Human‐Driven Fire Regime Change in the Seasonal Tropical Forests of Central Vietnam

• Published in: Geophysical research letters Vol. 50; no. 13
• Main Authors: Nguyen, Thiet V., Allen, Kathryn J., Le, Nam C., Truong, Cuong Q., Tenzin, Karma, Baker, Patrick J.
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 16.07.2023; Wiley
• Subjects: Central Highlands; Chronology; Climate; Climatic conditions; Climatic indexes; Conifers; Drought; Drought index; Dry season; fire regime; Fires; Forests; Highlands; Human influences; Landscape; National parks; Rainy season; Reconstruction; Tree rings; Trees; tree‐ring; Tropical forests; Vietnam; Wet season; Vietnam
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2022GL100687

To better understand fire regimes and their relation to climate in the seasonal tropical forests of continental Southeast Asia, we developed the first multi‐century tree‐ring based fire history chronology for the region. The chronology included 776 fire scars collected at Bidoup NuiBa National Park (BNNP) in the Central Highlands of Vietnam and spans the period 1636–2020. Fires were recorded in 116 years, representing 47% of the years covered by the 249‐year period between the first fire scar (1772) and the last (2020). While only 9% of years within the sampled BNNP forests experienced fires before 1905, 70% recorded fires between 1906 and 1963 and 90% showed evidence of fire after 1963. Fire occurrence was highly correlated with climate indices (wet season Nino 3.4 and dry season regional Palmer Drought Severity Index) during the period 1906–1963, but showed no significant correlation after 1963. Our fire reconstruction from BNNP suggests that the fire regime has shifted from one driven primarily by climate to one in which human activities dominate the occurrence of fire within these seasonal tropical landscapes. Plain Language Summary In many parts of the world fires shape forest structure, composition, and dynamics. While fire regimes and their long‐term impacts on forests have been described for many temperate forests, we know little about the impact of fire in tropical forests. We used tree rings from two tropical conifers (Pinus kesiya and Keteleeria evelyniana) to develop the first multi‐century fire chronology from continental southeast Asia. We used it to reconstruct over 200 years of fire activity in the Central Highlands of Vietnam. We found that fire occurrence in the region was associated with climatic conditions prior to 1963. However, since then an increase in human settlement and activities within these landscapes has led to a massive increase in fire frequency and extent. Our tree‐ring based fire‐history reconstruction shows that the overwhelming pressure of human ignitions have effectively eliminated climate as a factor limiting fires in these landscapes. Key Points First annually resolved, multi‐century fire history reconstruction from monsoon Asia Seasonal and interannual drought conditions have historically been an important driver of fire activity in the region In the 1960s the fire regime shifted from patchy to landscape‐scale occurrence, which was associated with a sudden increase in the regional human population