Impactos ambientales del aprovechamiento forestal en Venezuela

Interciencia (Impact Factor: 0.25). 03/1998; 23(2):74-83.

ABSTRACT La legislación vigente en Venezuela indica que los Planes de Ordenación y Manejo Forestal (POM) ya incluyen en su metodología la Evaluación de Impacto Ambiental (EIA); sin embargo al aplicar una técnica específica de EIA se observan las siguientes deficiencias:
• Impactos no previstos como los cambios en el microclima por el efecto de claro, las pérdidas de macro y micronutrientes, la alteración de las micorrizas, el cambio de uso de los suelos, la afectación de animales polinizadores y vectores de semillas, los daños a las vías interurbanas, la afectación de zonas indígenas, los accidentes personales y la posible contaminación del agua por el mantenimiento de maquinaria y uso de campamentos.
• Impactos mal evaluados o con medidas de control mal diseñadas como la alteración de la composición florística, la erosión genética y degradación del valor económico del bosque, la muerte y desplazamiento de fauna, el deficiente nivel de vida de los trabajadores y las pérdidas de biodiversidad.
Se discute la influencia de algunos de estos impactos para alcanzar las metas del manejo forestal (rendimiento continuo) y se evidencia la necesidad de monitorear algunos indicadores que demuestren el logro del manejo sostenible.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The patterns and processes of canopy tree death and replacement were studied in the elfin forest of Monteverde, Costa Rica. Natural treefalls and limbfalls in a 5.2-ha study area opened 0.8, 1.4, and 1.0% of the area in three consecutive years with about four gaps/ha/yr larger than 4 m2. Forty-one percent of the gaps were formed by uprooted trees, 39% by snapped trees, and the remainder by limbfall, the collapse of epiphyte masses, and dead standing trees killed by lightning. Gaps were found to be spatially aggregated, with more gaps occurring within 17-20 m of one another than expected by chance. Variation among gaps was complex; the first principal component of the variation in eight important gap characteristics among 88 gaps contrasted measures of gap size with the way the gapmaker broke and the position of the gap on the slope, but accounted for only 56% of the total variation. In gaps < 8 mo old, the leaf area index was 1.6, and only 8% of the area was not covered by living plants. Leaf area index increased logarithmically with time since gap formation and with gap area; 50% of the mature-forest leaf area index of 5.1 was recovered in 3 yr in gaps of 10 m2 and in 1.5 yr in gaps of 40 m2. Saplings of both shade-tolerant and shade-intolerant canopy tree species were more abundant in gaps than in the understory of mature forest. Sapling density increased with time since gap formation, but, given the effect of time, shade-tolerant sapling density decreased with gap area, while shade-intolerant sapling density increased. Saplings of eight species were concentrated on nurse logs, while those of one other species were concentrated on the mineral soil disturbed by uprooting trees. Experimental investigation of colonization of exposed soil in treefall gaps indicated that buried seeds give rise to many more tree seedlings than seeds dispersed into recent gaps. Many of the saplings in gaps, however, started life as epiphytic seedlings in the crowns of the trees that fell. The dynamics of this lower montane rain forest resemble many lowland forests in regards to the importance of gap-phase regeneration but differ in the sources of canopy gap colonists and in the importance of different substrates for seedling establishment.
    Ecology 06/1988; 69(3):764-777. · 5.00 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A forest harvesting system using skyline cables was evaluated for its effect on secondary forest structure and tree species richness of lowland rain forests in the Bajo Calima Concession, western Colombia. Forests were sampled using six 0.1 ha plots in mature primary forest and sites 0.4, 4, 8 and 12 years since logging. Clear-cutting reduced overstory (trees greater than or equal to 10 cm dbh) basal area, biomass and richness to 7%, 4%, and 17%, respectively, of primary forest levels. By the twelfth year 46% of basal area, 37% of biomass, and 38% of richness had returned. However, 63% of biomass and 50% of richness were composed of ‘core pioneer’ species. The replacement of primary (climax) species dominants by pioneer species indicates that the early process of regeneration is more appropriately described as secondary succession. Age since clear-cutting during the first 12 years of growth was a significant linear predictor of both pioneer and climax species biomass and basal area, but not climax richness. Extrapolation of these trends beyond 12 years suggest that overstory basal area and biomass would equal that of mature rain forests by 30 years (the proposed rotation time). However, the decline in pioneer growth rates over time, the slow climax growth rates, and the failure to predict observations in an 18-year old stand indicate that such a model is unrealistic. Climax species need longer than 30 years to recover, and biomass may decline between 15 and 30 years if many short-lived pioneer trees die before climax trees are well established. More consideration needs to be given to understanding the regeneration of climax species if conservation and harvesting are to be combined. Putting part of the concession under a longer rotation time may permit climax trees to regenerate successfully.
    Forest Ecology and Management. 01/1992;
  • [Show abstract] [Hide abstract]
    ABSTRACT: Selective harvesting in tropical forests has been shown to cause considerable damage to residual trees in stands that have relatively high densities of commercial trees. To complement existing studies, we measured forest damage caused by the selective harvesting of mahogany (Swietenia macrophylla), a very low density species in the Bosque Chimanes, Bolivia. Secondary damage along main roads and skid trails accounted for most of the damage measured in the study site. Total damage was low (4.39% of the study area), but results from our simulation model suggested that damage could be decreased by up to 25% by requiring main roads and skid trails to be linear.We used our simulation model to investigate the relationship between harvest intensity and forest damage. At low harvest intensities, most forest damage occurs from the construction of main roads. As harvest intensity increases, secondary damage from skid trails and tree felling comes to dominate forest damage. Overall, less damage will result to the forest for a given harvest volume if the harvest area is reduced and harvest intensity increased. Additional benefits to increasing harvest intensity are that re-entry into the logged site can be delayed, allowing the forest more time to recover, and regeneration of light-demanding species such as mahogany can be enhanced. The main impediment to increasing the harvest intensity in selective harvesting operations in Latin America is the lack of international markets for lesser known species, although there is some local and national demand.
    Forest Ecology and Management. 01/1993;


Available from
Jun 1, 2014