Coarse woody debris in the southeastern Canadian boreal forest: composition and load variations in relation to stand replacement

2000 ◽  
Vol 30 (5) ◽  
pp. 674-687 ◽  
Author(s):  
C Hély ◽  
Y Bergeron ◽  
M D Flannigan

Quantities and structural characteristics of coarse woody debris (CWD) (logs and snags) were examined in relation to stand age and composition in the Canadian mixedwood boreal forest. Forty-eight stands originating after fire (from 32 to 236 years) were sampled on mesic clay deposits. The point-centered quadrant method was used to record canopy composition and structure (living trees and snags). The line-intersect method was used to sample logs of all diameters. Total log load, mean snag density, and volume per stand were similar to other boreal stands. Linear and nonlinear regressions showed that time since fire and canopy composition were significant descriptors for log load changes, whereas time since fire was the only significant factor for snag changes. Coarse woody debris accumulation models through time since fire were different from the U-shaped model because the first initial decrease from residual pre-disturbance debris was missing, the involved species had rapid decay rates with no long-term accumulation, and the succession occurred from species replacement through time.


2018 ◽  
Vol 48 (4) ◽  
pp. 399-411 ◽  
Author(s):  
Praveen Kumar ◽  
Han Y.H. Chen ◽  
Sean C. Thomas ◽  
Chander Shahi

Although the importance of coarse woody debris (CWD) to understory species diversity has been recognized, the combined effects of CWD decay and substrate species on abundance and species diversity of epixylic vegetation have received little attention. We sampled a wide range of CWD substrate species and decay classes, as well as forest floors in fire-origin boreal forest stands. Percent cover, species richness, and evenness of epixylic vegetation differed significantly with both CWD decay class and substrate species. Trends in cover, species richness, and evenness differed significantly between nonvascular and vascular taxa. Cover, species richness, and species evenness of nonvascular species were higher on CWD, whereas those of vascular plants were higher on the forest floor. Epixylic species composition also varied significantly with stand ages, overstory compositions, decay classes, substrate species, and their interactions. Our findings highlight strong interactive influences of decay class and substrate species on epixylic plant communities and suggest that conservation of epixylic diversity would require forest managers to maintain a diverse range of CWD decay classes and substrate species. Because stand development and overstory compositions influence CWD decay classes and substrate species, as well as colonization time and environmental conditions in the understory, our results indicate that managed boreal landscapes should consist of a mosaic of different successional stages and a broad suite of overstory types to support diverse understory plant communities.



2006 ◽  
Vol 36 (2) ◽  
pp. 460-466 ◽  
Author(s):  
Leslie R Paul ◽  
Bill K Chapman ◽  
Christopher P Chanway

Tuberculate ectomycorrhizae (TEM) have been observed in decaying coarse woody debris (CWD) and may play a role in the nitrogen economy of forests. This study evaluates the occurrence of Suillus tomentosus (Kauff.) Singer, Snell and Dick TEM within CWD in Pinus contorta Dougl. ex Loud. var. latifolia Engelm. stands and relates their occurrence to CWD and soil characteristics as well as stand age. TEM were more abundant in the basal end of CWD incorporated in the forest floor than in the middle and top portions. Tubercle abundance was positively correlated with moisture and texture of CWD, degree of incorporation of CWD into the forest floor, and the amount of roots within CWD. There were significantly more TEM in CWD in young stands than in old stands and on sites with granitic soils than on sites with basaltic soils. Highly degraded CWD that is well incorporated in the forest floor appears to be an important microhabitat for the formation and occurrence of TEM.



2010 ◽  
Vol 26 (4) ◽  
pp. 467-471 ◽  
Author(s):  
Lisa B. Kissing ◽  
Jennifer S. Powers

The ecological importance of trees lasts much longer than their life spans. Standing dead trees (snags) and fallen trunks and branches are an important component of above-ground carbon stocks and nutrient reserves, provide habitat for wildlife, and interact with disturbance regimes (e.g. by serving as fuel for fires) (Clark et al. 2002, Harmon et al. 1986, Pyle et al. 2008). Despite these diverse functions, woody debris stocks remain poorly quantified in tropical forests in general (Brown 1997), and in tropical dry forests in particular (Harmon et al. 1995). More empirical studies of the patterns of woody debris and processes that control its dynamics are needed to understand its role in global biogeochemical cycles and for ecosystem simulation models, many of which do not represent coarse woody debris (CWD) as a separate pool (Cornwell et al. 2009).



2019 ◽  
Vol 438 ◽  
pp. 96-102 ◽  
Author(s):  
Loretta G. Garrett ◽  
Mark O. Kimberley ◽  
Graeme R. Oliver ◽  
Mallory Parks ◽  
Stephen H. Pearce ◽  
...  


