Characteristics of stomatal diffusion resistance in a Douglas fir forest exposed to soil water deficits

1977 ◽  
Vol 7 (4) ◽  
pp. 595-604 ◽  
Author(s):  
C. S. Tan ◽  
T. A. Black ◽  
J. U. Nnyamah
Keyword(s):  
Soil Water ◽  
Soil Water Potential ◽  
High Stress ◽  
Vapour Pressure Deficit ◽  
Douglas Fir ◽  
Diffusion Resistance ◽  
Total Water ◽  
Pressure Potential ◽  
Relationship Of ◽  
The Relationship

As part of a 2-year study of the effect of thinning on evapotranspiration in Douglas fir (Pseudotsugamenziesii (Mirb.) Franco), the relationship between stomatal diffusion resistance (rs) and environmental variables were studied. Research was conducted in an unthinned stand (1840 stems ha−1) with negligible undergrowth and a thinned stand (840 stems ha−1) with substantial salal (Gaultheriashallon Pursh) undergrowth. During the daytime rs was mainly related to the soil water potential (ψs) and the vapour pressure deficit (v.p.d.) of the canopy air. Daytime values of rs for Douglas fir ranged from 2 to 60 s cm−1 for values of v.p.d. between 4 and 24 mb (4 and 24 × 102 Pa) and values of ψs between 0 and −12.5 bars (0 and −12.5 × 105 Pa). Although increasing rs was usually associated with decreasing pressure potential of the twig xylem (ψt), increasing rs appeared to be associated with increasing ψt when the v.p.d. was high. Stress history was found to cause a shift in the relationship of rs to ψt, but had little effect on the relationship of rs to v.p.d. and ψs. Daytime values of rs for salal ranged from 2 to 45 s cm−1. This stomatal behaviour suggests that as the soil dried out, salal transpiration accounted for an increasing fraction of the total water loss by the thinned stand.

Effects of salal understory removal on photosynthetic rate and stomatal conductance of young Douglas-fir trees

1986 ◽  
Vol 16 (1) ◽  
pp. 90-97 ◽  
Author(s):  
D. T. Price ◽  
T. A. Black ◽  
F. M. Kelliher
Keyword(s):  
Stomatal Conductance ◽  
Water Potential ◽  
Soil Water ◽  
Soil Water Potential ◽  
Vapour Pressure Deficit ◽  
Basal Area ◽  
Douglas Fir ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Data Set

The effects of salal (Gaultheriashallon Pursh.) understory removal on the growth of thinned 32-year-old Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) trees were determined in a stand subject to growing season soil water deficits. Four pairs of similar trees were selected and the understory was completely removed from around one of each pair, the root zones of which were both isolated using plastic sheeting buried to bedrock. Photosynthesis, stomatal conductance, soil water potential and canopy microclimate were measured intensively in one pair on 4 clear days during an extended dry period in June 1982. Basal area increment of the four pairs of trees was measured over three growing seasons. To determine the effect of soil water potential on tree photosynthesis, the same variables were intensively measured over 3 consecutive days in late August 1982 for another tree initially subjected to a soil water potential of approximately −1.6 MPa, but irrigated to approximately −0.02 MPa between the 1st and 2nd days. Solar irradiance decreased markedly between the 2nd and 3rd days, thereby creating a unique data set. Findings were as follows: (i) removal of understory significantly increased rates of photosynthesis in the trees, both diurnally and seasonally, (ii) photosynthesis was not generally limited by stomatal conductance unless vapour pressure deficit was high and photon flux density was saturating, and (iii) tree growth response to salal removal was due to higher soil water potential, which increased both photosynthetic capacity and stomatal conductance.

