Fire can weaken or trigger functional responses of trees to flooding in wetland forest patches

Abstract

Question:Fire and flood act as ecological filters on vegetation, either separately or combined, and cause morphological and physiological changes. Hence, they influence the composition and structure of plant communities. Since evidence strongly suggests that they are important filters operating in the system, we asked if fire, flood intensity, and their interaction could be related to variation in the functional traits of studied trees.Study Site: Pantanal, Mato Grosso do Sul, Brazil. Methods:We sampled 14 individuals (totaling 280) of the 20 most representative trees in 24 forest patches along the flooding gradient and measured functional traits related to allocation of resources and protection in response to these filters. We also assessed leaf and soil nitrogen, phosphorus, and potassium levels.Results: Along the flooding gradient, the studied tree species showed a tendency toward decreasing specific leaf area (SLA), as well as leaf nitrogen concentrations, whereas leaf thickness and leaf dry matter content (LDMC) increased. In burned areas, LDMC and leaf nitrogen exhibited the opposite tendency and decreased along the flooding gradient. Leaf thickness (LT) showed less increase in burned areas, while SLA had less decrease. Relative Bark Thickness (RBT) increased along the flooding gradient only after fire. Soil nitrogen decreased along the flooding gradient without an effect of fire. Conclusions:Since LDMC is a proxy of flammability, the probability of burning decreases after each fire event, while the most flooded environments become less fireprone. In burned environments, the differences in the allocation of resources (SLA and LT) diminish along the flooding gradient, indicating that leaf behavior is almost the same post-fire. RBT increases with increased flooding only after a fire, contributing to oxygen exchange during floods to protect the bark against fire. The interaction between fire and flood causes tree species to invest in structures for protection and resistance to fire, as well as retain nutrients. K E Y W O R D S ecological filters, environmental factors, floodplain, functional diversity, Pantanal 522 |

Environmental drivers of three neighbouring monodominant stands in Pantanal wetland

“…a wet summer season and dry winter (Kottek et al, 2006). The average yearly rainfall is 1,070 mm (Soriano, 1997). The seasonal flooding regime of the Pantanal is mainly caused by the Paraguay River and its numerous tributaries, and some zones can even be flooded up to 200 days per year (Damasceno Junior et al, 2005).…”

“…Frequent vegetation types are the monodominant stands, riparian forests of the Miranda River, seasonally flooded grasslands and small islands of forest patches locally called capões (Allem & Valls, 1987;Damasceno Júnior et al, 1999). Fire events can also occur in this region in all types of vegetation at intervals that can vary from 2 to 10 years (Souza et al, 2019;Manrique-Pineda et al, 2021).…”

Avaliação de efeitos ambientais cumulativos na Bacia do Alto Paraguai: uma abordagem estratégica

“…Viganó et al, (2018b) avaliaram os focos de incêndio mensais que ocorriam na região de Corumbá entre os anos de 2005 a 2015, e os autores identificaram um aumento significativo a partir de julho, agosto e setembro respectivamente, apresentando um desvio padrão com coeficiente de variação alto, indicando uma grande heterogeneidade dos dados, devido ao fato de que no segundo semestre é considerado uma estação seca, e assim, há o aumento considerável dos focos de incêndio.Entretanto, é sabido que o fogo pode atuar como filtro ecológico que possibilita moldar as estruturas das comunidades vegetais, especialmente em sua regeneração, sendo que o processo de queima pode estar associado às condições meteorológicas e de inflamabilidade da vegetação(SOUZA et al, 2019). Contudo, ainda há poucas informações sobre os efeitos e implicações em algumas vegetações, como exemplo as e as atividades de uso da terra podem acabar potencializando o período de seca e os incêndios frequentes(MORISETTE et al, 2005;SERRÃO;LIMA, 2014).De acordo com os dados do Instituto Nacional de Pesquisa Espaciais (INPE) no ano de 2020 houve um aumento nos focos de incêndio no Pantanal, representados por 82% 11 em comparação aos anos anteriores, já com o Cerrado também houve um aumento nos focos de queimadas se comparado ao ano de 2017, apresentando 130% 12 .…”