Secondary Tropical Dry Forests Research Articles

Succession and seasonality of a Brazilian secondary tropical dry forest: Phenology and climate moderation

With large tracts of Tropical Dry Forests (TDF) in the Americas previously deforested, many places are currently undergoing secondary ecological succession. These processes vary in time and space, creating a landscape with forests of different ages or successional stages. These secondary forests need moreneed more understanding about how their ecosystem functionality is restored and recovering along the succession path. In particular, it is poorly understood how different successional stages moderate extremes of Essential Climatic Variables (ECV) such as temperature, relative humidity, soil moisture, and the fraction of Absorbed Photosynthetic Active Radiation (fAPAR). This paper, therefore, studies the linkages between high temporal resolution tower-based optical canopy phenology time series and seasonal changes in local ECV conditions between early (10–12 years) and late (50+ years) successional stage TDF in southeastern Brazil. We compare diurnal and seasonal patterns of understory ECVs between early/late plots and investigate the canopy’s Climate Moderating Capacity (CMC). Our data indicate at least 100 mm of precipitation within two weeks is necessary to initiate leaf flushing in this TDF. We also find that soil moisture and daytime air humidity strongly correlate (R2 > 0.75) with seasonal patterns in canopy vegetation greenness indices and fAPAR with a cross-correlation time lag peak of 12–15 days. Our results suggest that the late stage is more effective at cooling (−1.4 ± 0.6 °C vs −0.8 ± 0.6 °C) and reducing daytime evaporation (−0.41 ± 0.2 kPa vs −0.18 ± 0.12 °C) in the understory during the growing season than the early stage. Results suggest that the CMC varies with seasonal canopy leaf area dynamics and with heat and moisture scales, becoming significantly stronger when temperatures and vapour pressure deficits were highest, and correlated strongly with canopy fAPAR dynamics (R2 = 0.82). These findings demonstrate that TDFs can effectively regain microclimatic buffering capacity.

Crown cover of a dominant pioneer legume affects tree species regeneration in a secondary tropical dry forest

Background: Individual pioneer tree species often dominate early tropical dry forest succession and thereby affect possible successional pathways. Mimosa acantholoba var. eurycarpa is a highly dominant species in the tropical dry forest in Mexico.
 Hypothesis: Mimosa acantholoba var. eurycarpa exerts an inhibitory effect on the germination, establishment, survival, and early growth of light-demanding pioneers, while facilitating these processes for shade-tolerant old-growth forests species.
 Studied species: Lonchocarpus torresiorum, Lysiloma divaricatum, Mimosa acantholoba var. eurycarpa and Vachellia farnesiana.
 Study site and dates: Nizanda, Oaxaca, Mexico, 2020-2021.
 Methods: In 12 early successional plots, we applied three levels of crown cover removal (100, 50, and 0 %) of established trees of the dominant pioneer legume (M. acantholoba var. eurycarpa). We sowed seeds of the four study species in each experimental plot and recorded their germination, establishment, survival, and early growth over a 2-mo period.
 Results: The removal of crown cover of established M. acantholoba var. eurycarpa trees did not significantly affect germination. Lysiloma divaricatum had the highest germination probability, the fastest germination, and the highest establishment probability regardless of treatment. Lonchocarpus torresiorum had the highest establishment probability in plots where the crown cover of established M. acantholoba var. eurycarpa trees was removed The survival probability of both shade-tolerant species was highest in the 100 % removal treatment.
 Conclusions: Despite successful germination of shade-tolerant species, their survival is inhibited under the dense canopy of the dominant legume. Therefore, interventions to reduce the crown cover area of this dominant legume may stimulate forest recovery.

Tropical dry forest response to nutrient fertilization: a model validation and sensitivity analysis

Abstract. Soil nutrients, especially nitrogen (N) and phosphorus (P), regulate plant growth and hence influence carbon fluxes between the land surface and atmosphere. However, how forests adjust biomass partitioning to leaves, wood, and fine roots in response to N and/or P fertilization remains puzzling. Recent work in tropical forests suggests that trees increase fine root production under P fertilization, but it is unclear whether mechanistic models can reproduce this dynamic. In order to better understand mechanisms governing nutrient effects on plant allocation and improve models, we used the nutrient-enabled ED2 model to simulate a fertilization experiment being conducted in a secondary tropical dry forest in Costa Rica. We evaluated how different allocation parameterizations affected model performance. These parameterizations prescribed a linear relationship between relative allocation to fine roots and soil P concentrations. The slope of the linear relationship was allowed to be positive, negative, or zero. Some parameterizations realistically simulated leaf, wood, and fine root production, and these parameterizations all assumed a positive relationship between relative allocation to fine roots and soil P concentration. Model simulations of a 30-year timeframe indicated strong sensitivity to parameterization and fertilization treatment. Without P fertilization, the simulated aboveground biomass (AGB) accumulation was insensitive to the parameterization. With P fertilization, the model was highly sensitive to the parameterization and the greatest AGB accumulation occurred when relative allocation to fine roots was independent of soil P. Our study demonstrates the need for simultaneous measurements of leaf, wood, and fine root production in nutrient fertilization experiments and for longer-term experiments. Models that do not accurately represent allocation to fine roots may be highly biased in their simulations of AGB, especially on multi-decadal timescales.

Diversity of orb-weaving spiders (Arachnida: Araneae) from tropical dry forest in Northern Colombia, with eleven new records for the country

ABSTRACT Tropical dry forest is one of the most threatened and least studied tropical ecosystems despite high species diversity and endemism. In Colombia, the knowledge of spider diversity in this ecosystem is limited. Herein, we compare the diversity and species composition of orb-weaving spiders in a primary and a secondary tropical dry forest in northern Colombia. Sampling was conducted in March and May 2018 using aerial and ground hand collection methods. We collected 1106 specimens belonging to seven families and 76 species. The species Aculepeira travassosi (Soares and Camargo, 1948), Ariston aristus Opell, 1979, Eriophora nephiloides (O. Pickard-Cambridge, 1889), Eustala conformans Chamberlin, 1925, Eustala guttata F.O. Pickard-Cambridge, 1904, Eustala illicita (O. Pickard-Cambridge, 1889), Micrepeira hoeferi Levi, 1995, Testudinaria quadripunctata Taczanowski, 1879, Tetragnatha elongata Walckenaer, 1841, Tetragnatha mandibulata Walckenaer, 1841 and Verrucosa reticulata (O. Pickard-Cambridge, 1889) are recorded from Colombia for the first time. Spider diversity was significantly different among forests, and the similarity in species composition was 43%. Diversity was only 26% lower in the secondary tropical dry forest, demonstrating the importance of this type of forest as reservoirs of spider diversity.

Dynamics of Carbon Accumulation in Tropical Dry Forests under Climate Change Extremes

We analyze here how much carbon is being accumulated annually by secondary tropical dry forests (TDFs) and how structure, composition, time since abandonment, and climate can influence the dynamics of forest carbon accumulation. The study was carried out in Santa Rosa National Park in Guanacaste province, Costa Rica and Mata Seca State Park in Minas Gerais, Brazil. Total carbon storage and carbon accumulation were obtained for both sites from the sum of the aboveground carbon and belowground carbon gain plus the annual litterfall. Carbon accumulation of these TDFs varied from 2.6 Mg C ha−1 y−1 to 6.3 Mg C ha−1 y−1, depending on the age of the forest stands. Time since abandonment and number of stems per plot were the best predictors for carbon storage, annual carbon gains, and losses. Mortality rates and carbon losses were also associated with seasonal climate variability. We found significant correlations between tree mortality, carbon losses and mean seasonal temperature, mean seasonal precipitation, potential evapotranspiration, and the Oceanic Niño Index. Carbon dynamics in tropical dry forests are driven by time since abandonment and forest structure; however, rising temperature and El Niño Southern Oscillation (ENSO) events can have a significant impact on tree mortality and carbon losses. Depending on their location and land-use history, some dry forests are more impacted by climatic extremes than others, and differences between secondary stages are expected.

Woody species richness drives synergistic recovery of socio-ecological multifunctionality along early tropical dry forest regeneration

Secondary tropical forests offer critical ecosystem services such as regulation of climate, soil and water resources, which are frequently traded off against the provision of forest products for human use or repeated clearing for agriculture. While some evidence also suggests potential synergies between regulating and material contributions of regenerating forests to people, the ecological mechanisms of multiple synergies remain poorly understood. We assess tradeoffs and synergies by testing for cascading effects of tropical dry forest age and vegetation drivers on key ecosystem properties that underpin multiple regulating, material and non-material contributions to people. To do so we first compiled published evidence to propose a conceptual framework of the causal dependence among variables. Then, we tested which direct or indirect effects of this a priori conceptual model are supported by structural equation models of measured data from a chronosequence of secondary tropical dry forest plots. We tested whether individual density, taxonomic or functional diversity, community-weighted mean in wood specific gravity, or composition of the woody vegetation best explained synergies or tradeoffs among multiple key ecosystem properties. We show a synergistic, positive effect of observed woody species richness on all four key ecosystem properties, including total basal area, litter layer carbon stocks, soil penetration resistance and availability and versatility of socioeconomically useful plants. A similar synergistic effect of linear age-dependent changes in species composition suggests that the simultaneous recovery of multiple functions is not only driven by absolute woody species accrual, but also by temporal woody species turnover as secondary succession proceeds. However, local farmers reported uses of only a small fraction of available plant biodiversity that has previously been documented in the literature to be socioeconomically useful. In synthesis, we found that observed woody species richness and successional turnover along tropical dry forest regeneration are synergistic drivers of biodiversity, ecosystem functioning and the availability and versatility of currently underutilized plant products in Western Mexico. Such observed synergy between a range of key regulating, material and non-material contributions to people highlights untapped socioecological potential for multifunctional tropical forest restoration through sustainable use.

Ecosystem services supply and interactions along secondary tropical dry forests succession

Secondary forests will likely dominate future tropical landscapes, and the ecosystem services they provide to humanity will be particularly relevant. However, few empirical studies provide quantitative evidence of how the supply of ecosystem services change along secondary forest succession. The need for such information is particularly pressing for tropical dry forests because of their extensive global coverage and a high degree of disturbance. Here we examine the changes in the potential supply of ecosystem services and the interactions among them along secondary tropical dry forest succession for a site on the Mexican Pacific coast. Using data from a chronosequence of twelve sites followed over ten years, we characterized changes in five ecosystem services along a successional gradient from abandoned farmland to old-growth forests: forage, multiple forest resources, microclimate regulation, carbon storage and carbon sequestration. The long-term recovery trajectory for each service was modelled using linear and non-linear mixed models. Interactions among them were examined over different timeframes using Spearman correlations. The results showed rapid non-linear recovery of multiple forest resources provision, microclimate regulation and carbon storage within the first two decades of succession. Carbon sequestration increased slightly over time, while the supply of forage showed no clear trend. The strength of the interactions among pairs of services changed through successional time, being particularly higher in farmlands and old-growth forests. Our findings suggest that adaptive forest management practices that foster the natural regeneration of tropical dry forests are cost-effective mechanisms to recover the supply of critical ecosystem services for local actors by meeting their livelihood needs as well as those for the global community through climate change mitigation. Maintaining tropical dry forest resilience will highly depend on the maintenance of diversity in terms of species and ecosystem services.

Diversity and local perception of lepidopterans in secondary tropical dry forests: Implications for management

Butterflies are one of insect groups cherished by humans because of their spectacular colors and shapes. However, the ecosystem services and/or disservices they provide are less clear-cut, since they can be both important pollinators as adults and agricultural pests as larvae. In this study, we evaluated local perceptions about lepidopterans in “Los Ranchitos,” Jalisco, Mexico and estimated butterfly diversity in nearby secondary forests. Our aim was to understand whether common knowledge values the ecosystem services butterflies provide and whether local perception correlates with secondary forest butterfly diversity and management. To estimate lepidopteran diversity, we used direct sampling with live traps and direct observation. To understand local perceptions about the role of lepidopterans for ecosystems and management of their lands, we conducted semi-structured interviews and workshops with local Ejidatarios (members of the local community and participants in a Mexican collective land ownership structure). We found a high diversity of lepidopterans (40 species) at the secondary forests throughout the year. Most Ejidatarios have diverse management strategies involving cattle ranching and agriculture. Local knowledge recognized their presence in their fields particularly in secondary forests. However, we detected little awareness of the link between lepidopteran larvae (herbivores) and adults (pollinators), and their role in wild plant pollination. Many Ejidatarios were interested in deepening their knowledge of the ecosystem services that lepidopterans provide in the region. Therefore, researchers should strengthen their communication skills and share the information about the ecosystem services biodiversity provides and how secondary forests hold an important amount of biodiversity. In order to improve secondary forest management there is a need to incorporate ecological knowledge into localś perceptions.

Improving the accuracy of aboveground biomass estimations in secondary tropical dry forests

Biomass estimates in tropical forests are mainly available for old-growth forests, but the expansion of tropical secondary forests urges the development of tools for more accurate estimations of biomass and carbon pools. In this study, we developed local allometric models to estimate aboveground biomass in secondary tropical dry forests of the Chamela region in western Mexico and compared their accuracy to that of non-local (“foreign”) allometric models. We harvested 303 trees from 27 woody species contributing ≥75% of total basal area in secondary forest plots (5–45 y-old) distributed across the landscape. Nine to 14 individuals per species, covering the full natural range in stem diameter (DBH) found in an inventory, were measured for DBH and height (H) before harvesting. Subsamples from each stem and branches were used for dry mass and wood specific density (WSD) determinations. Power model functions were fitted to relate tree AGB to one or a multiplicative combination of three predictors (DBH, H, and WSD). Species-specific models with DBH alone explained a high percentage of the variance in tree AGB (R2 = 0.927 to 0.999). Among our multispecies models, fit and prediction of biomass improved when pooling the species into low and high WSD functional groups. Using local or global WSD data did not affect the accuracy of our multispecies models. In contrast, bias increased in foreign models with the use of global WSD values. We discuss the applicability of our allometric models and foreign models to improve the accuracy of biomass predictions in secondary tropical dry forests.

Understanding and predicting frost-induced tropical tree mortality patterns.

Extreme climatic and weather events are increasing in frequency and intensity across the world causing episodes of widespread tree mortality in many forested ecosystems. However, we have a limited understanding about which local factors influence tree mortality patterns, restricting our ability to predict tree mortality, especially within topographically complex tropical landscapes with a matrix of mature and secondary forests. We investigated the effects of two major local factors, topography and forest successional type, on climate-induced tropical tree mortality patterns using an observational and modeling approach. The northernmost Neotropical dry forest endured an unprecedented episode of frost-induced tree mortality after the historic February 2011 cold wave hit northwestern Mexico. In a moderately hilly landscape covering mature and secondary tropical dry forests, we surveyed 454 sites for the presence or absence of frost-induced tree mortality. In addition, across forty-eight 1ha plots equally split into the two forest types, we examined 6,981 woody plants to estimate a frost-disturbance severity metric using the density of frost-killed trees. Elevation is the main factor modulating frost effects regardless of forest type. Higher occurrence probabilities of frost-induced tree mortality at lowland forests can be explained by the strong influence of elevation on temperature distribution since heavier cold air masses move downhill during advective frosts. Holding elevation constant, the probability of frost-induced tree mortality in mature forests was twice that of secondary forests but severity showed the opposite pattern, suggesting a cautious use of occurrence probabilities of tree mortality to infer severity of climate-driven disturbances. Extreme frost events, in addition to altering forest successional pathways and ecosystem services, likely maintain and could ultimately shift latitudinal and altitudinal range margins of Neotropical dry forests.

Plant community responses to stand-level nutrient fertilization in a secondary tropical dry forest.

The size of the terrestrial carbon (C) sink is mediated by the availability of nutrients that limit plant growth. However, nutrient controls on primary productivity are poorly understood in the geographically extensive yet understudied tropical dry forest biome. To examine how nutrients influence above- and belowground biomass production in a secondary, seasonally dry tropical forest, we conducted a replicated, fully factorial nitrogen (N) and phosphorus (P) fertilization experiment at the stand scale in Guanacaste, Costa Rica. The production of leaves, wood, and fine roots was monitored through time; root colonization by mycorrhizal fungi and the abundance of N-fixing root nodules were also quantified. In this seasonal forest, interannual variation in rainfall had the largest influence on stand-level productivity, with lower biomass growth under drought. By contrast, aboveground productivity was generally not increased by nutrient addition, although fertilization enhanced growth of individual tree stems in a wet year. However, root growth increased markedly and consistently under P addition, significantly altering patterns of stand-level biomass allocation to above- vs. belowground compartments. Although nutrients did not stimulate total biomass production at the community scale, N-fixing legumes exhibited a twofold increase in woody growth in response to added P, accompanied by a dramatic increase in the abundance of root nodules. These data suggest that the relationship between nutrient availability and primary production in tropical dry forest is contingent on both water availability and plant functional diversity.

Comparing forest structure and biodiversity on private and public land: secondary tropical dry forests in Costa Rica

AbstractSecondary forests constitute a substantial proportion of tropical forestlands. These forests occur on both public and private lands and different underlying environmental variables and management regimes may affect post‐abandonment successional processes and resultant forest structure and biodiversity. We examined whether differences in ownership led to differences in forest structure, tree diversity, and tree species composition across a gradient of soil fertility and forest age. We collected soil samples and surveyed all trees in 82 public and 66 private 0.1‐ha forest plots arrayed across forest age and soil gradients in Guanacaste, Costa Rica. We found that soil fertility appeared to drive the spatial structure of public vs. private ownership; public conservation lands appeared to be non‐randomly located on areas of lower soil fertility. On private lands, areas of crops/pasture appeared to be non‐randomly located on higher soil fertility areas while forests occupied areas of lower soil fertility. We found that forest structure and tree species diversity did not differ significantly between public and private ownership. However, public and private forests differed in tree species composition: 11 percent were more prevalent in public forest and 7 percent were more prevalent in private forest. Swietenia macrophylla, Cedrela odorata, and Astronium graveolens were more prevalent in public forests likely because public forests provide stronger protection for these highly prized timber species. Guazuma ulmifolia was the most abundant tree in private forests likely because this species is widely consumed and dispersed by cattle. Furthermore, some compositional differences appear to result from soil fertility differences due to non‐random placement of public and private land holdings with respect to soil fertility. Land ownership creates a distinctive species composition signature that is likely the result of differences in soil fertility and management between the ownership types. Both biophysical and social variables should be considered to advance understanding of tropical secondary forest structure and biodiversity.

Ant Assemblage Structure in a Secondary Tropical Dry Forest: The Role of Ecological Succession and Seasonality

This study identified the main biological mechanisms governing the diversity of ants on different ecological time scales. Ants were sampled in 15 plots distributed in early, intermediate and late stages of succession (five plots per stage) at the Parque Estadual da Mata Seca, Brazil. At each sample point, unbaited pitfall traps were installed in hypogaeic, epigaeic and arboreal strata. We collected 95 ant species from 26 genera and nine subfamilies. Our results indicated that there was an increase in species richness in advanced stages of succession. We also observed that ant assemblages were different among successional stages. For the arboreal and epigaeic strata, species richness did not change with succession progression, but species composition of these two strata differed among successional stages. Unlike to arboreal and epigaeic ants, hypogaiec ant species richness was higher in the intermediate and late stages of succession and the composition of hypogaeic ants differed among successional stages. Similarity between ant species foraging in arboreal and epigaeic strata decreases with succession progression and β-diversity was higher in advanced successional stages. Additionally, species richness was higher in the dry season, whereas the composition of ant assemblages did not change between seasons. A considerable fraction of the ant assemblage was found only in advanced stages of succession, demonstrating the importance of secondary habitats in maintaining biodiversity in dry forests.

Identifying tropical dry forests extent and succession via the use of machine learning techniques

Information on ecosystem services as a function of the successional stage for secondary tropical dry forests (TDFs) is scarce and limited. Secondary TDFs succession is defined as regrowth following a complete forest clearance for cattle growth or agriculture activities. In the context of large conservation initiatives, the identification of the extent, structure and composition of secondary TDFs can serve as key elements to estimate the effectiveness of such activities. As such, in this study we evaluate the use of a Hyperspectral MAPper (HyMap) dataset and a waveform LIDAR dataset for characterization of different levels of intra-secondary forests stages at the Santa Rosa National Park (SRNP) Environmental Monitoring Super Site located in Costa Rica. Specifically, a multi-task learning based machine learning classifier (MLC-MTL) is employed on the first shortwave infrared (SWIR1) of HyMap in order to identify the variability of aboveground biomass of secondary TDFs along a successional gradient. Our paper recognizes that the process of ecological succession is not deterministic but a combination of transitional forests types along a stochastic path that depends on ecological, edaphic, land use, and micro-meteorological conditions, and our results provide a new way to obtain the spatial distribution of three main types of TDFs successional stages.

Modeling seasonal surface temperature variations in secondary tropical dry forests

Secondary tropical dry forests (TDFs) provide important ecosystem services such as carbon sequestration, biodiversity conservation, and nutrient cycle regulation. However, their biogeophysical processes at the canopy-atmosphere interface remain unknown, limiting our understanding of how this endangered ecosystem influences, and responds to the ongoing global warming. To facilitate future development of conservation policies, this study characterized the seasonal land surface temperature (LST) behavior of three successional stages (early, intermediate, and late) of a TDF, at the Santa Rosa National Park (SRNP), Costa Rica. A total of 38 Landsat-8 Thermal Infrared Sensor (TIRS) data and the Surface Reflectance (SR) product were utilized to model LST time series from July 2013 to July 2016 using a radiative transfer equation (RTE) algorithm. We further related the LST time series to seven vegetation indices which reflect different properties of TDFs, and soil moisture data obtained from a Wireless Sensor Network (WSN). Results showed that the LST in the dry season was 15–20K higher than in the wet season at SRNP. We found that the early successional stages were about 6–8K warmer than the intermediate successional stages and were 9–10K warmer than the late successional stages in the middle of the dry season; meanwhile, a minimum LST difference (0–1K) was observed at the end of the wet season. Leaf phenology and canopy architecture explained most LST variations in both dry and wet seasons. However, our analysis revealed that it is precipitation that ultimately determines the LST variations through both biogeochemical (leaf phenology) and biogeophysical processes (evapotranspiration) of the plants. Results of this study could help physiological modeling studies in secondary TDFs.

Can terrestrial laser scanners (TLSs) and hemispherical photographs predict tropical dry forest succession with liana abundance?

Abstract. Tropical dry forests (TDFs) are ecosystems with long drought periods, a mean temperature of 25 °C, a mean annual precipitation that ranges from 900 to 2000 mm, and that possess a high abundance of deciduous species (trees and lianas). What remains of the original extent of TDFs in the Americas remains highly fragmented and at different levels of ecological succession. It is estimated that one of the main fingerprints left by global environmental and climate change in tropical environments is an increase in liana coverage. Lianas are non-structural elements of the forest canopy that eventually kill their host trees. In this paper we evaluate the use of a terrestrial laser scanner (TLS) in combination with hemispherical photographs (HPs) to characterize changes in forest structure as a function of ecological succession and liana abundance. We deployed a TLS and HP system in 28 plots throughout secondary forests of different ages and with different levels of liana abundance. Using a canonical correlation analysis (CCA), we addressed how the VEGNET, a terrestrial laser scanner, and HPs could predict TDF structure. Likewise, using univariate analyses of correlations, we show how the liana abundance could affect the prediction of the forest structure. Our results suggest that TLSs and HPs can predict the differences in the forest structure at different successional stages but that these differences disappear as liana abundance increases. Therefore, in well known ecosystems such as the tropical dry forest of Costa Rica, these biases of prediction could be considered as structural effects of liana presence. This research contributes to the understanding of the potential effects of lianas in secondary dry forests and highlights the role of TLSs combined with HPs in monitoring structural changes in secondary TDFs.

Estimation of aboveground net primary productivity in secondary tropical dry forests using the Carnegie–Ames–Stanford approach (CASA) model

Although tropical dry forests (TDFs) cover roughly 42% of all tropical ecosystems, extensive deforestation and habitat fragmentation pose important limitations for their conservation and restoration worldwide. In order to develop conservation policies for this endangered ecosystem, it is necessary to quantify their provision of ecosystems services such as carbon sequestration and primary production. In this paper we explore the potential of the Carnegie–Ames–Stanford approach (CASA) for estimating aboveground net primary productivity (ANPP) in a secondary TDF located at the Santa Rosa National Park (SRNP), Costa Rica. We calculated ANPP using the CASA model (ANPPCASA) in three successional stages (early, intermediate, and late). Each stage has a stand age of 21 years, 32 years, and 50+ years, respectively, estimated as the age since land abandonment. Our results showed that the ANPPCASA for early, intermediate, and late successional stages were 3.22 Mg C ha−1 yr−1, 8.90 Mg C ha−1 yr−1, and 7.59 Mg C ha−1 yr−1, respectively, which are comparable with rates of carbon uptake in other TDFs. Our results indicate that key variables that influence ANPP in our dry forest site were stand age and precipitation seasonality. Incident photosynthetically active radiation and temperature were not dominant in the ANPPCASA. The results of this study highlight the potential of the use of remote sensing techniques and the importance of incorporating successional stage in accurate regional TDF ANPP estimation.

Resilience of tropical dry forests – a meta‐analysis of changes in species diversity and composition during secondary succession

Assessing the recovery of species diversity and composition after major disturbance is key to understanding the resilience of tropical forests through successional processes, and its importance for biodiversity conservation. Despite the specific abiotic environment and ecological processes of tropical dry forests, secondary succession has received less attention in this biome than others and changes in species diversity and composition have never been synthesised in a systematic and quantitative review. This study aims to assess in tropical dry forests 1) the directionality of change in species richness and evenness during secondary succession, 2) the convergence of species composition towards that of old‐growth forest and 3) the importance of the previous land use, precipitation regime and water availability in influencing the direction and rate of change. We conducted meta‐analyses of the rate of change in species richness, evenness and composition indices with succession in 13 tropical dry forest chronosequences. Species richness increased with succession, showing a gradual accumulation of species, as did Shannon evenness index. The similarity in species composition of successional forests with old‐growth forests increased with succession, yet at a low rate. Tropical dry forests therefore do show resilience of species composition but it may never reach that of old‐growth forests. We found no significant differences in rates of change between different previous land uses, precipitation regimes or water availability. Our results show high resilience of tropical dry forests in term of species richness but a slow recovery of species composition. They highlight the need for further research on secondary succession in this biome and better understanding of impacts of previous land‐use and landscape‐scale patterns.SynthesisSecondary forests account for an increasing proportion of remaining tropical forest. Assessing their resilience is key to conservation of their biodiversity. Our study is the first meta‐analysis of species changes during succession focussing on tropical dry forests, a highly threatened yet understudied biome. We show a gradual species accumulation and convergence of composition towards that of old‐growth forests. While secondary tropical dry forests offer good potential for biodiversity conservation, their capacity for recovery at a sufficient rate to match threats is uncertain. Further research on this biome is needed to understand the effect of land use history and landscape processes.

Ensamblaje de Hormigas del Bosque Seco Tropical, Jardín Botánico de Cali

The ant assemblages of a fragment of secondary tropical dry forest located in the Botanical Garden of Cali are presented. Two habitats were chosen: a fragment of forest and a pasture matrix. Samples were taken monthly for six months, using a linear transect of 100 m, with 10 stations spaced 10 m. At each station pitfall traps, epigeal bait and arboreal, sifting and removal of 1 m 2 of litter and manual capture survey techniques were applied. Richness, abundance and diversity of ant habitats were determined. Correlation coefficients and regression between temperature, relative humidity and richness of ants were calculated. A total of 13 170 ants representing 55 species, 35 genera and six subfamilies were collected. The forest had the highest species richness with 90.9%. This wealth of diversity indicates the conservation value of the Valle del Cauca myrmecofauna. Although the forest is in the process of regeneration, strongly disturbed by constant fire and human intervention, the ant species richness shows that it remains an invaluable source of biological resources for the conservation of species.

Stand age and soils as drivers of plant functional traits and aboveground biomass in secondary tropical dry forest

The distribution of tropical forest biomass across the landscape is poorly understood, particularly in increasingly common secondary tropical forests. We studied the landscape-scale distribution of edaphic properties, plant community characteristics, and aboveground biomass (AGB) in secondary tropical dry forests in northwest Costa Rica. We used structural equation modeling to examine conceptual models of relationships among these factors, with data from 84 0.1 ha plots. Stand age and soils explained 33%–60% of the variation in community-weighted mean values of foliar traits including specific leaf area, foliar nitrogen, phosphorus, and δ13C. Aboveground biomass ranged from 1.7 to 409 Mg·ha−1 among plots between 5 and >100 years old. Stand age alone explained 46% of the variation in AGB among plots, while a model including age, soil pH, traits, and forest type explained 58%. Stand age was the most important variable explaining the distribution of AGB and community characteristics in secondary forests. We speculate that plot size, landscape heterogeneity, disturbance history, and stand dynamics contribute to the unexplained variation in AGB across the landscape.