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Effects of biological legacies and herbivory on fuels and flammability traits: A long-term experimental study of alternative stable states
Ecological memory, often determined by the extent and type of retained biological legacies present following disturbance, may produce persistent landscape patterns. However, after fire, the persistence or switch to an alternative state may depend on the complex interplay of ecological memory (biological legacies) and potential effects of new external factors influencing the post-fire environment. The current study assesses both the strength of ecological memory resulting from biological legacies of pre-burn vegetation types as well as post-fire effects of livestock. Following a severe fire in 1999, we set up a network of long-term exclosures to examine the effects of legacies and cumulative herbivory by cattle on fuel types, amounts, distribution, flammability and microenvironmental conditions in two post-fire communities representing alternative fire-driven states: pyrophobic Nothofagus pumilio subalpine forests and pyrophytic Nothofagus antarctica tall shrublands in northwestern Patagonia, Argentina. Our results show that the retained post-disturbance legacies of tall shrublands and subalpine forests largely determine fuel and flammability traits of the post-fire plant communities 16 years after fire. The importance of biological legacies retained from the unburned plant communities was reflected by the substantially higher amounts of total fine fuel, greater vertical and horizontal fuel continuity and the higher temperatures reached during experimental tissue combustion at post-fire shrubland compared to post-fire forest sites. We show that herbivores may produce antagonistic effects on flammability by decreasing tissue ignitability, total fine fuel and litter depth, and disrupting the vertical and horizontal fine fuel continuity, therefore reducing the probability of fire propagation. However, cattle can increase ratios of dead to live fine fuels, reduce soil moisture, and inhibit tree height growth to canopy size, consequently impeding the development of a closed pyrophobic forest canopy. Synthesis. Our results support the hypothesis that biological legacies, most importantly the dominance by pyrophytic woody plants that resprout vigorously vs. the dominance by pyrophobic obligate seeders, favour fuel and flammability characteristics at the community level which reinforce the mechanisms maintaining pyrophytic shrublands vs. pyrophobic forests. Herbivory by introduced cattle can partially blur sharp pyrophobic/pyrophytic state boundaries by promoting the development of novel post-fire transitional states.Fil: Blackhall, Melisa. 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: Raffaele, Estela. 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: Paritsis, Juan. 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: Tiribelli, Florencia. 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: Morales, Juan Manuel. 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: 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: Gowda, Juan Janakiram Haridas. 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: Veblen, Thomas. University of Colorado; Estados Unido
Nematóides resistentes a alguns anti-helmínticos em rebanhos caprinos no Cariri Paraibano Nematode resistant to some anthelmintics in dairy goats in Cariri Paraibano, Brazil
Objetivou-se avaliar a resistência de nematódeos a alguns anti-helmínticos em rebanhos caprinos no Cariri Paraibano. Foram utilizados 144 animais no período seco e 120 animais no período chuvoso, fêmeas com idade acima de oito meses de vida e lactantes, distribuídos em 4 grupos: Grupo I não tratado, Grupo II tratado com albendazole a 10%, Grupo III tratado com ivermectina a 1% e Grupo IV tratado com fosfato de levamisole a 18,8%, nas doses recomendadas pelos fabricantes. Para avaliar a resistência, aplicou-se o teste de redução na contagem de ovos por grama de fezes (RCOF) e o cultivo de larvas de helmintos. As amostras fecais foram coletadas no dia do tratamento (dia base) e 7, 14 e 21 dias após o tratamento. No grupo tratado com Albendazole, observaram-se eficácias de 61%, 11% e 24% no período seco e de 55%, 14% e 12% no período chuvoso, aos 7, 14, e 21 dias, respectivamente. No grupo tratado com Ivermectina, a eficácia foi de 14%, 70% e 66% para o período seco, e de 76%, 34% e 71% para o período chuvoso, aos 7, 14 e 21 dias, respectivamente. O grupo tratado com fosfato de Levamisole apresentou percentuais de eficácia de 89%, 79% e 73% no período seco e de 76%, 69% e 67% no período chuvoso, aos 7, 14 e 21 dias, respectivamente. Os resultados obtidos indicam que os nematódeos gastrintestinais de alguns rebanhos caprinos no Cariri Paraibano não são sensíveis aos princípios ativos Albendazole, Levamisole e Ivermectina. Durante o período de estudo foi identificada a presença de parasitas dos gêneros Haemonchus, Trichostrongylus, Oesophagostomum e Strongyloides.<br>The aim of this paper was to evaluate the resistance of nematodes to some anthelmintics in dairy goats in Cariri Paraibano, Brazil. A total of 144 female goats, over 8 months of age, were used in the dry season and 120 ones during the rainy season, divided into four groups: Group I untreated, Group II treated with albendazole 10%, Group III treated with ivermectin 1%, and Group IV treated with levamisole phosphate 18.8%, at doses recommended by the manufacturer. To evaluate the resistance, the reduction in egg count per gram of feces and the cultivation of larval helminths. The fecal samples were collected on the day of treatment and, after 7, 14 and 21 days of treatment. In the group treated with albendazole, 61%, 11% and 24% of efficiency was observed in the dry period, and 55%, 14% and 12% in the rainy season, at 7, 14, and 21 days respectively. In the group treated with ivermectin, efficacy was 14%, 70% and 66% for the dry period, and 76%, 34% and 71% for the rainy season, at 7, 14 and 21 days respectively. The group treated with phosphate Levamisole showed efficacy rates of 89%, 79% and 73% in the dry period, and 76%, 69% and 67% in the rainy season, at 7, 14 and 21 days. The results indicate that the gastrointestinal nematodes of some dairy goats in Cariri Paraibano are not sensitive to the active Albendazole, Levamisole and Ivermectin. During the study, presence of specimens of the genera Haemonchus, Trichostrongylus, Oesophagostomum and Strongyloides was identified