Contrasting effects of grazing on the early stages of woody encroachment in a Neotropical savanna

Woody encroachment in savannas represents an ecological process of current global interest given its negative impact on ecosystem functioning, particularly on forage production. Traditional savanna models propose competition and niche differentiation as the main mechanisms allowing tree-grass coexistence. Demographic models, instead, propose abiotic and biotic factors as bottlenecks controlling vital rates and transitions from seeds to adult trees. The role played by domestic grazing on woody encroachment is yet controversial. Here, using a multistage tree life approach, we combine both models and evaluate the role of grazing and herbaceous vegetation on woody recruitment in a Neotropical savanna dominated by Vachellia caven, a successful and widely spread encroacher tree species. We performed three experiments to evaluate seed predation, seedling emergence and survival of V. caven by manipulating cattle grazing (grazed and ungrazed areas) and herbaceous vegetation presence (vegetated and unvegetated). Finally, we combined the results of the three experiments to estimate the probability of plant recruitment across these experimental factors. Grazing decreased seed predation by half, did not modify seedling emergence and decreased seedling survival. Herbaceous vegetation did not affect seed predation nor seedling emergence rate, but increased seedling survival. Overall, the net effect of grazing on V. caven recruitment was neutral since the increase in seed availability due to the reduction in seed predation rate was compensated by the negative effect of grazing on seedling survival. Our analysis revealed that cattle grazing and herbaceous vegetation had contrasting effects on the seed and seedling life stages. We propose that in order to restrain the early stages of encroachment, cattle grazing pressure could be managed following the seasonality of demographic tree transitions. Through rotational grazing amongst paddocks, stocking rates could be relaxed during the primary dispersal stage to maximize granivory, and then increased to enhance the chance of seedling consumption and trampling.Fil: Mochi, Lucia Sol. Universidad de Buenos Aires. Facultad de Agronomía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario; ArgentinaFil: Mazía, Cristina Noemí. Universidad de Buenos Aires. Facultad de Agronomia. Departamento de Producción Vegetal. Cátedra de Dasonomia; ArgentinaFil: Biganzoli, Fernando. Universidad de Buenos Aires. Facultad de Agronomía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario; ArgentinaFil: Aguiar, Martin Roberto. 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; Argentin

Impacto de la deposición de ceniza volcánica sobre la productividad foliar y la herbivoría por insectos en bosques deciduos del norte de la Patagonia

Volcanism has been a major force shaping the dynamics of Andean landscapes during the Holocene. Yet we still know little about the consequences of modern volcanic events on forest functioning. Ash fall may elicit multiple direct and indirect effects on key ecosystem attributes, with disturbance severity likely varying with distance to the crater. We examined the impact of ash deposition on foliage productivity and insect herbivory after the 2011 eruption of the Volcán Puyehue-Cordón Caulle system, in Nothofagus pumilio forests of northern Patagonia, Argentina. Tree leaf litterfall, a surrogate for annual foliar production, was measured before and after the event in wet and dry forest sites, which were located 22 km and 80 km east from the crater and were affected by mass deposition of coarse- and fine-grained tephra, respectively. Leaf damage by insects was monitored over a 10-year span (2004-2013) including the volcanic event. Foliar productivity in 2012 dropped by 60% in the wet forest, but did not change in the dry forest. Leaf area damaged by insects decreased abruptly in 2012, with post-eruption herbivory levels falling outside the range of annual variation recorded before the event. The impact was most severe in the dry forest wich normally supports the highest endemic herbivory. In contrast, leaf damage remained high in another dry forest located 98 km southeast from the crater and little affected by ashfall. Changes in foliar production and insect herbivory persisted for two years after the event. Our results show a widespread disruption of canopy-herbivore interactions in areas heavily affected by tephra. Remarkably, volcanic ash acted as a broad-spectrum insecticide on canopy herbivores. In the short-term, ashfall constrained the energy flow through the forest canopy and the arthropod consumer community, and thus temporarily overwhelmed previously existing differences in productivity and herbivory between wet and dry forest habitats.Impacto de la deposición de ceniza volcánica sobre la productividad foliar y la herbivoría por insectos en bosques deciduos del norte de la Patagonia: El vulcanismo ha moldeado la dinámica de los paisajes andinos durante todo el Holoceno. Sin embargo, aún se conoce poco sobre las consecuencias de eventos volcánicos modernos en el funcionamiento de los bosques nativos. La caída masiva de cenizas puede generar múltiples efectos directos e indirectos sobre procesos clave del ecosistema. Aquí evaluamos el impacto de la deposición de cenizas emitidas por la erupción del complejo Volcán Puyehue-Cordón Caulle en junio de 2011, sobre la productividad foliar y la herbivoría por insectos del dosel en bosques de Nothofagus pumilio del norte de la Patagonia Argentina. La producción de hojas fue medida antes y después de la erupción, en bosques húmedos y secos situados a 22 y 80 km del volcán y afectados por la caída de pumicita gruesa y fina, respectivamente. El área foliar dañada por insectos fue monitoreada durante 10 años (2004-2013), incluyendo al evento volcánico. La productividad foliar en 2012 cayó un 60% en el bosque húmedo pero no cambió en el bosque seco. El daño foliar se redujo abruptamente en 2012; los niveles de herbivoría post-erupción cayeron por debajo del rango de variación interanual registrado antes de la erupción. El impacto fue más severo en el bosque seco, donde los niveles endémicos de herbivoría son más elevados. En cambio, la herbivoría se mantuvo elevada en otro bosque seco localizado a 98 km del cráter y que recibió pocas cenizas. Los cambios en productividad y herbivoría persistieron por dos años después del evento. Estos resultados muestran una fuerte disrupción de las interacciones planta-herbívoro en áreas boscosas afectadas por la erupción volcánica. Las cenizas actuaron como un biocida de amplio espectro sobre los insectos defoliadores. En el corto plazo, la deposición de cenizas limitó el flujo de energía a través del dosel arbóreo y hacia los consumidores artrópodos.Fil: Chaneton, Enrique Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas A la Agricultura; ArgentinaFil: Mazía, Noemí. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal; ArgentinaFil: Garibaldi, Lucas Alejandro. Universidad Nacional de Rio Negro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Chaij, Jaquelina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal; ArgentinaFil: Kitzberger, Thomas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; Argentin

