Interactive effects of tree and herb cover on survivorship, physiology, and microclimate of conifer seedlings at the alpine tree-line ecotone

2005 ◽  
Vol 35 (3) ◽  
pp. 567-574 ◽  
Author(s):  
Eliza L Maher ◽  
Matthew J Germino ◽  
Niles J Hasselquist
Keyword(s):  
Forest Succession ◽  
Interactive Effects ◽  
Tree Cover ◽  
First Year ◽  
Abies Lasiocarpa ◽  
Tree Line ◽  
Conifer Seedlings ◽  
Factors Affecting ◽  
Nighttime Temperatures ◽  
Snowy Range

Factors affecting the establishment of trees in subalpine meadows are important to population dynamics of trees in the alpine tree-line ecotone (ATE). Interactive effects of tree and herb cover on conifer seedlings were investigated in the ATE of the Snowy Range, Wyoming, USA. Microclimate, physiology, and survivorship of first-year conifer seedlings of Pinus albicaulis Engelm., Picea engelmannii Parry, and Abies lasiocarpa Hook. were measured in response to manipulations of surrounding herb and tree cover, as well as water availability. Tree and herb cover had nearly additive effects on survivorship and photosynthesis of conifer seedlings, except under alleviated water stress. In P. albicaulis, photosynthesis was greater near compared with away from trees and herbs, and photosynthetic efficiency (Fv/Fm) increased under herb cover. Tree cover led to greater nighttime temperatures, soil water contents, and, like herb cover, shade from solar radiation for seedlings. We did not detect any negative responses of conifer seedlings to surrounding vegetation. Furthermore, the effect of surrounding vegetation on conifer establishment appeared dependent on the type of surrounding vegetation, the species of conifer, and microsite stress level. These factors may lead to variation in the way conifer seedlings interact with surrounding vegetation and could explain changes in the relative abundances of tree species during forest succession in ATEs.

Landscape- and age-based factors affecting fungal colonization of conifer seedling roots at the alpine tree line

2006 ◽  
Vol 36 (4) ◽  
pp. 901-909 ◽  
Author(s):  
Matthew J Germino ◽  
Niles J Hasselquist ◽  
Terence McGonigle ◽  
William K Smith ◽  
Peter P Sheridan
Keyword(s):  
Trichoderma Viride ◽  
Fungal Colonization ◽  
Transplant Experiment ◽  
Abies Lasiocarpa ◽  
Tree Line ◽  
Factors Affecting ◽  
Experimental Variation ◽  
Demographic Bottleneck ◽  
Seedling Roots ◽  
Root Surfaces

Survival of seedlings is a demographic bottleneck for tree populations in alpine tree-line ecotones (ATE) and may play a pivotal role in determining the elevation of timberlines and tree lines. We evaluated (1) fungal colonization of root surfaces of natural seedlings of Picea engelmannii Parry ex Engelm. and Abies lasiocarpa (Hook.) Nutt. in an ATE, (2) the relative importance of soil versus microclimate variation to differences in colonization in the ATE, determined using a reciprocal soil transplant experiment, and (3) ecophysiological responses of seedlings to natural and experimental variation in colonization. Many root systems lacked ectomycorrhizae but had extensive quantities of white mycelium attached to root surfaces. This mycelium was composed of a group of species referred to as the "alpine white complex" (AWC), and included Mortierella parvispora Linneman, Trichoderma viride Pers.:Fr., and a basidiomycete. Nearly all seedlings that survived beyond the first year of growth were colonized by AWC, whereas <10% of emergent seedlings had AWC where they commonly do not survive, in microsites distant from trees. No relationships of AWC and microclimate, photosynthesis, or water relations of seedlings were detected, and low colonization levels likely resulted from scarcity of AWC in ATE soils. Determining if and how AWC or emergent conifer seedlings benefit from their symbiosis in ATEs will require further inquiry.

