Extent and patterns of hybridization among the three species of Populus that constitute the riparian forest of southern Alberta, Canada

2004 ◽  
Vol 82 (2) ◽  
pp. 253-264 ◽  
Author(s):  
Kevin D Floate
Keyword(s):  
Leaf Morphology ◽  
Populus Deltoides ◽  
Riparian Forest ◽  
Elevational Gradient ◽  
Future Research ◽  
Hybrid Zones ◽  
Populus Balsamifera ◽  
Balsam Poplar ◽  
Southern Alberta ◽  
Unique Nature

Three species of Populus (Salicaceae) overlap and hybridize in southern Alberta, Canada. Variation in leaf morphology throughout the region identifies five genetically distinct zones. The drainage of the Oldman River contains a pure zone of balsam poplar (Populus balsamifera L.), a pure zone of plains cottonwood (Populus deltoides Marsh.), plus overlap and hybrid zones of balsam poplar – narrowleaf cottonwood (Populus angustifolia James) and balsam poplar – narrowleaf cottonwood – plains cottonwood. The drainage of the Red Deer River contains a pure zone of balsam poplar, a pure zone of plains cottonwood, plus an overlap and hybrid zone of balsam poplar – plains cottonwood. Zones on both drainages coincide with an elevational gradient. Overlap and hybrid zones extend at least 700 river km (the length obtained by measuring distances between sites of hybridization on a river and its tributaries) combined across the two drainages. Principal components analyses on leaf morphology identify a pattern of bidirectional intro gression between sect. Tacamahaca (balsam poplar, narrowleaf cottonwood) species. These analyses also identify a pattern of unidirectional introgression between Tacamahaca and sect. Aigeiros (plains cottonwood) species, with F1 hybrids backcrossing only with the Tacamahaca parent. This pattern of unidirectional introgression subsequently was assessed and supported with data from the drainages of Ashley Creek and the Ogden River, Utah, which contain hybrid and overlap zones between narrowleaf cottonwood (Tacamahaca) and Fremont cottonwood, Populus fremontii S. Watson (Aigeiros). Given its unique nature in terms of extent, health, and composition, and given the effect of plant hybrid zones on the ecology and evolution of their associated organisms, it is hoped that the current study will facilitate future research targeting conservation of this riparian forest in its full genetic complexity.Key words: Populus, hybridization, riparian, cottonwood, introgression.

The discrimination of cottonwood clones in a mature grove along the Oldman River in southern Alberta

1999 ◽  
Vol 77 (8) ◽  
pp. 1084-1094 ◽  
Author(s):  
Lori A Gom ◽  
Stewart B Rood
Keyword(s):  
Interspecific Hybrids ◽  
Clonal Propagation ◽  
Populus Deltoides ◽  
Leaf Shape ◽  
Populus Balsamifera ◽  
Balsam Poplar ◽  
Populus Angustifolia ◽  
Southern Alberta ◽  
Gall Mite ◽  
Oldman River

In southwestern Alberta, the prairie cottonwood (Populus deltoides Bartr.), balsam poplar (Populus balsamifera L.), narrowleaf cottonwood (Populus angustifolia James), and interspecific hybrids provide the foundation of the biologically rich riparian forests. In addition to seedling-based reproduction, these cottonwoods are capable of clonal propagation, the extent of which is poorly understood. To investigate clonality in mature cottonwoods, a method for clone recognition was investigated. Between 1995 and 1997, the morphology and phenology of each tree in a mature cottonwood grove along the Oldman River were characterized. In decreasing order of utility, the characteristics most effective in revealing clones were sex, leaf shape, floral (inflorescence) phenology, and leaf phenology: flushing, senescence, and abscission. Independent traits of poplar bud gall mite (Aceria parapopuli Keifer) susceptibility and trunk architecture were less useful in clone delineation but validated the clonal determinations. Based on the analysis, the grove's 391 trunks (>10 cm diameter) included 115 genotypes, 48 single-trunked individuals, and 67 multiple-trunked clones. The clones (genets) contained from 2 to 53 trunks (ramets). It was found that 88% of trunks belonged to clonal groups, a proportion that was higher than anticipated. The extensive capacity for clonal recruitment should thus be considered in analyses of cottonwood reproductive ecology and cottonwood conservation and restoration programs.Key words: asexual reproduction, clone delineation, cottonwoods, morphology, phenology, Populus.

