Neotropical Dry Forests Research Articles

Bioacoustics as an Important Complementary Tool in Bat Inventories in the Caatinga Drylands of Brazil

The Caatinga of northeastern Brazil is considered one of the most species-rich dry forests in the World. The area may harbor nearly 100 species of bats and correctly accessing such richness is a scientific challenge. Bat inventories have been usually based solely on mist netting, which is biased in drylands, where nearly half of the species are open-space insectivores flying high above nets, or species able to better detect and avoid nets. Here, we used mist netting and acoustic inventories in three protected areas in the Caatinga, so species richness could be compared based on both techniques. After an effort of 1,010 net.hours and 1,941 minutes of recordings, we recorded 29 species with nets, 27 on recordings, and five with both techniques. Acoustic sampling resulted in more species in 44% of nights sampled, and two nights had species recorded solely based on their echolocation calls. Species recording differed between techniques, and the driest the site, the lowest the captures with nets, while records based on echolocation remained constant. Based on species estimators, netting achieved 51% of the expected richness, acoustics achieved 87%, and both techniques achieved 70%. Using acoustic sampling we recorded ca. of 42% of the insectivorous species expected for the entire Caatinga and 20% solely on netting. Moreover, in our study bioacoustics indicated that some species were more abundant and widespread than expected. Therefore, studies using solely netting or bioacoustics will produce different results and, in Neotropical dry forests like Caatinga, for a more complete scenario on the local bat species richness a combination of both techniques is essential.

Neocapparis: Generic Status and New Name for Capparidastrum Subgenus Pachycarpum (Capparaceae)

Abstract. Based on morphological characters and recent molecular evidence, Capparidastrum subgenus Pachycarpum (Capparaceae) is raised to generic status. As Pachycarpus is a previous and valid generic name of Apocynaceae (Asclepiadoideae), Neocapparis is here proposed as a new generic name for Capparidastrum subgenus Pachycarpum. Two new combinations for species previously placed in Capparidastrum are presented here: Neocapparis pachaca and Neocapparis quina. The new genus is restricted to Neotropical dry forests, ranging from Mexico to northern Colombia and Venezuela and disjunct to western Ecuador and Peru. Illustrations of species and full citation of collections are provided.

Caryophyllales are the main hosts of a unique set of ectomycorrhizal fungi in a Neotropical dry forest.

The ectomycorrhizal symbiosis was long thought to be restricted to temperate forests. However, as tropical forests have been explored, it has become clear that these habitats host unique ectomycorrhizal (ECM) fungi. We have been exploring tropical dry forests (TDF), which are endangered terrestrial ecosystems and hotspots of endemism. Since Fabaceae is the main plant family in this environment, we hypothesized that trees in this lineage would be the main ECM hosts. We sequenced the ITS rDNA region from fungi and both rbcL and trnL cpDNA from plants to identify both symbiotic partners from root tips. The systematic position of each symbiont was confirmed by Bayesian phylogenetic inference. We identified 20 plant species belonging to 10 families that hosted 19 unique ECM fungal species from 5 lineages. Most ECM fungi were associated with Caryophyllales, not with Fabaceae. Achatocarpus and Guapira, the main hosts, are scattered throughout the forest and are not in monodominant patches. The low ECM fungal diversity can be explained by the low density of host plants and their high specificity. Our results indicate that Caryophyllales is an important order of tropical ECM hosts with at least four independent evolutionary lineages that have evolved the ability to form ectomycorrhizae.

Seasonality in abundance and detection bias of birds in a tropical dry forest in north-eastern South America

Abstract:Seasonal fluctuations in bird abundance are expected in semi-arid environments, but estimates may be biased if detectability is not considered. In a tropical dry forest in north-eastern Brazil, we evaluated whether bird abundance is highly seasonal, and associated with time-specific variability in detectability. We mark-recaptured birds with mist nets over three field visits (3487 records from 75 species), and used closed-capture models to estimate detectability and abundance in birds divided into three groups (all, residents, insectivores). In the two dry periods, the best models resulted in capture estimates at least three times larger than recapture, and both estimates were twice that of when rains occurred on the day preceding sampling. Abundance varied between dry and wet periods from 4.0 (from 115 ± 34 to 479 ± 144) to 13 times (183 ± 8 to 2463 ± 351). Estimates were 1.5–3.2 times greater in the dry period when behavioural responses of birds were excluded from capture-recapture models. Meanwhile, in the wet period the relative abundance was between 33–76% smaller than best-fit models estimated. This study found variation in avian abundance greater than that observed in other Neotropical dry forests, and indicates that biases may be common when not including detectability.

