scholarly journals Patterns of bryophyte succession in a 160-year chronosequence in deciduous and coniferous forests of boreal Alaska

2017 ◽  
Vol 47 (8) ◽  
pp. 1021-1032 ◽  
Author(s):  
Mélanie Jean ◽  
Heather D. Alexander ◽  
Michelle C. Mack ◽  
Jill F. Johnstone
Keyword(s):  
Leaf Litter ◽  
Populus Tremuloides ◽  
Boreal Forests ◽  
Coniferous Forests ◽  
Stand Age ◽  
Organic Layer ◽  
Layer Depth ◽  
Litter Cover ◽  
Canopy Composition ◽  
Compositional Patterns

Bryophytes are dominant components of boreal forest understories and play a large role in regulating soil microclimate and nutrient cycling. Therefore, shifts in bryophyte communities have the potential to affect boreal forests’ ecosystem processes. We investigated how bryophyte communities varied in 83 forest stands in interior Alaska that ranged in age (since fire) from 8 to 163 years and had canopies dominated by deciduous broadleaf (Populus tremuloides Michx. or Betula neoalaskana Sarg.) or coniferous trees (Picea mariana Mill B.S.P.). In each stand, we measured bryophyte community composition, along with environmental variables (e.g., organic layer depth, leaf litter cover, moisture). Bryophyte communities were initially similar in deciduous vs. coniferous forests but diverged in older stands in association with changes in organic layer depth and leaf litter cover. Our data suggest two tipping points in bryophyte succession: one at the disappearance of early colonizing taxa 20 years after fire and another at 40 years after fire, which corresponds to canopy closure and differential leaf litter inputs in mature deciduous and coniferous canopies. Our results enhance understanding of the processes that shape compositional patterns and ecosystem services of bryophytes in relation to stand age, canopy composition, and changing disturbances such as fire that may trigger changes in canopy composition.

Wounding of aspen roots promotes suckering

2004 ◽  
Vol 82 (3) ◽  
pp. 310-315 ◽  
Author(s):  
Erin C Fraser ◽  
Victor J Lieffers ◽  
Simon M Landhäusser
Keyword(s):  
Populus Tremuloides ◽  
Growth Rates ◽  
Growing Season ◽  
Organic Layer ◽  
Trembling Aspen ◽  
Layer Depth ◽  
Injury Type ◽  
Organic Layers ◽  
Root Injury ◽  
Root Sucker

In early May, 1-m sections of trembling aspen (Populus tremuloides Michx.) roots in a forest cutblock were carefully exposed and examined for damage. Undamaged roots were subjected to one of three wounding treatments (scrape, sever, or uninjured control) and were then reburied to either the full normal organic layer depth or to one third of the normal depth. Following one growing season, the roots were reexposed and assessed for aspen sucker numbers and growth rates. Results indicate that injured roots produced suckers nearly twice as often as uninjured roots. Further, injured roots produced more suckers per root, and these suckers were taller and had greater leaf area. Roots buried under shallow organic layers also generated more suckers, regardless of injury type. The side of injury (distal or proximal) did not affect any of the measured variables. The present study suggests that moderate wounding of aspen roots increases initial sucker numbers and growth rates.Key words: trembling aspen, root sucker, root injury, regeneration.

Variation in postfire organic layer thickness in a black spruce forest complex in interior Alaska and its effects on soil temperature and moisture

2005 ◽  
Vol 35 (9) ◽  
pp. 2164-2177 ◽  
Author(s):  
Eric S Kasischke ◽  
Jill F Johnstone
Keyword(s):  
Soil Temperature ◽  
Fuel Consumption ◽  
Fire History ◽  
Black Spruce ◽  
Mineral Soil ◽  
Stand Age ◽  
Organic Layer ◽  
Layer Depth ◽  
Interior Alaska ◽  
Soil Temperature And Moisture

