Plant community controls small-scale variation in nutrient stoichiometry in a Patagonian peatland

Elemental stoichiometry of plant litter is typically interpreted to reflect nutrient availability and limitation, e.g. the N:P ratio indicates whether plant growth is N- or P-limited and might point towards the presence of N-fixation. However, in the case of plant litter and peat organic matter, resorption of nutrients during senescence, and preferential loss of nutrients during decomposition have to be taken into account. Here we study how small scale variability in species composition within peatlands affects the stoichiometry and long term apparent uptake rates of nutrients (C, N, P, K, S, Ca, Mg) in an ombrotrophic peatland in southern Patagonia. Assuming that nutrient availability is similar within one site, observed variation should be driven by vegetation and decomposition processes linked to microtopography. We studied a transect spanning 800 m. where the vegetation changed from cushion plant (Astelia pumila) dominated, to graminoid dominated, ending in Sphagnum magellanicum dominated. From six peat cores along this transect we analysed nutrient concentrations by X-ray fluorescence. The peat decomposition state, expressed as FTIR-humification index, was the best predictor of stoichiometric variation (particularly ratios C:N, C:S, and N:P), followed by current plant species composition. Comparison of average peat core stoichiometry across the transect showed that C:N and C:S ratios were larger in Sphagnum cores than cushion plant and graminoid cores (C:N 56±14 vs. 38±6; C:S 312±61 vs. 268±57; respectively), controlled by lower decomposition state in Sphagnum cores and larger C:N ratios in living biomass of Sphagnum vs. A. pumila. Larger N:P ratios in cushion plant and graminoid vs. Sphagnum cores (N:P 50±12 vs. 38±11; respectively) could furthermore indicate the presence of N-fixation in the former. Comparison with two additional Patagonian bogs showed similar distinction in C:N and C:S ratios (both: Sphagnum > cushion plant), but variation between cores within sites was more pronounced than between different peatlands. Taking the variable peat accumulation rate (0.09 ? 0.52 mm yr-1) into account, there was notable variation in apparent long term nutrient uptake rates along the transect. N and S uptake rates were larger in cushion plant and graminoid versus Sphagnum cores, while Mg uptake rates were largest in Sphagnum cores. Overall, the stoichiometry of these Patagonian peatlands suggests lower availability of N, P, and Ca compared to peatlands in Ontario, Canada, resulting in lower apparent N, P, and Ca uptake rates. In contrast, apparent Mg uptake rates were larger in Patagonia than Ontario. These results indicate that small scale variability in long term accumulation of nutrients in these ecosystems might be more pronounced than variability in long term C accumulation, and highlights the variability in nutrient availability between peatlands of different regions.Fil: Mathijssen, Paul. University of Münster; AlemaniaFil: Münchberger, Wiebke. University of Münster; AlemaniaFil: Borken, Werner. University of Bayreuth; AlemaniaFil: Pancotto, Veronica Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Kleinebecker, Till. Justus Liebig Universitat Giessen; AlemaniaFil: Knorr, Klaus Holger. University of Bayreuth; Alemania21th European Geosciences Union General AssemblyVienaAustriaAsamblea General de European Geosciences Unio

Reduction of solar UV-B mediates changes in the Sphagnum capitulum microenvironment and the peatland microfungal community

The influence of near-ambient and reduced solar UV-B radiation on a peatland microfungal community was assessed by exposing experimental plots to UV-selective filtration. Replicate plots were covered with special plastic films to effect treatments of near-ambient and attenuated solar UV-B. The microfungal community from the top 1 cm of Sphagnum capitulum in a Tierra del Fuego peatland was censused throughout three growing seasons, between 1999 and 2002. Sphagnum capitula under near-ambient UV-B were more compressed and held more water than capitula under reduced UV-B. This water had a greater conductivity and was more acidic under near-ambient UV-B, as would be expected with increased leaching from the Sphagnum leaves. Nine regularly occurring hyphal fungi from the peatland were identified, at least to genus. Over three field seasons, no treatment effect on total fungal colony abundance was recorded, but individual species abundance was increased (Mortierella alpina), decreased (Penicillium frequentans), or was unaffected (P. thomii, Aureobasidium) by near-ambient UV-B. Species richness was also slightly lower under near-ambient UV-B. These treatment differences were smaller than seasonal or inter-annual fluctuations in abundance and species richness. In a growth chamber experiment, lamp UV-B treatments indicated that realistic fluxes of UV-B can inhibit fungal growth in some species. In addition to this direct UV-B effect, we suggest that changes in the peatland fungal community under near-ambient solar UV-B may also result from increased nutrient and moisture availability in the Sphagnum capitulum. The subtle nature of the responses of peatland fungi to solar UV-B suggests that most fungal species we encountered are well adapted to current solar UV-B fluxes in Tierra del Fuego.Fil: Robson, T. Matthew. State University of Utah; Estados UnidosFil: Pancotto, Veronica Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Ballare, Carlos Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Sala, Osvaldo Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Scopel, Ana Leonor. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Caldwell, Martyn M.. State University of Utah; Estados Unido

