Revisiting the role of high-energy Pacific events in the environmental and cultural history of Easter Island (Rapa Nui)

Margalef O., Álvarez-Gómez J.A., Pla-Rabes S., Cañellas-Boltà N., Rull V., Sáez A., Geyer A., Peñuelas J., Sardans J., Giralt S. (2018) Revisiting the role of high-energy Pacific events in the environmental and cultural history of Easter Island (Rapa Nui). Geographical Journal. : 0-0.
Enlace
Doi: 10.1111/geoj.12253

Resumen:

Pacific islands are spread over thousands of kilometres of the Pacific Basin and are characterised by similar ecological features but very diverse geologic origins, from steep volcanoes to flat coral atolls. Several climatic phases have been shared across the region within the last 1,000 years. Numerous and abrupt societal and cultural changes during the same period have been described for islands separated by thousands of kilometres. Conspicuous societal changes have been exclusively attributed to the main climatic patterns (changes in precipitation and temperature). The possible role of tsunamis and the occurrence of large volcanic eruptions as regional societal modulators, however, have traditionally received little attention from archaeologists, mainly due to the difficulty of recognising them in the sedimentary and geomorphological records. We explore the potential influence of the most important high-energy events in the Pacific on Polynesian societal changes, with a special focus on Easter Island. For example, the extreme Samalas eruption in AD 1257 may have been an indirect driver of the sudden population decline, land degradation and decreased food resources on many Pacific islands between AD 1250 and 1300, and the Kuwae eruption in AD 1450 may have triggered the synchronous end of long voyaging expeditions across the Pacific. Important palaeo-tsunamis have had unquestionable impacts on coastal and seafaring societies. A direct effect of the main eruptions of the last millennia (AD 1257 and 1453) on Easter Island has not yet been identified by any record, but we have calculated the likelihood of destructive tsunamis with an estimated period of recurrence for large events of less than a century. This insight is new and needs to be taken into account to complement what we already know about Easter Island's cultural history and archaeological sites, especially those in vulnerable coastal locations. © 2018 Royal Geographical Society (with the Institute of British Geographers).

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Coping with iron limitation: a metabolomic study of Synechocystis sp. PCC 6803

Rivas-Ubach A., Poret-Peterson A.T., Peñuelas J., Sardans J., Pérez-Trujillo M., Legido-Quigley C., Oravec M., Urban O., Elser J.J. (2018) Coping with iron limitation: a metabolomic study of Synechocystis sp. PCC 6803. Acta Physiologiae Plantarum. 40: 0-0.
Enlace
Doi: 10.1007/s11738-018-2603-1

Resumen:

Iron (Fe) is a key element for all living systems, especially for photosynthetic organisms because of its important role in the photosynthetic electron transport chain. Fe limitation in cyanobacteria leads to several physiological and morphological changes. However, the overall metabolic responses to Fe limitation are still poorly understood. In this study, we integrated elemental, stoichiometric, macromolecular, and metabolomic data to shed light on the responses of Synechocystis sp. PCC 6803, a non-N2-fixing freshwater cyanobacterium, to Fe limitation. Compared to Synechocystis growing at nutrient replete conditions, Fe-limited cultures had lower growth rates and amounts of chlorophyll a, RNA, RNA:DNA, C, N, and P, and higher ratios of protein:RNA, C:N, C:P, and N:P, in accordance with the growth rate hypothesis which predicts faster growing organisms will have decreased biomass RNA contents and C:P and N:P ratios. Fe-limited Synechocystis had lower amounts Fe, Mn, and Mo, and higher amount of Cu. Several changes in amino acids of cultures growing under Fe limitation suggest nitrogen limitation. In addition, we found substantial increases in stress-related metabolites in Fe-limited cyanobacteria such antioxidants. This study represents an advance in understanding the stoichiometric, macromolecular, and metabolic strategies that cyanobacteria use to cope with Fe limitation. This information, moreover, may further understanding of changes in cyanobacterial functions under scenarios of Fe limitation in aquatic ecosystems. © 2018, Franciszek Górski Institute of Plant Physiology, Polish Academy of Sciences, Kraków.

