scholarly journals Identifying Conifer Tree vs. Deciduous Shrub and Tree Regeneration Trajectories in a Space-for-Time Boreal Peatland Fire Chronosequence Using Multispectral Lidar

Atmosphere ◽  
2022 ◽  
Vol 13 (1) ◽  
pp. 112
Author(s):  
Humaira Enayetullah ◽  
Laura Chasmer ◽  
Christopher Hopkinson ◽  
Dan Thompson ◽  
Danielle Cobbaert
Keyword(s):  
Environmental Conditions ◽  
Tree Regeneration ◽  
Boreal Peatlands ◽  
Composition And Structure ◽  
Conifer Tree ◽  
Disturbance Vegetation ◽  
Northern Peatlands ◽  
Structural Metrics ◽  
Conifer Trees ◽  
Deciduous Shrub

Wildland fires and anthropogenic disturbances can cause changes in vegetation species composition and structure in boreal peatlands. These could potentially alter regeneration trajectories following severe fire or through cumulative impacts of climate-mediated drying, fire, and/or anthropogenic disturbance. We used lidar-derived point cloud metrics, and site-specific locational attributes to assess trajectories of post-disturbance vegetation regeneration in boreal peatlands south of Fort McMurray, Alberta, Canada using a space-for-time-chronosequence. The objectives were to (a) develop methods to identify conifer trees vs. deciduous shrubs and trees using multi-spectral lidar data, (b) quantify the proportional coverage of shrubs and trees to determine environmental conditions driving shrub regeneration, and (c) determine the spatial variations in shrub and tree heights as an indicator of cumulative growth since the fire. The results show that the use of lidar-derived structural metrics predicted areas of deciduous shrub establishment (92% accuracy) and classification of deciduous and conifer trees (71% accuracy). Burned bogs and fens were more prone to shrub regeneration up to and including 38 years after the fire. The transition from deciduous to conifer trees occurred approximately 30 years post-fire. These results improve the understanding of environmental conditions that are sensitive to disturbance and impacts of disturbance on northern peatlands within a changing climate.

scholarly journals Carbon dynamics in boreal peatlands of the Yenisey region, western Siberia

2015 ◽  
Vol 12 (23) ◽  
pp. 7057-7070 ◽  
Author(s):  
E. D. Schulze ◽  
E. Lapshina ◽  
I. Filippov ◽  
I. Kuhlmann ◽  
D. Mollicone
Keyword(s):  
Organic Carbon ◽  
Vegetation History ◽  
Accumulation Rate ◽  
West Siberian Plain ◽  
High Accumulation ◽  
Boreal Peatlands ◽  
Constant Rate ◽  
Northern Peatlands ◽  
River Valleys ◽  
Local Hydrology

Abstract. Here we investigate the vegetation history and peat accumulation at the eastern boarder of the West Siberian Plain, near the Yenisey River, south of permafrost. In this region, peat started to accumulate 15 000 years ago as gyttja of shallow lakes in ancient river valleys. This peat is older than previously reported, mainly due to separating particulate organic carbon (POC) from dissolved organic carbon (DOC), which was 1900–6500 years younger than POC. The probability of finding peat layers older than 12 000 years is about 2 %. Peat accumulated as fen peat at a constant rate of 0.2 mm yr−1 and 0.01 kg C m−2 yr−1. The accumulation was higher in ancient river valley environments. Over the last 2000 years these bogs changed into Sphagnum mires which have accumulated up to about 0.1 kg C m−2 yr−1 until present. The long-lasting fen stage, which makes the Yenisey bogs distinct from the western Siberian bogs, is discussed as a consequence of the local hydrology. The high accumulation rate of peat in unfrozen mires is taken as an indication that thawing of permafrost peat may also change northern peatlands into long-lasting carbon sinks.

scholarly journals Effect of gap size on composition and structure of regeneration 19 years after harvest in a southeastern bottomland forest, USA

2020 ◽  
Author(s):  
W. Henry McNab ◽  
John C. Kilgo ◽  
John I. Blake ◽  
Stanley J. Zarnoch
Keyword(s):  
Tree Regeneration ◽  
Stem Density ◽  
Pioneer Species ◽  
Gap Size ◽  
Species Dominance ◽  
Advance Regeneration ◽  
Tolerant Species ◽  
Composition And Structure ◽  
Bottomland Forest ◽  
Species Groups

