Browsing by Autor "Michelle A. Pinard"

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Cost and Efficiency of Cutting Lianas in a Lowland Liana Forest of Bolivia<sup>1</sup>
(Wiley, 2001) Diego R. Pérez‐Salicrup; Alberto Claros; Rudy Guzmán; Juan Carlos Licona; Fredy Ledezma; Michelle A. Pinard; Francis E. Putz
ABSTRACT Liana cutting is a commonly suggested silvicultural practice aimed at reducing the negative impacts of lianas on timber production, but few experimental studies have been conducted to evaluate the cost and efficiency of this practice. In this study, we estimated the cost of cutting lianas in 12 plots of 0.25 ha each in a densely liana‐infested forest of lowland Bolivia, and evaluated the efficiency of this silvicultural treatment in terms of the proportion of lianas missed, the density of resprouting liana stumps, and the number of liana‐infested trees after two years of an experimental liana treatment. The cost of cutting lianas in this forest by locally hired laborers was 23.6 (SE = 2.48) person‐hours/ha. Considering local cost of labor and the U.S.–Bolivian currency exchange rate at the time of the study, this figure translates to ca $15/ha. Liana density decreased from 2471 (SE = 104.3) to 130 (SE = 24.2) liana stems >2 cm/ha immediately after cutting, because 5.5 percent of lianas were left uncut (missed). Slender lianas were missed more often than lianas with large‐diameter stems. Liana species that grow 2–3 m before they start to twine were also frequently missed. Twenty‐two percent of liana stumps a2 cm sprouted after cutting. Liana stumps with larger diameters sprouted more than stumps with smaller diameters. Most liana stumps produced only two sprouts. Two years after cutting, 78 percent of trees had no living lianas in their crowns, in contrast to only 13 percent liana‐free trees in the control plots. Sixty‐four percent of trees still had hanging dead lianas two years after cutting, but only 23 percent of trees were reinvaded by lianas using dead liana stems as trellises. Liana cutting can efficiently reduce the number of lianas in liana‐infested forests, and the effects of cutting lianas last for at least two years; however, the treatment is expensive. Thus, we recommend that it is better to view liana cutting as a preventive activity to avoid liana infestation, rather than as a corrective measure after poor management. Liana cutting can be easily conducted along with other reduced‐impact logging practices. RESUMES El corte de lianas es una práctica de manejo comunmente recomendada para reducir los impactos negatives de las lianas en la producción forestal, pero existen pocos estudios experimentales que evaluen los costos y la eficiencia de dicha práctica. En este estudio estimamos el costo del corte de lianas en 12 parcelas de 0.25 ha cada una en un bosque densamente infestado de lianas en Bolivia, y evaluamos la eficiencia de este tratamiento en términos de la proporción de lianas no cortadas, de la densidad de lianas que rebrotan, y el número de árboles infestados con lianas dos años despues de un tratamiento del corte experimental de lianas. El costo de cortar lianas en este bosque por trabajadores locales fue de 23.6 (EE=2.48) horas‐persona/ha. Considerando el costo de labor y el intercambio monetario entre Bolivia y los EUA al tiempo del experimento, esta figura se traduce a ca 15 dólares EUA/ha. La densidad de lianas se redujo de 2471 (EE=104.3) a 130 (EE = 24.2) tallos de liana ≥2 cm/ha inmediatamente despues del corte, porque 5.5 por ciento de las lianas no se cortaron. Las lianas más delgadas fueron cortadas con mayor frequencia que las lianas más gruesas. Las especies de lianas que crecen
Ecological characterization of tree species for guiding forest management decisions in seasonally dry forests in Lomerıo, Bolivia
(Elsevier BV, 1999) Michelle A. Pinard; Francis E. Putz; Damián I. Rumiz; Rudy Guzmán; Antônio Augusto Jardim
Fire resistance and bark properties of trees in a seasonally dry forest in eastern Bolivia
(Cambridge University Press, 1997) Michelle A. Pinard; Jean M. Huffman
ABSTRACT As forest fragmentation and intentional burning of grasslands increase, the frequency of fires penetrating the dry and subhumid tropical forests of Bolivia is also likely to increase. To expand our understanding of the role of fire in tropical dry forest, the physical and thermal properties of barks of tree species were studied to determine their relative resistances to cambial damage by fire. For 16 tree species found in the dry forest of the Lomerío region of eastern Bolivia, bark thickness, moisture content, and specific gravity were measured. Insulating capabilities of bark were measured by obtaining cambial and surface temperatures during experimental wick fires. Bark thickness on trees 5-100 cm dbh (diameter at 1.4 m) ranged from 2–51 mm and both thick- and thin-barked species were represented. For all species, bark thickness increased as stem diameter increased. Bark thickness explained more (63%) of the variation in peak cambial temperatures during fires than did bark moisture content (4%) or specific gravity (1%). A threshold bark thickness of 18 mm was associated with the ability to withstand lethal cambial temperatures during the experimental, low intensity fires. For 13 of the 16 species included in this study, trees ≤20 cm dbh have bark thickness below the threshold 18 mm and, therefore, are likely to experience cambial injury from low intensity fires. Our results suggest that the forest presently characteristic of the Lomerío region did not develop with frequent fires and that species composition is likely to be substantially affected by an increase in fire frequency.
Sustaining conservation values in selectively logged tropical forests: the attained and the attainable
(Wiley, 2012) Francis E. Putz; Pieter A. Zuidema; T.J. Synnott; Marielos Peña‐Claros; Michelle A. Pinard; Douglas Sheil; Jerome K. Vanclay; Plínio Sist; Sylvie Gourlet‐Fleury; Bronson W. Griscom
Abstract Most tropical forests outside protected areas have been or will be selectively logged so it is essential to maximize the conservation values of partially harvested areas. Here we examine the extent to which these forests sustain timber production, retain species, and conserve carbon stocks. We then describe some improvements in tropical forestry and how their implementation can be promoted. A simple meta‐analysis based on >100 publications revealed substantial variability but that: timber yields decline by about 46% after the first harvest but are subsequently sustained at that level; 76% of carbon is retained in once‐logged forests; and, 85–100% of species of mammals, birds, invertebrates, and plants remain after logging. Timber stocks will not regain primary‐forest levels within current harvest cycles, but yields increase if collateral damage is reduced and silvicultural treatments are applied. Given that selectively logged forests retain substantial biodiversity, carbon, and timber stocks, this “middle way” between deforestation and total protection deserves more attention from researchers, conservation organizations, and policy‐makers. Improvements in forest management are now likely if synergies are enhanced among initiatives to retain forest carbon stocks (REDD+), assure the legality of forest products, certify responsible management, and devolve control over forests to empowered local communities.
Tree mortality and vine proliferation following a wildfire in a subhumid tropical forest in eastern Bolivia
(Elsevier BV, 1999) Michelle A. Pinard; Francis E. Putz; Juan Carlos Licona