Influence of precommercial thinning on understory vegetation of young-growth Sitka spruce forests in southeastern Alaska

2010 ◽  
Vol 40 (4) ◽  
pp. 619-628 ◽  
Author(s):  
Elizabeth C. Cole ◽  
Thomas A. Hanley ◽  
Michael Newton
Keyword(s):  
Food Resource ◽  
Odocoileus Hemionus ◽  
Tsuga Heterophylla ◽  
Picea Sitchensis ◽  
Vegetative Cover ◽  
Precommercial Thinning ◽  
Growing Seasons ◽  
Specific Effects ◽  
Odocoileus Hemionus Sitkensis ◽  
Species Specific

The effects of precommercial thinning on the understory vegetative cover of 16- to 18-year-old spruce–hemlock ( Picea sitchensis (Bong.) Carrière – Tsuga heterophylla (Raf.) Sarg.) stands were studied in seven replicate areas over seven growing seasons postthinning. Vegetative cover was analyzed at the class level, but species-specific effects were examined in relation to their value as food for Sitka black-tailed deer ( Odocoileus hemionus sitkensis Cowan). When compared with unthinned controls, thinned stands (3.6–6.3 m spacing) had significantly greater understory cover. However, all thinned spacings led to similar understory cover. Conifer cover recovered to about two-thirds of its prethinning level within seven growing seasons posttreatment. Understory nonconiferous cover increased during the first 2–4 years postthinning but began to decline with increasing conifer cover during the next 3 years, nearly reaching pretreatment levels by year 7. In unthinned understories, vegetative cover had declined and was significantly lower than that beneath thinned stands. Summer food resource values for deer were increased by thinning. Winter food resource values were increased by thinning for snow-free conditions but were unaffected for conditions when herb-layer forbs were buried by snow.

Density-dependent and species-specific effects on self-organization modulate the resistance of mussel bed ecosystems to hydrodynamic stress

2021 ◽  
Author(s):  
Gerardo I. Zardi ◽  
Katy Rebecca Nicastro ◽  
Christopher D. McQuaid ◽  
Monique de Jager ◽  
Johan van de Koppel ◽  
...  
Keyword(s):  
Self Organization ◽  
Mussel Bed ◽  
Hydrodynamic Stress ◽  
Density Dependent ◽  
Specific Effects ◽  
Species Specific

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.

Growth ofPseudotsuga menziesiiandTsuga heterophyllaseedlings along a light gradient: resource allocation and morphological acclimation

1997 ◽  
Vol 75 (9) ◽  
pp. 1424-1435 ◽  
Author(s):  
D. Mailly ◽  
J. P. Kimmins
Keyword(s):  
Leaf Morphology ◽  
Biomass Accumulation ◽  
Tsuga Heterophylla ◽  
Douglas Fir ◽  
Western Hemlock ◽  
Low Light ◽  
Growing Seasons ◽  
Light Levels ◽  
Light Gradient ◽  
Relative Light Intensity

Silvicultural alternatives that differ in the degree of overstory removal may create shady environments that will be problematic for the regeneration of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco). Gradients of light in the field were used to compare mortality, growth, and leaf morphological acclimation of two conifer species of contrasting shade tolerances: Douglas-fir and western hemlock (Tsuga heterophylla (Raf.) Sarg.). Results after two growing seasons indicated that Douglas-fir mortality occurred mainly at relative light intensity (RLI) below 20%, while western hemlock mortality was evenly distributed along the light gradient. Height, diameter, and biomass of the planted seedlings increased with increasing light for both species but at different rates, and maximum biomass accumulation always occurred in the open. Douglas-fir allocated more resources to stem biomass than western hemlock, which accumulated more foliage biomass. Increases in specific leaf area for Douglas-fir seedlings occurred at RLI ≤ 0.4 and red/far red (R/FR) ratio ≤ 0.6, which appear to be the minimal optimum light levels for growth. Conversely, western hemlock seedlings adjusted their leaf morphology in a more regular pattern, and changes were less pronounced at low light levels. These results, along with early mortality results for Douglas-fir, suggest that the most successful way to artificially regenerate this species may be by allowing at least 20% of RLI for ensuring survival and at least 40% RLI for optimum growth. Key words: light, light quality, leaf morphology, acclimation.

