Dawn Water Potential and Root Depth of Trees and Understorey Species in Southwestern Australia

1988 ◽  
Vol 36 (6) ◽  
pp. 621 ◽  
Author(s):  
DS Crombie ◽  
JT Tippett ◽  
TC Hill
Keyword(s):  
Water Potential ◽  
Annual Rainfall ◽  
Soil Profiles ◽  
Seasonal Patterns ◽  
Summer Drought ◽  
Root Depth ◽  
Jarrah Forest ◽  
Southwestern Australia ◽  
Water Potentials ◽  
Average Annual Rainfall

Water relations of selected tree and understorey species in the jarrah forest of south-western Australia were studied during summer drought and the results related to root morphology. Seasonal patterns of predawn water potential (Ψp) differed between species according to root depth and between sites according to average annual rainfall. Dawn water potentials fell most rapidly and by the greatest amount in plants with the shallowest roots. Dawn water potentials of medium and deep rooted species were not consistently different. Separation of Ψp between sites of different annual rainfall was less marked than was separation by root depth. Changes in Ψp, were consistent with a top-to-bottom drying of the soil profiles. We suggest that measurements of Ψp of plants of appropriate root depth can be used to monitor the drying of soils as an alternative to more expensive mechanical and electrical methods.

Persistence and productivity of phalaris (Phalaris aquatica) germplasm in dry marginal rainfall environments of south-eastern Australia

2017 ◽  
Vol 68 (8) ◽  
pp. 781
Author(s):  
R. A. Culvenor ◽  
M. R. Norton ◽  
J. De Faveri
Keyword(s):  
Environmental Benefits ◽  
Annual Rainfall ◽  
Summer Drought ◽  
Environment Interaction ◽  
Phalaris Aquatica ◽  
Mixed Farming ◽  
Eastern Australia ◽  
Summer Dormancy ◽  
Average Annual Rainfall ◽  
Establishment Phase

Perennial grasses have production and environmental benefits in areas of southern Australia typified by the mixed farming zone of southern New South Wales (NSW). The perennial grass phalaris (Phalaris aquatica L.) is widely used in southern Australia; however, it would find more use in the mixed farming zone if its persistence in marginal rainfall areas (450–500 mm average annual rainfall) were improved. We evaluated a range of germplasm (n = 29) including wild accessions, lines bred from these, and existing cultivars for persistence and production at three sites in a summer-dry area of southern NSW with 430–460-mm average annual rainfall. Two sites were used over 4 years and the third site over 5 years. Summer dormancy, maturity time and seedling growth were also assessed. Analysis of genotype × environment interaction employing factor analytic models and accounting for spatial and temporal correlations indicated that changes in persistence occurred mainly over time rather than between sites. Ranking changes occurred in the dry establishment phase of the experiment and during a severe final summer drought, with few changes occurring in the intervening high-rainfall years. Lines that survived the establishment phase best had vigorous seedlings and earlier maturity, whereas those surviving the final summer best were earlier maturing and higher in summer dormancy with high winter-growth activity. Some later maturing lines within the higher summer dormancy group were less persistent. Some accessions from North Africa were the most persistent; also, populations bred from these and other more persistent accessions generally persisted and produced better than cultivars used presently. However, present cultivars were capable of high yield in the higher rainfall years. We suggest that persistence of higher summer dormancy cultivars over very dry years could be improved by selecting for earlier maturity time.

scholarly journals Analysis of phosphorus migration into soil profiles fertilized with struvite

2019 ◽  
Vol 86 ◽  
pp. 00033
Author(s):  
Małgorzata Worwąg ◽  
Jolanta Sobik-Szołtysek
Keyword(s):  
Soil Profile ◽  
Phosphorus Content ◽  
Soil Washing ◽  
Rainfall Amount ◽  
Monthly Rainfall ◽  
Annual Rainfall ◽  
Soil Profiles ◽  
Soil Mixture ◽  
Average Annual Rainfall ◽  
The City

