Input and decay of coarse woody debris in coniferous stands in western Oregon and Washington

1982 ◽  
Vol 12 (1) ◽  
pp. 18-28 ◽  
Author(s):  
Phillip Sollins
Keyword(s):  
Tree Mortality ◽  
Large Diameter ◽  
Mineral Soil ◽  
Small Diameter ◽  
Decay Rates ◽  
Root Turnover ◽  
Permanent Plots ◽  
Old Growth ◽  
Salvage Logging ◽  
Standing Dead

At 10 locations in Oregon and Washington, tree mortality resulted in dry-matter transfer of 1.5–4.5 Mg•ha−1•year−1 of boles and branches to the forest floor and 0.3–1.3 Mg•ha−1•year−1 of large-diameter roots directly to the mineral soil. The first value is about the same as that reported for leaf fall in similar stands; the second value generally is smaller than that reported for fine root turnover. Results are based on measurements by the U.S. Forest Service spanning 16–46 years and areas as large as 42 ha. Values based on intervals < 10 years were highly variable and potentially misleading.At an old-growth Douglas-fir stand in Washington, fallen boles accounted for 81 Mg/ha, standing dead for 54 Mg/ha. Density of fallen boles averaged from 0.14 to 0.27 g/cm3 depending on decay state. Values were lower than some previously reported because (1) our sample included small-diameter fallen boles that tend to decay rapidly, and (2) we measured density with techniques that minimized compaction and shrinkage.The decay rate at the old-growth stand, calculated indirectly by dividing bole mortality (megagrams per hectare per year) by the amount (megagrams per hectare) of fallen and standing dead woody material, was 0.028 year−1. This rate, three to five times those previously calculated directly from change in density alone, was almost identical to values calculated elsewhere from change in both volume and density. Decay rates based on change in density alone include only respired and leached material and exclude the large amount of material lost in fragmentation. This study shows the value of permanent plots, undisturbed by salvage logging, for retrospective studies of decomposition, nutrient cycling, and productivity.

Dynamics of dead wood in old-growth hemlock–hardwood forests of northern Wisconsin and northern Michigan

1994 ◽  
Vol 24 (8) ◽  
pp. 1672-1683 ◽  
Author(s):  
Lucy E. Tyrrell ◽  
Thomas R. Crow
Keyword(s):  
Tree Mortality ◽  
Structural Integrity ◽  
Dead Wood ◽  
Woody Debris ◽  
Basal Area ◽  
Exponential Model ◽  
Decay Rates ◽  
Permanent Plots ◽  
Old Growth ◽  
Northern Michigan

We studied the dynamics of coarse woody debris (logs and snags) in old-growth forests by estimating rates of tree mortality, snag change, and log decay in hemlock–hardwood stands located in northern Wisconsin and northern Michigan. To estimate mortality and snag changes, we recensused live trees and dead snags in permanent plots in 15 stands. We also recorded recent mortality along transects, and noted category of mortality (standing death, breakage, or uprooting) for gap-maker trees and logs in 25 stands. Decay rates were estimated from a simple exponential model of wood density from log sections against the age of the wood since tree death, and from ages of trees growing on decaying "nurse" logs. From data obtained in permanent plots, annual tree mortality averaged 0.9% original basal area, 0.9% original live tree density, and 4.8 trees/ha. Of the three categories of tree mortality, standing death accounted for 62% of all mortality, while breakage represented 25%, and uprooting, 13%. Based on origin of logs, species composition affected category of mortality. Eastern hemlock (Tsugacanadensis (L.) Carr.) was significantly more prone to uprooting while yellow birch (Betulaalleghaniensis Britton) and paper birch (Betulapapyrifera Marsh.) were less prone to uprooting than expected if independence of species and categories of mortality were assumed (χ2 = 216.5, df = 14, p < 0.001). Changes in snags (fragmentation to shorter snags or collapse at the base) occurred for <7% of the original snags annually. Fragmentation occurred for 2.1 snags/(ha × year), and collapse for 1.3 snags/(ha × year). We estimated that it takes nearly 200 years for hemlock logs to lose structural integrity and become partially incorporated into the soil. At >350 years, the two oldest hemlock–hardwood stands had accumulated volumes of logs >65 m3/ha distributed among all decay classes, and appeared to be at a dead wood equilibrium in which rates of log production from mortality balance rates of wood loss by decay.

