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Ecosystem Consequences of Tree Monodominance for Nitrogen Cycling in Lowland Tropical Forest

Understanding how plant functional traits shape nutrient limitation and cycling on land is a major challenge in ecology. This is especially true for lowland forest ecosystems of the tropics which can be taxonomically and functionally diverse and rich in bioavailable nitrogen (N). In many tropical re...

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Autores principales: Brookshire, E. N. Jack, Thomas, Steven A.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Public Library of Science 2013
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3723728/
https://www.ncbi.nlm.nih.gov/pubmed/23936215
http://dx.doi.org/10.1371/journal.pone.0070491
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author Brookshire, E. N. Jack
Thomas, Steven A.
author_facet Brookshire, E. N. Jack
Thomas, Steven A.
author_sort Brookshire, E. N. Jack
collection PubMed
description Understanding how plant functional traits shape nutrient limitation and cycling on land is a major challenge in ecology. This is especially true for lowland forest ecosystems of the tropics which can be taxonomically and functionally diverse and rich in bioavailable nitrogen (N). In many tropical regions, however, diverse forests occur side-by-side with monodominant forest (one species >60% of canopy); the long-term biogeochemical consequences of tree monodominance are unclear. Particularly uncertain is whether the monodominant plant-soil system modifies nutrient balance at the ecosystem level. Here, we use chemical and stable isotope techniques to examine N cycling in old-growth Mora excelsa and diverse watershed rainforests on the island of Trinidad. Across 26 small watershed forests and 4 years, we show that Mora monodominance reduces bioavailable nitrate in the plant-soil system to exceedingly low levels which, in turn, results in small hydrologic and gaseous N losses at the watershed-level relative to adjacent N-rich diverse forests. Bioavailable N in soils and streams remained low and remarkably stable through time in Mora forests; N levels in diverse forests, on the other hand, showed high sensitivity to seasonal and inter-annual rainfall variation. Total mineral N losses from diverse forests exceeded inputs from atmospheric deposition, consistent with N saturation, while losses from Mora forests did not, suggesting N limitation. Our measures suggest that this difference cannot be explained by environmental factors but instead by low internal production and efficient retention of bioavailable N in the Mora plant-soil system. These results demonstrate ecosystem-level consequences of a tree species on the N cycle opposite to cases where trees enhance ecosystem N supply via N(2) fixation and suggest that, over time, Mora monodominance may generate progressive N draw-down in the plant-soil system.
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spelling pubmed-37237282013-08-09 Ecosystem Consequences of Tree Monodominance for Nitrogen Cycling in Lowland Tropical Forest Brookshire, E. N. Jack Thomas, Steven A. PLoS One Research Article Understanding how plant functional traits shape nutrient limitation and cycling on land is a major challenge in ecology. This is especially true for lowland forest ecosystems of the tropics which can be taxonomically and functionally diverse and rich in bioavailable nitrogen (N). In many tropical regions, however, diverse forests occur side-by-side with monodominant forest (one species >60% of canopy); the long-term biogeochemical consequences of tree monodominance are unclear. Particularly uncertain is whether the monodominant plant-soil system modifies nutrient balance at the ecosystem level. Here, we use chemical and stable isotope techniques to examine N cycling in old-growth Mora excelsa and diverse watershed rainforests on the island of Trinidad. Across 26 small watershed forests and 4 years, we show that Mora monodominance reduces bioavailable nitrate in the plant-soil system to exceedingly low levels which, in turn, results in small hydrologic and gaseous N losses at the watershed-level relative to adjacent N-rich diverse forests. Bioavailable N in soils and streams remained low and remarkably stable through time in Mora forests; N levels in diverse forests, on the other hand, showed high sensitivity to seasonal and inter-annual rainfall variation. Total mineral N losses from diverse forests exceeded inputs from atmospheric deposition, consistent with N saturation, while losses from Mora forests did not, suggesting N limitation. Our measures suggest that this difference cannot be explained by environmental factors but instead by low internal production and efficient retention of bioavailable N in the Mora plant-soil system. These results demonstrate ecosystem-level consequences of a tree species on the N cycle opposite to cases where trees enhance ecosystem N supply via N(2) fixation and suggest that, over time, Mora monodominance may generate progressive N draw-down in the plant-soil system. Public Library of Science 2013-07-25 /pmc/articles/PMC3723728/ /pubmed/23936215 http://dx.doi.org/10.1371/journal.pone.0070491 Text en © 2013 Brookshire, Thomas http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are properly credited.
spellingShingle Research Article
Brookshire, E. N. Jack
Thomas, Steven A.
Ecosystem Consequences of Tree Monodominance for Nitrogen Cycling in Lowland Tropical Forest
title Ecosystem Consequences of Tree Monodominance for Nitrogen Cycling in Lowland Tropical Forest
title_full Ecosystem Consequences of Tree Monodominance for Nitrogen Cycling in Lowland Tropical Forest
title_fullStr Ecosystem Consequences of Tree Monodominance for Nitrogen Cycling in Lowland Tropical Forest
title_full_unstemmed Ecosystem Consequences of Tree Monodominance for Nitrogen Cycling in Lowland Tropical Forest
title_short Ecosystem Consequences of Tree Monodominance for Nitrogen Cycling in Lowland Tropical Forest
title_sort ecosystem consequences of tree monodominance for nitrogen cycling in lowland tropical forest
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3723728/
https://www.ncbi.nlm.nih.gov/pubmed/23936215
http://dx.doi.org/10.1371/journal.pone.0070491
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