Tropical Dry Forest In Mexico Research Articles

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.

Tree species differ in plant economic spectrum traits in the tropical dry forest of Mexico.

In tropical dry forests, studies on wood anatomical traits have concentrated mainly on variations in vessel diameter and frequency. Recent research suggests that parenchyma and fibers also play an important role in water conduction and in xylem hydraulic safety. However, these relationships are not fully understood, and wood trait variation among different functional profiles as well as their variation under different water availability scenarios have been little studied. In this work, we aim to (1) characterize a set of wood anatomical traits among six selected tree species that represent the economic spectrum of tropical dry forests, (2) assess the variation in these traits under three different rainfall regimes, and (3) determine the relationships between wood anatomical traits and possible functional trade-offs. Differences among species and sites in wood traits were explored. Linear mixed models were fitted, and model comparison was performed. Most variation occurred among species along the economic spectrum. Obligate deciduous, low wood density species were characterized by wood with wide vessels and low frequency, suggesting high water transport capacity but sensitivity to drought. Moreover, high cell fractions of carbon and water storage were also found in these tree species related to the occurrence of abundant parenchyma or septate fibers. Contrary to what most studies show, Cochlospermum vitifolium, a succulent tree species, presented the greatest variation in wood traits. Facultative deciduous, high wood density species were characterized by a sturdy vascular system that may favor resistance to cavitation and low reserve storage. Contrary to our expectations, variation among the rainfall regimes was generally low in all species and was mostly related to vessel traits, while fiber and parenchyma traits presented little variation among species. Strong functional associations between wood anatomical traits and functional trade-offs were found for the six tree species studied along the economic spectrum of tropical dry forests.

Taxonomic Novelties in Sapranthus (Annonaceae): a new large-sized species endemic to the mountain cloud forest of Central America

Sapranthus (Annonaceae) is a Neotropical genus comprising ten small tree species, most of which inhabit the tropical dry forests of Mexico and Central America. Morphological characteristics of these species are quite variable and taxonomically informative, but the morphological affinities among them have not been studied. A multivariate cluster analysis was carried out to infer the morphological affinities among all species of Sapranthus, and to establish the position of a new species, S. pinedai, a shade tree used in the coffee plantations of Guatemala and El Salvador. This new species, illustrated and described herein, is recognized by a unique combination of features identified through comparisons with morphologically similar taxa, and a preliminary assessment of the conservation status of the new species was calculated. The results presented here show that Sapranthus forms four morphological groupings in two main clusters. The new species is more similar to S. microcarpus and S. campechianus, but differs from both species by its essentially glabrous leaves, short pedicels, fewer carpels, greater number of ovules per carpel, biseriate ovules, larger sessile fruits with a thick testa, and by its several lunate to wedge-shaped seeds. These morphological groupings provides new insights into the understanding of the sectional classification of the genus Sapranthus, the geographic distribution of its species, and the morphological affinity of the new species.

Physiological ecology and vulnerability to climate change of a microendemic, habitat-specialist lizard in a tropical dry forest of Mexico

The role of physiology on habitat specialization in terrestrial ectotherms constitutes a rarely addressed topic, despite the fact that habitat specialization often involves the coadaptation of multiple physiological traits, which in turn may confer a higher vulnerability to climate change. Here we documented aspects of the thermal and hydric physiology of Sceloporus macdougalli, a lizard restricted to granite boulders in a tiny area of a tropical dry forest of Mexico, and estimated its vulnerability to climate change. We aimed to determine the physiological and behavioral adjustments used by this species to cope with a striking seasonal environment, to elucidate whether ecophysiology could help explain its habitat specialization, microendemicity, and how increasing environmental temperatures will restrict activity of this species. The effectiveness of thermoregulation and indications of water conservation strategies changed markedly over seasons. As expected, granite boulders and associated vegetation were more suitable for thermo- and hydroregulation than surrounding (and unoccupied) habitat. However, our model indicated that by 2041-2060 climate change will restrict activity of this species, enhancing its threat of extinction. These results highlight the importance of granite microhabitats for the thermal and water relations of S. macdougalli, in the context of climate change, and suggest that the current habitat and range restriction of the species might be an outcome of its physiology, thus demanding urgent actions to preserve the species from extinction.