Évolution de la structure diamétrale et de la composition des peuplements mixtes de sapin baumier et d'épinette rouge de la forêt primitive après une coupe à diamètre limite sur l'Aire d'observation de la rivière Ouareau

2003 ◽  
Vol 33 (4) ◽  
pp. 691-704 ◽  
Author(s):  
Mathieu Fortin ◽  
Jean Bégin ◽  
Louis Bélanger
Keyword(s):  
Large Diameter ◽  
Group Analysis ◽  
Red Spruce ◽  
Balsam Fir ◽  
Permanent Plots ◽  
Betula Alleghaniensis ◽  
Mixed Stands ◽  
Old Growth ◽  
Old Growth Forest ◽  
Diameter Structure

Using data from 41 plots, the diameter structure and composition of old-growth mixed stands composed mainly of balsam fir (Abies basalmea (L.) Mill.) and red spruce (Picea rubens Sarg.) were characterized. The stand table was organized in five groups of diameter classes, and we characterized the basal area of four tree species in each group. Analysis showed that diameter structure tends toward a reverse J-shaped curve. Red spruce and yellow birch (Betula alleghaniensis Britt.) were more abundant among large diameter trees while balsam fir was more abundant among saplings. A comparison with 18 permanent plots from a diameter-limit cutting showed that plots had come back to a structure similar to that of the old-growth forest 47 years after cutting. However, spruce ratios had decreased while those of balsam fir and paper birch (Betula papyrifera Marsh.) had increased. Red spruce decrease is not due to a lack of regeneration but to overcutting. Single-tree selection method would be a suitable treatment if aimed at protecting red spruce trees up to a given diameter.

scholarly journals Does Raking Basal Duff Affect Tree Growth Rates or Mortality?

2010 ◽  
Vol 25 (4) ◽  
pp. 199-202 ◽  
Author(s):  
Erin Noonan-Wright ◽  
Sharon M. Hood ◽  
Danny R. Cluck
Keyword(s):  
Tree Growth ◽  
Growth Rates ◽  
Tree Mortality ◽  
Large Diameter ◽  
Mineral Soil ◽  
Basal Area ◽  
Basal Area Increment ◽  
National Forest ◽  
Jeffrey Pine ◽  
Pine Trees

Abstract Mortality and reduced growth rates due to raking accumulated basal duff were evaluated for old, large-diameter ponderosa and Jeffrey pine trees on the Lassen National Forest, California. No fire treatments were included to isolate the effect of raking from fire. Trees were monitored annually for 5 years after the raking treatment for mortality and then cored to measure basal area increment. Results showed that raking basal duff and litter to mineral soil from the bole out to 60 cm had no effect on basal area increment or mortality for 5 years posttreatment. Results are pertinent to managers who question whether raking basal duff will decrease tree vigor or increase tree mortality of large and old ponderosa and Jeffrey pine trees in northern California.

scholarly journals The importance of large-diameter trees to the creation of snag and deadwood biomass

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
James A. Lutz ◽  
Soren Struckman ◽  
Sara J. Germain ◽  
Tucker J. Furniss
Keyword(s):  
Tree Mortality ◽  
Woody Debris ◽  
Large Diameter ◽  
Small Diameter ◽  
Tsuga Heterophylla ◽  
Spatially Explicit ◽  
Causes Of Mortality ◽  
Small Diameter Trees ◽  
Time Required ◽  
Almost All