Grazing and neighborhood interactions limit woody encroachment in wet subtropical savannas

Woody encroachment in savannas is a worldwide concern, and there is growing consensus that anthropogenic activities play a central role in changing tree – grass interactions. We evaluated the influence of livestock grazing and neighborhood interactions on seedling emergence and survival of the native tree Acacia caven in wet savannas of northeastern Argentina. We hypothesized that grazing and grass competition act as biotic barriers limiting tree recruitment, but the relative magnitude of such barriers differs according to grass patch type. In two consecutive years (cohort 1 and 2) we sowed seeds and transplanted seedlings of Acacia in two grass patch types (prostrate/palatable and tussock/unpalatable grasses) in both, grazed and ungrazed plots. Each grass patch type was further manipulated to create three levels of grass competition (unclipped control, above-ground biomass removal and total biomass removal). Cattle grazing diminished seedling emergence of both cohorts and seedling survival of cohort 1. The effect of grass competition changed according to grass patch type. Prostrate grass cover enhanced emergence but lowered early survival, while tussock grass cover and also its total biomass removal facilitated early survival. During the second year, a severe drought drastically reduced Acacia recruitment, and it was strong enough to eliminate any grazing effects although the effect of grass competition on seedling establishment remained significant. Our results suggest that grazing and grass competition additively diminished the risk of woody establishment in this wet savanna. However, the stocking rate should be carefully balanced, thus contributing to the maintenance of a competitive grass cover to limit tree recruitment.Das Vordringen von Gehölzen in Savannen wird weltweit mit Besorgnis registriert, und es gibt eine zunehmende Übereinstimmung, dass menschliche Aktivität eine zentrale Rolle bei der Veränderung von Baum-Gras-Interaktionen spielt. Wir ermittelten den Einfluss von Beweidung durch Vieh und Nachbarschaftsinteraktionen auf das Auftreten von Sämlingen und das Überleben der einheimischen Baumart Acacia caven in Feuchtsavannen im nordöstlichen Argentinien. Wir erwarteten, dass Beweidung und Konkurrenz von Gräsern als biotische Barrieren fungieren, die den Aufwuchs von Bäumen limitieren, aber das relative Ausmaß dieser Barrieren sollte mit dem Grastyp variieren. In zwei aufeinander folgenden Jahren (Kohorten 1 und 2) säten wir Akazien-Samen und verpflanzten Jungpflanzen in zwei unterschiedlichen Grasbeständen (niederliegend/genießbar und horstartig/ungenießbar), jeweils mit und ohne Beweidung. Alle Grastypen wurden desweiteren manipuliert, um drei Stufen von Konkurrenz durch Gräser herzustellen: unbehandelte Kontrolle, Erntfernung der oberirdischen Grasbiomasse, Entfernung der gesamten Biomasse. Die Beweidung durch Rinder verminderte das Auftreten von Sämlingen in beiden Kohorten und das Überleben der Sämling in Kohorte 1. Der Einfluss der Konkurrenz durch Gräser variierte mit dem Grastyp. Niederliegendes Gras begünstigte das Auftreten von Keimlingen, verringerte aber das frühe Überleben, während Horstgräser aber auch ihre vollständige Entfernung das frühe Überleben begünstigten. Im zweiten Jahr reduzierte eine strenge Dürreperiode den Nachwuchs der Akazien, und sie war stark genug, Beweidungseffekte zu eliminieren, obwohl der Effekt der Konkurrenz durch Gräser signifikant blieb. Unsere Ergebnisse legen nahe, dass Beweidung und Konkurrenz durch Gräser zusammengenommen das Risiko einer Verwaldung in dieser Feuchtsavanne verringerten. Indessen sollte die Besatzdichte mit Vieh sorgfältig ausbalanciert werden, so dass eine wettbewerbsfähige Grasbedeckung erhalten bleibt, um die Rekrutierung von Bäumen einzugrenzen.EEA MercedesFil: Macias, Daniel. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Mercedes; ArgentinaFil: Mazía, Noemí. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal; ArgentinaFil: Jacobo, Elizabeth. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Animal; Argentin

