Juan Paritsis

Ecological and climatic controls of modern wildfire activity patterns across southwestern South America

Understanding how patterns of wildfire activity across biomes are shaped by heterogeneity in biomass resources to burn and atmospheric conditions conducive to burning is a high research priority in the context of global environmental change. Along a latitudinal gradient (25 to 56° S) from semi-arid scrublands through Mediterranean-type vegetation to wet forests in southwestern South America (SSA) we analyzed influences of mean climate and interannual climate variability on fire activity using documentary fire records from 1984 to 2008. We identified large regions with common temporal variability in annual area burned, related this variability to local interannual climate variability and in turn to modes of the major tropical and extratropical climate drivers of the southern hemisphere—El Nino-Southern Oscillation (ENSO) and the Antarctic Oscillation (AAO). Differences in fire activity response to interannual climate variability were related to the relative influences of available biomass to burn, and to weather effects on amounts of fine fuels and fuel moisture conditions. The pattern of average fire activity along this latitudinal moisture/productivity gradient corresponds well with the varying constraints model. This model predicts low fire activity towards the arid extreme due to reduced burnable biomass and again towards the humid extreme due to infrequent weather suitable for drying fuels, and predicts a broad zone of high fire activity at intermediate locations where resources to burn are abundant in all years and fuel moisture dries under reliably dry summer conditions. The dominant influence on interannual climate variability is AAO, which explained most of the variability in fire activity both by reducing seasonal precipitation in mesic and wet forests where fire is dependent on infrequent drought and by enhancing fine fuel production in Mediterranean-type vegetation where fuel amount and continuity constrain fire activity. In the context of the drying and warming trends in SSA related to the continued positive anomaly in AAO, our results underscore the importance of the varying constraints on fire activity and modulation of fire-climate relationships by different vegetation types, which is a much needed step toward developing fire projections under future climate.

Assessing dendroecological methods to reconstruct defoliator outbreaks on Nothofagus pumilio in northwestern Patagonia, Argentina.

We examined the use of dendroecological techniques for detecting past defoliations caused by Ormiscodes amphimone Fabricius (Saturniidae) in Nothofagus pumilio (Poepp. et Endl.) Krasser forests in northwestern Patagonia. We evaluated the suitability of the conifer Austrocedrus chilensis (D. Don) Pic. Serm. et Bizarri as a nonhost climate control for reconstructing Ormiscodes outbreaks on N. pumilio. Additionally, we assessed the effectiveness of three alternative procedures to detect past outbreaks: the use of a regional host chronology (instead of the nonhost chronology), the detection of pointer years (i.e., extremely narrow tree rings caused by defoliation), and the use of a morphological tree-ring signature associated with defoliation. Although differences in tree-ring growth response to climate between N. pumilio and A. chilensis did not support the use of the latter species as a reliable climatic control in most of our study area, the alternative procedures were effective in detecting past defoliati...

Habitat distribution modeling reveals vegetation flammability and land use as drivers of wildfire in SW Patagonia

Despite important recent advances in modeling current and future global fire activity in relation to biophysical predictors there remain important uncertainties about finer-scale spatial heterogeneity of fire and especially about human influences which are typically assessed at coarse-spatial resolutions. The purpose of the current study is to quantify the influence of biophysical and anthropogenic variables on the spatial distribution of wildfire activity between 1984 and 2010 over an extensive southern Patagonian-Andean region from ca. 43° to 53° S extending from coastal rainforests to xeric woodland and steppe. We used satellite imagery to map all detectable fires >5 ha from 1984 to 2010 in four study areas (each of 13,100 to 36,635 km 2 ) and field checked 65 of these burns for accuracy of burned vegetation class and fire perimeters. Then, we used the MaxEnt modeling technique to assess the relationships of wildfire distributions to biophysical and human environmental variables in each of the four regions. The 232 fires >5 ha mapped in the four study areas accounted for an area of 1,314 km 2 indicating that at least 1.8% of the total area burned between 1984 and 2010. In general, areas with intermediate productivity levels (e.g., shrublands) have higher fire probability compared with areas of low and high productivity levels, such as steppe and wet forests, respectively. There is a marked contrast in the flammability of broad vegetation classes in determining fire activity at a regional scale, as well as a strong spatial relationship of wildfires to anthropogenic variables. The juxtaposition of fire-resistant tall forests with fire-prone shrublands and woodlands creates the potential for positive feedbacks from human-set fires to gradually increase the flammability of extensive landscapes through repeated burning. Distance to roads and settlements were also strong predictors, suggesting that fire in all regions is ignition-limited. However, these anthropogenic predictors influenced probability of fire differently among study regions depending on their main land-use practices and their past and present socioeconomic contexts.

