Time since death and fall of Norway spruce logs in old-growth and selectively cut boreal forest

2002 ◽  
Vol 32 (10) ◽  
pp. 1801-1812 ◽  
Author(s):  
Ken Olaf Storaunet ◽  
Jørund Rolstad
Keyword(s):  
Norway Spruce ◽  
Classification Systems ◽  
Time Since Death ◽  
Forest Stands ◽  
Old Growth ◽  
South Central ◽  
Decay Class ◽  
Negative Exponential Distribution ◽  
Decomposition Time ◽  
Negative Exponential

To estimate the age of Norway spruce (Picea abies (L.) Karst.) logs by means of decay classes, and to assess how long it takes for downed logs to decompose, we dated logs dendrochronologically by applying 5- and 8-grade decay classification systems. Study sites were chosen in old-growth and previously selectively cut forest stands in boreal south-central Scandinavia; 113 logs were dated to the number of years since death, 120 were dated to the number of years since fall, and 61 logs were dated to both. The number of years from death to fall showed a negative exponential distribution, with a mean of 22 years and a range of 0–91 years. Decay classes of logs (8-grade scale) reflected time since fall (R2 = 0.58) better than time since death (R2 = 0.27) in a linear regression model. This result is due to the lower decomposition rate of standing snags. Therefore, the decomposition time of logs should be divided into two periods: time from death to fall, which varies considerably, and time after fall, which appears to follow a linear relationship with decay class. The model predicted that it takes 100 years after fall for downed logs to decompose completely (reaching decay class 8) in old-growth stands. Logs in selectively cut stands appeared to decompose faster (64 years), which is explained by a sample shortage of old logs resulting from previous cuttings. We conclude that the decomposition time of downed logs may be severely underestimated when data is retrospectively compiled from previously logged forest stands.

How long do Norway spruce snags stand? Evaluating four estimation methods

2004 ◽  
Vol 34 (2) ◽  
pp. 376-383 ◽  
Author(s):  
Ken Olaf Storaunet ◽  
Jørund Rolstad
Keyword(s):  
Norway Spruce ◽  
Bark Beetles ◽  
Survival Function ◽  
Estimation Methods ◽  
Time Since Death ◽  
Calculation Methods ◽  
Old Growth ◽  
Standing Time ◽  
South Central ◽  
Old Growth Forest

We estimated time from death to fall (standing time) of Norway spruce (Picea abies (L.) Karst.) snags in a submountainous old-growth forest in south-central Norway, applying four calculation methods to 124 dendro chrono logically cross-dated still-standing snags and 64 fallen logs. The calculation methods consistently estimated expected standing time of snags at 26–34 years, with a median of 16–21 years and 20% of snags standing for >48–58 years. The survival function from all methods took the approximate form of a negative exponential, with a 3%–4% annual fall rate for snags. In the distribution of time since death, a small peak in dead trees 20–30 years ago (late 1970s) coincides with a historic epidemic of bark beetles. The method using only time since death of still-standing snags appears to be the most feasible for estimating total standing time of snags in old-growth forests with constant tree mortality.

Modeling dead wood in Fennoscandian old-growth forests dominated by Norway spruce

2004 ◽  
Vol 34 (5) ◽  
pp. 1025-1034 ◽  
Author(s):  
Thomas Ranius ◽  
Bengt Gunnar Jonsson ◽  
Nicholas Kruys
Keyword(s):  
Norway Spruce ◽  
Residence Time ◽  
Tree Mortality ◽  
Woody Debris ◽  
National Forest Inventory ◽  
Mortality Data ◽  
Negative Exponential Distribution ◽  
Computer Simulation Program ◽  
Number Of Stems ◽  
Negative Exponential

If equilibrium is assumed in unmanaged forests, the volume of coarse woody debris (CWD), VCWD, may be calculated from (i) the volume of living trees, Vliving, (ii) average volume of a dead stem in relation to when it was alive, k, (iii) tree mortality rate, m, and (iv) residence time of CWD, t, by the equation VCWD = Vlivingkmt. We parameterized this equation with data from Norway spruce (Picea abies (L.) Karst.) dominated forests in Fennoscandia. The Vliving was assumed to be directly proportional to forest productivity. Tree mortality data were from the National Forest Inventory, while it was difficult to find quantitative data on k and t. The predicted amounts (74–138 m3/ha, with larger amounts in the south) and size distribution (a negative exponential distribution of the number of stems) of CWD corresponded fairly well to averages from field inventories. By using a computer simulation program, the variability in tree mortality, density of living trees, and residence time of CWD were considered. In the simulations, the amount of CWD varied widely between 1-ha plots, especially for individual decay classes. Therefore, this model could be used to predict averages from larger landscapes unaffected by large disturbances, while no model can predict the amount of CWD at individual plots.

scholarly journals Mesoscale Variation in Snag and Hardwood Densities and Sizes in Old-Growth Forests in Western Oregon