Clonal reproduction of riparian cottonwoods in southern Alberta

1994 ◽  
Vol 72 (12) ◽  
pp. 1766-1774 ◽  
Author(s):  
Stewart B. Rood ◽  
Craig Hillman ◽  
Trevor Sanche ◽  
John M. Mahoney
Keyword(s):  
Populus Deltoides ◽  
Hybrid Poplar ◽  
Adventitious Shoots ◽  
Clonal Reproduction ◽  
Populus Balsamifera ◽  
Populus Angustifolia ◽  
Southern Alberta ◽  
A Site ◽  
Oldman River ◽  
Root Suckers

From 1990 to 1993, 690 small cottonwood saplings were excavated along four rivers in the Oldman River Basin to determine their method of origin. Overall, 52% began as seedlings while 48% originated through clonal mechanisms, of which 30% (of the total) were root suckers, i.e., adventitious shoots from preexisting roots, and 18% were shoot suckers, i.e., new shoots originating from buried shoots. The shoot suckers arose primarily through (i) flood training, i.e., new shoot emergence from young shoots that had been toppled and buried during flood events, and (ii) shoot regrowth following decapitation by ice scouring or animal browsing. Only two saplings originated through cladoptosis, propagation from excised shoot fragments. The proportion of seedlings versus clonally established shoots varied somewhat across years and sites. Within a site, saplings near the river's edge were more commonly seedlings, whereas saplings further from the river were more commonly root suckers. Three cottonwood species occurred in the forests studied and their reproductive strategies varied somewhat. Unlike the balsam poplar (Populus balsamifera), narrowleaf cottonwood (Populus angustifolia), and interspecific hybrids, the prairie cottonwood (Populus deltoides) did not propagate through root suckers; all species produced seedlings and shoot suckers. This study demonstrates that clonal reproduction has the potential to contribute to the regeneration of riparian cottonwood forests in southern Alberta. The contribution through clonal propagation complicates the forest population structure and should be considered in programs to conserve the remaining riparian cottonwood forests in southern Alberta and elsewhere in North America. Key words: Populus, cottonwoods, hybrid poplar, reproduction, clones, suckering, seedlings.

A lack of heterosis in natural poplar hybrids from southern Alberta

1993 ◽  
Vol 71 (1) ◽  
pp. 37-42 ◽  
Author(s):  
John S. Campbell ◽  
John M. Mahoney ◽  
Stewart B. Rood
Keyword(s):  
Shoot Growth ◽  
Populus Deltoides ◽  
Populus Balsamifera ◽  
Hybrid Swarm ◽  
Basal Diameter ◽  
Populus Angustifolia ◽  
Southern Alberta ◽  
Order Of Magnitude ◽  
Wet Weight ◽  
Shoot Growth Rate

Shoot cuttings were collected from 56 native poplars along 11 rivers and creeks in southwestern Alberta, a region where Populus angustifolia, Populus balsamifera (sspp. balsamifera and trichocarpa), and Populus deltoïdes form a disectional, trispecific hybrid swarm. Cuttings were rooted and established in an irrigated nursery plot. After 3 years, stem diameters and heights were measured from 381 trees and whole shoots were harvested from 74 trees to establish a regression equation relating basal diameter and shoot wet weight. Shoot wet weight varied by more than an order of magnitude across the clones, and P. angustifolia clones tended to grow more slowly than clones of the other two species. There was no significant correlation between shoot growth rate and the degree of hybridization, as determined by a prior multivariate analysis of leaf form that has been substantiated by chemotaxonomic data. Thus, the interspecific hybrids were not generally more vigorous than clones with leaf forms typical of the parental species P. deltoides or P. balsamifera. Conversely, in the same environment, artificial hybrids of P. deltoides from Illinois and P. balsamifera (ssp. trichocarpa) from Washington expressed heterosis. It is theorized that introgressive genetic exchange accompanying the natural interbreeding of these three poplar species in southern Alberta minimizes their genetic distance, preventing heterosis. Key words: heterosis, hybridization, poplars, Populus, biomass.

