Oak Forests In Mexico Research Articles

Thelephora pacifica (Basidiomycota: Thelephorales), a new species of the tropical forests in the Mexican Pacific coast

Thelephora is a genus of ectomycorrhizal fungi distributed in angiosperm and gymnosperm forests around the world. In this study, we describe Thelephora pacifica, a new species associated with tropical oak forests in Mexico. Phylogenetically, it is the sister group of T. pseudoganbajun from China. Morphologically, it corresponds to T. vialis previously reported in Mexico. Thelephora pacifica has a flabelliform basidiocarp with a hymenophore of grayish-brown color with pinkish tinges contrasting with the yellowish-olive margin. It is distributed in the Pacific forests of Mexico, an area with a high potential for endemism.

The Pine-Oak Forest of the Rio Conchos Basin, Mexico: Key to Rain Production and Soil Erosion Control

Under the current climate crisis, the ecological integrity of forest ecosystems is key to increasing resilience and the sustainability of water and soil resources. Most forests around the world have experienced deforestation and degradation in the past few decades; however, the rate at which these occur varies depending on many factors, including the type of trees, management, and climate. We conducted a review of the deforestation, degradation, and soil erosion of the pine-oak forest within the Rio Conchos basin in northern Mexico. Preference was given to recent studies (last 10 years) conducted within this basin. Out of 27 recent publications on oak forests in Mexico, 19 focused on this forest and half of them were in Spanish. The results show that pine trees are more affected than oak trees, also that the deforestation rate has increased with time and is greater at higher elevations, making this area vulnerable to loss of topsoil during extreme hydrological events. Studies report an annual change in cover rate between 1985 and 2016 of −1.2% for pine, oak and mix vegetation. More recently, between 2000 and 2018, the change in pine cover was calculated as −2.8% concurrent with a +3.4% increase in cover of oak and other secondary vegetation. Proposed conservation strategies vary from runoff control to increased collaboration between landowners, government agencies, and stakeholders.

Dispersal of Dioon edule cycad seeds by rodents in a tropical oak forest in Mexico

Predation of seeds of the cycad Dioon edule Lindl. by Peromyscus mexicanus (Saussure, 1860) has been previously documented, demonstrating that the seeds’ toxins are not harmful when combined with a varied diet. However, there is scarce evidence of P. mexicanus as a seed disperser. In a tropical oak forest in San Luis Potosí, Mexico, we experimented with seeds of D. edule and Quercus polymorpha Schltdl. & Cham., evaluating predators’ preference and recording it with photo-trapping. Burrows were sampled in concentric circles around a D. edule mother plant, and the types of burrows and condition of the seeds inside were identified with a borescope without destroying the burrows. The structure and composition of the forest were evaluated. The primary dispersion of D. edule seeds is by barochory. The rodents predate on seeds and prefer Q. polymorpha over D. edule (survival: 48.9% and 78.5%, respectively). There are more escape and multiple burrows at 3–6 m with mature oaks. Rodents forget or abandon D. edule seeds in the burrows, and such seeds germinate at 3–6 m. Peromyscus leucopus (Rafinesque, 1818) is a short-distance secondary disperser and predator of Dioon edule seeds.

Restoration interventions produce opposite and non‐additive benefits on tree establishment in degraded forest clearings

The natural regeneration of forests is declining in human‐modified landscapes and overcoming ecological barriers to the seedling establishment is paramount to its restoration. This study focus on two common forest regeneration barriers: excessive sun exposure and low‐quality soils. A degraded clearing with eroded and compacted soils within a disturbed oak forest in Mexico was chosen, and 20 experimental plots in a randomized factorial block design were set up to test seedling performance in the artificial shade and in forest topsoil that was transferred from a nearby remnant forest, as well as a combination of both. We sowed 400 acorns from two oak species (Quercus eduardii and Q. viminea) and monitored the emerging seedlings for 63 months. Our results confirm different survival and growth rates between species, ontogenetic stages, and environmental micro‐conditions. The effect of artificial shade on seedling performance was positive in weathered soil but negative or neutral in transferred forest soil. Restoration interventions did not have additive benefits; seedling performance was improved by both restoration interventions applied separately though was not further enhanced when both actions were combined. Both species had different mechanisms to cope with water stress, which resulted in different photosynthetic rates under full sun. Trade‐offs resulted in different life stages that were more enhanced by different restoration strategies; survival and growth were most enhanced by applying artificial shade or transferring forest topsoil, respectively. Restoration practitioners may prioritize seedling survival in harsh conditions and growth in less severe degraded sites or apply interventions sequentially over time.

