Seed-dispersal mode and habitat connectivity underpin variation in carbon stocking between Brazilian biomes

In tropical forests, about 60%-80% of woody plant species depend on animal-plant interactions for dispersal. The dependence on animal species for dispersal makes this interaction very fragile in the face of anthropogenic changes in land use. Disrupting seed-dispersal processes, principally zoochoric dispersal, could significantly alter the long-term carbon storage potential of tropical forests. An important question is how landscape structure changes tree carbon stocks in different types of tropical vegetation and how variation is mediated by the dispersal mode of animal (zoochoric) or abiotic (non-zoochoric) seeds. We focused on tree plots at 126 sites in Brazil spanning four types of forest and savanna vegetation, and calculated carbon stored in zoochoric, non-zoochoric, and large frugivore-dispersed species. Our results showed that carbon stocks in zoochoric species and non-zoochoric species differ significantly among vegetation types, with rainforests having higher stocks in zoochoric species and deciduous seasonally dry tropical forests having higher values in non-zoochoric species. A greater area of native vegetation promotes higher proportions of carbon stocks dispersed by large frugivore species, whereas a higher mean shape index reduces this proportion. Synthesis. This study highlights that seed-dispersal type underpins the variation in carbon stocks between vegetation types and that the maintenance of habitat of large dispersers and connectivity are key for retaining carbon stocks in zoochoric species, particularly in rainforest and cerrado sensu stricto. Nas florestas tropicais, cerca de 60 a 80% das especies de plantas lenhosas dependem da interacoes planta-animal para dispersao de suas sementes. Essa dependencia torna a interacao muito fragil face as mudancas antropogenicas no uso da terra. A interrupcao dos processos de dispersao de sementes, principalmente a dispersao zoocorica, pode alterar significativamente o potencial de armazenamento de carbono a longo prazo das florestas tropicais. Uma questao importante e como a estrutura da paisagem altera os estoques de carbono das arvores em diferentes tipos de vegetacao tropical e como a variacao e mediada pelo modo de dispersao de sementes dispersas por animais (zoocoricas) ou abioticas (nao zoocoricas). Nos nos concentramos em parcelas de arvores em 126 locais no Brasil, abrangendo quatro tipos de vegetacao florestal e de savana, e calculamos o carbono armazenado em especies zoocoricas, nao zoocoricas e dispersas por grandes frugivoros. Nossos resultados mostraram que os estoques de carbono em especies zoocoricas e nao zoocoricas diferem significativamente entre os tipos de vegetacao, com as florestas ombrofilas apresentando estoques mais elevados em especies zoocoricas e as florestas deciduas tendo valores mais elevados em especies nao zoocoricas. Uma maior area de vegetacao nativa promove maiores proporcoes de estoques de carbono dispersos por grandes especies frugivoras, enquanto um indice medio de forma mais elevado reduz essa proporcao. Sintese. Este estudo destaca que o tipo de dispersao de sementes sustenta a variacao nos estoques de carbono entre os tipos de vegetacao e que a manutencao do habitat de grandes dispersores e a conectividade sao fundamentais para reter os estoques de carbono em especies zoocoricas, particularmente na floresta ombrofila e no cerrado sensu stricto. This study highlights that seed-dispersal type underpins the variation in carbon stocks between vegetation types. Carbon stocks in zoochoric species and non-zoochoric species differ significantly among vegetation types, with rainforests having higher stocks in zoochoric species and semideciduous seasonally dry tropical forests having higher values in non-zoochoric species.image