Hurricane impacts on a pair of coastal forested watersheds: implications of selective hurricane damage to forest structure and streamflow dynamics

Abstract

Abstract. Hurricanes are infrequent but influential disruptors of ecosystem processes in the southeastern Atlantic and Gulf coasts. Every southeastern forested wetland has the potential to be struck by a tropical cyclone. We examined the impact of Hurricane Hugo on two paired coastal South Carolina watersheds in terms of streamflow and vegetation dynamics, both before and after the hurricane's passage in 1989. The study objectives were to quantify the magnitude and timing of changes including a reversal in relative streamflow difference between two paired watersheds, and to examine the selective impacts of a hurricane on the vegetative composition of the forest. We related these impacts to their potential contribution to change watershed hydrology through altered evapotranspiration processes. Using over 30 years of monthly rainfall and streamflow data we showed that there was a significant transformation in the hydrologic character of the two watersheds -a transformation that occurred soon after the hurricane's passage. We linked the change in the rainfall-runoff relationship to a catastrophic change in forest vegetation due to selective hurricane damage. While both watersheds were located in the path of the hurricane, extant forest structure varied between the two watersheds as a function of experimental forest management techniques on the treatment watershed. We showed that the primary damage was to older pines, and to some extent larger hardwood trees. We believe that lowered vegetative water use impacted both watersheds with increased outflows on both watersheds due to loss of trees following hurricane impact. However, one watershed was able to recover to pre hurricane levels of evapotranspiration at a quicker rate due to the greater abundance of pine seedlings and saplings in that watershed.

Drought impacts on ecosystem functions of the U.S. National Forests and Grasslands: Part II assessment results and management implications

“…Precipitation (mm yr À1 ) (%) Temperature (°C) ET (mm yr À1 ) (%) Q (mm yr À1 ) (%) GPP (gC m À2 yr À1 ) (%) functions (Hanson and Weltzin, 2000;Dale et al, 2001;Jayakaran et al, 2014). For wildfires, the direct effects on forest ecosystems include vegetation mortality and reducing soil infiltration capacity, consequently leading to a decrease in ecosystem productivity and increase in overland flow and water yield, and soil erosion (Inamdar et al, 2006).…”

Water budget and run‐off response of a tropical multispecies “reforest” and effects of typhoon disturbance

“…The duration of altered streamflow following forest disturbance by typhoons depends on the degree of damage inflicted to the forest as well as on the dynamics and rate of forest recovery. When, on top of defoliation, the structural damage consists mostly of snapped and uprooted trees in the upper stratum, saplings and seedlings may benefit from the increased light levels and increase their biomass, thereby gradually increasing ET over time (Jayakaran et al, ; cf. Yao, Chiang, McEwan, Lin, & Yao, ).…”

“…Yao, Chiang, McEwan, Lin, & Yao, ). Under such conditions, a return to pretyphoon above‐ground biomass and water yield may well take more than a decade (Jayakaran et al, ; cf. Heartsill‐Scalley, Scatena, Lugo, Moya, & Estrada‐Ruiz, ).…”

“…This provided a unique opportunity to study the effect of this particularly extreme event and the associated disturbance of the vegetation on run‐off production. Due to continued oceanic warming, tropical cyclones are expected to become more forceful in the future (Balaguru, Foltz, Leung, & Emanuel, ), and heavy rainfalls in East and South‐east Asia appear to be on the increase as well (Chiang & Chang, ; Walsh et al, ), lending added importance to the study of the hydrological impacts of ecosystem disturbance by extreme events (Jayakaran et al, ; Lin et al, ; Scatena, Planos‐Gutierrez, & Schellekens, ). J. Zhang, Bruijnzeel, Quiñones, et al () reported very low (near‐) surface soil hydraulic conductivities in the Basper grassland, but much higher values for the Manobo reforest, whereas J. Zhang, van Meerveld, et al () showed the landslide‐infested grassland to be extremely responsive to rainfall and to generate large amounts of sediment.…”

Coastal Forests and Groundwater: Using Case Studies to Understand the Effects of Drivers and Stressors for Resource Management

“…In the southeastern U.S., major hurricanes over the past several decades have destroyed large tracts of forests and researchers have analyzed how the succession of forest communities has been affected by these events. Structural damage from intense winds and flooding are the short-term impacts, but the subsequent reduction of the forest canopy and the salinization of soils in the storm surge areas can produce longer-term effects on the water budget, specifically by increasing outflows from coastal watersheds; Hurricane Hugo made landfall in September 1989, and in some respects, the forest ecological processes and streamflow behavior have not yet returned to the pre-storm conditions [45,89]. Coastal forests have evolved resiliencies over millennia and have adapted to short-term impacts, yet widespread demand for forested water resources is cause for increased investigations on the role of groundwater in modulating stresses on forest resources.…”