The focus of the present study was on phosphorus migration into soil profile fertilized with struvite with various doses (0.0 g – control, 0.1 g, 0.5 g and 1.0 g). Lysimeter examinations were carried out in 3 columns which modelled 3 levels of soil washing (10, 20 and 30 cm) for each soil mixture with specific struvite doses. Each experiment consisted in flushing water through a column filled with a mixture, with an amount modelling the average annual rainfall for the area of the city of Czestochowa, Poland, adopted at the level of 650 mm. The tests were conducted for 12 days, with simulation of monthly rainfall performed on each day. The phosphorus content was analyzed in the leachate. It was found based on the results that the amount of leached phosphorus was directly connected with the struvite dose in the mixture. The highest phosphorus concentrations were observed at the level of 20 cm of the height of soil profile for the dose of 0.1 g struvite. In the case of the higher struvite doses, i.e. 1.0 g, the highest concentration was found for the height of 30 cm. A decline in concentration of the leached phosphorus was observed after the sixth sampling of the eluate, which resulted from leaching the soil profile with simulated annual rainfall amount.

Root Depth, Leaf Area and Daytime Water Relations of Jarrah (Eucalyptus marginata) Forest Overstorey and Understorey During Summer Drought

1992 ◽  
Vol 40 (2) ◽  
pp. 113 ◽  
Author(s):  
DS Crombie
Keyword(s):  
Stomatal Conductance ◽  
Leaf Area ◽  
Summer Drought ◽  
Root Depth ◽  
Jarrah Forest ◽  
Area Index ◽  
Eucalyptus Marginata ◽  
Water Deficits ◽  
Forest Sites ◽  
Understorey Plants

Foliage projective cover of trees on high and low rainfall jarrah forest sites was 1.6 and 1.2 times that of their understorey respectively. Corresponding leaf area index ratios were 7.2 and 3.4 times. Tree and understorey species developed substantial water deficits on both sites during the summer drought, although water deficits developed more rapidly and became more severe on the site receiving less rainfall. Stornatal conductances and midday water potentials of deeply rooted trees (root depth > 10m) remained higher than those of less deeply rooted understorey plants for 1-2 months in the absence of rain. Daily cycling of water potential and stomatal conductance was detected in most plants throughout the summer. This is interpreted as indicating that the plants did not become dormant during summer drought.

Differential effects of reduced water potential on the germination of floodplain grassland species indicative of wet and dry habitats

2014 ◽  
Vol 24 (1) ◽  
pp. 49-61 ◽  
Author(s):  
Kristin Ludewig ◽  
Bianka Zelle ◽  
R. Lutz Eckstein ◽  
Eva Mosner ◽  
Annette Otte ◽  
...  
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Potential Gradient ◽  
Water Level Fluctuations ◽  
Summer Drought ◽  
Climate Change Scenarios ◽  
Water Potentials ◽  
Floodplain Meadow ◽  
Reduced Water ◽  
Meadow Species

AbstractFloodplain meadow ecosystems are characterized by high water level fluctuations and highly variable soil water potentials. Additionally, climate change scenarios indicate an increasing risk for summer drought along the northern Upper Rhine and the Middle Elbe River, Germany. While adult plants often persist even after strong changes in water availability, early life phases, such as seed germination and seedling establishment, might be more vulnerable. Therefore we tested whether reduced soil water potentials will affect the germination of meadow species and whether the response varies between (1) forbs indicative of wet and dry habitats and (2) seeds originating from sites along the rivers Elbe and Rhine. We exposed seeds of 20 floodplain meadow species with different moisture requirements from five plant families to a water potential gradient ranging from 0 to − 1.5 MPa. While across species germination percentage and synchrony decreased, germination time increased at reduced water potentials. Germination of the species indicative of dry habitats decreased more strongly, was slower and less synchronous at reduced water potentials than that of species indicative of wet habitats. Seeds from sites along the rivers Elbe and Rhine did not differ in their germination characteristics. We propose that species of wet sites follow an all-or-nothing-strategy with fast and synchronous germination to maximize competitive advantages, betting on a high probability of moist conditions for establishment (optimists). In contrast, species from dry sites appear to follow a bet-hedging strategy with a moisture-sensing mechanism for unsuitable conditions (pessimists), resulting in a slower and less synchronous germination.

