Towards the restoration with Annona glabra (Annonaceae) of a freshwater swamp: seedling establishment and growth, and the accompanying vegetation change

Abstract

Background and Aims: Currently, freshwater swamps are deteriorating and their cover is decreasing, mainly due to deforestation for livestock and the introduction of exotic grasses. The objectives of this study were to evaluate the survival and the growth of Annona glabra seedlings, monitor changes in the accompanying vegetation, and estimate the cost of our experimental ecological restoration treatments in a freshwater swamp transformed into a flooded pasture and invaded by the exotic grass Echinochloa pyramidalis.Methods: The study was carried out on a floodplain surrounding a mangrove on the coast of central Veracruz, Mexico. It consisted of sowing four A. glabra seedlings in experimental quadrats exposed to different restoration techniques. Fifteen experimental restoration treatments were tested consisting of five restoration techniques (no modification, covering with plastic, planting Pontederia sagittata, soil removal, and raising the soil level), and three pretreatments applied to the seedlings planted (nursery seedlings with and without fertilizer, seedlings collected from the wetlands) in a random block design.Key results: Low seedling survival was recorded (30.7%), but this was higher for the seedlings from freshwater wetlands (41.1%). The highest percent survival was recorded where the soil was raised, followed by the soil removal technique. Regarding the vegetation, 40 species were recorded and the highest species richness was observed where the soil had been raised and where it had been removed. The Relative Importance Value was highest for Echinochloa pyramidalis, Mimosa pigra, and Annona glabra. The pretreatment of obtaining seedlings directly from the wetland was the cheapest one.Conclusions: Action is required to increase reforestation success. For future restoration projects, we recommend that the soil in the transplanting area be raised and covered with plastic before planting, to increase the probability of seedling survival and reduce grass cover. Moreover, seedlings collected from a swamp fragment should be used for reforestation.