Seventeen Years of Forest Succession Following the Waterfalls Canyon Fire in Grand Teton National Park, Wyoming

1998 ◽  
Vol 8 (1) ◽  
pp. 45 ◽  
Author(s):  
KM Doyle ◽  
DH Knight ◽  
DL Taylor ◽  
WJ Barmore ◽  
JM Benedict
Keyword(s):  
Tree Species ◽  
National Park ◽  
Forest Succession ◽  
Picea Engelmannii ◽  
First Year ◽  
Abies Lasiocarpa ◽  
Severe Burn ◽  
Grand Teton National Park ◽  
Primary Mechanism ◽  
Understory Plant

Plant species composition has been sampled periodically since the 1974 Waterfalls Canyon Fire in Grand Teton National Park, Wyoming. Prior to the fire, the forests were dominated by mature Abies lasiocarpa, Picea engelmannii and Finns contorta. All three tree species have reestablished. After 17 years, P. engelmannii sapling density was 1.2-11.2 times greater than the other tree species. A. lasiocarpa and P. contorta saplings were second in density to P. engelmannii in the moderate and severely burned stands, respectively. The understory shrub and herbaceous species that were most abundant during the first 17 years were common the first year after the fire and were also found in the unburned mature forest. Species present in the unburned forest contributed 91-100% of the understory cover in the moderate burn, and 55-74% in the severe burn. Species richness was greatest in the severely burned stand and has increased during the 17 years of succession. While sprouting is the primary mechanism for understory plant establishment in the moderate burn, most species appear to have grown from seeds in the severe burn.

scholarly journals Interactive effects between travel behaviour and COVID-19: a questionnaire study

2021 ◽  
Author(s):  
Jinbao Zhang ◽  
Jaeyoung Lee
Keyword(s):  
Early Stage ◽  
Travel Behaviour ◽  
Interactive Effects ◽  
Factors Affecting ◽  
Individual Level ◽  
Passenger Volume ◽  
Spatial Autoregressive ◽  
Railway Passenger ◽  
The Individual ◽  
And Control

Abstract This study has two main objectives: (i) to analyse the effect of travel characteristics on the spreading of disease, and (ii) to determine the effect of COVID-19 on travel behaviour at the individual level. First, the study analyses the effect of passenger volume and the proportions of different modes of travel on the spread of COVID-19 in the early stage. The developed spatial autoregressive model shows that total passenger volume and proportions of air and railway passenger volumes are positively associated with the cumulative confirmed cases. Second, a questionnaire is analysed to determine changes in travel behaviour after COVID-19. The results indicate that the number of total trips considerably decreased. Public transport usage decreased by 20.5%, while private car usage increased by 6.4%. Then the factors affecting the changes in travel behaviour are analysed by logit models. The findings reveal significant factors, including gender, occupation and travel restriction. It is expected that the findings from this study would be helpful for management and control of traffic during a pandemic.

scholarly journals Carbon and nutrient physiology in shrubs at the upper limits: a multi-species study

2020 ◽  
Author(s):  
Xue Wang ◽  
Fei-Hai Yu ◽  
Yong Jiang ◽  
Mai-He Li
Keyword(s):  
Fine Roots ◽  
Soluble Sugar ◽  
Soluble Sugars ◽  
Growing Season ◽  
Interactive Effects ◽  
Tree Line ◽  
Shrub Species ◽  
Nutrient Physiology ◽  
Upper Limits ◽  
Species Study

Abstract Aims Carbon and nutrient physiology of trees at their upper limits have been extensively studied, but those of shrubs at their upper limits have received much less attention. The aim of this study is to examine the general patterns of non-structural carbohydrates (NSCs), nitrogen (N) and phosphorous (P) in shrubs at the upper limits, and to assess whether such patterns are similar to those in trees at the upper limits. Methods Across Eurasia, we measured the concentrations of soluble sugars, starch, total NSCs, N and P in leaves, branches and fine roots (&lt; 0.5 cm in diameter) of five shrub species growing at both the upper limits and lower elevations in both summer (peak growing season) and winter (dormancy season). Important Findings Neither elevation nor season had significant effects on tissue N and P concentrations, except for lower P concentrations in fine roots in winter than in summer. Total NSCs and soluble sugars in branches were significantly higher in winter than in summer. There were significant interactive effects between elevation and season for total NSCs, starch, soluble sugars and the ratio of soluble sugar to starch in fine roots, showing lower soluble sugars and starch in fine roots at the upper limits than at the lower elevations in winter but not in summer. These results suggest that the carbon physiology of roots in winter may play an important role in determining the upward distribution of shrubs, like that in the alpine tree-line trees.