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Using research networks to create the comprehensive datasets needed to assess nutrient availability as a key determinant of terrestrial carbon cycling

Vicca S., Stocker B.D., Reed S., Wieder W.R., Bahn M., Fay P.A., Janssens I.A., Lambers H., Peñuelas J., Piao S., Rebel K.T., Sardans J., Sigurdsson B.D., Van Sundert K., Wang Y.-P., Zaehle S., Ciais P. (2018) Using research networks to create the comprehensive datasets needed to assess nutrient availability as a key determinant of terrestrial carbon cycling. Environmental Research Letters. 13: 0-0.
Enlace
Doi: 10.1088/1748-9326/aaeae7

Resumen:

A wide range of research shows that nutrient availability strongly influences terrestrial carbon (C) cycling and shapes ecosystem responses to environmental changes and hence terrestrial feedbacks to climate. Nonetheless, our understanding of nutrient controls remains far from complete and poorly quantified, at least partly due to a lack of informative, comparable, and accessible datasets at regional-to-global scales. A growing research infrastructure of multi-site networks are providing valuable data on C fluxes and stocks and are monitoring their responses to global environmental change and measuring responses to experimental treatments. These networks thus provide an opportunity for improving our understanding of C-nutrient cycle interactions and our ability to model them. However, coherent information on how nutrient cycling interacts with observed C cycle patterns is still generally lacking. Here, we argue that complementing available C-cycle measurements from monitoring and experimental sites with data characterizing nutrient availability will greatly enhance their power and will improve our capacity to forecast future trajectories of terrestrial C cycling and climate. Therefore, we propose a set of complementary measurements that are relatively easy to conduct routinely at any site or experiment and that, in combination with C cycle observations, can provide a robust characterization of the effects of nutrient availability across sites. In addition, we discuss the power of different observable variables for informing the formulation of models and constraining their predictions. Most widely available measurements of nutrient availability often do not align well with current modelling needs. This highlights the importance to foster the interaction between the empirical and modelling communities for setting future research priorities. © 2018 The Author(s). Published by IOP Publishing Ltd.

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EFFECTS OF FERTILIZATION ON POREWATER NUTRIENTS, GREENHOUSE-GAS EMISSIONS AND RICE PRODUCTIVITY IN A SUBTROPICAL PADDY FIELD

WANG W., SARDANS J., WANG C., TONG C., JI Q., PEÑUELAS J. (2018) EFFECTS OF FERTILIZATION ON POREWATER NUTRIENTS, GREENHOUSE-GAS EMISSIONS AND RICE PRODUCTIVITY IN A SUBTROPICAL PADDY FIELD. Experimental Agriculture. : 1-17.
Enlace
Doi: 10.1017/S0014479718000078

Resumen:

Suitable fertilization is crucial for the sustainability of rice production and for the potential mitigation of global warming. The effects of fertilization on porewater nutrients and greenhouse-gas fluxes in cropland, however, remain poorly known. We studied the effects of no fertilization (control), standard fertilization and double fertilization on the concentrations of porewater nutrients, greenhouse-gas fluxes and emissions, and rice yield in a subtropical paddy in southeastern China. Double fertilization increased dissolved NH4 + in porewater. Mean CO2 and CH4 emissions were 13.5% and 7.4%, and 20.4% and 39.5% higher for the standard and double fertilizations, respectively, than the control. N2O depositions in soils were 61% and 101% higher for the standard and double fertilizations, respectively, than the control. The total global warming potentials (GWPs) for all emissions were 14.1% and 10.8% higher for the standard and double fertilizations, respectively than the control, with increasing contribution of CH4 with fertilization and a CO2 contribution > 85%. The total GWPs per unit yield were significantly higher for the standard and double fertilizations than the control by 7.3% and 10.9%, respectively. The two levels of fertilization did not significantly increase rice yield. Prior long-term fertilization in the paddy (about 20 years with annual doses of 95 kg N ha−1, 70 kg P2O5 ha−1 and 70 kg K2O ha−1) might have prevented these fertilizations from increasing the yield. However, fertilizations increased greenhouse-gas emissions. This situation is common in paddy fields in subtropical China, suggesting a saturation of soil nutrients and the necessity to review current fertilization management. These areas likely suffer from unnecessary nutrient leaching and excessive greenhouse-gas emissions. These results provide a scientific basis for continued research to identify an easy and optimal fertilization management solution. Copyright © Cambridge University Press 2018