Seed local adaptation and seedling plasticity account for Gleditsia triacanthos tree invasion across biomes

Background and Aims: Phenotypic plasticity and local adaption can contribute to the success of invasive species. While the former is an environmentally induced trait, the latter involves a selection process to filter the best genotype for a location. We examined the evidence for phenotypic plasticity and local adaptation for seed and seedling traits of the invasive tree Gleditsia triacanthos, with three origins distributed along an approx. 10° latitude gradient across three biomes. Methods: In sub-tropical forests, dry woodlands and secondary temperate grasslands in Argentina, we harvested seeds from clusters of neighbouring trees (i.e. families) distributed within 15-20 km in each origin (biome). We manipulated the environmental conditions relevant to each biome, assuming that propagule availability did not represent an ecological barrier. In growth chambers, we evaluated seed imbibition and seed germination under different light, temperature and water potential. In a 2 year common garden, we evaluated the impact of resident vegetation removal on seedling survival and growth. Key Results: Mean time to complete seed imbibition differed among origins; seeds from temperate grasslands reached full imbibition before seeds from dry woodlands and sub-tropical forests. Germination was always >70 %, but was differentially affected by water potential, and light quantity (dark-light) and quality (red-far red) among origins, suggesting local adaptation. In the common garden, vegetation removal rather than origin negatively affected seedling survival and enhanced seedling growth. Vegetation removal increased basal diameter, leaves per plant and spine number, and reduced the height:basal diameter ratio. Conclusions: We conclude that local adaptation in seed germination traits and plastic changes in seedling allometry (e.g. height:diameter) may allow this tree to respond over the short and long term to changes in environmental conditions, and to contribute to shape G. triacanthos as a successful woody invader. Overall, our study revealed how local adaptation and plasticity can explain different aspects of tree invasion capacity across biomes.Fil: Tognetti, Pedro Maximiliano. 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 Buenos Aires. Facultad de Agronomía. Departamento de Métodos Cuantitativos y Sistemas de Información; ArgentinaFil: Mazía, Cristina Noemí. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal; ArgentinaFil: Ibáñez, Gonzalo. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal; Argentin

