The effect of prescribed fires in abiotic and biotic factors in the southern region of Puerto Rico

Authors: TIRADO-CORBALA, REBECCA - University Of Puerto Rico; FLORES-MANGUAL, MARIO - University Of Puerto Rico; Rana Dangi, Sadikshya

Submitted to: Journal of Agriculture of the University of Puerto Rico
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/5/2023
Publication Date: 10/1/2022
Citation: Tirado-Corbala, R., Flores-Mangual, M.L., Rana Dangi, S. 2022. The effect of prescribed fires in abiotic and biotic factors in the southern region of Puerto Rico. Journal of Agriculture of the University of Puerto Rico. 106(2):183-205.

Interpretive Summary: The effects of field fires on soil microbial communities and nutrient cycling are poorly understood in the Southern Region of Puerto Rico. Prescribed fires were performed to mimic the effects of a field fire. The treatments included positive control (burned without remediation), negative control (non-burned sites), muching (burned and covered with mulch after burning) and surfactant (burned and covered with surfactant after burning). Soil samples were collected before and after burning. Study showed that most soil chemical properties were not affected by prescribed fire. Further, an increase in calcium and decrease in potassium concentrations were observed on burned plots with or without treatments compared to unburned soils. Soil microbial biomass was temporarily reduced by prescribed fire. However, after around 90 days, total microbial biomass was higher in mulch and surfactant treated burned soil compared to unburned and burned plots without treatments. The use of mulch and surfactant may have helped recover microbial communities after burning. This short-term study suggests that soil microbial communities are highly resilient to disturbance after fire.

Technical Abstract: Field fires can modify and affect soil nutrient cycling as well as alter the soil microbial communities (SMC), although the latter is not well understood. In the Southern Region of Puerto Rico, field fires have become a great problem primarily during the dry season. In this study, we performed prescribed fires to mimic the effects of a field fire in a hillside area at the Juana Díaz Agricultural Experiment Stations in October 2015 and March 2017. A complete randomized block design including the following treatments: negative control (unburned), positive control (burned plots, no remediation), mulching treatment (burned plots remediated with Leucaena spp. mulch), and surfactant treatment (burned plots remediated with a surfactant) was established in a Typic Calciustolls. In 2015 (first burning) soil samples were collected before burning and 30, 180, and 420 days after burning (DAB). In the second burning (2017) samples were collected 30, 90, and 270 DAB. Soil physicochemical properties and microbial community structure via phospholipid fatty acid (PLFA) analysis were assessed. Results showed that after two prescribed fires exchangeable cations were impacted, showing increasing and decreasing concentrations of calcium (Ca) and potassium (K), respectively when compared to unburned soils. Total fungal PLFA was significantly lower in burned plots with or without mulch and surfactant treatments compared to unburned plots, and total bacterial PLFA did not differ between burned and unburned plots after 30 days. Total microbial biomass was significantly (P < 0.05) higher in mulch and surfactant treated burned soil compared to unburned and burned plots without treatment after 90 (2017) and 420 (2015) DAB, respectively. The use of mulch and surfactant treatments on prescribed burning fields increased microbial communities after around 90 days. This study emphasizes short-term changes in microbial communities and suggests that they are highly resilient to disturbance after prescribed fire.