Facundo Oddi | Universidad Nacional de Rio Negro (original) (raw)

Papers by Facundo Oddi

Oddi, Facundo J. Universidad Nacional de Rio Negro. Instituto de Investigaciones en Recursos Natu... more Oddi, Facundo J. Universidad Nacional de Rio Negro. Instituto de Investigaciones en Recursos Naturales, Agroecologia y Desarrollo Rural. Rio Negro, Argentina.

Conservation Letters, 2020

International agreements aim to conserve 17% of Earth's land area by 2020 but include no area... more International agreements aim to conserve 17% of Earth's land area by 2020 but include no area‐based conservation targets within the working landscapes that support human needs through farming, ranching, and forestry. Through a review of country‐level legislation, we found that just 38% of countries have minimum area requirements for conserving native habitats within working landscapes. We argue for increasing native habitats to at least 20% of working landscape area where it is below this minimum. Such target has benefits for food security, nature's contributions to people, and the connectivity and effectiveness of protected area networks in biomes in which protected areas are underrepresented. We also argue for maintaining native habitat at higher levels where it currently exceeds the 20% minimum, and performed a literature review that shows that even more than 50% native habitat restoration is needed in particular landscapes. The post‐2020 Global Biodiversity Framework is ...

Ecología Austral, 2021

Las especies forestales nativas permiten restaurar bosques y son una alternativa productiva suste... more Las especies forestales nativas permiten restaurar bosques y son una alternativa productiva sustentable. Como en cualquier forestación, en bosques implantados o enriquecidos con nativas, el conocimiento sobre la dinámica de los plantines resulta clave para establecer estrategias de manejo. En este estudio describimos la dinámica de la supervivencia y el crecimiento en altura en plantines de ciprés de la cordillera (especie nativa de los bosques Andino-patagónicos de alto valor forestal) en matorrales de la Patagonia norte. Establecimos un experimento de plantación (275 plantines) en dos sitios contrastantes (un fondo de valle y una ladera de exposición norte) y durante 6 ó 7 años, dependiendo del sitio, en cada primavera registramos la supervivencia y la altura de los plantines. Evaluamos además el efecto de la protección contra herbívoros y modelamos la dinámica del ramoneo. La supervivencia y el ramoneo la evaluamos con modelos lineales generalizados, y para la altura ajustamos un modelo no lineal de efectos mixtos que permitió cuantificar la tasa de crecimiento de cada plantín. En el fondo de valle, la supervivencia disminuyó hasta menos del 15% al finalizar el experimento. En la ladera de exposición norte, la supervivencia fue más alta y se mantuvo relativamente estable. En este sitio, los valores de supervivencia (~70% al séptimo año) y crecimiento en altura (tasas mayores al 15%; IMA ~8 cm/año) fueron comparables a los reportados en plantaciones bajo bosque de ciprés de la cordillera, lo que sugiere que la especie se podría utilizar para restaurar/producir en matorrales mixtos de exposición norte. Los protectores redujeron el ramoneo, aumentaron la supervivencia, aunque no significativamente, y atenuaron el crecimiento. Por lo tanto, no es clara la conveniencia de proteger los plantines con el tipo de protector evaluado. Esperamos que nuestros resultados contribuyan con la gestión sustentable de los matorrales y bosques de la Patagonia norte.

Canadian Journal of Forest Research, 2020

Unmanned aerial vehicles (UAVs) have gained attention for forestry applications in recent years. ... more Unmanned aerial vehicles (UAVs) have gained attention for forestry applications in recent years. These technologies provide ultrahigh-resolution spatial data for detailed mapping of forest structure, among other forestry applications. UAVs have mainly been tested in high-value timber stands, but little is known about their performance in other woody ecosystems such as shrublands that also provide key ecosystem services. Field measurements in shrublands are time-consuming, so UAVs could be used instead to provide data for shrubland management and conservation. We tested whether UAVs could map common structural attributes in shrublands of northern Patagonia. We specifically evaluated the capability of UAV point clouds for mapping (i) canopy height, (ii) stand density, (iii) basal area, and (iv) volume. The agreement with the field measurements was satisfactory (R2 was up to 0.95 and relative root mean square error (rRMSE) ranged between 12% and 39%) and comparable with those found for coniferous forests in similar studies. This study is a first attempt to characterize the structure of Patagonian shrublands using UAV data. Despite the challenges and methodological aspects that need to be solved, our results encourage the use of UAVs in these types of ecosystems.

Fire is an integral process in the Earth system that varies in space and time. The fire regime co... more Fire is an integral process in the Earth system that varies in space and time. The fire regime concept captures this variability through several
parameters describing which, how many, when, and where fires occur. Quantifying fire regimes requires evidence about past fires, which can be obtained from satellite images, dendrochronology, charcoal in ediments,
operational databases, or other sources. Fire regimes are controlled by factors named drivers of fire regime (climate, biomass, fire-conducive weather, ignitions) which act and interact at different scales and are modified by human activities. To understand how fire operates on ecosystems and how humans interact with it, fire patterns must be linked to the socioecological context within which they occur. This implies going beyond the mere quantification of the parameters and expanding the fire regime definition to a more integral view. From this perspective, the fire regime concept can be applied for management of ecosystems and WUI.