This study investigated the relationship between climate and landscape characteristics and surface fuel consumption as well as the effects of variations in postfire organic layer depth on soil temperature and moisture in a black spruce (Picea mariana (Mill.) BSP) forest complex in interior Alaska. Mineral soil moisture and temperature at the end of the growing season and organic layer depth were measured in three burns occurring in different years (1987, 1994, 1999) and in adjacent unburned stands. In unburned stands, average organic layer and humic layer depth increased with stand age. Mineral soil temperature and moisture varied as a function of the surface organic layer depth in unburned stands, indicating that as a stand matures, the moisture content of the deep duff layer is likely to increase as well. Fires reduced the depth of the surface organic layers by 5 to 24 cm. Within each burn we found that significant variations in levels of surface fuel consumption were related to several factors, including mineral soil texture, presence or absence of permafrost, and timing of the fires with respect to seasonal permafrost thaw. While seasonal weather patterns contribute to variations in fuel moisture and consumption during fires, interactions among the soil thermal regime, surface organic layer depth, and previous fire history are also important in controlling patterns of surface fuel consumption.

Diversity and abundance of bryophytes, lichens, and fungi in relation to woody substrate and successional stage in aspen mixedwood boreal forests

1998 ◽  
Vol 76 (4) ◽  
pp. 641-651 ◽  
Author(s):  
Susan Crites ◽  
Mark RT Dale
Keyword(s):  
Species Richness ◽  
Relative Abundance ◽  
Populus Tremuloides ◽  
Boreal Forests ◽  
Stand Age ◽  
Species Assemblages ◽  
Age Classes ◽  
Successional Stage ◽  
Woody Substrates ◽  
Mixedwood Stands

We examined the effects of woody substrate and stand age on diversity and relative abundance of bryophytes, lichens, and fungi in trembling aspen (Populus tremuloides Michx.) mixedwood boreal forests in Alberta. Point sampling was carried out on surfaces of downed woody material in young (23-26 years), mature (51-63 years), and old (122-146 years) aspen mixedwood stands. Downed woody material was categorized into one of seven decay stages. Diversity and relative abundance of bryophytes, lichens, and fungi were related to decay stage of the log and to stand age. Old aspen mixedwood stands had the highest nonvascular species richness and the greatest diversity of woody substrates in each of the decay stages. The seven decay stages shared many species. Species of bryophytes, lichens, and fungi on particular decay stages were different across the age-classes, indicating that time, as well as structural attributes, were important in determining species assemblages. These results suggest that both the presence of old aspen mixedwood stands and downed wood in different stages of decay are important to maintaining assemblages of bryophytes, lichens, and fungi.Key words: bryophytes, lichens, decay, aspen mixedwood, downed woody material.

Riparian canopy type, management history, and successional stage control fluxes of plant litter to streams

2011 ◽  
Vol 41 (7) ◽  
pp. 1394-1404 ◽  
Author(s):  
Trent M. Hoover ◽  
Xavier Pinto ◽  
John S. Richardson
Keyword(s):  
Leaf Litter ◽  
Forest Type ◽  
Riparian Forest ◽  
Plant Litter ◽  
Coniferous Forests ◽  
Stand Age ◽  
Riparian Management ◽  
Management History ◽  
Forest Stream ◽  
Small Streams

The food webs of forest stream ecosystems are based primarily on cross-boundary flows of terrestrial plant litter (PL). As such, changes in the composition of riparian forest canopies can alter flows of PL, affecting the ecosystem functioning of adjacent streams. We measured seasonal changes in PL fluxes to 20 small streams flowing through temperate rain forests in southwestern British Columbia to determine how riparian forest type and riparian management history influence resource availability in these systems. Differences in PL fluxes among the four riparian forest types studied were most pronounced in the summer, when PL fluxes from clearcuts < riparian reserve strips and coniferous forests, and PL fluxes from deciduous-dominated forests < riparian reserve strips. PL fluxes also varied among seasons (spring < summer < autumn). Fluxes were similar in riparian reserve strips and coniferous forests of similar age, indicating that reserve strips maintain this crucial ecosystem process. Clearcutting of riparian forests dramatically increased light availability while reducing leaf litter inputs; these effects, however, lasted only a few years. As riparian forest stand age increased, inputs shifted from broadleaf to coniferous inputs, indicating a possible long-term decrease in the lability of the leaf litter resources available to stream consumers.

scholarly journals Ranking Importance of Topographical Surface and Subsurface Parameters on Paludification in Northern Boreal Forests Using Very High Resolution Remotely Sensed Datasets

