Effects of overtopping vegetation on light availability and growth of Engelmann spruce (Piceaengelmannii) seedlings

1993 ◽  
Vol 23 (10) ◽  
pp. 2044-2048 ◽  
Author(s):  
Philip G. Comeau ◽  
Thomas F. Braumandl ◽  
Chang-Yi Xie
Keyword(s):  
Seedling Growth ◽  
Objective Assessment ◽  
Light Availability ◽  
Field Measurements ◽  
Percent Cover ◽  
Competition Index ◽  
Full Sunlight ◽  
Vegetation Height ◽  
Engelmann Spruce ◽  
Neighborhood Studies

To examine the effects of overtopping vegetation on solar irradiance reaching Engelmann spruce (Piceaengelmannii Parry) seedlings and on crop seedling performance, neighborhood studies were established at six sites in mixed shrub–herb and fireweed communities of the Interior Cedar–Hemlock zone of southern British Columbia. These communities were dominated by mixtures of fireweed (Epilobiumangustifolium L.), thimbleberry (Rubusparviflorus Nutt.), red raspberry (Rubusidaeus L.), and (or) bracken fern (Pteridiumaquilinum (L.) Kuhn). Three hundred and eighty-eight planted Engelmann spruce seedlings, between 1 and 5 years of age, served as plot centers for measurements in 1990 and 1991. Vegetation had been clipped around 109 of these seedlings in 1988, 1989, and 1990. Seedling diameter and height were measured in the autumn of 1990 and 1991. Vegetation cover, vegetation height, and the fraction of full sunlight reaching the top branches of each spruce seedling were measured in midsummer of 1991. A simple competition index (CI), based on visually estimated percent cover, height of each species present within 1.26 m of the crop seedling, and crop-seedling height, can be used to estimate the fraction of full sunlight reaching crop seedlings. Measurements of transmittance through vegetation canopies are correlated with this competition index and could be useful as a separate, objective assessment of competition levels. Seedling growth was related to both seedling-needle biomass (at the beginning of the year) and either CI or the amount of light reaching crop seedlings during midsummer. Growth increased as needle biomass or irradiance reaching the seedling increased and decreased as CI increased. Since CI can be calculated from simple field measurements and since seedling growth is related to CI, this index has potential utility in evaluating the need for operational release treatments. Transmittance measurement provides an equally useful, and potentially more objective approach to evaluating the need for release treatment. Results from this study suggest that cumulative effects of competition result at least in part from effects on growth of seedling leaf mass.

Light and temperature differentially colimit subalpine fir and Engelmann spruce seedling growth in partial-cut subalpine forests

2004 ◽  
Vol 34 (1) ◽  
pp. 249-260 ◽  
Author(s):  
Cleo C Lajzerowicz ◽  
Michael B Walters ◽  
Marek Krasowski ◽  
Hugues B Massicotte
Keyword(s):  
Soil Temperature ◽  
Seedling Growth ◽  
Light Availability ◽  
N Availability ◽  
Abies Lasiocarpa ◽  
Soil N ◽  
Subalpine Forests ◽  
Subalpine Fir ◽  
Engelmann Spruce ◽  
Soil Temperatures

We compared the relative impacts of light, soil N, and soil temperature on Engelmann spruce (Picea engelman nii Parry ex Engelm.) and subalpine fir (Abies lasiocarpa (Hook.) Nutt.) seedling growth by quantifying (i) microsite environment-growth relationships for N-fertilized and unfertilized planted seedlings in shelterwood, patch cut, and clearcut harvest treatments and (ii) growth, photosynthesis, and biomass allocation for greenhouse-grown seedlings at 5, 10, and 15 °C soil temperatures. Fertilization did not affect seedling growth. Furthermore, soil N availability did not vary among harvest treatments. In contrast, clearcut compared with shelterwood seedlings had greater mass (fivefold), light availability (twofold), and soil temperatures (1.6 °C). Across harvest treatments, spruce and fir mass increased linearly to 100% open-sky light (R2 = 0.51 and 0.57, respectively), and temperature and light combined explained more variation in mass than light alone (adjusted R2 = 0.58 for both species). Spruce growth was more sensitive to temperature than fir in both field and greenhouse experiments. Diminished growth at low soil temperature was associated with lower photosynthesis and not lower leaf fraction. Thus, soil temperature and light colimit seedling growth in subalpine forests, but responses were species-specific and consistent with microenvironment differences in spruce and fir regeneration niches.

