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Blowdown

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William L. Baker – One of the best experts on this subject based on the ideXlab platform.

  • Effect of vegetation on the impact of a severe Blowdown in the southern Rocky Mountains, USA
    Forest Ecology and Management, 2002
    Co-Authors: William L. Baker, Thomas T. Veblen, Jeremiah D. Lindemann, Patrick H Flaherty, Karen S. Eisenhart, Dominik Kulakowski

    Abstract:

    Abstract In October 1997, a storm with winds estimated at 200–250 km/h blew down a large percentage of trees in over 10,000 ha of subalpine forest in northern Colorado, USA. In a case study, we analyzed the effect of pre-Blowdown tree density, cover-type, and stand structural stage on the percentage of trees blown down. Low tree density led to somewhat lower levels of Blowdown than did higher density. Effects of cover-type and habitat structural stage on the pattern of damage from the Blowdown varied spatially. At lower elevations, farther from the source of the winds coming over the Continental Divide, aspen forests were less susceptible to Blowdown than expected, whereas spruce–fir forests were more susceptible than expected. At higher elevations, closer to the source of the winds, habitat structural stages representing earlier stages of stand development were much less susceptible to Blowdown than expected, whereas more advanced structural stages were generally more susceptible to Blowdown than expected. Overall, the effects of density, composition, and structural stage on the pattern of damage were modest, but evident. That there is a detectable effect of vegetation composition and structure across this large Blowdown implies that, even during extreme wind events, vegetation can influence the extent and pattern of damage, more strongly so in some places than in others.

  • Using GIS to analyse a severe forest Blowdown in the Southern Rocky Mountains
    International Journal of Geographical Information Science, 2002
    Co-Authors: Jeremiah D. Lindemann, William L. Baker

    Abstract:

    Many studies have helped us understand where Blowdowns occur, how forests regenerate and respond to large disturbances. However, few studies have analysed how physical and biological factors affect Blowdowns or interact with one another to determine susceptibility to Blowdown. These factors range from the natural physical setting to past disturbances, and human-related features, such as roads and timber harvest units. These factors were examined in this study. Patches of the blown-down forest were mapped for the 1997 Routt-Divide Blowdown, which affected over 10 000 ha of subalpine forest in north-central Colorado. A systematic sampling scheme was used to extract information on predictors for sampling points inside and outside the Blowdown. Data on predictors were used in Classification and Regression Trees (CART) and logistic regression to model Blowdown occurrence and severity. Two models were applied, and both were able to predict with an overall success rate of 75% or more. These two models produced s…

  • Attributes of Blowdown patches from a severe wind event in the Southern Rocky Mountains, USA
    Landscape Ecology, 2001
    Co-Authors: Jeremiah D. Lindemann, William L. Baker

    Abstract:

    There is increasing interest in large, infrequent, natural disturbances and how they affect ecosystems. Attributes of patches produced by some natural disturbances, such as Blowdowns, have seldom been measured. We measured attributes of patches produced by a large Blowdown (over 10 000 ha) in northern Colorado, USA in 1997. The Blowdown produced 402, 655, or 756 patches, based on three different concepts of a Blowdown patch. An inverse-J relationship shows that most patches are small in size (50% down). Blowdown patches are highly variable in their size, perimeter length, and distance to the nearest patch. The Blowdown patches are larger and have more complex shapes than patches in the surrounding forest. Mean size of Blowdown patches (25 ha) may be smaller than those of crown fires in a nearby forest, but similar total areas may be affected. About 75% of the Blowdown area is within 125 m of a forest not blown down, so natural tree regeneration should not be a problem. About 16,400 ha of mature spruce-fir forest is susceptible to first-year attack by spruce beetles, as this forest is within the expected dispersal distance (1.2 km) from Blowdown patches where beetle reproduction is favored. Timber harvest patches differ from Blowdown patches in size and distance to nearest patch. It also may be inappropriate to mimic forest Blowdown patches using timber harvesting in this region, due to the rare occurrence of large Blowdowns, their spatial restriction, and other factors.

Jeremiah D. Lindemann – One of the best experts on this subject based on the ideXlab platform.

  • Effect of vegetation on the impact of a severe Blowdown in the southern Rocky Mountains, USA
    Forest Ecology and Management, 2002
    Co-Authors: William L. Baker, Thomas T. Veblen, Jeremiah D. Lindemann, Patrick H Flaherty, Karen S. Eisenhart, Dominik Kulakowski

    Abstract:

    Abstract In October 1997, a storm with winds estimated at 200–250 km/h blew down a large percentage of trees in over 10,000 ha of subalpine forest in northern Colorado, USA. In a case study, we analyzed the effect of pre-Blowdown tree density, cover-type, and stand structural stage on the percentage of trees blown down. Low tree density led to somewhat lower levels of Blowdown than did higher density. Effects of cover-type and habitat structural stage on the pattern of damage from the Blowdown varied spatially. At lower elevations, farther from the source of the winds coming over the Continental Divide, aspen forests were less susceptible to Blowdown than expected, whereas spruce–fir forests were more susceptible than expected. At higher elevations, closer to the source of the winds, habitat structural stages representing earlier stages of stand development were much less susceptible to Blowdown than expected, whereas more advanced structural stages were generally more susceptible to Blowdown than expected. Overall, the effects of density, composition, and structural stage on the pattern of damage were modest, but evident. That there is a detectable effect of vegetation composition and structure across this large Blowdown implies that, even during extreme wind events, vegetation can influence the extent and pattern of damage, more strongly so in some places than in others.

