for coral growth is essential for sustainable coral aquaculture. Therefore, in this study, the question was explored whether more light (i.e. more photons), presented either as irradiance or as light duration, would result in more growth. A series of nine genetically identical coral colonies of Galaxea fascicularis L. were cultured for a period of 18 weeks at different light duration times (8 hours 150 µE m-2 s-1:16 hours dark, 12 hours 150 µE m-2 s-1:12 hours dark, 16 hours 150 µE m-2 s-1:8 hours dark, 24 hours 150 µE m-2 s-1:0 hours dark) and different irradiance levels (8 hours 150 µE m-2 s-1:16 hours dark, 8 hours 225 µE m-2 s-1:16 hours dark and 8 hours 300 µE m-2 s-1:16 hours dark). Growth was determined every two weeks by measuring buoyant weight. Temperature, salinity and feeding levels were kept constant during the experiment. To detect possible acclimation of the corals to an increased light duration, rates of net photosynthesis and dark respiration were measured, hereby comparing coral colonies grown under an 8:16 hours light (150 µE m-2 s-1):dark cycle with corals grown under a 16:8 hours light (150 µE m-2 s-1):dark cycle. No increase in growth was detected with either increasing photoperiod or irradiance. Continuous lighting (24 hours 150 µE m-2 s-1:0 hours dark) resulted in immediate bleaching and the corals died after 14 weeks. Hourly photosynthetic rates were significantly reduced in the 16 hour light treatment compared to the 8 hour light treatment. As a result, daily net photosynthetic rates were not significantly different, which may explain the observed specific growth rates. Acclimation to photoperiod duration appeared neither to be mediated by changes in chlorophyll-a concentration nor zooxanthellae density. Based on the results of this study, we can conclude that the enhancing effect of light on coral growth is not only a matter of photons. Obviously, the availability of light was not limiting growth in these experiments and was probably in excess (i.e. stressful amounts). Other factors are discussed that play a role in determining growth rates and might explain our results.
    Longer growing seasons do not increase net carbon uptake in Northeastern Siberian tundra
    Parmentier, F.J.W. ; Molen, M.K. van der; Huissteden, J. van; Karsanaev, S. ; Kononov, A.V. ; Suzdalov, D. ; Maximov, T.C. ; Dolman, A.J. - \ 2011
    Journal of Geophysical Research: Biogeosciences 116 (2011). - ISSN 2169-8953 - 11 p.
    eddy covariance - ecosystem exchange - climate-change - arctic tundra - co2 exchange - respiration - flux - vegetation - dioxide - cycle
    With global warming, snowmelt is occurring earlier and growing seasons are becoming longer around the Arctic. It has been suggested that this would lead to more uptake of carbon due to a lengthening of the period in which plants photosynthesize. To investigate this suggestion, 8 consecutive years of eddy covariance measurements at a northeastern Siberian graminoid tundra site were investigated for patterns in net ecosystem exchange, gross primary production (GPP) and ecosystem respiration (Reco). While GPP showed no clear increase with longer growing seasons, it was significantly increased in warmer summers. Due to these warmer temperatures however, the increase in uptake was mostly offset by an increase in Reco. Therefore, overall variability in net carbon uptake was low, and no relationship with growing season length was found. Furthermore, the highest net uptake of carbon occurred with the shortest and the coldest growing season. Low uptake of carbon mostly occurred with longer or warmer growing seasons. We thus conclude that the net carbon uptake of this ecosystem is more likely to decrease rather than to increase under a warmer climate. These results contradict previous research that has showed more net carbon uptake with longer growing seasons. We hypothesize that this difference is due to site-specific differences, such as climate type and soil, and that changes in the carbon cycle with longer growing seasons will not be uniform around the Arctic
    Global patterns of land-atmosphere fluxes of carbon dioxide, latent heat, and sensible heat derived from eddy covariance, satellite, and meteorological observations
    Jung, M. ; Reichstein, M. ; Cescatti, A. ; Richardson, A.D. ; Arain, A. ; Arneth, A. ; Bernhofer, C. ; Bonal, D. ; Chen, J. ; Gianelle, D. ; Gobron, N. ; Lasslop, G. ; Moors, E.J. - \ 2011
    Journal of Geophysical Research: Biogeosciences 116 (2011)G3. - ISSN 2169-8953 - 16 p.
