Assessment of Wildfire-Induced Changes in Energy Fluxes and Environmental Variables: A Case Study in the Similipal Forest Reserve, Odisha, India
Authors: Sunder MS Shyam , Tyagi Bhishma 
Published: March 2024

Wildfires, as extreme heat events, significantly impact environmental fluxes and vegetation. The present study investigates the impact of human-induced pressures on vegetation density, particularly in open forests vulnerable to deforestation, emphasizes the importance of preserving and managing forest resources. This study analyses the net effects of fire-induced changes in vegetation on incoming solar radiation (I), sensible heat flux (SH), latent heat flux (LH), Gross Primary Productivity (GPP), Global Precipitation Measurement (GPM), Evapotranspiration (ET), Land Surface Temperature (LST), Vapor Pressure Deficit (VPD), Soil Moisture (SM) and Aerosol Optical Depth (AOD). The examination spans the phases before, during, and after forest fires, offering comprehensive insights into long-term mean values and dynamic ecosystem responses. The forest fire events of 2004, 2005, 2006, 2009, 2013, 2016, 2018, 2021 have been considered based on their severity and significant number of fire episodes over the Simlipal forest reserve, Odisha, India. During the forest fires, we observed that I ranged from 34.366 Wm-2 to 36.411 Wm-2 before the fire, spiked to 37.729 Wm-2 during the fire and slightly decreased post-fire. SH peaked at 75.964 Wm-2 during the fire, indicating intense heat transfer. LH initially reduced during the fire, reaching a minimum of 49.069 Wm-2, followed by a significant post-fire increase, suggesting improved moisture transfer and a concurrent increasing trend in GPM (rainfall). GPP and ET declined during the fire but significantly increased post-fire, indicating recovery and enhanced vegetation productivity. LST rose notably during the fire, influenced by VPD, which decreased and increased post-fire. Soil Moisture SM gradually reduced throughout the study, reflecting environmental changes. AOD increased during the fire, negatively impacting GPP by limiting photosynthetic activity. Post-fire, GPP and SM increased with reduced AOD, supporting ecosystem recovery. GPM exhibited a post-fire increase, reaching the highest value of ~0.23 mm/day. Spatial analysis of AOD, SH, LH, VPD, ET, LST, and GPP revealed similar significant findings over the 2021 fire events. AOD exhibited higher variation in the southern and eastern regions before the forest fire, however, during the fire, AOD increased, particularly in the east part. SH and LH demonstrated inverse spatial distribution patterns during the fire, with SH increasing notably in the southern region and LH exhibiting reduced variability. VPD experienced slight changes, ranging from ~0.47 to 0.50 hPa. ET rates increased before and during the fire but decreased after the fire due to vegetation destruction. LST variation increased in burnt areas, and GPP showed decreased variability post-fire. The observed changes highlighted the resilience of the ecosystem and its adaptive responses to disturbances, providing valuable insights for sustainable land management strategies.
Keywords: Forest Fires; Forest Reserve; Heat Flux; Energy Balance; AOD