2020 ◽  
Vol 12 (2) ◽  
pp. 577 ◽  
Author(s):  
Ahmed Laamrani ◽  
Osvaldo Valeria
Keyword(s):  
High Resolution ◽  
Boreal Forests ◽  
Critical Role ◽  
Mineral Soil ◽  
Coniferous Forests ◽  
Slope Aspect ◽  
Limiting Factor ◽  
Organic Layer ◽  
Topographic Wetness Index ◽  
Variable Surface

The accumulation of organic material on top of the mineral soil over time (a process called paludification) is common in Northern Boreal coniferous forests. This natural process leads to a marked decrease in forest productivity overtime. Topography both at the surface of the forest floor (i.e., above ground) and the subsurface (i.e., top of mineral soil which is underground) is known to play a critical role in the paludification process. Until recently, the availability of more accurate topographic information regarding the surface and subsurface was a limiting factor for land management and modeling of spatial organic layer thickness (OLT) variability, a proxy for paludification. However so far, no research has assessed which of these two topographic variables has the greatest influence on paludification. This study aims to assess which topographic variable (surface or subsurface) better explains paludification, using high-resolution remote sensing technology (i.e., Light Detection and Ranging: LiDAR and Ground Penetrating Radar: GPR). To this end, field soil measurements were made in over 1614 sites distributed throughout the reference Valrennes Experimental site in Canadian northern coniferous forests. Then, a machine learning model (i.e., Random Forest, RF) was implemented to rank a set of selected predictor topographic variables (i.e., slope, aspect, mean curvature, plan curvature, profile curvature, and topographic wetness index) using the Mean Decrease Gini (MDG) index as an indicator of importance. Results showed that overall 83% of the overall variance was explained by the RF selected model, while the derived subsurface topography predictors had the lowest MDGs for predicting paludification. On the other hand, the surface slope predictor had the highest MDGs and better explained paludification. This finding would be particularly useful for implanting sustainable management strategies based on the surface variables of paludified northern boreal forests. This study has also highlighted the potential of LiDAR data to provide surface topographic spatial detail information for planning and optimizing forest management activities in paludified boreal forests. This is even of great importance when we know that LiDAR variables are easier to obtain compared to GPR derived variables (subsurface topographic variables).

Decomposition of broadleaf and needle litter in forests of British Columbia: influences of litter type, forest type, and litter mixtures

2000 ◽  
Vol 30 (11) ◽  
pp. 1742-1750 ◽  
Author(s):  
C E Prescott ◽  
L M Zabek ◽  
C L Staley ◽  
R Kabzems
Keyword(s):  
British Columbia ◽  
Populus Tremuloides ◽  
Picea Glauca ◽  
Boreal Forests ◽  
Forest Type ◽  
Douglas Fir ◽  
Coniferous Forests ◽  
Coastal Forests ◽  
Mixedwood Forests ◽  
Needle Litter

We measured rates of decomposition at three sites representing the major mixedwood forest types of British Columbia: (i) boreal forests of white spruce (Picea glauca (Moench) Voss) and trembling aspen (Populus tremuloides Michx.); (ii) coastal forests of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and red alder (Alnus rubra Bong.); and (iii) a wet interior forest of Douglas-fir, paper birch (Betula papyrifera Marsh.), and lodgepole pine (Pinus contorta Doug. ex Loud.). Mass loss of litter of each species (both pure and in combination with the other species) was measured for 2-5 years in forests of each species to determine (i) if broadleaf litter decomposed faster than needle litter, (ii) if litter decomposed faster in broadleaf or mixedwood forests than in coniferous forests, and (iii) if mixing with broadleaf hastened decomposition of needle litter. The broadleaf litters decomposed faster than needles during the first year but, thereafter, decomposed more slowly, so differences were small after 3 years. Litter tended to decompose faster in the broadleaf forests than in the coniferous forests. There was either no effect or a slight suppression of decomposition when litters were mixed; thus, there was no evidence that addition of broadleaf litter hastened decomposition of needle litter. The results clearly indicate that the mixing of needle litter with broadleaf litter is unlikely to hasten decomposition in mixedwood forests of British Columbia. The main influence of broadleaves was more rapid decomposition in broadleaf or mixedwood forest floors, which does not appear to be simply an effect of litter quality or litter mixing.

