Neotropical Forests Research Articles

Soil resistance and recovery during neotropical forest succession.

The recovery of soil conditions is crucial for successful ecosystem restoration and, hence, for achieving the goals of the UN Decade on Ecosystem Restoration. Here, we assess how soils resist forest conversion and agricultural land use, and how soils recover during subsequent tropical forest succession on abandoned agricultural fields. Our overarching question is how soil resistance and recovery depend on local conditions such as climate, soil type and land-use history. For 300 plots in 21 sites across the Neotropics, we used a chronosequence approach in which we sampled soils from two depths in old-growth forests, agricultural fields (i.e. crop fields and pastures), and secondary forests that differ in age (1-95 years) since abandonment. We measured six soil properties using a standardized sampling design and laboratory analyses. Soil resistance strongly depended on local conditions. Croplands and sites on high-activity clay (i.e. high fertility) show strong increases in bulk density and decreases in pH, carbon (C) and nitrogen (N) during deforestation and subsequent agricultural use. Resistance is lower in such sites probably because of a sharp decline in fine root biomass in croplands in the upper soil layers, and a decline in litter input from formerly productive old-growth forest (on high-activity clays). Soil recovery also strongly depended on local conditions. During forest succession, high-activity clays and croplands decreased most strongly in bulk density and increased in C and N, possibly because of strongly compacted soils with low C and N after cropland abandonment, and because of rapid vegetation recovery in high-activity clays leading to greater fine root growth and litter input. Furthermore, sites at low precipitation decreased in pH, whereas sites at high precipitation increased in N and decreased in C : N ratio. Extractable phosphorus (P) did not recover during succession, suggesting increased P limitation as forests age. These results indicate that no single solution exists for effective soil restoration and that local site conditions should determine the restoration strategies. This article is part of the theme issue 'Understanding forest landscape restoration: reinforcing scientific foundations for the UN Decade on Ecosystem Restoration'.

Prey tracking and predator avoidance in a Neotropical moist forest: a camera-trapping approach.

Whether prey species avoid predators and predator species track prey is a poorly understood aspect of predator-prey interactions, given measuring prey tracking by predators and predator avoidance by prey is challenging. A common approach to study these interactions among mammals in field situations is to monitor the spatial proximity of animals at fixed times, using GPS tags fitted to individuals. However, this method is invasive and only allows tracking of a subset of individuals. Here, we use an alternative, noninvasive camera-trapping approach to monitor temporal proximity of predator and prey animals. We deployed camera traps at fixed locations on Barro Colorado Island, Panama, where the ocelot (Leopardus pardalis) is the principal mammalian predator, and tested two hypotheses: (1) prey animals avoid ocelots; and (2) ocelots track prey. We quantified temporal proximity of predators and prey by fitting parametric survival models to the time intervals between subsequent prey and predator captures by camera traps, and then compared the observed intervals to random permutations that retained the spatiotemporal distribution of animal activity. We found that time until a prey animal appeared at a location was significantly longer than expected by chance if an ocelot had passed, and that the time until an ocelot appeared at a location was significantly shorter than expected by chance after prey passage. These findings are indirect evidence for both predator avoidance and prey tracking in this system. Our results show that predator avoidance and prey tracking influence predator and prey distribution over time in a field setting. Moreover, this study demonstrates that camera trapping is a viable and noninvasive alternative to GPS tracking for studying certain predator-prey interactions.

Landscape‐scale drivers of liana load across a Southeast Asian forest canopy differ to the Neotropics

