Reduced hornbill abundance associated with low seed arrival and altered recruitment in a hunted and logged tropical forest

• Published in: PloS one Vol. 10; no. 3; p. e0120062
• Main Authors: Naniwadekar, Rohit, Shukla, Ushma, Isvaran, Kavita, Datta, Aparajita
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 17.03.2015; Public Library of Science (PLoS)
• Subjects: Abundance; Aceros nipalensis; Animals; Anorrhinus tickelli austeni; Anthracoceros albirostris; Birds - physiology; Buceros bicornis; Cochoa purpurea; Cochoa viridis; Dispersal; Dispersion; Ducula badia; Flowers & plants; Food; Food plants; Food processing plants; Forests; Gracula religiosa; Hoolock hoolock; Hunting; Logging; Logging industry; Macaca arctoides; Macaca assamensis; Macaca leonina; Macaca mulatta; Megalaima virens; Muntiacus muntjak; Pathways; Rainforests; Recruitment; Rhyticeros undulatus; Rusa unicolor; Scattering; Seed dispersal; Seeds; Sus scrofa; Trees; Tropical Climate; Tropical environments; Tropical forests; Wildlife; Borneo; India
• DOI: 10.1371/journal.pone.0120062
• ISSN: 1932-6203

Logging and hunting are two key direct threats to the survival of wildlife in the tropics, and also disrupt important ecosystem processes. We investigated the impacts of these two factors on the different stages of the seed dispersal cycle, including abundance of plants and their dispersers and dispersal of seeds and recruitment, in a tropical forest in north-east India. We focused on hornbills, which are important seed dispersers in these forests, and their food tree species. We compared abundances of hornbill food tree species in a site with high logging and hunting pressures (heavily disturbed) with a site that had no logging and relatively low levels of hunting (less disturbed) to understand logging impacts on hornbill food tree abundance. We compared hornbill abundances across these two sites. We, then, compared the scatter-dispersed seed arrival of five large-seeded tree species and the recruitment of four of those species. Abundances of hornbill food trees that are preferentially targeted by logging were two times higher in the less disturbed site as compared to the heavily disturbed site while that of hornbills was 22 times higher. The arrival of scatter-dispersed seeds was seven times higher in the less disturbed site. Abundances of recruits of two tree species were significantly higher in the less disturbed site. For another species, abundances of younger recruits were significantly lower while that of older recruits were higher in the heavily disturbed site. Our findings suggest that logging reduces food plant abundance for an important frugivore-seed disperser group, while hunting diminishes disperser abundances, with an associated reduction in seed arrival and altered recruitment of animal-dispersed tree species in the disturbed site. Based on our results, we present a conceptual model depicting the relationships and pathways between vertebrate-dispersed trees, their dispersers, and the impacts of hunting and logging on these pathways.