Resumen: Se analizó la variación estructural de comunidades de árboles y arbustos presentes en diferentes tipos de vegetación (matorral subtropical, bosque de encino, bosque mixto, bosque de pino y bosque de oyamel) a través de gradientes de altitud y profundidad del suelo en la Cuenca de Cuitzeo, Michoacán. La cuenca cubre 4,000 km 2 y un ámbito altitudinal de 1,700 a 3,420 m s.n.m. En toda la cuenca se muestrearon 50 sitios de 1,000 m 2 cada uno, se registró un total de 4,941 plantas con diámetro a la altura del pecho ≥ 1 cm, que representaron 164 especies, 88 géneros y 47 familias. Las familias con más especies fueron Asteraceae (30; 18.4% del total de especies) y Fagaceae (16; 9.8%). Por arriba de los 2,500 m s.n.m. se encontraron los bosques de pino, oyamel y mixto (pino-encino); por debajo de 2,300 m s.n.m. se encontraron el bosque de encino y el matorral subtropical. La densidad de plantas fue semejante entre los tipos de vegetación, pero diferentes indicadores de la biomasa aumentaron con la altitud y la profundidad del suelo. El matorral subtropical y el bosque mixto fueron los más diversos en especies, mientras que el bosque de coníferas fue el menos diverso. Existió un elevado recambio de especies dentro y entre los tipos de vegetación (índice de similitud de Bray-Curtis, ámbito: 5.4-25.4%). La composición de especies varió notablemente asociada con la altitud y la profundidad del suelo. Se ofrecen lineamientos para la conservación del importante complejo vegetal presente en la Cuenca de Cuitzeo. Palabras claves: cuenca hidrográfi ca, diversidad alfa y beta, gradientes ambientales, relación altitud-vegetación, relación suelovegetación.Abstract: This work analyzed the structural variation of tree and shrub communities present in different vegetation types (subtropical scrub, oak forest, mixed forest, pine and fi r forest) across altitudinal gradients and soil depth at the Cuitzeo Basin, Michoacán. The basin covers 4,000 km 2 and altitudinal range of 1,700 to 3,420 m a.s.l. In the entire basin we sampled 50 sites 1,000 m 2 each, recording a total of 4,941 plants with a diameter at breast height ≥ 1 cm, representing 164 species, 88 genera and 47 families. Families with more species were Asteraceae (30, 18.4% of total species) and Fagaceae (16, 9.8%). Above 2,500 m a.s.l. were found pine, fi r and mixed (pine-oak) forests; below 2,300 m a.s.l. were found the oak forest and subtropical scrub. Plant density was similar among vegetation types but different indicators of community biomass increased with altitude and soil depth. The subtropical scrub and mixed forest were the most diverse in species and coniferous forest the less diverse. There was a high turnover of species within and among vegetation types (index of Bray-Curtis similarity, range: 5.4-25.4%). The vegetation composition varied signifi cantly associated with altitude and soil depth. We offer some guidelines for the conservation of the important vegetation complex present in the Cuitzeo Basin.

Palm leaves represent one of the most important non-timber forest products in tropical and subtropical regions. Brahea aculeata is an endemic palm of northwest Mexico, whose leaves are intensively exploited for roof thatch and handcrafts. As part of a long-term defoliation experiment, we evaluated the effects of different leaf harvest on foliar and reproductive traits of adults and attributes of their progeny. We conducted a six-year manipulative experiment and applied three harvesting treatments to adults: high harvest, low harvest and no harvest (control). We recorded leaf production and size, flower and fruit production, seed germination and seedling growth. We also explored trade-offs among foliar and reproductive traits.Harvested palms exhibited drastically reduced reproductive activity, producing fewer flowers and fruits (up to 80 and 90% fewer than unharvested palms). However, individuals in both harvest treatments had larger leaves and increased leaf production rates, compared to control palms. For harvested palms, we registered first a slight increase in leaf traits and a decline in reproductive attributes. These traits showed a gradual reduction and for six period attained very low proportional values compared to control palms (~0.10), however individuals in the harvested treatments maintained the greatest leaf lengths and leaf production rates. Seed germination and seedling growth rates of progeny from harvested palms were significantly lower than control palms, with seeds from the high harvest treatment having the lowest seed production and germination rates. Relationships among leaf (size/production) and reproductive traits (flower/fruit production) were positive during the fourth year, but showed negative relationships for the fifth year suggesting a trade-off between reproduction and growth functions. Leaf harvesting in B. aculeata seems to alter patterns of resource allocation away from reproduction as reflected in a decrease in the probability of reproduction, seed number, germination, and vigor, causing a strong decrease in the reproductive success of this species. Results showed that the consequences of long-term leaf harvest not only affect harvested individuals, but also the fitness and vigor of progeny. This type of long-term studies is essential to understand the population dynamics of non-timber forest products and helps inform sustainable harvesting programs considering intensity, frequencies and periods for recovery from defoliation. Also results may help to explain how intensive and non-planned management schemes may negatively affect vital rates and long-term dynamics of populations from non-timber forest products and other components of the ecosystem.

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