Grass competition surpasses the effect of defoliation on a woody plant invader

Woody encroachment in grasslands represents a global phenomenon with strong consequences on ecosystem functioning. While the causes triggering this process can be multiple, there is consensus on the fact that anthropogenic activities play a central role in woody expansion. In particular, the loss of grass cover increases the chances of woody invasion, whereas the role of defoliation is less known. In this study our objective was to assess the simultaneous effect of competition generated by resident vegetation and woody seedling defoliation on the growth and survival of Gleditsia triacanthos seedlings, a woody invader in Argentina. We established a factorial pot experiment with two main factors: Gleditsia defoliation (2 levels: with and without defoliation) and pasture competition (3 levels: without pasture, clipped pasture and intact pasture). Our results showed that pasture competition reduced Gleditsia survival and tree growth, but that the effect of tree defoliation on tree growth depended on the magnitude of pasture competition. More widely, our results stress the existence of a hierarchy order of factors controlling Gleditsia establishment (survival + growth): grass competition was the main control and tree defoliation became important only in the absence of competition. This evidence suggests that maintaining a competitive grass cover along with a frequency of tree defoliation could diminish tree establishment in herbaceous communities.Fil: Aranda, Melina Jeanette. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Tognetti, Pedro Maximiliano. 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: Mazía, Cristina Noemí. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Are rodents a source of biotic resistance to tree invasion in Pampean grasslands? Tree seed consumption under different conditions

Biotic resistance has been invoked as a major barrier to woody species invasion, although the role of resident generalist consumers and their interaction with seed availability in a local community has received little attention.We assessed tree seed consumption by rodents under two different scenarios: (i) We documented in field spatio-temporal patterns of seed predation by native rodents on two exotic tree species, Gleditsia triacanthos or ‘honey locust’ and Robinia pseudoacacia or ‘white locust’ (family Leguminosae), in five grassland habitats of the Inland Pampa, Argentina. (ii) We conducted laboratory feeding trials to evaluate tree seed consumption in the presence (cafeteria-style feeding trials) and in the absence (non-choice feeding trials) of alternative food supplies. Seed predation was generally higher for Robinia than for Gleditsia seeds, both in field and laboratory conditions. For both tree species, seed predation varied between habitats and seasons and was higher in the native tussock grassland than in the remaining studied communities, whereas the crop field showed the lowest levels of consumption along with the absence of captured rodents. Seed consumption of Gleditsia and Robinia among the four grassland communities (which did not differ in rodent abundance) was negatively associated with the availability of alternative food. Laboratory feeding trials showed a higher consumption of Gleditsia seeds in the non-choice than in the cafeteria-style feeding trials, while the consumption of Robinia seeds did not differ in the absence or presence of alternative seeds. These patterns indicate that the contribution of resident granivores to invasion resistance might depend on colonizer species identity, recipient community type and season of the year. We suggest that rodent preferences for different invader seeds will interact with the availability of alternative food in the local habitat in influencing the amount of predator-mediated biotic resistance to invasion.Fil: Muschetto, Emiliano. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: Mazía, Cristina Noemí. Universidad de Buenos Aires. Facultad de Agronomia. Departamento de Producción Vegetal. Cátedra de Dasonomia; ArgentinaFil: Cueto, Gerardo Ruben. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: Busch, Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentin

Chronic insect herbivores accelerate litter decomposition and nutrient recycling rates along an environmental/herbivory gradient in northern Patagonia

Canopy insects are the main consumers in forests, and understanding their ecological role includes considering their effects on litter decomposition and nutrient cycling. We experimentally evaluated how litter decomposition is shaped by the decomposition environment and by litter traits shaped by forest moisture origin and chronic insect activity. We selected 4 forest stands at the driest and wettest extremes of beech (Nothofagus pumilio) forests in northwest Patagonia (mean annual rainfall 800 and 3000 mm yr−1 respectively). In two stands from each extreme, we performed three litterbag decomposition experiments. Experiment 1 included a reciprocal litter transplant between dry and wet stands, replicated in 2 different years for 24 and 12 months. Litterbags comprised the “Natural” proportion of undamaged and damaged leaves from the local insect community. Experiments 2 and 3 examined leaf insect damage effects on litter decomposition, respectively “in situ” and under controlled conditions. Here, we included three types of litterbags: 1- “Natural” (described above), 2- only insect-damaged litter, and 3- only healthy (undamaged) litter. Reciprocal transplants showed that litter decomposition was mostly controlled by litter origin and less by the decomposition environment (wet or dry forests). But, challenging predictions based on litter quality produced under water limiting environments, “Natural” litter chemical quality did not differ between forests. Even, when compared under the same decomposition environment (wet or dry forest), “Natural” litter from dry forests decomposed 31% faster and released 109% more N than “Natural” litter from wet forests. “Natural” litter from dry forests had a higher herbivory frequency and higher dominance of endophagous insects than wet stands. The high proportion of damaged litter in dry forests decreased “Natural” litter C:N ratio to match the chemical quality of “Natural” litter from wet forests. Experiment 2 showed that, in both wet and dry forests, damaged litter decomposed 31% faster than undamaged litter (in situ). Insect damage also reduced 90% N retention, but only in dry forests. Our results suggest that differences in insect communities living in contrasting environments could act as key drivers in shaping the recycling of organic matter, counteracting environmental differences between forests.Fil: Piazza, María Victoria. Universidad de Buenos Aires. Facultad de Agronomia. Departamento de Producción Vegetal. Cátedra de Dasonomia; Argentina. 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: Mazía, Cristina Noemí. Universidad de Buenos Aires. Facultad de Agronomia. Departamento de Producción Vegetal. Cátedra de Dasonomia; ArgentinaFil: Kitzberger, Thomas. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Laboratorio de Ecotono; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Chaneton, Enrique Jose. 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; Argentin

