Moss leaf water content and solar radiation at the moss surface in a mature black spruce forest in central Alaska

1983 ◽  
Vol 13 (5) ◽  
pp. 860-868 ◽  
Author(s):  
O. Skre ◽  
W. C. Oechel ◽  
P. M. Miller
Keyword(s):  
Wind Speed ◽  
Vapor Pressure ◽  
Water Content ◽  
Water Loss ◽  
Forest Canopy ◽  
Black Spruce ◽  
Field Measurements ◽  
The Other ◽  
Leaf Water Content ◽  
Moss Species

In a mature black spruce (Piceamariana (Mill.) B.S.P.) forest near the University of Alaska, Fairbanks, AK, samples of four common moss species, Polytrichumcommune Hedw., Hylocomiumsplendens (Hedw.) B.S.G., Pleuroziumschreberi (Brid.) Mitt., and Sphagnumsubsecundum Nees. were collected at intervals during the 1976 season to determine the diurnal variation in leaf water content and daily water loss as functions of temperature, moisture, radiation, and wind speed. The field measurements were followed by laboratory experiments on intact cores in an open system and on excised shoots in closed cuvettes. In these experiments, water loss rates varied by species and were affected by vapor pressure deficits and wind speed; where vapor pressure deficit is more constant than these other factors, variations in light intensities had less effect on water loss rates. Polytrichumcommune, which translocates water from the soil, avoided moisture stress to a greater extent than the other moss species which were more dependent on water absorption through the leaves. Hylocomiumsplendens was below the water content for compensation for almost 50% of the July measurement period. Observed patterns of the rates of water loss and of the moisture required to reach field capacity are correlated with the moisture status of the mosses in the field. Field measurements of photosynthetically active radiation (PAR) at the moss surface and above the forest canopy showed that the transmission of diffuse radiation through the forest canopy increased with increasing cloudiness. PAR at the moss surface was above the compensation level for photosynthesis with sunny and cloudy conditions. Sunflecks (short periods of direct sunlight), which had an intensity of about 76% of the radiation incident on the forest canopy, occurred on up to 35% of the ground surface and provided a major source of the radiation received. Species varied in their pattern of attenuation of light through the moss canopy. A mixed stand of P. commune and P. schreberi and stands of H. splendens transmit light deeply. Sphagnumsubsecundum, on the other hand, shows rapid attenuation of light high in the canopy. The observed pattern of light attenuation helps explain the vertical position of the green–brown interface and the death of green material in the moss canopy.

Carbon balance in relation to drying in four epiphytic mosses growing in different vertical ranges

1979 ◽  
Vol 57 (19) ◽  
pp. 1994-1998 ◽  
Author(s):  
Peter L. Tobiessen ◽  
Nancy G. Slack ◽  
Keith A. Mott
Keyword(s):  
Water Potential ◽  
Water Content ◽  
Carbon Balance ◽  
The Other ◽  
Moss Species ◽  
Relationship Of ◽  
The Relationship ◽  
Neckera Pennata ◽  
Lower Water Content ◽  
Photosynthesis And Respiration

The response of photosynthesis and respiration to drying was measured in four species of epiphytic mosses, Ulota crispa (Hedw.) Brid., Neckera pennata Hedw., Anomodon rugellii (C. Mull.) Keissl., and Plagiomnium cuspidatum (Hedw.) T. Kop., from habitats along a desiccation gradient. There was little difference among the mosses in these responses. The relationship of water content to water potential did differ among the mosses, with Plagiomnium, the facultative epiphyte, showing a typical response of more mesic species and the other three showing a more xeric response, i.e., water potential does not begin to fall steeply until a lower water content is reached in Ulota, Neckera, and Anomodon. Both photosynthesis and respiration in all four moss species were quite sensitive to moderate water stress.

scholarly journals Remotely Sensed Water Limitation in Vegetation: Insights from an Experiment with Unmanned Aerial Vehicles (UAVs)

2019 ◽  
Vol 11 (16) ◽  
pp. 1853 ◽  
Author(s):  
Kelly Easterday ◽  
Chippie Kislik ◽  
Todd Dawson ◽  
Sean Hogan ◽  
Maggi Kelly
Keyword(s):  
Unmanned Aerial Vehicles ◽  
Water Content ◽  
Water Deficit ◽  
Water Status ◽  
Field Measurements ◽  
Leaf Water Content ◽  
Multispectral Imagery ◽  
Spectral Indices ◽  
Aerial Vehicles ◽  
The Relationship