Vegetation dynamics in declining eastern hemlock stands: 9 years of forest response to hemlock woolly adelgid infestation

2006 ◽  
Vol 36 (6) ◽  
pp. 1435-1450 ◽  
Author(s):  
Anne K Eschtruth ◽  
Natalie L Cleavitt ◽  
John J Battles ◽  
Richard A Evans ◽  
Timothy J Fahey
Keyword(s):  
Invasive Plants ◽  
Light Availability ◽  
Hemlock Woolly Adelgid ◽  
Adelges Tsugae ◽  
Eastern Hemlock ◽  
Percent Cover ◽  
Eastern United States ◽  
Transmitted Radiation ◽  
Exotic Invasive ◽  
Exotic Invasive Plants

Hemlock woolly adelgid (HWA; Adelges tsugae Annand) infestations have resulted in the continuing decline of eastern hemlock (Tsuga canadensis (L.) Carrière) throughout much of the eastern United States. In 1994 and 2003, we quantified the vegetation composition and structure of two hemlock ravines in the Delaware Water Gap National Recreation Area. This is the first study to use pre-adelgid disturbance data, annual monitoring of infestation severity, and annual records of hemlock health to assess forest response to HWA infestation. In 2003, 25% of monitored hemlock trees were either dead or in severe decline. Measures of hemlock decline (crown vigor, transparency, density, and dieback) were correlated with HWA infestation severity and changes in light availability over the study period. Average percent total transmitted radiation more than doubled at these sites from 5.0% in 1994 to 11.7% in 2003. The total percent cover of vascular plants increased from 3.1% in 1994 to 11.3% in 2003. Species richness increased significantly, and more species were gained (53) than lost (19) from both ravine floras over the 9-year study period. Though exotic invasive plants were absent from these ravines in 1994, our 2003 resurvey found invasive plants in 35% of the permanent vegetation plots.

Factors influencing understory seedling establishment of Engelmann spruce (Picea engelmannii) and subalpine fir (Abies lasiocarpa) in southeast Wyoming

1982 ◽  
Vol 60 (12) ◽  
pp. 2753-2761 ◽  
Author(s):  
Alan K. Knapp ◽  
William K. Smith
Keyword(s):  
Seedling Establishment ◽  
Rocky Mountain ◽  
Field Measurements ◽  
Incident Radiation ◽  
Picea Engelmannii ◽  
Abies Lasiocarpa ◽  
Northern Rocky Mountains ◽  
Medicine Bow Mountains ◽  
Engelmann Spruce ◽  
Surface Drying

Although seedlings of Abies lasiocarpa are generally more abundant than those of Picea engelmannii in the understory of mature spruce–fir forests throughout the central and northern Rocky Mountains, little information exists concerning environmental or plant factors that may influence the establishment of these two conifers. Field measurements in the Medicine Bow Mountains of southeast Wyoming showed that seedlings of A. lasiocarpa had greater photosynthetic rates at low understory light levels and required lower levels of incident radiation for saturation of photosynthesis compared with those of P. engelmannii. However, both conifers occurred in understory locations where total daily solar radiation was equally low (<2 MJ∙m−2∙day−1) and thus, a lack of light did not appear to be responsible for the low number of P. engelmannii seedlings in the understory. In contrast, seedlings of P. engelmannii were substantially more abundant at locations with thinner litter layers compared with those of A. lasiocarpa. Also, laboratory studies showed that the smaller seeds of P. engelmannii germinated more rapidly and at lower temperatures than seeds of A. lasiocarpa although growth of tap roots on A. lasiocarpa seedlings was greater initially ([Formula: see text] longer in 2-week-old seedlings) as well as for 10-week-old seedlings (50% longer). The deeper penetrating tap root of A. lasiocarpa seedlings may enable this conifer to establish more abundantly on thick, rapidly drying litter layers that are characteristic of mature spruce–fir forests. In contrast, establishment of P. engelmannii seedlings may be limited to microsites without a thick litter layer such as disturbed areas or decomposing wood, where surface drying may occur more gradually throughout the summer. These results are discussed in terms of the potential effects of seedling establishment on the observed patterns in climax vegetation of central and northern Rocky Mountain subalpine forests.