Variation in vegetation cover and seedling performance of tree species in a forest-savanna ecotone

2019 ◽  
Vol 35 (2) ◽  
pp. 74-82 ◽  
Author(s):  
Hamza Issifu ◽  
George K. D. Ametsitsi ◽  
Lana J. de Vries ◽  
Gloria Djaney Djagbletey ◽  
Stephen Adu-Bredu ◽  
...  
Keyword(s):  
Vegetation Cover ◽  
Seedling Recruitment ◽  
Seedling Survival ◽  
Tree Cover ◽  
First Year ◽  
Transplant Experiment ◽  
Tree Seedling ◽  
Savanna Woodland ◽  
Specific Effects ◽  
Species Specific

AbstractDifferential tree seedling recruitment across forest-savanna ecotones is poorly understood, but hypothesized to be influenced by vegetation cover and associated factors. In a 3-y-long field transplant experiment in the forest-savanna ecotone of Ghana, we assessed performance and root allocation of 864 seedlings for two forest (Khaya ivorensis and Terminalia superba) and two savanna (Khaya senegalensis and Terminalia macroptera) species in savanna woodland, closed-woodland and forest. Herbaceous vegetation biomass was significantly higher in savanna woodland (1.0 ± 0.4 kg m−2 vs 0.2 ± 0.1 kg m−2 in forest) and hence expected fire intensities, while some soil properties were improved in forest. Regardless, seedling survival declined significantly in the first-year dry-season for all species with huge declines for the forest species (50% vs 6% for Khaya and 16% vs 2% for Terminalia) by year 2. After 3 y, only savanna species survived in savanna woodland. However, best performance for savanna Khaya was in forest, but in savanna woodland for savanna Terminalia which also had the highest biomass fraction (0.8 ± 0.1 g g−1 vs 0.6 ± 0.1 g g−1 and 0.4 ± 0.1 g g−1) and starch concentration (27% ± 10% vs 15% ± 7% and 10% ± 4%) in roots relative to savanna and forest Khaya respectively. Our results demonstrate that tree cover variation has species-specific effects on tree seedling recruitment which is related to root storage functions.

Age- and sex-related morphological and physiological differences influence escape capacity in House Sparrows (Passer domesticus)

2010 ◽  
Vol 88 (10) ◽  
pp. 1021-1031 ◽  
Author(s):  
L. De Neve ◽  
J. D. Ibañez-Alamo ◽  
M. Soler
Keyword(s):  
Escape Response ◽  
Passer Domesticus ◽  
First Year ◽  
Cell Mediated Immunity ◽  
Animal Performance ◽  
House Sparrows ◽  
Factors Affecting ◽  
Age Related ◽  
Animal Populations ◽  
Age And Sex

Sexual dimorphism and age-related differences are sources that contribute to morphologic and physiologic variation within animal populations. Measurement of animal performance may indicate whether this variation is functionally relevant. Our study aimed to experimentally test this statement in a captive population of House Sparrows ( Passer domesticus (L., 1758)) by examining age- and sex-related differences in escape response and its relationship to several morphological (tarsus, wing, tail lengths, and body mass) and physiological traits (cell-mediated immunity, natural antibodies, complement activity, hematocrit, and stress response). Escape response from a predator is considered a good variable to measure animal performance, because natural selection clearly favours individuals that avoid predators successfully. Our experimental design also aimed to standardize possible confounding factors affecting escape behaviour under natural conditions. We exposed sparrows to short episodes of high predation risk by simulating the attack of a predator and assumed that the capture order of individuals was related to their escape capacity. The optimal strategy was the immediate escape response for all individuals. We found that first-year males were the best escapers. In support of the hypothesis, juvenile males gathered a better optimum of several morphological and physiological characters that related to capture order.

Factors affecting the study pace of first-year law students: in search of study counselling tools

2011 ◽  
Vol 36 (8) ◽  
pp. 911-922 ◽  
Author(s):  
Anne Haarala-Muhonen ◽  
Mirja Ruohoniemi ◽  
Sari Lindblom-Ylänne
Keyword(s):  
Law Students ◽  
First Year ◽  
Factors Affecting
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