Jevons paradox and the loss of natural habitat in the Argentinean Chaco: The impact of the indigenous communities’ land titling and the Forest Law in the province of Salta

The Chaco Salteño in Argentina is part of the Dry Chaco ecoregion, the largest neotropical dry forest in the world, and represents an important hotspot for deforestation and natural habitat loss due to agricultural expansion. The purpose of this article is: i) to assess systematically the role of agricultural expansion, intensification and demographics on the loss of natural habitat and ii) to understand how institutional factors contribute to direct the impact of agricultural intensification towards land sparing or Jevons paradox. We use multivariate statistical methods to assess the effect of important institutional changes, including the promulgation of the Forest Law in the Province of Salta and the titling of communal lands to Indigenous Peoples (IPs), on the loss of natural forests, shrublands and grasslands in the Chaco Salteño. Our results show that the approval of the Forest Law in Salta has been ineffective at slowing down the loss of natural habitat and is associated with the emergence of Jevons paradox via the increase in agricultural productivity. Moreover, this new institutional context appears to have increased the pressures on IPs land and encouraged preventive clearing on these lands. Finally, we detect the decreasing importance of livestock heads as drivers of natural habitat loss.

White‐tailed deer as the last megafauna dispersing seeds in Neotropical dry forests: the role of fruit and seed traits

AbstractEndozoochory is a prominent form of seed dispersal in tropical dry forests. Most extant megafauna that perform such seed dispersal are ungulates, which can also be seed predators. White‐tailed deer (Odocoileus virginianus) is one of the last extant megafauna of Neotropical dry forests, but whether it serves as a legitimate seed disperser is poorly understood. We studied seed dispersal patterns and germination after white‐tailed deer gut passage in a tropical dry forest in southwest Ecuador. Over 23 mo, we recorded ca 2000 seeds of 11 species in 385 fecal samples. Most seeds belonged to four species of Fabaceae: Chloroleucon mangense, Senna mollissima, Piptadenia flava, and Caesalpinia glabrata. Seeds from eight of the 11 species dispersed by white‐tailed deer germinated under controlled conditions. Ingestion did not affect germination of C. mangense and S. mollissima, whereas C. glabrata showed reduced germination. Nevertheless, the removal of fruit pulp resulting from ingestion by white‐tailed deer could have a deinhibition effect on germination due to seed release. Thus, white‐tailed deer play an important role as legitimate seed dispersers of woody species formerly considered autochorous. Our results suggest that more research is needed to fully understand the ecological and evolutionary effects of the remaining extant megafauna on plant regeneration dynamics in the dry Neotropics.

Carbon Accumulation in Neotropical Dry Secondary Forests: The Roles of Forest Age and Tree Dominance and Diversity

Tropical secondary forests are important sinks for atmospheric carbon, yet C uptake and accumulation rates are highly uncertain, and the mechanisms poorly understood. We evaluated the recovery of C stocks in four pools (aboveground biomass, litter, roots and topsoil) during dry forest regrowth by combining a space for time replacement (that is, a chronosequence) with a repeated measurements approach (that is, a resampling). We fit nonlinear models to chronosequence data to test whether forest age could explain differences in C stocks across sites, and to changes in aboveground biomass calculated from resampling over two 3-year periods, to test the predictive potential of forest age. We combined data from both approaches into structural equation models (SEM) to assess forest age and tree community attributes (diversity and dominance) as drivers of C stocks and changes in aboveground biomass. Forest age explained differences across sites in C stocks for aboveground biomass, litter and live roots, but not for the remaining pools. Observed C stock changes in aboveground biomass were poorly predicted by forest age. SEM revealed that aboveground biomass C was consistently and positively related to forest age and to the community weighted mean of maximum tree height (H max CWM), but not to tree diversity. Observed C stock changes were related only to H max CWM, although not consistently across the two 3-year periods. Our results highlight that the chronosequence approach can yield reasonable insights into long-term C accumulation trends, but erroneous estimates of C change over specific time periods. They also show that, in addition to age, dominance by tall statured species, but not tree species diversity, plays a significant role in C accumulation.

