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Recurrent tree defoliation by pastoralists, akin to herbivory, can negatively affect plant reproduction and population dynamics. However, our understanding of the indirect role of defoliation in seedling recruitment and tree-grass dynamics in tropical savanna is limited. In West African savanna, Fulani pastoralists frequently defoliate several fodder tree species to feed livestock in the dry season. We investigated the direct and indirect effects of recurrent defoliation of African mahogany ( Khaya senegalensis ) by Fulani people on seedling (<2 cm basal diameter) and sapling dynamics in West Africa using four years of demographic data on seedling and sapling density, growth, and survival, coupled with fruit production and microhabitat data over the same time period. Tree canopy cover facilitated seedlings but had negative effects on sapling growth possibly via intraspecific competition with adult plants. Interspecific competition with grasses strongly reduced seedling survival but had a weak effect on sapling growth. Fire reduced seedling survival and weakly reduced growth of seedlings and saplings, but did not affect sapling survival. These results indicate that the effect of fire on seedlings and saplings is distinct, a mechanism suitable for an episodic recruitment of seedlings into the sapling stage and consistent with predictions from the demographic bottleneck model. Defoliation affected seedling density and sapling growth through changes in canopy cover, but had no effect on seedling growth and sapling survival. In the moist region, sapling density was higher in sites with low-intensity defoliation, indicating that defoliation may strengthen the tree recruitment bottleneck. Our study suggests that large-scale defoliation can alter the facilitative role of nurse trees on seedling dynamics and tree-sapling competition. Given that tree defoliation by local people is a widespread activity throughout savanna-forest systems in West Africa, it has the potential to affect tree-grass coexistence. Incorporating the influence of large tree defoliation into existing models of savanna dynamics can further our understanding of tree-grass coexistence and improve management. A rotating harvest system, which allows seedlings to recruit episodically, or a patchwork harvest, which maintains some nursery trees in the mosaic, could help sustain seedling recruitment and minimize the indirect effects of harvest.

1. The Cerrado Domain of central Brazil houses the largest extent of savanna in the Neotropics, but despite its simple characterization as a giant savanna, it contains considerable vegetation heterogeneity that is poorly understood. 2. We aimed to determine how vegetation types in the Cerrado diverge in their tree species composition and what role ecological factors play in driving compositional patterns. 3. We used a dataset of 1,165 tree species inventories spread across the Cerrado Domain, which come from six vegetation types that have a substantial arboreal component: woody savannas, dystrophic cerradāo, mesotrophic cerradāo, seasonally dry tropical forests, semideciduous forests and evergreen forests. We found three extremes in terms of tree species composition, with clear underlying ecological drivers, which leads us to propose a ternary model, the Cerrado Vegetation Triangle, to characterize woody vegetation in the Cerrado. At one extreme, we found that semideciduous and evergreen forests are indistinguishable floristically and are found in areas with high water availability. At another extreme lie seasonally dry tropical forests which are found on more fertile soils. At the third extreme, we found that all types of savanna, and dystrophic cerradão, are highly similar in tree species composition and are commonly found in areas of poor soils and high flammability. Mesotrophic cerradão is transitional in tree species composition between savannas and seasonally dry tropical forest. 4. The lack of variation in tree species composition attributed to climatic variables indicates that within homogeneous macroclimatic zones, many types of forest and savanna co-exist due to complex mosaics of local substrate heterogeneity and fire history. 5. Synthesis. Our findings highlight the complexity of forest-savanna transitions in the Cerrado Domain, with relevance for understanding the future of Cerrado vegetation under environmental change. If nitrogen deposition is extensive, some savannas may be more likely to transition to mesotrophic cerradão or even seasonally dry tropical forest, whereas if water availability increases these same savannas may transition to semideciduous or evergreen forest. Our \"Cerrado Vegetation Triangle\" model offers a simple conceptual tool to frame discussions of conservation and management.

