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Tropical timber regions across the world share common problems such as degradation and poor regeneration after timber harvesting. Traditional Mayan land management through slash and burn is now recognized as an effective way of renewing forest stands in multispecies tropical forests. The practice of slash and burn for forest management in Mexico has led to area regulation, which has made land value a convenient means of assessing alternative forest plans. The use of expected land value as a performance indicator shifts the manager's attention from managing a species mix to balancing financial tradeoffs between liquidation or retention of the standing biomass. Since the forest-wide residual stock is so large, land value overrides the importance of revenue from timber sales. Several forest management methods along these lines have appeared in tropical regions of Mexico over a thirty-year time span and represent a patrimonial system of forest management (PS). The gradual innovation generated by PS is described here, as well as examples of PS practices. PS methods today provide stewardship for a total of 155,814 ha in different parts of Mexico. PS performance will become evident in the long run; in the meantime, the embrace of PS by private landowners and regulatory institutions is equated with a positive, independent opinion about PS design. The Mexican experience suggests pathways for rational management of all types of forests. PS features that are worth replicating are, for instance, the inclusion of disturbance patterns as factors in decision making, as well as the use of specific silvicultural regimes for roads, woodlands, closed forests, hilltops, swamps, riparian zones, clearings and forest edges.

Aunque muchos árboles tropicales se extraen con fines comerciales, son escasas las investigaciones que han abordado el estudio de su regeneración, tasas de crecimiento y las técnicas sustentables para su aprovechamiento. La carencia de este tipo de información representa una de las mayores debilidades de los programas de manejo forestal, en las regiones tropicales de méxico. Lo anterior se refleja, por ejemplo, en que la caoba (Swietenia macrophylla) y el cedro (Cedrela odorata) están cada vez menos disponibles en las selvas de Quintana roo. un efecto secundario de la disminución del volumen del cedro y la caoba es el incremento del número de las especies susceptibles de aprovecharse, y los volúmenes que de ellas se cosechan; tal es el caso del tzalam (Lysiloma latisiliquum), por lo que el objetivo del presente estudio fue contribuir al conocimiento sobre el crecimiento y la regeneración del tzalam, mediante la evaluación de 74 árboles entre 2002 y 2008 (en una selva sujeta a manejo comercial). se obtuvo una tasa de crecimiento anual de 0.41 cm y la ausencia de individuos con daP entre 2 y 10 cm, en 176 sitios de 30 m2. del total de ejemplares muestreados 84% se localizaron en suelo negro, que representa solamente 5% de los suelos de la selva estudiada. el futuro comercial sustentable del tzalam está muy amenazado, por la falta de plantas con daP de 2 y 10 cm.

Conservation professionals are increasingly called on to adopt democratic approaches that integrate public concerns and diverse societal voices yet are not taught how to do so. We use a case study approach to analyze a 3-year graduate learning initiative piloted in Mexico by Universidad Veracruzana and the University of Florida that sought to fill this gap. Two team-taught courses were integrated with multiple field and on-campus experiences (e.g., stakeholder simulations, community dissemination events, scholar-practitioner workshops, a student exchange forum), pedagogically modeling the collaborative leadership needed to address current conservation challenges. Our analysis highlights individual student and institutional impacts, drawing on systematic reflections, an external evaluation, and a student survey administered 3 years after the initiative ended. Through methodical learning opportunities, students incrementally and systematically developed skills and confidence. Their conceptualization of leadership shifted as they preferentially referred to themselves as agents of change (versus leaders), working across disciplines and collectively with multiple social actors. Students highlighted the following learning impacts: the strength of diversity across disciplines and individuals, individual and collective learning, intertwined professional and personal growth, and a new concept of conservation leadership. The university-to-university collaboration continues through multiple joint activities. Maintaining institutional support and instigating administrative change toward a democratization of educational processes is a slow and delicate proposition, yet it occurred. Finally, we emphasize integration of training to manage conflict and collaboration into conservation education as well as constant reflection to appropriately redirect programs.

