Hurricane disturbances, tree diversity, and succession in North Carolina Piedmont forests, USA

Weimin Xi,Dean L. Urban,Michael T. Lee,Robert K. Peet

doi:10.1007/s11676-018-0813-4

Abstract

Windthrow plays a critical role in maintaining species diversity in temperate forests. Do large-scale strong wind events (i.e., tropical cyclones, including hurricanes, typhoons and severe cyclonic storms) increase tree diversity in severely damaged forest areas? Do hurricanes (tropical cyclones that occurs in the Atlantic Ocean and northeastern Pacific Ocean) lead to altered relative abundance of shade-tolerant and shade-intolerant species? Did historic hurricanes alter the succession trajectory of the damaged forests? We used nearly 70-year tree demographic data to assess the effects of two major hurricanes on woody species diversity in Piedmont forests, North Carolina, USA. Species richness (S) and Shannon–Wiener’s diversity index (H′) were used to evaluate the changes in tree diversity. The changes in composition were assessed with Nonmetric Multidimensional Scaling. The pre-hurricane successional phase can strongly influence both the damage severity and subsequent responses. Although there is often an immediate drop in diversity following a hurricane, understory tree diversity quickly increases to levels that exceed those prior to the disturbance. This leads to an increase in diversity in stands that were substantially damaged. Hurricanes significantly decrease the dominance of shade-intolerant canopy species while increasing pre-established, more shade-tolerant species. We conclude that large, and infrequent hurricanes help to maintain local tree diversity, but also accelerate the increase in dominance of understory species such as red maple and beech.

Highlights

Do large-scale strong wind events increase tree diversity in severely damaged forest areas? Do hurricanes lead to altered relative abundance of shade-tolerant and shade-intolerant species? Did historic hurricanes alter the succession trajectory of the damaged forests? We used nearly 70-year tree demographic data to assess the effects of two major hurricanes on woody species diversity in Piedmont forests, North Carolina, USA
Species diversity at any time is the result of a dynamic balance of recruitment and extirpation of species that reflects the combined influence of historical disturbance and population change
We examined permanent sample plots (PSPs) data from 66-year records to document diversity trends in tree species for both even-aged loblolly pine stands from the thinning phase through to the transition phase, and relatively mature upland mixed-aged hardwood stands (Table 1)

Summary

Introduction

Windthrows caused by large hurricanes and other intensive windstorms have profound impacts on forest structure (Imbert et al 1998; Greenberg and McNab 1998; Elliott et al 2002; Xi et al 2008a; Yang et al 2017), species composition (Spurr 1956; Putz and Sharitz 1991; Vandermeer et al 2000; Xi et al 2008b; Li et al 2018), successional development (Hibbs 1983), carbon storage and emissions (Owari et al 2011), and have been hypothesized to play a critical role in maintaining species diversity in temperate forests (Peet and Christensen 1980; Beckage et al 2000; Xi et al 2008a ( see reviews in Everham and Brokaw 1996; Webb 1999; Peterson 2000; Zhu et al 2004; Xi and Peet 2011; Xi 2015). What is less clear is: (1) how the pre-disturbance community or successional stage influences species diversity; (2) how the juxtaposition of background dynamics and succession influences the postdisturbance trajectory of species diversity; and, (3) how long the disturbance effects influence species replacement and successional trajectory. Clarifying these issues is important for understanding forest recovery, species dynamics, and disturbance-diversity relationships. Many years of pre- and post-disturbance data are critical for understanding long-term tree diversity dynamics

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Conclusion