Post-fire consequences for leaf breakdown in a tropical stream

Renan De Souza Rezende,José Francisco Gonçalves-Júnior,Natália Guedes,Ricardo Keichi Umetsu,Cristiano Queiroz De Albuquerque,Andrezza Sayuri Victoriano Hirota,Paulino Bambi,Paulo Fernandes Roges Souza Silva,Cássia Alves Lima-Rezende,Helena Soares Ramos Cabette

doi:10.1590/s2179-975x4118

Abstract

Abstract Aim Wildfire is a natural pulsed disturbance in landscapes of the Savannah Biome. This study evaluates short-term post-fire effects on leaf litter breakdown, the invertebrate community and fungal biomass of litter from three different vegetal species in a tropical stream. Methods Senescent leaves of Inga laurina, Protium spruceanum and Rircheria grandis (2 ± 0.1 g dry mass) were individually placed in litter bags (30 × 30 cm: 10 mm coarse mesh and 0.5 mm fine mesh) and submerged in the study stream before and after fire. Replicate bags (n = 4; individually for each species, sampling time, fire event and mesh size) were then retrieved after 20 and 40 days and washed to separate the invertebrates before fire event and again immediately after fire. Disks were cut from leaves to determine ash-free dry mass, while the remaining material was oven-dried to determine dry mass. Results The pre-fire mean decomposition coefficient (k = -0.012 day-1) was intermediate compared to that reported for other savannah streams, but post-fire it was lower (k = -0.007 day-1), due to decreased allochthonous litter input and increased autochthones production. Intermediate k values for all qualities of litter post-fire may indicate that fire is equalizing litter quality in the stream ecosystem. The abundance of scrapers was found to be more important than fungal biomass or shredder abundance, probably due to their functioning in leaf fragmentation while consuming periphyton growing on leaf litter. Conclusions Theses results indicate that fire can modify the relationships within decomposer communities in tropical stream ecosystems.

Highlights

Wildfire is a natural pulsed disturbance in landscapes of the Cerrado (Neotropical savannah) biome in Brazil (Ribeiro, 2008); a warming climate can increase the frequency and intensity of wildfire disturbance (Rodríguez-lozano et al, 2015; Silverio et al, 2013)
This study evaluates short-term post-fire effects on leaf litter breakdown, the invertebrate community and fungal biomass of litter from three different vegetal species in a tropical stream
The remaining mass after fire in coarse mesh is higher in I. laurina (83.9%), followed to P. spruceanum (77.6%) and R. grandis (71.2%)

Summary

Introduction

Wildfire is a natural pulsed disturbance in landscapes of the Cerrado (Neotropical savannah) biome in Brazil (Ribeiro, 2008); a warming climate can increase the frequency and intensity of wildfire disturbance (Rodríguez-lozano et al, 2015; Silverio et al, 2013). Some of the effects that fire has on freshwater ecosystems (e.g. increased rate of nutrient cycling and changes to the trophic chain and physical and chemical properties of the water) may be similar to those from anthropic land use, such as agricultural and silviculture (for more see Bixby et al, 2015). Wildfire changes water quality with consequences for aquatic communities and ecosystem processes (Pettit & Naiman, 2007; White-Monsant et al, 2017). The effects of fire may be driven by resilient successional trajectories for watershed recovery (Bixby et al, 2015; White-Monsant et al, 2017), with changes to OM dynamics (e.g. leaf litter breakdown) in riparian zones during this process (Rodríguez-Lozano et al, 2015)

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