Nutrient supply and bird predation additively control insect herbivory and tree growth in two contrasting forests. Oikos

It has been suggested that bottom-up and top-down forces interactively control food web dynamics. While top-down effects would increase with resource availability to plants, bottom-up effects would be stronger under low predator abundance. These predictions, however, have rarely been tested at contrasting sites while keeping the dominant plant species unchanged. Furthermore, few studies have factorially manipulated both types of forces in forest communities. For two years, we evaluated the effects of fertiliser (NPK) addition and bird exclusion on tree growth, leaf traits, insect abundance, and folivory rates in a dry/warm and a wet/cold Nothofagus pumilio forest in Patagonia, Argentina. Overall, we found no interaction between nutrient supply and bird predation, although the strength of bottom-up and top-down forces differed markedly between forest sites. Treatment effects were generally weak in the wet forest, where tree growth rates and insect herbivory were low relative to the dry forest. In the dry forest, fertilisation increased sapling growth, insect abundance and folivory, whereas bird exclusion increased leaf damage and reduced tree growth. In the wet forest, fertilisation enhanced leaf nutrient contents and folivore abundance but not sapling growth, while bird exclusion had little impact on insects or trees. These results imply that factors other than nutrients and birds were important in controlling tree growth and folivore activity in the wet forest. While treatment effect sizes varied widely among feeding guilds, in general, nutrient effects on folivores were stronger than predator effects. We conclude that, within the time-frame of this study, tree growth and herbivory were additively affected by soil nutrients and predator presence, as bird exclusion effects did not change with elevated folivore activity on fertilised trees. We also show that both top-down and bottom-up cascades were weaker in a forest site characterised by slow-growing juvenile trees subjected to low folivore pressure. © 2009 The Authors.Fil: Garibaldi, Lucas Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Métodos Cuantitativos y Sistemas de Información; ArgentinaFil: Kitzberger, Thomas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Mazía, Cristina Noemí. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Agronomia. Departamento de Producción Vegetal. Cátedra de Dasonomia; ArgentinaFil: Chaneton, Enrique Jose. 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; Argentin

Seasonal patterns of herbivory, leaf traits and productivity consumption in dry and wet Patagonian forests

1. Endemic herbivory can influence forest ecosystem function, but how annual productivity consumption relates to seasonal resource utilisation by folivore guilds remains poorly understood. 2. Monthly changes in leaf damage and foliage traits were monitored in 'dry' and 'wet'Nothofagus pumilio (Fagales: Nothofagaceae) deciduous forests in northern Patagonia, Argentina. Herbivore-induced leaf abscission was assessed and foliar productivity consumption was measured in the canopy and in litterfall harvests. 3. Seasonal damage ranged from 8% to 32% in dry forest, but remained below 5% in wet forest although foliar quality was higher in the latter. In dry forest, dominant guilds were temporally separated; leaf miners consumed younger foliage in spring to early summer, whereas leaf tiers prevailed in late summer to autumn. In wet forest, damage created by external chewers was concentrated in early summer. 4. Insect damage induced premature leaf abscission, especially in dry forest. Although foliar production in wet forest doubled that in dry forest, the percentage of productivity lost to folivores was higher in dry (14-20%) than in wet (1.2-1.8%) forest. 5. The overall greater impact of herbivory in dry forest canopies countered the expectation that consumption would increase with plant productivity and nutritional quality. Lower temperatures and a shorter growing season are likely to constrain folivory in wet forest stands.Fil: Mazía, Cristina Noemí. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal; ArgentinaFil: Chaneton, Enrique Jose. 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: Dellacanonica, Cristina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal; ArgentinaFil: Dipaolo, Luciano. 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: Kitzberger, Thomas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentin