Hurricane Katrina impacts on forest trees of Louisiana’s Pearl River basin Elise L. Chapman a , Jeffrey Q. Chambers a, *, Kenny F. Ribbeck b , Dave B. Baker a , Mark A. Tobler a , Hongcheng Zeng a , David A. White c a Tulane University, Department of Ecology and Evolutionary Biology, 400 Lindy Boggs, New Orleans, LA 70115, United States b Louisiana Department of Wildlife and Fisheries, 2000 Quail Drive, Baton Rouge, LA 70808, United States c Loyola University, Biological Sciences, 6363 St. Charles Avenue, New Orleans, LA 70118, United States 1. Introduction Forests of the U.S. Gulf Coast region have experienced hurricane disturbances approximately every 20 years for thou- sands of years (Conner et al., 1989). For a community composed of long-lived organisms such as trees, these events can dramatically alter ecological interactions and ecosystem processes. Ecosystem attributes that influence storm damage and subsequent recovery are numerous. Factors that affect tree damage and mortality include wind speed, forest structure, tree species composition, and unique characteristics of the study area (Everham, 1995; Foster and Boose, 1995). Damage sustained by forests during a catastrophic storm also exhibits a high level of spatial hetero- geneity (Brokaw and Grear, 1991; Lugo, 2000; Chambers et al., 2007). For bottomland hardwood forest ecosystems, differences in species composition and tree size interact to result in a disturbance continuum, rather than discrete disturbance regimes (Battaglia et al., 1999). All of these factors impede efforts to predict the impact of a given storm. Disturbance and recovery responses after forest impact suggest hurricanes can play an important role in influencing tree species community composition. Differential recruitment of tree species, varied distribution of resources throughout the environment, and new and altered microenvironments may result in significant shifts in community composition (Boose et al., 1974; Beatty, 1984). However, many studies find few compositional differences after a major storm dramatically alters the physical structure of a forest (Yih et al., 1991; Boucher et al., 1994; Scatena and Lugo, 1995; Weaver, 2002). A similar composition to pre-disturbance forest is attributed to the mode of recovery, where advanced regeneration is released, and vegetative sprouting of survivors may lead to only minor changes in tree species community structure (Whigham et al., 1989; Brokaw and Grear, 1991; Tanner et al., 1991; Yih et al., 1991). Previous studies have investigated the impact and response of Gulf Coast bottomland hardwood forests to damaging storms. In these ecosystems, a catastrophic disturbance event is likely to severely damage up to half the forest trees (Putz and Sharitz, 1991), Forest Ecology and Management 256 (2008) 883–889 ARTICLE INFO Article history: Received 20 June 2007 Received in revised form 17 May 2008 Accepted 19 May 2008 Keywords: Tropical cyclone Oak Taxodium Nyssa Quercus Liquidambar Wetlands NEP NPP Carbon balance ABSTRACT Hurricane disturbance has the potential to markedly affect coastal forest structure and ecosystem processes. This study focused on the impacts of Hurricane Katrina in Louisiana’s Pearl River basin, which lies just west of Katrina’s final landfall at the Louisiana–Mississippi border. Prior to landfall, composition and structure of bottomland hardwood forests in this region were studied with permanent forest inventory plots sampled in 1989, 1998, 2005 and following the storm in 2006. This enabled a direct comparison of forest structure and dynamics before and after the disturbance, including species-specific tree mortality and damage rates, biomass production, and differences among forest types having varied hydrologic regimes. Background tree mortality rate before Hurricane Katrina was 1.9%, while average annual mortality was 20.5% for the census interval including the disturbance. Change in live tree biomass estimated from allometric models demonstrated a shift from an average annual production of 3.5 Mg ha 1 before the disturbance, to an average loss of 77.6 Mg ha 1 from the storm. Damage associated with Hurricane Katrina varied significantly with tree species but not tree size. Flooded cypress-tupelo swamp forests sustained the least damage and frequently flooded bottomland hardwood forests sustained the highest damage. Hurricane disturbance influenced the structure and composition of these coastal forests through species-specific differences in damage and mortality rates, and varied impacts dependent on forest flooding regime. ß 2008 Elsevier B.V. All rights reserved. * Corresponding author. Tel.: +1 504 862 8291. E-mail address: chambers@tulane.edu (J.Q. Chambers). Contents lists available at ScienceDirect Forest Ecology and Management journal homepage: www.elsevier.com/locate/foreco 0378-1127/$ – see front matter ß 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.foreco.2008.05.057