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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. [ABSTRACT FROM AUTHOR]

Tropical freshwater swamps provide essential ecosystem services, such as flood mitigation and control. Land use changes cause alterations in their hydrology, increasing risks of degradation caused by extreme events like storms and hurricanes. We evaluated the effectiveness of different strategies to control opportunistic herbaceous vegetation, as a factor limiting the establishment of the dominant money tree Pachira aquatica for the restoration of swamps in the coastal floodplains of the Gulf coast in Mexico. Pachira aquatica saplings were planted in four treatments: (1) Control (saplings without further intervention), (2) Cut (herbaceous vegetation removal), (3) cutting with Vegetation mulch, and (4) cutting with Plastic cover. The effect of treatments on survival and relative growth rate (RGR) of P. aquatica saplings and on the herbaceous cover was measured after 2 years. Costs per treatment were also calculated. Saplings in the Control had the lowest survival (5.0%; only one seedling survived), followed by Cut (35.0 ± 12.75%), Vegetation mulch (70.0 ± 9.35%), and Plastic cover (95.0 ± 5.0%). Sapling height and RGR were similar among treatments. The herbaceous layer cover was reduced to ~30% in Vegetation mulch and Plastic cover in comparison to Control and Cut treatments with ~94%. The most cost‐effective treatment was Vegetation mulch, with almost half the cost of Plastic cover. Our results support the establishment of restoration plantings with P. aquatica to assist the recovery of swamps and highlight the need to include complementary interventions, to ensure higher tree sapling survival and to avoid total restoration failure in this system. [ABSTRACT FROM AUTHOR]

In wetlands, hydrochory is one of the main mechanisms of seed dispersal and there is often synchrony between propagule production and the flood season. Different sources of disturbance can prevent seed dispersal to suitable sites, and if environmental conditions are not adequate for germination and seedling establishment, recruitment will be limited, affecting succession.We worked in a disturbed tropical freshwater swamp where the native grass Leersia hexandra has dominated open areas, creating a grass matrix that surrounds patches of swamp forest. Leersia grows vigorously, forming cushions of dry matter that cover the soil, forming a potential obstacle to seed dispersal. We asked whether the vegetative growth of this grass prevents the entry and dispersal of seeds of the tropical swamp tree Pachira aquatica, thwarting seed germination and seedling establishment, and arresting succession. We set up transects in the grass matrix in two zones: close to the river (R) and bordering the tree patches or fragments (F). We quantified tree seed and seedling presence, survival and growth in situ and experimentally introduced seeds and seedlings in the field and monitored seed germination and the survival and growth of their seedlings, as well as that of transplanted seedlings.There was a negative relationship between the number of seeds and established seedlings, and the distance to river or fragment (r = −0.86, p < 0.001 for zone R; and r = −0.77, p < 0.001 for zone F) and with the grass cushion (r = −0.68, p = 0.005 for zone R; and r = −0.66, p = 0.007 for zone F); the grass creating a barrier to dispersal. When seeds were sown after clearing the grass cushion, germination success was high, so this stage is not limited. The transplanted seedlings had better survival and a greater final height than the seedlings of the sown seeds. Grass cover had a negative effect on both types of seedlings. Seedling survival rates were inversely related to grass cover, showing that seedlings overgrown by grass had low survival rates. Flooding is a stress factor for seedlings and produced mortality, in addition to the effects of the grass.Together, the field survey and the experiment show that succession is being arrested in two ways: (1) by limiting seed dispersal because the grass cushion slows the dispersal and penetration of seeds into the vegetation; and (2) by limiting seedling establishment because the grass competes for space and light. Our results show that even where the grass is native, slower growing, seed‐dependent species may struggle to compete and establish. If grass cover is increasing, these swamps are very vulnerable to a decrease in area because it is very difficult for them to regenerate naturally. [ABSTRACT FROM AUTHOR]

The identification and quantification of global change, including climate change, requires long time series of key variables. In this work, the fundamentals and operation of low-cost long-term coastal observatories are described, and preliminary data are shown. The vision is to offer a scientific platform of physicochemical data for at least the next 100 years, what requires establishing sustainable strategies, training human resources, strong institutional support, and long-term funding sources. The network formally operates since 2013 and has generated more than 6 million data points, continuously growing, of which >1.5 million data points are permanently stored and available through a public access web platform. The strategies and methodologies are described and, in the Mazatlan observatory, data recovery and basic statistics of eight environmental variables are presented. During 2015, an extreme El Niño year, marine temperatures increased from the bay to the middle Urias coastal lagoon, were higher than atmospheric temperatures, and showed the impact of a thermal power plant. In surface waters of Mazatlan bay, hypoxic periods were also observed. It is expected that results will foster the development of other projects, and will be useful to the scientific community and decision makers, for a better management of coastal ecosystems worldwide. [ABSTRACT FROM AUTHOR]

Echinochloa pyramidalis (Lam.) Hitchc. & Chase is an African grass with C4 photosynthesis, high biomass production, and high vegetative propagation that is tolerant to grazing and able to grow in flooded and dry conditions. Thus, it is highly invasive in tropical freshwater marshes where it is intentionally planted by ranchers to increase cattle production. This invasion is reducing plant biodiversity by increasing the invader's aerial coverage, changing wetland hydrology and causing soil physicochemical changes such as vertical accretion. Reducing the dominance of this species and increasing the density of native wetland species is a difficult, expensive, and time-consuming process. We applied a series of disturbance treatments aimed at eliminating E. pyramidalis and recovering the native vegetation of a partially invaded freshwater marsh. Treatments included physical (cutting, soil disking, transplanting individuals of the key native species Sagittaria lancifolia subsp. media (Micheli) Bogin, and/or reducing light with shade mesh) and/or chemical (spraying Round-Up™ herbicide) disturbances. At the end of the experiment, four of the five treatments used were effective in increasing the cover and biomass of native species and reducing that of E. pyramidalis. The combination of these treatments should be used to generate a proposal for the restoration of tropical wetlands invaded by non-native grasses. A promising treatment is using soil disked to soften the soil and destroy belowground structures such as roots and rhizomes. This treatment would be more promising if combined with the use of shade cloth. If it is desirable not to impact the soil or if there is not enough budget to make an effort to include active restoration disking soil, the use of shade cloth will suffice, although the recovery of native vegetation will be slower. [ABSTRACT FROM AUTHOR]