Cattle effects on seed dispersal, germination, and seedling recruitment of a threatened brazilian dry forest palm tree (Syagrus coronata)

Abstract

Syagrus coronata (Arecaceae) is a palm widely distributed throughout the Brazilian semi-arid region presenting high sociocultural, economic, and ecological importance. Anthropogenic disturbances have led to a defaunation of wild birds and mammal dispersers, compromising the seedling recruitment. Herein, we verified the livestock effects on S. coronata dispersal, germination, and establishment of regenerant stages in dry forest vegetation and pasture. Seed dispersal was assessed using 72 experimental arenas for measuring dung beetles’ functions facilitated by cattle. We applied a completely randomized design for the germination experiment with 400 seeds divided into four groups: 1) control, 2) mechanically scarified seeds, 3) seeds ingested by cattle and recovered from feces, and 4) seeds both ingested by cattle and mechanically scarified. We assessed the survival rates of regenerating S. coronata individuals (seedlings, saplings, and juveniles) in 40 plots (20 × 20 m) over a year. We found cattle as a potential disperser and facilitator of secondary dispersal for 43% of seeds, mainly in pastures. Mechanical scarification treatment reached the greatest germination percentage. Seed passage through the digestive tract of cattle treatment increased germination compared with the control. In contrast, combining mechanical and digestive bovine tract scarification damages the seeds. There was a negative cattle effect on survival of regenerants, in which their establishment is a crucial stage in the life cycle of palms. This study provides information for farming practices in areas of extractive use, contributing to S. coronata population conservation.