Phylogeny of the Pyrenula ochraceoflava group (Pyrenulaceae) reveals near-cryptic diversification and the inclusion of the Mazaediothecium album aggregate

In this study we present an analysis of the Pyrenula ochraceoflava group (Pyrenulaceae), focusing on the Neotropics and based on morphological, chemical, and molecular data of the mtSSU, nuLSU and ITS markers. We described three new species from tropical dry forests of Mexico, confirm the monophyly of the P. ochraceoflava group and provide evidence for the inclusion of species currently placed in the genus Mazaediothecium within Pyrenula. Pyrenula aurantiacoretis sp. nov. is characterized by an orange pigment covering the thallus in net-like fashion, muriform ascospores with 4 rows of 1–4 cells each, 12–15.5 × 8–10.5 µm, and 7-chloroemodin and emodin as major compounds. Pyrenula connexa sp. nov. is closely related to Mazaediothecium album, being characterized by mazaedioid pyrenocarps, basal and lateral excipular carbonization, highly variable mature ascospores, 1-septate to submuriform, thallus with abundant white verrucae, and lichexanthone as major compound. Pyrenula moldenkeorum sp. nov. is characterized by an orange thallus, submuriform ascospores that frequently show pigmented septa forming a cross septation pattern, 7.5–11 × 5.5–8.5 µm in size, and 7-chloroemodin and emodin as major compounds. The taxonomy of the most common and widespread species of the group, P. ochraceoflava and P. ochraceoflavens, is briefly discussed, presenting evidence to support the consideration of P. ochraceoflava as a species complex. The two species Mazaedothecium album and M. mohamedii are transferred to Pyrenula as P. aptrootiana nom. nov. [non Pyrenula alba (Schrad.) A.Massal.] and P. mohamedii comb. nov.

Phylogenetic structure and diversity among herpetofaunal communities along a successional gradient of a tropical dry forest in Mexico

The tropical dry forest (TDF) is one of the most biodiverse ecosystems on earth, but also one of the most threatened. Therefore, it is critical to understand the processes that control community assembly and generate diversity during succession. We surveyed 15 herpetofaunal communities from a chronosequence of succession plots and tested whether phylogenetic structure (nonrandom distribution of species with respect to phylogeny) and phylogenetic diversity (incorporation of phylogenetic differences between species to measure biodiversity) differed among seasons and succession stages of the TDF in western Mexico. Phylogenetic structure and diversity of both groups showed temporal shifts. Our data suggest a role of environmental filtering in the first succession stages: during the rainy season in amphibians, allowing the coexistence of closely related species in water ponds, while for reptiles during the dry season, where higher exposure to solar radiation and humidity loss predominate in pastures. The more distantly related species in primary and secondary forests in later succession stages may predict ecosystem stability assuring the sufficient ecological strategies in a community to achieve the persistence of the ecosystem under changing conditions. Our results strengthen the arguments for promoting the conservation and managing of secondary forests under recovery to maintain phylogenetic diversity.

Color and morphological differentiation in the Sinaloa Wren (Thryophilus sinaloa) in the tropical dry forests of Mexico: The role of environment and geographic isolation.

The role and the degree to which environment and geographic isolation contribute to phenotypic diversity has been widely debated. Here, we studied phenotypic variation (morphology and plumage reflectance) in the Sinaloa Wren, an endemic bird distributed throughout the tropical dry forest (TDF) on the Mexican pacific slope where a pronounced variability in environmental conditions has been reported. In particular, we aimed: 1) to characterize phenotypic variation between subspecies; 2) to analyze the relationship between phenotypic and environmental variation in the context of classic ecogeographic rules, such as Bergmann’s, Allen’s, Gloger’s, and Bogert’s, and to quantify the relative roles of environment and geographic isolation and their interaction in shaping phenotypic variation; and 3) to test for niche conservatism between subspecies. Our data revealed significant differences among subspecies morphology and plumage reflectance. The environment explained a higher proportion of the morphological variation, while geography explained a smaller proportion. However, variation in plumage reflectance was mainly explained by the joint effect of geography and environment. Our data did not support for Bergmann´s and Allen´s rule. However, longer tails and wings were positively associated with higher elevations, larger tarsus and culmens were positively related to higher latitudes and to greater tree cover, respectively. Our data partially supported Gloger´s rule, where darker plumages were associated with more humid environments. The effects of temperature on plumage coloration were more consistent with Bogert´s rule. In addition, we found darker plumages related to higher levels of UV-B radiation. Finally, niche divergence was detected between T. s. cinereus and T. s. sinaloa vs. T. s. russeus. In a continuously distributed ecosystem such as the TDF on the pacific slope of Mexico, the environmental conditions and geographic isolation have played an important role in promoting phenotypic differentiation in the Sinaloa Wren.

