Factors Affecting Stomatal Conductance of Bracken Below a Forest Canopy

1984 ◽  
Vol 21 (2) ◽  
pp. 643 ◽  
Author(s):  
J. Roberts ◽  
J. S. Wallace ◽  
R. M. Pitman
Keyword(s):  
Stomatal Conductance ◽  
Forest Canopy ◽  
Factors Affecting

scholarly journals Modelling bi-directional fluxes of methanol and acetaldehyde with the FORCAsT canopy exchange model

2016 ◽  
Author(s):  
Kirsti Ashworth ◽  
Serena H. Chung ◽  
Karena A. McKinney ◽  
Ying Liu ◽  
Bill J. Munger ◽  
...  
Keyword(s):  
Stomatal Conductance ◽  
Atmospheric Chemistry ◽  
Forest Canopy ◽  
Global Scale ◽  
Exchange Model ◽  
Forest Site ◽  
Canopy Exchange ◽  
Harvard Forest ◽  
Leaf Level ◽  
Underlying Mechanisms

Abstract. The FORCAsT canopy exchange model was used to investigate the underlying mechanisms governing foliage emissions of methanol and acetaldehyde, two short chain oxygenated volatile organic compounds ubiquitous in the troposphere and known to have strong biogenic sources, at a northern mid-latitude forest site. The explicit representation of the vegetation canopy within the model allowed us to test the hypothesis that stomatal conductance regulates emissions of these compounds to an extent that its influence is observable at the ecosystem-scale, a process not currently considered in regional or global scale atmospheric chemistry models. We found that FORCAsT could only reproduce the magnitude and diurnal profiles of methanol and acetaldehyde fluxes measured at the top of the forest canopy at Harvard Forest if light-dependent emissions were introduced to the model. With the inclusion of such emissions FORCAsT was able to successfully simulate the observed bi-directional exchange of methanol and acetaldehyde. Although we found evidence that stomatal conductance influences methanol fluxes and concentrations at scales beyond the leaf-level, particularly at dawn and dusk, we were able to adequately capture ecosystem exchange without the addition of stomatal control to the standard parameterisations of foliage emissions, suggesting that ecosystem fluxes can be well enough represented by the emissions models currently used.

Factors affecting the availability of thick epiphyte mats and other potential nest platforms for Marbled Murrelets in British Columbia

2010 ◽  
Vol 40 (4) ◽  
pp. 727-746 ◽  
Author(s):  
Alan E. Burger ◽  
Robert A. Ronconi ◽  
Michael P. Silvergieter ◽  
Catherine Conroy ◽  
Volker Bahn ◽  
...  
Keyword(s):  
British Columbia ◽  
Forest Canopy ◽  
Tree Height ◽  
Suitable Habitat ◽  
Factors Affecting ◽  
Marbled Murrelet ◽  
Pooled Data ◽  
Model Predictions ◽  
Using Data ◽  
Marbled Murrelets

Nest platforms (mossy pads, limbs, and deformities >15 cm in diameter) are key requirements in the forest nesting habitat of the threatened Marbled Murrelet ( Brachyramphus marmoratus (J.F. Gmelin, 1789)). Little is known about factors that affect the availability of platforms or the growth of canopy epiphytes that provide platforms. We examined variables affecting these parameters in coastal trees in British Columbia using data from 29 763 trees at 1412 sites in 170 watersheds. Tree diameter (diameter at breast height (DBH)) was the most important predictor of platform availability in the pooled data and within each of six regions. In most regions, platforms become available at DBH > 60 cm, but on East Vancouver Island, DBH needs to be >96 cm and possibly on the Central Coast >82 cm. Other regional predictors of platforms included tree height, tree species, and to a lesser extent elevation, slope, and latitude. Most (72%) trees providing platforms had epiphytes (mainly moss) covering one third or more of branch surfaces and 81% had intermediate or thick epiphyte mats. Mistletoe deformities provided <7% of platforms. Our model predictions help to define and manage suitable habitat for nesting Marbled Murrelets and also contribute to understanding forest canopy ecosystems.

scholarly journals Variability in aboveground carbon driven by slope aspect and curvature in an eastern deciduous forest, USA

2017 ◽  
Vol 47 (2) ◽  
pp. 149-158 ◽  
Author(s):  
Lauren A. Smith ◽  
David M. Eissenstat ◽  
Margot W. Kaye
Keyword(s):  
Spatial Variability ◽  
Tree Species ◽  
Forest Canopy ◽  
Deciduous Forest ◽  
Local Variation ◽  
Slope Aspect ◽  
Litter Production ◽  
Eastern Deciduous Forest ◽  
Factors Affecting ◽  
Species Specific