Se definen las características necesarias para el manejo forestal maderable visto como la gestión responsable de bienes raíces con intenciones patrimoniales, que aquí se designa como sistema patrimonial. El método silvícola peninsular (MSP) es uno de varios modos de recrear esta definición teórica del manejo forestal con fines patrimoniales. El estudio plantea que el MSP está diseñado para lograr niveles de capitalización del valor del predio superiores al común de los métodos de manejo forestal usados en México. Las cualidades del sistema patrimonial se ejemplifican a partir de un programa de manejo forestal autorizado con MSP para el ejido Kankabchen, Quintana Roo, México. Dichas cualidades se comparan, para fines de ilustración, con la forma de manejo previo. Si el manejo forestal actual fuese continuación del aprovechamiento maderable anterior no habría consideraciones económicas que vigilen el desempeño financiero, pero las proyecciones que resultan de los datos de remoción indican un deterioro del valor predial que, comparado con lo esperado de aplicar el sistema patrimonial, es una merma innecesaria del patrimonio del ejido. El ejemplo del ejido Kankabchen muestra que el sistema patrimonial es una forma responsable de gestión de los bienes raíces del propietario del bosque, a la vez que mejora su estructura y mantiene conformidad con la normatividad forestal mexicana.

La reforestación en México es importante para recuperar la producción de las áreas deforestadas y degradadas y para mantener la de los bosques comerciales. Sólo 40% de la reforestación tienen un nivel aceptable de supervivencia. Las características de las plántulas que se utilizan, incluyendo la relación tallo/raíz de la plántula, deben tomarse en cuenta para lograr los resultados deseados (alta supervivencia y buen crecimiento en campo). Se describen las características de plántulas de Swietenia macrophylla King, Cedrela odorata L. y Tabebuia rosea ( Bertol.) DC bajo dos densidades (100 y 50 plantas/m2) y dos sustratos [suelo y suelo + composta (S+C)] en vivero. El tratamiento S+C tuvo un efecto significativo en el crecimiento del diámetro, altura, peso de la raíz y la relación tallo/raíz de cada una de las especies. En suelo 76% de las plántulas tienen la relación tallo/raíz =< 3 y en S+C 21 % presentaron una relación tallo/raíz < 3. Para coníferas se recomienda tallo/raíz 2:1 para sitios secos y 4:1 para húmedos. Para las latifoliadas no se sabe cual es la relación tallo: raíz óptima. Dos meses después de llevarlas a campo, murieron más plántulas de Swietenia en S+C pero menos plántulas de Cedrela y Tabebuia. De las tres especies murieron las más pequeñas.

Despite regional deforestation threats, the state of Quintana Roo has maintained over 80% of its territory in forests. Community forest management (CFM) has played a pivotal role in forest cover and biodiversity conservation in the region. In this article, we present the institutional, socioeconomic and environmental conditions under which community-based forest management has been consolidated in the tropical state of Quintana Roo, which occupies the eastern half of Mexico’s Yucatan Peninsula. With a focus on management for timber and other market-based development strategies, we then examine the institutional and socioeconomic factors, as well as biophysical shocks, that have constrained community forestry development in the past 25 years, challenging its persistence. Following, we discuss how forest communities and institutions have responded and adapted to changing forest policies and markets as well as major environmental shocks from hurricanes and fires. CFM in Quintana Roo has shown resiliency since its institutionalization 30 years ago. Future challenges and opportunities include biodiversity conservation, carbon management through Reducing Emissions from Deforestation and Forest Degradation (REDD+) initiatives, market strengthening, business management training as well as the implementation of alternative silvicultural systems, particularly to manage sustainable populations of commercial timber species.

We studied succession over five years in a seasonally dry tropical forest in Quintana Roo, Mexico, following three different types of experimental disturbance (slashing and complete felling; slashing, felling and burning; and machine-clearing), each one implemented in 1996 on two 0.5 ha treatment plots. Before experimental disturbances, the floristic composition, dominance and diversity of the forest vegetation had been determined. In 1997, after treatments were applied, a second survey characterized early secondary vegetation at one year. A third survey was conducted in 2001. The 1996 vegetation composition revealed no significant differences among the six treatment plots. In 1997, floristic composition on the six treatment plots showed differences in dominance and diversity: the post-treatment vegetation on the slash/fell treatment was clearly distinct from that on the other two treatments. In 2001, differences among the plots had decreased considerably. Comparisons among seral stages revealed that one-year-old secondary vegetation differed from the pre-disturbance original vegetation, while five-year-old vegetation was similar to the original in its diversity, floristic composition and dominance. Felling alone favors species with a high resprouting capacity. The frequency of species with resprouting capacity was lower on slash/fell/burn treatments and lowest on machine-cleared plots. Results indicate that the effect of disturbance tends to decline over time and that complete clearing of small areas is effective as a silvicultural treatment to favor regeneration of valuable timber species and sustain diversity.