  • Using GIS to analyse a severe forest Blowdown in the Southern Rocky Mountains
    International Journal of Geographical Information Science, 2002
    Co-Authors: Jeremiah D. Lindemann, William L. Baker

    Abstract:

    Many studies have helped us understand where Blowdowns occur, how forests regenerate and respond to large disturbances. However, few studies have analysed how physical and biological factors affect Blowdowns or interact with one another to determine susceptibility to Blowdown. These factors range from the natural physical setting to past disturbances, and human-related features, such as roads and timber harvest units. These factors were examined in this study. Patches of the blown-down forest were mapped for the 1997 Routt-Divide Blowdown, which affected over 10 000 ha of subalpine forest in north-central Colorado. A systematic sampling scheme was used to extract information on predictors for sampling points inside and outside the Blowdown. Data on predictors were used in Classification and Regression Trees (CART) and logistic regression to model Blowdown occurrence and severity. Two models were applied, and both were able to predict with an overall success rate of 75% or more. These two models produced s…

  • Attributes of Blowdown patches from a severe wind event in the Southern Rocky Mountains, USA
    Landscape Ecology, 2001
    Co-Authors: Jeremiah D. Lindemann, William L. Baker

    Abstract:

    There is increasing interest in large, infrequent, natural disturbances and how they affect ecosystems. Attributes of patches produced by some natural disturbances, such as Blowdowns, have seldom been measured. We measured attributes of patches produced by a large Blowdown (over 10 000 ha) in northern Colorado, USA in 1997. The Blowdown produced 402, 655, or 756 patches, based on three different concepts of a Blowdown patch. An inverse-J relationship shows that most patches are small in size (50% down). Blowdown patches are highly variable in their size, perimeter length, and distance to the nearest patch. The Blowdown patches are larger and have more complex shapes than patches in the surrounding forest. Mean size of Blowdown patches (25 ha) may be smaller than those of crown fires in a nearby forest, but similar total areas may be affected. About 75% of the Blowdown area is within 125 m of a forest not blown down, so natural tree regeneration should not be a problem. About 16,400 ha of mature spruce-fir forest is susceptible to first-year attack by spruce beetles, as this forest is within the expected dispersal distance (1.2 km) from Blowdown patches where beetle reproduction is favored. Timber harvest patches differ from Blowdown patches in size and distance to nearest patch. It also may be inappropriate to mimic forest Blowdown patches using timber harvesting in this region, due to the rare occurrence of large Blowdowns, their spatial restriction, and other factors.

A. Jedrzejak – One of the best experts on this subject based on the ideXlab platform.

  • A non-linear equilibrium analysis of Blowdown policy in pressure—swing—adsorption separation
    Chemical Engineering Journal, 1992
    Co-Authors: A. Bossy, Daniel Tondeur, A. Jedrzejak

    Abstract:

    Abstract Using the local non-linear equilibrium approach, we investigated pressure—swing—adsorption (PSA) cycles directed toward the removal of an adsorbable impurity present in large amounts in an inert substance. Three Blowdown policies are compared (the Blowdown is the part of the PSA cycle in which the pressure of a column is released by rejecting gas). In one such policy, the gas resulting from Blowdown is rich in the impurity and is rejected as waste. In a second policy in contrast, the production is adjusted so that the Blowdown gas is pure and is considered as a product or is reused to recompress or purge another column. The third policy is intermediate, in the sense that part of the Blowdown gas is pure and recovered, and part is impure and rejected. The equilibrium approach presented neglects mass-transfer and dispersion effects, but accounts for non-linear equilibria and variations in gas velocity. It thus allows analytical or semi-analytical expressions to be obtained for quantities such as the inert recovery ratio, and hence an easy qualitative discussion of the effects of operating parameters on the recovery. It is shown that the intermediate policy (partial recovery of the Blowdown gas) is optimal. The adsorption of methane and ethane on activated carbon from helium or hydrogen are presented as illustrations.

  • a non linear equilibrium analysis of Blowdown policy in pressure swing adsorption separation
    Chemical Engineering Journal, 1992
    Co-Authors: A. Bossy, Daniel Tondeur, A. Jedrzejak

    Abstract:

    Abstract Using the local non-linear equilibrium approach, we investigated pressure—swing—adsorption (PSA) cycles directed toward the removal of an adsorbable impurity present in large amounts in an inert substance. Three Blowdown policies are compared (the Blowdown is the part of the PSA cycle in which the pressure of a column is released by rejecting gas). In one such policy, the gas resulting from Blowdown is rich in the impurity and is rejected as waste. In a second policy in contrast, the production is adjusted so that the Blowdown gas is pure and is considered as a product or is reused to recompress or purge another column. The third policy is intermediate, in the sense that part of the Blowdown gas is pure and recovered, and part is impure and rejected. The equilibrium approach presented neglects mass-transfer and dispersion effects, but accounts for non-linear equilibria and variations in gas velocity. It thus allows analytical or semi-analytical expressions to be obtained for quantities such as the inert recovery ratio, and hence an easy qualitative discussion of the effects of operating parameters on the recovery. It is shown that the intermediate policy (partial recovery of the Blowdown gas) is optimal. The adsorption of methane and ethane on activated carbon from helium or hydrogen are presented as illustrations.