Abstract
Forest fires are known to significantly alter soil nutrient availability. The study investigated the post-fire nutrient availability in the sub-tropical forest ecosystem of Koubru Hills, Manipur (North-East India). The forested ecosystem was disturbed by forest wildfire in January 2010.To study the fire effect, collection of burned and unburned soil samples from three soil depths (0-5, 5-10 and 10-15 cm) was started approximately three months after the fire event and continued at monthly intervals for a period of one year. The collected soil samples were analyzed for soil organic carbon (SOC), NH4+-N, Bray-extractable phosphorus, available potassium and micronutrients such as Fe, Cu, Mn and Zn. Results of the ANOVA test showed significant reduction in the SOC, NH4+-N and available K contents of the surface (0-5 cm) and sub-surface (5–10 and 10-15 cm) soil layers of the burned area. However, significant increases in the Bray-extractable phosphorus were observed in all the three soil depths studied. With respect to the effect of forest fire on soil micronutrient availability, results are contradictory. The available Fe depleted in all the three soil depths, whilst the available Cu declined in the 0-5 cm but increased in the 10-15 cm soil layer. The available Cu content of the 5-10 cm soil layer did not vary between the burned and unburned areas. While no significant effect of fire was observed on the available Mn contents of the 0-5 and 10-15 cm soil layers, there was a significant post-fire decrease in the Mn availability of the 5-10 cm soil layer of the burned area compared with the unburned area. Forest fire also resulted in a significant loss of the available Zn from the 0-5 and 5-10 cm soil layers of the burned area but in the 10-15 cm soil layer, no significant variation was observed between the burned and unburned areas.
Highlights
Forest fires form part of ecosystem disturbances and those provoked by human activities are a paramount environmental problem and a serious threat to biodiversity[1]
The persistence of this condition throughout the study reflects the high severity of the forest fire and the fact that we found a significant decrease of soil organic carbon (SOC) in the [5,6,7,8,9,10] and [10,11,12,13,14,15] cm soil layers is further evidence of the high severity of the forest fire
The forest wildfire had a significant effect on the available macronutrient concentrations, decreasing NH4+–N and available K and increasing that of available P in all the three soil layers
Summary
Forest fires form part of ecosystem disturbances and those provoked by human activities are a paramount environmental problem and a serious threat to biodiversity[1]. Fire as natural or anthropogenic disturbance can cause short- or long-term changes in ecosystem dynamics[3,4]. Fire effects on soil can vary greatly among different ecosystems depending on the severity (a combination of fire line intensity and duration) according to Keeley[6] and frequency of fires. While low severity-fires do not substantially affect soils, high severity-fires can affect a wide range of soil properties, one of which is nutrient availability[7]. The concentrations, forms, and depth distribution of soil nutrients can be dramatically altered after fire disturbance[8]. Post-fire nutrient losses can be accelerated through volatilization, leaching and erosion[7]
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