scholarly journals Effects of crevice size on the establishment of macroalgae in subtropical streams

2014 ◽  
Vol 74 (4) ◽  
pp. 803-809
Author(s):  
AF Tonetto ◽  
CK Peres ◽  
MA Khnayfes ◽  
CCZ Branco
Keyword(s):  
Surface Roughness ◽  
Plane Surface ◽  
Algal Growth ◽  
Percent Cover ◽  
Weak Effect ◽  
Southern Brazil ◽  
Full Sunlight ◽  
Macroalgal Community ◽  
Stream Macroalgae ◽  
Different Shapes

Considering that in previous studies, the surface roughness (micrometric dimension) showed a weak effect on the colonization of stream macroalgae, we investigated the effects of different crevice sizes (milimetric dimension, a scale slightly higher than previous investigations) on the macroalgal abundance in three streams exposed to full sunlight in southern Brazil. We used smooth sterile glass plates with different shapes: P – plane surface without crevices; S – sinuous surface (depth of crevices with 0.159 mm ± 0.03); N – non-unifom surface (0.498 mm ± 0.09); C – surfaces with convex structures (1.190 mm ± 0.12); and three additional surface types with different patterns of heterogeneity with combinations of glass pieces: P + S (H1); P + S + N (H2) and P + S + N + C (H3). The plates were placed into the streams and after 105 days the percent cover of macroalgal community was measured. No significant differences among treatments were recorded. However, we observed a trend of macroalgae occurs within the crevices in all treatments and this suggests that, for stream macroalgae, the crevice sizes used in this study was still not enough to provide an expressive algal growth, even in the treatment with bigger crevices.

Stomatal control and the development of water deficit in Engelmann spruce seedlings during drought

1979 ◽  
Vol 9 (3) ◽  
pp. 297-304 ◽  
Author(s):  
Merrill R. Kaufmann
Keyword(s):  
Flux Density ◽  
Stomatal Closure ◽  
Absolute Humidity ◽  
Pressure Potential ◽  
Evaporative Demand ◽  
Xylem Pressure ◽  
Full Sunlight ◽  
Engelmann Spruce ◽  
Xylem Pressure Potential ◽  
The Relationship

The effects of soil drying on water relations of Engelmann spruce (Piceaengelmannii Engelm.) were studied by withholding water from 4-year-old potted seedlings in full sunlight and under a shade screen transmitting 55–60% light. During a period of 2 months, xylem pressure potential, water vapor conductance, and transpirational flux density gradually declined compared with well watered controls, with drying being more rapid in full sunlight. As drying progressed, xylem pressure potential at 0 transpiration (predawn potential) decreased and the slope of the relationship between xylem pressure potential and transpirational flux density became more negative. Hysteresis in the relationship occurred when predawn xylem pressure potential was −6 bars (1 bar = 105 Pa) or lower. Needle conductance during daylight hours decreased as the absolute humidity difference from leaf to air increased but conductances were lower in September than in August for given humidity differences. Xylem pressure potentials between −15 and −19 bars had no clear effect on conductance in August but apparently caused significant stomatal closure in September. Because of humidity-induced stomatal closure, evaporative demand had little effect on transpirational flux density over a broad range of humidity gradient. Thus increased leaf-to-air vapor gradients for transpiration are not always accompanied by increased transpiration.

