Tropical montane vegetation dynamics near the upper cloud belt strongly associated with a shifting ITCZ and fire

Abstract

Summary1. Tropical montane forests house unusual and diverse biota and are considered highly vulnerable to climate change, particularly near the trade wind inversion (TWI) -the upper end of the cloud belt that defines tropical montane cloud forest (TMCF). The upper cloud belt has two possible futures: one hypothesis postulates a 'lifting cloud base', raising both the upper and lower ends of the cloud belt; the other expects the upper end of the cloud belt will change independently, with a 'shifting TWI'. 2. We used a~5900-year-long palaeorecord of vegetation and fire from a small forest hollow at 2455 m in the Cordillera Central, Dominican Republic. The site sits near the upper limit of TMCF taxa and the TWI and allows us to evaluate the relationship between vegetation dynamics and two potential drivers of TWI elevation -the Intertropical Convergence Zone (ITCZ) and the El Niño/ Southern Oscillation (ENSO). 3. Vegetation changed from cloud forest (~5900-5500 cal. years BP) to alpine grassland (~4300-1300 cal. years BP), to pine savanna (~1300-600 cal. years BP) and finally to closed pine forest (after~600 cal. years BP). Habitat distribution models for TMCF and pine forest taxa show that these state changes were strongly associated with position of the ITCZ (cloud forest xR 2 = 0.63; pine forest xR 2 = 0.53), providing support for the shifting TWI hypothesis.4. We find a negative relationship between fire and TMCF and a hump-shaped relationship between fire activity and pine. 5. Synthesis. Shifts up-and downslope of the upper limit of the cloud belt over the last 5900 years produced major vegetation changes. Fire also played a significant role, in particular when pine occupied the site after~1300 years ago and from 1965 AD when fire suppression led to a rapid return of cloud forest taxa. Our results strongly suggest that latitudinal shifts in the ITCZ position have controlled the upper limit of cloud forest in the Caribbean and understanding how the ITCZ will respond to climate change will be critical for tropical montane conservation strategies.

Columbus’ environmental impact in the New World: Land use change in the Yaque River valley, Dominican Republic

“…On Hispaniola, vegetation studies are most abundant for the area of the Dominican Republic ( Cano et al, 2014 ; Cano-Carmona, 2010 ; Cano-Ortiz et al, 2015 ; Durland, 1922 ; Hager and Zanoni, 1993 ; Harcourt et al, 1996 ; Liogier, 1981 ; Marcus, 2008; Martin et al, 2007 ). The natural vegetation consists of (a) dry forest ( Cano-Ortiz et al (2015) and references therein; Garcia-Fuentes, 2015), (b) mesic forest, (c) wet forest (including high elevation ‘cloud forest’ at locations where ascending air masses cause local condensation zones ( Crausbay et al, 2015 ), and low elevation ‘gallery forest’ which is periodically flooded in the study area by the Yaque River), (d) pine forest of Pinus occidentalis (endemic to Hispaniola) found from 200 to 3100 m elevation in the Cordillera Central ( Darrow and Zanoni, 1990 ; Farjon and Styles, 1997 ), (e) shrubland, and (f) herbaceous vegetation types ( Holdridge, 1945 ; Marcus et al, 2008 ). In the Ciboa Valley, only remnants of degraded natural vegetation can be found.…”

Natural disturbance, vegetation patterns and ecological dynamics in tropical montane forests

“…Recent palaeoecological studies have also demonstrated the historic importance of fire in TMFs, finding correlations in climatic fluctuations, fire occurrence and human land use over millennial time-scales (Bush et al . 2005, Conserva & Byrne 2002, Crausbay et al 2014a, 2015; Dull 2004, Hope 2009, Islebe & Hooghiemstra 1997, Urrego et al 2011). Until recently however, fire was generally considered rare in TMFs (Asbjornsen & Wickel 2009), in part because of the prominence of the fire-resistant cloud zone in the study of TMFs, but natural fires can be quite common in some parts of tropical montane landscapes (Ashton 2003, Martin & Fahey 2006, Martin et al .…”

“…In contrast, the roles of disturbance and vegetation dynamics have received little attention in TMFs, despite the importance of these topics in understanding the spatial patterns of plant communities in other biomes and numerous palaeoecological studies distributed across the tropics that detail the pervasiveness of change and disturbance in TMF landscapes (Bush et al . 2005, Conserva & Byrne 2002, Crausbay et al 2014a, 2015; Dull 2004, Hope 2009, Islebe & Hooghiemstra 1997, Urrego et al 2011). To date, four books have provided the main synthesis and conceptual framework of TMF ecology (Bruijnzeel et al 2011, Churchill et al 1995, Hamilton et al 1995, Stadtmüller 1987), yet natural disturbances and forest dynamics received very little attention therein.…”

Late Holocene fire history and charcoal decay in subtropical dry forests of Puerto Rico

“…Frequent and possibly more intense natural fires occurred around 5200 calibrated years before present (cal yr BP, where 0 yr BP corresponds to 1950 AD) in a coastal region of Puerto Rico (Caffrey andHorn 2014, Rivera-Collazo et al 2015). Regional climate issues in the pan-Caribbean area (e.g., hurricanes and the interannual changes in the position of the Intertropical Convergence Zone; Barry and Chorley 2010) were reported to induce paleofire in Dominica and Cuba (Crausbay et al 2015, Peros et al 2015. Synchrony of fire is a characteristic of climate-driven burning (Caffrey and Horn 2014).…”