Colombia Forestal

7

Authors: Juan Carlos Camargo García, Juan David Suarez Franco

The preservation of guadua (Guadua angustifolia) culms is an important process which affects their quality after harvesting and their subsequent utilization as a raw material in handicraft, furniture and construction. Boron and boric acid are frequently used in the preserving solution (PS). To ease the adsorption the culm diaphragm is usually drilled before immersion in the PS. We performed a factorial experiment to determine the possible effects of drilling the culm diaphragm on compression and shear strength. Two measures of culm maturity were considered. The traditional measure is defined by the external features of the culms and another is based on the time since culm emergence. Variance analyses did not show any significant (p > 0.05) difference in mechanical properties when the diaphragm was drilled. Nevertheless, those culms with maturity defined using the traditional approach had significantly lower values of compression and shear strength. In addition, culms with higher moisture content were significantly stronger.

14

Authors: César Augusto Polanco Tapia, Jenny Paola Caicedo Velásquez, Diego Hernán Beltrán Hernández

The wood anatomy of Caryodaphnopsis cogolloi Van der Werff was studied using xilological characteristics identified in transverse and longitudinal wood cuts (tangential and radial views). Wood natural durability was established in an accelerated laboratory trial, using two methods: a soil block method established by the Colombian Technical Standard NTC 1127 (NTC for its acronym in Spanish), and an Agar block method ruled by the standard norm EN 350-1: 1994 in which the decay fungi used were Trametes versicolor and Gloeophyllum trabeum. The durability was assessed by weight loss and analysis of the fungal decay characteristics over a four month incubation period on the wood samples where each month the colonization mechanism, development and fungal growth characteristics were observed, along with the effects on the cell wall. Caryodaphnopsis cogolloi wood is significantly resistant to fungal white and brown rotting showing a mean weight loss of 5.1% and 6.1% respectively in the soil block method, while in the agar block method the weight loss was 5.9 % for both fungi. Decay patterns in the samples demonstrated that T. versicolor eroded cell walls and produced enlargement in the cell wall holes in some cells, while G. trabeum produced a reduction in cell wall thickness in a few cells.

16

Authors: Andrés Avella Muñoz, J. Orlando Rangel Churio

Characterizations of oak forests according to their floristic composition and structure and the identification of the main use requirements of local communities were performed. This permitted recommendations for the sustainable use and preservation of these forest types in the Guantiva-La Rusia-Iguaque conservation corridor (Santander-Boyacá, Colombia). The oak forests correspond to the Quercus humboldtii - Billia rosea major forest formation, which can be categorized into a hierarchical structure of seven forest types. The Q. humboldtii - Ocotea calophylla forests present in the high Andean fringe (>2200-3200 m.a.s.l); the Q. humboldtii - Alchornea grandiflora forests, common in the Andean region include two types of forests, Q. humboldtii - Blakea cuatrecasii, and Q. humboldtii - Cyathea multiflora forests; furthermore, these types of forests comprise the Q. humboldtii - Daphnopsis caracasana and Q. humboldtii - Pouteria baehniana forests. The final forest type is the Virola macrocarpa - Q. humboldtii forests present in the sub-Andean life zone. According to interviews with members of local communities oak forests are considered the main components of ecosystems of high cultural and social value. The interviews identified two principle uses of oaks, for fuel and for land tenure and property maintenance (fence posts, stakes for crops, timber and tool handles). According to ecological characterization and conservation status assessments the Virola macrocarpa - Q. humboldtii, Q. humboldtii - Pouteria baehniana and Q. humboldtii - Daphnopsis caracasana forests can be used by the community with technical prescriptions. The Q. humboldtii - Blakea cuatrecasii and Q. humboldtii - Ocotea calophylla forests should not be used under any circumstance and should be subject to strict strategies for their protection and ecological restoration. The future of oak forests is uncertain unless appropriate strategies based on the generation of co-management agreements with local communities for sustainable use and conservation are proposed and implemented.

19

Authors: Cristopher Edgar Camargo Roa, Jesús Enrique Andrades Grassi, Raúl Oswaldo Vidal García

Digital elevation models -DEM- as a visual representation of landforms and altitude have been very useful in the study of topography. This research took place in a 3.39 km2 area of the La Machirí torrential micro-watershed (Táchira State, Venezuela). Its purpose was to evaluate a DEM generated through a process of digital photogrammetry that was also checked against a DEM edited from existing level curves in topographic charts. Exploratory Spatial Data Analysis (ESDA) and the Multiple-Point Geostatistics (Minimal Distance Analysis, Special Pattern Analysis, Variogram, and Variographic Analysis of Surfaces) methods were used. Differences between the two models were identified generated by the sum of the errors caused by the spatial distribution of checkpoints marked for the photogrammetric process (less than the number of checkpoints of a normal distribution, possible spatial bias between checkpoints and indications of spatial dependence phenomena), the error generated from the interpolation method applied during the process, and by the error caused by local erosion processes. The first assessment indicated a difference in the surface area of 0.57 ha and of 9.41 hm3 in volume in both DEMs. A zoned analysis indicated that at least three more checkpoints are necessary in order to get a more accurate DEM.