In forested ecosystems, topography and tree species contribute to spatial variability in carbon (C) dynamics through differential rates of C uptake and storage; therefore, estimates of species-specific and spatial variability in C can strengthen ecosystem budgets. To produce such estimates, we deconstructed watershed-scale C and component pools (e.g., wood biomass, litter) and fluxes at a fine scale using a small mixed deciduous forest catchment to determine the variation due to topographic position and species. Factors affecting fluxes included aspect, slope curvature, tree species contributions, and litter production. Annual C uptake into wood varied across the catchment from 0 to 34 kg C·year−1 and was 20% greater on southern aspects than northern ones and 33% greater in swales than non-swale slopes. Of the more than 20 tree species found in the forest canopy of the catchment, highest C uptake in woody biomass was measured in Quercus rubra L. growing in swales, followed by Quercus prinus L. syn. growing on the southern aspect, with the lowest aboveground wood increment measured in Pinus at higher elevations on non-swale slopes. Quercus leaf litter moved from where it dropped into litter traps to where it settled on the forest floor, shifting the location of litter C inputs to the soil. Local variation in aboveground C rivals regional variation across regions and has the potential to introduce error when scaling C measures from points to landscapes.

Water Potential and Stomatal Conductance of Three Eucalyptus Species in the Mount Lofty Ranges, South Australia: Responses to Summer Drought

1980 ◽  
Vol 28 (6) ◽  
pp. 499 ◽  
Author(s):  
R Sinclair
Keyword(s):  
Stomatal Conductance ◽  
Water Potential ◽  
South Australia ◽  
Late Summer ◽  
Distribution Patterns ◽  
The Other ◽  
Late Winter ◽  
Eucalyptus Species ◽  
Summer Drought ◽  
Factors Affecting

Water potential and stomatal conductance were measured for three eucalypt species: Eucalyptus obliqua L'Hérit., E. fasciculosa F. Muell. and E. leucoxylon F. Muell. Field sites were located in the Mt Lofty Ranges, S.A., near the lower altitudinal limits of the E. obliqua population, where this species begins to be replaced by one or other of the other two. Pairs of trees, one pair of each species, were selected at each site growing within a few metres of each other. Measurements were made in late winter 1977 and during the unusually dry summer of 1977-78. In late winter E. obliqua and E. fasciculosa results were similar. Both had dawn water potential maxima of approximately -0.4 MPa, and stomatal conductance was high throughout the day. By mid summer E. obliqua was suffering water stress. Dawn water potential maxima of -1.93 and -4.35 MPa were measured, and stomatal conductance was low, but not zero, throughout the day. Adjacent E. fasciculosa showed few signs of stress; dawn maximum water potential was -0.7 MPa, and stornatal conductances were high. By late summer both water potentials and stornatal conductances of E. obliqua were much lower than those of adjacent trees of either of the other two species. The significance of these differences is discussed in relation to factors affecting eucalypt distribution patterns.

scholarly journals Tree Surface Temperature in a Primary Tropical Rain Forest

Atmosphere ◽  
2020 ◽  
Vol 11 (8) ◽  
pp. 798
Author(s):  
Qinghai Song ◽  
Chenna Sun ◽  
Yun Deng ◽  
He Bai ◽  
Yiping Zhang ◽  
...  
Keyword(s):  
Stomatal Conductance ◽  
Tree Species ◽  
Rain Forest ◽  
Tropical Rain Forest ◽  
Leaf Size ◽  
Leaf Temperature ◽  
Plant Distribution ◽  
Factors Affecting ◽  
Thermal Cameras ◽  
The Mean

As one of the important factors affecting plant productivity and plant distribution, temperature also affects the physiological and ecological characteristics of plants to a large extent. We report canopy leaf temperature distribution over a 36 m tall primary tropical rain forest and samplings of 28 tree species in SW China by means of two high resolution thermal cameras (P25, Flir systems, Wilsonville, OR, USA). The leaf temperature of dominant tree Species Pometia tomentosa was the highest (31.8 °C), 10.2 °C higher than that of tree species Mezzettipsis creaghii (21.6 °C). The mean leaf to air temperature difference (Tc–Ta) of Pometia tomentosa was the highest (6.4 K), the second highest was Barringtonia pendula (6.1 K), and Mezzettipsis creaghii had the lowest (Tc–Ta) (1.9K). (Tc–Ta) of tree species with smaller leaves and larger stomatal conductance was lowly sensitive to climate factors. Leaf size and stomatal conductance together decided the effect of climate change to (Tc–Ta) of the different tree species. We have shown that the composition of tree species in tropical rain forest areas is important to the climate through our research.

