Browsing by Autor "Geoffrey M. Blate"

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Beyond reduced-impact logging: Silvicultural treatments to increase growth rates of tropical trees
(Elsevier BV, 2008) Marielos Peña‐Claros; Todd S. Fredericksen; Alejandro Alarcón; Geoffrey M. Blate; U. Choque; Claudio Leaño; Juan Carlos Licona; Bonifacio Mostacedo; William Pariona; Z. Villegas
Estructura de la vegetación y de la comunidad de aves en un bosque intervenido de La Chonta, Guarayos, Santa Cruz
(2005) Betty Flores; Damián I. Rumiz; Geoffrey M. Blate
El estudio fue realizado en la concesion forestal La Chonta, (Prov. Guarayos, Santa Cruz, Bolivia), con la finalidad de evaluar la estructura de la vegetacion y la comunidad de aves en sitios que en anos recientes habian sufrido aprovechamiento selectivo de madera, incendios forestales, o ninguno de estos disturbios. Registramos la abundancia y riqueza de aves por conteo visual y auditivo y la cobertura de las formas de vida de plantas en 30 puntos fijos en tres tratamientos: bosque aprovechado (n = 15), quemado (n = 7) e inalterado (n = 8). El area basal y la cobertura de la vegetacion fue mayor en el bosque inalterado. La cobertura de hierba fue mayor en el estrato medio del bosque quemado. En cambio, la cobertura de helechos fue mayor en el sotobosque del inalterado. La abundancia y riqueza especifica total de aves no mostraron diferencias significativas entre los tratamientos. La cobertura de arboles altos y de lianas en las copas mostro una asociacion positiva con la riqueza de especies de aves en el dosel, mientras que otras relaciones entre la vegetacion y las aves no fueron claras. Palabras claves: Abundancia de aves, bosque subhumedo tropical, cobertura de vegetacion, conteo por puntos, dosel, estrato medio, estratificacion vertical, sotobosque. ABSTRACT Vegetation and the bird community structure in areas that had suffered selective logging, forest fires, or none of these disturbances in recent years were studied in La Chonta forest concession (Guarayos Province, Santa Cruz, Bolivia). Bird density and richness were determined visually and acoustically and vegetative cover, according to plant life form and vertical strata, was evaluated in 15 logged, 7 burned but not logged, and 8 undisturbed fixed sites. Basal area and vegetation coverage were greater in undisturbed forest. The herbaceous cover was greater in the middle strata of the burned forest but fern cover was higher in the understory of undisturbed sites. Tall trees and canopy vines were positively associated to bird species richness. Other associations between vegetation and bird community structure were inconclusive. Overall bird abundance and richness did not differ significantly across treatments. Key words: Bird abundance, canopy, point counts, vegetation cover, vertical stratification, medium strata, subhumid tropical forest, understory, Bolivia
MODEST TRADE-OFFS BETWEEN TIMBER MANAGEMENT AND FIRE SUSCEPTIBILITY OF A BOLIVIAN SEMI-DECIDUOUS FOREST
(Wiley, 2005) Geoffrey M. Blate
Fire threatens to undermine the conservation potential of tropical production forests. Expecting seasonally deciduous forests that require intensive silviculture to secure sustained yields of commercial species to be especially fire prone, I assessed fire susceptibility in a Bolivian semi-deciduous forest subjected to four management intensities: no logging control; selective harvest only; and two harvest treatments with additional silviculture. I quantified treatment effects on fuel loads, vegetative cover, dry-down rates of 10-h fuels, and fire spread in 4-m2 test plots. With these data and daily rainfall records, I estimated the number of fire-prone days per month associated with each treatment. Fuel loads increased with management intensity, but principally in the 1000-h size class. Treatment impacts on vegetative cover were modest, in part because only 30% of the control forest comprised mature stands with closed canopies >16 m high. Fuels dried enough to ignite in 3–5 days in sites with sparse cover, but within 11 days in sites with dense cover. Given that rainless periods of 20 days are common throughout the dry season, fuels are dry enough to burn for long periods in this forest. In the late dry season in forest logged 2–4 months previously, total cover had little effect on whether test plots burned. Plots in recently logged forest burned more readily than those in forest logged one and three years previously. The model developed for calculating fire-prone days indicated that, unlike intact evergreen Amazon forests that typically remain fire resistant, this forest is very fire prone during most dry seasons. The similar number of fire-prone days among treatments suggests that forest managers need not worry about elevating fire susceptibility with their silviculture. These results suggest that timber management and fire susceptibility trade-offs are modest in this forest because it is already fire prone and because the intensity of silvicultural treatments applied was low compared to other tropical production forests. Fire severity, however, would likely increase with management intensity due to increases in 1000-h fuels. Fire prevention efforts must complement silviculture treatments to achieve sustained yields if these and similar forests are to serve both production and conservation goals.
