A importância de filtros bióticos e abióticos para o sucesso de gramíneas exóticas no cerrado
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Data
2023-01-12
Autores
Leite, Matheus Roberto
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Universidade Estadual Paulista (Unesp)
Resumo
O Cerrado contém as savanas mais ricas em biodiversidade do planeta, entretanto, as mesmas vêm sendo ameaçadas por gramíneas exóticas. Diante disso, foi realizada uma revisão de literatura narrativa, investigando a influência de filtros abióticos (perturbação, eventos de fogo, disponibilidade nutricional e disponibilidade hídrica) e bióticos (germinação, facilitação e comunidade microbiana) no sucesso das gramíneas invasoras Urochloa decumbens (Capim Braquiária) e Melinis minutiflora (Capim Gordura) e das gramíneas naturalizadas Hyparrhenia rufa (Capim Jaraguá) e Andropogon gayanus (Capim Gamba). Dentre os filtros abióticos, a perturbação tem sido associada à ação antrópica e/ou ocorrência de eventos de fogo, existindo evidências de que áreas perturbadas estão mais suscetíveis à invasão, especialmente por M. minutiflora. Por outro lado, a ocorrência de eventos de fogo pode beneficiar fortemente as gramíneas exóticas U. decumbens, M. minutiflora, H. rufa e A. gayanus, as quais apresentam diferentes estratégias para lidar com a adversidade, como a capacidade de rebrota e resistência do banco de sementes. Tendo em vista que baixa disponibilidade de recursos (água e nutrientes) pode ser um fator limitante às gramíneas exóticas, há evidências de que M. minutiflora e A. gayanus recorram ao uso econômico de recursos e modificações na ciclagem de nutrientes, favorecendo a sua absorção. Em relação aos filtros bióticos, é relatado que enquanto espécies nativas possuem elevada produção de sementes inviáveis, as gramíneas exóticas M. minutiflora, U. decumbens, H. rufa e A. gayanus apresentam elevadas taxas de germinação e produção de sementes viáveis. Tais espécies também podem se beneficiar de associações com outras plantas ou microrganismos, havendo evidências que U. decumbens e Melinis minutiflora apresentam relações com fungos micorrízicos, rizobactérias e plantas leguminosas que se associam com bactérias diazotróficas. Este estudo reforça que embora as gramíneas naturalizadas H. rufa e A. gayanus não sejam motivo atual de preocupação, o fato destas apresentarem estratégias semelhantes às gramíneas invasoras pode sinalizar futura tendência à invasão.
The Cerrado contains the richest savannas on the planet, however, such diversity is being threatened by exotic grasses. Therefore, a literature review was carried out, investigating the influence of abiotic (disturbance, fire events, nutrient availability and water availability) and biotic (germination, facilitation and microbial community) filters on the success of invasive grasses Urochloa decumbens (Signal Grass) and Melinis minutiflora (Molasses Grass) and the naturalized grasses Hyparrhenia rufa (Giant Thatching Grass) and Andropogon gayanus (Gamba Grass). Among the abiotic filters, disturbance has been associated with anthropic action and/or occurrence of fire events, and there is evidence that disturbed areas are more susceptible to invasion, especially by M. minutiflora. On the other hand, the occurrence of fire events can strongly benefit the exotic grasses U. decumbens, M. minutiflora, H. rufa and A. gayanus, which have different strategies to deal with adversity, such as the capacity for regrowth and resistance of the seed bank. Considering that the low availability of resources (water and nutrients) can be a limiting factor for exotic grasses, there is evidence that M. minutiflora and A. gayanus resort to the economical use of resources and modifications in the cycling of nutrients, favoring their absorption. Regarding biotic filters, it is reported that while native species have a high production of unviable seeds, the exotic grasses M. minutiflora, U. decumbens, H. rufa and A. gayanus have high rates of germination and production of viable seeds. Such species can also benefit from associations with other plants or microorganisms, with evidence that U. decumbens and M. minutiflora have relationships with mycorrhizal fungi, rhizobacteria and nitrogen-fixing plants. This study reinforces that although the naturalized grasses H. rufa and A. gayanus are not a current cause for concern, the fact that they present strategies similar to invasive grasses may signal a future trend towards invasion.
The Cerrado contains the richest savannas on the planet, however, such diversity is being threatened by exotic grasses. Therefore, a literature review was carried out, investigating the influence of abiotic (disturbance, fire events, nutrient availability and water availability) and biotic (germination, facilitation and microbial community) filters on the success of invasive grasses Urochloa decumbens (Signal Grass) and Melinis minutiflora (Molasses Grass) and the naturalized grasses Hyparrhenia rufa (Giant Thatching Grass) and Andropogon gayanus (Gamba Grass). Among the abiotic filters, disturbance has been associated with anthropic action and/or occurrence of fire events, and there is evidence that disturbed areas are more susceptible to invasion, especially by M. minutiflora. On the other hand, the occurrence of fire events can strongly benefit the exotic grasses U. decumbens, M. minutiflora, H. rufa and A. gayanus, which have different strategies to deal with adversity, such as the capacity for regrowth and resistance of the seed bank. Considering that the low availability of resources (water and nutrients) can be a limiting factor for exotic grasses, there is evidence that M. minutiflora and A. gayanus resort to the economical use of resources and modifications in the cycling of nutrients, favoring their absorption. Regarding biotic filters, it is reported that while native species have a high production of unviable seeds, the exotic grasses M. minutiflora, U. decumbens, H. rufa and A. gayanus have high rates of germination and production of viable seeds. Such species can also benefit from associations with other plants or microorganisms, with evidence that U. decumbens and M. minutiflora have relationships with mycorrhizal fungi, rhizobacteria and nitrogen-fixing plants. This study reinforces that although the naturalized grasses H. rufa and A. gayanus are not a current cause for concern, the fact that they present strategies similar to invasive grasses may signal a future trend towards invasion.
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Andropogon gayanus, Hyparrhenia rufa, Melinis minutiflora, Urochloa decumbens, Invasões biológicas, Biological invasions