Unmanned aerial vehicles (UAVs) equipped with multispectral sensors present an opportunity to monitor vegetation with on-demand high spatial and temporal resolution. In this study we use multispectral imagery from quadcopter UAVs to monitor the progression of a water manipulation experiment on a common shrub, Baccharis pilularis (coyote brush) at the Blue Oak Ranch Reserve (BORR) ~20 km east of San Jose, California. We recorded multispectral imagery at several altitudes with nearly hourly intervals to explore the relationship between two common spectral indices, NDVI (normalized difference vegetation index) and NDRE (normalized difference red edge index), leaf water content and water potential as physiological metrics of plant water status, across a gradient of water deficit. An examination of the spatial and temporal thresholds at which water limitations were most detectable revealed that the best separation between levels of water deficit were at higher resolution (lower flying height), and in the morning (NDVI) and early morning (NDRE). We found that both measures were able to identify moisture deficit across treatments; however, NDVI was better able to distinguish between treatments than NDRE and was more positively correlated with field measurements of leaf water content. Finally, we explored how relationships between spectral indices and water status changed when the imagery was scaled to courser resolutions provided by satellite-based imagery (PlanetScope).We found that PlanetScope data was able to capture the overall trend in treatments but unable to capture subtle changes in water content. These kinds of experiments that evaluate the relationship between direct field measurements and UAV camera sensitivity are needed to enable translation of field-based physiology measurements to landscape or regional scales.

scholarly journals Close-range Hyperspectral Spectroscopy Reveals Leaf Water Content Dynamics

2021 ◽  
Author(s):  
Samuli Junttila ◽  
Teemu Hölttä ◽  
Ninni Saarinen ◽  
Ville Kankare ◽  
Tuomas Yrttimaa ◽  
...  
Keyword(s):  
Water Content ◽  
Field Measurements ◽  
Leaf Water ◽  
Leaf Water Content ◽  
Plant Responses ◽  
Continuous Change ◽  
Laboratory Findings ◽  
Equivalent Water Thickness ◽  
Close Range ◽  
Non Destructive

Water plays a crucial role in maintaining plant functionality and drives many ecophysiological processes. The distribution of water resources is in a continuous change due to global warming affecting the productivity of ecosystems around the globe, but there is a lack of non-destructive methods capable of continuous monitoring of plant and leaf water content that would help us in understanding the consequences of the redistribution of water. We studied the utilization of novel small hyperspectral sensors in the 1350-2450 nm spectral range in non-destructive estimation of leaf water content in laboratory and field conditions. We found that the sensors captured up to 96% of the variation in equivalent water thickness (EWT, g/m2) and up to 90% of the variation in relative water content (RWC). These laboratory findings were supported by field measurements, where repeated leaf spectra measurements were in good agreement (R2=0.79) with a time-lagged change of tree xylem diameter. Further tests were done with an indoor plant (Dracaena marginate Lem.) by continuously measuring leaf spectra while drought conditions developed, which revealed detailed diurnal dynamics of leaf water content. We conclude that close-range hyperspectral spectroscopy can provide a novel tool for continuous measurement of leaf water content at the single leaf level and help us to better understand plant responses to varying environmental conditions.

Studies of the tolerance of Atriplex species. 1. Environmental characteristics and plant response of A. vesicaria, A. nummularia and A. semibaccata

1967 ◽  
Vol 7 (24) ◽  
pp. 39 ◽  
Author(s):  
CT Gates ◽  
W Muirhead
Keyword(s):  
Plant Growth ◽  
Water Content ◽  
Leaf Water ◽  
The Other ◽  
Leaf Water Content ◽  
Seasonal Fluctuations ◽  
Adverse Conditions ◽  
Plant Life ◽  
Extremes Of Temperature ◽  
Seasonal Extremes

The effect of climate on the growth of three species of Atriplex viz., A. vesicaria Heward, A. nummdaria Lindl., and A. semibaccata R. Br., was measured for two years in the Riverine plains area of Australia. A single harvest of Kochia georgii R. Br, was also made. Plant life in the area is exposed to the stresses of wide diurnal and seasonal extremes of temperature and humidity and to low rainfall, with high actual evaporation and evapotranspiration rates during the summer. The plants also grow in soils that are highly saline with an unfavourable ratio of sodium to potassium contents. Despite these adverse conditions for plant growth the Atriplex species and Kochia georgii were well adapted and had high leaf weight ratios. The species were summer growers. A. semibaccata was dormant in the winter, but the other Atriplex species remained green and healthy, although they grew very little during the winter. The ratios of leaf to stem weights and the leaf water content showed seasonal fluctuations in the Atriplex species, but these were modified in accord with previous rainfall and evaporation rates. The remarkable capacity of Atriplex species to remain leafy and viable, under such adverse conditions, as were observed, is a major factor contributing to its pastoral importance in these inland areas.

