scholarly journals Growth and age class distribution of Pterygophora California (Phaeophyta)

1984 ◽  
Vol 19 ◽  
pp. 93-100 ◽  
Author(s):  
RE De Wreede
Keyword(s):  
Class Distribution ◽  
Age Class

Timber production versus old-growth preservation with endogenous prices and forest age-classes

2004 ◽  
Vol 34 (6) ◽  
pp. 1296-1310 ◽  
Author(s):  
Olli Tahvonen
Keyword(s):  
Environmental Values ◽  
Timber Harvesting ◽  
Timber Production ◽  
Forest Age ◽  
Forest Land ◽  
Age Classes ◽  
Old Growth ◽  
Class Distribution ◽  
Age Class ◽  
Long Run

This study combines timber production and environmental values, applying a dynamic forest-level economic model with any number of forest age-classes. The model includes endogenous timber price or nonlinear harvesting costs and various possibilities to specify the dependence of environmental values (related e.g. to species persistence) on the forest age-class structure. The nonlinearities in the net benefits from timber production have the consequence that fluctuations in optimal timber harvesting may totally vanish or at least become smaller than in forest scheduling models without ad hoc even flow constraints. If environmental values are specified to depend on the fraction of forest land preserved as old growth, the optimal long run allocation between timber production and old growth is represented by an equilibrium continuum. Thus the optimal long run allocation depends on the initial age-class distribution. The continuum and the dependence of initial age-class distribution vanish when the rate of discount approaches zero. If the environmental values of age-classes increase smoothly with age, the long run equilibrium may simultaneously include multiple rotation periods. The model determines the optimality of producing timber and environmental values separately at different parts of the forest or at the same piece of forest land. Numerical computation suggests that the optimal solution always converges toward some optimal long run stationary age-class distribution.

Past, current, and future fire frequencies in Quebec's commercial forests: implications for the cumulative effects of harvesting and fire on age-class structure and natural disturbance-based management

2006 ◽  
Vol 36 (11) ◽  
pp. 2737-2744 ◽  
Author(s):  
Yves Bergeron ◽  
Dominic Cyr ◽  
C Ronnie Drever ◽  
Mike Flannigan ◽  
Sylvie Gauthier ◽  
...  
Keyword(s):  
Forest Management ◽  
Sustainable Forest Management ◽  
Natural Disturbance ◽  
Fire Frequency ◽  
Ecological Functions ◽  
The Past ◽  
Class Distribution ◽  
Age Class ◽  
If Current ◽  
In Fire

The past decade has seen an increasing interest in forest management based on historical or natural disturbance dynamics. The rationale is that management that favours landscape compositions and stand structures similar to those found historically should also maintain biodiversity and essential ecological functions. In fire-dominated landscapes, this approach is feasible only if current and future fire frequencies are sufficiently low compared with the preindustrial fire frequency, so a substitution of fire by forest management can occur without elevating the overall frequency of disturbance. We address this question by comparing current and simulated future fire frequency based on 2 × CO2 and 3 × CO2 scenarios to historical reconstructions of fire frequency in the commercial forests of Quebec. For most regions, current and simulated future fire frequencies are lower than the historical fire frequency, suggesting that forest management could potentially be used to maintain or recreate the age-class distribution of fire-dominated preindustrial landscapes. Current even-aged management, however, tends to reduce forest variability by, for example, truncating the natural age-class distribution and eliminating mature and old-growth forests from the landscape. Therefore, in the context of sustainable forest management, silvicultural techniques that retain a spectrum of forest compositions and structures at different scales are necessary to maintain this variability and thereby allow a substitution of fire by harvesting.

Estimating the time since fire of long-unburnt Eucalyptus salubris (Myrtaceae) stands in the Great Western Woodlands

2013 ◽  
Vol 61 (1) ◽  
pp. 11 ◽  
Author(s):  
Carl R. Gosper ◽  
Suzanne M. Prober ◽  
Colin J. Yates ◽  
Georg Wiehl
Keyword(s):  
Plant Height ◽  
Growth Ring ◽  
Plant Size ◽  
Current Approach ◽  
Significant Advance ◽  
Growth Rings ◽  
Trunk Diameter ◽  
Class Distribution ◽  
Age Class ◽  
Time Since Fire