Ground and surface water hydrology often governs the abundance and type of vegetation present in dryland riparian ecosystems, particularly along rivers that have both perennial and intermittent reaches. But how these differences in riparian vegetation affect riparian arthropod communities is not well understood. I conducted a replicated field experiment at three sites along the San Pedro River in central Arizona, United States, which varied in ground and surface water hydrology and in riparian vegetation. The most mesic site was comprised of cottonwood‐willow gallery forest and had more canopy cover, higher absolute humidity, and lower maximum air temperature than the most arid site, which was comprised of mesquite and saltcedar scrubland. Experimental treatments added resources (water, sugar, and a no resource control) to assess water and energy limitation of ground‐dwelling arthropods over a 4‐week period. I found that arthropod community structure differed between the three study sites, and that these changes were strongly associated with differences in microclimate. The most mesic site had 5.5 times greater arthropod biomass than the most arid site. I also found that the effect size of water supplementation on cricket abundance and the effect size of sugar supplementation on ant abundance were related to microclimate variables. Water effects on cricket abundance were larger, and sugar effects on ant abundance smaller, as general aridity increased. However, I found no relationship between the magnitude of water or sugar effects on total arthropod community abundance and microclimate variables. Nevertheless, these results indicate that groundwater depth can indirectly affect the abundance, community structure, and water vs. energy limitation of riparian arthropod communities via groundwater effects on riparian vegetation, and riparian vegetation effects on microclimate. Increases in river drying events due to climate change and increased water withdrawals will likely lead to changes in riparian vegetation in arid systems, and here I show that these changes could affect riparian animal communities as well.

We report a new locality for the endemic glassfrog Vitreorana franciscana Santana, Barros, Pontes & Feio, 2015 from Brazilian Cerrado, from the municipality of Nova Ponte, state of Minas Gerais, Brazil. Field visits were conducted in 2023 at Fazenda Brejão and resulted in the fourth record of this species, which expands this species’ geographic distribution by 150 km to the east. With the new record, the minimum convex polygon for the species is now 18,210 km2.

Tropical savanna and forest are recognized to represent alternate stable states, primarily determined by feedbacks with fire. Vegetation-fire dynamics in each of these vegetation types are largely determined by the influence of the vegetation on fire behavior, as well as the effects of fire behavior on tree mortality, topkill (defined here as complete death of the aerial biomass, regardless of whether the plant recovers by resprouting), and rate of growth of resprouts. We studied the effect of fire on three savanna-forest boundaries in central Brazil. Fire intensity was greater in savanna than forest, as inferred by a twofold greater height of stem charring. Despite lower fire intensity, forest tree species exhibited higher rates of topkill, which was best explained by their thinner bark, relative to savanna species. Following topkill, there was no tendency for sprouts of savanna trees to grow faster than those of forest species, contrary to expectations, nor was whole-plant mortality higher in forest than in savanna. This contrasts with observations of high rates of postburn mortality in many other tropical forests. The low tree mortality in these transitional forests suggests that the dynamic of these natural savanna-forest boundaries is fundamentally different from that of forest boundaries originating from deforestation in the humid tropics. The forests studied here appear to be much more resilient to occasional incursion of fire from the savanna, despite being unable to invade frequently burned savanna. The thin bark of forest species makes them particularly susceptible to the \"fire trap,\" whereby repeated topkill of small trees prevents recruitment into adult size classes. Rapid growth will be particularly important for forest species to escape the fire trap, so we predict that, where fire is frequent, forests should be restricted to high-resource sites. Here, Mg²⁺ and Ca²⁺ concentrations had particularly strong effects on postburn growth rates, suggesting that these elements may most strongly limit the distribution of forest in these fire-prone savannas.

This work details the structure and composition of the woody plant community of a gallery forest located in the La Silla River, between Monterrey and Guadalupe urban areas in Nuevo León, Mexico. For the analysis, the woody vegetation was categorized into upper and lower strata. The upper stratum maximum height was 38 m, and the canopy cover was 100%. The canopy consisted of 22 species from 16 families, of which seven species represented 82.3% of the importance value index (IV); Taxodium huegelii had the highest IV (34.32%). The lower stratum maximum height was 2.5 m, and the cover was 48%. Thirteen species from 10 families were identified, five of which reached 81.3% of the IV; Ricinus communis had the highest IV (23.42%). The plant community diversity was 3.8 and 2.29, based on Margalef and Shannon indices, respectively. As one finding in the present study, it can be stated that the main threat is the presence of widely distributed exotic species such as Ricinus communis and Leucaena leucocephala, with high importance values. However, the presence of a well-established tree stratum, as well as the presence of species typical of the gallery forest, suggest a good state of conservation of this gallery forest. The present results highlight the importance of studying the composition, structure, and diversity, taking into consideration the flora of floristic provinces, as an analytic strategy for the diagnosis of riparian lentic community health.

