Drought stress and hurricane defoliation influence mountain clouds and moisture recycling in a tropical forest

Scholl, Martha A.; Bassiouni, Maoya; Torres-Sanchez, A.

doi:10.1073/pnas.2021646118

Cited by 14 publications

(11 citation statements)

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“…We also considered the proportion of the watershed above 700 m asl, calculated from the Puerto Rico Coast Digital Elevation Model (DEM) (NOAA, 2006), to account for the relationships between increased elevation and moisture that may not be represented by the rainfall data. Cloud condensation begins at approximately 700 m in Puerto Rico (Bassiouni et al, 2017; Scholl et al, 2021; Van Beusekom et al, 2017) and cloud immersion causes actual evapotranspiration rates to be lower above this elevation; in addition, MSWEP rainfall for high elevation wet sites may be underestimated (Beck et al, 2019). Using the DEM, we also calculated watershed slope steepness in the study area (mean watershed slopes of 11–23 degrees), however, slope displayed high collinearity with forest cover and could not be included in our analysis.…”

Section: Methodsmentioning

confidence: 99%

“…The easterly trade winds also deliver additional small-droplet precipitation to high elevation windward watersheds in Puerto Rico that current rainfall data sets are unable to account for. (Scholl et al, 2021). These increase uncertainty in rainfall-streamflow relationships as well as the relationship between forest cover and streamflow in the analysis.…”

Section: Limitations Uncertainties and Other Potential Contributing F...mentioning

confidence: 99%

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Forest cover lessens the impact of drought on streamflow in Puerto Rico

Hall

Scholl

Gorokhovich

et al. 2022

Hydrological Processes

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Tropical regions are experiencing high rates of forest cover loss coupled with changes in the volume and timing of rainfall. These shifts can compromise streamflow and water provision, highlighting the need to identify how forest cover influences streamflow generation under variable rainfall conditions. Although rainfall is the key driver of streamflow regimes, the role of forests is less clear, particularly in tropical regions where forest loss is an ongoing risk. Forest cover loss alters evapotranspiration, rainfall infiltration and storage, and may increase stream ecosystem vulnerability to rainfall extremes. Puerto Rico, an island with spatially heterogenous forest cover and a marked geographic rainfall gradient, is projected to experience more frequent droughts and flash flooding. Using 15‐min streamflow data collected between 2005 and 2016 from 20 US Geological Survey stream gages and 3‐hourly Multi‐Source Weighted‐Ensemble Precipitation rainfall estimates, we utilized flow‐duration curves and linear mixed regression models to examine the role of forest cover in regulating the timing and volume of streamflow. The mixed model approach helps to account for differences in watershed characteristics. We determined the effects of rainfall and forest cover on low and peak flows in Puerto Rican streams, then evaluated changes in these relationships under dry and wet antecedent rainfall conditions. Watersheds with high forest cover had consistently greater low and peak streamflow than deforested ones under all rainfall conditions, although the effect was more marked during wet antecedent conditions, suggesting that peak flow is largely the result of saturation excess overland flow. During dry antecedent rainfall conditions, highly forested watersheds had higher streamflow than deforested ones, suggesting greater hillslope storage and release may also be at play. Our results demonstrate that forest cover generated a net increase in hillslope infiltration and storage and may lessen drought impacts on streamflow in Puerto Rico. Resilience to prolonged drought may be limited by finite water storage potential in this steep, mountainous setting, highlighting maintenance of forest cover as an important water management strategy to increase infiltration.

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Section: Methodsmentioning

confidence: 99%

Section: Limitations Uncertainties and Other Potential Contributing F...mentioning

confidence: 99%

Forest cover lessens the impact of drought on streamflow in Puerto Rico

Hall

Scholl

Gorokhovich

et al. 2022

Hydrological Processes

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“…Tropical forests in Puerto Rico are undergoing constant hurricane disturbances, which are considered agents of ecosystem structuring through direct defoliation as well as drivers of terrestrial-aquatic nitrogen and phosphorus transport [11,12]. The surges of heavy precipitation associated with hurricanes immediately increase surface runoff, which can directly move the soil nitrogen and phosphorous to inland waters [13,14].…”

Section: Introductionmentioning

confidence: 99%

Hurricanes Substantially Reduce the Nutrients in Tropical Forested Watersheds in Puerto Rico