The management of mahogany (Swietenia macrophylla King) in the Yucatan peninsula of Mexico is based on the assumption that diameter at breast height (dbh) growth averages 0.73 cm yr 1 so mahogany will reach a harvestable dbh of 55 cm in 75 years. In 2002, transects were established in the forested area of Laguna Kana ´ in Quintana Roo, Mexico. All mahogany with a dbh > 10.0 cm were measured and marked. In 2008/2009, the trees were remeasured, and tree, soil, and site characteristics and competition around each tree were recorded. Of the 499 trees studied, average dbh growth of surviving trees was 0.22 cm yr 1 , far below the rate assumed by managers. Only 21 trees grew 0.73 cm yr 1 or more. Dbh growth was significantly correlated to initial dbh and the percentage of the soil that was Box luum, varied significantly among soil types and colors and was negatively correlated to stoniness. Growth was not significantly influenced by crown radius, basal area of competition, crown growing space, topographic position, microrelief, and soil depth (for soils 30 cm in depth or less). Mortality averaged 1% per year and was not related to initial dbh or initial commercial height. Forest management in Quintana Roo requires new science-based practices that increase the growth of standing trees and that ensure the establishment and continued recruitment of mahogany reproduction.

En la comunidad de San Pablito en la Sierra Norte de Puebla, el arbol Trema micrantha (jonote) proporciona 80 % de la corteza utilizada en la manufactura del papel amate, una de las artesanias mas importantes y conocidas de Mexico. La comunidad se dedica en su totalidad a la produccion del amate; sin embargo, el abastecimiento de corteza es irregular, insuficiente y proviene de lugares lejanos al centro productor. El presente estudio tiene tres objetivos: evaluar el interes de las personas de las comunidades vecinas para aumentar la produccion de arboles de jonote, documentar las practicas silvicolas y evaluar la tasa de crecimiento en altura y diametro del arbol. Se entrevistaron 28 personas; 40 % estan interesadas en aumentar la produccion de jonote; 20 % aplica practicas silvicolas como podas, eliminacion de sombra, trasplante de jonote y adicion de materia organica. Con base en la medicion de 396 arboles de edad conocida, el jonote puede medir 7 cm de diametro promedio en el primer ano y 16 cm a los 5 anos. Los mejores crecimientos se observaron en terrenos con pendientes menores de 70 %, altitudes entre 1,200 y 1,600 m, suelos fertiles y luz directa

Although bigleaf mahogany (Swietenia macrophylla King) is one of the most important commercial timber species in the neotropics, little is known about its site preferences in the Yucatan Peninsula. We evaluated the association of mahogany with soil characteristics using the easily observed characteristics of soil color, stoniness, and relief position. The study was conducted in a commercially managed, medium-height, semi-evergreen, dry tropical forest. A total of 609 mahogany were located along 119 km of transects established in the forest. Forest site conditions were classified in 2,464, 0.78 m2 circular plots located systematically along transects, and site conditions of mahogany along the transects were recorded for the area within 1 m radius of each tree. Mahogany preferred level sites with 93% occurring on level conditions compared to 75% for forest site plots (P < 0.001). There was also a preference for black soils (76% of mahogany versus 68% of forest site plots) and a negative preference for red soils (17% versus 27%, P < 0.001). Observed soil site preferences can improve management decisions, including where to plant mahogany and where to apply silvicultural treatments, such as liberation thinning.

Un problème clé dans la gestion de la production de bois d’œuvre est d’assurer la régénération d’espèces ayant une valeur commerciale, telles que Swietenia macrophylla King (acajou), ce qui nécessite une connaissance approfondie des espèces concernées. Cet article rend compte des résultats du semis direct de l’acajou dans trois champs cultivés sur brûlis au cours de la dernière année de culture, à Betania, dans la région de Quintana Roo au Mexique. Dans chaque champ, 121 sites de semis ont été identifiés dans une parcelle de 0,25 ha, et cinq graines ont été semées dans chacun d’entre eux. La hauteur, le diamètre et les indications de dommages causés par Hypsipyla grandella de toutes les graines germées ont été enregistrés à 2, 11, 23, 38, 45 et 58 mois après le semis. Les niveaux d’ombrage et la couleur du sol ont été notés. À 11 mois, la mortalité chez les semis qui étaient vivants à 2 mois variait d’un champ à l’autre, mais ne variait pas selon le niveau d’ombrage ou la couleur du sol. Un champ a été abandonné après 11 mois car le protocole de recherche n’avait pas été respecté. En comparant les semis vivants à 58 mois avec les semis vivants à 2 mois mais morts à 58 mois, le pourcentage de survie variait selon les champs et selon les niveaux d’ombrage, mais ne variait pas selon la couleur du sol. Le diamètre moyen des semis vivants à 58 mois a été influencé par les conditions du champ, mais n’a pas varié selon la couleur du sol ou les niveaux d’ombrage. Leur hauteur moyenne variait d’un champ à l’autre, probablement en fonction de la couleur du sol, et n’était pas influencée par les niveaux d’ombrage. Deux mois après le semis, 20 % des sites de semis avaient au moins un semis. Cinq ans plus tard, 63 % de ces semis étaient morts, laissant 7,4 % des sites de semis occupés par un semis. La hauteur des semis à 58 mois variait de 0,3 à 8 m, avec une moyenne de 2,7 m. Fait remarquable, aucun des 212 semis observés ne montrait des signes de dommages causés par H. grandella, et le coût de la technique est minime. Les champs de milpa dans leur dernière année de culture semblent être des sites prometteurs pour la régénération de l’acajou à partir de graines dans un contexte de forêt tropicale mixte.

Seeds of mahogany and Spanish cedar were planted in gaps created by harvesting railroad ties at two locations in the Yucatan Peninsula. Gaps averaged 40 m2 in area. Germination after 2 months was very low (2%) for Spanish cedar and moderately low (29%) for mahogany at the one location where it was measured, probably due to predation and fungal damage. Annual seedling mortality was 25–40%, and height growth was moderate to normal, with average height equal to 45 cm after 3 or 4 years, depending upon the location. We conclude that gaps from railroad tie harvesting are not adequate for the establishment of either species from seed. If, however, gaps created by harvesting could be concentrated into at least moderately open areas 400 m2 in area or larger, they may be useful as sites for regenerating both species.

A study of the effect of different levels of basal area removal on stand and tree growth was established in a second growth forest in Quintana Roo, Mexico. In five 0.5 ha plots (subdivided into 10 × 10 m2 plots), data were collected periodically for 15 years and used to estimate stand and diameter growth of 30 tropical forest tree species. Net basal area per hectare growth was almost 0, -0.1% yr-1. For surviving trees only, basal area growth was 1.6% per year. On the 10 × 10 m2 plots basal area growth was strongly correlated to initial basal area when only surviving trees were considered. Maximum average diameter growth rate was 0.31 cmy-1 (Swietenia macrophylla King). Most species grew relatively slowly, probably due to low quality of the site resulting from calcareous soils and low precipitation rates and possibly due to being in a relatively old second growth forest. Mortality by species during the 15 years of the study ranged from 0% to 40%. The results are contrary to information used to dev...

To mimic catastrophic disturbances which have favored the establishment of natural stands rich in mahogany ( Swietenia macrophylla ), two 5000 m 2 clearings were established in each of four locations using each of three treatments: complete felling; slashing, felling and burning; and machine-clearing, which uprooted all prior vegetation. One to three months later, and again after an additional 12 months, twenty 4-month-old mahogany seedlings were planted in the center of each clearing, and, simultaneously, nearby, under the forest canopy. One year after the first planting and again 7 months later, vines and competing vegetation were cleaned from around the seedlings on one of each type of clearing in each location. Fifty-eight months later, only 5% of mahogany seedlings survived under the canopy, as compared to 32% on felled clearings and 50% on burned or machine-made clearings. Average annual growth of seedlings planted the year clearings were opened was approximately double that of seedlings planted a year later, after natural regeneration of other species had become established. At 58 months uncleaned trees averaged 352 cm in height (and the tallest 600 cm) on burned clearings, 324 cm on machine-made clearings, and 195 cm on felled clearings. Surviving seedlings planted under the forest canopy had grown less than 30 cm during the same period. On burned and machine-made clearings the effect of cleaning on growth was not statistically significant, but on felled clearings cleaning increased growth by 120%, to rates similar to those on burned clearings. Attack by the Hypsipyla grandella shootborer was significantly affected by cleaning. After 58 months, only 12% of seedlings on uncleaned plots had been attacked, compared to 44% of seedlings on cleaned plots. Cleaning also significantly increased vines, particularly on seedlings planted the year after clearings were created: 36% of all seedlings on cleaned plots had vines, as compared to 19% of uncleaned seedlings. In summary, planting mahogany seedlings under the forest canopy cannot be expected to regenerate mahogany trees. However, mahogany seedlings survive and grow well on clearings, with no subsequent interventions, if planted shortly after these are opened by machine or burning. This approach to regeneration could be expected to yield densities of 100 commercial-sized mahogany trees/ha among a matrix of 400 naturally regenerated trees/ha of other species. At this rate, regenerating mahogany on clearings equivalent to 3% of the annual cutting area intervened at each harvest, could provide for replacement of mahogany trees harvested from the permanent forest reserves in the region.

Honduras or bigleaf mahogany (Swietenia macrophylla King) is the most commercially important timber species in the Neotropics, but it often does not regenerate successfully after harvesting. Effective methods are needed to sustain or increase mahogany yields by increasing regeneration. This study evaluates the effects of three treatments (slash, fell and burn; slash, fell and leave; and uprooting and pushing away trees using machines) used to open 0.5 ha clearings, plus a control under the forest canopy, and two sowing methods (surface-sown seed and buried seed) on the germination, establishment, survival, and early growth of mahogany. After 10 months, significantly more buried seeds yielded established seedlings (20%) than surface-sown seeds (9%), but there were no significant differences among clearing treatments. Establishment on controls averaged 18%. The percentage of seedlings that survived from 10 to 49 months varied significantly among treatments, from 53 to 54%, respectively, on the slash and burn and machine-cleared treatments to 16% on the fell and leave treatment and 26% on controls. Both slash and burn and machine-clearing reduced sprouting as compared to the fell and leave treatment, which had abundant sprouting from stumps of other species and the lowest establishment and survival of mahogany. Low survival on controls was probably due to low light levels. Forty-nine months after sowing, an average of 12% of the seeds buried in the slash and burn and machine-cleared treatments were represented by live seedlings, a rate substantially higher than on the fell and leave treatment (3%) and the control (6%). Yield from buried seeds averaged 9% as compared to 4% from surface-sown seeds. Seedling height at 49 months (average=66 cm) did not differ significantly among the clearing treatments or sowing methods, but on control plots average height of the few surviving seedlings was only 27 cm. The traditional slash and burn practice used for agricultural clearing seems to be a good way to prepare sites for seeding with mahogany and could be used as a silvicultural technique to facilitate regeneration. Consideration should be given to integrating these systems into forest management to help assure continued production of mahogany.

"Researchers concerned with sustainable management of forests in the tropics have argued that the road to improved stewardship of forest resources is the transfer of responsibility to the local communities who get their livelihoods from them. On the other hand, conservationists have declared that the only way to stem the tide of deforestation is to place as many tracts as possible under strict protection. In this context, Mexico presents a national laboratory for studying the social and ecological benefits of delivering forests to local people. As a little-noticed result of the Mexican Revolution in the second decade of the twentieth century, well over half of the forests of Mexico were placed in community-held lands. In historic struggles that passed through several phases, most of these communities have now gained substantial control over the use of their forests. Because of the substantial degree of social capital in rural forms of organization in Mexico, this control of forest resources has led to an estimated 290,479 community forest enterprises ( CFEs ), through which communities are producing timber on their own lands. New studies are beginning to suggest that important gains in both social and economic justice, good forest management, and biodiversity protection are resulting from the actions of these CFEs. As more forests globally are being devolved to local communities, it is important to carry out more research on the Mexican model of community forest management for timber production."