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Effect of simulated acid rain on CO2, CH4 and N2O fluxes and rice productivity in a subtropical Chinese paddy field

Wang C., Wang W., Sardans J., An W., Zeng C., Abid A.A., Peñuelas J. (2018) Effect of simulated acid rain on CO2, CH4 and N2O fluxes and rice productivity in a subtropical Chinese paddy field. Environmental Pollution. 243: 1196-1205.
Enlace
Doi: 10.1016/j.envpol.2018.08.103

Resumen:

The need of more food production, an increase in acidic deposition and the large capacity of paddy to emit greenhouse gases all coincide in several areas of China. Studying the effects of acid rain on the emission of greenhouse gases and the productivity of rice paddies are thus important, because these effects are currently unknown. We conducted a field experiment for two rice croppings (early and late paddies independent experiment) to determine the effects of simulated acid rain (control, normal rain, and treatments with rain at pH of 4.5, 3.5 and 2.5) on the fluxes of CO2, CH4 and N2O and on rice productivity in subtropical China. Total CO2 fluxes at pHs of 4.5, 3.5 and 2.5 were 10.3, 9.7 and 3.2% lower in the early paddy and 28.3, 14.8 and 6.8% lower in the late paddy, respectively, than the control. These differences from the control were significant for pH 3.5 and 4.5. Total CH4 fluxes at pHs of 4.5, 3.5 and 2.5 were 50.4, 32.9 and 25.2% lower in the early paddy, respectively, than the control. pH had no significant effect on CH4 flux in the late paddy or for total (early + late) emissions. N2O flux was significantly higher at pH 2.5 than 3.5 and 4.5 but did not differ significantly from the flux in the control. Global-warming potentials (GWPs) were lower than the control at pH 3.5 and 4.5 but not 2.5, whereas rice yield was not appreciably affected by pH. Acid rain (between 3.5 and 4.5) may thus significantly affect greenhouse gases emissions by altering soil properties such as pH and nutrient pools, whereas highly acidic rain (pH 2.5) could increase GWPs (but not significantly), probably partially due to an increase in the production of plant litter. © 2018 Elsevier Ltd

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Shifts in plant and soil C, N and P accumulation and C:N:P stoichiometry associated with flooding intensity in subtropical estuarine wetlands in China

Wang W., Sardans J., Wang C., Zeng C., Tong C., Bartrons M., Asensio D., Peñuelas J. (2018) Shifts in plant and soil C, N and P accumulation and C:N:P stoichiometry associated with flooding intensity in subtropical estuarine wetlands in China. Estuarine, Coastal and Shelf Science. 215: 172-184.
Enlace
Doi: 10.1016/j.ecss.2018.09.026

Resumen:

Flooding caused by rising sea levels can influence the biogeochemistry of estuarine wetland ecosystems. We studied the relationships of higher flooding intensity with soil carbon (C), nitrogen (N) and phosphorus (P) concentrations in communities of the native sedge Cyperus malaccensis var. brevifolius Boecklr. in the wetlands of the Minjiang River estuary in China. The aboveground and total biomasses of C. malaccensis were higher in high-flooding habitats than in intermediate- and low-flooding habitats. These differences in plant biomass were accompanied by a lower N:P ratio in the aboveground biomass and a higher N:P ratio in the belowground biomass. Higher intensities of flooding were associated with higher soil N and P concentrations in intermediate and deep soil layers. The higher P concentration under flooding was mainly associated with the higher clay content, whereas the higher N concentration was associated with higher salinity. Flooding intensity did not have a net total effect on soil total C concentration. The positive direct effect of flooding intensity on total soil C concentration was counteracted by its positive effects on CH4 emissions and soil salinity. The results suggest that C. malaccensis wetlands will be able to maintain and even increase the current C, N and P storage capacity of the ecosystem under moderate increases of flooding in the Minjiang River estuary. © 2018