Diversity and Structure of Social Wasps Community (Hymenoptera: Vespidae, Polistinae) in Neotropical Dry Forest

In the northeastern part of Brazil, located 90% within the semi-arid region of the country, we can find areas that present quite peculiar characteristics, amongst these the Caatinga. This biome is characterized by the floristic composition formed of dry forest and in this semi-arid environment there is an increase in the supply of resources during the rainy season. This is a region lacking in research, particularly in the State of Paraíba, where no survey studies of social wasp were carried out yet. Social wasps are an important predator of plagues species. The objective of this study was to conduct a survey of the community of social wasps (Polistinae species) that inhabit in the neotropical dry forest of Paraiba, in the municipalities of Sumé and Prata, and to compare the richness and abundance of wasps located in areas of Caatinga with those inhabiting areas intercropping plantation with organic farming. The present study sampled 10 Polistinae species distributed in six genera. Two new species were registered for the state. The comparison between the community of social wasps of the Caatinga There was not statistical difference in the richness and abundance between the natural vegetation and organic intercropping. This means that agroecosystem attracted community of Polistinae, promoting the maintenance of social wasps in anthropic environmental and favoring the biological control.

Pleistocene climate changes shaped the population structure of Partamona seridoensis (Apidae, Meliponini), an endemic stingless bee from the Neotropical dry forest.

Partamona seridoensis is an endemic stingless bee from the Caatinga, a Neotropical dry forest in northeastern Brazil. Like other stingless bees, this species plays an important ecological role as a pollinator. The aim of the present study was to investigate the genetic structure and evolutionary history of P. seridoensis across its current geographic range. Workers from 84 nests from 17 localities were analyzed for COI and Cytb genic regions. The population structure tests (Bayesian phylogenetic inference, AMOVA and haplotype network) consistently characterized two haplogroups (northwestern and eastern), with little gene flow between them, generating a high differentiation between them as well as among the populations within each haplogroup. The Mantel test revealed no isolation by distance. No evidence of a potential geographic barrier in the present that could explain the diversification between the P. seridoensis haplogroups was found. However, Pleistocene climatic changes may explain this differentiation, since the initial time for the P. seridoensis lineages diversification took place during the mid-Pleistocene, specifically the interglacial period, when the biota is presumed to have been more associated with dry conditions and had more restricted, fragmented geographical distribution. This event may have driven diversification by isolating the two haplogroups. Otherwise, the climatic changes in the late Pleistocene must not have drastically affected the population dynamics of P. seridoensis, since the Bayesian Skyline Plot did not reveal any substantial fluctuation in effective population size in either haplogroup. Considering its importance and the fact that it is an endemic bee from a very threatened Neotropical dry forest, the results herein could be useful to the development of conservation strategies for P. seridoensis.

Patterns and correlates of plant diversity differ between common and rare species in a neotropical dry forest

Determining which factors affect species richness is important for conservation theory and practice. However, richness of common and rare species may be affected by different factors. We use an extensive inventory of woody plants from a tropical dry forest landscape in Yucatan, Mexico to assess the unique effects of environmental variables, spatial dependence of sampling sites, forest stand age and the combined effect of all groups of variables on species richness of woody plants with different levels of rarity (common, intermediate, rare, very rare)—according to their abundance, habitat specificity and spatial distribution range in the landscape. Analyzing separately common species and those with different levels of rarity uncovered contrasting patterns and correlates of species richness that were not apparent when focusing on all woody plants. In particular, richness of common and intermediate species was influenced mainly by environmental factors, whereas richness of very rare species was affected mostly by the unique effect of spatial dependence of sampling sites, suggesting a main role of environmental filtering and dispersal limitation, respectively. However, common and very rare species also responded inversely to some landscape metrics, revealing contrasting environmental preferences of these groups of species. These contrasting results suggest different underlying mechanisms and the need for very different conservation strategies. Therefore, basic and applied research on tropical forest biodiversity should consider separately species with different levels of rarity, focusing on which factors control variation in each level, and paying special attention to very rare species, generally the most specious and vulnerable to local extinction.