Several countries have carried out surveys of managed honeybee colonies, the results of which sug... more Several countries have carried out surveys of managed honeybee colonies, the results of which suggest high loss rates all over
the world. Although Latin America is an important apicultural location, estimates of honeybee colony losses are lacking. This study quantified colony losses in Argentina during the 2015-16 season. Overall, the survey included 28,204 honeybee colonies, of which 15.5% were recorded as lost. The total winter losses (13.0%) were higher than summer losses (3.9%), a result that contrasts with that collected in Uruguay where no seasonality was observed in the 2013-14 losses. Although interesting, such inter-country variability cannot be analysed for Latin America because of the lack of simultaneous and standardized estimates of colony losses. Therefore, we developed a unified questionnaire to simultaneously record colony losses in 10 countries of Latin America in collaboration with 35 researchers. We address the readers of Bee World and ask them to help distribute the questionnaire among potentially interested parties in Latin America.

Los profesionales de las ciencias sociales y ambientales debemos resolver problemas (contestar pr... more Los profesionales de las ciencias sociales y ambientales debemos resolver problemas (contestar preguntas) a partir de la recolección y el análisis de datos. Habitualmente, todos enfrentamos dificultades similares; queremos tomar decisiones sobre una población (e.g., todos los árboles de una región), pero sólo contamos con información de una muestra (algunos árboles de esa región). Una herramienta fundamental en este proceso es plantear modelos de la población sobre la variable de interés (crecimiento los árboles en función de la edad y las condiciones climáticas) para luego utilizar sus predicciones en la toma de decisiones (turnos de corta de acuerdo a las condiciones climáticas). En esta ayuda didáctica discutimos cómo plantear, estimar y seleccionar modelos de una población a partir de los datos de una muestra. Dedicamos especial énfasis a proponer varios modelos (hipótesis) alternativos ante un mismo problema (e.g., distintas funciones del crecimiento arbóreo con la edad), los cuales son planteados antes de recolectar los datos e incluyen un modelo nulo (el crecimiento arbóreo no depende de la edad ni del clima). Los modelos nos indican cómo se deben recolectar los datos para un contraste válido (e.g., mediciones del crecimiento en árboles de edad distinta y en sitios con clima contrastante). Luego, el criterio de información de Akaike (AIC) permite ordenar los modelos según su parsimonia y seleccionar aquellos que mejor se ajusten a los datos (verosimilitud), y con menor número de parámetros (complejidad). A lo largo del texto introducimos las nociones básicas sobre la inferencia multimodelo y discutimos los errores más comunes en su uso. Proveemos ejemplos reales y hacemos disponibles los datos y los códigos de ejecución en el programa R, de acceso gratuito. Además de ser útil para los profesionales, esperamos que esta ayuda didáctica promueva la enseñanza de la inferencia multimodelo en los cursos de grado. A��. Multimodel inference in social and environmental sciences. Professionals of the social and environmental sciences must solve problems (answer questions) based on data sampling and analyses. Commonly, all professionals face similar challenges: they need to take decisions on a population (e.g., all the trees of a region), but only have data from a sample (some trees of that region). A key tool in this process is to propose population models for the response variable (tree growth as a function of tree age and climatic conditions) and then use model predictions to take decisions (e.g., when to cut trees according to climatic conditions). In this paper we discuss how to propose, estimate, and select models of a population based on sampling data. We put special emphasis in proposing several alternative models (hypotheses) to solve one problem (e.g., different tree growth functions for age), which must be proposed before data sampling, including a null model (tree growth does not depend on tree age or climatic conditions). Models guide us on how data must be sampled for a valid contrast (growth measurements in trees of different age and under contrasting climates). Then, the Akaike information criterion (AIC) can be employed to sort the most parsimonious models, selecting those with the best goodness of fit (likelihood) and the lowest number of parameters (model complexity). Along the text, we introduce basic notions of multimodel inference and discuss common user mistakes. We provide real examples, and share their data and the analyses code in R, a free and open source software. In addition to be useful to professionals from different sciences, we expect our paper to promote the teaching of multimodel inference in graduate courses.