Following timber harvests in bottomland mixed-oak (Quercus) stands, desirable oak advance regeneration can be overgrown by shade intolerant pioneer species. We investigated the effects of group selection opening size on composition of tree regeneration 19 years post-harvest in an oak dominated bottomland forest and compared our results with earlier findings to evaluate development trends. In response to six opening sizes (7 - 40 m radii) we evaluated regeneration density and dominance of four tree species groups: conifers, hard mast, shade intolerant and shade tolerant hardwoods. Our objective was to determine the optimum gap size for regenerating oaks and test the delayed oak dominance hypothesis, where oaks slowly gain dominance as pioneer species undergo self-thinning. Opening size influenced conifer regeneration but minimally affected hardwoods. Hard mast species density was less than either intolerant or tolerant species regardless of opening size. Future stem density trends suggest increasing intolerant species and constant mast and tolerant species. Modeled future height trends suggest increasing mast species dominance over intolerant pioneers after 30 years. Our results suggest that gap-based silviculture can be used to regenerate bottomland hardwood stands with desirable species including oaks; larger gaps favor conifers but there was no optimum size to enhance oak regeneration.

scholarly journals Isometric scaling to model water transport in conifer tree rings across time and environments

2020 ◽  
Author(s):  
Irina V Sviderskaya ◽  
Eugene A Vaganov ◽  
Marina V Fonti ◽  
Patrick Fonti
Keyword(s):  
Tree Rings ◽  
Environmental Conditions ◽  
Hydraulic Properties ◽  
Anatomical Variations ◽  
Plant Responses ◽  
Cross Sectional ◽  
Substantial Impact ◽  
Xylem Structure ◽  
Bordered Pits ◽  
Conifer Tree

Abstract Xylem hydraulic properties determine the ability of plants to efficiently and safely provide water to their leaves. These properties are key to understanding plant responses to environmental conditions and to evaluating their fate under a rapidly changing climate. However, their assessment is hindered by the challenges of quantifying basic hydraulic components such as bordered pits and tracheids. Here we use isometric scaling between tracheids and pits morphology to merge partial hydraulic models of tracheid’s component to upscale properties at the tree-ring level in conifers trees. Our new model output is first cross-validated with literature and then applied to cell anatomical measurements from Larix sibirica tree-rings formed under harsh conditions in southern Siberia to quantify the intra- and inter-annual variability in hydraulic properties. The model provides a means of assessing how different-sized tracheid’s components contribute to the hydraulic properties of the ring. Up-scaled results indicate that natural inter- and intra-ring anatomical variations have a substantial impact on the tree’s hydraulic properties. Our model facilitates the assessment of important xylem functional attributes because it only requires the more accessible measures of cross-sectional tracheid size. This approach, if applied to dated tree-rings, provides a novel way to investigate xylem structure-function relations across time and environmental conditions.

Modifications des communautés d'oiseaux de la sapinière suite au ravage d'une épidémie d'insectes

1995 ◽  
Vol 71 (2) ◽  
pp. 201-210
Author(s):  
J. L. DesGranges ◽  
G. Rondeau
Keyword(s):  
Choristoneura Fumiferana ◽  
Bird Species ◽  
Spruce Budworm ◽  
Forest Birds ◽  
Balsam Fir ◽  
White Birch ◽  
Predator Prey ◽  
Composition And Structure ◽  
Deciduous Shrub ◽  
Birch Forests

This study addresses the relationships between changes in the structure of bird communities and changes in the composition and structure of forest vegetation resulting from an insect infestation. The study compares two balsam fir-white birch forests located in similar physiographic settings. One of these was protected against spruce budworm infestation through insecticide spraying over a ten-year period. Following the infestation, the unprotected, defoliated forest underwent significant changes in structure, particularly the mortality of the coniferous tree strata and the consecutive expansion of the deciduous shrub strata. Yet, despite the infestation, the defoliated forest had just as many bird species and individual birds as the healthy stand protected through the use of insecticides. In addition, half of the avian species occurred with the same frequency in both types of forest. Aerial feeders (flycatchers) and those found in the underbrush (including four species of Turdinae) best withstood this type of infestation, whereas all species that fed chiefly at the tops of conifers decreased in number. This decrease in population could be the result of changes in stand physiognomy (for species such as Boreal Chickadee, Pine Grosbeak and Blackpoll Warbler) or predator-prey relationships affecting birds that feed mostly on spruce budworm larvae (Yellow-rumped, Bay-breasted and Tennessee Warblers). As the defoliated forest became mixed with hardwood stands, some birds increased in number (Black-throated Green Warbler and Solitary Vireo). However, two other species, Winter Wren and White-throated Sparrow, both ground species, were more common in the defoliated stand, probably because of gaps in the forest and the accumulation of dead wood on the ground, where the infestation left openings in the previously dense stands of mature balsam fir. Key words: forest birds, balsam fir, Choristoneura fumiferana, insecticides

The understorey palm Licuala (Arecaceae) suppresses tree regeneration in a lowland forest in Asia

2005 ◽  
Vol 21 (6) ◽  
pp. 703-706 ◽  
Author(s):  
James V. LaFrankie ◽  
L. G. Saw
Keyword(s):  
Environmental Conditions ◽  
Forest Floor ◽  
Seedling Recruitment ◽  
Spatial Association ◽  
Humid Tropics ◽  
Tree Regeneration ◽  
Low Density ◽  
Lowland Forest ◽  
Young Tree ◽  
Saw Palmetto

