Journal of Tropical Ecology (2010) 26:25–33. Copyright © Cambridge University Press 2009 doi:10.1017/S0266467409990344 Patterns of seed rain and seedling regeneration in abandoned agricultural clearings in a seasonally dry tropical forest in India Karthik Teegalapalli ∗,1 , Ankila J. Hiremath† and Devcharan Jathanna‡ ∗ Wildlife Conservation Society-India Programme, Post-graduate Programme in Wildlife Biology and Conservation, National Centre for Biological Sciences, PO Box 6501, Hebbal, Bangalore-560 065, India † Ashoka Trust for Research in Ecology and Environment, K-1 Commercial Complex, Birbal Road, Jangpura Extension, New Delhi-110014, India ‡ Wildlife Conservation Society-India Programme, Centre for Wildlife Studies, 1669, 31st Cross, 16th Main, Banashankari 2nd stage, Bangalore, Karnataka-560 042, India (Accepted 27 August 2009) Abstract: Forest recovery in abandoned pastures and agricultural fields is often impeded, therefore it is important to understand the factors limiting regeneration. Patterns of seed arrival and regeneration in five abandoned agricultural clearings nested within a seasonally dry tropical forest in India were examined along five transects radiating from the forest edge into the clearings. Wind-dispersed seeds dominated the seed arrival in clearings compared with vertebrate- dispersed seeds: 5563 wind-dispersed seeds and 1094 vertebrate-dispersed seeds of 14 and 13 tree species, respectively, were recorded. Numbers of the former declined steeply with increasing distance from the forest, whereas the latter showed no evident pattern with distance. Seeds of the invasive herb, Chromolaena odorata, were abundant in clearings. Although wind-dispersed seeds greatly outnumbered vertebrate-dispersed seeds, seedlings and saplings of vertebrate- dispersed species were three times more abundant than those of wind-dispersed species, indicating distinct differences in patterns of actual and effective seed dispersal. This points to recruitment limitation, and suggests that seed arrival may not be the principal barrier to regeneration in these clearings. Nonetheless, the clearings are likely to revert to forest over time. Key Words: agricultural clearings, Chromolaena odorata, regeneration, seasonally dry tropical forests, seed dispersal INTRODUCTION Across the tropics, vast expanses of forest have been converted into pastures and agricultural fields and subsequently abandoned (Brown & Lugo 1990, Chapman & Chapman 1999). In such tropical forest clearings, seed arrival has been shown to be a critical limitation to forest recovery, with most seeds dispersed close to the forest edge; post-dispersal seed predation and seedling herbivory after germination also inhibit regeneration (Aide & Cavelier 1994, Cubi ˜ na & Aide 2001, Holl 1999, McClanahan & Wolfe 1993, Uhl 1987, Willson & Crome 1989). Existing vegetation such as remnant trees and shrubs may facilitate regeneration (Duncan & Chapman 1999, Galindo-Gonzalez et al. 2000, Guevara et al. 2004, Holl 2002, Willson & Crome 1989) whereas grasses and ferns may impede tree regeneration (Aide et al. 1995, Holl 1998, Slocum et al. 2004). Abiotic factors such 1 Corresponding author. Email: karthik.teegalapalli@gmail.com as low concentrations of soil nutrients due to several years of cultivation, and harsh microclimatic conditions compared to adjoining forest, can further impede tree regeneration (Aide & Cavelier 1994, Holl 1999, Uhl 1987). In tropical moist and wet forests, over 80% of tree species are vertebrate-dispersed (Ganesh & Davidar 2001, Howe & Smallwood 1982, Vieira & Scariot 2006), and their dispersal is adversely affected by forest fragmentation, since animals are less likely to traverse open habitats (Aide & Cavelier 1994, Cubi ˜ na & Aide 2001, Holl 1999). In seasonally dry tropical environments, however, more than a third of all tree species are wind- dispersed (Justiniano & Fredericksen 2000, Kahn & Lawrie 1987, Parthasarathy & Karthikeyan 1997), and seed dispersal is likely to be somewhat less affected by fragmentation and opening-up of habitats (Gillespie 1999, Vieira & Scariot 2006). Studies of forest recovery in abandoned pastures and agricultural fields have been conducted mostly in the humid tropics, with few studies carried out in the dry