Abstract Lianas (woody vines) are a key component of tropical forests, known to reduce forest carbon storage and sequestration and to be increasing in abundance. Analysing how and why lianas are distributed in forest canopies at landscape scales will help us determine the mechanisms driving changes in lianas over time. This will improve our understanding of liana ecology and projections of tropical forest carbon storage now and into the future. Despite competing hypotheses on the mechanisms driving spatial patterning of lianas, few studies have integrated multiple tree‐level biotic and abiotic factors in an analytical framework. None have done so in the Palaeotropics, which are biogeographically and evolutionarily distinct from the Neotropics, where most research on lianas has been conducted. We used an unoccupied aerial system (UAS; drone) to assess liana load in 50‐ha of Palaeotropical forest canopy in Southeast Asia. We obtained data on hypothesised drivers of liana spatial distribution in the forest canopy, including disturbance, tree characteristics, soil chemistry and topography, from the UAS, from airborne LiDAR and from ground surveys. We integrated these in a comprehensive analytical framework to extract variables at an individual‐tree level and evaluated the relative strengths of the hypothesised drivers and their ability to predict liana distributions through boosted regression tree (BRT) modelling. Tree height and distance to canopy gaps were the two most important predictors of liana load, with relative contribution values in BRT models of 34.60%–45.39% and 7.93%–10.19%, respectively. Our results suggest that taller trees were less often and less heavily infested by lianas than shorter trees, opposite to Neotropical findings. Lianas also occurred more often, and to a greater extent, in tree crowns close to canopy gaps and to neighbouring trees with lianas in their crown. Synthesis. Despite their known importance and prevalence in tropical forests, lianas are not well understood, particularly in the Palaeotropics. Examining 2428 trees across 50‐ha of Palaeotropical forest canopy in Southeast Asia, we find support for the hypothesis that canopy gaps promote liana infestation. However, we also found that liana presence and load declined with tree height, which is opposite to well‐established Neotropical findings. This suggests a fundamental difference between Neotropical and Southeast Asian forests. Considering that most liana literature has focused on the Neotropics, this highlights the need for additional studies in other biogeographic regions to clarify potential differences and enable us to better understand liana impacts on tropical forest ecology, carbon storage and sequestration.

Plasticity in Compensatory Growth to Artificial Defoliation and Light Availability in Four Neotropical Understory and Forest Edge Herb Species.

Simple SummaryFor monocot herbs growing in the understory of wet tropical forests face an extreme hazard in falling branches and debris from the canopy. We compared the response of two species of understory herbs to two other species of herbs growing at the forest edge or in large gaps. We made the prediction that the forest edge herb species would be better able to compensate for damage because of compensatory growth made possible in the higher light environment than that experienced by the shade-tolerant understory herbs. Our experimental studies showed that both groups of species were tolerant of defoliation under high and intermediate light conditions, but under low light growth conditions the forest edge species showed higher mortality. This finding suggests that a variety of functional growth traits may be structuring post-damage response in understory and forest edge herbs.Defoliation from falling branches is a major factor in the survival of understory herbs in tropical rainforests. Experimental studies of defoliation under three levels of light environment compared responses to partial and total defoliation in four species of tropical rainforest understory herbs. We predicted that elevated levels of light availability would help compensate for damage to through compensatory growth in both understory and forest edge species and that forest edge species would more effectively compensate under high light conditions than shade-tolerant species from the forest understory All species showed a high tolerance to defoliation under high and intermediate light conditions. Under low-light conditions survival differed dramatically with minimal mortality in forest-edge species compared to high mortality in completely defoliated understory species. Defoliation, and light × defoliation interactions, impacted multiple growth traits in understory species. In contrast, forest-edge species showed no effect of defoliation except on total biomass, and only one light × defoliation interaction was observed. Our results indicate that differences in biomass allocation, leaf ecophysiology, and other growth parameters between forest understory and edge species may be structuring post-damage response in understory and forest edge herbs.

Small scale changes in spider diversity and composition between two close elevations in a Neotropical forest

ABSTRACT Tropical rainforests are one of the most diverse ecosystems worldwide, yet the mechanisms driving the spatial distribution of their biodiversity remain poorly understood. Here, we tested the effects of elevation, sampling method and their interaction on α and β diversities of spider assemblages between two close elevations in one tropical forest of French Guiana. Through a standardized protocol, both ground- and vegetation-dwelling (up to 2.5-m high) assemblages were sampled at medium and high elevations, during day and night using 3 complementary methods (beating, sweeping, and nocturnal hand collecting). Despite a lower total number of species at high elevation, we found no significant effect of elevation on mean species richness. However, elevation had a significant effect on species composition, notably with less web builders and more ground hunters at higher elevations. In addition, we found a significant effect of sampling methods on both estimated species richness and composition. These results suggest that even slight elevation shape spider assemblages of tropical forests, which probably contributes to the high turn-over and amazing gamma diversity of these ecosystems.

Functional diversity and redundancy of amphibians, ants, and dung beetles in passive and active cloud forest restoration

Forest restoration practices have increased globally, with positive consequences for biodiversity conservation. However, our understanding of the variation in ecosystem functioning recovery presented among different restoration strategies remains limited, and few studies have compared the functional diversity of contrasting faunal assemblages. Here, we assessed how the functional diversities and functional redundancies of amphibian, ant, and dung beetle assemblages vary among forests of the same age (23 years) under active (native mixed plantations) and passive (natural regeneration) restoration, cattle pasture (degraded ecosystem), and mature cloud forest (reference ecosystem). We also explored how environmental variables relate to the functional diversity of each animal assemblage. We found that functional diversity (measured as functional richness, functional evenness, and functional divergence) and functional redundancy in the three faunal assemblages were similar between the two restoration strategies. However, some attributes of functional diversity did not reach the values of the reference ecosystem, especially in the amphibians and dung beetles. Environmental variables related to functional diversity also depended on the taxonomic group and the metric of functional diversity, but the most important of these variables were vegetation condition, canopy cover and tree density. In our study system, passive and active restoration produced similar recovery rates of functional diversity of the faunal assemblages. Regardless of the restoration strategy implemented, long-term adaptive management strategies must be implemented to ensure full recovery of biodiversity and functionality in Neotropical cloud forest landscapes.

Drought Tolerance Traits in Neotropical Trees Correlate with the Composition of Phyllosphere Fungal Communities

Plant-associated microorganisms have been shown to aid plants in coping with drought. However, the underlying mechanisms are poorly understood and there is uncertainty regarding which microbial taxa and functions are mostly involved. We explored these issues in Neotropical rainforests and identified foliar microorganisms that may play a role in drought tolerance of trees. Our objectives were to (i) test the relationship between drought tolerance traits in Neotropical trees and the diversity and composition of their foliar fungal and bacterial communities and (ii) identify leaf microbial taxa positively or negatively associated with drought tolerance traits. Our results showed that the composition of leaf fungal communities but not bacterial communities was related to drought tolerance. We identified 27 fungal amplicon sequence variants whose relative abundance covaried with drought tolerance traits. Most variants were assigned to fungal clades often described as plant pathogens and increased in abundance with drought susceptibility. This greater relative abundance of leaf pathogens in the most drought-susceptible trees might increase their vulnerability to climate change. Moreover, we identified the Strelitziana and Ochroconis fungal genera as potential candidates for future culture-dependent studies aimed at understanding and improving drought tolerance in Neotropical forests. [Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Distributional patterns and conservation of the genus Habromys (Rodentia: Cricetidae) in Mesoamerica

ABSTRACT We analyzed the geographical distribution of Habromys species based on distributional data from museum specimens, web databases, and literature. We recorded species-presence data of each species in 0.5° × 0.5° grid cells and biogeographic provinces in Mexico and Central America. We analyzed the association between vegetation types and land use. We carried out species distribution models of most species of Habromys and those tree species frequently harboring these mice, finding a high distributional congruence among mice and trees. Species of Habromys occur throughout the montane systems of Mexico and northern Central America, so they can be considered characteristic elements of the Neotropical montane cloud forests. All species of the genus occur in Mexico, whereas Guatemala and El Salvador have only one species. Although all species of Habromys are highly restricted and considered rare species, only one (H. simulatus) is currently protected by Mexican laws. We assigned two species to a high and four to the critical conservation risk. Habromys species contribute to the recognition of Mesoamerica as a biodiversity hotspot.

Pollen Preference Patterns by Tetragonisca angustula (Apidae: Meliponini) in a Boliviano-Tucumano Forest.

Native bees are important pollinators in neotropical forests. Tetragonisca angustula (Latreille) (Apidae: Meliponini) is a stingless bee widely distributed from the south of Mexico to Argentina. We characterized the patterns of preference of T. angustula for pollen in relation to the richness and abundance of plant species in the Tucumano-Boliviano Forest. During two field campaigns in different seasons (winter and spring), six colonies of T. angustula were studied. Pollen from flowers of plant species in the study area (pollen offer) and pot-pollen in each hive (pollen demand) were collected and their plant family of origin identified. Pollen from Asteraceae was more abundant in the winter than in the spring. Pollen of Solanaceae in the winter and Bignoniaceae in the spring were the most selected by the worker bees. Pollen from plants outside the sampling area was also found in the pots; it was mainly from Asteraceae. Tetragonisca angustula workers showed a polylectic foraging behavior, being able to use in a dynamic way the resources that are present in their environment at different times of the year; occasionally, it selected less abundant specific resources likely based on their nutritional value. More studies are needed to evaluate aspects of pollen quality consumed by this bee.

Effects of climate change on plant resource allocation and herbivore interactions in a Neotropical rainforest shrub

AbstractClimate change is a mounting global issue, but its consequences will be variable across regions. Tropical species are hypothesized to have reduced climatic adaptability and plasticity. Yet, relative to temperate species, less is understood about how they will respond to climate change. Rising temperature and atmospheric CO2 could impact plant–herbivore systems directly by altering species traits or abundances, or the effects could be indirect by altering the strength and direction of the relationships that govern organismal strategies and interactions. Using open‐top chambers in a Neotropical wet forest, we applied a full‐factorial combination of active warming and CO2 fertilization to investigate the above‐ground, short‐term effects of climate change on plant–herbivore interactions in a common Neotropical shrub, Piper generalense. We aimed to answer two main questions: (1) Could climate change alter plant–herbivore systems through direct effects on plant growth rate, chemical defense, and/or insect herbivore damage rate? and (2) Could climate change affect plant–herbivore systems indirectly by altering (a) the strength of plant resource allocation trade‐offs between growth and defense or (b) the effectiveness of plant chemical defense against herbivory? None of the microclimate treatments had direct effects on plant growth, chemical defense, or herbivore damage. However, we did observe a positive relationship between growth and chemical defense in treatments mimicking climate‐change conditions, which partially supports the growth–differentiation balance hypothesis. We did not detect any effects of treatments on the effectiveness of plant chemical defense against herbivory. It appears that, in this system, increased CO2 concentration and temperature may cause indirect, cascading consequences, even where direct effects are not observable. We recommend more climate‐change experiments addressing multi‐trophic interactions that focus not only on the direct responses of organisms but also on the ways in which climate change can restructure the relationships that govern complex biotic systems.

Patterns and controls on island‐wide aboveground biomass accumulation in second‐growth forests of Puerto Rico

AbstractUnderstanding the heterogeneity of biomass accumulation in second‐growth tropical forests following land use abandonment is important for informing ecosystem carbon models and forest restoration efforts. There is an urgent need for a broad sample of second‐growth forests to enhance our knowledge of carbon accumulation in human‐dominated landscapes, especially for older forests. Puerto Rico has predominantly second‐growth forests, ranging in age from approximately 25 to more than 80 years. We used an island‐wide sample of airborne lidar from the NASA Goddard Lidar, Hyperspectral, and Thermal (G‐LiHT) Airborne Imager collected on March 2017, forest inventory data, and data on forest age, precipitation, soils, and land use to estimate aboveground biomass stocks in moist and wet, second‐growth tropical forests. Biomass accumulation rates in Puerto Rico were lower, on average, than in other Neotropical forests. Median biomass across >16,700 ha of older second‐growth forests was 105 Mg ha−1, and sampled biomass rarely surpassed 250 Mg ha−1. Differences in biomass by age were large and persistent across different substrates and land uses, with a plateau in the pattern of island‐wide biomass accumulation after about 33 years. A spatial regression model showed that multiple factors were related to biomass accumulation, including time since abandonment, geologic substrate, past land use as coffee or pasture, precipitation, topographic wetness index, and slope. Our findings have important consequences for the total carbon storage and expected climate mitigation benefits of large‐scale reforestation efforts, and highlight the value of airborne lidar for quantifying biomass variability in complex tropical landscapes.Abstract in Spanish is available with online material.

Phylogeography supports lineage divergence for an endemic rattlesnake (Crotalus ravus) of the Neotropical montane forest in the Trans-Mexican Volcanic Belt

Abstract The formation of the Trans-Mexican Volcanic Belt (TMVB) and Pleistocene climatic fluctuations have been shown to influence the diversification of lineages and species distributed throughout central Mexico. In some taxa, however, evidence of lineage diversification is not easily recognized, as often is the case in reptiles. Here we present a phylogeographic study on a Mexican endemic rattlesnake species (Crotalus ravus), with the aim of understanding how distinct lineages are distributed across the TMVB. Genetic (mtDNA) and genomic (ddRADseq) data were generated from samples across the species’ range to evaluate phylogeographic structure, estimate phylogenetic relationships and divergence times, and perform environmental niche modeling (ENM). Both datasets recover strong phylogeographic structuring of two distinct lineages on an east-west axis, with an estimated Pleistocene divergence (~1.47 Myr). The ENM suggest that the distribution of the two lineages experienced expansion and reduction events throughout recent evolutionary time. We attribute the diversification of C. ravus lineages to geological events associated with the formation of the TMVB, as well as Quaternary climate changes, both of which have been previously recognized in co-distributed taxa in the TMVB. This work emphasizes the existence of cryptic diversification processes in a morphologically conserved species distributed in a region of complex climatic and orogenic heterogeneity.

Temporal and spatial diversification along the Amazonia-Cerrado transition in Neotropical treefrogs of the Boana albopunctata species group

Despite extensive research on biodiversity in Neotropical forests, biodiversity in seasonally dry, open biomes in South America has been underestimated until recently. We leverage a widespread group, Boana albopunctata, to uncover cryptic lineages and investigate the timing of diversification in Neotropical anurans with a focus on dry diagonal biomes (Cerrado, Caatinga and Chaco) and the ecotone between Amazonia and the Cerrado. We inferred a multilocus phylogeny of the B. albopunctata species group that includes 15 of 18 described species, recovered two cryptic species, and reconstructed the timing of diversification among species distributed across multiple South American biomes. One new potential species (B. aff. steinbachi), sampled in the Amazonian state of Acre, clustered within the B. calcara-fasciata species complex and is close to B. steinbachi. A second putative new species (B. aff. multifasciata), sampled in the Amazonia-Cerrado ecotone, is closely related to B. multifasciata. Lastly, we place a recently identified Cerrado lineage (B. aff. albopuncata) into the B. albopunctata species group phylogeny for the first time. Our ancestral range reconstruction showed that species in the B. albopuctata group likely dispersed from Amazonia-Cerrado into the dry-diagonal and Atlantic Forest. Intraspecies demography showed, for both B. raniceps and B. albopunctata, signs of rapid expansion across the dry diagonal. Similarly, for one clade of B. multifasciata, our analyses support an invasion of the Cerrado from Amazonia, followed by a rapid expansion across the open diagonal biomes. Thus, our study recovers several recent divergences along the Amazonia-Cerrado ecotone in northern Brazil. Tectonic uplift and erosion in the late Miocene and climate oscillations in the Pleistocene corresponded with estimated divergence times in the dry diagonal and Amazonia-Cerrado ecotone. Our study highlights the importance of these threatened open formations in the generation of biodiversity in the Neotropics.

Phylogenomics of arboreal alligator lizards shed light on the geographical diversification of cloud forest‐adapted biotas

AbstractAimThe proximate ecological and evolutionary processes underlying the high biodiversity of neotropical montane cloud forests are still very poorly understood. Climatic oscillations may have contributed to vicariance and cladogenesis, but also promoted secondary contact and erosion of genetic divergence. Here we tested whether geographical diversification – or its lack thereof – in a complex of arboreal alligator lizards is explained by range shifts during Quaternary climatic oscillations.LocationPine–oak and cloud forests, central Mexico.TaxonAbronia taeniata–gramineaspecies complex (Squamata: Anguidae: Gerrhonotinae).MethodsWe generated genomic data (ddRADseq) to infer patterns of geographical diversification in the complex, reconstruct its demographic history, estimate the timing of lineage split, and test for the presence of contemporary and/or historical hybridization. We evaluated whether the tempo and mode of diversification (i.e. strict isolation vs. secondary contact with introgression) are explained by the contemporary distribution of suitable habitats and/or range shifts experienced by the complex since the Last Glacial Maximum (LGM), as inferred from environmental niche modelling (ENM).ResultsGenomic data supported a marked genetic structure within the complex, and phylogenomic and dating analyses revealed cryptic lineage diversification starting at the onset of the Pleistocene followed by secondary contact with limited introgression. ENM pointed to considerable range expansions of the complex during the LGM and a marked fragmentation and scarce connectivity among contemporary populations, which was supported by genomic‐based demographic reconstructions.Main ConclusionsThe geographical diversification of the complex has been moulded by vicariant events promoted by Pleistocene geologic and climatic changes impacting the distribution of their pine–oak and cloud forest habitats. Our data supported a model of divergence with introgression, indicating that pulses of population fragmentation and expansion during the Quaternary have led to multiple opportunities for both allopatric isolation and secondary contact.

Phylogenomic data resolve the historical biogeography and ecomorphs of Neotropical forest lizards (Squamata, Diploglossidae)

Few studies have been conducted on the biogeography and phylogenetic relationships of Neotropical forest lizards (Diploglossidae) because of incomplete taxon sampling, conflicting datasets, and low statistical support at phylogenetic nodes. Here, we enhance a recent nine-gene dataset with a genomic dataset of 3,232 loci and 642,775 aligned base pairs. The resulting phylogeny includes 30 diploglossid species, 10 of the 11 genera, and the three subfamilies. It shows significant support for all supra-specific taxa in either maximum likelihood or Bayesian analyses or both. With this well-supported phylogeny, we further investigate the historical biogeography of the group and how diploglossids reached the Caribbean islands. Our analyses indicate that Antillean diploglossid lizards originated from at least two overwater dispersals from South America. Our tests for the strength of convergent evolution between morphologically similar taxa support the recognition of a soil and a tree ecomorph. In addition, we propose grass, ground, rock, and swamp ecomorphs for species in this family based on ecological and morphological data and analyses.

Strong floristic distinctiveness across Neotropical successional forests.

Forests that regrow naturally on abandoned fields are important for restoring biodiversity and ecosystem services, but can they also preserve the distinct regional tree floras? Using the floristic composition of 1215 early successional forests (≤20 years) in 75 human-modified landscapes across the Neotropic realm, we identified 14 distinct floristic groups, with a between-group dissimilarity of 0.97. Floristic groups were associated with location, bioregions, soil pH, temperature seasonality, and water availability. Hence, there is large continental-scale variation in the species composition of early successional forests, which is mainly associated with biogeographic and environmental factors but not with human disturbance indicators. This floristic distinctiveness is partially driven by regionally restricted species belonging to widespread genera. Early secondary forests contribute therefore to restoring and conserving the distinctiveness of bioregions across the Neotropical realm, and forest restoration initiatives should use local species to assure that these distinct floras are maintained.

Multi-year, post-harvesting impact assessment in a neotropical secondary Atlantic Forest

Subject to overexploitation in the past centuries, the Atlantic Forest is subject to very rigorous protection rules. However, the law is a controversial issue since landowners are not compensated for the limited choice of land use possibilities. We believe that, alternatively to a general timber harvest ban, sustainable forest management of the Atlantic Forest has the potential to generate income for the landowners while sustaining important ecological functions of the forest. Such choice would require better understanding of the potential effects of timber harvesting on the forest ecosystem and on species composition and succession over time. In this context, we assessed the harvesting impact of a conventional harvesting method (CM) and compared it to an alternative harvesting method (AM) in three different stands (stands A, B and C) of a secondary forest fragment in southern Brazil. Results from three comprehensive forest inventories over a period of two years were used to assess the timber harvesting impact. Measurements of species composition (i.e., number of species, life form, ecological group), forest structure (i.e., density, basal area, DBH, volume) and saplings density formed the basis of the impact assessment. The inventories were carried out before, immediately after and two years after harvesting. Intensities of damage on remnant trees immediately after harvesting and two years after harvesting were also measured. Before harvesting, a total of 114 tree species (trees, tree fern and palm tree) belonging to 49 families were identified in the study site’s three research stands. Palm trees and secondary species, such as Euterpe edulis, represented the majority of recruited individuals (DBH ≥ 5 cm) two years after harvesting. However, new saplings (DBH ≤ 5 cm) after two years were mainly pioneer woody tree species, such as Cecropia glaziovii and Schizolobium parahyba. On average, AM reduced damage to saplings by 5%. Most of the damages caused by CM were moderate to severe, while AM caused light to moderate damages. Binary logistic regression indicated dependency of the mortality rates on the independent variables “stand, stem and leaning damages.” On the other hand, the recovery rates of damaged trees were dependent on crown, stem and leaning damages. Therefore, two years after harvesting a higher mortality rate of low-dimensional trees was observed in stands with high density of smaller trees and high density of improvement felling. Although crown damages were not related to mortality rates, high intensity of crown damages reduced recovery rates over time.

Climate Change Affects Reproductive Phenology in Lianas of Australia’s Wet Tropics

Lianas are increasing in abundance in many tropical forests. This increase can alter forest structure and decrease both carbon storage and tree diversityviaantagonistic relationships between lianas and their host trees. Climate change is postulated as an underlying driver of increasing liana abundances,viaincreases in dry-season length, forest-disturbance events, and atmospheric CO2concentrations; all factors thought to favour lianas. However, the impact of climate change on liana reproductive phenology, an underlying determinant of liana abundance, has been little studied, particularly outside of Neotropical forests. Over a 15-year period (2000–2014), we examined the phenological patterns of a liana community in intact rainforests of the Wet Tropics bioregion of Australia; a World Heritage Area and hotspot of floral diversity. Specifically, we assessed (1) flowering and fruiting patterns of liana species; (2) potential climate drivers of flowering and fruiting activity; and (3) the influence of El Niño-related climatic disturbances on liana phenology. We found that flowering and fruiting of the studied liana species increased over time. Liana reproduction, moreover, rose in apparent response to higher temperatures and reduced rainfall. Finally, we found flowering and fruiting of the liana species increased following El Niño events. These results suggest that liana reproduction and abundance are likely to increase under predicted future climate regimes, with potentially important impacts on the survival, growth, and reproduction of resident trees and thus the overall health of Australian tropical rainforests.

Repeated burning undermines the value of regenerating cattle pastures for tropical forest birds

Forest restoration has become a central strategy to conserve biodiversity, especially in the global tropics, but many priority regions are increasingly threatened by anthropogenic stressors. Of particular concern is the growing frequency of fire in humid tropical systems due to agricultural expansion and regional drying. Yet little is known about how fire affects recovery of tropical biodiversity in restored lands, including forest-dependent and threatened species. Here we provide the first assessment of the impacts of burning within naturally regenerating cattle pastures on pasture use by Neotropical forest birds. Working within 1–11-year-old regenerating pastures in Guatemala’s Maya Biosphere Reserve, we asked how occupancy rates of forest-dependent and threatened bird species differ between repeatedly burned and unburned pasture. To better understand the effect of fire on pasture use, we examined how species’ opportunistic use of regenerating pastures is a function of vegetation succession at local scales. We found that 70 forest-dependent and 19 threatened species used unburned pastures, but fire reduced or eliminated pasture use for 56% of forest-dependent and 53% of threatened species. Local vegetation succession explained the likelihood of colonizing pastures for nearly half of forest species that used regenerating pastures. Species closely associated with closed-canopy vegetation were most likely to be partially or fully excluded from burned pasture, suggesting that fire excluded certain species by impeding forest regrowth. Our results clearly demonstrate that burning undermines the high value of regenerating pastures for forest-dependent and threatened species and highlight the critical importance of preventing human-caused fires in restored tropical landscapes.

Paleoecological Studies at the Ancient Maya Center of Yaxnohcah Using Analyses of Pollen, Environmental DNA, and Plant Macroremains

Yaxnohcah was a major city of the ancient Maya world, especially during the Preclassic period (1000 BCE–200 CE). Data from excavations provide important insights into the interactions between the ancient inhabitants and its surrounding Neotropical forests, a topic that, as a whole, remains largely enigmatic. This study aspired to fill that void in understanding by using traditional paleoethnobotanical approaches and a powerful new technology, the analysis of environmental DNA. Our results enabled us to characterize the vegetation growing in association with the principal structures and the artificial reservoirs that provided the city’s water supply. Because the area is without access to permanent water sources, such as rivers or lakes, these reservoirs were key to the development and survival of the city. Our results indicate that although there were large areas cleared for agricultural purposes, a mosaic of mature upland and bajo forest remained throughout the Maya occupation. In addition, our studies reveal that there were incursions of pine savanna into the area that may have been a reflection of prevailing edaphic conditions, or alternatively, the result of frequent burning.