Flora del bosque mesófilo de montaña y vegetación adyacente en Avándaro, Valle de Bravo, estado de México, México

El bosque mesófilo de montaña estudiado se encuentra en la zona central de la frontera entre la Faja Volcánica Transmexicana y la cuenca del río Balsas. En este trabajo se incluye una lista florística que comprende 98 familias, 245 géneros y 391 especies de plantas vasculares. La vegetación arbórea presenta tres estratos, uno alto (cercano a 40 m), donde son frecuentes varias especies de encinos y Zinowiewia integerrima; uno medio (20 m) con Carpinus caroliniana, Ternstroemia lineata subsp. lineata y Tilia americana, entre otras y uno bajo (5-15 m) con Clethra spp., Cleyera integrifolia, Cornus disciflora, Garrya laurifolia, Meliosma dentata, Oreopanax xalapensis, Parathesis melanosticta, Styrax argenteus y Symplocos citrea. Los estratos arbustivo y herbáceo son ricos debido a la intrusión de especies de zonas de uso agropecuario y recreativo. Se discute el estado de conservación del bosque con base en indicadores ambientales derivados de los resultados florísticos.

Una población relicta de Acer saccharum subsp. skutchii (Aceroideae) en el estado de Guerrero, México

Se describe la estructura, composición, diversidad, relaciones ambientales y conservación de un bosque mesófilo con Acer saccharum subsp. skutchii (arce azucarero) recientemente encontrado en el municipio de Coahuayutla de José María Izazaga, Guerrero. Se registraron los individuos leñosos con ≥1 cm dap en parcelas circulares de 10 m de radio, y la altura de plántulas y plantas juveniles del arce azucarero en parcelas de 5.6 m de radio. Para cada especie se obtuvo su valor de importancia. Se utilizó la técnica de ordenación Escalar Multidimensional No-métrica (NMDS) para explorar sus correlaciones con variables edafológicas, coordenadas geográficas, de elevación y apertura de claros. Se registraron 43 especies de plantas leñosas en una superficie de 0.126 ha. Las familias mejor representadas fueron Asteraceae y Fagaceae. La distribución diamétrica de las plantas leñosas mostró una forma de “J” invertida, indicando regeneración exitosa. El arce azucarero fue codominante en el dosel con Carpinus caroliniana y Quercus uxoris. Tanto en la población de Guerrero, como en las otras cinco localidades donde habita el árbol en México y Guatemala, la mayoría de las correlaciones encontradas entre la presencia y ausencia de árboles, incluyendo Acer saccharum subsp. skutchii, y los factores ambientales se refirieron a las características de suelo. De las especies registradas en el estudio, 30% están incluidas en alguna categoría de riesgo. El régimen de incendios en la zona pone en peligro la persistencia de este árbol en el sitio de estudio.

Effects of Extended Photoperiod and Light Quality on Growth of Carpinus caroliniana, Fagus grandifolia and Gymnocladus dioicus Seedlings

Although Carpinus caroliniana (American hornbeam), Fagus grandifolia (American beech), and Gymnocladus dioicus (Kentucky coffeetree) have considerable landscape merit, they are not readily available in nurseries. Little research has been conducted on the cultural preferences of these species during nursery production. This study tested the effects of light quality and extended photoperiod on these species. Container-grown seedlings were subjected to three light treatments: 18-hour photoperiod using high pressure sodium lights (HPS), 18-hour photoperiod using incandescent lights (INC), and natural light and daylength (NAT). After 14 weeks, stem height of F. grandifolia seedlings was greatest for HPS light and least for NAT light. After 8 and 12 weeks, light source had no impact on stem heights of C. caroliniana. In 1997, stem height and caliper of G. dioicus were greatest using HPS light. In a repeat of the G. dioicus, experiment in 1998, HPS and INC light treatments resulted in greater stem height, caliper, and shoot and root dry weight compared to NAT treatment. The increase in height of seedlings under the HPS and INC treatments compared to the NAT treatments resulted from a greater number of seedlings that produced a second flush of growth under the HPS and INC treatments.

Microfungi from Carpinus caroliniana

The microfungal flora and community structure of the bark of Carpinus caroliniana is described as perceived by a direct isolation method. Twenty-four bark discs were removed from 10 trees at five different sites in New Jersey and West Virginia and applied to three different isolation media. From 1200 bark discs from 50 trees, 155 species of fungi were isolated. The overall recovery rate was 11.5 species/tree. A medium with cycloheximide gave the highest species recovery rates and isolated the highest percentage of all the species recovered. A medium of malt–yeast extract gave the most isolates but lowest species recovery rate. Eleven of the 12 dominant species were preferentially isolated on one of the three isolation media. The community structure of the fungi recovered from Carpinus bark exhibited the typical dominance–diversity curve that has been reported for other saprobic fungal communities. Generally, the floristic composition was similar to the bark of other tree species previously studied in temperate deciduous forests. The total number of isolates was dominated by a few species of ubiquitous epiphytic taxa, but a large percentage of the species recovered appeared either at a single site or on a single tree. Sterile isolates accounted for 39% of the species and Coelomycetes for 13% of the species. The sites from West Virginia had a significantly higher recovery rate of species per tree than the New Jersey sites. In a search for fungi for potential biotechnological applications, bark is an easily utilized and rich resource. Simple isolation methods yield several ecological groups of fungi, including terrestrial epiphytes, soil decomposers, endophytes, entomopathogenic fungi, Ingoldian Hyphomycetes, and decomposer Basidomycetes. Key words: bark, ironwood, isolation methods, microbial diversity.

Streamline Basal Application of Herbicide for Small-Stem Hardwood Control

The effectiveness of low-volume basal application of herbicide—"streamline" application—was evaluated on 25 hardwood species and loblolly pine. Test mixtures were step-wise rates of Garlon 4 mixed in diesel fuel with a penetrant added. Most comparisons tested 10%, 20%, and 30% mixtures of Garlon 4, while tests with saplings and small trees used 20%, 30%, and 40%. Target stems ranged from 2 ft tall to 6 in. dbh. Applications were made in February, using pressure-regulated handguns equipped with straight stream nozzles attached to backpack sprayers. Two bands of the herbicide mixture were applied to two sides of all stems. After 18 months, susceptible hardwood species with greater than 80% average control at all three Garlon rates were water oak (Quercus nigra), am. hornbeam (Carpinus caroliniana), black locust (Robinia pseudoacacia), boxelder (Acer negundo), huckleberry (Vaccinium elliottii), sumacs (Rhus spp.), southern bayberry (Myrica cerifera), and mountain-laurel (Kalmia latifolia). Tolerant species with less than 40% control were sourwood (Oxydendrum arboreum), titi (Cliftonia monophylia), and yellow poplar (Liriodendron tulipifera) (>1 in. groundline diameter). Treatment of loblolly pines resulted in an average of 22% mortality. Smaller stems were more readily killed than larger stems for all species. South. J. Appl. For. 14(4):161-165.