No abstract

During the last century the mean sea level has been increasing at a rate of 0.2 to 0.4 mm•year -1 , and that rate is expected to accelerate during this century. Coastal wetland ecosystems are sensitive to the potential changes and impacts of resulting from a rise in sea level. In the coastal region of the Gulf of Mexico, freshwater swamps are wetlands located further inland than mangroves, and while in uenced by the tides maintain freshwater conditions. Due to their location, the rise in sea level could increase the levels of ooding and salinity in these ecosystems. The objective of this study was to evaluate, under greenhouse conditions, the effect of nine ood and salinity treatments on the survival, growth and increase in the biomass of Annona glabra (pond apple) seedlings. The treatments combined two factors: water level (saturation, ood, ood-drought) and salinity (0, 5 and 15 ‰). Germinated seedlings were used (average height: 18.6 ± 1.61 cm). Seedling survival was greater under freshwater conditions.Increase in height and diameter, as well as leaf and biomass gain, were greater under saturation and freshwater conditions. Based on our results, we conclude that under a scenario of rising sea level, increased ood levels and salinity will negatively affect the natural establishment of Annona glabra seedlings in freshwater swamps.

The magnitude of facilitation by shelter-building engineers on community structure is expected to be greater when they increase limited resources in the environment. We evaluated the influence of local environmental context on the colonisation of leaf shelters by arthropods in a Mexican evergreen tropical rainforest. We compared the species richness and abundance of arthropods (total and for different guilds) colonising artificially rolled leaves in habitats differing in understory heterogeneity (forest edge > old-growth forests > living fences). Arthropod abundance of the most representative arthropod taxa (i.e., Araneae, Blattodea, Collembola and Psocoptera) colonising the rolled leaves was greater at forest edge, a trend also observed for average arthropod abundance, and for detritivore and predator guilds. In addition, fewer arthropod species and individuals colonised the rolled leaves in the living fence habitat, a trend also observed for most arthropod guilds. As forest edge is expected to have a greater arthropod diversity and stronger density-dependent interactions, a greater limitation of refuges from competitors or predators may have determined the higher colonisation of the rolled leaves in this habitat. Our results demonstrate that local environment context is an important factor that affects the colonisation of arthropods in leaf shelters.

The expansion of cattle ranching in the coastal plain of the Gulf of Mexico is transforming freshwater swamps resulting in the reduction of swamps area and the introduction of invasive exotic grasses. This study seeks to determine the structure of the remaining population of Annona glabra in a grassland, evaluate vegetation and environmental conditions of the grassland, and determine the germination capability of A. glabra under different cover conditions of grass growth and two flood levels. The study area is a flooded grassland invaded by Echinochloa pyramidalis in central Veracruz, Gulf of Mexico. In the grassland, we censused and mapped the remaining individuals of A. glabra. We sampled the vegetation and measured the physicochemical characteristics of the soil and water. To evaluate the effect of the invasive grass on the germination of A. glabra seeds, we designed two greenhouse experiments: one (E1) under soil moisture at field capacity and another (E2) under flooded conditions. We found 312 remnant individuals. We recorded 31 plant species, most (72.7%) classified as aquatic/semiaquatic. The relative importance value was highest for E. pyramidalis, Mimosa pigra, and Eleocharis mutata. BEST analysis did not detect significant correlations between vegetation and physicochemical variables, indicating homogeneous environmental conditions. Seed germination was above 80% in E1 and below 20% in E2 in all grass cover levels. Although flooding decreases germination rates, substantial proportion of seeds can germinate, suggesting that natural succession is viable. Based on our results, the flooded grassland has conditions to restore swamp.

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.