Free amino acids in nectar: its composition and variability among bat-pollinated plants

Regardless of the low concentrations at which amino acids are present in floral nectar of bat-pollinated plants, their role as nectar flavor providers and their influence on bats’ foraging decisions have been recognized. Nevertheless, variation in the free amino acids among bat-pollinated plant species has been less studied. The goal of this study was to analyze the nectar free amino acids and to determine its variability among 8 bat-pollinated plant species from 5 families in a Tropical Dry Forest in Mexico. Nectar collections were made opportunistically depending on plants flowering season. We quantified 17 amino acids by HPLC. All 17 free amino acids were present in nectar from the 8 analyzed plant species. The concentration of 12 amino acids is explained by plant species by 19-58%. Analyses showed that Ceiba grandiflora (Malvaceae) was significantly different in asparagine content when compared to Bahuinia pauletia (Fabaceae) and Ceiba aesculifolia (Malvaceae), and in glutamic acid when compared to Ipomoea ampullacea (Convolvulaceae). We discuss the importance of free amino acids in nectar among plant species and their influence on bat pollination ecology.

Functional connectivity of an endemic tree frog in a highly threatened tropical dry forest in Mexico

ABSTRACT The increase in anthropogenic activities that lead to fragmentation and habitat loss, could result in a reduction of connectivity among habitat patches of terrestrial species. We used ecological niche models, circuit and graph theories to evaluate functional connectivity among home-range patches and suitable habitat patches of the Mexican Leaf Frog (Agalychnis dacnicolor), in a heterogeneous landscape of tropical dry forest (TDF) in central-western Mexico. We found high connectivity among home-range patches within the Chamela-Cuixmala Biosphere Reserve (CCBR) and among those surrounding the CCBR. Similarly, suitable habitat patches along the Pacific slope (except those in the South) were well-connected. Conversely, we detected weak connectivity in the southern and eastern parts of the study area, which is in accordance with the poor habitat quality and fragmentation that characterize that zone. Suitable habitat patches with the largest areas of TDF were the most important in maintaining functional connectivity, but only one patch was within a natural protected area. Our results highlight the importance of conserving large and continuous patches of habitat in a very threatened landscape to maintain connectivity in A. dacnicolor and probably in other anurans.

Sustaining Medicinal Barks: Survival and Bark Regeneration of Amphipterygium adstringens (Anacardiaceae), a Tropical Tree under Experimental Debarking

Commercial harvests can threaten tree species harvested for their bark. Amphipterygium adstringens is a dioecious tree, endemic to the tropical dry forests of Mexico, where it is intensively harvested for its medicinal bark. Limited information hinders developing sustainable management strategies for A. adstringens. We assessed bark regeneration for male and female trees, and evaluated the effect of tree sex and diameter, debarking treatments and cutting seasons on bark regeneration and tree survival rates. Bark regeneration was higher for wet season harvested trees (vs. dry), regardless of their sex. Bark regeneration was higher on female than on male trees. There were significant interactions of harvest season, harvest treatment and tree sex diameter on bark regeneration and survival. Overall, the highest bark regeneration rates occurred in female trees with ≥20.1 cm diameter that were wet season harvested with a 50% debarking intensity. Consequently, wet season and intermediate intensity harvests appear to foster sound management, but we recommend against targeting exclusively a single demographic group (i.e., large female trees) due to potential negative impacts on species demography and bark supply. A grounded strategy for sustaining bark harvest would also need to take into account relevant aspects of local socio-ecological context, including harvest interactions with other land uses.

Assessment of above-ground biomass and carbon loss from a tropical dry forest in Mexico

Primary forests in seasonally dry tropical regions have undergone intense land-use/cover change, ranging from widespread shifting agriculture to land clearing for livestock production systems, and selective logging. Despite the importance of tropical dry forests (TDF), little is known about the implications of carbon (C) emissions from deforestation in local, national, and global scales. Therefore, the main objective of this study is to quantify and understand the processes that drive major C losses of this ecosystem in Mexico. Also, we evaluated the applicability of the already published above ground biomass (AGB) maps to quantify and allocate changes in C stocks. The results suggest that biomass maps can be used to capture the patterns of AGB distribution and to identify the driving forces of C emissions. The C losses are more related to socioeconomic drivers than biophysical characteristics like topography and climate. Besides, this study shows that published current AGB maps may be used for landscape management, including conservation and restoration areas.