    net ecosystem exchange - energy-balance closure - co2 flux - primary productivity - vegetation model - climate - uncertainty - respiration - sensitivity - dynamics
    We upscaled FLUXNET observations of carbon dioxide, water, and energy fluxes to the global scale using the machine learning technique, model tree ensembles (MTE). We trained MTE to predict site-level gross primary productivity (GPP), terrestrial ecosystem respiration (TER), net ecosystem exchange (NEE), latent energy (LE), and sensible heat (H) based on remote sensing indices, climate and meteorological data, and information on land use. We applied the trained MTEs to generate global flux fields at a 0.5° × 0.5° spatial resolution and a monthly temporal resolution from 1982 to 2008. Cross-validation analyses revealed good performance of MTE in predicting among-site flux variability with modeling efficiencies (MEf) between 0.64 and 0.84, except for NEE (MEf = 0.32). Performance was also good for predicting seasonal patterns (MEf between 0.84 and 0.89, except for NEE (0.64)). By comparison, predictions of monthly anomalies were not as strong (MEf between 0.29 and 0.52). Improved accounting of disturbance and lagged environmental effects, along with improved characterization of errors in the training data set, would contribute most to further reducing uncertainties. Our global estimates of LE (158 ± 7 J × 1018 yr-1), H (164 ± 15 J × 1018 yr-1), and GPP (119 ± 6 Pg C yr-1) were similar to independent estimates. Our global TER estimate (96 ± 6 Pg C yr-1) was likely underestimated by 5–10%. Hot spot regions of interannual variability in carbon fluxes occurred in semiarid to semihumid regions and were controlled by moisture supply. Overall, GPP was more important to interannual variability in NEE than TER. Our empirically derived fluxes may be used for calibration and evaluation of land surface process models and for exploratory and diagnostic assessments of the biosphere
    Assessing the uncertainty of estimated annual totals of net ecosystem productivityAssessing the uncertainty of estimated annual totals of net ecosystem productivity: A practical approach applied to a mid latitude temperate pine forest
    Elbers, J.A. ; Jacobs, C.M.J. ; Kruijt, B. ; Jans, W.W.P. ; Moors, E.J. - \ 2011
    Agricultural and Forest Meteorology 151 (2011)12. - ISSN 0168-1923 - p. 1823 - 1830.
    eddy covariance technique - energy-balance closure - carboeurope flux data - quality-control - gas analyzers - co2 flux - exchange - respiration - errors
    Values for annual NEP of micrometeorological tower sites are usually published without an estimate of associated uncertainties. Few authors quantify total uncertainty of annual NEP. Moreover, different methods to assess total uncertainty are applied, usually addressing only one aspect of the uncertainty. This paper presents a robust and easy to apply method to quantify uncertainty of annual totals of Net Ecosystem Productivity (NEP), related to multiple factors involved therein. The method was applied to NEP observations for a Scots pine forest (Loobos) in the Netherlands. Total uncertainty of annual NEP for the Loobos site was on average ±32 g C m-2 a-1 (±8% of NEP), which is a quarter of the standard deviation of annual NEP (127 g C m-2 a-1). Highlights - ¿ A robust method is presented to quantify uncertainty of annual totals of net ecosystem productivity (NEP). ¿ The method contains uncertainty estimates for the most important known components of the total uncertainty: measurement error and flux calculation uncertainty, self-heating correction uncertainty, u* threshold uncertainty, statistical selection uncertainty and gap-filling uncertainty. ¿ The uncertainties associated with the friction velocity threshold criterion and measurement error and flux calculation are substantial and much higher than the other uncertainties. ¿ Total uncertainty of NEP for the Loobos site was on average ±32 g C m-2 a-1 (±8% of NEP). Abbreviations - NEP, annual net ecosystem productivity (g C m-2 a-1 positive values represent accumulation of carbon by the ecosystem); Fec, eddy-covariance flux (µmol m-2 s-1 positive values represent carbon released to the atmosphere); Fs, storage flux (µmol m-2 s-1 positive values represent carbon released to the atmosphere); NEE, net ecosystem exchange (µmol m-2 s-1 positive values represent carbon released to the atmosphere)
    First pioneering laboratory experiments on filtration, respiration and growth of the razor clam (Ensis directus, Conrad)
    Kamermans, P. ; Brummelhuis, E.B.M. ; Wijsman, J.W.M. - \ 2011
    Yerseke : IMARES (Report / IMARES Wageningen UR C115/11) - 48
    ensis - voedsel - ademhaling - filtratie - groeitempo - mariene ecologie - noordzee - ensis - food - respiration - filtration - growth rate - marine ecology - north sea
    In Dutch marine circumstances, sand extraction releases silt into the water column. The extra silt can reduce light penetration into the water and consequently algal growth. To predict potential effects of an expansion of sand extraction activities it is necessary to know possible impacts on the environment. Ensis directus, a dominant species web of the North Sea coastal zone, has a key position in the food web. Therefore, it was selected as model species in this study to predict the effects of the reduced food conditions due to sand extraction on the growth of E. directus. A DEB (Dynamic Energy Budget) model is in development. This study describes the basic experiments that have been done to determine empirical relations between clam size or food concentration and filtration, respiration and growth rates necessary for the DEB modelling. Also, the basic values on physiology itself have their value because little is known on this species. Filtration and respiration rates were measured at four food levels (2, 5, 20 and 40 μg chlorophyll a/l). Clam shell length varied from 42 to 135 mm. Filtration rate decreased with an increase in clam size from maximally 3.3 lh-1 g-1 ash-free dry weight (ADW) to 0. lh-1 g-1 ADW. There was no relation between food concentration on filtration rate. Respiration rates showed a similar decrease with clam size from maximally 5000 mg O2 lh-1 g-1 ADW to 1500 mg O2 lh-1 g-1 ADW. In addition, an increase in respiration rate was found with an increase in food concentration. In the growth experiment five food levels were tested (0, 2, 5, 20 and 40 μg chlorophyll a/l).Clams smaller than 75 mm shell length showed more growth (up to 1% increase in wet weight (WW) per day or 0.3% shell length per day) than larger clams (maximally 0.16% increase in WW per day or 0.01% shell length per day). Growth rates showed an increase with increased food concentration.
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