2008 ◽  
Vol 38 (7) ◽  
pp. 1911-1923 ◽  
Author(s):  
Thomas A. Kurkowski ◽  
Daniel H. Mann ◽  
T. Scott Rupp ◽  
David L. Verbyla

Postfire succession in the Alaskan boreal forest follows several different pathways, the most common being self-replacement and species-dominance relay. In self-replacement, canopy-dominant tree species replace themselves as the postfire dominants. It implies a relatively unchanging forest composition through time maintained by trees segregated within their respective, ecophysiological niches on an environmentally complex landscape. In contrast, species-dominance relay involves the simultaneous, postfire establishment of multiple tree species, followed by later shifts in canopy dominance. It implies that stand compositions vary with time since last fire. The relative frequencies of these and other successional pathways are poorly understood, despite their importance in determining the species mosaic of the present forest and their varying, potential responses to climate changes. Here we assess the relative frequencies of different successional pathways by modeling the relationship between stand type, solar insolation, and altitude; by describing how stand age relates to species composition; and by inferring successional trajectories from stand understories. Results suggest that >70% of the study forest is the product of self-replacement, and tree distributions are controlled mainly by the spatial distribution of solar insolation and altitude, not by time since last fire. As climate warms over the coming decades, deciduous trees will invade cold sites formerly dominated by black spruce, and increased fire frequency will make species-dominance relay even rarer.



2006 ◽  
Vol 36 (7) ◽  
pp. 1770-1780 ◽  
Author(s):  
Yan Boulanger ◽  
Luc Sirois

In this study, postfire coarse woody debris (CWD) dynamics in northern Quebec, Canada, were assessed using a 29-year chronosequence. Postfire woody-debris storage, decomposition rates, and variation of nitrogen and carbon contents of black spruce CWD (Picea mariana (Mill.) BSP) are estimated. The decomposition rate for postfire snags is exceptionally slow (k = 0.00), while the decomposition rate for logs (k = 0.019–0.021) is within previously recorded values for the boreal forest. The low decomposition rate for snags could be related to low moisture content associated with the position of debris and fast bark shedding. Given the low CWD decomposition rates and CWD storage (21.3–66.8 m3·ha–1), carbon losses from postfire CWD are relatively low, varying between 35.5 and 128.8 kg·ha–1·year–1 at the study sites. The nitrogen content in CWD drops quickly between living trees and snags and increases slightly with time since fire in logs. Nitrogen content is not related to wood density or to moisture content of deadwood. Rapid loss of nitrogen is associated with fast decomposition of subcortical tissues, leaching, and insect comminution. The increase in nitrogen content at the oldest site could result from asymbiotic nitrogen fixation, although a longer time span in the chronosequence would probably have revealed a greater nitrogen gain in increasingly decayed CWD.



2008 ◽  
Vol 256 (4) ◽  
pp. 548-557 ◽  
Author(s):  
P.N. Beets ◽  
I.A. Hood ◽  
M.O. Kimberley ◽  
G.R. Oliver ◽  
S.H. Pearce ◽  
...  


2004 ◽  
Vol 34 (4) ◽  
pp. 763-777 ◽  
Author(s):  
Raija Laiho ◽  
Cindy E Prescott

We synthesize current information on input, accumulation, and decay of coarse woody debris (CWD) compared with other aboveground litter to assess the role of CWD in the nutrient cycles of northern coniferous forests. CWD contributes between 3% and 73% of aboveground litter input, but <20% of N, P, K, and Ca. Although CWD accounts for up to 54% of accumulated organic matter (including forest floor and soil), it contributes <5% of the N, <10% of the P, and <25% of the K, Ca, and Mg. Decay rates of CWD in northern forests range from 0.0025 to 0.071 year-1. Nitrogen or P concentrations in CWD increase during decay, depending on the initial N/P ratio, which eventually converges at about 20. CWD is initially a sink for N and (or) P, whichever is least available, but becomes a source later in decay. CWD contributes <5% of the N released annually. There is little evidence that CWD retains significant amounts of excess N following disturbance. We conclude that CWD is of minor importance in the nutrient cycles of northern coniferous forests, and that guidelines for CWD retention should be based on other perceived benefits of CWD.



2009 ◽  
Vol 2009 ◽  
pp. 1-13 ◽  
Author(s):  
Louis Duchesne ◽  
Rock Ouimet

This study reports on the contemporary structure, composition, and dynamics of the pristine northern boreal forest in Quebec, Canada, associated with air temperature, precipitation, and soil texture, using 147 permanent sample plots located at the limit of continuous forest in Quebec. The results show that tree species composition of stands is associated with stand age, soil texture, air temperature, and precipitation regime. After establishment of the pioneer cohort, the postsuccessional stand dynamics differed among temperature and precipitation regimes, probably because of their influence on tree growth. Our results support the hypothesis that shifts in forest composition related to stand dynamics and the subsequent senescing phase associated with the old growth stage generally occur sooner and proceed faster on more fertile sites due to quicker growth and the subsequent earlier mortality of pioneer species. This study suggests that climate warming should accelerate the successional dynamics of these ecosystems through its positive influence on tree growth.



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