Setting the stage for the restoration of anAnnona glabraswamp after exotic grass invasion

Abstract

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.

Synthesis of special feature —Tailored Restoration Response: Predictions And Guidelines For Wetland Renewal

“…(P10): The introduction of cattle ranching into the coastal plain of the Gulf of Mexico has reduced the area of natural swamps and entailed the introduction of invasive exotic grasses therein. These grass‐invaded swamps were previously dominated by trees, such as Annona glabra , that is the focus of the restoration potential study by Sánchez‐García et al (2023). Based on the evaluation of environmental conditions in the grass‐invaded areas, these freshwater swamps present a high chance of rehabilitation success, provided the livestock activities are ceased.…”