Abstract Background Baseline levels of tree mortality can, over time, contribute to high snag densities and high levels of deadwood (down woody debris) if fire is infrequent and decomposition is slow. Deadwood can be important for tree recruitment, and it plays a major role in terrestrial carbon cycling, but deadwood is rarely examined in a spatially explicit context. Methods Between 2011 and 2019, we annually tracked all trees and snags ≥1 cm in diameter and mapped all pieces of deadwood ≥10 cm diameter and ≥1 m in length in 25.6 ha of Tsuga heterophylla / Pseudotsuga menziesii forest. We analyzed the amount, biomass, and spatial distribution of deadwood, and we assessed how various causes of mortality that contributed uniquely to deadwood creation. Results Compared to aboveground woody live biomass of 481 Mg ha−1 (from trees ≥10 cm diameter), snag biomass was 74 Mg ha−1 and deadwood biomass was 109 Mg ha−1 (from boles ≥10 cm diameter). Biomass from large-diameter trees (≥60 cm) accounted for 85%, 88%, and 58%, of trees, snags, and deadwood, respectively. Total aboveground woody live and dead biomass was 668 Mg ha−1. The annual production of downed wood (≥10 cm diameter) from tree boles averaged 4 Mg ha−1 yr−1. Woody debris was spatially heterogeneous, varying more than two orders of magnitude from 4 to 587 Mg ha−1 at the scale of 20 m × 20 m quadrats. Almost all causes of deadwood creation varied in importance between large-diameter trees and small-diameter trees. Biomass of standing stems and deadwood had weak inverse distributions, reflecting the long period of time required for trees to reach large diameters following antecedent tree mortalities and the centennial scale time required for deadwood decomposition. Conclusion Old-growth forests contain large stores of biomass in living trees, as well as in snag and deadwood biomass pools that are stable long after tree death. Ignoring biomass (or carbon) in deadwood pools can lead to substantial underestimations of sequestration and stability.

Changes in the quantity and characteristics of large woody debris in streams of the Olympic Peninsula, Washington, U.S.A. (1982-1993)

1998 ◽  
Vol 55 (6) ◽  
pp. 1395-1407 ◽  
Author(s):  
Michael L McHenry ◽  
Eric Shott ◽  
Robert H Conrad ◽  
Glenn B Grette
Keyword(s):  
Woody Debris ◽  
Small Diameter ◽  
High Mobility ◽  
Decay Rates ◽  
Riparian Forests ◽  
Large Woody Debris ◽  
Olympic Peninsula ◽  
Old Growth ◽  
Second Growth ◽  
The Mean

We assessed the changes in large woody debris (LWD) abundance and composition at 28 sites in 27 low-gradient Olympic Peninsula streams between 1982 and 1993. The average number of pieces of debris was virtually identical (P = 0.98) in both years (50.7 versus 50.6). However, we found a significant (P <= 0.01) reduction in the total volume of LWD material in the stream sites surveyed (51.7 m3 ·100 m-1 in 1982 to 38.2 m3 ·100 m-1 in 1993). While the mean volume of second-growth derived LWD increased from 3.6 to 10.9 m3 ·100 m-1 (P < 0.01), the increase was insufficient to offset the loss of old-growth derived LWD. The mean volume of old-growth derived LWD for all sites decreased from 48.1 to 27.4 m3 ·100 m-1 between sample years (P < 0.01). The mean diameter of second-growth derived LWD was significantly larger in 1993 than in 1982, although still smaller than old-growth derived pieces. We measured a significant increase in the percentage of LWD pieces rated as highly decayed from 1982 to 1993. The results indicate that the loss of old-growth derived LWD following the removal of old-growth riparian forests is initially very rapid, followed by a slower rate of depletion associated with watershed destabilization. Inputs of LWD from second-growth riparian forests up to 73 years old were characterized by small diameter, high mobility, and high decay rates.