El contenido de humedad de la vegetación es un parámetro crítico en la evaluación del peligro de ... more El contenido de humedad de la vegetación es un parámetro crítico en la evaluación del peligro de incendios. Si bien se ha avanzado en comprender su rol en el comportamiento del fuego y en su estimación por teledetección, poco esfuerzo se ha dedicado a modelar su variabilidad temporal y espacial. Nuestro objetivo fue modelar la dinámica del contenido de humedad del combustible vivo (CHCV) en pastizales del NO de la Patagonia. Desde noviembre a febrero del 2013-2014, cada 15 días, tomamos muestras de biomasa verde en dos sitios de diferente grado de aridez separados por 60 km y determinamos su contenido de humedad. Mientras el sitio húmedo (SH; 580 mm.año-1 de Pp.) representa una estepa herbácea dominada por el coirón Festuca pallescens, el sitio xérico (SX; 250 mm.año-1) corresponde a una estepa arbustiva dominada por el coirón Pappostipa speciosa y los arbustos Mulinum spinosum y Senecio filaginoides. En cada sitio establecimos tres parcelas (500 m de lado) y dentro de cada una localizamos tres puntos en los que cosechamos 100 g de combustible vivo (de F. pallecens en el SH y de P. speciosa, M. spinosum y Senecio sp en el SX). Evaluamos la dinámica del CHCV a partir de un modelo de efectos mixtos controlando la estructura espacial de los datos, con autocorrelación temporal, y con modelado de la varianza. El CHCV disminuyó desde noviembre a febrero y fue diferente entre coirones y arbustos. Los arbustos comenzaron con un CHCV del 245% y terminaron con un 70%. En cambio, el CHCV de los coirones fue más estable y siempre menor al de arbustos variando entre el 65% y el 20%. La curva temporal del CHBV fue similar entre las dos especies arbustivas pero difirió entre F. pallescens (SH) y P. speciosa (SX). La variabilidad del CHCV fue mayor en los arbustos y disminuyó con el tiempo. Los resultados pueden ser atribuidos a las diferentes estrategias de uso del agua y a diferencias morfológicas entre las especies. Modelar correctamente la variabilidad del CHCV y conocer la eco-fisiología de la vegetación especies y puede aportar herramientas valiosas al manejo del fuego.

The concerns for the effects of honey bee declines have spurred several large-scale surveys of ho... more The concerns for the effects of honey bee declines have spurred several large-scale surveys of honey bee health around the world
to evaluate potential drivers of colony losses. United States and Europe already have well developed honey bee surveys, however,
no large-scale survey has yet been developed in South America. In this paper, we present such an initiative of a national survey of
honey bee health in Argentina, which hosts the largest population of managed honey bee colonies in South America. It is also one
of the top honey-producing countries in the world. We developed a volunteer-based survey using a standardized questionnaire
and distributed it to a national network of beekeepers. The rapid mobilization and support from beekeepers shows an interest
in and a need for this type of national survey. We call for help from the readers of American Bee Journal to improve the dissemination of the questionnaire among potential interested parties in Argentina. We provide methods and recommendations to help the development of national surveys of honey bee health and also encourage such initiatives in other South American countries.

The overlapping zone between urbanization and wildland vegetation, known as the wildland urban in... more The overlapping zone between urbanization and wildland vegetation, known as the wildland urban interface (WUI), is often at high risk of wildfire. Human activities increase the likelihood of wildfires, which can have disastrous consequences for property and land use, and can pose a serious threat to lives. Fire hazard assessments depend strongly on the spatial scale of analysis. We assessed the fire hazard in a WUI area of a Patagonian city by working at three scales: landscape, community and species. Fire is a complex phenomenon, so we used a large number of variables that correlate a priori with the fire hazard. Consequently, we analyzed environmental variables together with fuel load and leaf flammability variables and integrated all the information in a fire hazard map with four fire hazard categories. The Nothofagus dombeyi forest had the highest fire hazard while grasslands had the lowest. Our work highlights the vulnerability of the wildland-urban interface to fire in this region and our suggested methodology could be applied in other wildland-urban interface areas. Particularly in high hazard areas, our work could help in spatial delimitation policies, urban planning and development of plans for the protection of human lives and assets.

Fire is one of the most important disturbances in terrestrial ecosystems and has major ecological... more Fire is one of the most important disturbances in terrestrial ecosystems and has major ecological and socioeconomic impacts. Fire regime describes the variation of individual fire events in time and space. Few studies have characterised the fire regime in grasslands in spite of the importance of these ecosystems. The aim of this study was to describe the recent fire regime (from 1973 to 2011) of northwestern Patagonian grasslands in terms of seasonality, frequency and burned area. Our study area covered 560 000 ha and we used a remote sensing approach combined with statistics obtained from operational databases. Fires occur during the summer in 2 of every 3 years with a frequency of 2.7 fires per year and a mean size of 823 ha. Fire size distribution is characterised by many small fires and few large ones which would respond to a distribution from the power law family. Eighty per cent of the total area affected by fire was burned in the span of a few years, which were also widespread fire years in forests and woodlands of northwestern Patagonia. This work contributes to general knowledge about fire regimes in grasslands and we expect that our results will serve as a reference to further fire regime research.