Fire-Vegetation Feedbacks and Alternative States: Common Mechanisms of Temperate Forest Vulnerability to Fire in Southern South America and New Zealand

ABSTRACT In the context of global warming and increasing impacts of invasive plants and animals, we examine how positive fire–vegetation feedbacks are increasing the vulnerability of pyrophobic temperate forests to conversion to pyrophytic non-forest vegetation in southern South America and New Zealand. We extensively review the relevant literature to reveal how these temperate southern hemisphere floras have generated similar positive fire–vegetation feedback mechanisms resulting in increased vulnerability to anthropogenically altered fire regimens. For the two regions, we address the following questions. 1. What are the major plant species, physiognomic types and functional types characteristic of pyrophytic versus pyrophobic vegetation types and how do their traits affect flammability, resistance to fire and recovery after fire? 2. What are the roles of herbivory and microclimate in enhancing fire–vegetation feedbacks? 3. Are there similarities in trends of cover type transitions in relation to altered fire regimens? 4. How are climate change, land-use trends and the effects of introduced plants and animals affecting the vulnerability of these ecosystems to fire-induced transitions to alternative stable states? Most temperate forests of New Zealand and southern South America evolved under conditions of low fire frequencies so few taxa became adapted to recurrent fire. Current dichotomous landscapes consisting of juxtaposed pyrophobic and pyrophytic vegetation types are the outcome of the expansion of fire-resilient and fire-promoting species associated with the arrival of humans. Despite considerable differences in human history and biogeographic history, the case studies presented here show remarkable parallels in life-history traits of the key pyrophobic taxa, fire–vegetation feedback mechanisms, overall ecosystem responses to anthropogenic alteration of fire regimens, and likely vulnerability to expected global change influences on future fire regimens.

Temperature and foliage quality affect performance of the outbreak defoliator Ormiscodes amphimone (F.) (Lepidoptera: Saturniidae) in northwestern Patagonia, Argentina.

En los bosques templados de Chile y Argentina la polilla fitofaga Ormiscodes amphimone (F.) genera severas defoliaciones sobre la lenga (Nothofagus pumilio [Poepp. & Endl.] Krasser). El reciente aumento en la frecuencia de defoliacion en algunas areas de la Patagonia pareceria estar influenciada por un clima mas calido. Para evaluar los efectos de la temperatura y la heterogeneidad espacial en la calidad del follaje sobre el desempeno y la tasa de consumo relativo del defoliador O. amphimone en el noroeste de la Patagonia argentina llevamos a cabo un experimento factorial. El desempeno larval fue medido como tasa de crecimiento relativo, tiempo de desarrollo, supervivencia larval y peso de las pupas. Las larvas de O. amphimone fueron criadas bajo dos temperaturas constantes (15 °C y 20 °C) y alimentadas con dos tipos de follaje de N. pumilio (de un sitio mesico y de uno xerico). Las larvas criadas a la temperatura mas alta y alimentadas con hojas del sitio mesico exhibieron desempenos y tasas de consumo mas elevadas que las larvas en los otros tratamientos. La temperatura mas alta y el follaje del sitio mesico tuvieron efectos positivos en la tasa de crecimiento relativo, el tiempo de desarrollo y la tasa de consumo relativo. Sin embargo, el peso de las pupas fue influenciado positivamente por el follaje mesico pero no por la temperatura, y la supervivencia larval no mostro diferencias significativas entre tratamientos. Nuestros resultados sugieren preliminarmente que el desempeno y la tasa de consumo de O. amphimone podrian aumentar bajo condiciones de temperatura mas elevadas, especialmente en los sitios mesicos del gradiente de precipitacion. Sin embargo, estos resultados deben ser interpretados en forma prudente ya que mas estudios son necesarios para evaluar los efectos de temperaturas elevadas sobre la calidad foliar de N. pumilio.

