Root production influences a range of belowground processes, such as soil 19 accretion, carbon sequestration and nutrient acquisition. Here, we measured biomass 20 and root production of mangroves surrounding a karstic oligotrophic lagoon that spans a 21 nutrient and salinity gradient. We also measured forest structure and soil 22 physicochemical conditions (salinity, bulk density, carbon, nitrogen (N) and phosphorus 23 (P)) in order to determine factors associated with root production. We tested the 24 following hypotheses: 1) root biomass and production increase at low soil P and N in 25 order to maximize resource utilization, and 2) root biomass and production increase with 26 high interstitial salinity. Root biomass (947-3040 g m-2) and production (0.46-1.85 g m-27 2 d-1) increased where soil P and interstitial salinity were relatively high. Thus, we 28 rejected the first hypothesis and confirmed the second. The larger root fraction (5-20 29 mm) was the major contributor to root biomass and production. Our findings suggest that 30 root production and thus capacity for belowground carbon storage in karstic regions, 31 where P is often limiting, is greater where interstitial salinity and P are higher. This 32 contrasts with past assessments indicating that P-deficiency stimulates root growth, 33 suggesting wide variation in belowground responses in mangroves. 34

Tropical storms can shape the structure and productivity of mangrove forests. In this study, we compared current litterfall with historical tropical storm disturbance in the karstic Yucatan Peninsula (YP). We also explored the relationship between litterfall and the fresh/seawater mixture of floodwater. Our hypotheses were that litterfall peaks at moderate perturbations and in sites where seawater dominates the floodwater mixture, and thus, where soil total phosphorus (TP) is relatively high. Litterfall was sampled for 2 yr, from eight mangrove forests around the YP. At each site, forest structure, interstitial salinity, TP, nitrogen, carbon, pH, and bulk density were measured. Our results show that mangrove forest from northeast YP are historically impacted by stronger and more frequent tropical storms compared with those in northwest and southeast YP, where tropical storm intensity is moderate and mild, respectively. Litterfall was higher in northwest YP (≥3 g/m2 d) compared with northeast and southeast (≤ 2 g/m2 d), mimicking a subsidy‐stress gradient where highest productivity is reached at moderate perturbations. Neither salinity nor forest structure alone satisfactorily explained litterfall variability. Soil TP followed a similar geographical pattern as the disturbance gradient: highest concentrations in the northwest YP (≥0.05%) and lowest in the northeast and southeast (≤ 0.03%). Thus, it is likely that TP, and not tropical storm disturbance, is the main driver of litterfall in mangrove forests of the YP. Alterations in TP availability (e.g., sea level rise and aquifer contamination) have the potential to modify mangrove productivity in the region.

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The restoration of mangroves has gained prominence in recent decades. Hydrological rehabilitation has been undertaken to connect impaired mangroves with the sea, lagoons or estuaries. Because mangrove hydrodynamics occurs on the surface and interstitial spaces in the sediment, we propose to determine the hydrological flow paths to restore the hydrological regimes of the impaired mangroves. The hydrological flow paths were determined through a micro basin analysis based on microtopographic data to generate a digital elevation model. Applying this methodological approach, the hydrology of an impaired area on a barrier island in the Gulf of Mexico was restored by excavating, desilting or clearing the channels on the identified hydrological flow paths. This area was compared to one in which impaired mangroves were reconnected to the marine lagoon but disregarding the flow paths. Data collected in both areas were evaluated by flood level analysis, using two methods: (i) a simple linear regression model (SLRM) and (ii) spectral analysis (SA), also known as dominant frequency analysis. The results suggest that restoration based on the hydrological flow paths was more effective than the direct opening to the nearest main water body without accounting for the microtopography. In both areas, soil salinity and sulfides decreased after hydrological reconnection. However, a greater efficiency in the investment of time and human resources was achieved when preferential flow paths were identified and taken into account. The methodological procedures described in this study are of universal application to other mangrove restoration programs.

This is an open access article distributed under the terms of the Creative Commons Attribution License CC BY-NC (4.0) international.

We evaluated the success of the ecological restoration of a degraded mangrove forest by monitoring the natural regeneration of Avicennia germinans (black mangrove). The restoration actions focused on hydrological rehabilitation by desilting tidal channels and modifying the microtopography to enhance or restore water flow. As a result of these efforts, a population of black mangrove established naturally. Six sampling sites including restored and reference areas were established. We measured seedling survival; tree density, height, and growth rate; and the physical and chemical characteristics of soil and water. According to a redundancy analysis, microtopography and hydroperiod contributed the most to the establishment and development of the black mangrove. Microtopography ranged from 0.08 to 0.14 m above sea level. In the case of the hydroperiod, water level ranged from 0.11 to 0.14 m, flooding duration ranged from 439 to 529 h per month, and frequency was 7 to 8 floods per month. Our results highlight the contribution of microtopography and hydroperiod to the natural establishment of black mangrove. It is important to consider these 2 variables in mangrove ecological restoration.

Background Mangrove forests provide many ecosystem services, including the provision of habitat that supports avian biodiversity. However, hurricanes can knock down trees, alter hydrologic connectivity, and affect avian habitat. In 1995, Hurricanes Opal and Roxanne destroyed approximately 1,700 ha of mangrove forest in Laguna de Términos, Mexico. Since then, hydrological restoration has been implemented to protect the mangrove forest and its biodiversity. Methods Since avian communities are often considered biological indicators of ecosystem quality, avian diversity and species relative abundance were evaluated as indicators of mangrove restoration success by comparing undisturbed mangrove patches with those affected by the hurricanes. Using bird surveys, similarity analyses, and generalized linear models, we evaluated the effects of water quality variables and forest structure on the relative abundance and diversity of the avian community in disturbed, restored, and undisturbed mangrove patches. Results Higher bird species richness and relative abundances were found in disturbed and restored sites compared to the undisturbed site. After restoration, values of frequency of flooding, water temperature, tree density, and the number of tree species were more similar to that of the undisturbed site than to the values of the disturbed one. Such variables influenced the relative abundance of bird guilds in the different habitat conditions. Furthermore, some insectivorous bird species, such as the Yellow Warbler and Tropical Kingbird, were found to be similarly abundant in both undisturbed and restored sites, but absent or very low in occurrence at the disturbed site. Conclusions Collectively, our results strongly suggest that hydrologic restoration helps to enhance niche availability for different bird guilds, including water and canopy bird species. Our work can help inform management strategies that benefit avian communities in mangrove forests and wetland systems.

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