scholarly journals Effects of Powdery Mildew of Grape on Carbon Assimilation Mechanisms of Potted `Chardonnay' Grapevines

HortScience ◽  
2004 ◽  
Vol 39 (7) ◽  
pp. 1670-1673 ◽  
Author(s):  
William R. Nail ◽  
G. Stanley Howell
Keyword(s):  
Chlorophyll Fluorescence ◽  
Stomatal Conductance ◽  
Powdery Mildew ◽  
Photochemical Efficiency ◽  
Carbon Assimilation ◽  
Compensation Point ◽  
Uncinula Necator ◽  
Assimilation Rate ◽  
Factors Affecting ◽  
Stomatal Limitations

Potted grapevines (Vitis vinifera L. `Chardonnay') were inoculated with conidial suspensions of the grapevine pathogen causing powdery mildew of grape (GPM) (Uncinula necator (Schw.) Burr.). Leaves of inoculated and noninoculated vines were studied for the effects of varying light (PAR) and CO2 concentrations on factors affecting carbon assimilation. GPM reduced carboxylation efficiency (k), net CO2 assimilation rate (A), stomatal conductance (gs), and internal CO2 concentration (Ci) under ambient CO2, Amax at >900 ppm CO2, stomatal limitations to A (lg), and photochemical efficiency (Φ) on diseased leaves, while having no effect on the CO2 compensation point (Γ) or the light compensation point (cp). GPM had no significant effect on chlorophyll fluorescence (Fv/Fm).

scholarly journals Modelling bidirectional fluxes of methanol and acetaldehyde with the FORCAsT canopy exchange model

2016 ◽  
Vol 16 (24) ◽  
pp. 15461-15484 ◽  
Author(s):  
Kirsti Ashworth ◽  
Serena H. Chung ◽  
Karena A. McKinney ◽  
Ying Liu ◽  
J. William Munger ◽  
...  
Keyword(s):  
Stomatal Conductance ◽  
Atmospheric Chemistry ◽  
Forest Canopy ◽  
Global Scale ◽  
Exchange Model ◽  
Forest Site ◽  
Canopy Exchange ◽  
Leaf Level ◽  
Underlying Mechanisms ◽  
Bidirectional Exchange

Abstract. The FORCAsT canopy exchange model was used to investigate the underlying mechanisms governing foliage emissions of methanol and acetaldehyde, two short chain oxygenated volatile organic compounds ubiquitous in the troposphere and known to have strong biogenic sources, at a northern mid-latitude forest site. The explicit representation of the vegetation canopy within the model allowed us to test the hypothesis that stomatal conductance regulates emissions of these compounds to an extent that its influence is observable at the ecosystem scale, a process not currently considered in regional- or global-scale atmospheric chemistry models.We found that FORCAsT could only reproduce the magnitude and diurnal profiles of methanol and acetaldehyde fluxes measured at the top of the forest canopy at Harvard Forest if light-dependent emissions were introduced to the model. With the inclusion of such emissions, FORCAsT was able to successfully simulate the observed bidirectional exchange of methanol and acetaldehyde. Although we found evidence that stomatal conductance influences methanol fluxes and concentrations at scales beyond the leaf level, particularly at dawn and dusk, we were able to adequately capture ecosystem exchange without the addition of stomatal control to the standard parameterisations of foliage emissions, suggesting that ecosystem fluxes can be well enough represented by the emissions models currently used.

Progress In The Practical Application Of Automated Image Analysis To Tem Negatives

1977 ◽  
Vol 35 ◽  
pp. 214-217
Author(s):  
F. A. Heckman ◽  
E. Redman ◽  
J.E. Connolly
Keyword(s):  
Image Analysis ◽  
Image Quality ◽  
Exposure Time ◽  
Image Contrast ◽  
Automated Image Analysis ◽  
Practical Application ◽  
Factors Affecting ◽  
High Image Quality ◽  
Qualitative Evidence ◽  
Comprehensive Study

In our initial publication on this subject1) we reported results demonstrating that contrast is the most important factor in producing the high image quality required for reliable image analysis. We also listed the factors which enhance contrast in order of the experimentally determined magnitude of their effect. The two most powerful factors affecting image contrast attainable with sheet film are beam intensity and KV. At that time we had only qualitative evidence for the ranking of enhancing factors. Later we carried out the densitometric measurements which led to the results outlined below.Meaningful evaluations of the cause-effect relationships among the considerable number of variables in preparing EM negatives depend on doing things in a systematic way, varying only one parameter at a time. Unless otherwise noted, we adhered to the following procedure evolved during our comprehensive study:Philips EM-300; 30μ objective aperature; magnification 7000- 12000X, exposure time 1 second, anti-contamination device operating.

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