Incidencia del ramoneo del guanaco (Lama guanicoe Müller) sobre la regeneración temprana en bosques de lenga [Nothofagus pumilio (Poepp et Endl) Krasser] de Tierra del Fuego, Argentina

In this work we analyze the early regeneration of Nothofagus pumilio forests, as well as the impact of browsing by guanacos (Lama guanicoe), in Tierra del Fuego, Argentina. First, we describe the structure of three N. pumilio stands with differing management schedules: a native virgin forest stand (BV), a stand that was logged in 1991-93 leaving a certain homogeneous density of parent trees («shelterwood cut», CP), and a third stand that was selectively and intensively logged (FL) in 1995. In these three stands we quantify the use by guanacos (estimated from the density of fecal remains) and the frequency of browsed seedlings (< 0.5 cm) and saplings (> 0.5 cm in stem diameter). Results show a high incidence of browsing, which was higher for the native forests stand (100 % and 95.7 %), than for CP (69.9 % and 72.1 %) and FL (67.3 % and 61.5 %, for basal and apical damage of browsed plants, respectively). These differences are mainly due to the fact that patches where big trunks accumulate in managed stands, provide shelter from damage by guanacos. Comparison of observed and expected (according to calculated growth models) sapling heigth show that recurrent damage by guanacos prevent successful growth, the corresponding height loss being 83.1 % for BV, 45.7 % for CP, and 50.3 % for FL. We conclude that guanacos effectively limits early regeneration in both native and managed stands, though a wider time scale is needed for a conclusive assessment of the incidence of browsing in forest dynamics and production.En este trabajo se analiza la regeneración temprana y su consumo por el guanaco (Lama guanicoe) en bosques de lenga (Nothofagus pumilio) de Tierra del Fuego, Argentina. En primer lugar, se cuantifica la estructura de un rodal de bosque virgen (BV), uno de bosque aprovechado mediante corta de protección (CP: dejando árboles-padre homogéneamente distribuidos) en 1991-93 y uno aprovechado mediante floreo intenso (FL: extracción selectiva de los mejores pies) en 1995. En los tres rodales se analiza el uso del bosque por el guanaco y el consumo de plántulas y brinzales de lenga. Los resultados muestran que en todos los casos la incidencia del ramoneo es elevada, y que tiende a ser mayor en BV (100 % y 95,7 %) que en CP (69,9 % y 72,1 %) y en FL (67,3 % y 61,5 %) para el ramoneo basal y el ramoneo apical reciente, respectivamente. Estas diferencias se deben a que en los bosques aprovechados los acúmulos de residuos de corta impiden el acceso de los ramoneadores a las plántulas, que alcanzan así mayor altura. La comparación de alturas observadas y esperadas según un modelo de crecimiento sin influencia del guanaco indica que el ramoneo continuado, supone pérdidas de crecimiento del 83,1 % en BV, 45,7 % en CP y 50,3 % en FL. Se concluye que el guanaco puede ser un factor limitante del crecimiento inicial de la regeneración de los bosque virgen y aprovechado, si bien es preciso analizar esta incidencia a una escala de tiempo más amplia para conocer su efecto en la dinámica y la producción forestal

Environmental drivers of plant community assembly in Isla de los Estados at Southern Atlantic Ocean