Journal of Arid Environments

Volcanic eruptions can cause changes in plant communities through the effects of ash fall. We stu... more Volcanic eruptions can cause changes in plant communities through the effects of ash fall. We studied the effect of ash deposition on vegetation recovery in inter-plant patches (gaps) following the eruption of the Puyehue-Cord on Caulle volcano (June 2011) in the Northwestern Patagonian steppe of Argentina. We estimated the aboveground vegetation cover and the seed bank abundance (April 2012) in gaps with and without ash (November 2011 and December 2012). We compared the sampled data with studies performed in the area before the eruption. Total plant cover was greater in gaps with ash compared to gaps without ash. Ash deposition suppressed cover of therophyte exotic species, but augmented total cover due to the increase of geophyte cover. Pre-and post-eruption soil seed bank was dominated by ther-ophytes, mostly exotic species. However, ash deposition decreased the abundance of the total seed bank, including therophyte species. The position of buds and plant size in relation to ash ...

Fire severity influences the recovery and biodiversity of plant communities. We compared the earl... more Fire severity influences the recovery and biodiversity of plant communities. We compared the early post-fire recovery of plant functional groups in two sites (one burnt with high severity and one with low severity) in the northwestern Patagonian steppe. We sampled the post-fire soil seed banks, as well as the composition and cover of aboveground plant species, and calculated richness, diversity and the percentage of exotic species. Low fire severity increased the diversity of aboveground vegetation and seed banks, whereas high fire severity reduced the cover of all functional groups, with the exception of fugitive species. Tiller production of perennial grasses decreased due to bud bank mortality. In the seed bank, high severity fire reduced fugitive species and increased exotic species. Fugitive species need fire to recruit, and the combination of fire cues and post-fire environmental conditions can explain the high abundance of these species after fire. In Patagonia, the use of fire is not considered a management option because fires are believed to be dangerous to humans, goods and services. However, north-western Patagonia is sparsely populated and the frequent wildfires pose no danger. It is necessary to increase the knowledge of the ecological processes of Patagonian ecosystems related to fire regime and land use, to achieve a reasonable balance between sustainable use and conservation in this region.

Fire recurrently affects Mediterranean-type climate (MTC) regions causing major implications on t... more Fire recurrently affects Mediterranean-type climate (MTC) regions causing major implications on the structure and dynamics of vegetation. In these regions, it is important to know the fire regime for which reliable fire records are needed. Dendroecology offers the possibility of obtaining fire occurrence data from woody species and has been widely used in forest ecosystems for fire research. Grasslands are regions with no trees where shrubs can provide dendroecological evidence for reconstructing fire history at landscape scale. We studied the dendroecological potential of the shrub Fabiana imbricata to reconstruct fire history at landscape scale in MTC grasslands of northwestern Patagonia. In order to accomplish this, we combined spatio-temporal information of recorded fires from the study area with the age structure of F. imbricata shrublands obtained from dendroecological methods. Shrubland age structure correctly described how often fires occurred in the past. In rocky outcrops, where fires cannot reach, individuals are long-lived and heterogeneous in age; while downhill, individuals are young and shrublands are evenaged. Five pulses of massive recruitment were found: three of these coincided with three known fires; the remaining two had not been recorded before. A bi-variated analysis showed that F. imbricata recruited mainly during two years after fire, and the spatial distribution of pulses coincided with the fire map. Information derived from shrubland age structure could be used to estimate fire regime parameters such as fire return interval at landscape or community scale. For instance, we estimated a fire return interval of nine years at landscape scale and ranging from 11 to 24 years at community scale (shrubland). Our results in northwestern Patagonia grasslands showed that the F. imbricata chronology can be used to complement other information sources such as remote sensing and operational databases improving the knowledge
about fire regime. The present study demonstrates that is possible to utilize shrubs as a dendroecological data source to study fire history in regions where tree cover is absent.