Multiple Factors Influence Seasonal and Interannual Litterfall Production in a Tropical Dry Forest in Mexico

Litterfall production plays a fundamental role in the dynamics and function of tropical forest ecosystems, as it supplies 70–80% of nutrients entering the soil. This process varies annually and seasonally, depending on multiple environmental factors. However, few studies spanning several years have addressed the combined effect of climate variables, successional age, topography, and vegetation structure in tropical dry forests. In this study, we evaluated monthly, seasonal, and annual litterfall production over a five-year period in semideciduous dry forests of different successional ages growing on contrasting topographic conditions (sloping or flat terrain) in Yucatan, Mexico. Its relationship with climate and vegetation structural variables were also analyzed using multiple linear regression and generalized linear models. Litterfall was measured monthly in 12 litterfall traps of 0.5 m2 in three sampling clusters (sets of four 400 m2 sampling plots) established in forests of five successional age classes, 3–5, 10–17, 18–25, 60–79, and >80 years (in the latter two classes either on slopping or on flat terrain), for a total of 15 sampling clusters and 180 litterfall traps. Litterfall production varied between years (negatively correlated with precipitation), seasons (positively correlated with wind speed and maximum temperature), and months (negatively correlated with relative humidity) and was higher in flat than in sloping sites. Litterfall production also increased with successional age until 18–25 years after abandonment, when it attained values similar to those of mature forests. It was positively correlated with the aboveground biomass of deciduous species but negatively correlated with the basal area of evergreen species. Our results show a rapid recovery of litterfall production with successional age of these forests, which may increase with climate changes such as less precipitation, higher temperatures, and higher incidence of hurricanes.

Management strategies, silvopastoral practices and socioecological drivers in traditional livestock systems in tropical dry forests: An integrated analysis

Understanding traditional livestock management is essential in the design of more sustainable systems, given the forest loss associated to the growing demand for meat. In Latin America, where extensive livestock production is increasing, along with tropical dry forest (TDF) transformation, the role of small holders is critical for designing more sustainable management practices. This study is an integrated socioecological analysis of traditional livestock systems in a region with TDF in Mexico. The objectives were to: a) characterise the historical development and current state of livestock systems and silvopastoral practices, b) define the management strategies and their impacts on forests, and c) identify the regional and local socioecological drivers that influence decision-making processes in livestock and forest management. In-depth interviews were carried out to 32 cattle farmers and analysed using a qualitative-interpretative approach which included multivariate and narrative analyses. Three historical stages (colonization, promotion of livestock and forest conservation) had a strong impact in the development and current state of livestock systems. Access to natural and economic resources and proportion of plant cover (grassland/forest) were essential in defining four groups of management strategies. The main regional drivers favouring or restricting production include climate, native vegetation, markets and public policies; at the local scale, socioecological factors, such as water availability, native vegetation, economic assets, local knowledge and their interactions determine heterogeneity in management strategies, decision-making processes and their impacts on forests. Adaptive management of livestock and forests in a context of limited economic resources has allowed the conservation of forest areas and the use of silvopastoral practices with local tree species. The integrated socio-ecological approach and the use of mixed methods allowed a better understanding of drivers and their interrelationships, the local knowledge, objectives and perceptions of farmers in the decision-making processes regarding livestock and forest management. Perspectives of farmers on resource use can contribute to the design of more effective and inclusive policies for sustainable livestock systems in the dry tropics.

Thermal ecophysiology of a native and an invasive gecko species in a tropical dry forest of Mexico.

For ectotherms, thermal physiology plays a fundamental role in the establishment and success of invasive species in novel areas and, ultimately, in their ecological interactions with native species. Invasive species are assumed to have a greater ability to exploit the thermal environment, higher acclimation capacities, a wider thermal tolerance range, and better relative performance under a range of thermal conditions. Here we compare the thermal ecophysiology of two species that occur in sympatry in a tropical dry forest of the Pacific coast of Mexico, the microendemic species Benedetti's Leaf-toed Gecko (Phyllodactylus benedettii) and the invasive Common House Gecko (Hemidactylus frenatus). We characterized their patterns of thermoregulation, thermoregulatory efficiency, thermal tolerances, and thermal sensitivity of locomotor performance. In addition, we included morphological variables and an index of body condition to evaluate their effects on the thermal sensitivity of locomotor performance in these species. Although the two species had similar selected temperatures and thermal tolerances, they contrasted in their thermoregulatory strategies and thermal sensitivity of locomotor performance. Hemidactylus frenatus had a higher performance than the native species, P. benedettii, which would represent an ecological advantage for the former species. Nevertheless, we suggest that given the spatial and temporal limitations in habitat use of the two species, the probability of agonistic interactions between them is reduced. We recommend exploring additional biotic attributes, such as competition, behavior and niche overlap in order assess the role of alternative factors favoring the success of invasive species.

