Natalia Mesa-Sierra

The tropical dry regions in the Neotropics are under intense anthropogenic pressures, resulting in changes for local communities related with their life patterns, wellbeing, and their relationship with ecosystems. The region has a history of human occupation that has shaped the traditional use of resources. We evaluated the richness, redundancy, and divergence of traditional uses of tree species present in vegetation patches of the tropical dry region of the Gulf of Mexico using functional diversity indices. The most used species are Acacia cochliacantha, Cedrela odorata, Enterolobium cyclocarpum, Gliricidia sepium, and Guazuma ulmifolia, and the uses with the broadest distributions across the region are firewood and pasture management, while reforestation is the least common use. While distance to the nearest patch of the closest human settlement is the most predictive variable associated with inhabitants’ different uses or recognitions of the value of different plant species, the most recognized and valued species are widely distributed in Mexico. Even when the forest cover is greatly reduced, the inhabitants recognize numerous uses that can be obtained from the vegetation patches. The approach used in this work provides important baseline information, as well as a methodology that facilitates the identification of priority areas for conservation.

β-diversity has been under continuous debate, with a current need to better understand the way in which a new wave of measures work. We assessed the results of 12 incidence-based β-diversity indices. Our results of gradual species composition overlap between paired assemblages considering progressive differences in species richness show the following: (i) four indices (β_-2, β_-3, β_-3.s, and β_r) should be used cautiously given that results with no shared species retrieve results that could be misinterpreted; (ii) all measures conceived specifically as partitioned components of species compositional dissimilarities ought to be used as such and not as independent measures per se; (iii) the non-linear response of some indices to gradual species composition overlap should be interpreted carefully, and further analysis using their results as dependent variables should be performed cautiously; and (iv) two metrics (β_sim and β_sor) behave predictably and linearly to gradual species composition overlap. We encourage ecologists using measures of β-diversity to fully understand their mathematical nature and type of results under the scenario to be used in order to avoid inappropriate and misleading inferences.

Deforestation is the dominant threat to tropical dry forests (TDFs) in Mexico. Its causes include agriculture, tourism, and mining. In some cases, unassisted forest regeneration is sufficient to return diverse forest cover to a site, but in other cases, changes in land use are so severe that active restoration is required to reintroduce tree cover. The ecological and social constraints on TDF restoration in Mexico are poorly understood. To address this knowledge gap, we synthesized relevant restoration literature for Mexico published between January 1990 and February 2020. We examined 43 unique articles about TDF restoration practices in Mexico to identify (1) the national distribution of TDF restoration projects, (2) restoration objectives, and (3) factors contributing to TDF restoration success or failure. The largest number of restoration sites were in the Yucatan Peninsula, and the most common objective was to restore dry forest vegetation on lands that had been used for agriculture or impacted by fires. Planting seedlings was the most widely reported restoration strategy, and plant survival was the most frequently monitored response variable. Maximum annual temperature and the Lang Aridity Index were the best predictors of plant survival, which ranged from 15% to 78%. This synthesis highlights how national restoration inventories can facilitate the development of a restoration evaluation framework to increase the efficacy of restoration investments.

Seasonally dry tropical regions in the Neotropics are remarkably biodiverse and provide valuable ecosystem services. Thus, it is crucial to increase and update our information on the biodiversity still preserved within them, particularly in poorly studied areas such as the central coastal plain of the Gulf of Mexico, our study area. A total of 5,583 individuals belonging to 157 species, 113 genera, and 43 families were recorded in 29 forest patches (total sampling area = 8.7 ha). From the floristic composition of these patches, 6 vegetation types were identified: Tropical Dry Oak Forest, Tropical Deciduous Forest, Semi-deciduous Forest, Late Secondary Forest, Intermediate Secondary Forest and Early Secondary Forest. Spatial variation in composition was strongly related to edaphic variables (pH, organic matter, carbon content). Some patches had high local (α) diversity, but even more noteworthy was the distinctively high regional (β) diversity of all the patches together. In spite of the high degree of forest fragmentation in central Veracruz, our results show that it is essential to acknowledge the value of this region to biodiversity and the urgency of developing and implementing protection and management policies that ensure the ecological functions of the landscape and the sustainable development of human activities.