High-resolution classification of south patagonian peat bog microforms reveals potential gaps in up-scaled CH4 fluxes by use of Unmanned Aerial System (UAS) and CIR imagery

South Patagonian peat bogs are little studied sources of methane (CH4). Since CH4 fluxes can vary greatly on a small scale of meters, high-quality maps are needed to accurately quantify CH4 fluxes from bogs. We used high-resolution color infrared (CIR) images captured by an Unmanned Aerial System (UAS) to investigate potential uncertainties in total ecosystem CH4 fluxes introduced by the classification of the surface area. An object-based approach was used to classify vegetation both on species and microform level. We achieved an overall Kappa Index of Agreement (KIA) of 0.90 for the species- and 0.83 for the microform-level classification, respectively. CH4 fluxes were determined by closed chamber measurements on four predominant microforms of the studied bog. Both classification approaches were employed to up-scale CH4 closed chamber measurements in a total area of around 1.8 hectares. Including proportions of the surface area where no chamber measurements were conducted, we estimated a potential uncertainty in ecosystem CH4 fluxes introduced by the classification of the surface area. This potential uncertainty ranged from 14.2 mg·m-2· day-1 to 26.8 mg·m-2· day-1. Our results show that a simple classification with only few classes potentially leads to pronounced bias in total ecosystem CH4 fluxes when plot-scale fluxes are up-scaled.Fil: Lehmann, Jan R. K.. Westfalische Wilhelms Universitat; AlemaniaFil: Münchberger, Wiebke. Westfalische Wilhelms Universitat; AlemaniaFil: Knoth, Christian. Westfalische Wilhelms Universitat; AlemaniaFil: Blodau, Christian. Westfalische Wilhelms Universitat; AlemaniaFil: Nieberding, Felix. Westfalische Wilhelms Universitat; AlemaniaFil: Prinz, Torsten. Westfalische Wilhelms Universitat; AlemaniaFil: Pancotto, Veronica Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Kleinebecker, Till. Westfalische Wilhelms Universitat; Alemani

Microfungal composition in an Astellia-Donatia cushion peatland in Tierra del Fuego, Argentina

Southern Hemisphere peatlands store substantial amounts of soil carbon. Despite their importance in the global carbon cycle, little is known about decomposition processes and the associated fungal diversity. The present study describes the composition of fungal assemblage in two depths from a cushion peatland of predominating Astelia (Asteliaceae) and Donatia (Donatiaceae) species in Moat, Tierra del Fuego. From 48 samples processed, we obtained 338 isolates. Using different culturing methodologies, through direct and microscopic observation and using molecular methods we identified 38 fungal species and 18 genera of Ascomycetes and Zygomycetes. Isolates belonging to Ascomycetes were the most abundant, with dominance of Penicillium and Trichoderma. We described fungal composition and compared species diversity and evenness across two dephts. No differences in the diversity index and evenness were found between depths. The studied peat is an ecosystem that has a great diversity of filamentous fungal species, some of which are described in other peatlands worldwide.Fil: Paredes, Noelia Ivana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones En Biodiversidad y Biotecnología; ArgentinaFil: Consolo, Verónica Fabiana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones En Biodiversidad y Biotecnología; Argentina. Fundación para Investigaciones Biológicas Aplicadas; ArgentinaFil: Pancotto, Veronica Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina. Universidad Nacional de Tierra del Fuego; ArgentinaFil: Fritz, Christian. Radboud University; Países BajosFil: Barrera, Marcelo Daniel. Universidad Nacional de La Plata; ArgentinaFil: Arambarri, Angélica Margarita. Universidad Nacional de la Plata. Facultad de Ciencias Naturales y Museo. Instituto de Botánica Spegazzini; ArgentinaFil: Salerno, Graciela Lidia. Fundación para Investigaciones Biológicas Aplicadas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones En Biodiversidad y Biotecnología; Argentin

Decomposition of Nothofagus pumilio in Tierra del Fuego forests affected by forest management practices