Differences in the brain stem terminations of large- and small-diameter vestibular primary afferents

1995 ◽  
Vol 74 (3) ◽  
pp. 1362-1366 ◽  
Author(s):  
J. A. Huwe ◽  
E. H. Peterson
Keyword(s):  
Brain Stem ◽  
Large Diameter ◽  
Small Diameter ◽  
Movement Control ◽  
Three Dimensions ◽  
Significant Shift ◽  
Axon Diameter ◽  
Vestibular Complex ◽  
The Brain ◽  
Adjacent Brain

1. We visualized the central axons of 32 vestibular afferents from the posterior canal by extracellular application of horseradish peroxidase, reconstructed them in three dimensions, and quantified their morphology. Here we compare the descending limbs of central axons that differ in parent axon diameter. 2. The brain stem distribution of descending limb terminals (collaterals and associated varicosities) varies systematically with parent axon diameter. Large-diameter afferents concentrate their terminals in rostral regions of the medial/descending nuclei. As axon diameter decreases, there is a significant shift of terminal concentration toward the caudal vestibular complex and adjacent brain stem. 3. Rostral and caudal regions of the medial/descending nuclei have different labyrinthine, cerebellar, intrinsic, commissural, and spinal connections; they are believed to play different roles in head movement control. Our data help clarify the functions of large- and small-diameter afferents by showing that they contribute differentially to rostral and caudal vestibular complex.

scholarly journals A large database supports the use of simple models of post-fire tree mortality for thick-barked conifers, with less support for other species

Fire Ecology ◽  
2020 ◽  
Vol 16 (1) ◽  
Author(s):  
C. Alina Cansler ◽  
Sharon M. Hood ◽  
Phillip J. van Mantgem ◽  
J. Morgan Varner
Keyword(s):  
Tree Mortality ◽  
Characteristic Curve ◽  
Small Diameter ◽  
Fire Effects ◽  
Tree Level ◽  
Clear Understanding ◽  
Bark Thickness ◽  
Mortality Models ◽  
Species Specific ◽  
Stem Mortality

Abstract Background Predictive models of post-fire tree and stem mortality are vital for management planning and understanding fire effects. Post-fire tree and stem mortality have been traditionally modeled as a simple empirical function of tree defenses (e.g., bark thickness) and fire injury (e.g., crown scorch). We used the Fire and Tree Mortality database (FTM)—which includes observations of tree mortality in obligate seeders and stem mortality in basal resprouting species from across the USA—to evaluate the accuracy of post-fire mortality models used in the First Order Fire Effects Model (FOFEM) software system. The basic model in FOFEM, the Ryan and Amman (R-A) model, uses bark thickness and percentage of crown volume scorched to predict post-fire mortality and can be applied to any species for which bark thickness can be calculated (184 species-level coefficients are included in the program). FOFEM (v6.7) also includes 38 species-specific tree mortality models (26 for gymnosperms, 12 for angiosperms), with unique predictors and coefficients. We assessed accuracy of the R-A model for 44 tree species and accuracy of 24 species-specific models for 13 species, using data from 93 438 tree-level observations and 351 fires that occurred from 1981 to 2016. Results For each model, we calculated performance statistics and provided an assessment of the representativeness of the evaluation data. We identified probability thresholds for which the model performed best, and the best thresholds with either ≥80% sensitivity or specificity. Of the 68 models evaluated, 43 had Area Under the Receiver Operating Characteristic Curve (AUC) values ≥0.80, indicating excellent performance, and 14 had AUCs <0.7, indicating poor performance. The R-A model often over-predicted mortality for angiosperms; 5 of 11 angiosperms had AUCs <0.7. For conifers, R-A over-predicted mortality for thin-barked species and for small diameter trees. The species-specific models had significantly higher AUCs than the R-A models for 10 of the 22 models, and five additional species-specific models had more balanced errors than R-A models, even though their AUCs were not significantly different or were significantly lower. Conclusions Approximately 75% of models tested had acceptable, excellent, or outstanding predictive ability. The models that performed poorly were primarily models predicting stem mortality of angiosperms or tree mortality of thin-barked conifers. This suggests that different approaches—such as different model forms, better estimates of bark thickness, and additional predictors—may be warranted for these taxa. Future data collection and research should target the geographical and taxonomic data gaps and poorly performing models identified in this study. Our evaluation of post-fire tree mortality models is the most comprehensive effort to date and allows users to have a clear understanding of the expected accuracy in predicting tree death from fire for 44 species.

scholarly journals Elastic Modulus and Elasticity Ratio of Malignant Breast Lesions with Shear Wave Ultrasound Elastography: Variations with Different Region of Interest and Lesion Size

