In seasonal plant communities, it is recognized that topography-related variation in water availability and solar radiation determine vegetation structure and community composition; however, the effects on functional structure, particularly through changes in resource use strategies of plants are still poorly understood. This study examines the effects of slope aspect and topographic position on functional trait dominance in a tropical dry forest landscape and explores whether strategies for coping with drought (avoidance vs. tolerance) segregate spatially along the water stress gradient created by the interaction of these two topographic factors. The study was conducted in the Balsas river basin in south-central Mexico. Functional traits were evaluated in 63 species of trees (≥ 2.5 cm diameter at breast height) dominant in plots located at three topographic positions (low, medium and high) and on two slope aspects (north and south). Eight leaf and four stem functional traits, relating to the plants' ability to avoid or tolerate water and temperature stress, were measured. Community-level functional traits were strongly affected by topographic position while only a weak signal was detected by the slope aspect. Contrary to our expectations, attributes associated with drought tolerance predominated on the lower topographic positions of the slopes, (moister and warmer sites), while on the upper parts with drier soil, but cooler air, attributes associated with water stress avoidance dominated. In addition, variation in the dominance of leaf pulvini and trichomes along the topographic gradient suggests environmental filtering by elevated air temperatures and water stress, respectively. Overall, our results suggest that the upper topographic positions that generate a shorter and more fluctuating water-availability window, favor readily-deciduous plants with high levels of water storage in their tissues, traits allowing for a rapid avoid of water stress, whereas on the lower topographic positions, where the soil remains moist for longer periods of time, tardily-deciduous species thrive with dense, low-water content tissues, attributes that are associated with physiological tolerance to drought.

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For the first time in a Neotropical Ficus species (Ficus petiolaris Kunth), the external and internal structural changes in its syconia are described, together with the development of its fig wasps. Ficus petiolaris is endemic to Mexico and represents the northernmost limit of the geographical distribution of the genus in America. Considering the large variation in syconium morphology, we evaluated whether there are differences between syconium development in F. petiolaris and that described for Paleotropical species. We recorded the development of 428 syconia in two individuals from initiation to maturity, weekly, for a period of five months, as well as that of their associated insects. The time required for completion of syconium development ranged from 91 to 126 days. The external morphology of the syconia (color, ostiole size, and thickness of syconium wall) enabled phase recognition. Male and female pollinators (Pegoscapus sp.) and parasitic wasps (Idarnes sp.) were registered. High seed germination values (50%–90%) indirectly tested the positive role of pollinators. Our results are similar to those reported in Paleotropical Ficus species, and should contribute to our understanding of syconium development as well as to the relationships that they maintain with their Agaonidae wasps.

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Erosion prediction models recreate past scenarios, assess future ones, and determine the best explanatory variables of the soil erosion process. They are widely used and contribute valuable data for landscape management. This paper presents an estimation of soil erosion in the Teotihuacan Valley Basin in central Mexico, assessing its response to biophysical and anthropogenic components during 4 periods within the past 2,000 years. The valley has undergone past and recent anthropogenic erosion and, during the past 2 millennia, has experienced a marked variation in precipitation, variations in land use, soil management, and to a lesser extent, variations in soil type. With the use of the Water Erosion Prediction Project model, we estimated how the above‐mentioned parameters affect soil losses under 4 scenarios: (a) humid conditions (900 mm yr−1) during the Teotihuacan Period (1–650 CE), (b) dry conditions (370 mm yr−1) during the Aztec Period (1325–1521 CE), (c) humid conditions (900 mm yr−1) during the Aztec Period, and (d) present conditions (after 1970 CE; 560 mm yr−1). Comparison of scenarios and a principal component analysis of soil loss according biophysical components showed topography to be the most closely related parameter to soil erosion. Land use and soil type also showed a relationship with soil erosion, particularly during the Aztec Period; climate change did not appear to be the most significant factor in soil loss. Estimation of soil erosion by means of models is an inexpensive way to find answers to future challenges concerning soil erosion in a changing environment.

Background: Heteroflorum (Fabaceae) is a monospecific genus endemic to western Mexico. Community attributes of the forest where H. sclerocarpum is found are scarcely known, as well as its similarity with other tropical seasonal forests. Question: What is the composition, structure, and diversity of the tropical deciduous forest where H. sclerocarpum is physiognomically dominant? Study site and date: The study was carried out in the buffer area of the Zicuirán-Infiernillo Biosphere Reserve, in the Churumuco municipality of Michoacán, Mexico (2014). Methods: In three 0.1-ha sites, we sampled trees with a diameter at breast height ≥ 1 cm and lianas whose rooted stem had a diameter of ≥ 1 cm. We calculated the density, biomass, rank-abundance, rank-basal area curves, and alpha and beta diversity measures for each site. Results: We recorded 64 species from 21 families in 0.3 ha. Fabaceae had the highest number of genera, species, individuals, and biomass in all sites sampled. The sites varied in richness (33-41 species), density (176-247 individuals), basal area (2-2.9 m2), and maximum height of trees (12-16 m). Rank-abundance curves differed significantly. Rarefaction curves showed that 0Dα and 1Dα did not differ among sites, while 2Dα separated one of the sites, which also showed a different diversity profile. Beta diversity did not show a strong species turnover among sites (0Dβ, 1.38-1.45; 2Dβ, 1.35-1.56). Conclusions: The composition of trees and shrubs in the forest sampled was similar to other seasonal forests, while the density and diversity were among the lowest values.