Los bosques de lenga de Tierra del Fuego son aprovechados forestalmente, uno de los métodos más usados es la corta de protección (CP). El objetivo fue evaluar la descomposición de hojarasca en bosques de lenga intervenidos con CP de Tierra del Fuego. Se consideraron tres situaciones: área intervenida propiamente dicha (CP), área de acopio cercana (Ca) y bosque primario sin intervención (BP) a través del ciclo de manejo (1, 5-10 y más de 50 años después del aprovechamiento). Se instalaron bolsitas de descomposición, y luego de 21 meses, los sitios de más de 50 años fueron los que presentaron mayor descomposición. Este efecto de la edad desde la intervención se evidenció durante todas las cosechas evaluadas (3, 9, 15 y 21 meses). Por el contrario, el tipo de intervención sólo presentó un efecto significativo al comienzo de la descomposición, siendo mayor la descomposición en sitios intervenidos (CP y Ca). Estos resultados sugieren que el proceso de descomposición es afectado por la intervención del bosque, tanto por el efecto inmediato de la intervención que podría estar afectando los compuestos que presentan una rápida liberación, como por el efecto a más largo plazo visto a través de los años transcurridos desde la intervención.Fil: Mansilla, Paula Romina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Cientificas; Argentina;Fil: Pancotto, Veronica Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Cientificas; Argentina;Fil: Moretto, Alicia Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Cientificas; Argentina;Fil: Vrsalovic, Jazmin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Cientificas; Argentina;Fil: Escobar, Julio Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Cientificas; Argentina;Fil: Oro Castro, Natalia Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Cientificas; Argentina;Fil: Lencinas, María Vanessa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Cientificas; Argentina

N deposition and elevated CO2 on methane emissions: Differential responses of indirect effects compared to direct effects through litter chemistry feedbacks

Increases in atmospheric CO2 concentration and N deposition are expected to affect methane (CH4) production in soils and emission to the atmosphere, directly through increased plant litter production and indirectly through changes in substrate quality. We examined how CH4 emission responded to changes in litter quality under increased N and CO2, beyond differences in CH4 resulting from changes in litter production. We used senesced leaves from 13C-labeled plants of Molinia caerulea grown at elevated and ambient CO2 and affected by N fertilization to carry out two experiments: a laboratory litter incubation and a pot experiment. N fertilization increased N and decreased C concentrations in litter whereas elevated CO2 decreased litter quality as reflected in litter C and N concentrations and in the composition of lignin and saturated fatty acids within the litter. In contrast to our expectations, CH4 production in the laboratory incubation decreased when using litter from N-fertilized plants as substrate, whereas litter from elevated CO2 had no effect, compared to controls without N and at ambient CO2. Owing to high within-treatment variability in CH4 emissions, none of the treatment effects were reflected in the pot experiment. C mineralization rates were not affected by any of the treatments. The decrease in CH4 emissions due to indirect effects of N availability through litter quality changes (described here for the first time) contrast direct effects of N fertilization on CH4 production. The complex interaction of direct effects with indirect effects of increased N on litter quality may potentially result in a net decrease in CH4 emissions from wetlands in the long term.Fil: Pancotto, Veronica Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Bodegom, P. M. van. University Of Amsterdam; Países BajosFil: Hal, J. van. University Of Amsterdam; Países BajosFil: Logtestijn, R. S. P. van. University Of Amsterdam; Países BajosFil: Blokker, P.. University Of Amsterdam; Países BajosFil: Toet, S.. University Of Amsterdam; Países Bajos. University Of York; Reino UnidoFil: Aerts, R.. University Of Amsterdam; Países Bajo

Patron de uso de habitat de roedores en la reserva natural estricta Otamendi

Se estudió el patrón de uso de microhábitat de Akodon azarae, Oligoryzomys flavescens y Calomys musculinus en un espartillal de la Reserva Natural Estricta Otamendi. Se evaluó el efecto de las características de la vegetación y su variabilidad temporal en la distribución de las capturas de los roedores. Las poblaciones de roedores fiieron estudiadas entre febrero de 1996 y junio de 1997 mediante el método de captura-marcado-recaptura. Se instalaron trampas Shermann en una grilla de 94 estaciones de muestreo (0,94 ha). Se efectuaron censos de vegetación en cada estación y se delimitaron microhábitats utilizando un análisis de componentes principales: espartillal denso (MHl), espartillal denso quemado (MHZ), espartillal ralo (MI-13). La relación roedor-vegetación se analizó mediante un análisis de correspondencia canónico. A.azarae y Oflavescens se restringieron a sitios con mayor cobertura total, de gramíneas y altura de la vegetación de MHl, Cmusculinus se ubicó en sitios con mayor porcentaje de suelo desnudo restringidos a MHZ y MH3. A partir de febrero de 1997 se observó el ingreso de A.azarae a MHZ, coincidiendo con la recuperación (etapas sucesionales) de la altura y cobertura total de la vegetación en este microhábitat, Oflavescens ingresó al MHZ a partir de marzo de 1998. Ambas especies continuaron prefiriendo sitios con gramíneas y de mayor altura de la vegetación, mientras que Cmusculinus se reubicó dentro del MHZ, ocupando sitios con mayor cobertura de material seco en pie. Las variaciones mas importantes en el estudio se registraron en el MHZ, estas fueron explicadas en gran parte por los cambios de la vegetación; mientras que las variaciones en las capturas de roedores en MHl no responden a cambios de la vegetación.Fil: Pancotto, Veronica Andrea. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Temperature measurements from treatment and control plots of a passive warming experiment at a cushion bog on Tierra del Fuego, Argentina