Diagnostics ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1015
Author(s):  
Antonio Bulum ◽  
Gordana Ivanac ◽  
Eugen Divjak ◽  
Iva Biondić Špoljar ◽  
Martina Džoić Dominković ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Shear Wave ◽  
Large Diameter ◽  
Small Diameter ◽  
Shear Wave Elastography ◽  
Lesion Size ◽  
Ultrasound Elastography ◽  
Breast Lesions ◽  
Malignant Breast ◽  
The Impact

Shear wave elastography (SWE) is a type of ultrasound elastography with which the elastic properties of breast tissues can be quantitatively assessed. The purpose of this study was to determine the impact of different regions of interest (ROI) and lesion size on the performance of SWE in differentiating malignant breast lesions. The study included 150 female patients with histopathologically confirmed malignant breast lesions. Minimal (Emin), mean (Emean), maximal (Emax) elastic modulus and elasticity ratio (e-ratio) values were measured using a circular ROI size of 2, 4 and 6 mm diameters and the lesions were divided into large (diameter ≥ 15 mm) and small (diameter < 15 mm). Highest Emin, Emean and e-ratio values and lowest variability were observed when using the 2 mm ROI. Emax values did not differ between different ROI sizes. Larger lesions had significantly higher Emean and Emax values, but there was no difference in e-ratio values between lesions of different sizes. In conclusion, when measuring the Emin, Emean and e-ratio of malignant breast lesions using SWE the smallest possible ROI size should be used regardless of lesion size. ROI size has no impact on Emax values while lesion size has no impact on e-ratio values.

Variation in canopy gap formation among developmental stages of northern hardwood stands

1996 ◽  
Vol 26 (10) ◽  
pp. 1875-1892 ◽  
Author(s):  
Sally E. Dahir ◽  
Craig G. Lorimer
Keyword(s):  
Sugar Maple ◽  
Tree Mortality ◽  
Developmental Stages ◽  
Turnover Time ◽  
Gap Formation ◽  
Old Growth ◽  
Northern Hardwood ◽  
Hardwood Species ◽  
Shade Tolerant Species ◽  
Mature Stands

Trends in gap dynamics among pole, mature, and old-growth northern hardwood stands were investigated on eight sites in the Porcupine Mountains of western upper Michigan. Recent gaps (created between 1981 and 1992) were identified using permanent plot records of tree mortality, while older gaps (1940–1981) were identified using stand reconstruction techniques. Although canopy gaps were somewhat more numerous in pole and mature stands, gaps were <25% as large as those in old-growth stands because of smaller gap-maker size, and the proportion of stand area turned over in gaps was only about half as large. Gap makers in younger stands generally had mean relative diameters (ratio of gap-maker DBH to mean DBH of canopy trees) <1.0 and were disproportionately from minor species such as eastern hophornbeam (Ostryavirginiana (Mill.) K. Koch). Gap makers in old-growth stands had mean relative diameters >1.5 and were predominantly from the dominant canopy species. Even in old-growth forests, most gaps were small (mean 44 m2) and created by single trees. Based on the identity of the tallest gap tree in each gap, nearly all shade-tolerant and midtolerant species have been successful in capturing gaps, but gap capture rates for some species were significantly different from their relative density in the upper canopy. The tallest gap trees of shade-tolerant species were often formerly overtopped trees, averaging more than 60% of the mean canopy height and having mean ages of 65–149 years. Canopy turnover times, based on gap formation rates over a 50-year period, were estimated to average 128 years for old-growth stands dominated by sugar maple (Acersaccharum Marsh.) and 192 years for old-growth stands dominated by hemlock (Tsugacanadensis (L.) Carrière). While these estimates of turnover time are substantially shorter than maximum tree ages observed on these sites, they agree closely with independent data on mean canopy residence time for trees that die at the average gap-maker size of 51 cm DBH. The data support previous hypothetical explanations of the apparent discrepancy between canopy turnover times of <130 years for hardwood species and the frequent occurrence of trees exceeding 250 years of age.

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