Basave Villalobos E.,Postgrado Forestal |
Cetina Alcala V.M.,Postgrado Forestal |
Lopez Lopez M.A.,Postgrado Forestal |
Aldrete A.,Postgrado Forestal |
Del Valle Paniagua D.H.,Colegio de Mexico
IForest | Year: 2015
Swietenia humilis is a valued tree species for its high-quality wood, among other commercial interests. Attempts to plant the species in southwest Mexico have often failed due to poor quality seedlings combined with low soil fertility and dry environments. Nursery top-pruning and fertilization are practices previously reported to improve seedling quality, and facilitate rapid establishment under poor site conditions. In the present study, the effects of three top-pruning intensities (0%, 25%, and 50%), and two fertilizer regimes (traditional and exponential) on several S. humilis seedling morphological and physiological indices were tested in the nursery, and a quality test trial on nutrient-poor soils was conducted. Significant interactions between the above two treatments were not detected. Top pruning at 25% and 50% intensity did not improve S. humilis seedling quality. However, exponential nutrient supply exhibited favorable effects on seedling growth. Results of the quality test trial revealed exponential fertilization promoted satisfactory seedling performance when low nutrient availability was a limiting factor. © SISEF.
Self-thinning and density management diagrams for Pinus patula fitted under the stochastic frontier regression approach [Auto-aclareo y guías de densidad para Pinus patula mediante el enfoque de regresión de frontera estocástica]
Santiago-Garcia W.,Postgrado Forestal |
De los Santos-Posadas H.M.,Postgrado Forestal |
Angeles-Perez G.,Postgrado Forestal |
Valdez-Lazalde J.R.,Postgrado Forestal |
And 2 more authors.
Agrociencia | Year: 2013
Forest management in the region of Zacualtipán, Hidalgo, Mexico, has focused in the last three decades on the cultivation of pure even-aged stands of Pinus patula, the native timber species of fastest growth and high commercial value. The rapid growth of P. patula requires appropriate management of stand density to properly schedule thinnings and optimize stands' rotation. In this study, we determined the maximum line size-density relationship or self-thinning considering the stochastic frontier regression and ordinary least squares approaches for Reineke and Yoda models. In the estimation, we used data derived from 42 permanent sampling plots of 400 m2. The best estimates of the self-thinning line were obtained using the stochastic frontier models Truncated-normal and Half-normal of Reineke and Yoda. On this basis, we set diagrams for tree density management, considering the relative stand density index of Reineke (SDI) and that of Yoda (YDI). The method of stochastic frontier regression enables to directly estimate the upper limit of self-thinning without resorting to the selective use of data, where the points in which mortality from self-thinning has not yet exhibited are excluded from the analysis. For SDI and YDI, stochastic setting suggests a more conservative mortality rate compared to least squares fit. The method also allows a more efficient use of data, and incorporates information from inventory plots without remeasurements.