We conducted our study in a cushion bog dominated by Astelia pumila on Tierra del Fuego, Argentina (54.972° S, 66.734° W). We experimentally investigated how a cushion bog plant community responded to elevated surface temperature conditions. We installed a year-round passive warming experiment using semicircular plastic walls that raised average near-surface air temperatures between 0.4°C and 0.7°C (at the three of ten treatment plots which were equipped with temperature sensors). We conducted chamber gas flux measurements to characterize differences in carbon dioxide exchange dynamics between the treatment and control plots.Fil: Pancotto, Veronica Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina. Universidad Nacional de Tierra del Fuego; ArgentinaFil: Holl, David. Universitat Hamburg; AlemaniaFil: Escobar, Julio Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Kutzbach, Lars. Universitat Hamburg; Alemani

Liverworts of Sphagnum magellanicum Brid. Raised bogs from Tierra del Fuego National Park, Ushuaia (Argentina)

At present, the available information about the liverworts of Sphagnum magellanicum Brid. mires from South America is very limited. The main aim of this paper is to present a comprehensive study of the liverwort flora of this habitat, as well as details on the chorology and ecology of the taxa involved. Four different environmental units were examined, based on the water table level and plant cover, in three representative raised bogs from Tierra del Fuego National Park (Ushuaia). Floristic releve´s were recorded in 93 square plots (0.5060.50 m2 ), distributed at random in the environmental units. Twenty-four liverwort species have been identified; the majority have a Subantarctic distribution and there were a remarkable number of Magellanean endemics (11 species). Among the rare species, there were two new records for the Argentinian Province of Tierra del Fuego, Cephaloziella byssacea and Chiloscyphus notophyllus. The ecological preferences of the species were analysed based on their frequencies in the four environmental units examined. Only six species demonstrated significant correlation with some of the environmental units. Riccardia pallidevirens, R. georgiensis, R. alcicornis, and Cephaloziella varians, showed a preference for waterlogged and wet habitats, while Calypogeia sphagnicola and Cephalozia chilensis were linked to dense carpets of Sphagnum magellanicum.Fil: Souto, Martín. Universidad de Santiago de Compostela; EspañaFil: Castro, Daniel. Universidad de Santiago de Compostela; EspañaFil: Pancotto, Veronica Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Fraga, M. Isabel. Universidad de Santiago de Compostela; Españ

Fine roots of Prosopis flexuosa trees in the field. Plant and soil variables that control their growth and depth distribution

Fine root growth in natural vegetation is difficult to predict due to its regulation by soil and plant factors. Field studies in arid ecosystems show a variety of root responses to soil resources and to plant aboveground phenology that sometimes differ from root responses predicted by controlled experiments. There is a pressing need to cover a greater diversity of plant species and ecological scenarios in field studies. In this paper, we have studied fine roots of Prosopis flexuosa trees living with or without access to phreatic water in an inter-dune valley and a dune flank, respectively, in the Central Monte Desert, Argentina. We have described fine root growth over time and at different depths by rhizotron observations and soil core auger samples in relation to soil water and nutrients, tree crown phenology, plant water and nutrient status. We have found that surface soil moisture from rainfall is the variable that best predicts seasonal topsoil fine root growth. Access to groundwater advanced leaf sprouting with respect to rainfall, but did not advance root growth that stayed linked to rainfall in valley and dune flank trees. Trees without access to phreatic water produced deeper and thicker or denser roots, which is consistent with the poor soil resource content of dunes. Variations in rainfall dynamics due to global climate change may have a particular impact on fine roots and ecosystem processes such as biogeochemistry and carbon budget in dune flank trees as well as in valley trees.Fil: Guevara, Aranzazú. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Pancotto, Veronica Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Mastrantonio, Leandro Eloy. Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias; ArgentinaFil: Giordano, Carla Valeria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; Argentin