The new genus Jocatoa (Lecanoromycetes: Graphidaceae) and new insights into subfamily Redonographoideae

One new genus and two new species of Graphidaceae are described from tropical dry forests of Mexico, based on morphological and molecular data of the mtSSU, nuLSU and ITS markers. The new genus Jocatoa in subfamily Graphidoideae is described to accommodate the species Graphis agminalis (syn.: Medusulina texana), previously known from Colombia and North America. The new genus resembles Diorygma but differs by having simple paraphyses tips that do not form an epithecium. Jocatoa agminalis is similar to Diorygma monophorum but differs by having larger ascospores, hypostictic and stictic acids and by the type of paraphysis tips. In subfamily Redonographoideae, the two new species Gymnographopsis corticicola and Redonographa parvispora are described, representing the first corticolous species in the subfamily. Gymnographopsis corticicola is characterized by the smallest spores in the genus, the presence of norstictic acid, and a rectangular perispore that appears to be a newly recognized character state in fungi. Redonographa parvispora is characterized by warty periphysoids, small ascospores with 3 transverse septa, and norstictic acid. It also frequently develops a rectangular perispore. We present a phylogenetic analysis, based on the markers mtSSU, nuLSU and RPB2, that includes all the genera in the family Graphidaceae, with available sequences, to accommodate the new genus and to validate for the first time the position of Gymnographopsis. Diagnostic anatomical and ecological characters are discussed for Redonographoideae. Gymnographopsis is newly reported to the Northern Hemisphere.

Anthropogenic and hurricane disturbances had similar negative effects on epiphytic Tillandsia species in a tropical dry forest

The distribution of epiphytes in tropical dry forests has been associated with the availability and traits of their phorophytes. Thus, strong disturbances of the phorophyte community are expected to affect the abundance and composition of epiphytes. Here, we address the effects of anthropogenic and hurricane disturbances on the richness and abundance of Tillandsia species in a tropical dry forest of Mexico. Tillandsia species were sampled at sites corresponding to early, intermediate, and late stages of succession in 2007 and 2016, before and after two successive large hurricanes, Jova (October 2011; Category 2) and Patricia (October 2015; Category 5). Tillandsia species richness and abundance were greater in the late successional stage compared with intermediate and early stages, which did not differ from each other. In addition, both richness and abundance were positively correlated with the abundance of large trees. Tillandsia species richness and abundance were greater before than after hurricanes. We conclude that only old-growth forests or secondary forests in late successional stages can support large populations of Tillandsia species, probably because their recovery time is dependent on the presence of large host trees that provide higher quality substrates. Our results also demonstrated that catastrophic hurricane disturbances are important density-independent factors that decrease the species richness and abundance of Tillandsia epiphytes in tropical dry forests.

Seasonal diversity of Cerambycidae (Coleoptera) is more complex than thought: evidence from a tropical dry forest of Mexico.

Global climate change is expected to affect temperature and precipitation patterns worldwide, which in turn is likely to affect insect phenology, distribution and diversity. To improve our understanding of such processes, it is important to understand how insects may respond to changes in seasonality, and how these affect their activity, patterns of distribution and species richness. The tropical dry forest (TDF) is a highly seasonal ecosystem, for which two seasons are commonly described (rainy and dry) and there is a lack of information on the combined effect of both precipitation and temperature on the insect communities. In order to evaluate the seasonal patterns in the community of Cerambycidae in a TDF, historical climatic variables were obtained, and an annual sampling of the family was carried out, using three collection techniques. We found that the Cerambycidae family showed a more complex response to climate, than simply the rainy and dry season of the year. The relationship between diversity and composition of cerambycids with changes in temperature and precipitation showed four seasonal communities which were synchronized with phenological processes of the TDF. Climate change could reduce biodiversity, causing seasonal patterns to lose complexity, either because the climatic characteristics of a season disappear and/or because the duration of a season expands, these changes will modify the ecological processes of the TDF, since they would generate changes in the flora and fauna associated with the different seasons.