Needle water potential and soil-to-foliage flow resistance during soil drying: a comparison of Douglas-fir, western hemlock, and mountain hemlock

1985 ◽  
Vol 15 (1) ◽  
pp. 185-188 ◽  
Author(s):  
T. M. Ballard ◽  
M. G. Dosskey
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Water Flow ◽  
Flow Resistance ◽  
Soil Water Potential ◽  
Douglas Fir ◽  
Western Hemlock ◽  
Soil Drying ◽  
Experimental Conditions ◽  
Needle Water Potential

Needle water potential in western and mountain hemlock falls as the soil dries, but under our experimental conditions, it remained stable in Douglas-fir. Resistance to water flow from soil to foliage is higher for the hemlocks and increases more steeply as the soil dries. These findings physically account for the observation that water uptake is reduced relatively more for the hemlocks than for Douglas-fir, as soil water potential declines.

Level of Stress and Sleep Duration

1987 ◽  
Vol 64 (1) ◽  
pp. 44-46 ◽  
Author(s):  
Robert A. Hicks ◽  
Eliot R. Garcia
Keyword(s):  
Standard Deviation ◽  
Sleep Duration ◽  
High Stress ◽  
Daily Diaries ◽  
Stress Levels ◽  
Relationship Of ◽  
The Relationship

30 subjects kept daily diaries of sleep-duration and stress levels for 4 mo. From these data, it was determined that during periods of high stress, sleep was reduced by about one standard deviation while during periods of low stress, sleep increased by about one-half a standard deviation. The relationship of these results to the relevant sleep-stress literature was briefly discussed.

scholarly journals FAKTOR-FAKTOR YANG BERHUBUNGAN DENGAN KEJADIAN HIPERTENSI

2019 ◽  
Vol 8 (1) ◽  
pp. 78
Author(s):  
Mariza Elvira ◽  
Novi Anggraini
Keyword(s):  
High Stress ◽  
Cross Sectional Study ◽  
Dietary Factors ◽  
Stress Factors ◽  
P Value ◽  
Chi Square ◽  
Cross Sectional ◽  
Age Factor ◽  
Relationship Of ◽  
The Relationship

Hypertension is a condition when blood pressure increases chronically. Ministry of Health (2007) states, mortality due to hypertension ranks second of total deaths from non-communicable diseases (12.3%). The purpose of this study was to determine the factors associated with the incidence of hypertension in polyclinic disease in RSUD Dr. Achmad Mochtar Bukittinggi. This study used descriptive analytic method with cross sectional study approach with 100 respondents and using correlation dynamics technique, research instrument is questionnaire by using chi-square statistic test. The result of the study (46%) had age 35-55 years old (51%) had bad diet, (51%) had high stress and 51% respondents consumed cigarettes. The result of statistic test was found on the association of age factor with the incidence of hypertension p-value 0.031, on the association of dietary factors with the incidence of hypertension obtained p-value 0.083, on the relationship of stress factor with hypertension occurrence obtained p-value 0.050 and on the relationship of smoking factor to the incidence Hypertension was obtained p-value 0.204, so it can be concluded from the four factors, only the age factor and stress factors that are related to the incidence of hypertension. It is expected that the health service can conduct an extension activity about hypertension which will be used as routine hospital program in improving health degree

Soil Moisture as Predictor of Plant Water Status

2021 ◽  
Vol 47 (3) ◽  
pp. 110-115
Author(s):  
Johannes Hertzler ◽  
Steffen Rust
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Water Status ◽  
Soil Water Potential ◽  
Irrigation Scheduling ◽  
Plant Water Status ◽  
Plant Water ◽  
Estimation Errors ◽  
Plant Available Water ◽  
The Relationship

Soil water potential can be used as a proxy for plant available water in irrigation scheduling. This study investigated the relationship between soil water potential and plant water status of pines (Pinus sylvestris L.) planted into two different substrates. Predawn leaf water potential as a well-established measure of the plant water status and soil water potential correlated very well. However, estimating the plant water status from individual sensor readings is subject to significant estimation errors. Furthermore, it was shown that heterogeneous soil/root ball combinations can lead to critical effects on the soil water balance, and that sensors installed outside of the root balls cannot estimate the plant water status without site-specific calibration.