2012 ◽  
Vol 27 (1) ◽  
pp. 12-17 ◽  
Author(s):  
Adrian Ares ◽  
Cheryl Bright ◽  
Klaus Puettmann
Keyword(s):  
Pacific Northwest ◽  
Spatial Scales ◽  
Coast Range ◽  
Willamette Valley ◽  
Old Growth ◽  
Regional Patterns ◽  
Negative Exponential Distribution ◽  
Wide Range ◽  
Old Growth Forests ◽  
Negative Exponential

Abstract Snags and hardwoods contribute to biological, structural, and functional diversity in old-growth forests. In the US Pacific Northwest, only general knowledge about regional patterns is available to determine target density of snags and hardwood trees. To investigate their variability at relevant scales for silviculture, we examined snag and hardwood densities and sizes in 20 old-growth units in northern and southern aspects in the Coast Range and the Willamette Valley foothills of Oregon. Snag densities varied largely between subregions and aspects, with aspect affecting densities more than subregion. In the Coast Range, snag density was 2.8 times greater on northern aspects than on southern aspects, whereas in the Willamette Valley foothills snag density was 1.4 times greater on northern aspects than on southern aspects. Density of snags larger than 101.6 cm in diameter was very low. Hardwood densities were also greater on northern aspects than on southern aspects. The negative exponential distribution of hardwood density frequency by size classes could be explained by cohort growth under a wide range of competitive pressures or repeated-recruitment events. Aspect and subregion should be taken into account when defining management targets. Allowing for flexibility at these smaller spatial scales would better reflect the variability in ecological conditions and land use history that led to the development of old-growth stands.

The Comparison Between the Bayes Estimator and the Maximum Likelihood Estimator of the Reliability Function for Negative Exponential Distribution

2018 ◽  
pp. 439
Author(s):  
Hazim Mansour Gorgees ◽  
Bushra Abdualrasool Ali ◽  
Raghad Ibrahim Kathum
Keyword(s):  
Maximum Likelihood ◽  
Maximum Likelihood Estimator ◽  
Exponential Distribution ◽  
Reliability Function ◽  
Bayes Estimator ◽  
Likelihood Estimator ◽  
Monte Carlo Simulation Technique ◽  
Negative Exponential Distribution ◽  
Negative Exponential ◽  
Better Than

     In this paper, the maximum likelihood estimator and the Bayes estimator of the reliability function for negative exponential distribution has been derived, then a Monte –Carlo simulation technique was employed to compare the performance of such estimators. The integral mean square error (IMSE) was used as a criterion for this comparison. The simulation results displayed that the Bayes estimator performed better than the maximum likelihood estimator for different samples sizes.

Ehrenfest urn models

1965 ◽  
Vol 2 (02) ◽  
pp. 352-376 ◽  
Author(s):  
Samuel Karlin ◽  
James McGregor
Keyword(s):  
Exponential Distribution ◽  
Continuous Time ◽  
Random Variables ◽  
Independent Random Variables ◽  
Urn Models ◽  
Time Intervals ◽  
Negative Exponential Distribution ◽  
Negative Exponential ◽  
Random Times

In the Ehrenfest model with continuous time one considers two urns and N balls distributed in the urns. The system is said to be in stateiif there areiballs in urn I, N −iballs in urn II. Events occur at random times and the time intervals T between successive events are independent random variables all with the same negative exponential distributionWhen an event occurs a ball is chosen at random (each of theNballs has probability 1/Nto be chosen), removed from its urn, and then placed in urn I with probabilityp, in urn II with probabilityq= 1 −p, (0 <p< 1).

scholarly journals Differentiating mature and old-growth forests in the Upper Foothills and Subalpine Subregions of west-central Alberta

2003 ◽  
Vol 79 (3) ◽  
pp. 602-612 ◽  
Author(s):  
Luigi E Morgantini ◽  
John L Kansas
Keyword(s):  
Forest Management ◽  
Growth Index ◽  
Tree Height ◽  
Tree Age ◽  
Old Growth ◽  
West Central ◽  
Decay Class ◽  
Management Area ◽  
Growth Attributes ◽  
Live Tree

Weyerhaeuser Company Ltd. is developing harvest strategies that will maintain appropriate levels of late to very late seral stages ("old growth") in its Drayton Valley Forest Management Area. This management area encompasses 490 570 ha in the Foothills and Rocky Mountain Natural Regions of west-central Alberta. In planning for future forest landscapes, Weyerhaeuser intends to maintain a range of age structures consistent with the ecological processes characteristic of each natural region and subregion. The absence of a discrete point separating mature forest from old growth means that the age at which a stand is currently identified as "old growth" and subject to special management practices is arbitrary. In a research study initiated in the summer of 2000, we seek to understand the differences in structure and composition between forests of various ages and topographic site conditions (elevation, aspect, and slope angle). Using 95 sampling plots in a 123-km2 study area in the Upper Foothills and Subalpine Natural Subregions, we quantified vegetation structure and composition for stands ranging in age from 70 to 300 years. Variables measured and analysed included live-tree height and diameter, snag density, diameter and decay class, downed woody material volume, diameter and decay class, vascular plant species richness, sapling and regeneration density, and duff depth. An old-growth index was developed for each sampled stand that took into account multiple attributes. Preliminary results indicate that specific attributes (snag basal area and density, decay stage and density of downed woody material, variation in live-tree age, and variation in live-tree height and age) separate a younger forest from a more mature one and hence may describe "old-growth" conditions. The age of onset of these old-growth attributes is variable but appears to occur between 160 and 180 years. Key factors other than stand age that contribute to or modify the development of old-growth attributes (as measured by the old-growth index) are elevation and moisture regime (as modified by site position). Further investigation is required to more accurately assess the effect of site factors on old-growth attributes. These results are now used by Weyerhaeuser to address retention of late seral stages in long-term forest planning. Key words: old growth, mature forests, old growth protection, forest management, Alberta, Weyerhaeuser, Rocky Mountains foothills