Sustainable Design of Smart Health Facilities in Seismically Prone Areas

2013 ◽  
Vol 569-570 ◽  
pp. 278-285 ◽  
Author(s):  
Carlo Rainieri ◽  
Giovanni Fabbrocino
Keyword(s):  
Objective Assessment ◽  
Field Measurements ◽  
Health Facilities ◽  
Ease Of Use ◽  
Structural Members ◽  
Structural Components ◽  
Term Basis ◽  
Smart Health ◽  
Supply Systems

Safety ofhealth facilities (hospitals) is only partially related to the performance ofprimary structural members. Modern seismic codes provide strict requirements toboth structural and non-structural components, since the latterare alsocritical to ensure that the system remains fully operational in the case offrequent earthquakes. Thus, performance and safety checks apply also to electro-mechanicaland medical equipment,elevators, tanks, power supply systems, distributionsystems, heating, ventilation and air-conditioning systems.In the present paperattention is focusedon the analysis of the factors which make health facilities vulnerable and onthe issues related to a rational and objective assessment of performance andhealth state of structural and non-structural components. This is not a trivialtask, since functions and resilience of the system as a whole depend also onthe ability of inspectors and managers to integrate theoretical evaluationswith field measurements and their physical meaning.In this context, strategies and recommendations for a sustainableimplementation of Smart Health Facilities, which fulfilAtoE characteristics (Accuracy, Budget compliance, Computational burden,Durability, Ease of use)on a long term basis, are discussed, taking into account the specific requirementsand characteristics of the different subsystems in a hospital.

Neighborhood predictors of interspecific competition in young Douglas-fir plantations

1991 ◽  
Vol 21 (6) ◽  
pp. 821-828 ◽  
Author(s):  
Robert G. Wagner ◽  
Steven R. Radosevich
Keyword(s):  
Interspecific Competition ◽  
Woody Plants ◽  
Woody Species ◽  
Spatial Arrangement ◽  
Douglas Fir ◽  
Stem Diameter ◽  
Tree Age ◽  
Percent Cover ◽  
Competition Index ◽  
Neighborhood Models

Neighborhood models describing the effect of interspecific competition on the height and stem diameter of 4- to 9-year-old saplings of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) were developed from site-preparation experiments in the Oregon Coast Range. The influence of abundance measures, height, distance, arid spatial arrangement of nonconiferous woody plants surrounding individual saplings was examined. Optimum neighborhood heights and radii were defined. The best interspecific competition index for predicting Douglas-fir height and stem diameter was total percent cover for all woody species within a 2.1-m radius. Visual estimates of neighbor cover were superior to objective measures of crown area. The cover of woody species equalling or exceeding the height of the tree provided the best prediction for tree height. Woody species cover equalling or exceeding one-half the height of the tree provided the best index for predicting stem diameter. Accounting for the spatial arrangement of neighboring woody plants did not improve the competition index. Interaction between the competition index and tree age indicated that the negative effect of interspecific competition on Douglas-fir size increased with time. The age-adjusted competition index accounted for 11% of the variation in height and 19% of the variation in stem diameter. Douglas-fir stem diameter was more sensitive to neighboring woody plants than was height.

scholarly journals Limited natural regeneration of unique Scalesia forest following invasive plant removal in Galapagos

PLoS ONE ◽  
2021 ◽  
Vol 16 (10) ◽  
pp. e0258467
Author(s):  
Anna Walentowitz ◽  
Michael Manthey ◽  
María Belén Bentet Preciado ◽  
Rafael Chango ◽  
Christian Sevilla ◽  
...  
Keyword(s):  
Plant Species ◽  
Natural Regeneration ◽  
Large Scale ◽  
Invasive Plant ◽  
Linear Models ◽  
Light Availability ◽  
Percent Cover ◽  
Introduced Plants ◽  
Adult Trees ◽  
Sapling Survival