The establishment and growth of a young tree requires a microsite that falls within a range of specific environmental conditions. Microsites will to some degree be modified by such neighbouring plants as are already established, a circumstance that will in turn lead to either a positive or negative spatial association among the individuals. Such patterns of spatial interactions are amenable to statistical inference. Positive associations may result when one species ameliorates overall hostile conditions, such as the shade and moisture provided the seedlings of long-leaf pine by the canopy of the saw palmetto (Allen 1956). Indeed, positive associations appear widespread in arid and cold habitats (reviewed in Tirado & Pugnaire 2003). However, on the forest floor of the humid tropics, negative associations are presumably more likely (Montgomery 2004). Harms et al. (2004) recently found a correlation between high density of small palms and a low density of tree saplings across four Neotropical sites, while Wang & Augspurger (2004) demonstrated that dwarf palms and cyclanths reduce seedling recruitment on the forest floor in Costa Rica.

scholarly journals Variation in Tracheid Dimensions of Conifer Xylem Reveals Evidence of Adaptation to Environmental Conditions

2021 ◽  
Author(s):  
Jingming Zheng ◽  
Yajin Li ◽  
Hugh Morris ◽  
Filip Vandelook ◽  
Steven Jansen
Keyword(s):  
Wall Thickness ◽  
Environmental Conditions ◽  
Least Square ◽  
Soil Conditions ◽  
Conifer Species ◽  
Large Variability ◽  
Xylem Structure ◽  
Significant Difference ◽  
Conifer Tree ◽  
Independent Contrast

Abstract Background: Globally distributed extant conifer species must adapt to various environmental conditions, which would be reflected in their xylem structure, especially in the tracheid characteristics of earlywood and latewood. A comparative study of conifer species might shed light on how xylem structure responds to environmental conditions. With an anatomical trait dataset of 79 conifer tree species growing throughout China, an interspecific study within a phylogenetic context was conducted to quantify variance of tracheid dimensions and their response to climatic and soil conditions. Results: There was a significant difference in tracheid diameter between early- and latewood while no significant difference was detected in tracheid wall thickness through a phylogenetically paired t-test. Most of the tracheid dimensional traits were positively related to each other based on phylogenetic independent contrast (PIC) analyses, and tracheid structure could be accounted for by the first and second PCA axes. Through a phylogenetic principle component analysis (pPCA), Pinaceae species were found to be strongly divergent in their tracheid structure in contrast to a conservative tracheid structure in species of Cupressaceae, Taxaceae and Podocarpaceae. Meanwhile, tracheid wall thickness decreased from high to low latitudes in both earlywood and latewood, with tracheid diameter decreasing for latewood only. According to the most parsimonious phylogenetic general least square models (PGLS), environment and phylogeny together could explain about 21%~56% of tracheid structure variance, suggesting both genetics and the environment contribute to tracheid characteristics. Conclusions: The large variability of tracheid traits observed along an environmental gradient across China suggests that xylem structure was strongly constrained by the environmental conditions in temperate monsoonal climates and thus could be regarded as an ecological strategy for adapting to environmental stresses, especially freezing and drought. Our results provide insights into the effects of climate and soil on the xylem structure of conifer species thus furthering our understanding of the trees’ response to global change and guiding forest management.

Crystal Structure Analysis of Cu-Zr Alloys by Convergent Beam Diffraction

1981 ◽  
Vol 39 ◽  
pp. 354-355
Author(s):  
A. F. Marshall ◽  
J. W. Steeds ◽  
D. Bouchet ◽  
S. L. Shinde ◽  
R. G. Walmsley
Keyword(s):  
Crystal Structure ◽  
Point Group ◽  
Intermetallic Phase ◽  
Three Dimensional ◽  
Crystal Structure Analysis ◽  
Ion Milling ◽  
Composition And Structure ◽  
Unit Cells ◽  
Sputter Deposited ◽  
Convergent Beam

Convergent beam electron diffraction is a powerful technique for determining the crystal structure of a material in TEM. In this paper we have applied it to the study of the intermetallic phases in the Cu-rich end of the Cu-Zr system. These phases are highly ordered. Their composition and structure has been previously studied by microprobe and x-ray diffraction with sometimes conflicting results.The crystalline phases were obtained by annealing amorphous sputter-deposited Cu-Zr. Specimens were thinned for TEM by ion milling and observed in a Philips EM 400. Due to the large unit cells involved, a small convergence angle of diffraction was used; however, the three-dimensional lattice and symmetry information of convergent beam microdiffraction patterns is still present. The results are as follows:1) 21 at% Zr in Cu: annealed at 500°C for 5 hours. An intermetallic phase, Cu3.6Zr (21.7% Zr), space group P6/m has been proposed near this composition (2). The major phase of our annealed material was hexagonal with a point group determined as 6/m.

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