The relationship of buried, germinating seeds to vegetation in an old-growth Colorado subalpine forest

1978 ◽  
Vol 56 (13) ◽  
pp. 1505-1509 ◽  
Author(s):  
Stephen A. Whipple
Keyword(s):  
Subalpine Forest ◽  
Forest Species ◽  
Forest Stands ◽  
Rapid Loss ◽  
Old Growth ◽  
Old Growth Forest ◽  
Viable Seeds ◽  
Relationship Of ◽  
Germinating Seeds ◽  
The Relationship

Species of buried, germinating seeds and species occurring in the vegetation are compared for two Colorado subalpine forest stands, one dry and one mesic, both over 325 years old. The total numbers of seeds found were small and the correspondence with species in the vegetation was poor. This is consistent with reports from other old-growth forests and may be accounted for by a combination of low seed input and rapid loss of viable seeds from the soil reservoir for old-growth forest species.

scholarly journals Allometric equations for estimating tree biomass in restored mixed-species Atlantic Forest stands

2014 ◽  
Vol 14 (2) ◽  
Author(s):  
Lauro Rodrigues Nogueira Júnior ◽  
Vera Lex Engel ◽  
John A. Parrotta ◽  
Antonio Carlos Galvão de Melo ◽  
Danilo Scorzoni Ré
Keyword(s):  
Atlantic Forest ◽  
Forest Restoration ◽  
Global Climate ◽  
Allometric Equations ◽  
Predictor Variables ◽  
Forest Stands ◽  
Tree Biomass ◽  
Biomass Equation ◽  
South Central ◽  
Biomass Equations

Restoration of Atlantic Forests is receiving increasing attention because of its role in both biodiversity conservation and carbon sequestration for global climate change mitigation. This study was carried out in an Atlantic Forest restoration project in the south-central region of São Paulo State - Brazil to develop allometric equations to estimate tree biomass of indigenous tree species in mixed plantations. Above and below-ground biomass (AGB and BGB, respectively), stem diameter (DBH: diameter at 1.3 m height), tree height (H: total height) and specific wood density (WD) were measured for 60 trees of 19 species. Different biomass equations (linear and nonlinear-transformed) were adjusted to estimate AGB and BGB as a function of DBH, H and WD. For estimating AGB and BGB, the linear biomass equation models were the least accurate. The transformed nonlinear biomass equation that used log DBH2, log H and log WD as predictor variables were the most accurate for AGB and the transformed nonlinear biomass equations that used log DBH2*WD as predictor variables were the most accurate for BGB. It is concluded that these adjusted equations can be used to estimate the AGB and BGB in areas of the studied project. The adjusted equations can be recommended for use elsewhere in the region for forest stands of similar age, tree size ranges, species composition and site characteristics.

scholarly journals Traffic Characteristics for A Freeway Normal Section at Baghdad City

2018 ◽  
Vol 7 (4.20) ◽  
pp. 283
Author(s):  
Jalal T. S. Al-Obaedi ◽  
Muhanad Al-temimy ◽  
Amal Ali
Keyword(s):  
Traffic Flow ◽  
Research Work ◽  
Distribution Data ◽  
Lane Changing ◽  
Traffic Characteristics ◽  
Traffic Lane ◽  
Video Recordings ◽  
Negative Exponential Distribution ◽  
Headway Distribution ◽  
Negative Exponential

Traffic characteristics at highway sections are usually varying based on many factors including type of highways, geometric design and drivers’ behavior at a given area (country).  This paper focuses on finding the characteristics for traffic on selected normal freeway section at Baghdad city.  Video recordings and speed gun are used to collect data from a basic freeway section within Mohammed Al-Qassim freeway that represents the busiest freeway at the city.  The estimated characteristics include the distribution of traffic among the available lanes, desired speed of traffic, lane-changing frequency, and headway distribution.  For traffic distribution, it is found that traffic concentrates more in off side lane compared with other lanes for moderate to high flow rates.  Regression models have been developed based on the available lane distribution data.  The lane found to be increased with the increasing of traffic flow and the desired speeds found to be normally distributed.  Examining the headway data shows that the shifted negative exponential distribution can be used to represent the headway distribution for low to intermediate traffic flow only.  The findings of this work provides a good database for traffic characteristics for Iraqi highways as little effort has been given in previous research work.  

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