Influence of Stand Age And Structure on the Epiphytic Lichen Vegetation in the Middle-Boreal Forests of Finland

1992 ◽  
Vol 24 (2) ◽  
pp. 165-180
Author(s):  
M. Hyvärinen ◽  
P. Halonen ◽  
M. Kauppi
Keyword(s):  
Boreal Forests ◽  
Environmental Variables ◽  
Competitive Ability ◽  
Lichen Species ◽  
Tree Canopy ◽  
Stand Age ◽  
Ecological Strategy ◽  
Epiphytic Lichen ◽  
Vertical Location ◽  
Community Variation

Abstract The epiphytic lichen vegetation on the trunks of Pinus sylvestris and Picea abies was studied and analysed by canonical correspondence analysis in relation to a number of environmental variables. The distribution and abundance of epiphytic lichen species proved to be dependent on the age of the stand, showing divergent responses in relation to phorophyte species and environmental variables such as acidity of the bark and vertical location on the trunk. The importance of stand age in the pattern of community variation is concluded to be an outcome of interaction between changes in the structure of the tree canopy, microclimate and properties of the bark. The responses of single lichen species to changes in the environment seem to vary considerably, indicating differences in competitive ability and ecological strategy between the species.

Saproxylic insect assemblages in Canadian forests: diversity, ecology, and conservation

2008 ◽  
Vol 140 (4) ◽  
pp. 453-474 ◽  
Author(s):  
David W. Langor ◽  
H.E. James Hammond ◽  
John R. Spence ◽  
Joshua Jacobs ◽  
Tyler P. Cobb
Keyword(s):  
Forest Management ◽  
Boreal Forests ◽  
Dead Wood ◽  
Sustainable Forest Management ◽  
Forest Harvesting ◽  
Stand Age ◽  
Managed Forests ◽  
Saproxylic Insects ◽  
Associated Species ◽  
Experimental Burns

AbstractSaproxylic insect assemblages inhabiting dead wood in Canadian forests are highly diverse and variable but quite poorly understood. Adequate assessment of these assemblages poses significant challenges with respect to sampling, taxonomy, and analysis. Their assessment is nonetheless critical to attaining the broad goals of sustainable forest management because such species are disproportionately threatened elsewhere by the reductions in dead wood generally associated with commercial exploitation of northern forests. The composition of the saproxylic fauna is influenced by many factors, including tree species, degree of decay, stand age, and cause of tree death. Wildfire and forest harvesting have differential impacts on saproxylic insect assemblages and on their recovery in postdisturbance stands. Exploration of saproxylic insect responses to variable retention harvesting and experimental burns is contributing to the development of prescriptions for conserving saproxylic insects in boreal forests. Understanding of processes that determine diversity patterns and responses of saproxylic insects would benefit from increased attention to natural history. Such work should aim to provide a habitat-classification system for dead wood to better identify habitats (and associated species) at risk as a result of forest management. This tool could also be used to improve strategies to better maintain saproxylic organisms and their central nutrient-cycling functions in managed forests.

Effect of forest harvesting and slash piling on microbial biomass and respiration in Newfoundland boreal forests

2007 ◽  
Vol 87 (4) ◽  
pp. 455-458 ◽  
Author(s):  
Martin T Moroni ◽  
Paul Q Carter ◽  
Dean W Strickland ◽  
Franz Makeschin ◽  
Don-Roger Parkinson ◽  
...  
Keyword(s):  
Microbial Biomass ◽  
Key Words ◽  
Boreal Forests ◽  
Fungal Biomass ◽  
Forest Harvesting ◽  
Organic Layer ◽  
Total Microbial Biomass ◽  
Organic Layers ◽  
Respiration Rates ◽  
Fumigation Extraction

Clearcutting Newfoundland boreal forests significantly reduced organic layer fungal and total microbial biomass in clearcut areas with and without slash cover, compared with forested plots. However, aerobically incubated respiration rates were highest in organic layers from clearcut areas under slash, intermediate under forests, and lowest from clearcut areas without slash. Key words: Carbon, ergosterol, fumigation–extraction, fungal biomass, harvest slash, nitrogen

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