scholarly journals Association of morphological and water factors with irrigated forage cactus yield

2017 ◽  
Vol 21 (9) ◽  
pp. 600-605 ◽  
Author(s):  
Marcela L. Barbosa ◽  
Thieres G. F. da Silva ◽  
Sérgio Zolnier ◽  
Servulo M. S. e Silva ◽  
José E. F. de Morais ◽  
...  
Keyword(s):  
Soil Water ◽  
Correlation Matrix ◽  
Water Regime ◽  
Morphological Characteristics ◽  
Plant Morphology ◽  
Actual Evapotranspiration ◽  
Productive Capacity ◽  
The Moment ◽  
Relationship Of ◽  
The Relationship

ABSTRACT This study aimed to understand the relationship of morphological characteristics and actual evapotranspiration of forage cactus clones with their productive capacity under different water regimes. The data used in this study were collected between the years 2012 and 2013, in Serra Talhada, State of Pernambuco. The clones Sertânia IPA - IPA, Miúda - MIU and Orelha de Elefante Mexicana - OEM were submitted to three irrigation depths (2.5, 5.0 and 7.5 mm) and three irrigation intervals (7, 14 and 28 days). Cladode and plant morphology, accumulated actual evapotranspiration and yield were obtained at the moment of harvest. Pearson’s correlation matrix was elaborated and, in the sequence, multicollinearity, canonical and path analysis were applied. There was no correlation of yield with the soil water supply and actual evapotranspiration of the clones (p > 0.05). Forage cactus yield was more associated with peculiarities of the morphological characteristics of the clones than with the different soil water supplies or the crop actual evapotranspiration. However, regardless of the water regime and clone, the vigor of the basal cladodes was highly decisive for the expression of the forage cactus productive capacity.

scholarly journals Investigation on the relationship of proline with wheat anti-drought under soil water deficits

2006 ◽  
Vol 53 (1) ◽  
pp. 113-119 ◽  
Author(s):  
Shao Hong-Bo ◽  
Chen Xiao-Yan ◽  
Chu Li-Ye ◽  
Zhao Xi-Ning ◽  
Wu Gang ◽  
...  
Keyword(s):  
Soil Water ◽  
Water Deficits ◽  
Relationship Of ◽  
The Relationship

scholarly journals Personal Accomplishment and Hardiness in Reducing Emergency Stress and Burnout among COVID-19 Emergency Workers

2020 ◽  
Vol 12 (21) ◽  
pp. 9071
Author(s):  
Monia Vagni ◽  
Valeria Giostra ◽  
Tiziana Maiorano ◽  
Giuliano Santaniello ◽  
Daniela Pajardi
Keyword(s):  
Emotional Exhaustion ◽  
High Stress ◽  
Personal Accomplishment ◽  
Stress Factors ◽  
Red Cross ◽  
Emergency Workers ◽  
Stress Levels ◽  
High Stress Level ◽  
Relationship Of ◽  
The Relationship

During the severe phase of the pandemic, COVID-19 emergency workers were engaged in long and numerous shifts of duty, resulting in exposure to various stress factors. A high stress level is associated with risk of burnout. Resilience and personal accomplishment can effectively help mitigate and reduce emergency stress levels and emotional exhaustion. The main aim of this study was to analyze the relationship of emergency stress and hardiness with burnout among emergency workers. The participants included 494 emergency volunteers from the Red Cross Committee in Veneto, Italy, engaged in various health, emergency, and social activities aimed at COVID-19 patients and people at risk of contracting the virus. Questionnaires used to measure emergency stress, hardiness and burnout were administered on an online platform. We analyzed the influence of age, sex, weekly hours of service, stress risk factors, and use of personal protective equipment. To verify the predictive effects of risk and protective factors on burnout, correlational and multivariate analyses, and regressions were conducted. Hardiness showed an effect in reducing emergency stress levels, emotional exhaustion, and depersonalization and simultaneously increased personal accomplishment.

Sign in / Sign up

Export Citation Format

Share Document