Inferring population trends of Syagrus coronata (Arecaceae) in areas under different management in Brazilian Caatinga using a transition matrix model

Abstract

Syagrus coronata (Mart.) Becc. (Arecaceae), known as licuri, is a palm tree widely distributed throughout the Brazilian semi-arid, being currently vulnerable to extinction. Its fruits are exploited by both humans and animals, representing high sociocultural, economic, and ecological relevance. This palm tree is found in areas under different management intensity and land use; therefore, both medium and long-term ecological monitoring programs are essential to verify the effects of anthropogenic disturbances on the dynamic of their populations. Information on population structure and growth (λ) from 2018 to 2021 was obtained in 40 plots of 20 × 20 m (1.6 ha). Population matrix models based on five life stages (seedling, sapling, juvenile, immature adult, and reproductive adults) were obtained, in addition to information on fruit productivity and harvesting intensity. Individuals from the seedling stage predominated in both pasture and natural habitats. The populations from two habitats were stable (Pasture λ = 1.00 and Natural λ = 1.01); however, no transition occurred from earlier up to later stages. The population in the pasture was characterized by a low transition rate (recruitment of juveniles onwards), caused mainly by the pressure exerted by cattle. Our results suggest that the adult reproductive and seedling stages are the most important for the survival and growth of the populations. Harvest intensity had no effect on population growth, and only 16.65 % of the fruit annual production was collected. Therefore, fruit harvesting is sustainable, but the type of pasture management might compromise the future of the population. Management strategies ought to reduce the pressure exerted by livestock to increase the transition between stages and maintain the S. coronata populations over several years.