Tropical forests are endangered from deforestation and overexploitation. The objective of this study was to examine the effects of production practices of the tropical hardwoods, mahogany and Spanish cedar, on survival and early growth in the state of Quintana Roo, Mexico. Mahogany seedlings were grown in polybags and Spanish cedar seedlings were grown in bareroot nursery beds. In addition, seedlings of both species were grown in R–L containers for the outplanting comparison. Fertilization had a minor affect on seedling morphology, but the amount of shade had a strong affect on seedling morphology in the nursery. Following outplanting, initial seedling diameter influenced seedling survival and growth. Survival and growth of Spanish cedar was strongly correlated with initial seedling diameter. Seedlings larger than 4 mm had excellent survival and good growth. Large diameter (>5 mm) mahogany seedlings had exceptional growth, achieving over 4 m in height at 57 months There appeared to be no interaction between stocktype and performance. Polybag mahogany seedlings were larger than containerized seedlings, and grew better. Conversely, containerized cedar seedlings were larger than the bareroot seedlings and performed better. Nearly all the bareroot cedar seedlings had died by 57 months, whereas 50% of the larger containerized seedlings lived. Growth of cedar was less than one-half that of mahogany. Successful reforestation of both species can be accomplished with just small improvements in seedling quality using the conventional systems. Larger seedlings survive and grow better, and on this site, mahogany was superior in performance compared to Spanish cedar.

En Amérique tropicale, la régénération de l’acajou à grandes feuilles, Swietenia macrophylla King, essence commerciale majeure, est problématique en raison de ses caractéristiques de fructification et de dispersion et de sa faible tolérance à l’ombre et sa réaction à l’exploitation forestière. Dans l’État de Quintana Roo, au Mexique, les brûlis abandonnés offrent d’excellents espaces pour l’établissement de jeunes plants, mais un moyen effi- cace permettant d’assurer la survie des semences reste à identifier. La présente étude s’est attachée à évaluer la pro- babilité de prédation des semis directs d’acajou, en analysant les effets de trois types de traitement (quatre types de pro- tection des semences, deux méthodes de semis et deux moments de semis dans la journée). Le pourcentage moyen de semences éliminées ou consommées en partie sur une période de 12 heures varie de 1,1 à 7,7 % selon les quatre types de traitement des semences mais ne varie pas selon les deux méthodes de semis. La précipitation au moment du semis est fortement positive pour la reprise des semences, tandis que la température journalière minimale a un effet légère- ment négatif. L’effet de la date des semis, selon le calendrier julien, est positif pour la survie des semences. La prédation des semences ne varie pas selon les traite- ments de protection qui permettent l’ac- cès aux seuls rongeurs, aux seuls insectes et aux deux, et la prédation est plus importante avec ces trois types de trai- tement qu’avec le traitement interdisant totalement l’accès aux prédateurs. La pré- dation des semences n’est pas influencée par le moment du semis dans la journée. Le semis direct est favorable à la régéné- ration de l’acajou, notamment lorsque les semences sont trempées pendant au moins deux semaines avant le semis pour réduire les risques de prédation et aug- menter les chances de survie et de reprise.

Swietenia macrophylla King (big-leaf mahogany) is one of the most economically important tree species that grows in the Yucatan peninsula. While it is well known that exposure to high levels of light and low levels of competition are necessary for big-leaf mahogany establishment, conditions favoring germination have been little studied. The effect of sowing date, shade, and irrigation on germination were investigated in a nursery in Quintana Roo, Mexico. Three levels of shade (0, 63, and 80%) and two levels of irrigation (non-irrigated and irrigated 20 mm per week) were used. In addition, seed were sown on four different dates, spanning the dry season to the middle of the rainy season. Germination increased linearly with increasing shade. Irrigated seed had significantly higher germination than non-irrigated seed across all three levels of shade. Seed sown in April germinated 10 weeks after sowing, and seed sown in May and June germinated 4–5 weeks after sowing. Most seed sown in August did not germinate. Although shade does not favor establishment and growth, it may contribute to maintaining soil moisture and seed viability during germination of big-leaf mahogany.