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STEEL SLAG AMENDMENT INCREASES NUTRIENT AVAILABILITY and RICE YIELD in A SUBTROPICAL PADDY FIELD in CHINA

Wang W., Sardans J., Wang C., Zeng C., Tong C., Bartrons M., Peñuelas J. (2018) STEEL SLAG AMENDMENT INCREASES NUTRIENT AVAILABILITY and RICE YIELD in A SUBTROPICAL PADDY FIELD in CHINA. Experimental Agriculture. 54: 842-856.
Enlace
Doi: 10.1017/S0014479717000412

Resumen:

Rice is the main food for most of the human population, so sustainable rice production is very important for food security. The fertility of the soil in paddy fields is the key factor controlling rice growth and production. Steel slag amendment is becoming an effective method to increase the soil fertility, stabilize rice production and reduce greenhouse-gas emissions in Asiatic paddy fields (i.e. Korea, Japan, Bangladesh and China). We studied the relationships of steel slag amendment with plant-soil nutrient allocation, stoichiometry and rice yield in a paddy field in subtropical China. Amendment was associated with higher soil N and P availability, lower available-N:available-P ratio and higher available Ca and Si concentrations. Increases in P, Ca and Mg availability were correlated with high yields. High yields under steel slag amendment were also associated with high foliar and stem N and P concentrations and lower N:P ratios and with high shoot/root N and P concentration ratios, traits that are typically associated with productive ecosystems able to support species with high growth rates. The positive correlation between steel slag application and yield was partially due to an indirect effect (35% of the total effect) of enhancement of soil Ca, Si and P availability, which were positively correlated with yield. Steel slag amendment in this paddy field increased plant growth and yield by enhancing nutrient availability, altering soil and plant stoichiometry and shifting stem:root nutrient allocation. © 2017 Cambridge University Press.

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Storage and release of nutrients during litter decomposition for native and invasive species under different flooding intensities in a Chinese wetland

Wang W., Wang C., Sardans J., Tong C., Ouyang L., Asensio D., Gargallo-Garriga A., Peñuelas J. (2018) Storage and release of nutrients during litter decomposition for native and invasive species under different flooding intensities in a Chinese wetland. Aquatic Botany. 149: 5-16.
Enlace
Doi: 10.1016/j.aquabot.2018.04.006

Resumen:

Projections of climate change impacts over the coming decades suggest that rising sea level will flood coastal wetlands. We studied the impacts of three intensities of flooding on litter decomposition in the native Cyperus malaccensis, and the invasives Spartina alterniflora and Phragmites australis in Shanyutan wetland (Minjiang River estuary, China). Invasive species had larger C, N and P stocks in plant-litter compartments and higher fluxes among plant-litter-soil, which increased with flooding intensity. Litter mass remaining (% of initial mass) were correlated with the N:P ratio in remaining litter, consistently with the N-limitation in this wetland. P. australis had the highest accumulated N release (P < 0.001) in all flooding intensities, whereas C. malaccensis had higher N accumulated release than S. alternifolia but only at low flooding intensity. At high flooding intensity, the N released in the first year of litter decomposition (g m−2 y−1) were 9.56 ± 0.21, 2.38 ± 0.18 and 1.92 ± 0.03 for P. australis, S. alternifolia and C. malaccensis, respectively. The higher rates of nutrient release from litter decomposition in invasive species provided better nutrient supply during the growing season coinciding with the initial phases of decomposition. Thus, this study shows that invasive species may gain a competitive advantage over the native C. malaccensis under the projected scenarios of sea level rises. © 2018 Elsevier B.V.

