Physical properties of two-component growth media based on Sphagnum peat and their implications for plant-available water and aeration

1995 ◽  
Vol 172 (1) ◽  
pp. 45-54 ◽  
Author(s):  
J. Heiskanen
Keyword(s):  
Physical Properties ◽  
Growth Media ◽  
Sphagnum Peat ◽  
Available Water ◽  
Two Component ◽  
Plant Available Water

scholarly journals Impacts of extreme precipitation and seasonal changes in precipitation on plants

2014 ◽  
Vol 11 (11) ◽  
pp. 3083-3093 ◽  
Author(s):  
M. J. B. Zeppel ◽  
J. V. Wilks ◽  
J. D. Lewis
Keyword(s):  
Extreme Precipitation ◽  
Seasonal Changes ◽  
Net Primary Productivity ◽  
Hydrological Cycle ◽  
Aridity Index ◽  
Summer Precipitation ◽  
Negative Effects ◽  
Available Water ◽  
Key Factor ◽  
Plant Available Water

Abstract. The global hydrological cycle is predicted to become more intense in future climates, with both larger precipitation events and longer times between events in some regions. Redistribution of precipitation may occur both within and across seasons, and the resulting wide fluctuations in soil water content (SWC) may dramatically affect plants. Though these responses remain poorly understood, recent research in this emerging field suggests the effects of redistributed precipitation may differ from predictions based on previous drought studies. We review available studies on both extreme precipitation (redistribution within seasons) and seasonal changes in precipitation (redistribution across seasons) on grasslands and forests. Extreme precipitation differentially affected above-ground net primary productivity (ANPP), depending on whether extreme precipitation led to increased or decreased SWC, which differed based on the current precipitation and aridity index of the site. Specifically, studies to date reported that extreme precipitation decreased ANPP in mesic sites, but, conversely, increased ANPP in xeric sites, suggesting that plant-available water is a key factor driving responses to extreme precipitation. Similarly, the effects of seasonal changes in precipitation on ANPP, phenology, and leaf and fruit development varied with the effect on SWC. Reductions in spring or summer generally had negative effects on plants, associated with reduced SWC, while subsequent reductions in autumn or winter had little effect on SWC or plants. Similarly, increased summer precipitation had a more dramatic impact on plants than winter increases in precipitation. The patterns of response suggest xeric biomes may respond positively to extreme precipitation, while comparatively mesic biomes may be more likely to be negatively affected. Moreover, seasonal changes in precipitation during warm or dry seasons may have larger effects than changes during cool or wet seasons. Accordingly, responses to redistributed precipitation will involve a complex interplay between plant-available water, plant functional type and resultant influences on plant phenology, growth and water relations. These results highlight the need for experiments across a range of soil types and plant functional types, critical for predicting future vegetation responses to future climates.

scholarly journals Exogenous Abscisic Acid Application Effects on Stomatal Closure, Water Use, and Shelf Life of Hydrangea (Hydrangea macrophylla)

2009 ◽  
Vol 27 (4) ◽  
pp. 234-238 ◽  
Author(s):  
Marc W. van Iersel ◽  
Kate Seader ◽  
Sue Dove
Keyword(s):  
Abscisic Acid ◽  
Shelf Life ◽  
Water Uptake ◽  
Stomatal Closure ◽  
Ornamental Plants ◽  
Detectable Effect ◽  
Water Control ◽  
Available Water ◽  
Hydrangea Macrophylla ◽  
Plant Available Water