The comprehensive assessment of environmental gradients influencing species assemblages is important for implementing new conservation strategies under climate change. This study aims to determine the multi-scale effect of altitudinal and longitudinal gradients as drivers of richness and plant community assembly in mountain landscapes of Isla de los Estados (Argentina) to identify areas with greater conservation value in Southern Patagonia. We chose three fjords across the island that extends from West to East and we categorized landscapes into four ecosystem types according to their vegetation type (forests and open-lands) and elevation (lower lands, 0-100 m.a.s.l. and upper lands, 300-400 m.a.s.l.). Forest structure, soil cover (woody debris, rocky outcrop and bare soil) and vegetation cover (vascular and non-vascular), including richness and growthforms (trees, shrubs, prostrate and erect herbs, tussock and rhizomatous grasses, ferns and inferior plants) were measured in 60 sampling areas (3 fjords × 2 vegetation types × 2 elevations × 5 replicates). ANOVAs and multivariate methods were used to analyse heterogeneity in forest structure, plant richness, and life-form. In addition, species richness and the Simpson’s diversity index were calculated to understand plant assembly at multiple-scales (α, β and γ). Our results showed that environmental gradients (altitudinal and longitudinal) are more important drivers of change of ecosystem type than forest spatial structure. Furthermore, forest structure significantly varied with altitudinal and longitudinal gradients affecting most of the studied variables. A greater similarity (in richness and cover) between open-lands of lower and higher elevations was detected, as well as between forests. Fjords showed a West-East gradient, where the western and center fjords were more closely related to each other than to the eastern fjord. A multi-scale diversity approach may play central role in improving our understanding the main environmental drivers of richness and plant community assembly in these forests, both theoretical and empirical, and may be used to identify the spatial scale at which ecosystem types have greater conservation value. This study indicates that for southern forest conservation at regional level, efforts must cover all environmental gradients, including the different vegetation types to assure ful conservation of all the species assemblages. | Supporting Information Supporting Information </supplementary-material

Manejo de malezas en bosques nativos y plantaciones forestales : Enfoques y problemas vinculados con el manejo de malezas en la producción forestal de Argentina

Fil: Achinelli, Fabio G.. Cátedra de Silvicultura. Facultad de Ciencias Agrarias y Forestales. Universidad Nacional de La Plata; ArgentinaFil: Martínez Pastur, Guillermo. Laboratorio de Recursos Forestales. Centro Austral de Investigaciones Científicas (CADIC). Ushuaia. Tierra del Fuego; ArgentinaFil: Frangi, Jorge Luis. Laboratorio de Investigaciones de Sistemas Ecológicos y Ambientales (LISEA). Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; Argentin

Modeling Soil Nitrogen Content in South Patagonia across a Climate Gradient, Vegetation Type, and Grazing

Soil total nitrogen (N) stock in rangelands, shrublands, and forests support key ecological functions such as the capacity of the land to sustain plant and animal productivity and ecosystem services. The objective of this study was to model soil total N stocks and soil C/N ratio from 0-30 cm depth across the region using freely accessible information on topography, climate, and vegetation with a view to establishing a baseline against which sustainable land management practices can be evaluated in Southern Patagonia. We used stepwise multiple regression to determine which independent variables best explained soil totalNvariation across the landscape in Southern Patagonia. We then used multiple regression models to upscale and produce maps of soil total N and C/N across the Santa Cruz province. Soil total N stock to 30 cm ranged from 0.13 to 2.21 kg N m-2, and soil C/N ratios ranged from 4.5 to 26.8. The model for variation of soil total N stock explained 88% of the variance on the data and the most powerful predictor variables were: isothermality, elevation, and vegetation cover (normalized difference vegetation index (NDVI)). Soil total N and soil C/N ratios were allocated to three categories (low, medium, high) and these three levels were used to map the variation of soil total N and soil C/N ratios across Southern Patagonia. The results demonstrate that soil total N decreases as desertification increases, probably due to erosional processes, and that soil C/N is lower at low temperatures and increased with increasing precipitation. Soil total N and soil C/N ratios are critical variables that determine system capacity for productivity, especially the provisioning ecosystem services, and can serve as baselines against which efforts to adopt more sustainable land management practices in Patagonia can be assessed.Fil: Peri, Pablo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones y Transferencia de Santa Cruz. Universidad Tecnológica Nacional. Facultad Regional Santa Cruz. Centro de Investigaciones y Transferencia de Santa Cruz. Universidad Nacional de la Patagonia Austral. Centro de Investigaciones y Transferencia de Santa Cruz; Argentina. Instituto Nacional de Tecnología Agropecuaria; ArgentinaFil: Rosas, Yamina Micaela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Ladd, Brenton. Universidad Científica del Sur; PerúFil: Toledo, Santiago. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones y Transferencia de Santa Cruz. Universidad Tecnológica Nacional. Facultad Regional Santa Cruz. Centro de Investigaciones y Transferencia de Santa Cruz. Universidad Nacional de la Patagonia Austral. Centro de Investigaciones y Transferencia de Santa Cruz; ArgentinaFil: Lasagno, Romina G.. Instituto Nacional de Tecnología Agropecuaria; ArgentinaFil: Martínez Pastur, Guillermo José. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentin

Survival and growth of Nothofagus pumilio seedlings under several microenvironments after variable retention harvesting in southern Patagonian forests

Context: Variable retention prescriptions for Nothofagus pumilio forests provide for biodiversity conservation and natural regeneration by controlled opening of the canopy. Harvesting generates different microenvironments which present dissimilar conditions for seedling establishment, due to positive or negative influences over biotic and abiotic factors. Aims: This study evaluated seedling survival and performance in different microenvironments within the harvested stands. Tested hypotheses stated that seedling stress and performance were influenced by harvesting due to changes in forest structure, microclimate, soil properties, and nutrient availability. Methods: In the stands harvested by variable retention, five contrasting microenvironments were selected as treatments for the experiments and sampling. Environmental variables were related to ecophysiological, seedling survival, and performance. Results: The modification of forest structure (crown cover and tree density) and the presence of coarse woody debris greatly affect the effective rainfall and global radiation reaching understorey level, influencing seedling stress and consequently survival and performance. Harvesting also modifies soil properties (e.g., soil bulk density) and coarse woody debris accumulation which in turn influences soil moisture and/or solar radiation levels. Analyses showed that seedlings received benefits of microenvironment variation after harvesting. Areas covered with middle or fine woody debris presented regeneration with better ecophysiological response and seedling performance, although dispersed retention areas (far away from remnant trees) and roads could also present suitable conditions for seedling survival and performance. Conclusions: The proportion of different microenvironments in the harvested forests will determine the amount of natural recruitment of regeneration and consequently the success of proposed silvicultural management. Forest practices must be manipulated to increase the proportion of favorable microenvironments (e.g., woody debris), allowing greater natural regeneration success during the first years after harvesting.Laboratorio de Investigación de Sistemas Ecológicos y Ambientale

Antropic fires promotes the increase of alien species cover in the understory of Nothofagus antarctica (Forster f.) Oersted forests under management

Se analizó la respuesta temprana del sotobosque de Nothofagus antarctica (ñire) luego de un incendio, particularmente, la potencialidad de invasión por parte de especies exóticas. Se establecieron transectas permanentes (n=6 por sitio) de 10 m de longitud antes (2008) y después del fuego (2009 a 2014) en bosques maduros con manejo silvopastoril. Se evaluó la riqueza y cobertura de especies con el método de intersección puntual y se analizaron los datos mediante ANOVAs de medidas repetidas. La composición del sotobosque de N. antarctica se modificó debido a: (a) el aumento de la cobertura de hierbas y pastos exóticos, (b) el ingreso de especies exóticas nuevas ausentes en la situación pre-incendio, (c) la menor cobertura de algunas especies de hierbas nativas, d) el ingreso de especies nativas de Tierra del Fuego, pero no propias del bosque y que estaban ausentes en la situación pre-incendio.We examined the early response of Nothofagus antarctica (ñire) understory after a fire, including the potential for invasion by exotic species. Permanent transects (n =6 per site) 10m length were surveyed before (2008) and after fire (2009 to 2014). In each transect, vegetation (species richness and cover) was recorded at by the point-intercept method. Data were analyzed using repeated measures ANOVAs. The composition of N. antarctica understory was significantly modified from: (a) increasing the coverage of alien species of herbs and grasses, (b) the income of new alien species that were absent in the pre-fire situation, (c) the lowest coverage of some native species of herbs, (d) the income of native species of Tierra del Fuego, which are typical from other habitat types (e.g., grasslands), and which were absent in the pre-fire situation.Laboratorio de Investigación de Sistemas Ecológicos y Ambientale

Ojos que no ven… ¿Qué podemos hacer para incluir más a la fracción subterránea en estudios de vegetación?