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Soil Methane Production, Anaerobic and Aerobic Oxidation in Porewater of Wetland Soils of the Minjiang River Estuarine, China

Wang W., Zeng C., Sardans J., Wang C., Tong C., Peñuelas J. (2018) Soil Methane Production, Anaerobic and Aerobic Oxidation in Porewater of Wetland Soils of the Minjiang River Estuarine, China. Wetlands. : 1-14.
Enlace
Doi: 10.1007/s13157-018-1006-9

Resumen:

Wetlands are important sources of methane emission. Anaerobic oxidation, aerobic oxidation and production of methane as well as dissolved methane are important processes of methane metabolism. We studied methane metabolism and the soil influencing factors. Potential soil methane production, anaerobic oxidation and aerobic oxidation rates, and dissolved methane in soil porewater changed seasonally and the annual average was 21.1 ± 5.1 μg g−1d−1, 11.0 ± 3.9 μg g−1d−1, 20.9 ± 5.8 μg g−1d−1, and 62.9 ± 20.6 μmol l−1, respectively. Potential soil methane production and anaerobic and aerobic oxidation were positively correlated among themselves and with soil pH and negatively correlated with soil redox potential (Eh). Potential soil methane production and aerobic and anaerobic oxidation rates were negatively related to pore soil methane concentration. Thus, the more water-saturated the soil (the lower Eh), the higher its capacity to produce methane. The potential soil capacity for methane oxidation was higher both in the same anaerobic circumstances and when the soil was suddenly subjected to aerobic conditions. The results of this study suggested a buffer effect in the methane balance in wetland areas. The environmental circumstances favoring methane production are also favorable for anaerobic methane oxidation. © 2018 Society of Wetland Scientists

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GOLUM-CNP v1.0: A data-driven modeling of carbon, nitrogen and phosphorus cycles in major terrestrial biomes

Wang Y., Ciais P., Goll D., Huang Y., Luo Y., Wang Y.-P., Bloom A.A., Broquet G., Hartmann J., Peng S., Penuelas J., Piao S., Sardans J., Stocker B.D., Wang R., Zaehle S., Zechmeister-Boltenstern S. (2018) GOLUM-CNP v1.0: A data-driven modeling of carbon, nitrogen and phosphorus cycles in major terrestrial biomes. Geoscientific Model Development. 11: 3903-3928.
Enlace
Doi: 10.5194/gmd-11-3903-2018

Resumen:

Global terrestrial nitrogen (N) and phosphorus (P) cycles are coupled to the global carbon (C) cycle for net primary production (NPP), plant C allocation, and decomposition of soil organic matter, but N and P have distinct pathways of inputs and losses. Current C-nutrient models exhibit large uncertainties in their estimates of pool sizes, fluxes, and turnover rates of nutrients, due to a lack of consistent global data for evaluating the models. In this study, we present a new model-data fusion framework called the Global Observation-based Land-ecosystems Utilization Model of Carbon, Nitrogen and Phosphorus (GOLUM-CNP) that combines the CARbon DAta MOdel fraMework (CARDAMOM) data-constrained C-cycle analysis with spatially explicit data-driven estimates of N and P inputs and losses and with observed stoichiometric ratios. We calculated the steady-state N- and P-pool sizes and fluxes globally for large biomes. Our study showed that new N inputs from biological fixation and deposition supplied > 20 % of total plant uptake in most forest ecosystems but accounted for smaller fractions in boreal forests and grasslands. New P inputs from atmospheric deposition and rock weathering supplied a much smaller fraction of total plant uptake than new N inputs, indicating the importance of internal P recycling within ecosystems to support plant growth. Nutrient-use efficiency, defined as the ratio of gross primary production (GPP) to plant nutrient uptake, were diagnosed from our model results and compared between biomes. Tropical forests had the lowest N-use efficiency and the highest P-use efficiency of the forest biomes. An analysis of sensitivity and uncertainty indicated that the NPP-allocation fractions to leaves, roots, and wood contributed the most to the uncertainties in the estimates of nutrient-use efficiencies. Correcting for biases in NPP-allocation fractions produced more plausible gradients of N- and P-use efficiencies from tropical to boreal ecosystems and highlighted the critical role of accurate measurements of C allocation for understanding the N and P cycles. © Author(s) 2018.

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