Fuel and Energy Abstracts, 2011

Wildland fire is a natural force that has shaped most vegetation types of the world. However, its... more Wildland fire is a natural force that has shaped most vegetation types of the world. However, its inappropriate
management during the last century has led to more frequent and catastrophic fires. Wildland
fires are also recognized as one of the sources of CO2 and other greenhouse gases (GHG) that influence
global climate change. As one of the techniques used to reduce the risk of destructive wildfires,
prescribed burning has the potential of mitigating carbon emissions, and effectively contributes to the
efforts proposed as part of the Clean Development Mechanism within the Kyoto protocol. In order to
apply this concept to a real case, a simulation study was conducted in pine afforestation in the Andean
region of Patagonia, Argentina, with the objective of evaluating the potential of prescribed burning for
reducing GHG emissions. The scenario was established for a ten year period, in which simulated prescribed
burning was compared to the traditional management scheme, which included the probability
of annual average of wildfire occurrence based on available wildfire statistics. The two contrasting scenarios
were: (1) managed afforestation, affected by the annual average rate of wildfires occurred in the
same type of afforestation in the region, without prescribed burning, and (2) same as (1) but with the
application of simulated prescribed burning. In order to estimate carbon stocks, and CO2 removals and
emissions, we followed the guidelines given for GHG inventories on the Agriculture, Forestry and Other
Land Uses (AFOLU) sector of the International Panel on Climate Change (IPCC), while the terminology
used was the established by IPCC (2003). Data of afforested area, thinnings, and biomass growth were
taken from previous surveys in the study area. Downed dead wood and litter (forest fuel load, FFL) was
estimated adjusting equations fitted to those fuels, based on field data. Results show that comparing
the two scenarios, prescribed burning reduced CO2 emissions by 44% compared to the situation without
prescribed burning. The prescribed burning scenario represented about 12% of the total emissions (prescribed
burning plus wildfires). Furthermore, avoided wildfires by simulated prescribed burning allowed
an additional 78% GHG emissions mitigation due to extra biomass growth. Simulated prescribed burning
in commercial afforestation of Patagonia appears to be an effective management practice not only to prevent
wildfires, but also an efficient tool to mitigate GHG emissions. However, more studies in different
scenarios would be needed to generalize these benefits to other ecosystems.

Fire is a critical disturbance in the structuring and functioning of most Mediterranean ecosyste... more Fire is a critical disturbance in the structuring and
functioning of most Mediterranean ecosystems. In northwestern
Patagonia, vegetation patterns are strongly influenced
by fire and environmental heterogeneity. Dendroecology,
together with satellite imagery and GIS, have been
demonstrated to be useful tools in studies that relate to fire
effects with patches, patterns and species dynamics at landscape
scale. Such studies can be approached from landscape
ecology, which has evolved in the last years supported by the
development of remote sensing and GIS technologies. This
study evaluates the spatial dynamic of F. imbricata in response
to fire using remote sensing, GIS and dendrochronology
techniques, at landscape scale. Two sites were evaluated
and one of them was affected by fire in the year 1999. The
digital processing images (using the NBR spectral index) and
the dendroecological analysis verified this. A fire, occurring
in 1978, was also detected by the analysis of F. imbricata
growth rings. The relation between F. imbricata shrubland
dynamics and spatial configuration with fire, land topography
and hydrography was established in the study area.

Conference Presentations by Facundo Oddi

Los bosques nativos proveen múltiples servicios ecosistémicos (SE). Sin embargo, las dediciones d... more Los bosques nativos proveen múltiples servicios ecosistémicos (SE). Sin embargo, las dediciones de manejo generalmente dependen de los servicios de provisión (madera, leña) y son tomadas en función de maximizar la rentabilidad económica. Nuestro objetivo fue modelar espacialmente la rentabilidad económica (Valor Actual Neto) de cinco alternativas de manejo que presentan diferente sustentabilidad ambiental (distintas intensidades de extracción leñera con/sin forestación con especies nativas o exóticas) del matorral en la provincia de Río Negro bajo diferentes escenarios financieros. En cuanto a los ingresos, la información sobre productividad fue obtenida en un experimento de largo plazo en tres tipos de matorrales. La variabilidad espacial de los egresos dependió de la distancia de transportar el producto hasta el centro de consumo más cercano y para estimarlo usamos una función que también tuvo en cuenta la dificultad del recorrido entre el pixel y la ruta. Entendiendo que el escenario financiero, reflejado por medio de la tasa de descuento, es clave en la toma de decisiones, definimos tres tasas (1,7%, 5% y 7% en dólares) y para cada una de ellas generamos un mapa con la alternativa de manejo económicamente más atractiva. Nuestros resultados demuestran que la influencia de la distancia al centro de venta depende del escenario financiero y que, bajo cada escenario, la elección del manejo depende del tipo de matorral. Este trabajo es una primera aproximación al análisis espacial del atractivo económico-financiero del manejo del matorral en el noroeste de la Patagonia. Complementar la información espacial obtenida en este trabajo con mapas de otros SE asociados al manejo pero que carecen de valor de mercado, puede aportar una herramienta clave para el manejo sustentable de estas comunidades.