Fire induces clonal sprouting of riparian cottonwoods

2000 ◽  
Vol 77 (11) ◽  
pp. 1604-1616 ◽  
Author(s):  
Lori A Gom ◽  
Stewart B Rood
Keyword(s):  
Populus Deltoides ◽  
Seedling Recruitment ◽  
Adventitious Shoots ◽  
Fire Disturbance ◽  
Average Height ◽  
Populus Balsamifera ◽  
Black Cottonwood ◽  
Populus Angustifolia ◽  
Southern Alberta ◽  
Oldman River

The principal native trees in the semiarid regions of southern Alberta are riparian cottonwoods. These include narrowleaf cottonwood, Populus angustifolia James, balsam poplar, Populus balsamifera ssp. balsamifera L., black cottonwood, Populus balsamifera ssp.trichocarpa Torr. & Gray, and prairie cottonwood, Populus deltoides Bartr., and interspecific hybrids. These phreatophytic poplars occur on the moist floodplains along streams and require flood disturbance for seedling recruitment. The present study investigated the responses of cottonwoods to another physical disturbance, fire. Two fires occurred in April 1992, in adjacent groves along the Oldman River at Lethbridge, Alberta. The fires occurred prior to bud flushing and the cottonwoods responded by vigorous sprouting, particularly in the first summer. By September of 1992 about 75% of the burned trees had produced coppice sprouts, new shoots from the remnant stumps. Root suckers, adventitious shoots from the roots of the burned trees, were also common, averaging 1 sucker/3 m2 in the burned zone. Five years after the burns, the number of clonal sprouts was reduced by about half and those had reached an average height of 3 m. Because of the difficulties of species identification for juvenile cottonwoods, sprouts were designated as Populus section Aigeiros (P. deltoides) or section Tacamahaca (the other species). After 5 months, 90% of the sprouting trunks and 80% of the suckers belonged to section Tacamahaca. After 5 years, this ratio had increased to 97% of the sprouting trunks and 98% of the suckers. This indicates that Tacamahaca cottonwoods produced more numerous sprouts with better survival than P. deltoides. This pattern across Populus sections was also observed at seven other cottonwood burn sites in western North America, from northern British Columbia to southern Utah. The Aigeiros cottonwoods, P. deltoides and P. fremontii S. Wats., produced few clonal shoots following fire, whereas Tacamahaca trees sprouted profusely. This study demonstrates that fire disturbance can stimulate clonal regeneration of riparian cottonwoods, particularly of section Tacamahaca.

Knowledge assimilation by employees in learning organizations

2014 ◽  
Vol 21 (6) ◽  
pp. 350-368 ◽  
Author(s):  
Tali Marcus ◽  
Snunith Shoham
Keyword(s):  
Self Efficacy ◽  
Safety Information ◽  
Future Research ◽  
Subjective Perception ◽  
Content Type ◽  
Unique Nature ◽  
Knowledge Assimilation ◽  
The Subject ◽  
Powerful Explanation ◽  
Safety Procedures