Diversity and niche differentiation of a mixed pine–oak forest in the Sierra Norte, Oaxaca, Mexico

AbstractThis study examined tree species diversity, distribution, and community differentiation patterns along an elevation gradient in pine–oak forest in the Sierra Norte mountains in Oaxaca, Mexico. Pine and oak are ecologically and economically valuable both locally and globally, but their dynamics are poorly understood in seasonally dry montane forests. This is a biome that is both widespread, with high human use and importance, and widely understudied. The community‐managed forest we studied contained high levels of tree diversity (32 total species), with especially high levels of oak (10 species) and pine (eight species) diversity compared to other pine–oak forests in Mexico. Tree communities in the study area demonstrated high levels of species turnover across sites, especially at mid and low elevations, as well as high levels of oak species coexistence within communities, with a mean of three oak species per 1000 m2. We identified three distinct tree vegetation types using multivariate ordination and cluster analyses and found that both tree distributions and community assemblages are primarily differentiated by elevation, but also by soil type, topography, and likely successional disturbance from historical land use. Oak communities in the study area followed patterns of phylogenetic overdispersion with species from different sections (red and white) co‐occurring more frequently than species from the same section, and demonstrated differences in reported reproductive phenology, with coexisting species alternately fruiting in rainy and dry seasons. This differentiation in both oak species' environmental associations and in fruiting phenology has important management and conservation implications as Mexico becomes more arid with climate change. This study also provided key information for local management as different forest types should have different silvicultural management regimes, as well as essential baseline data useful for a broader theoretical understanding of how closely related species coexist in communities.

Recent dynamics of pine and oak forests in Mexico

Temperate forests worldwide are dominated by two families, Pinaceae and Fagaceae. In the last decades, temperate forests are experiencing rapid changes and, in some regions, a directional increase in Fagaceae abundance at the expense of Pinaceae has been detected. Here, we analyze the recent forest dynamics of Pinaceae and Fagaceae in Mexican forests to assess whether there is a directional change in the relative abundance of these two families and identify the environmental factors that are determining their recent growth dynamics. We take advantage of repeated surveys data from the Mexican National Forest and Soil Inventory, obtained in 2004–2007 and 2009–2014. Our results show that, at present, there is no overall directional trend in the changes of the relative abundance of Pinaceae and Fagaceae in the temperate forests of Mexico, which likely reflects a complex mixture of forest dynamics, locally dominated by different types of disturbance or successional dynamics. At the same time, however, we find evidence that the growth of Fagaceae species is responding more favorably than that of Pinaceae to currently rising temperatures in Mexico. Although these results need to be confirmed by longer-term studies, the resulting changes in composition could potentially have strong impacts on forest ecosystem function in the midterm.

Direct and legacy effects of plant-traits control litter decomposition in a deciduous oak forest in Mexico.

