scholarly journals Time since fire and prior fire interval shape woody debris dynamics in obligate‐seeder woodlands

Ecosphere ◽  
2019 ◽  
Vol 10 (12) ◽  
Author(s):  
Carl R. Gosper ◽  
Colin J. Yates ◽  
Elizabeth Fox ◽  
Suzanne M. Prober

Forests ◽  
2019 ◽  
Vol 10 (5) ◽  
pp. 436 ◽  
Author(s):  
Jamie Burton ◽  
Jane Cawson ◽  
Philip Noske ◽  
Gary Sheridan

High frequency wildfires can shift the structure and composition of obligate seeder forests and initiate replacement with alternative vegetation states. In some forests, the alternative stable state is drier and more easily burned by subsequent fires, driving a positive feedback that promotes further wildfire and perpetuates alternative stable states. Mountain Ash (Eucalyptus regnans (F.Muell.)) forests are highly valued for their biodiversity, water, timber and carbon. Fires are a natural part of the lifecycle of these forests, but too frequent fires can eliminate Mountain Ash and trigger a transition to lower stature, non-eucalypt forests which are dominated by understorey species. This study sought to better understand the fuel moisture dynamics of alternative stable states resulting from high frequency wildfires. A vegetation mosaic in the Central Highlands, Victoria created a unique opportunity to measure fuel moisture in adjacent forest stands that differed in overstorey species composition and time since fire. Specifically, we measured fuel moisture and microclimate at two eucalypt sites (9 and 79 years old) and three non-eucalypt sites (two 9 year old and one 79 year old). Fuel availability, defined here as the number of days surface fuels were below 16% and dry enough to ignite and sustain fire, was calculated to estimate flammability. Fuel availability differed between sites, particularly as a function of time since fire, with recently burnt sites available to burn more often (4–17 versus 0–3 days). There were differences in fuel availability between non-eucalypt sites of the same age, suggesting that high frequency fire does not always lead to the same vegetation condition or outcome for fuel availability. This indicates there is potential for both positive and negative flammability feedbacks following state transition depending on the composition of the non-eucalypt state. This is the first study to provide empirical insight into the fuel moisture dynamics of alternative stable states in Mountain Ash forests.



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.



2007 ◽  
Vol 55 (2) ◽  
pp. 91 ◽  
Author(s):  
Peter J. Myerscough ◽  
Peter J. Clarke

Four fires burned vegetation on a sand plain on a 4-km stretch of Pleistocene beach ridges between 1980–1981 and 1998. Fires of 1980–81 and 1991 burned the whole area. Those of 1994 and 1998 burned only parts of it. Cover of individual species and bare ground was scored on permanent plots at intervals between 1990 and 1996. Ordination and generalised linear model analysis of the data showed strong spatial variation between dry and wet heaths, four transects and plots within transects. This was strictly conserved through time, owing to the rapid regrowth of abundant resprouting species, most of which, after 1 year, showed little change in cover with increasing time-since-fire. Vegetation of the dry and wet heaths showed no detectable convergence or divergence in similarity with time-since-fire or variation of interval between fires. Changes with time-since-fire were found, and some change with the length of fire interval, owing to variation in cover of obligate-seeder species, which increased steadily with time up to 10 years since fire, and showed some decrease when fire interval decreased to 3.75 years. At 10 years since fire, obligate-seeder species reached ~25% of the totalled cover scores for all species, with 75% from resprouting species. Dry and wet heath were broadly similar in their general pattern of regrowth after fire, but in dry heath bare ground was more slowly covered than in wet heath, and wet heath had a higher cover of monocotyledons, especially restiads and sedges. Wet heath was more flammable than dry heath in the patchy fire of 1998. The heaths observed appeared highly resilient to recent fire regimes. Resprouting species always dominated their canopy; none of their obligate-seeding species formed a dominant overstorey canopy.



2009 ◽  
Vol 61 (1) ◽  
pp. 107-115 ◽  
Author(s):  
Mathrubutham Ravikumar ◽  
Kandikere R. Sridhar ◽  
Thangaraju Sivakumar ◽  
Kishore S. Karamchand ◽  
Nallusamy Sivakumar ◽  
...  


1996 ◽  
Author(s):  
James W. McWinn ◽  
D.A. Crossley




Author(s):  
Yoshihiko SHIMIZU ◽  
Kengo OSADA ◽  
Shuji IWAMI


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