Purpose – The purpose of this study is to examine the factors related to the employee as an individual, that affect the quality and level of the individual’s assimilation of knowledge (AOK) which is transmitted by way of organizational learning. Design/methodology/approach – All subjects (317) of this research were employed at different positions in day camps of a social organization. The study examined the subjects’ AOK relating to the organization’s security and safety procedures. The variables examined in this study include: the employee’s organizational commitment; the employee’s perception of the organization’s culture; the employee’s perception of the advantage inherent in the security and safety information; the employee’s self-efficacy; and the employee’s motivation to assimilate the new knowledge. Findings – The research variables explained a significant part (37 per cent) of the variance obtained with respect to assimilation and learning in the organization. The most powerful explanation for the variance in degree of implementation was the perception of the organization’s security and safety culture and the subject’s self-efficacy. Subjects’ perceived advantage from the knowledge did not make a significant contribution and motivation serves as a mediator but it does not mediate directly between the variables and AOK. Research limitations/implications – The research was conducted in a single organization. We recommend conducting similar studies in other organizations, including other types of organizations, to strengthen the conclusions which derive from our research. We also recommend that future research should use alternative methodologies (e.g. qualitative research and review of the results by experts) since other methodologies might reveal new facts that may have been uncovered in the use of the quantitative method applied in our research. Practical implications – We recommend that an organization which strives to be a learning organization, should pay attention, inter alia, to factors relating to the employees themselves, and in particular: increasing the employees’ self-efficacy, clarifying the benefits to the employee of the transmitted knowledge; and bringing the organization’s values and culture into clearer focus for the employees. Originality/value – The unique nature of our research model is twofold: first, the variables on which we have chosen to focus are different from other studies, and to our knowledge, the combination of these variables and the examination of these variables in relation to learning in the context of organizations have not been examined in other studies. Second, our model gauges the effects of an employee’s subjective perception with relation to his organization’s culture, his perceived advantage with regard to the subject-matter which he is learning and his self-assessed existing knowledge.

scholarly journals Smartphones and Learning: An Extension of M-Learning or a Distinct Area of Inquiry

2022 ◽  
Vol 12 (1) ◽  
pp. 50
Author(s):  
Kendall Hartley ◽  
Alberto Andújar
Keyword(s):  
Future Research ◽  
Unique Role ◽  
Distinct Area ◽  
Unique Nature ◽  
Author Keywords ◽  
Learning Research ◽  
Research In Education

The smartphone has become an integral part of the education landscape. While there has been significant smartphone research in education under the guise of m-learning, the unique role of the device suggests that m-learning may not be an appropriate characterization. The purpose of this paper is to review the use of m-learning as a primary descriptor for smartphone- and learning-related research. In support of this goal, the paper reviews the definitions associated with m-learning, smartphones, and related technologies from the perspective of educational research. In addition, a review of author keywords of research on smartphones in education is used to provide context to the classification of the research. Finally, three theoretically guided smartphone programs are presented as evidence of the unique nature of smartphone and learning research. This review concludes with recommendations for the characterization of future research.

scholarly journals Climate-driven local adaptation of ecophysiology and phenology in balsam poplar, Populus balsamifera L. (Salicaceae)

2011 ◽  
Vol 98 (1) ◽  
pp. 99-108 ◽  
Author(s):  
Stephen R. Keller ◽  
Raju Y. Soolanayakanahally ◽  
Robert D. Guy ◽  
Salim N. Silim ◽  
Matthew S. Olson ◽  
...  
Keyword(s):  
Local Adaptation ◽  
Populus Balsamifera ◽  
Balsam Poplar

Effects of balsam poplar (Populus balsamifera) tannins and low molecular weight phenolics on microbial activity in taiga floodplain soil: implications for changes in N cycling during succession

1996 ◽  
Vol 74 (1) ◽  
pp. 84-90 ◽  
Author(s):  
Joshua P. Schimel ◽  
Keith Van Cleve ◽  
Rex G. Cates ◽  
Thomas P. Clausen ◽  
Paul B. Reichardt
Keyword(s):  
Molecular Weight ◽  
Secondary Compounds ◽  
N Cycling ◽  
Low Molecular Weight ◽  
N Fixation ◽  
N Availability ◽  
Populus Balsamifera ◽  
Floodplain Soil ◽  
Balsam Poplar ◽  
River Floodplains

The transition from alder (Alnus tenuifolia) to balsam poplar (Populus balsamifera) is a critical turning point in primary succession on river floodplains in interior Alaska. Associated with the change in plant species are large changes in N cycling. N-fixation and nitrification decrease and the system becomes N-limited, with NH4+ dominating the inorganic N pool. Balsam poplar leaves contain large quantities of tannins and low molecular weight phenolic compounds. We evaluated the effect of these compounds on microbial respiration and N cycling in laboratory assays on soils from an alder-dominated site. Plant compounds were purified and applied to silica gel as an inert carrier. Both tannins and phenolics caused net N-immobilization over a 30-day assay. However, tannins inhibited respiration while phenolics stimulated it. There were no specific effects on nitrification. Thus, tannins acted as a general microbial inhibitor, while phenolics acted as a growth substrate. By inhibiting mineralization while stimulating immobilization, poplar secondary compounds may reduce soil N-availability during the transition betwen alder and poplar stages in succession. Keywords: respiration, mineralization, tannins, secondary chemicals, succession, plant–microbe interactions.

