Fuel beds variation of coastal tropical freshwater forested wetlands in three disturbance regimes at La Encrucijada, Biosphere Reserve, Mexico

Abstract

Background: Tropical freshwater forested wetlands in coastal regions are rapidly disappearing, one of the causes is forest fires. This is caused by high accumulation of fuel beds that can vary in origin and type. Therefore, the objective of this study was to characterize the fuel beds in tropical freshwater forested wetlands with three different level of disturbance at El Castaño, La Encrucijada Biosphere Reserve.Methods: Seventeen sampling units were used to described the strates of forest fuel beds (canopy, sub-canopy and understory) in both the vertical and horizontal stratum. Quantity and quality of dead (fallen woody material, surface litterfall and fermented litterfall) fuels were characterized using the planars intersections technique.Results: A total of eight tree species, two shrubs, five lianas and two herbaceous species were found in tropical freshwater forested wetlands. The vertical structure concentrates the highest proportion of trees between 2 and 12 m high, including the first two defined height classes. The horizontal structure denotes a higher percentage of trees with a normal diameter between 2.5 to 7.5 cm (61.4%) of the total. The sites none disturbance presented the highest arboreal density (2,686 ind. ha− 1), however the highest basal area was found in the sites with medium disturbance (39.41 m2 ha− 1). The richness and diversity of species shows that the Fisher, Margalef, Shannon and Simpson α indices were higher in the sites undisturbed, while the Berger-Parker index shows greater dominance in the sites high disturbance. Pachira aquatica Aubl. was the species with the highest importance value index, and contributes the most to the fuel beds. The average accumulation of dead fuel beds was higher in sites with high disturbance (222.18 ± 33.62 t ha− 1), with the largest accumulations of woody fuels occurring in the 1 h, 10 h and 1000 h classes, the latter in a state of fermentation.Conclusions: It’s important to consider the probability of occurrence of surface fires is high. In these tropical freshwater forested wetlands, independent of disturbance, underground fires have the same probability and the intensity will depend on the depth of the organic matter layer. This study contributes define fire-prone areas in these ecosystems. The results are of great importance to design fire prevention strategies.

A screening system to predict wildfire risk of invasive plants

“…Pachira aquatica was first identified as naturalizing on O'ahu in 2011 (Evenhuis and Eldredge 2013). This species is recognized as producing a flammable litter which can promote fires during the dry season in mangrove forests in Mexico (Caldero ´n et al 2020). In Hawai 0 i it has been naturalized in lowland rainforest, where its litter is unlikely to burn, and the plant has low dispersal ability, producing few, very large seeds.…”