Under a global change context, ecosystems are receiving high pressure and the ecology science pla... more Under a global change context, ecosystems are receiving high pressure and the ecology science play a key role
for monitoring and assessment of natural resources. To achieve an effective resources management to develop
an ecosystem functioning knowledge based on spatio-temporal perspective is useful. Satellite imagery periodically
capture the spectral response of the earth and remote sensing have been widely utilized as classification and change
detection tool making possible evaluate the intra and inter-annual plant dynamics. Vegetation spectral indices (e.g.,
NDVI) are particularly suitable to study spatio-temporal processes related to plant phenology and remote sensing
specific software, such as TIMESAT, has been developed to carry out time series analysis of spectral indexes. We
used TIMESAT software applied to series of 25 years of NDVI bi-monthly composites (240 images covering the
period 1982-2006) from the NOAA-AVHRR sensor (8 x 8 km) to assessment plant pheonology over 900000 ha of
shrubby-grasslands in the Northwestern of Patagonia, Argentina. The study area corresponds to a Mediterranean
environment and is part of a gradient defined by a sharp drop west-east in the precipitation regime (600 mm to 280
mm). We fitted the temporal series of NDVI data to double logistic functions by least-squares methods evaluating
three seasonality parameters: a) start of growing season, b) growing season length, c) NDVI seasonal integral.
According to fitted models by TIMESAT, start average of growing season was the second half of September (± 10
days) with beginnings latest in the east (dryer areas). The average growing season length was 180 days (± 15 days)
without a clear spatial trend. The NDVI seasonal integral showed a clear trend of decrease in west-east direction
following the precipitation gradient. The temporal and spatial information allows revealing important patterns of
ecological interest, which can be of great importance to environmental monitoring. In this work we also show as
utilizing TIMESAT to characterize the plant phenology at regional scale.

Fires at landscape level are result from complex interactions among ignitions, weather and vegeta... more Fires at landscape level are result from complex interactions among ignitions, weather and vegetation. Factors
related to fire, such as fuel moisture, vegetation structure and topography, can exhibit substantial spatial and
temporal variability. Arrangements of patches with different degree of burn severity are found after to fire and this
heterogeneity could have major implications for ecosystem processes. For instance, severely burned patches may
be more affected by fire returning to pre-fire conditions in a large time period while areas with low burn severity
may be seed sources accelerating the plant recovery process.
Interactions between fire severity, type vegetation and others environmental factors are poorly known, in particular
in large fires. For overcome this lack, the first step is rely on accurate data regarding fire severity at landscape
scale.
Remote sensing tools are particularly suitable assessment fire effects at landscape scale, where monitoring the
entire surface affected by large fires is laborious. In addition, the integration into a GIS of data obtained by remote
sensing facilitates to explore causal relationships involved in fire severity and the influence of them in the recovery
process. In this context, spectral indices can be used to relate burn severity observed in the surface to values
measured by the satellite sensor. One of the most widely used indices is the “Normalized Burn Ratio” (NBR)
which enables to infer the degree of post-fire ecological change.
Nevertheless, in heterogeneous landscapes, to map fire effects may be required pre-disturbance data in addition to
post-disturbance image, because precisely to non-homogeneity conditions. Thus, two NBR derivatives, delta-NBR
(dNBR) and Relative delta-NBR (RdNBR), have been developed to remove biasing of the pre-fire vegetation
present in the uni-temporal approach. To difference of dNBR, in which it is obtained an absolute change value,
RdNBR is a relative measure that allows independence from the pre-fire condition of vegetation.
Considering that: 1) the dNBRand RdNBR indexes are proposed to evaluate fire severity by remote sensing in
different environments and 2) exist few information about its behavior in communities with low biomass load as
the semiarid grasslands. Then, the general objective of work was to analyze and compare the behavior of dNBR
and RdNBR in their ability to discriminate the degrees of fire severity in semiarid environments dominated by
herbaceous vegetation.

Fire recurrently affects many of the terrestrial ecosystems causing major implications on the str... more Fire recurrently affects many of the terrestrial ecosystems causing major implications on the structure and dynamics
of vegetation. In fire prone, it is particularly important to know the fire regime for which precise fire records are
needed. Dendroecology offers the possibility of obtaining fire occurrence data from woody species and has been
widely used in forest ecosystems for fire research. Grasslands are regions with no trees but shrubs could be used
to acquire dendroecological information in order to reconstructing fire history at landscape scale. We studied
the dendroecological potential of shrub F. imbricata to reconstruct fire history at landscape scale in a fire prone
grassland of northwestern Patagonia. To do this, we combined spatio-temporal information of recorded fires within
the study area with the age structure of F. imbricata shrublands derived by dendroecology. Sampling sites were
located over 2500 ha in San Ramón ranch, 30 km east from Bariloche, Río Negro province, Argentina (latitude
-41 04’; longitude -70 51’). Shrubland age structure correctly described how fires occurred in the past. Pulses of
individuals’ recruitment were associated with fire in time and space. A bi-variate analysis showed that F. imbricata
recruits individuals during the two years after fire and spatial distribution of pulses coincided with the fire map.
In sites without fire data, the age structure allowed the identification of two additional fires. Our results show that
shrub F. imbricata can be employed with other data sources such as remote sensing and operational databases to
improve knowledge on fire regime in northwestern Patagonia grasslands. In conclusion, we raise the possibility of
utilizing shrubs as a dendroecological data source to study fire history in grasslands where tree cover is absent.