scholarly journals Physiological Demands of Extreme Obstacle Course Racing: A Case Study

2019 ◽  
Vol 16 (16) ◽  
pp. 2879
Author(s):  
Timothy Baghurst ◽  
Steven L. Prewitt ◽  
Tyler Tapps
Keyword(s):  
Heart Rate ◽  
The United States ◽  
Future Research ◽  
Improve Performance ◽  
Cognitive Demands ◽  
Unique Nature ◽  
Physiological Demands ◽  
Road Races ◽  
Training Opportunities

Obstacle course races are a popular source of recreation in the United States, providing additional challenges over traditional endurance events. Despite their popularity, very little is known about the physiological or cognitive demands of obstacle course races compared to traditional road races. The purpose of this study was to investigate the physiological effects of participation in an extreme obstacle course race. The participant was a 38-year-old Caucasian male, who completed an extreme obstacle course race over a 24-h period. Exercise intensity, steps taken, energy expenditure, and heart rate were recorded over the event’s duration using an Actigraph Link GT9X-BT accelerometer and a Polar heart rate monitor. Results reflected the unique nature of obstacle course racing when compared to traditional endurance events, with ups-and-downs recorded in each variable due to the encountering of obstacles. This case study provides a glimpse into the physiological demands of obstacle course racing, and suggests that the cognitive demands placed on competitors may differ to traditional endurance events, due to the challenges of obstacles interspersed throughout the event. With the popularity of obstacle course racing, and to enhance training opportunities, improve performance, and decrease the incidence of injuries, future research should further investigate the physiological and cognitive demands of obstacle course races of various distances and among diverse populations.

scholarly journals Foliar Penetration of Picloram and 2,4-D in Aspen and Balsam Poplar

Weed Science ◽  
1970 ◽  
Vol 18 (1) ◽  
pp. 57-63 ◽  
Author(s):  
M. P. Sharma ◽  
W. H. Vanden Born
Keyword(s):  
Relative Humidity ◽  
Populus Tremuloides ◽  
High Relative Humidity ◽  
Populus Balsamifera ◽  
Cuticular Waxes ◽  
Adaxial Surface ◽  
Balsam Poplar ◽  
Detached Leaves ◽  
Young Leaves ◽  
Dichlorophenoxy Acetic Acid

Added surfactant (Atlox 210) at 1% (v/v) and high relative humidity enhanced the penetration of both 4-amino-3,5,6-trichloropicolinic acid (picloram) and (2,4-dichlorophenoxy)acetic acid (2,4-D) into detached leaves of aspen poplar (Populus tremuloides Michx.). The influence of added surfactant was greater for picloram and the dimethylamine of 2,4-D than for the ethyl or butoxyethanol ester of 2,4-D. Penetration of picloram and the dimethylamine of 2,4-D occurred more readily from the abaxial than from adaxial surfaces of leaves. The ethyl ester of 2,4-D penetrated equally readily from both leaf surfaces. Penetration of picloram and the dimethylamine of 2,4-D from the adaxial surface of leaves occurred readily in young leaves in early June. There was an increase in penetration in early July followed by a decrease in August and September to a level equal to or less than that in June. Penetration from the abaxial surface of leaves was nearly equal in June and July, but there was a gradual decrease in August and September. An increase in temperature from 10 to 25.5 or to 40.5 C resulted in a sharp increase in penetration of both picloram and 2,4-D under both low and high relative humidity. Autoradiographic evidence showed that movement of picloram within the leaf also was much more extensive at the higher temperatures. Partial removal of cuticular waxes from the adaxial surface of leaves with chloroform resulted in up to four-fold increases in penetration of picloram and 2,4-D. Differences in penetration rate of picloram between leaves of aspen poplar and balsam poplar (Populus balsamifera L.) did not account for reported differences in susceptibility between these two species.

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