Bifidobacteria exert species-specific effects on constipation in BALB/c mice

2017 ◽  
Vol 8 (10) ◽  
pp. 3587-3600 ◽  
Author(s):  
Linlin Wang ◽  
Lujun Hu ◽  
Qi Xu ◽  
Tian Jiang ◽  
Shuguang Fang ◽  
...  
Keyword(s):  
Specific Effects ◽  
Species Specific

Edible bifidobacteria exerted species-specific effects in relieving constipation.

scholarly journals Species-Specific Effects of Ant Inhabitants on Bromeliad Nutrition

PLoS ONE ◽  
2016 ◽  
Vol 11 (3) ◽  
pp. e0152113 ◽  
Author(s):  
Ana Z. Gonçalves ◽  
Rafael S. Oliveira ◽  
Paulo S. Oliveira ◽  
Gustavo Q. Romero
Keyword(s):  
Specific Effects ◽  
Species Specific

Distribution of leaf orientations in six conifer species

2001 ◽  
Vol 79 (4) ◽  
pp. 389-397 ◽  
Author(s):  
Hugh J Barclay
Keyword(s):  
Pseudotsuga Menziesii ◽  
Pinus Contorta ◽  
Goodness Of Fit ◽  
Tsuga Heterophylla ◽  
Picea Sitchensis ◽  
The Other ◽  
Thuja Plicata ◽  
Leaf Angle ◽  
Conifer Species ◽  
Abies Grandis

Leaf angle distributions are important in assessing both the flexibility of a plant's response to differing daily and seasonal sun angles and also the variability in the proportion of total leaf area visible in remotely sensed images. Leaf angle distributions are presented for six conifer species, Abies grandis (Dougl. ex D. Don) Lindl., Thuja plicata Donn. ex D. Don, Tsuga heterophylla (Raf.) Sarg., Pseudotsuga menziesii (Mirb.) Franco, Picea sitchensis (Bong.) Carr. and Pinus contorta Dougl. ex Loud. var. latifolia. The leaf angles were calculated by measuring four foliar quantities, and then the distributions of leaf angles are cast in three forms: distributions of (i) the angle of the long axis of the leaf from the vertical for the range 0–180°; (ii) the angle of the long axis of the leaf for the range 0–90°; and (iii) the angle of the plane of the leaf for the range 0–90°. Each of these are fit to the ellipsoidal distribution to test the hypothesis that leaf angles in conifers are sufficiently random to fit the ellipsoidal distribution. The fit was generally better for planar angles and for longitudinal angles between 0° and 90° than for longitudinal angles between 0° and 180°. The fit was also better for Tsuga heterophylla, Pseudotsuga menziesii, Picea sitchensis, and Pinus contorta than for Abies grandis and Thuja plicata. This is probably because Abies and Thuja are more shade tolerant than the other species, and so the leaves in Abies and Thuja are preferentially oriented near the horizontal and are much less random than for the other species. Comparisons of distributions on individual twigs, whole branches, entire trees, and groups of trees were done to test the hypothesis that angle distributions will depend on scale, and these comparisons indicated that the apparent randomness and goodness-of-fit increased on passing to each larger unit (twigs up to groups of trees).Key words: conifer, leaf angles, ellipsoidal distribution.

