The availability and quality of resources for herbivores in tropical dry forests (TDFs) vary in time and space, affecting herbivore guilds differently across spatial scales (both horizontally and vertically), with consequences to the distribution of leaf damage in these forests. We attempted to elucidate the distribution patterns of herbivorous insect guilds and leaf damage throughout the secondary succession and vertical stratification along the rainy season in a Brazilian TDF. With the advance of the succession, a greater richness and abundance of herbivorous insects were found, resulting in higher leaf damage in intermediate and late stages. This pattern, however, was not observed for the frequency of leaf miners. At a smaller spatial scale, the host tree height positively affected the richness and abundance of insects. The higher leaf damage was found in canopy, which also harbored a greater richness and abundance of chewing herbivores compared to the understory at both the beginning and the end of the rainy season. Although for sap-sucking insects, this was only true at the beginning of the season. We detected a decrease in insect richness and abundance at the end of the rainy season, probably due to a synchronization of insect activity with the availability of young, highly nutritious plant tissues. These results are consistent with other studies that found a general trend of increasing richness and abundance of herbivorous insects and leaf damage throughout the secondary succession (early to late stages) and between vertical strata (understory to canopy), suggesting that forest complexity positively affects herbivores.Abstract in Portuguese is available in the online version of this article.

No abstract

Clearing tropical vegetation impacts biodiversity, the provision of ecosystem services, and thus ultimately human welfare. We quantified changes in land cover from 2000 to 2015 across the Cerrado biome of northern Minas Gerais state, Brazil. We assessed the potential biophysical and socio-economic drivers of the loss of Cerrado, natural regeneration and net cover change at the municipality level. Further, we evaluated correlations between these land change variables and indicators of human welfare. We detected extensive land-cover changes in the study area, with the conversion of 23 446 km 2 and the natural regeneration of 13 926 km 2 , resulting in a net loss of 9520 km 2 . The annual net loss (−1.2% per year) of the cover of Cerrado is higher than that reported for the whole biome in similar periods. We argue that environmental and economic variables interact to underpin rates of conversion of Cerrado, most severely affecting more humid Cerrado lowlands. While rates of Cerrado regeneration are important for conservation strategies of the remaining biome, their integrity must be investigated given the likelihood of encroachment. Given the high frequency of land abandonment in tropical regions, secondary vegetation is fundamental to maintain biodiversity and ecosystem services. Finally, the impacts of Cerrado conversion on human welfare likely vary from local to regional scales, making it difficult to elaborate land-use policies based solely on socio-economic indicators. This article is part of the themed issue ‘Tropical grassy biomes: linking ecology, human use and conservation’.

No abstract

Plant development is the main factor that determines the insect-ontogeny interaction, since it leads to variations in resource quality and availability. The aim of this study was to test the hypothesis that plant development and varying tannin concentration leads to changes in species richness, abundance and composition of ants, free-feeding herbivores and galling insects associated with Copaifera langsdorffii (Fabaceae). The plant ontogeny and tannin concentration effects on insects were tested on 60 individuals with height varying from 0.9 to 11.0 m. A positive correlation was observed for tree height and species richness and abundance of ants, free-feeding and galling insects. In contrast, we did not find a significant relation between leaf tannin concentration and plant height, or richness and abundance of the different insect guilds. The assemblage of ants (composition of species) did not change between saplings and adults of C. langsdorffii. However, the assemblage of free-feeding herbivores and galling insects varied between the two development stages studied. The present study reveals an ontogenetic succession pattern for herbivore insects along the C. langsdorffii growth, probably due to both indirect and direct benefits from the host plant architecture and quality. Those plants with more complex architectures should support a wider diversity of insects, since they present higher number of sites for egg laying, housing, feeding and better environmental conditions. This is the first work to investigate the host plant ontogeny effect on insects in Cerrado ''Savanna'' vegetation. The pattern described, along with other previous studies, suggests a vast occurrence of ontogenetic succession in tropical areas.

Background: This study aimed to determine the influence of soil traits, vegetation structure and climate on litterfall dynamics along a successional gradient in a tropical dry forest (TDF) in southeastern Brazil. We used a chronosequence design consisting of three successional stages (early, intermediate, and old-growth) defined based on forest age and vertical and horizontal structures. Methods: Litterfall was recorded monthly for three years in 12 plots of 50 × 20 m (four plots per stage) where vegetation parameters (species richness, basal area, density and height for trees with diameter at breast height ≥ 5 cm) and soil chemical and physical traits were previously obtained. We placed eight 0.5-m 2 litter traps in each plot, totalling 96 traps. Samples were sorted into leaves, twigs, reproductive parts, and debris. Results: Litterfall mass was composed mainly of leaves and varied slightly among years (4 to 4.5 Mg•ha − 1), within the range observed for other TDFs. Annual litterfall mass was higher at the old-growth forest than at the early and intermediate forest stages and this successional pattern was driven by vegetation characteristics (forest structural parameters and plant functional groups) and soil traits related to water-holding capacity. Litter amount in the intermediate stage was lower than expected for its forest structure (and similar to the early stage), possibly because its higher soil clay content increased the water holding capacity and leaf retention during the dry season. Seasonal variations in monthly litterfall were strongly driven by forest deciduousness and affected by climatic factors related to water availability. This pattern was consistent across the successional gradient, although differences for each litterfall component were observed. Conclusions: Our results suggest that litter production in the studied TDF is influenced by multiple factors along succession, such as above-ground biomass and the degree of leaf retention mediated by soil water-holding capacity. Further studies on community phenological patterns can allow a better understanding of successional changes on litterfall and how fast this fundamental function recovers in secondary forests.

This study determined the temporal patterns of herbivory on Handroanthus ochraceus (Cham.) Mattos (Bignoniaceae) along a successional gradient in a seasonally dry tropical forest (SDTF) in southeastern Brazil. We assessed the diversity of free-feeding herbivore insects (sapsuckers and leaf-chewers), leaf herbivory rates, leaf nitrogen content, phenolic compounds, and spider abundance through the rainy season in three different successional stages (early, intermediate, and late). Sampling was conducted in December, at the beginning of the rainy season (with fully expanded young leaves), February (mid-aged leaves), and April, at the end of rainy season (old leaves). Fifteen reproductive trees of H. ochraceus were sampled per successional stage in each month of sampling. Herbivore diversity was highest in the early stage of succession, but herbivory rates were highest in the intermediate and late stages. This result was probably related to differences in herbivore community composition and leaf quality across successional stages. The highest herbivore abundance was found in April in the early successional stage. In addition, we found low levels of herbivory in the intermediate and late successional stages in the second half of the rainy season. For each successional stage, leaf nitrogen content decreased through the rainy season, whereas the concentration of phenolic compounds increased. For the intermediate and late successional stages, the temporal changes that took place as the rainy season progressed corroborated the following hypotheses postulated for SDTFs: (1) both the abundance of chewing insects and herbivory rates decreased, (2) the abundance of natural enemies (i.e., spiders) increased, and (3) leaf quality decreased. These results suggest that the described herbivory patterns are robust for advanced successional stages (intermediate and late) of the SDTFs, but may not apply to early successional stages of these forests.

No abstract