Regeneration of commercial tree species following silvicultural treatments in a moist tropical forest
(Elsevier BV, 2007) Marielos Peña‐Claros; Edward M. Peters; M. Joaquin Justiniano; Frans Bongers; Geoffrey M. Blate; Todd S. Fredericksen; Francis E. Putz
Soil Effects on Forest Structure and Diversity in a Moist and a Dry Tropical Forest
(Wiley, 2011) Marielos Peña‐Claros; Lourens Poorter; Alfredo Alarcón; Geoffrey M. Blate; U. Choque; Todd S. Fredericksen; M. Joaquin Justiniano; Claudio Leaño; Juan Carlos Licona; William Pariona
ABSTRACT Soil characteristics are important drivers of variation in wet tropical forest structure and diversity, but few studies have evaluated these relationships in drier forest types. Using tree and soil data from 48 and 32 1 ha plots, respectively, in a Bolivian moist and dry forest, we asked how soil conditions affect forest structure and diversity within each of the two forest types. After correcting for spatial effects, soil‐vegetation relationships differed between the dry and the moist forest, being strongest in the dry forest. Furthermore, we hypothesized that soil nutrients would play a more important role in the moist forest than in the dry forest because vegetation in the moist forest is less constrained by water availability and thus can show its full potential response to soil fertility. However, contrary to our expectations, we found that soil fertility explained a larger number of forest variables in the dry forest (50 percent) than in the moist forest (17 percent). Shannon diversity declined with soil fertility at both sites, probably because the most dominant, shade‐tolerant species strongly increased in abundance as soil fertility increased.
Timber production in selectively logged tropical forests in South America
(Wiley, 2007) Michael Keller; Gregory P. Asner; Geoffrey M. Blate; John McGlocklin; Frank Merry; Marielos Peña‐Claros; J. Zweede
Selective logging is an extensive land-use practice in South America. Governments in the region have enacted policies to promote the establishment and maintenance of economically productive and sustainable forest industries. However, both biological and policy constraints threaten to limit the viability of the industry over the long term. Biological constraints, such as slow tree growth rates, can be overcome somewhat by management practices. In order to improve the likelihood of success for sustainable management, it is important to accept that forests change over time and that managed forests may be different than those of the present. Furthermore, education campaigns must convince decision makers and the public of the value of forest resources. We recommend that the forest sector be governed by simple, understandable regulations, based on sound science and consistent enforcement, and that governments work with, instead of against, industry. Problems of tropical forest management are far from being solved, so biological and social scientists should continue to generate new knowledge to promote effective management. El aprovechamiento selectivo es una práctica extensiva del uso del suelo en Sudamérica. Los gobiernos de la región han establecido políticas para promover el establecimiento y mantenimiento de industrias forestales económicamente productivas y sostenibles. Sin embargo, tanto restricciones biológicas como políticas amenazan con limitar la viabilidad a largo plazo de esta industria. Las limitaciones biológicas, tales como una baja tasa de crecimiento de los árboles, pueden ser superadas parcialmente a través de prácticas de manejo. Para aumentar la probabilidad de éxito del manejo sostenible es importante reconocer que los bosques cambian en el tiempo y que los bosques manejados podrían ser diferentes a los bosques actuales. Asimismo las campañas de educación deben convencer a los tomadores de decisiones y al público en general del valor que tienen los recursos forestales. Recomendamos que el sector forestal esté regido por regulaciones sencillas y comprensibles, basadas en una ciencia sólida y con aplicación consistente, y que los gobiernos trabajen con, y no en contra de, la industria. Los problemas de manejo de los bosques tropicales están lejos de ser resueltos, por lo que los científicos de las áreas biológicas y sociales deben continuar generando nuevo conocimiento para promover un manejo forestal efectivo.