Conocer la estructura y el funcionamiento de la fracción subterránea de la vegetación es fundamental para comprender numerosos procesos que ocurren en distintos niveles de organización. Sin embargo, dicha fracción fue menos estudiada que su contraparte aérea, principalmente por el gran esfuerzo que demanda muestrearla a campo y procesarla en el laboratorio. En la XXVIII Reunión Argentina de Ecología (Mar del Plata, 2018) se realizaron dos simposios sobre la importancia de conocer las raíces en estudios ecológicos. De los simposios surgió la necesidad de 1) cuantificar los estudios que hayan evaluado las fracciones subterránea y aérea de la vegetación, y 2) determinar las metodologías empleadas y las variables de la fracción subterránea registradas en sistemas naturales (i.e., pastizales, estepas, bosques, arbustales y desierto) y antropizados (i.e., pasturas y cultivos) en seis provincias fitogeográficas de la Argentina y en dos regiones geomorfológicas de Uruguay. Se registraron 933 estudios publicados entre 1990 y 2019. El 57% y el 23% correspondieron a estudios exclusivos de la fracción aérea y de la subterránea, respectivamente, con un incremento exponencial en el tiempo de ambas fracciones. En la actualidad existe una tendencia a incorporar el compartimiento subterráneo en estudios ecológicos. Mediante un análisis sistemático se encontró que se emplearon seis métodos de muestreo (barreno, ruleros, planta entera, monolitos, rhizotron y estimación de la biomasa subterránea a partir de la biomasa aérea) para evaluar cuatro variables (biomasa subterránea, productividad primaria neta subterránea, algunos atributos radicales y tasa de descomposición radical). El método más empleado fue el del barreno y la variable más evaluada fue la biomasa subterránea. Proponemos fomentar la colaboración entre equipos de investigación y establecer comparaciones metodológicas para comprender los alcances de los resultados y obtener estimaciones más confiables sobre las consecuencias del cambio en el uso del suelo.To know the structure and functioning of the belowground vegetation compartment is essential to understand numerous processes that occur at different organization levels. However, the belowground vegetation compartment has traditionally been less studied than the above layer due to the great effort required for field sampling and laboratory processing. In the XXVIII Reunión Argentina de Ecología, Mar del Plata 2018, two symposia about the importance of root knowledge in ecological studies were conducted. From this exchange arose the need to 1) quantify studies that include data of belowground and aboveground vegetation, and 2) determine the methodologies and the variables of the belowground compartment recorded in natural (grasslands, steppes, forests, shrubs, and desert) and human modified systems (pastures, crops) in six Argentinean phytogeographic provinces and in two Uruguayan geomorphological regions. There were 933 published studies from 1990 to 2019. The 57% and 23% corresponded to exclusive studies of the above and belowground compartments respectively, with an exponential increase in the time of both fractions. Currently, there is a tendency to incorporate the underground compartment in ecological studies. Through systematic analysis, it was found that six sampling methods were used (soil core, ingrowth cores, trench, monoliths, rhizotron and belowground biomass estimation from aboveground biomass) where four variables of the belowground vegetation compartment were recorded (belowground biomass, belowground net primary productivity, root traits, and roots decomposition rate). Obtaining soil volumes by soil core was the most used method, while belowground biomass was the most evaluated variable. We propose to encourage collaboration between research teams and establish methodological comparisons to understand the scope of the results and obtain better estimates about the consequences of land-use change.EEA Santa CruzFil: López Mársico, Luis. Universidad de la República. Facultad de Ciencias. Instituto de Ecología y Ciencias Ambientales; UruguayFil: Pestoni, Sofía. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Conti, Georgina. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Pérez-Harguindeguy, Natalia. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Martínez Pastur, Guillermo José. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas. Laboratorio de Recursos Agroforestales; ArgentinaFil: Pinto, Priscila. 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: Sarquis, Agustín. 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: Reyes, María Fernanda. 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; Argentina. Universidad Nacional del Comahue. Facultad de Ambiente y Salud. Laboratorio de Rehabilitación y Restauración de Ecosistemas Áridos y Semiáridos (LARREA); ArgentinaFil: Peri, Pablo Luis. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Santa Cruz; Argentina. Universidad Nacional de la Patagonia Austral; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Piñeiro, Gervasio. 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; Argentina. Universidad de la República. Facultad de Agronomía. Departamento de Sistemas Ambientales; Urugua