The Cerrado has high plant and vertebrate diversity and is an important biome for conserving species and provisioning ecosystem services. Volume equations in this biome are scarce because of their size and physiognomic diversity. This study was conducted to develop specific volumetric models for the phytophysiognomies Gallery Forest, Dry Forest, Forest Savannah, and Savannah Woodland, a generic model and a model for Cerrado forest formation. Twelve 10 m × 10 m (100 m²) (National Forest Inventory) plots were used for each phytophysiognomy at different sites (regions) of the Federal District (FD) where trees had a diameter at breast height (DBH; 1.30 m) ≥5 cm in forest formations and a diameter at base height (Db; 0.30 m) ≥5 cm in savanna formations. Their diameters and heights were measured, they were cut and cubed, and the volume of each tree was obtained according to the Smalian methodology. Linear and nonlinear models were adjusted. Criteria for the selection of models were determined using correlation coefficients, the standard error of the estimates, and a graphical analysis of the residues. They were later validated by the chi-square test. The resultant models indicated that fit by specific phytophysiognomy was ideal; however, the generic and forest formation models exhibited similar performance to specific models and could be used in extensive areas of the Cerrado, where they represent a high potential for generalization. To further increase our understanding, similar research is recommended for the development of specific and generic models of the total volume in Cerrado areas.

The juniper (Taxodium mucronatum Ten. of the Cupressaceae family) is a long-lived species that forms gallery forests. Dozens of dead junipers > 100 years old have been identified in the San Pedro Mezquital watershed in Durango, Mexico. This work determines the causes of death of these specimens. The work was carried out in the field and in the laboratory, where in the former the surface of the damaged trees was identified, together with the changes observed in the watercourses. In the latter, sabino seedlings were transported to the work center and exposed for 7 days in containers with gravel to five types of wastewater generated in the region. With the above, the conditions experienced by the adult trees in the field were studied, as well as the sensitivity of the young specimens to the types of water quality, and the differences were validated with ANOVA tests. Five sites with dead junipers were found, ranging in size from 0.5 to 4 ha, with ages between 200 and 400 years. It was found that during the dry season, water is diverted to irrigated areas, leaving some areas without water for several months. The shoots survived in most of the water qualities, except the one with high salinity (3.34 mS/cm). It is concluded that the lack of water in the rivers had a stronger influence than the water quality and is the probable cause of the death of the sabino.

Studies on animal camouflage offer some of the most compelling examples of microevolution via natural selection. If selection favouring camouflage is indeed widespread, the colour of the vegetation might act as a filter by removing non-camouflaged species. Consequently, the colouration and diversity of colours of animal communities may follow similar patterns to those of the vegetation. During wet and dry periods of the year, we extracted physical descriptors of chromatic and achromatic dimensions of arthropods and vegetation items collected from neighbouring vegetational types: a seasonal savanna (cerrado) and an evergreen gallery forest. Here, colouration can be understood as a trait, and we seek to describe and comprehend patterns at the community-level. The colours of the arthropods in the gallery forest were similar to the vegetation and followed the relatively small changes in this vegetational type. This could indicate the potential for the studied animals to be, overall, camouflaged against the vegetation. Conversely, the cerrado vegetation during the dry season was dominated by dry grasses and a homogeneous beige tint. After the dry season, the vegetation shifted to a bimodal distribution, dominated by the green of new leaves. The diversity of arthropod colours changed, to some extent, in concert with the vegetation. However, the peak location of arthropod colouration did not follow the vegetation. The Cerrado colour variation could act as one of the filters in these arthropod communities.

1. Fire is important in the dynamics of savanna-forest boundaries, often maintaining a balance between forest advance and retreat. 2. We performed a comparative ecological study to understand how savanna and forest species differ in traits related to fire tolerance. We compared bark thickness, root and stem carbohydrates, and height of reproductive individuals within 10 congeneric pairs, each containing one savanna and one forest species. 3. Bark thickness of savanna species averaged nearly three times that of forest species, thereby reducing the risk of stem death during fire. The allometric relationship between bark thickness and stem diameter differed between these two tree types, with forest species tending to have a larger allometric coefficient. 4. The height of reproductive individuals of forest species averaged twice that of congeneric savanna species. This should increase the time necessary for forest species to reach reproductive size, thereby reducing their capacity to reach maturity in the time between consecutive fires. 5. There was no difference in total non-structural carbohydrate content of stems or roots between savanna and forest species, though greater allocation to total root biomass by savanna species probably confers greater capacity to resprout following fire. 6. These differences in fire-related traits may largely explain the greater capacity of savanna species to persist in the savanna environment.