Southern Annular Mode drives multicentury wildfire activity in southern South America

Significance Fire is a key ecological process affecting ecosystem dynamics and services, driven primarily by variations in fuel amount and condition, ignition patterns, and climate. In the Southern Hemisphere, current warming conditions are linked to the upward trend in the Southern Annular Mode (SAM) due to ozone depletion. Here we use tree ring fire scar data obtained from diverse biomes ranging from subtropical dry woodlands to sub-Antarctic rainforests to assess the effect of the SAM on regional fire activity over the past several centuries. Our findings reveal a tight coupling between fire activity and the SAM at all temporal scales and in all biomes, with increased wildfire synchrony and activity during the 20th century compared with previous centuries. The Southern Annular Mode (SAM) is the main driver of climate variability at mid to high latitudes in the Southern Hemisphere, affecting wildfire activity, which in turn pollutes the air and contributes to human health problems and mortality, and potentially provides strong feedback to the climate system through emissions and land cover changes. Here we report the largest Southern Hemisphere network of annually resolved tree ring fire histories, consisting of 1,767 fire-scarred trees from 97 sites (from 22 °S to 54 °S) in southern South America (SAS), to quantify the coupling of SAM and regional wildfire variability using recently created multicentury proxy indices of SAM for the years 1531–2010 AD. We show that at interannual time scales, as well as at multidecadal time scales across 37–54 °S, latitudinal gradient elevated wildfire activity is synchronous with positive phases of the SAM over the years 1665–1995. Positive phases of the SAM are associated primarily with warm conditions in these biomass-rich forests, in which widespread fire activity depends on fuel desiccation. Climate modeling studies indicate that greenhouse gases will force SAM into its positive phase even if stratospheric ozone returns to normal levels, so that climate conditions conducive to widespread fire activity in SAS will continue throughout the 21st century.

New host-plant records for the defoliator Ormiscodes amphimone (Fabricius) (Lepidoptera: Saturniidae).

Ormiscodes amphimone (Fabricius) is a phytophagous moth species known to severely defoliate woody species in Chile and Argentina. Here we document new records of O. amphimonehost associations emphasizing the role of Nothofagus pumilio as its primary host in our study area. This new record for Argentina is highly significant given the economic importance of N. pumilio as a timber resource and the potential of O. amphimone to generate extensive outbreaks.

Spatial prediction of caterpillar (Ormiscodes) defoliation in Patagonian Nothofagus forests

In the temperate forests of the southern Andes, southern beech species (Nothofagus), the dominant tree species of the region, experience severe defoliation caused by caterpillars of the Ormiscodes genus (Lepidoptera: Saturniidae). Despite the recent increase in defoliation frequency in some areas, there is no quantitative information on the spatial extent and dynamics of these outbreaks. This study examines the spatial patterns of O. amphimone outbreaks in relation to landscape heterogeneity. We mapped defoliation events caused by O. amphimone in northern (ca. 40–41°S) and southern Patagonian (ca. 49°S) Nothofagus forests from Landsat imagery and analyzed their spatial associations with vegetation cover type, topography (elevation, slope angle, aspect) and mean annual precipitation using overlay analyses. We used these data and relationships to develop a logistic regression model in order to generate maps of predicted susceptibility to defoliation by O. amphimone for each study area. Forests of N. pumilio are typically more susceptible to O. amphimone outbreaks than lower elevation forests of other Nothofagus species (N. dombeyi and N. antarctica). Stands located at intermediate elevations and on gentle slopes (<15°) are also more susceptible to defoliation than higher and lower elevation stands located on high angle slopes. Stands in areas with intermediate to high precipitation, relative to the distribution of Nothofagus along the precipitation gradient, are more susceptible to O. amphimone attack than are drier areas. Our study represents the first mapping and spatial analysis of insect defoliator outbreaks in Nothofagus forests in South America.

Influences of fire–vegetation feedbacks and post‐fire recovery rates on forest landscape vulnerability to altered fire regimes

1Smithsonian Conservation Biology Institute, Front Royal, VA, USA; 2Department of Mathematics, Oregon State University, Corvallis, OR, USA; 3Department of Geography, University of Colorado at Boulder, Boulder, CO, USA; 4School of Environment, University of Auckland, Auckland, New Zealand; 5Department of Geography, Portland State University, Portland, OR, USA; 6Laboratorio Ecotono, INIBIOMA, CONICET-Universidad Nacional del Comahue, Bariloche, Río Negro, Argentina; 7Departamento de Ecología, Universidad Nacional del Comahue, Bariloche, Río Negro, Argentina and 8Center for Tropical Forest Science– Forest Global Earth Observatory, Smithsonian Tropical Research Institute, Panama

Mortality of the outbreak defoliator Ormiscodes amphimone (Lepidoptera: Saturniidae) caused by natural enemies in northwestern Patagonia, Argentina

Fil: Paritsis, Juan. State University Of Colorado - Fort Collins; Estados Unidos. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Patagonia Norte. Instituto de Investigacion en Biodiversidad y Medioambiente; Argentina