Response of wildlife to forest herbicide applications in northern coniferous ecosystems

1993 ◽  
Vol 23 (10) ◽  
pp. 2286-2299 ◽  
Author(s):  
R.A. Lautenschlager
Keyword(s):  
Small Mammal ◽  
Growing Season ◽  
Sampling Techniques ◽  
Mammal Species ◽  
Growing Seasons ◽  
Disturbed Areas ◽  
Herbicide Treatments ◽  
Species Specific ◽  
Small Mammal Species ◽  
Coniferous Ecosystems

Reviewed studies of the effects of forest herbicide applications on wildlife often lacked replication, pretreatment information, and (or) were conducted for only one or two growing seasons after treatment. Because of these problems, as well as the use of dissimilar sampling techniques, study conclusions have sometimes been contradictory. A review of eight studies of the effects of herbicide treatments on northern songbird populations in regenerating clearcuts indicates that total songbird populations are seldom reduced during the growing season after treatment. Densities of species that use early successional brushy, deciduous cover are sometimes reduced, while densities of species which commonly use more open areas, sometimes increase. A review of 14 studies of the effects of herbicide treatments on small mammals indicates that like songbirds, small mammal responses are species specific. Some species are unaffected, while some select and others avoid herbicide-treated areas. Only studies that use kill or removal trapping to study small mammal responses show density reductions associated with herbicide treatment. It seems that some small mammal species may be reluctant to venture into disturbed areas, although residents in those areas are apparently not affected by the disturbance. Fourteen relevant studies examined the effects of conifer release treatments on moose and deer foods and habitat use. Conifer release treatments reduce the availability of moose browse for as long as four growing seasons after treatment. The degree of reduction during the growing season after treatment varies with the herbicide and rate used. Deer use of treated areas remains unchanged or increases during the first growing season after treatment. Eight years after treating a naturally regenerated spruce–fir stand browse was three to seven times more abundant on treated than on control plots (depending on the chemical and rate used). Forage quality (nitrogen, ash, and moisture) of crop trees increased one growing season after the soil-active herbicide simazine was applied to control competition around outplanted 3-year-old balsam fir seedlings.

Species-specific Effects of Nitromethylene Heterocycle Insecticides on Nicotinic Receptors in Locust Neurons and Mouse N1E-115 and BC3H1 Cells

1994 ◽  
Vol 22 (6) ◽  
pp. 454-461
Author(s):  
Marga Oortgiesen ◽  
Ruud Zwart ◽  
Henk P.M. Vijverberg
Keyword(s):  
Mammalian Cells ◽  
Neuroblastoma Cells ◽  
Receptor Subtypes ◽  
Inward Current ◽  
Specific Effects ◽  
Blocking Effects ◽  
Inward Currents ◽  
Species Specific ◽  
Ganglion Neurons

The effects of nitromethylene heterocycle (NMH) insecticides on subtypes of nicotinic acetylcholine (nACh) receptors were investigated in locust thoracic ganglion neurons, mouse N1E-115 neuroblastoma cells, and mouse BC3H1 muscle cells by using electrophysiological techniques. In locust neurons, all of the six NMH insecticides tested induced transient inward currents resembling nicotinic ACh-induced inward currents, while, in the continued presence of the NMH compounds, the ACh-induced inward current was blocked. The amplitude of the inward current and the blocking effects of the NMH insecticides were enhanced by concentrations between 0.1 and 10μM. Cross-desensitisation with the ACh-induced inward current confirmed that the NMH-induced inward current was governed by the activation of nACh receptors. Mammalian endplate type nACh receptors in BC3H1 cells and mammalian neuronal type nACh receptors in N1E-115 cells were much less sensitive to the NMH insecticides than the locust neuronal nACh receptors. At a concentration of 10μM, which blocked 80–100% of the ACh-induced inward current in locust neurons, NMH insecticides only partially blocked the ACh-induced inward currents mediated by the two subtypes of mammalian nACh receptors. NMH insecticides also failed to induce significant agonist effects in the mammalian cells at this concentration. The results provide a possible explanation for the selectively greater toxicity of NMH insecticides to insects than to vertebrates, at the level of nACh receptor subtypes and, hence, demonstrate that this in vitro approach is valuable for the investigation of species-specific interactions of compounds at their target site.

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