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Your search keyword '"Ramirez-Rojas, Irene"' showing total 2 results
Start Over Author "Ramirez-Rojas, Irene" Topic nitrogen
2 results on '"Ramirez-Rojas, Irene"'

1. Phosphorus scarcity contributes to nitrogen limitation in lowland tropical rainforests.

Author

Vallicrosa H, Lugli LF, Fuchslueger L, Sardans J, Ramirez-Rojas I, Verbruggen E, Grau O, Bréchet L, Peguero G, Van Langenhove L, Verryckt LT, Terrer C, Llusià J, Ogaya R, Márquez L, Roc-Fernández P, Janssens I, and Peñuelas J

Subjects
Phosphorus, Tropical Climate, Forests, Trees, Soil, Rainforest, Nitrogen
Abstract

There is increasing evidence to suggest that soil nutrient availability can limit the carbon sink capacity of forests, a particularly relevant issue considering today's changing climate. This question is especially important in the tropics, where most part of the Earth's plant biomass is stored. To assess whether tropical forest growth is limited by soil nutrients and to explore N and P limitations, we analyzed stem growth and foliar elemental composition of the five stem widest trees per plot at two sites in French Guiana after 3 years of nitrogen (N), phosphorus (P), and N + P addition. We also compared the results between potential N-fixer and non-N-fixer species. We found a positive effect of N fertilization on stem growth and foliar N, as well as a positive effect of P fertilization on stem growth, foliar N, and foliar P. Potential N-fixing species had greater stem growth, greater foliar N, and greater foliar P concentrations than non-N-fixers. In terms of growth, there was a negative interaction between N-fixer status, N + P, and P fertilization, but no interaction with N fertilization. Because N-fixing plants do not show to be completely N saturated, we do not anticipate N providing from N-fixing plants would supply non-N-fixers. Although the soil-age hypothesis only anticipates P limitation in highly weathered systems, our results for stem growth and foliar elemental composition indicate the existence of considerable N and P co-limitation, which is alleviated in N-fixing plants. The evidence suggests that certain mechanisms invest in N to obtain the scarce P through soil phosphatases, which potentially contributes to the N limitation detected by this study., (© 2023 The Authors. Ecology published by Wiley Periodicals LLC on behalf of The Ecological Society of America.)

Published
2023
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2. Disentangling drought and nutrient effects on soil carbon dioxide and methane fluxes in a tropical forest

Author

Bréchet, Laëtitia, Dr. Elodie A. Courtois, Saint-Germain, Thomas, Prof. Ivan A. Janssens, Dr. Dolores Asensio, Ramirez-Rojas, Irene, Dr. Jennifer L. Soong, Langenhove, Leandro Van, Prof. Erik Verbruggen, and Dr. Clément Stahl

Subjects
2. Zero hunger, Carbon dioxide, Drought, Tropical forest, 13. Climate action, Nitrogen, Fertilization, Phosphorus, Soil GHG fluxes, 15. Life on land, Methane, 6. Clean water
Abstract

Tropical soils are a major contributor to the balance of greenhouse gas (GHG) fluxes in the atmosphere. Models of tropical GHG fluxes predict that both the frequency of drought events and changes in atmospheric deposition of nitrogen (N) will significantly affect dynamics of soil carbon dioxide (CO2) and methane (CH4) production and consumption. In this study, we examined the combined effect of a reduction in precipitation and an increase in nutrient availability on soil CO2 and CH4 fluxes in a primary French Guiana tropical forest. Drought conditions were simulated by intercepting precipitation falling through the forest canopy with tarpaulin roofs. Nutrient availability was manipulated through application of granular N and / or phosphorus (P) fertilizer to the soil. Soil water content (SWC) below the roofs decreased rapidly and stayed at continuously low values until roof removal, which as a consequence roughly doubled the duration of the dry season. After roof removal, SWC slowly increased but remained lower than in the control soils even after 2.5 months of wet-season precipitation. We showed that drought-imposed reduction in SWC decreased the CO2 emissions (i.e CO2 efflux), but strongly increased the CH4 emissions. N, P and N × P (i.e. NP) additions all significantly increased CO2 emission but had no effect on CH4 fluxes. In treatments where both fertilization and drought were applied, the positive effect of N, P and NP fertilization on CO2 efflux was reduced. After roof removal, soil CO2 efflux was more resilient in the control plots than in the fertilized plots while there was only a modest effect of roof removal on soil CH4 fluxes. Our results suggest that a combined increase in drought and nutrient availability in soil can locally increase the emissions of both CO2 and CH4 from tropical soils, for a long term.

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