Fire history along environmental gradients in the subtropical pine forests of the Cordillera Central, Dominican Republic

Abstract

Fire history was reconstructed from fire-scarred individuals of the endemic pine (Pinus occidentalis) along climatic gradients in the Cordillera Central, Dominican Republic. We analysed variation in fire frequency by climate, elevation and aspect (windward and leeward of the central massif). A high correspondence between known fires and fire-scar chronologies indicates that the primary rings of this species are annual. Evidence was found for 41 fire years since 1727 A.D.; 28 were landscape-scale fires, nine of which were exceptionally large and linked to El Niño-triggered droughts. Mean fire return interval (FRI; the mean of individual samples) and mean fire interval (MFI; the composite mean of a group of samples) were used to estimate the upper and lower range in fire frequency. Mean FRI of the entire study area was 31.5 y (±24.9 y SD) and MFI for landscape-scale fires was 5.6 y (±4.1 y SD). The fire regime varied significantly with elevation and aspect. Mean FRI was 42.1 y (±27.6 y SD) and MFI was 9.8 y (±16.7 y SD) on moister windward zones, and mean FRI was 16.7 y (±7.8 y SD) and MFI 4.2 y (±1.9 y SD) in drier leeward zones. On windward slopes, high-elevation mean FRI (26.4 y) was significantly shorter than at middle (44.5 y) and low elevations (58.4 y). On leeward slopes, mean FRI did not vary significantly with elevation. The strong windward elevational patterning of the fire regime is driven by the trade wind inversion which traps moist air below 2000–2300 m. Such elevational patterns may be characteristic of montane fire regimes throughout the tropical trade wind belt.