More than 60% of the flora of the Galapagos Islands is introduced and some of these species have become invasive, severely altering ecosystems. An example of an affected ecosystem is the Scalesia forest, originally dominated by the endemic giant daisy tree Scalesia pedunculata (Asteraceae). The remnant patches of this unique forest are increasingly being invaded by introduced plants, mainly by Rubus niveus (blackberry, Rosaceae). To help large-scale restoration of this ecologically important forest, we seek to better understand the natural regeneration of S. pedunculata after invasive plant control. We monitored naturally recruited S. pedunculata saplings and young trees over five years in an area where invasive plant species are continuously being removed by manual means. We measured survival, height and growth of S. pedunculata saplings and young trees along permanent transects. Percent cover of surrounding plant species and of canopy shade directly above each S. pedunculata individual were determined, as well as distance to the next mature S. pedunculata tree. We identified potential factors influencing initial sapling survival and growth by applying generalized linear models. Results showed a rapid growth of saplings and young trees of up to 0.45 cm per day and a high mortality rate, as is typical for pioneer species like S. pedunculata. Sapling survival, growth and mortality seemed to be influenced by light availability, surrounding vegetation and distance to the next adult S. pedunculata tree. We concluded that natural regeneration of S. pedunculata was high only five months after the last herbicide application but that 95% of these recruits had died over the 5-year period. Further studies are needed to corroborate whether the number of surviving trees is sufficient to replace the aging adult trees and this way maintain remnants of the Scalesia forest. Urgent action is needed to help improve future restoration strategies to prevent further degradation of this rapidly shrinking threatened forest ecosystem.

Comparison of laser and field measurements of vegetation height and canopy cover

1994 ◽  
Vol 30 (5) ◽  
pp. 1311-1319 ◽  
Author(s):  
Mark A. Weltz ◽  
Jerry C. Ritchie ◽  
H. Dale Fox
Keyword(s):  
Canopy Cover ◽  
Field Measurements ◽  
Vegetation Height

scholarly journals Effectiveness of Repeated Manual Cutting and Glyphosate for Release of Engelmann Spruce from Mixed-Shrub Herb Vegetation

2000 ◽  
Vol 15 (3) ◽  
pp. 154-162 ◽  
Author(s):  
P. G. Comeau ◽  
B. S. Biring ◽  
G. J. Harper
Keyword(s):  
Vegetation Cover ◽  
Vascular Plant ◽  
Plant Cover ◽  
Picea Engelmannii ◽  
Seedling Height ◽  
Vegetation Height ◽  
Engelmann Spruce ◽  
Collar Diameter ◽  
Glyphosate Herbicide ◽  
Root Collar

Abstract This study, initiated in 1992, examined the effectiveness of repeated cutting for controlling vegetation in a mixed-shrub-herb community to release planted Engelmann spruce (Picea engelmannii) seedlings. Eight treatments were compared: (a) cut once in spring of 1992, (b) cut once in summer of 1992, (c) 3 yr of cutting once annually in the spring (mid to late June) starting in 1992, (d) 3 yr of cutting once annually in the summer (late July) starting in 1992, (e) 3 yr of cutting twice annually, in the spring and in the summer starting in 1992, (f) 2 yr of cutting twice annually, in the spring and in the summer starting in 1993, (g) application of glyphosate herbicide at 2.1 kg ai/ha during late August, 1992, and (h) an untreated control. Treatments were replicated 3 times in 30 × 30 m plots. Glyphosate treatment (g) and spring cutting treatments (c, e, and J) significantly reduced vegetation (vascular plant) cover and height compared to the control in 1993 and 1994. There were no significant differences in vegetation cover among treatments in year 5 (1996), but vegetation height was significantly lower in the glyphosate treatment (g) and repeated cutting treatments (c, d, e, and f) compared to the control. After 5 yr, spruce survival was high for both control (86%) and treated (> 91%) plots, with no significant (P ≤ 0.05) differences detected among treatments. Repeated cutting treatments (c, d, e, and f) and glyphosate treatment (g) significantly increased root collar diameter (rcd) over that of untreated (h) seedlings, and repeated summer cutting (d) significantly increased seedling height. Three years of repeated cutting (c, d, and e) increased rcd by 54%, and glyphosate (g) increased rcd by 46% compared to the control (h). At the end of year 5, seedlings receiving 3 yr of cutting (e) were not significantly larger than seedlings receiving only 2 yr of cutting (J). West. J. Appl. For. 15(3):154-162.

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