Aim: Spatial patterns in resource supply drive variability in vegetation structure and function, yet quantification of this variability for tropical dry forests (TDFs) remains rudimentary. Several climate-driven indices have been developed to classify and delineate TDFs globally, but there has not been a climo-edaphic synthesis of these indices to assess and delineate the extent of TDFs. A statistical climo-edaphic synthesis of these indices is therefore required. Location: Pantropical. Time period: Modern. Major taxa studied: Vascular plants. Methods: We assembled most known prior descriptions of TDFs into a single data layer and assessed statistically how the TDF biome, which we call tropical dry landscapes (TDLs) composed of forest and non-forest vegetation, varied with respect to the normalized difference vegetation index (NDVI) sensed by MODIS (250 m pixel resolution). We examined how the NDVI varied with respect to mean annual temperature (MAT) and rainfall (MAR), precipitation regime, evapotranspiration and the physical, chemical and biological properties of TDL soils.Results: Overall, the NDVI varied widely across TDLs, and we were able to identify five principal NDVI categories. A regression tree model captured 90% of NDVI variation across TDLs, with 14 climate and soil metrics as predictors. The model was then pruned to use only the three strongest metrics. These included the Lang aridity index, total evapotranspiration (ET) and MAT, which aligned with identified NDVI thresholds and accounted for 70% of the variation in NDVI. We found that across a global TDL distribution, ET was the strongest positive predictor and MAT the strongest negative predictor of the NDVI. Main conclusions:The remote sensing-based approach described here provides a comprehensive and quantitative biogeographical characterization of global TDL occurrence and the climatic and edaphic drivers of these landscapes.

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.

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 βr) 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 (βsim and βsor) 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.

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The pervasive loss of primary forest in the tropics means that we need a better understanding of how transforming tropical landscapes affects plant regeneration if we wish to recover and maintain the diverse composition, structure, and function of tropical forest and landscapes. Advance regeneration (AR) is a crucial stage in forest dynamics; it includes all the immature woody plants that germinate and establish and may eventually form part of the forest as adults. In this study, we describe AR in three contiguous habitats in the tropics of central Veracruz, Mexico: a protected tropical semideciduous forest, a 17-year-old secondary forest (SF), and coastal dune scrub (DS). The community attributes of the AR were analyzed among and within the three habitats as were the relationship between its spatial variability and microenvironmental conditions and the attributes of the adult woody vegetation. In total, 3,195 individuals belonging to 95 species and 40 families were recorded in 90 quadrats of 25 m 2 (sampling area: 2,250 m 2). Brosimum alicastrum (Moraceae) was the most abundant species (1,498 individuals) and occurred in all three habitats. Despite having an adult community dominated by secondary species, the AR of the SF had a high degree of similarity with the primary forest. In the DS, late successional species were rare indicating it will likely take centuries for it to become a forest. Regardless of the severe fragmentation of the area and its nutrient-poor sandy soils, our results show that the seasonally dry tropical region of central Veracruz is highly resilient.