Assessing the accuracy of detected breaks in Landsat time series as predictors of small scale deforestation in tropical dry forests of Mexico and Costa Rica

Tracking the occurrence of deforestation events is an essential task in tropical dry forest (TDF) conservation efforts. Ideally, deforestation monitoring systems would identify a TDF clearing with near real time precision and high spatial detail, and alert park managers and environmental practitioners of illegal forest clearings occurring anywhere in a region of interest. Over the past several years there have been significant advances in the design and application of continuous land cover change mapping algorithms with these capabilities, but no studies have implemented such methods over human dominated TDF environments where small–scale deforestation (<5 ha) is widespread and hard to detect with moderate resolution sensors. The general objective for this research was to evaluate the overall accuracy of the BFASTSpatial R Package for detecting and monitoring small-scale deforestation in four sites located in tropical dry forest landscapes of Mexico and Costa Rica using greenness and moisture spectral indices derived from Landsat time series. Results show a high degree of spatial agreement (90%–94%) between the distribution of TDF clearings occurred during the 2013–2016 period (as indicated by VHR imagery interpretation) and BFASTSpatial outputs. NDMI and NBR2 had the best performance than other indices and this is evidenced by the combined overall, user's and producer's accuracies. In particular, NBR2 were the most accurate predictor of deforestation with an overall accuracy of 94.5%. Our results also imply that monitoring sites at an annual basis is feasible using BFASTSpatial and LTS, but that lower confidence should be given to sub-annual products given significant systematic temporal differences between the BFASTSpatial monthly product and reference data. The possibility of including more clear observations at the spatial resolution of Landsat (30-m) or higher will greatly increase the spatial and temporal accuracies of the method. Given its performance, BFASTSpatial can help monitor hotspots of small-scale TDF loss across Central and North America at little or no cost. Users of the method should have a strong knowledge of the local land use and land cover dynamics and the ecophysiology of vegetation types present in the landscape. This local expertise is necessary for interpreting and validating results as well as communicating its output to decision-makers and stakeholders.

Linking social–ecological knowledge with rural communities in Mexico: lessons and challenges toward sustainability

AbstractFor decades, ecologists have stressed the need to establish and strengthen the exchange of knowledge between scientists and different stakeholders in order to construct better management practices that mitigate or provide solutions to environmental problems. Using a framework that links knowledge generation with social appropriation processes, we present an 18 yr’ experience of social–ecological research and outreach activities carried out in a place where scientists have generated a great amount of knowledge: the Chamela Biological Research Station. This site was created in 1971 as a place for research, teaching, and to conserve tropical dry forests in Mexico, and it has played a relevant role in the advancement of tropical science as well as in undergraduate and graduate education. For many years, researchers and students from Mexico and many other countries have used the facility that is part of the National Autonomous University of Mexico. Here, we measured the extent to which social–ecological knowledge responds to information needs of rural people and found that very little of it has been shared with the local inhabitants. Local needs regarding pasture and forest management are covered by local people's own knowledge. In order to help bridging the gap between social–ecological knowledge and rural inhabitants, we describe and evaluate ongoing communication and educational projects. We propose a model that shows how knowledge generation, exchange, and use processes can be linked to facilitate the work of scientists and their institutions. Our aim is that the experience contributes to promote and strengthen linkage processes between scientists and rural people around the world in order to better transit toward sustainable social–ecological systems.

Occurrence of termites (Isoptera) on living and standing dead trees in a tropical dry forest in Mexico.

Termites play a key role as ecosystem engineers in numerous ecological processes though their role in the dynamics of wood degradation in tropical dry forests, particularly at the level of the crown canopy, has been little studied. In this study, we analysed the occurrence of termites in the forest canopy by evaluating the density and proportion of living and standing dead trees associated with termites in deciduous and riparian habitats of the tropical dry forest in Chamela, Mexico. The results indicated that 60–98% of standing dead trees and 23–59% of living trees in Chamela were associated with termites. In particular, we found that the density of standing dead trees was higher in deciduous forests (0.057–0.066 trees/m2) than in riparian forests (0.022 and 0.027 trees/m2), even though the proportion of trees was not significantly different among habitats. Additionally, we found a higher density of trees associated with termites in trees of smaller size classes (0.01–0.09 trees/m2) than in larger class sizes (0–0.02 trees/m2). Interestingly, 72% of variation in the density of trees associated with termites is explained by the density of standing dead trees. Overall, these results indicate that standing dead tree availability might be the main factor regulating termite populations in Chamela forest and suggest that termites could play a key role in the decomposition of above-ground dead wood, mediating the incorporation of suspended and standing dead wood into the soil.