Importance of riparian habitat for frugivorous bats in a tropical dry forest in western Mexico

Abstract:Riparian forests (RF) provide shelter, feeding resources and commuting areas and are fundamental for local fauna during long drought periods in tropical dry forests. Nevertheless, information regarding vertebrate ecology in tropical RF is scarce. The studies of bats in riparian habitats have been mostly focused on insectivorous assemblages in non-tropical regions. We contrasted the occurrence of frugivorous bats between RF and upland dry forest (UDF) in a Neotropical dry forest region and evaluated how vegetation structure modulates frugivorous bat presence and abundance. We sampled bat ensembles and vegetation structure in three UDF and three RF sites in Jalisco, Mexico. Bat ensembles and populations were analysed with generalized linear models, including as independent factors: (1) habitat and (2) vegetation attributes. In 72 nights we captured 840 bats belonging to seven species. No effect of habitat type or vegetation structure on species richness was found, but habitat type did affect bat species composition and abundance. Moreover, vegetation structural traits affected frugivorous bat abundance. Frugivore abundance was higher in RF than in UDF probably because RF provides greater resources and more roosting sites. Riparian forests also present more canopy cover and accessible flight spaces. Our results support the importance of RF for frugivorous bats in terms of abundance and composition. Additionally, the lack of differences in species richness between UDF and RF highlights the importance of both habitats for maintaining frugivorous bats, as well as the related ecosystem processes and services in tropical dry forest landscapes.

Abundance and diversity of lianas in a Neotropical dry forest: the influence of soil moisture

Background and aims – Based on data across tropical forests, a leading hypothesis posits that lianas are better competitors than trees under water shortage. Evaluating this hypothesis at a local scale may provide insights into its generality. We tested whether the abundance of lianas –relative to trees– decreases with soil moisture in a Neotropical dry forest. We also evaluated the influence of water availability on liana diversity.Methods – Lianas (≥ 1 cm diameter) and trees (≥ 1.5 m height) were counted and identified, and soil moisture was measured, in twenty 10 × 10 m plots at different distances to water sources. Linear regressions assessed the relationships between water availability and relative abundance and diversity of lianas.Key Results – We found a significant an d positive relationship between the relative abundance of lianas and water availability. Liana density ranged from 21 to 77 individuals per plot. Soil moisture did not influence liana species richness (S) or Fisher's α. Eighteen liana species were recorded , from ten families.Conclusions – Our results show that, in contrast with geographic and regional patterns, relative abundance and diversity of lianas at a local scale are not favoured by water shortage. This suggests that different mechanisms may prevail in the liana-tree interaction across water availability gradients.

Tree responses to moisture fluctuations in a neotropical dry forest as potential climate change indicators

Trees in tropical dry forests (TDFs) have manifold drought coping strategies including succulence of different plant organs, wood anatomical traits and leaf phenology. As water availability to plants is the limiting factor for physiological activity, changes in precipitation patterns are assumed to have strong influences on tree phenology, growth and water turnover. Our objectives were to assess patterns in leaf phenology, radial stem circumference changes and sap flux responses to fluctuating moisture regimes of selected species. Based on these findings we evaluated the potential suitability as indicator species for climate change effects. The study was implemented at different elevational positions in a submontane dry forest of southern Ecuador. Annual rainfall is 600mm with an eight months dry period; moisture availability slightly increases with altitude because of moist air coming from the Pacific. At three altitudes, we studied the tree species Ceiba trichistandra (leaf deciduous, stem succulent), Eriotheca ruizii (leaf deciduous, root succulent) and Erythrina velutina (leaf deciduous). Reversible stem swelling and shrinking was observed for all three species during the whole study period and at all positions at the altitudinal gradient. However, it was most pronounced and sensitive in the stem succulent C. trichistandra and at the lowest (driest) position. C. trichistandra flushed leaves at dry season intermittent rain events, and from dry to wet season leaf out was earlier, and in this period sap flux was high while stem circumference decreased. Length of the leaved periods of all species increased with altitude. Thus, clear differences among species, topographic positions, radial growth and tree water use patterns are revealed; especially C. trichistandra responded very sensitive to fluctuating moisture regimes with leaf phenology, sap flux and stem diameter variations, and can be regarded as a sensitive indicator for assessing climatic variations.