BackgroundLitter decomposition is a key process in the functioning of forest ecosystems, because it strongly controls nutrient recycling and soil fertility maintenance. The interaction between the litter chemical composition and the metabolism of the soil microbial community has been described as the main factor of the decomposition process based on three hypotheses: substrate-matrix interaction (SMI), functional breadth (FB) and home-field advantage (HFA). The objective of the present study was to evaluate the effect of leaf litter quality (as a direct plant effect, SMI hypothesis), the metabolic capacity of the microbial community (as a legacy effect, FB hypothesis), and the coupling between the litter quality and microbial activity (HFA hypothesis) on the litter decomposition of two contiguous deciduous oak species at a local scale.MethodsTo accomplish this objective, we performed a litterbag experiment in the field for 270 days to evaluate mass loss, leaf litter quality and microbial activity in a complete factorial design for litter quality and species site.ResultsThe litter of Quercus deserticola had higher rate of decomposition independently of the site, while the site of Quercus castanea promoted a higher rate of decomposition independently of the litter quality, explained by the specialization of the soil microbial community in the use of recalcitrant organic compounds. The Home-Field Advantage Index was reduced with the decomposition date (22% and 4% for 30 and 270 days, respectively).DiscussionWe observed that the importance of the coupling of litter quality and microbial activity depends on decomposition stage. At the early decomposition stage, the home-advantage hypothesis explained the mass loss of litter; however, in the advanced decomposition stage, the litter quality and the metabolic capacity of the microbial community can be the key drivers.

A δ(15)N assessment of nitrogen deposition for the endangered epiphytic orchid Laelia speciosa from a city and an oak forest in Mexico.

Atmospheric nitrogen deposition poses a major threat to global biodiversity. Tropical epiphytic plants are especially at risk given their reliance on atmospheric sources of nutrients. The leaf, pseudobulb, and root carbon and nitrogen content, C:N ratio, as well as the nitrogen isotopic composition were studied for individuals of Laelia speciosa from a city and from an oak forest in Mexico. The nitrogen content of leaves was similar between the city and the oak forest, reaching 1.3±0.2% (dry mass). The δ(15)N of leaves, pseudobulbs, and roots reached 5.6±0.2‰ in the city, values found in sites exposed to industrial and vehicular activities. The δ(15)N for plant from the oak forest amounted to -3.1±0.3‰, which is similar to values measured from sites with low industrial activities. Some orchids such as Laelia speciosa produce a single pseudobulb per year, i.e., a water and nutrient storage organ, so the interannual nitrogen deposition was studied by considering the ten most recent pseudobulbs for plants from either site formed between 2003 and 2012. The C:N ratio of the ten most recent pseudobulbs from the oak forest, as well as that of the pseudobulbs formed before 2010 for plants in the city were indistinguishable from each other, averaging 132.4±6.5, while it was lower for the two most recent pseudobulbs in the city. The δ(15)N values of pseudobulbs from the oak forest averaged ‒4.4±0.1‰ for the entire series. The δ(15)N ranged from 0.1±1.6‰ for the oldest pseudobulb to 4.7±0.2‰ for the pseudobulb formed in the city from 2008 onwards. Isotopic analysis and the C:N ratio for L. speciosa revealed that rates of nitrogen deposition were higher in the city than in the forest. The δ(15)N values of series of pseudobulbs showed that it is possible to track nitrogen deposition over multiple years.

Effects of burial depth on seed germination and seedling emergence of Mexican oaks: A glasshouse experiment

Despite the interest in restoring oak forests in Mexico, very little is known about their regeneration ecology. We assessed the influence of acorn burial depth on seed germination and seedling emergence for eight Mexican oak species (Q. affinis, Q. castanea, Q. coccolobifolia, Q. laeta, Q. mexicana, Q. polymorpha, Q. tinkhamii and Q. viminea). We performed a glasshouse experiment in which acorns were buried at five soil depths (0, 2, 4, 6 and 8 cm). After four months, acorn germination and seedling emergence were recorded. Buried acorns showed higher germination and seedling emergence than unburied ones, but burial depth also influenced these responses. The optimum burial depth for seedling emergence of each species was 2, 4, 6 and 8 cm depth for four species (Q. castanea, Q. mexicana, Q. tinkhamii, and Q. viminea); 2 and 4 cm for Q. laeta; as well as 2, 4 and 8 cm for Q. coccolobifolia.