While carrying out an overstory removal/natural regeneration study, the number of sprouts from the trees that were cut down were recorded. Seventeen species with average diameters from 9 to 36 cm were studied. The number of sprouts varied from 1 to 6, and sprout heights from 1.0 m to 5 m, 3 years after the original trees were cut. Overall, the number of sprouts and the height of the sprouts increased as the parent tree diameter increased. This information can be very useful in managing the forest for products other than timber. Firewood, medicinal plants, construction materials, edible fruits, and forages are among the different uses of the observed species. Specific stands might be coppiced to satisfy some of the most immediate needs of the region's inhabitants.

The shortened fallow period in traditional slash and burn agriculture of the Maya of Quintana Roo, Mexico, has reduced soil fertility, crop yields, biodiversity, and mature forest vegetation. Studies have shown that agroforests that mimic local ecosystem processes can be used to provide for the farmers' well-being while protecting and preserving forest resources and biodiversity. The objective of this investigation was to identify, describe, and evaluate Mayan crop plants that could be used as analog species in agroforest design. We used participant observation, interviews with farmers, and field measurements to collect information on the social, agricultural, and ecological aspects of the plants. We identified five horizontal and one vertical strata in mature homegardens: the herbaceous stratum, the low shrub stratum, the tall shrub stratum, the fruit tree stratum, the timber tree stratum, and the viny stratum. We categorized 77 forbes, shrubs, and vines identified for their temporal and spatial placement in an agroforest. The plants evaluated can be placed in one of the four developmental stages of an agroforest: the herbaceous stage, and the shrub stage, the fruit tree stage, and the timber tree stage. By using the identified plants and the analog hypothesis, we can design an agroecological system that provides for the farmers' needs, and efficiently utilizes the resources on-site for the production of food, timber, medicinal plants, and nontimber products in a manner that protects the natural resource base of the region.

Mahogany (Swietenia macrophylla King) is the single most important commercial tree species in the forests of the state of Quintana Roo, Mexico. Mahogany regeneration has been associated with natural disturbances that increase understory light levels. A study to analyze the effect of overstory removal on seed germination and early seedling survival and growth of mahogany was conducted. Twenty-five 0.2 ha plots were treated to create different levels of overstory removal and then seeded. Two seeding methods were used, dibbling and dropping. Dropping was used to simulate the way that seeding occurs in nature. Understory light levels were measured after the overstory removal was done. A year after applying the treatments, seed germination and seedling survival were not affected by the understory light levels created by the overstory removal. It is expected that over the next several years seedling survival and growth will be more affected by understory light levels. Seedling establishment by dibbling and drop...

MIGUEL N. ALEXIADES,∗ CHARLES M. PETERS,† SARAH A. LAIRD,‡ CITLALLI LOPEZ BINNQUIST,§ AND PATRICIA NEGREROS CASTILLO∗∗ ∗School of Anthropology and Conservation, Marlowe Building, University of Kent, Canterbury, Kent CT27NR, United Kingdom, email m.n.alexiades@kent.ac.uk †Institute of Economic Botany, The New York Botanical Garden, Bronx, NY 10458–5126, U.S.A. ‡People and Plants International, P.O. Box 251, Bristol, VT 05443, U.S.A. §Centro de Investigaciones Tropicales-Universidad Veracruzana, Ex-Hacienda Lucas Martin, Privada de Araucarias s/n, Col. Periodistas C.P. 91019, Xalapa, Veracruz, Mexico ∗∗Instituto de Investigaciones Forestales, Universidad Veracruzana, Parque Ecologico ‘El Haya’, Carretera antigua Xalapa-Coatepec, Xalapa, Veracruz, Mexico

A study was carried out to identify an efficient and low-cost method to kill seven tropical tree species as a means of achieving overstory removal. Four methods were tested: two chemical injection techniques (Banvel CST Herbicide and Esteron 47 M) and two physical treatments (girdling bands 20 cm and 40 cm wide). Overall, there was a substantial difference among the four treatments. Esteron 47 M was the most effective treatment, with 68% mortality. Banvel and girding 20-cm bands and 40-cm bands resulted in 57, 57 and 53% mortality, respectively. Mortality varied considerably among the species. Although girding is more time-consuming than using chemicals, it is recommended, when possible, because, of low application cost and avoidance of chemical pollution and danger to workers. Safety equipment is not readily available in tropical areas. Even if it were, it is not comfortable to use under tropical conditions. People living in the tropics are usually accustomed to the use of machete and hatchet, and accidents very seldom occur.