Assessing ecosystem services in Neotropical dry forests: a systematic review

SUMMARYThere is an increasing consensus on the importance of understanding ecosystem service (ES) provision in order to facilitate decision making and the sustainable management of Neotropical dry forests (NTDFs), yet research on the ESs provided by NTDFs is limited. We identified the main existing gaps and trends in the quantification of provisioning, regulating and supporting ESs in NTDFs. Systematic web-based searches showed that research has been increasing in recent decades in NTDFs, supporting greater ES knowledge and assessment. Carbon storage and biodiversity are the main subjects under study, while ESs relating to water and soil lack investigation. The most common approaches for assessing ES were fauna and plant inventories, carbon dynamics and ecological processes.

Diversity in neotropical dry forests

Forest Ecology Dry forests in the American tropics are not as extensive as rain forests and are more severely threatened by human activity. The DRYFLOR network compiled a floristic inventory of the entire neotropical dry forest biome and used this database of nearly 5000 woody species to analyze the geographical distribution of plant diversity that it hosts. Large variation in floristic composition between different sites and regions implies that effective conservation of dry forest plant diversity will require the protection of numerous priority areas across neotropical nations. Science , this issue p. [1383][1] [1]: /lookup/doi/10.1126/science.aaf5080

Plant diversity patterns in neotropical dry forests and their conservation implications.

Seasonally dry tropical forests are distributed across Latin America and the Caribbean and are highly threatened, with less than 10% of their original extent remaining in many countries. Using 835 inventories covering 4660 species of woody plants, we show marked floristic turnover among inventories and regions, which may be higher than in other neotropical biomes, such as savanna. Such high floristic turnover indicates that numerous conservation areas across many countries will be needed to protect the full diversity of tropical dry forests. Our results provide a scientific framework within which national decision-makers can contextualize the floristic significance of their dry forest at a regional and continental scale.

Natural vegetation cover in the landscape and edge effects: differential responses of insect orders in a fragmented forest.

Human activities have led to global simplification of ecosystems, among which Neotropical dry forests are some of the most threatened. Habitat loss as well as edge effects may affect insect communities. Here, we analyzed insects sampled with pan traps in 9 landscapes (at 5 scales, in 100-500 m diameter circles) comprising cultivated fields and Chaco Serrano forests, at overall community and taxonomic order level. In total 7043 specimens and 456 species of hexapods were captured, with abundance and richness being directly related to forest cover at 500 m and higher at edges in comparison with forest interior. Community composition also varied with forest cover and edge/interior location. Different responses were detected among the 8 dominant orders. Collembola, Hemiptera, and Orthoptera richness and/or abundance were positively related to forest cover at the larger scale, while Thysanoptera abundance increased with forest cover only at the edge. Hymenoptera abundance and richness were negatively related to forest cover at 100 m. Coleoptera, Diptera, and Hymenoptera were more diverse and abundant at the forest edge. The generally negative influence of forest loss on insect communities could have functional consequences for both natural and cultivated systems, and highlights the relevance of forest conservation. Higher diversity at the edges could result from the simultaneous presence of forest and matrix species, although "resource mapping" might be involved for orders that were richer and more abundant at edges. Adjacent crops could benefit from forest proximity since natural enemies and pollinators are well represented in the orders showing positive edge effects.