Sun

Wei

Zhou

et al. 2022

Forests

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Because nutrients including nitrogen and phosphorus are generally limited in tropical forest ecosystems in Puerto Rico, a quantitative understanding of the nutrient budget at a watershed scale is required to assess vegetation growth and predict forest carbon dynamics. Hurricanes are the most frequent disturbance in Puerto Rico and play an important role in regulating lateral nitrogen and phosphorus exports from the forested watershed. In this study, we selected seven watersheds in Puerto Rico to examine the immediate and lagged effects of hurricanes on nitrogen and phosphorous exports. Our results suggest that immediate surges of heavy precipitation associated with hurricanes accelerate nitrogen and phosphorus exports as much as 297 ± 113 and 306 ± 70 times than the long-term average, respectively. In addition, we estimated that it requires approximately one year for post-hurricane riverine nitrogen and phosphorus concentrations to recover to pre-hurricane levels. During the recovery period, the riverine nitrogen and phosphorus concentrations are 30 ± 6% and 28 ± 5% higher than the pre-hurricane concentrations on average.

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“…Tropical montane ecosystems are highly vulnerable to rapidly altering temperature and moisture regimes caused by global climate change (Hannah, 2021;Krishnaswamy et al, 2014;Muñoz et al, 2022;Williams et al, 2007) and extreme weather events, especially severe droughts (Foster, 2001;Scholl et al, 2021). Climate change is also causing large shifts in the elevation of orographic clouds and the trade wind inversion (TWI; a synoptic subsidence inversion that traps clouds below a roughly constant elevation, Giambelluca & Nullet, 1991) on tropical mountains, both of which strongly shape climate (Cao et al, 2007;Martin & Fahey, 2014;Marzol-Jaén et al, 2011) and disturbance regimes (Crausbay & Martin, 2016;Martin et al, 2007Martin et al, , 2011) in these ecosystems.…”

Section: Introductionmentioning

confidence: 99%

Resilience of a tropical montane pine forest to fire and severe droughts

2022

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1. Higher temperatures, declining precipitation, changing cloud cover and increased wildfires threaten tropical montane pine forests by overriding the environmental heterogeneity that typically buffers these systems from catastrophic fires. Severe fires threaten to overwhelm forest resilience and tip this biome into alternate vegetation states.2. This study focused on long-term dynamics of montane Pinus occidentalis forests in the Cordillera Central, Dominican Republic after a ~1000 km 2 fire in 2005, the largest since 1965. We used long-term records to investigate climate before and after the fire, and 19-year dataset of pre-and post-fire vegetation change from a network of 55 permanent plots (20 small 0.05 ha plots and 35 large 0.1 ha plots) established in 1999 to model overstorey and understorey vegetation dynamics.3. The 2005 fire was synchronized with the most extreme drought in the region in over 60 years. The fire burned from <1600 to >3000 m a.s.l. in elevation across windward and leeward slopes, creating a mosaic of low-, moderate-and highseverity patches. Lower elevations, leeward slopes and stands with a higher proportion of smaller pine trees all burned at higher severities. 4. Growth rates of trees that survived the fire remained lower than pre-fire rates 13 years after the fire. The highest post-fire mortality rates were soon after the fire and in the census immediately following subsequent post-fire droughts. Postfire pine seedling abundance was significantly greater in stands with higher basal area of live canopy trees and significantly reduced by increased shrub abundance in the understorey. Understorey composition recovered rapidly to pre-fire states in sites affected by low-and moderate-severity fires, but sites affected by highseverity fires remained dissimilar to pre-fire composition 13 years after the fire.Even though high-severity patches had persistently low pine regeneration, 100% of small plots and 96% of large plots had at least one pine sapling or canopy tree recruit by 2018. Shrub taxa survived the fire in higher numbers and recovered to pre-fire densities much faster than the pine, especially in high-severity burns. Synthesis.Climate change has increased the likelihood of wildfires in tropical montane pine forests, with long-lasting effects on vegetation dynamics. However, this biome may prove resilient to increasingly severe fires in the near future, given the ongoing recovery of Pinus occidentalis forests in Hispaniola despite

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Drought stress and hurricane defoliation influence mountain clouds and moisture recycling in a tropical forest

Cited by 14 publications

References 50 publications

Forest cover lessens the impact of drought on streamflow in Puerto Rico

Forest cover lessens the impact of drought on streamflow in Puerto Rico

Hurricanes Substantially Reduce the Nutrients in Tropical Forested Watersheds in Puerto Rico

Resilience of a tropical montane pine forest to fire and severe droughts

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