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.
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Doi: 10.1016/j.ecss.2018.09.026

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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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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.
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Doi: 10.1016/j.aquabot.2018.04.006

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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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Global patterns of phosphatase activity in natural soils

Margalef O., Sardans J., Fernández-Martínez M., Molowny-Horas R., Janssens I.A., Ciais P., Goll D., Richter A., Obersteiner M., Asensio D., Peñuelas J. (2017) Global patterns of phosphatase activity in natural soils. Scientific Reports. 7: 0-0.
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Doi: 10.1038/s41598-017-01418-8

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Soil phosphatase levels strongly control the biotic pathways of phosphorus (P), an essential element for life, which is often limiting in terrestrial ecosystems. We investigated the influence of climatic and soil traits on phosphatase activity in terrestrial systems using metadata analysis from published studies. This is the first analysis of global measurements of phosphatase in natural soils. Our results suggest that organic P (Porg), rather than available P, is the most important P fraction in predicting phosphatase activity. Structural equation modeling using soil total nitrogen (TN), mean annual precipitation, mean annual temperature, thermal amplitude and total soil carbon as most available predictor variables explained up to 50% of the spatial variance in phosphatase activity. In this analysis, Porg could not be tested and among the rest of available variables, TN was the most important factor explaining the observed spatial gradients in phosphatase activity. On the other hand, phosphatase activity was also found to be associated with climatic conditions and soil type across different biomes worldwide. The close association among different predictors like Porg, TN and precipitation suggest that P recycling is driven by a broad scale pattern of ecosystem productivity capacity. © 2017 The Author(s).

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Impacts of global change on Mediterranean forests and their services

Peñuelas, J., Sardans, J., Filella, I., Estiarte, M., Llusià, J., Ogaya, R., Carnicer, J., Bartrons, M., Rivas-Ubach, A., Grau, O., Peguero, G., Margalef, O., Pla-Rabés, S., Stefanescu, C., Asensio, D., Preece, C., Liu, L., Verger, A., Barbeta, A., Achotegui-Castells, A., Gargallo-Garriga, A., Sperlich, D., Farré-Armengol, G., Fernández-Martínez, M., Liu, D., Zhang, C., Urbina, I., Camino-Serrano, M., Vives-Ingla, M., Stocker, B.D., Balzarolo, M., Guerrieri, R., Peaucelle, M., Marañón-Jiménez, S., Bórnez-Mejías, K., Mu, Z., Descals, A., Castellanos, A., Terradas, J. (2017) Impacts of global change on Mediterranean forests and their services. Forests. 8: 0-0.
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Doi: 10.3390/f8120463

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Relationships between the potential production of the greenhouse gases CO<inf>2</inf>, CH<inf>4</inf> and N<inf>2</inf>O and soil concentrations of C, N and P across 26 paddy fields in southeastern China

Wang, W., Sardans, J., Wang, C., Zeng, C., Tong, C., Asensio, D., Peñuelas, J. (2017) Relationships between the potential production of the greenhouse gases CO2, CH4 and N2O and soil concentrations of C, N and P across 26 paddy fields in southeastern China. Atmospheric Environment. : 0-0.
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Doi: 10.1016/j.atmosenv.2017.06.023

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Assessment of the impacts of climate change on Mediterranean terrestrial ecosystems based on data from field experiments and long-term monitored field gradients in Catalonia

Peñuelas, J., Sardans, J., Filella, I., Estiarte, M., Llusià, J., Ogaya, R., Carnicer, J., Bartrons, M., Rivas-Ubach, A., Grau, O., Peguero, G., Margalef, O., Pla-Rabés, S., Stefanescu, C., Asensio, D., Preece, C., Liu, L., Verger, A., Rico, L., Barbeta, A., Achotegui-Castells, A., Gargallo-Garriga, A., Sperlich, D., Farré-Armengol, G., Fernández-Martínez, M., Liu, D., Zhang, C., Urbina, I., Camino, M., Vives, M., Nadal-Sala, D., Sabaté, S., Gracia, C., Terradas, J. (2016) Assessment of the impacts of climate change on Mediterranean terrestrial ecosystems based on data from field experiments and long-term monitored field gradients in Catalonia. Environmental and Experimental Botany. : 0-0.
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Doi: 10.1016/j.envexpbot.2017.05.012

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Organic cultivation of jasmine and tea increases carbon sequestration by changing plant and soil stoichiometry

Wang W., Min Q., Sardans J., Wang C., Asensio D., Bartrons M., Peñuelas J. (2016) Organic cultivation of jasmine and tea increases carbon sequestration by changing plant and soil stoichiometry. Agronomy Journal. 108: 1636-1648.
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Doi: 10.2134/agronj2015.0559