Demographic Drivers of Aboveground Biomass Dynamics During Secondary Succession in Neotropical Dry and Wet Forests

The magnitude of the carbon sink in second-growth forests is expected to vary with successional biomass dynamics resulting from tree growth, recruitment, and mortality, and with the effects of climate on these dynamics. We compare aboveground biomass dynamics of dry and wet Neotropical forests, based on monitoring data gathered over 3–16 years in forests covering the first 25 years of succession. We estimated standing biomass, annual biomass change, and contributions of tree growth, recruitment, and mortality. We also evaluated tree species’ contributions to biomass dynamics. Absolute rates of biomass change were lower in dry forests, 2.3 and 1.9 Mg ha−1 y−1, after 5–15 and 15–25 years after abandonment, respectively, than in wet forests, with 4.7 and 6.1 Mg ha−1 y−1, in the same age classes. Biomass change was largely driven by tree growth, accounting for at least 48% of biomass change across forest types and age classes. Mortality also contributed strongly to biomass change in wet forests of 5–15 years, whereas its contribution became important later in succession in dry forests. Biomass dynamics tended to be dominated by fewer species in early-successional dry than wet forests, but dominance was strong in both forest types. Overall, our results indicate that biomass dynamics during succession are faster in Neotropical wet than dry forests, with high tree mortality earlier in succession in the wet forests. Long-term monitoring of second-growth tropical forest plots is crucial for improving estimates of annual biomass change, and for enhancing understanding of the underlying mechanisms and demographic drivers.

Dendrocronología en bosques neotropicales secos: métodos, avances y aplicaciones

Medivelso, H.A., Camarero, J.J., Gutierrez, E. 2016. Dendrochronology in Neotropical dry forests: methods, advances and applications. Ecosistemas 25(2): 66-75. Doi.: 10.7818/ECOS.2016.25-2.08 Neotropical dry forests (TDFs) are characterized by a dry season which allows some tree species forming annual rings. In TDFs the study of tree rings using dendrochronology involves their identification, dating and measurement. In this way, we gain a retrospective view of tree growth at a temporal scale in agreement with tree longevity. Having a good knowledge of wood anatomy and phenology is necessary to perform dendrochronological studies in TDFs. For instance, most angiosperm tree species which have been studied in TDFs from a dendrochronological point of view present ring boundaries characterized by a band of marginal parenchyma. The information recorded in tree rings has allowed (i) quantifying how growth of TDF trees responds to climatic variables (mainly precipitation) and determining if it is related to large scale atmospheric patterns (El Nino-Southern Oscillation) (dendroclimatology); (ii) reconstructing the dynamics of many TDFs (dendroecology) by improving our knowledge of tree ages and growth rates. Dendroecology will provide forest managers with objective tools to quantify and forecast cutting cycles, making the management of TDFs more sustainable.

Rasgos morfológicos regenerativos en una comunidad de especies leñosas en un bosque seco tropical tumbesino

The study of functional morphological traits enables us to know fundamental aspects of the dynamics of plant communities in local and global habitats. Regenerative morphological traits play an important role in defining plant history and ecological behavior. Seed and fruit characteristics determine to a large extent the patterns for dispersal, germination, establishment and seedling recruitment a given species exhibits on its natural habitat. Despite their prominent role, seed and fruit traits have been poorly studied at the community level of woody plant species in neo-tropical dry forests. In the present study we aimed at i) evaluate the functional role of morphological traits of seeds, fruits and embryo in woody plant species; ii) determine which are the morphological patterns present in seeds collected from the community of woody species that occur in neo-tropical dry forests; and iii) compare woody plant species seed mass values comparatively between neo-tropical dry and tropical forests. To do so, mature seeds were collected from 79 plant species that occur in the Tumbesian forest of Southwest Ecuador. The studied species included the 42 and 37 most representative tree and shrubbery species of the Tumbesian forest respectively. A total of 18 morphological traits (seven quantitative and 11 qualitative) were measured and evaluated in the seeds, fruits and embryos of the selected species, and we compared the seeds mass with other forest types. Our results showed a huge heterogeneity among traits values in the studied species. Seed mass, volume and number were the traits that vary the most at the community level, i.e. seed length ranged from 1.3 to 39 mm, and seed width from 0.6 to 25 mm. Only six embryo types were found among the 79 plant species. In 40 % of the cases, fully developed inverted embryos with large and thick cotyledons to store considerable amount of nutrients were recorded. We concluded that highly variable and functionally complementary morphological traits occur among the studied woody plants of the Tumbesian dry forest. The latter favors a plethora of behavioral mechanisms to coexist among woody species of the dry forest in response to the environmental stress that is typical of arid areas.