Abstract A lack of adequate watering reduces the shelf life of many ornamental plants during retail. Our goals were to determine whether sprays or drenches with abscisic acid (ABA) can reduce transpiration and extend the shelf life of hydrangea (Hydrangea macrophylla). During the first 5 days after treatment, ABA drenches of 125 to 1000 ppm reduced stomatal conductance (gs) by 50 to 80% as compared to water. ABA-induced stomatal closure reduced plant water uptake from the substrate; control plants took up half of the plant-available water during the first 7 days after treatment, while it took 14 days for plants drenched with 1000 ppm to take up half of the available water. Control plants wilted after 12 days and time to wilting of drenched plants increased with increasing ABA concentrations, up to 23 days in the 1000 ppm treatment. Spray treatments had little effect on gs and no detectable effect on water uptake or time to wilting. Some yellowing of older leaves was seen with ABA drenches of 500 or 1000 ppm. Despite this side effect, ABA drenches have potential to extend the shelf life of hydrangeas in retail environments.

scholarly journals Impacts of reindeer grazing on soil properties on Finnmarksvidda, northern Norway

Rangifer ◽  
2004 ◽  
pp. 83-91 ◽  
Author(s):  
Christian Uhlig ◽  
Tore E. Sveistrup ◽  
Ivar Schjelderup
Keyword(s):  
Soil Fertility ◽  
Soil Properties ◽  
Plant Cover ◽  
Grazing Intensity ◽  
Organic Layer ◽  
Organic C ◽  
Northern Norway ◽  
Available Water ◽  
Lichen Cover ◽  
Plant Available Water

Numerous investigations have documented changes in vegetation due to reindeer grazing in Finnmark County, Northern Norway. However, rather few studies have focused on impacts of reindeer grazing on soil properties. The aim of this investigation was to identify possible changes in physical and chemical soil properties due to reindeer grazing. Furthermore, root distribution was detected. At four different locations on Finnmarksvidda three sample sites each were selected subjectively according to lichen and plant cover: A) ample, B) reduced, and C) poor lichen and plant cover. It was supposed that differences in lichen and plant cover were due to differences in reindeer grazing intensity. Results showed that the organic layer beneath ample lichen cover had an about 20% higher CEC and a 30—50% higher concentration of plant available Ca and Mg and total Mg compared to those beneath reduced ones. At sites with poor lichen and plant cover, an organic layer was mostly missing. The exposed mineral Eh-horizons at these sites had a significant (P<0.05) higher organic C content, higher CEC, concentrations of total P, Ca and K, and plant available K, when compared to E-horizons beneath better lichen covers. Rooting depth and amounts of plant available water in the rooting zone were lower at sites with reduced and poor lichen cover. A relation was found between soil organic C and CEC for all soil samples, indicating that soil organic matter is an essential key factor for soil fertility at the investigate sites on Finnmarksvidda. Assuming that differences in lichen and plant cover are related to differences in grazing intensity, results indicate that overgrazing by reindeers can cause a significant degradation of the organic layer, followed by significant losses of essential plant nutrients, a reduction in plant available water and consequently soil fertility.

scholarly journals A local description of dark energy in terms of classical two-component massive spin-one uncharged fields on spacetimes with torsionful affinities

Open Physics ◽  
2015 ◽  
Vol 13 (1) ◽  
Author(s):  
Jorge G. Cardoso
Keyword(s):  
Dark Energy ◽  
Physical Properties ◽  
Gauge Group ◽  
Wave Equations ◽  
Wave Functions ◽  
Local Description ◽  
Massive Spin ◽  
Two Component ◽  
Curved Spacetimes ◽  
Component Spinor

AbstractIt is assumed that the two-component spinor formalisms for curved spacetimes that are endowed with torsionful affine connexions can supply a local description of dark energy in terms of classical massive spin-one uncharged fields. The relevant wave functions are related to torsional affine potentials which bear invariance under the action of the generalized Weyl gauge group. Such potentials are thus taken to carry an observable character and emerge from contracted spin affinities whose patterns are chosen in a suitable way. New covariant calculational techniques are then developed towards deriving explicitly the wave equations that supposedly control the propagation in spacetime of the dark energy background. What immediately comes out of this derivation is a presumably natural display of interactions between the fields and both spin torsion and curvatures. The physical properties that may arise directly fromthe solutions to thewave equations are not brought out.

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