scholarly journals Leaf water content estimation using top-of-canopy airborne hyperspectral data

2021 ◽  
Vol 102 ◽  
pp. 102393
Author(s):  
Rahul Raj ◽  
Jeffrey P. Walker ◽  
Vishal Vinod ◽  
Rohit Pingale ◽  
Balaji Naik ◽  
...  
Keyword(s):  
Water Content ◽  
Hyperspectral Data ◽  
Leaf Water ◽  
Leaf Water Content

scholarly journals Simulating Heat Stress of Coal Gangue Spontaneous Combustion on Vegetation Using Alfalfa Leaf Water Content Spectral Features as Indicators

2021 ◽  
Vol 13 (13) ◽  
pp. 2634
Author(s):  
Qiyuan Wang ◽  
Yanling Zhao ◽  
Feifei Yang ◽  
Tao Liu ◽  
Wu Xiao ◽  
...  
Keyword(s):  
Heat Stress ◽  
Water Content ◽  
Spontaneous Combustion ◽  
Leaf Water ◽  
Coal Gangue ◽  
Leaf Water Content ◽  
Spectral Features ◽  
Lasso Regression ◽  
Stress Assessment ◽  
First Derivative

Vegetation heat-stress assessment in the reclamation areas of coal gangue dumps is of great significance in controlling spontaneous combustion; through a temperature gradient experiment, we collected leaf spectra and water content data on alfalfa. We then obtained the optimal spectral features of appropriate leaf water content indicators through time series analysis, correlation analysis, and Lasso regression analysis. A spectral feature-based long short-term memory (SF-LSTM) model is proposed to estimate alfalfa’s heat stress level; the live fuel moisture content (LFMC) varies significantly with time and has high regularity. Correlation analysis of the raw spectrum, first-derivative spectrum, spectral reflectance indices, and leaf water content data shows that LFMC and spectral data were the most strongly correlated. Combined with Lasso regression analysis, the optimal spectral features were the first-derivative spectral value at 1661 nm (abbreviated as FDS (1661)), RVI (1525,1771), DVI (1412,740), and NDVI (1447,1803). When the classification strategies were divided into three categories and the time sequence length of the spectral features was set to five consecutive monitoring dates, the SF-LSTM model had the highest accuracy in estimating the heat stress level in alfalfa; the results provide an important theoretical basis and technical support for vegetation heat-stress assessment in coal gangue dump reclamation areas.

Shell Resistance and Evaporative Water Loss from Bird Eggs: Effects of Wind Speed and Egg Size

1981 ◽  
Vol 54 (2) ◽  
pp. 195-202 ◽  
Author(s):  
James R. Spotila ◽  
Christina J. Weinheimer ◽  
Charles V. Paganelli
Keyword(s):  
Wind Speed ◽  
Water Loss ◽  
Egg Size ◽  
Evaporative Water Loss ◽  
Evaporative Water ◽  
Bird Eggs

scholarly journals Accumulation of Silicon and Changes in Water Balance under Drought Stress in Brassica napus var. napus L.

Plants ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 280
Author(s):  
Diana Saja-Garbarz ◽  
Agnieszka Ostrowska ◽  
Katarzyna Kaczanowska ◽  
Franciszek Janowiak
Keyword(s):  
Abscisic Acid ◽  
Drought Stress ◽  
Stomatal Conductance ◽  
Water Balance ◽  
Water Content ◽  
Oilseed Rape ◽  
Potential Evapotranspiration ◽  
Leaf Water Content ◽  
Optimal Conditions ◽  
Abscisic Acid Level

The aim of this study was to investigate the accumulation of silicon in oilseed rape and to characterize the changes in chosen water balance parameters in response to drought. The following parameters were estimated: water content, osmotic and water potential, evapotranspiration, stomatal conductance and abscisic acid level under optimal and drought conditions. It was shown that oilseed rape plants accumulate silicon after its supplementation to the soil, both in the case of silicon alone and silicon together with iron. It was revealed that silicon (without iron) helps maintain constant water content under optimal conditions. While no silicon influence on osmotic regulation was observed, a transpiration decrease was detected under optimal conditions after silicon application. Under drought, a reduction in stomatal conductance was observed, but it was similar for all plants. The decrease in leaf water content under drought was accompanied by a significant increase in abscisic acid content in leaves of control plants and those treated with silicon together with iron. To sum up, under certain conditions, silicon is accumulated even in non-accumulator species, such as oilseed rape, and presumably improves water uptake under drought stress.

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