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Organic cultivation methods would be a good alternative to conventional cultivation, avoiding the use of industrial fertilizer and reducing the risk of eutrophication, but its impacts on soil elemental composition and stoichiometry warrants to be clearly stated. This study was conducted to determine the effects of long-term organic cultivation on soil elemental composition, stoichiometry, and C storing capacity and CO2 emissions in the plant-soil systems of jasmine (Jasminum spp.) and tea [Camellia sinensis (L.) Ktze.] plantations in Fujian and other regions in China. We examined the impact of organic cultivation on the concentrations, contents and stoichiometric relationships among C, N, P, and K. Organic cultivation was associated with lower plant N and P concentrations, and P mineralomasses and with higher total plant C/N, C/P, C/K, and N/P ratios and higher soil N and P concentrations and contents at some depths. Organic cultivation was thus associated with a shift of P from plants to soil and with a higher nutrient-use efficiency in biomass production, mainly of P. Soil CO2 emissions were higher under organic cultivation, but the soil was able to accumulate more C with no changes in C storage in plant biomass, suggesting that organic cultivation could increase the overall C sequestration, thereby mitigating climate change and enhancing soil nutrient content. Our results thus showed that the organic cultivation of jasmine and tea in Fujian can improve soil fertility and C accumulation, reduce the use of industrial fertilizers and phytosanitary products, and improve product quality without loss of economical profits. © 2016 by the American Society of Agronomy.

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Ecological stoichiometry of C, N, and P of invasive Phragmites australis and native Cyperus malaccensis species in the Minjiang River tidal estuarine wetlands of China

Wang W.Q., Sardans J., Wang C., Zeng C.S., Tong C., Asensio D., Penuelas J. (2015) Ecological stoichiometry of C, N, and P of invasive Phragmites australis and native Cyperus malaccensis species in the Minjiang River tidal estuarine wetlands of China. Plant Ecology. : 0-0.
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Doi: 10.1007/s11258-015-0469-5

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Tidal estuarine wetlands of China are rich in plant diversity, but several global change drivers, such as species invasion, are currently affecting the biogeochemical cycles of these ecosystems. We seasonally analyzed the carbon (C), nitrogen (N), and phosphorus (P) concentrations in litters and soils and in leaves, stems, and roots of the C3 invasive species Phragmites australis (Cav.) Trin. ex Steud. and of the C4 native species Cyperus malaccensis var. brevifolius Boeckeler to investigate the effect of C3 plant invasion on C, N, and P stoichiometry in the C4 plant-dominated tidal wetlands of the Minjiang River. When averaged across seasons, the invasive species P. australis had higher N concentrations and lower P concentrations in leaves than the native species C. malaccensis. N and P concentrations were lower in litter (stem and leaf), whereas C concentrations in leaf litter were higher in P. australis than in C. malaccensis. The C, N, and P concentrations of the soil also did not differ, but plants had a lower C:N and much higher N:P ratios than soils. Root C:P and N:P ratios were lower in the growing season both in the invasive and the native species. The leaf C:N, C:P and N:P ratios peaked in summer. The invasive species had lower C:N ratio in leaves and roots, and higher N:P ratios in all biomass organs and litter than the native species, an effect related with the higher N-resorption capacity of the invasive species. Interspecific differences in C:N, C:P, and N:P ratios may likely reflect the differences in plant morphology, nutrient-use efficiency, and photosynthetic capacity between the C3 (P. australis) and C4 (C. malaccensis) plants. Our results generally suggested that the success of P. australis in these wetlands was related to its slow growth and higher resorption capacity of N and P. This implies a more conservative use of limited nutrients, particularly N, by P. australis, and to higher N concentration in its biomass thus potentially contributing to its invasiveness in these estuarine wetlands. © 2015 Springer Science+Business Media Dordrecht

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Global biodiversity, stoichiometry and ecosystem function responses to human-induced C-N-P imbalances

Carnicer J., Sardans J., Stefanescu C., Ubach A., Bartons M., Asensio D., Penuelas J. (2014) Global biodiversity, stoichiometry and ecosystem function responses to human-induced C-N-P imbalances. Journal of Plant Physiology. : 0-0.
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Doi: 10.1016/j.jplph.2014.07.022

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Global change analyses usually consider biodiversity as a global asset that needs to be preserved. Biodiversity is frequently analysed mainly as a response variable affected by diverse environmental drivers. However, recent studies highlight that gradients of biodiversity are associated with gradual changes in the distribution of key dominant functional groups characterized by distinctive traits and stoichiometry, which in turn often define the rates of ecosystem processes and nutrient cycling. Moreover, pervasive links have been reported between biodiversity, food web structure, ecosystem function and species stoichiometry. Here we review current global stoichiometric gradients and how future distributional shifts in key functional groups may in turn influence basic ecosystem functions (production, nutrient cycling, decomposition) and therefore could exert a feedback effect on stoichiometric gradients. The C-N-P stoichiometry of most primary producers (phytoplankton, algae, plants) has been linked to functional trait continua (i.e. to major axes of phenotypic variation observed in inter-specific analyses of multiple traits). In contrast, the C-N-P stoichiometry of higher-level consumers remains less precisely quantified in many taxonomic groups. We show that significant links are observed between trait continua across trophic levels. In spite of recent advances, the future reciprocal feedbacks between key functional groups, biodiversity and ecosystem functions remain largely uncertain. The reported evidence, however, highlights the key role of stoichiometric traits and suggests the need of a progressive shift towards an ecosystemic and stoichiometric perspective in global biodiversity analyses.

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