Conservation Letters, 2020

Ecología Austral, 2021

Canadian Journal of Forest Research, 2020

Journal of Arid Environments

Fuel and Energy Abstracts, 2011

Landscapes are dynamic in space and time, being spatio-temporal processes of particular interest ... more Landscapes are dynamic in space and time, being spatio-temporal processes of particular interest for landscape
ecology. In particular, grasslands can change their structure through the expansion of shrubs in the landscape
matrix. Shrub encroachment affect biodiversity as well as forage availability that is the key component of the productive
use of rangelands. However, despite its recognition as a global problem, knowledge on the rates, dynamics
and encroachment patterns is even scarce. For example, although it is generally accepted that fire control shrub encroachment,
certain shrubby species could be favored by the occurrence of fire. In northwestern Patagonian steppe,
Fabiana imbricata form large monospecific shrublands that are part of the landscape mosaic and its dynamics of
regeneration is strongly related to fire. This long-lived shrub ( 150 years) is a typical seeder that is killed by fire
and recruits seedlings almost exclusively in post-fire, establishing even-age patches. Our objective was to determine
whether F. imbricata shrublands have expanded during the last 40 years in a landscape fire prone. The study
area corresponds to San Ramon ranch (22,000 ha) located in northwestern Patagonia steppe, Argentina (latitude
-41 04’; longitude -70 51’). Two distribution maps of the species were made that corresponds to the study area
in 1968 and 2011. The 1968 map was elaborated from the digitalization of aerial photographs (1:45000) while
the 2011 map was produced with very high resolution satellite images, current aerial photographs and GPS field
data. Both maps were loaded into a GIS environment, in which landscape metrics at patch and class level were
determined and then compared. From remote sensing and dendroecological techniques, we know that the study
area was almost entirely affected by fires during the study period. Therefore, the comparison of both maps allows
us to know post-fire changes in the shrublands spatial configuration at the landscape scale and to infer the fire
effect on these changes. Our results show that during the studied period F. imbricata shrublands has expanded over
the grassland. Nowadays, the species occupies 20% more area than in 1968 and this area, is divided into a smaller
number of patches that are closer to each other. The observed change in the shrublands spatial pattern is evidence
of a post-fire shrub encroachment. These results contribute to the understanding of the role of fire in vegetation
dynamics in fire prone ecosystems.

Fabiana imbricata en el noroeste de la Patagonia a escala de paisaje. Su relación con factores am... more Fabiana imbricata en el noroeste de la Patagonia a escala de paisaje. Su relación con factores ambientales y el uso del suelo. Presentación oral libre. Facundo José Oddi. Lab. Ecotono -Instituto de Biodiversidad y Medioambiente (INIBIOMA) -Universidad nacional del Comahue (UNCo). Calle Quintral 1250, Bariloche, Río Negro.

Fire is one of the most important disturbances on the Earth affecting most terrestrial ecosystems... more Fire is one of the most important disturbances on the Earth affecting most terrestrial ecosystems. Evidence suggests that since the last glaciations there has been a substantial interaction among climate, vegetation and fire. In fact fire is recognized as an emergent property of climate and vegetation type, which determine that distinct regions are differently affected by wildfires. For instance, it has been suggest that relative roles of weather/climate and fuel on fire activity change along the global productivity/aridity (intermediate fire-productivity hypothesis). At one extreme of the gradient we find dry-unproductive regions (deserts) where fire is absent owing to very low fuel loads, while at the other extreme we have wet-productive environments (rain forest) with fire being unlikely due to high fuel moisture. Environments located around middle of the gradient, such as Mediterranean ecosystems, have a high fire activity but is difficult to predict if the fuel moisture conditions are a stronger constrain on the fire regime or it is constrained by biomass production (i.e. fuel load). The intermediate fire-productivity hypothesis has been tested in recent works at global scale. However, data resolution at global scale is coarse and thus is not possible know the fire variability occurring at scales of more spatial detail. Therefore, it is necessary to complement the information obtained at global scale with studies at finer scales exploring fire-productivity/aridity relationships in particular portions of the gradient. We elaborate fire cartography from Landsat temporal series for a portion (560250 ha -regional scale) of northwestern Patagonian steppe. The study zone corresponds to a Mediterranean environment and is part of a gradient defined by a sharp drop in the precipitation regime (600mm to 280mm). This environmental gradient predisposes a change in fuel load and fuel moisture and therefore could be affecting the fire regime. We divided the study area in relation to precipitation gradient establishing two zones (wet and xeric). To delimit area of wildfires on Landsat scenes we used the NBR index. Then, we calculated the annual burned area in each zone, compared the annual burned area between zones and also explored relationships between that variable of the fire regime and precipitation/temperature data. We expect to contribute to the discussions about the importance of drought/fuel on the fire activity across the productivity/aridity gradient, specifically on Mediterranean environments. Finally, with this work we expect to improve future management and conservation practices in Northwestern Patagonia grasslands.

