Journal of Tropical Ecology (2011) 27:195–203. Copyright © Cambridge University Press 2011 doi:10.1017/S0266467410000659 Sprouting, succession and tree species diversity in a South African coastal dune forest Emmanuel Fred Nzunda 1 School of Biological and Conservation Sciences, University of KwaZulu-Natal, South Africa (Accepted 24 September 2010) Abstract: Sprouting may play a significant role in maintenance of plant diversity where prevailing disturbance frequency and severity allows. When disturbance frequency and severity decrease, strong sprouters may be outcompeted. As a result, species composition and diversity may change. This study was carried out to investigate the relationship between sprouting, succession and species diversity in a coastal dune forest that currently suffers from low-severity, chronic disturbance due to sea winds and loose sand substrate. Historically, the site was occupied by shifting cultivators who left the site about 80 y ago. Data on trees that were at least 1.3 m tall from 42 sample plots measuring 20 × 20 m were used. The plots were ranked in order of advancement of succession using the first axis of Principal Components Analysis of forest structural variables. Regeneration pattern was examined using analysis of stem diameter frequency distribution. Abundance and regeneration of strong basal sprouters, incidence of basal sprouting and species diversity decreased with advancement of succession. Only a few species could regenerate under the canopy of late-successional sites. Basal sprouts decreased with advancement of succession whereas trunk sprouts increased. These results suggest that maintenance of high species diversity may need a level of disturbance that allows regeneration and maintenance of strong basal sprouters. Key Words: disturbance severity, forest structure, multi-stemmed trees, plant community dynamics, resprouting, shade tolerance, species composition, succession INTRODUCTION The temporally and spatially patchy nature of disturbance results in temporal and spatial mosaics of vegetation at varying successional stages for which the role of sprouting differs (Bellingham & Sparrow 2000, White & Pickett 1985). Some studies have documented reduction in number of sprouts and stems contributed by sprouting with advancement of succession after catastrophic disturbances, such as logging, slash-and-burn agriculture and fire (Donnegan & Rebertus 1999, Kammesheidt 1998, 1999; McCoy et al. 1999, Rodrigues et al. 2004). Furthermore, there has been observed a negative relationship between canopy height and density, and sprouting of canopy species (Falster & Westoby 2005, Kruger et al. 1997, McCoy et al. 1999), which may suggest that canopy sprouters are light demanding and hence adapted to low canopy, open, early-successional stages 1 Current address: Department of Forest Mensuration and Man- agement, Sokoine University of Agriculture, P.O. Box 3013 Chuo Kikuu, Morogoro, Tanzania. Email: emmanuelnzunda@yahoo.com; nzundaef@gmail.com of forest development (Horn 1974). These observations are commensurate with the argument that sprouting is a strategy useful for recovery after disturbance (Bellingham & Sparrow 2000, Karlsson et al. 2004). However, there are examples of canopy species that sprout under a closed canopy and are late-successional shade-tolerant species (Ohkubo 1992, Ohkubo et al. 1996). This contradiction calls for specific research to establish the role of sprouting in the succession of a given ecosystem. Species diversity may be higher in communities dominated by non-sprouters (Cowling et al. 1997, Kruger & Midgley 2001, Le Maitre & Midgley 1992). However, the relationship between sprouting and species diversity may be confounded if only canopy species are considered (Kruger & Midgley 2001) since the advantages and disadvantages of sprouting change with life-form (Bellingham & Sparrow 2000). Sprouting may enhance species diversity by enabling coexistence through segregation of species according to sprouting ability (Loehle 2000, Nanami et al. 2004). Trees tend to sprout just below the point of damage (Del Tredici 2001). Usually the segment of the tree above the point where sprouts emerge dies and rots. Where disturbance severity is low, trees will produce more