Aunque muchos árboles tropicales se extraen con fines comerciales, son escasas las investigaciones que han abordado el estudio de su regeneración, tasas de crecimiento y las técnicas sustentables para su aprovechamiento. La carencia de este tipo de información representa una de las mayores debilidades de los programas de manejo forestal, en las regiones tropicales de México. Lo anterior se refleja, por ejemplo, en que la caoba (Swietenia macrophylla) y el cedro (Cedrela odorata) están cada vez menos disponibles en las selvas de Quintana Roo. Un efecto secundario de la disminución del volumen del cedro y la caoba es el incremento del número de las especies susceptibles de aprovecharse, y los volúmenes que de ellas se cosechan; tal es el caso del tzalam (Lysiloma latisiliquum), por lo que el objetivo del presente estudio fue contribuir al conocimiento sobre el crecimiento y la regeneración del Tzalam, mediante la evaluación de 74 árboles entre 2002 y 2008 (en una selva sujeta a manejo comercial). Se obtuvo una tasa de crecimiento anual de 0.41 cm y la ausencia de individuos con DAP entre 2 y 10 cm, en 176 sitios de 30 m2. Del total de ejemplares muestreados 84% se localizaron en suelo negro, que representa solamente 5% de los suelos de la selva estudiada. El futuro comercial sustentable del Tzalam está muy amenazado, por la falta de plantas con DAP de 2 y 10 cm.

Los beneficios de los hongos micorrízicos arbusculares (HMA) son evidentes en la transferencia de nutrientes y en la protección contra patógenos del suelo y factores ambientales adversos a las plantas asociadas. Adicionalmente, en la actualidad se reconoce la influencia de los HMA en la conformación de la estructura y funcionamiento de los ecosistemas. Por estas razones, se han llevado a cabo gran variedad de estudios de la asociación micorrízica arbuscular en especies de importancia ecológica o agronómica, con diversidad de enfoques. Sin embargo, en las regiones neotropicales, los estudios detallados de la diversidad y funcionamiento de los HMA, especialmente aquellos vinculados con la producción y manejo de especies de importancia forestal han sido limitados. En este manuscrito se analizan las diferentes implicaciones del manejo de HMA en la producción de especies tropicales forestales, principalmente en especies de Meliáceas nativas de Latinoamérica, dentro de las que se incluyen el cedro rojo (Cedrela odorata L) y la caoba (Swietenia macrophylla K). Estas especies son altamente valoradas por la calidad de su madera, aunque el establecimiento de plantaciones comerciales y de reforestación generalmente no ha sido completamente exitoso. Por lo tanto, la inoculación de HMA debe ser un factor fundamental a considerar en el establecimiento de estas especies precedida de estudios con enfoques múltiples que aseguren su aplicación exitosa. También se discute la utilización de inóculos micorrízicos en los sistemas de producción de plantas en vivero.

In a tropical, semi-evergreen forest in Quintana Roo, Mexico, a study was conducted to observe the effects of partial overstory removal (creation of multiple gaps) on natural regeneration, with special attention to commercially valuable tree species. Five 0.5-ha plots were subjected to different levels of overstory removal of 0%, 8%, 28%, 45% and 55%. The regeneration population 3 years after overstory removal was similar in density and composition to the population before overstory removal except for an unidentified liana that was not found in 1986 but was moderately abundant in 1989. Regeneration of commercial tree species (tolerant and intolerant), noncommercial tree species, and nontree species was compared with the residual basal area and percentage of basal area removed. Frequency of intolerant commercial species increased as residual basal area decreased. Frequency of tolerant commercial species was not affected by residual basal area or percentage of basal area reduced.

Enrichment planting, a tool for regenerating tropical forests, has been used but not evaluated for many years in community forests in Quintana Roo, Mexico. This study was designed to determine if enrichment planting would assure regeneration of big-leaf mahogany and Spanish cedar in these forests. Survival and growth of seedlings of both species planted in two communities were evaluated. Seedlings had been planted from 1986 to 1993 along main and log-hauling roads, in log landings, and in narrow strips opened under forest canopies. Survival was 18%; it varied considerably from year to year but was similar for both species and among the four types of areas planted. Available light appeared to be the principal limiting factor for survival in the enrichment plantings.