MASTREE+ : time-series of plant reproductive effort from six continents

Significant gaps remain in understanding the response of plant reproduction to environmental change. This is partly because measuring reproduction in long-lived plants requires direct observation over many years and such datasets have rarely been made publicly available. Here we introduce MASTREE+, a data set that collates reproductive time-series data from across the globe and makes these data freely available to the community. MASTREE+ includes 73,828 georeferenced observations of annual reproduction (e.g. seed and fruit counts) in perennial plant populations worldwide. These observations consist of 5971 population-level time-series from 974 species in 66 countries. The mean and median time-series length is 12.4 and 10 years respectively, and the data set includes 1122 series that extend over at least two decades (≥20 years of observations). For a subset of well-studied species, MASTREE+ includes extensive replication of time-series across geographical and climatic gradients. Here we describe the open-access data set, available as a.csv file, and we introduce an associated web-based app for data exploration. MASTREE+ will provide the basis for improved understanding of the response of long-lived plant reproduction to environmental change. Additionally, MASTREE+ will enable investigation of the ecology and evolution of reproductive strategies in perennial plants, and the role of plant reproduction as a driver of ecosystem dynamics

MASTREE+: Time-series of plant reproductive effort from six continents.

Significant gaps remain in understanding the response of plant reproduction to environmental change. This is partly because measuring reproduction in long-lived plants requires direct observation over many years and such datasets have rarely been made publicly available. Here we introduce MASTREE+, a data set that collates reproductive time-series data from across the globe and makes these data freely available to the community. MASTREE+ includes 73,828 georeferenced observations of annual reproduction (e.g. seed and fruit counts) in perennial plant populations worldwide. These observations consist of 5971 population-level time-series from 974 species in 66 countries. The mean and median time-series length is 12.4 and 10 years respectively, and the data set includes 1122 series that extend over at least two decades (≥20 years of observations). For a subset of well-studied species, MASTREE+ includes extensive replication of time-series across geographical and climatic gradients. Here we describe the open-access data set, available as a.csv file, and we introduce an associated web-based app for data exploration. MASTREE+ will provide the basis for improved understanding of the response of long-lived plant reproduction to environmental change. Additionally, MASTREE+ will enable investigation of the ecology and evolution of reproductive strategies in perennial plants, and the role of plant reproduction as a driver of ecosystem dynamics

Crecimiento en cortinas cortavientos de "Populus nigra cv." "Itálica" en Patagonia Sur (Argentina)

La implantación de cortinas contribuyó al desarrollo agrícola en Patagonia sur. Predecir el crecimiento y la dinámica de estas plantaciones permite cuantificar el área protegida de los cultivos y la rentabilidad maderera. Este trabajo presenta modelos biométricos para Populus nigra cv 'Italica' en diferentes sitios, condiciones de copa y distanciamientos en cortinas cortavientos de Santa Cruz (Argentina). Para el ajuste del crecimiento diametral y en altura se utilizó una modificación de la función de Chapman-Richards. Para la ecuación de volumen se empleó la función de Schumacher-Hall, mientras que usando técnicas de regresión múltiple se definieron los modelos de dinámica de clases de copa. Los modelos ajustados presentaron muy buenos estadísticos, ya que los múltiples factores que inciden en el crecimiento de cortinas cortaviento pudieron ser explicados a través de variables de fácil medición (DAP, altura total, clases de copa, sitio)