One way to reflect accurately on a particular geographic region the spatial distribution of a pop... more One way to reflect accurately on a particular geographic region the spatial distribution of a population, community or ecological phenomenon (of discrete nature) is to represent in a cartographic the elements that form part of it. In real ecosystem non-random distribution in space is the most common due individuals and populations live in heterogeneous habitats in space and time. The study of patterns related to spatial structures is part of the discipline called "Spatial Analysis", which contains a large set of techniques that have as aim the quantitative analysis of spatially explicit data. The importance of taking into account the space in the ecology is due to this can determine how spatial structure influences ecological processes and, conversely, how these processes can affect the structure. The analysis of the spatial point pattern tries to answer questions like: What is the spatial pattern of individuals or patches of a species? Is there spatial interaction between two or more species? What is the scale at which take place these patterns? Observed patterns are generated by an ecological process or are due to the heterogeneous environment? What are the characteristics or attributes of the species associated with the spatial pattern? The advance of information technology has allowed the spatial simulation models to compare real and simulated patterns and then determine the pattern found in the system. Geographic information technologies (remote sensing, GPS and GIS) have facilitated the real data collection and processing since allows the precise location of individuals and populations. The Patagonia northwestern steppe region is characterized by a high environmental heterogeneity where fire and grazing disturbances appears as influential factors in the landscape structure due to its effect modifier of the plant mosaic. The aim of this is research is to characterize the spatial pattern found in the Fabiana imbricata shrublands over an area of 23000 ha. The species of study is a typical shrub of NW Patagonia that forms dense shrublands where its dynamics seems to be strongly related to fire, and probably grazing. From high-resolution satellite images and walk round with GPS in the field were digitized Fabiana imbricata patches. The data were processed with GIS software to reflect the spatial structure of these patches and then converted to files valid for to use in the "Programmita" software (which quantifies spatial patterns). Characterizing the spatial structure of these shrubs is initially a descriptive work, but is the first step to infer whether such structure is the result of environmental heterogeneity or whether is part a dynamic population that may be related to common disturbances in the study area, like as fire and grazing.

Fire is a major environmental ecological agent acting in the landscape configuration and a factor... more Fire is a major environmental ecological agent acting in the landscape configuration and a factor that models vegetation in Mediterranean environments. Fire impacts differently in the landscape due to the intrinsic heterogeneity of the environments and the characteristics associated with each fire event. After fire, density of patches may be increased and the size of them may be reduced because fire generates areas of different successional stages. Landscape ecology seems to be the ideal theoretical approach to study the fire impact in fire prone environments. Landscape ecology has been greatly favoured by a significant progress in the last years of geographic information technologies (GIT) (remote sensing, GIS, GPS). The study area of this work is the San Ramon ranch (22,000 ha) located in Northwester Patagonia in the ecotone between the sub Antarctic forest in the West and the Patagonian steppe in the East. We studied sectors of the ranch with different fire recurrence in the last 40 years and we mapped Fabiana imbricata shrubland with GPS. This specie is a native shrub characteristic of Northwester Patagonia grasslands and its dynamic is not very known. Shrublands compete for the space with palatable grasses that are used for forage and livestock production, the main economic resource of the region. We analysed the mapped patches with GIS software, and we assessed landscape metrics to determine differences between sites with different fire recurrence. In the future we foresee the integrated use of satellite imagery with different resolution to add to GIS other important spatial variables (topography, hydrography, aspect, soil) to develop models that can explain landscape metrics, spatial configuration and the potential shrub invasion in the grassland.

Wildfires can cause an environment deterioration modifying vegetation dynamics because they have ... more Wildfires can cause an environment deterioration modifying vegetation dynamics because they have the capacity of changing vegetation diversity and physiognomy. In semiarid regions, like the northwestern Patagonia, fire disturbance is also important because it could impact on the potential productivity of the ecosystem. There is reduction plant biomass and with that reducing the animal carrying capacity and/or the forest site quality with negative economics implications. Therefore knowledge of the fires regime in a region is of great importance to understand and predict the responses of vegetation and its possible effect on the regional economy. Studies of this type at a landscape level can be addressed using GIS tools. Satellite imagery allows detect burned areas and through a temporary analysis can be determined to fire regime and detecting changes at landscape scale. The study area of work is located on the east of the city of Bariloche including the San Ramon Ranch (22,000 ha) and its environs in the ecotone formed by the sub Antarctic forest and the patagonian steppe. We worked with multiespectral Landsat TM images and Landsat ETM + 30m spatial resolution obtained at different times. For the spatial analysis we used the software Erdas Imagine 9.0 and ArcView 3.3. A discrimination of vegetation types has made and was determined areas affected by fires in different years. We determined the level of change on vegetation induced by fire. In the future the use of high spatial resolution images combined with higher spectral resolution will allows distinguish burned areas with greater precision on study area. Also the use of digital terrain models derived from satellite imagery associated with climatic variables will allows model the relationship between them and the dynamics of vegetation.