Establishing the time since fire in infrequently burnt, yet fire-prone, communities is a significant challenge. Until this can be resolved for >50-year timeframes, our capacity to understand important ecological processes, such as the periods required for development of habitat features, will remain limited. We characterised the relationship between observable tree growth rings, plant age and plant size in Eucalyptus salubris F.Muell. in the globally significant Great Western Woodlands in south-western Australia. In the context of recent concerns regarding high woodland fire occurrence, we then used this approach to estimate the age of long-unburnt E. salubris stands, and the age-class distribution of Eucalyptus woodlands across the region. Time since fire was strongly predicted by trunk growth rings and plant size predicted growth rings with reasonable accuracy. The best model estimating growth rings contained parameters for trunk diameter, plant height and plot location, although simple models including either trunk diameter or plant height were nearly as good. Using growth ring–size relationships to date long-unburnt stands represents a significant advance over the current approach based on satellite imagery, which substantially truncates post-fire age. However, there was significant uncertainty over the best model form for estimating the time since fire of stands last burnt over 200 years ago. The management implications of predicted age-class distributions were highly dependent on both the choice of what, if any, transformation was applied to growth rings, and the theoretical age-class distribution to which the actual age-class distribution was compared.

Commercial thinning to provide harvest stability to forests with an unbalanced age class distribution

1994 ◽  
Vol 70 (3) ◽  
pp. 299-303 ◽  
Author(s):  
Mark Jamnick ◽  
Ted Needham ◽  
Marshall Bateman
Keyword(s):  
Stages Of Development ◽  
Wood Supply ◽  
Habitat Protection ◽  
Class Distribution ◽  
Age Class ◽  
Commercial Thinning ◽  
Supply Analysis ◽  
Mature Stands

Maintaining harvest stability while minimizing volume losses to mortality is a challenge in forests characterized by an unbalanced age-class distribution with an overabundance of "over-mature" and too few 'mature' stands. In many areas with this situation, emphasis is on harvesting over-mature stands and regenerating them quickly at defined density and stocking levels to minimize the eventual wood supply downfall. However, silvicultural activities in stands at other stages of development are often neglected. Wood supply analysis of a spruce-fir forest with the above characteristics indicated that both harvest stability and maintenance of the total volume harvested could be obtained by commercial thinning in mature stands. In addition, the treatment may have other benefits such as habitat protection. Defining the specifics of the treatment is required to move from consideration at the strategic level to operational implementation.

Effects of climate change and management on net climate impacts of production and utilization of energy biomass in Norway spruce with stable age-class distribution

GCB Bioenergy ◽  
2015 ◽  
Vol 8 (2) ◽  
pp. 419-427 ◽  
Author(s):  
Piritta Torssonen ◽  
Antti Kilpeläinen ◽  
Harri Strandman ◽  
Seppo Kellomäki ◽  
Kirsti Jylhä ◽  
...  
Keyword(s):  
Climate Change ◽  
Norway Spruce ◽  
Climate Impacts ◽  
Class Distribution ◽  
Age Class

The Missing Tail and Other Considerations for the Use of Fire History Models

1995 ◽  
Vol 5 (4) ◽  
pp. 197 ◽  
Author(s):  
MA Finney
Keyword(s):  
Exponential Distribution ◽  
Exponential Model ◽  
Forest Age ◽  
Age Classes ◽  
Class Distribution ◽  
Age Class ◽  
Negative Exponential Distribution ◽  
Negative Exponential Model ◽  
Negative Exponential ◽  
Tests Of Fit

This paper reviews methods used for testing the fit of the cumulative form of a negative exponential distribution to the cumulative distribution of forest age-classes. It is shown that existing methods can lead to a greater chance of falsely rejecting the fit of the negative exponential model and inferring that fire frequencies have changed through time. This results when the old-age tail of a negative exponential distribution is mathematically assumed to be present at the end of the age-class distribution. In reality, the tail is censored from sample distributions of forest age-classes. Censoring alters the shape of a cumulative age-class distribution from the straight line expected for a semi-log graph of the cumulative negative exponential model. A solution to this problem is proposed that restricts the tests-of-fit to the portion of the negative exponential distribution that overlaps with the data to be tested. The cumulative age-class distribution can then be compared directly with the cumulative of a truncated negative exponential distribution. Considerations for interpreting a poor fit are then discussed.

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