Reconstrucción de la precipitación y caudal medio del río Piaxtla mediante anillos de crecimiento de Pseudotsuga menziesii (Mirb.) Franco

La reconstrucción de variables hidroclimáticas es importante para comprender el funcionamiento de las cuencas forestales y tomar decisiones sobre su manejo. En este trabajo se reconstruyó la precipitación y el caudal medio a partir de información de anillos de crecimiento de Pseudostuga menziesii en la cuenca del río Piaxtla. Con la información de siete series dendrocronologías, se construyó una sola cronología regional. Se probó la correlación de la cronología regional con eventos de fenómenos océano-atmósfera como El Niño Oscilación del Sur, Oscilación Decadal del Pacífico, Oscilación Multidecadal del Atlántico e Índices de la Severidad de Sequía de Palmer. Los resultados mostraron que fue posible la reconstrucción de la precipitación de noviembre-abril y el caudal medio noviembre-agosto a partir de la serie de madera temprana con ecuaciones verificadas y validadas: Precipitación = -271.538 + 447.764*(índice de madera temprana), (r = 0.85, n = 49, p < 0.0001) y caudal medio = 5.123 + 0.623*log10(índice de madera temprana), (r = 0.68, n = 46, p < 0.001). Excepto por la Oscilación Multidecadal del Atlántico, todos los fenómenos globales mostraron correlación significativa con la información de los anillos de crecimiento. Este estudio confirma que los bosques de P. menziesii de la Sierra Madre Occidental son altamente sensibles al clima, lo que se refleja en la anchura de anillos de crecimiento y a su vez en la variabilidad del caudal medio de la cuenca. Por lo anterior se debe aprovechar el potencial de este tipo de trabajos para prever los cambios en la disponibilidad de recursos hídricos, así como ampliar su uso en la valoración de servicios ambientales hidrológicos.

Effect of precommercial thinning followed by a fertilization regime on branch diameter in coastal United States Douglas-fir plantations

The effect of precommercial thinning in 6- to 13-year-old Douglas-fir ( Pseudostuga menziesii (Mirb.) Franco var. menziesii ) plantations with and without fertilization with 224 kg·ha–1 nitrogen (N) as urea on the mean diameter of the largest limb at breast height (DLLBH) was modeled. DLLBH is a simple, nondestructive field measurement related to log knot indices used to measure log quality in product recovery studies. Model [1] succeeded in predicting mean DLLBH (RMSE = 2.80 and radj2 = 0.84) using only site, initial stocking, and treatment variables. Model [2], which used only mean tree variables, improved on model [1] and was simpler. However, model [3], which used a combination of both groups of variables, produced the best model. Model [4] successfully predicted mean DLLBH using variables that can be measured with light detection and ranging (LIDAR), a high-resolution remote sensing technology. Since the age when the live crown receded above breast height is an important variable in some of the models, model [5] was developed to predict when crown recession above breast height occurs. This study found that mean DLLBH of Douglas-fir plantations can be estimated using variables obtained from stand-level growth models or remote sensing, providing a quality indicator that can be easily measured and verified in the field.

The potential for woody understory plants to provide refuge for ectomycorrhizal inoculum at an interior Douglas-fir forest after clear-cut logging

Clear-cut logging can decrease the amount of inoculum for some ectomycorrhizal fungi. Ectomycorrhizal plants that are not selected for harvest (refuge plants) may, therefore, be important for the maintenance of ectomycorrhizal fungal inoculum in clearcuts following logging. The purpose of this study was to identify refuge plants that could provide ectomycorrhizal fungal inoculum for outplanted seedlings. The ectomycorrhizal status of selected plants was assessed in 1.6-ha clearcuts and in adjacent forest. Over 3 years, 17 and 14 morphotypes were described for Pseudostuga menziesii (Mirb.) Franco (Douglas-fir) and Arctostaphylos uva-ursi (L.) Spreng, respectively. Ten morphotypes (six of these confirmed with restriction fragment length polymorphism patterns) were shared by both species. Anatomical and molecular analyses revealed that, for the morphotypes observed, ectomycorrhizal fungi formed ectomycorrhizal anatomy when associated with Douglas-fir and arbutoid anatomy with A. uva-ursi. Because advanced regeneration seedlings of Douglas-fir and A. uva-ursi are well distributed throughout this site, these two species have a high potential to provide ectomycorrhizal fungal inoculum for outplanted seedlings. There was no difference in mycorrhizal richness between A. uva-ursi plants sampled from the clearcut and forest in the latter 2 years of the study. Conversely, the richness of ectomycorrhizae associated with Douglas-fir sampled from the forest was significantly greater than for seedlings sampled from the clearcuts.

Discrete proteins associated with overwintering of interior spruce and Douglas-fir seedlings

Seasonal protein changes were followed in seedlings of interior spruce (a mixture of Picea glauca and P. englemannii) and Douglas-fir (Pseudostuga menziesii) by sodium dodecylsulfate – polyacrylimide gel electrophoresis. A 30-kDa protein in seedlings of Douglas-fir and a 30- and 27-kDa protein in interior spruce that were not detected in the late summer accumulated in seedling tissues during the fall. These proteins remained present throughout the winter but declined rapidly in seedlings during the initial flush of spring growth. There was an increase in the total protein content of interior spruce seedling tissues during the fall; however, the accumulation of the 30- and 27-kDa protein was tissue specific, since it increased in the apical bud, shoot, and root tissue but not in the leaves. By late fall these proteins represented approximately 15% of the total seedling protein. Measurements of variable chlorophyll fluorescence indicated that the accumulation of these overwintering proteins was associated with the seasonal decline in photosynthetic capacity. These results suggest that conifer seedlings may utilize these proteins as a storage reserve during overwintering. Key words: conifers, electrophoresis, overwintering, proteins, seasonal, seedlings.