The root colonizing fungi of the terrestrial orchid Cypripedium irapeanum

Este estudio investigó el status micorrízico y la identificación de los hongos que colonizan la raíz de la orquídea terrestre Cypripedium irapeanum por medio de los polimorfismos de los fragmentos de la restricción y la secuenciación del espacio tránscrito interno del rDNA. Esta orquídea es endémica de diferentes regiones de México, Guatemala y Honduras localizándose entre los 1400 y 2250 m de altitud. Crece principalmente en los remanentes de los bosques de encino del altiplano y está en la lista roja de México de las plantas amenazadas. Los bosques de encino en este país están constantemente amenazados. El examen al microscopio de los segmentos de raíces teñidas de las orquídeas nos mostró la presencia de estructuras fúngicas tanto de hongos de micorriza orquidoide (pelotones e hifas enrrolladas) como de los llamados endófitos obscuros septados (DSE) (hifas mielinizadas y microesclerosios). El análisis de la secuenciación de la región ITS1-5.6-ITS2 sugiere que el tejido micorrizado está dominado por Tulasneaceae: Sistotrema sp., Rhizoctonia solani, and Epulorhiza sp. Entre los DSE, uno de los 10 aislados mostró 100% de similaridad con Phomopsis sp XJ-05, y otro 99% con el endofito MUT 885, ambos reportados como endófitos obscuros septados. El hipotético endófito septado obscuro Phomopsis sp XJ-05 fue aislado tanto de las raíces como de las semillas que germinaron de C. irapeanum restriction fragment length polymorphisms and by rDNA internal transcribed spacer sequencing.

Edge type effect on germination of oak tree species in the Highlands of Chiapas, Mexico

The purpose of this study was to examine the effect of habitat edges on the probability of acorn germination of three oak species ( Quercus crassifolia Humb. and Bonpl., Quercus rugosa Née and Quercus laurina Humb. and Bonpl.). The effects of edge type (hard and soft), habitat type (grassland, edges and forest) and leaf litter cover (covered or uncovered acorns) on acorn germination was evaluated by the experimental establishment of acorns along transects crossing habitat edges. More acorns developed into seedlings in grasslands (38%) than in the forest edge (18%) or the forest interior (15%). In sites with soft edges, a higher number of seedlings emerged from acorns covered by litter compared with acorns sowed in the adjacent forest edge and forest interior ( P < 0.05). In sites with hard edges, fewer seedlings emerged in the edge (14%) compared with the adjacent grassland (38%), and the adjacent forest (20%) presented intermediate values. However, in sites with soft edges significant differences in seedling emergence were recorded between the grassland (38%) and the forest (10%), whereas the edge presented intermediate values (23%). The effect of leaf litter cover on acorn germination was only significant in grasslands in sites with soft edges ( P < 0.05). Acorns in grasslands received relatively little insect damage (10%) compared with the edge (19%) and the forest (30%, P < 0.05), emphasising the importance of acorn dispersal for successful oak establishment. The implications for regeneration of these oak species and the dynamics of montane oak forests in Mexico are discussed.

Environmental influences on post-harvest natural regeneration in Mexican pine–oak forests

Pine–oak forests in Mexico’s Sierra Madre Occidental are increasingly harvested for industrial wood production, but few studies have investigated post-harvest stand dynamics or natural regeneration. The influence of environment, harvest year and stand location on natural regeneration was studied in 27 post-harvest and two undisturbed stands in the Madrean pine–oak forest of Durango state. Multivariate analyses showed that local environmental factors, including surface fires, continue to structure tree seedling communities more strongly than harvesting. Environmental factors explained 50% of the species variance while year of harvest and the spatial distribution of stands explained 13 and 7%, respectively. Regeneration of Pinus durangensis, P. teocote and Quercus crassifolia was more abundant on sloping sites with stony soils and low vegetation cover that had experienced recent surface fires. Quercus sideroxylla, Juniperus deppeana, P. leiophylla and P. cooperi were favoured on valley bottom sites with deeper, fine-textured soils. Although stand spatial distribution had a minor role in structuring seedling communities, spatial autocorrelation in the distributions of single height classes of P. durangensis and P. teocote may account for some of the species variance that was explained by harvest year. The topographic and soil factors that influence the species composition of natural regeneration in stands may also modify fire frequency and intensity, and thus affect seedling establishment. Thus, while current logging practices in the Sierra Madre allow natural regeneration to continue, Mexican foresters should consider incorporating natural disturbance regimes into their management practices.