THE ROLE OF GRASSLAND IN MANAGEMENT

1968 ◽  
pp. 44-49
Author(s):  
B.K. Cameron
Keyword(s):  
Soil Temperature ◽  
Annual Rainfall ◽  
Silt Loam ◽  
Average Annual Rainfall ◽  
Very High ◽  
Wilting Point

THE PROPERTY to be discussed is a mixed sheep and cropping unit, situated ei ht a miles east of Ashburton and midway between the Ra aia and the Ashburton rivers. Average annual rainfall is 27 in., evenly spread, but there is very high summer evaporation and therefore frequent droughts. On average, the soil is below wilting point for 40 to 50 days each summer. Winters are cold with the soil temperature being below 48°F for about four months each year. The soil is a Lismore stony silt loam averaging 9 in. in depth over gravel.

NITROGEN TRANSFORMATIONS NEAR UREA IN SOIL WITH DIFFERENT WATER POTENTIALS

1988 ◽  
Vol 68 (3) ◽  
pp. 569-576 ◽  
Author(s):  
YADVINDER SINGH ◽  
E. G. BEAUCHAMP
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Incubation Period ◽  
Relative Rate ◽  
Soil Water Potential ◽  
Nitrification Inhibitor ◽  
Silt Loam ◽  
Nitrogen Transformations ◽  
Water Potentials ◽  
Initial Soil

Two laboratory incubation experiments were conducted to determine the effect of initial soil water potential on the transformation of urea in large granules to nitrite and nitrate. In the first experiment two soils varying in initial soil water potentials (− 70 and − 140 kPa) were incubated with 2 g urea granules with and without a nitrification inhibitor (dicyandiamide) at 15 °C for 35 d. Only a trace of [Formula: see text] accumulated in a Brookston clay (pH 6.0) during the transformation of urea in 2 g granules. Accumulation of [Formula: see text] was also small (4–6 μg N g−1) in Conestogo silt loam (pH 7.6). Incorporation of dicyandiamide (DCD) into the urea granule at 50 g kg−1 urea significantly reduced the accumulation of [Formula: see text] in this soil. The relative rate of nitrification in the absence of DCD at −140 kPa water potential was 63.5% of that at −70 kPa (average of two soils). DCD reduced the nitrification of urea in 2 g granules by 85% during the 35-d period. In the second experiment a uniform layer of 2 g urea was placed in the center of 20-cm-long cores of Conestogo silt loam with three initial water potentials (−35, −60 and −120 kPa) and the soil was incubated at 15 °C for 45 d. The rate of urea hydrolysis was lowest at −120 kPa and greatest at −35 kPa. Soil pH in the vicinity of the urea layer increased from 7.6 to 9.1 and [Formula: see text] concentration was greater than 3000 μg g−1 soil. There were no significant differences in pH or [Formula: see text] concentration with the three soil water potential treatments at the 10th day of the incubation period. But, in the latter part of the incubation period, pH and [Formula: see text] concentration decreased with increasing soil water potential due to a higher rate of nitrification. Diffusion of various N species including [Formula: see text] was probably greater with the highest water potential treatment. Only small quantities of [Formula: see text] accumulated during nitrification of urea – N. Nitrification of urea increased with increasing water potential. After 35 d of incubation, 19.3, 15.4 and 8.9% of the applied urea had apparently nitrified at −35, −60 and −120 kPa, respectively. Nitrifier activity was completely inhibited in the 0- to 2-cm zone near the urea layer for 35 days. Nitrifier activity increased from an initial level of 8.5 to 73 μg [Formula: see text] in the 3- to 7-cm zone over the 35-d period. Nitrifier activity also increased with increasing soil water potential. Key words: Urea transformation, nitrification, water potential, large granules, nitrifier activity, [Formula: see text] production

Photosynthesis Response of Sunlit and Shade Pepper (Capsicum annuum) Leaves at Different Positions in the Canopy Under Two Water Regimes

1994 ◽  
Vol 21 (3) ◽  
pp. 377 ◽  
Author(s):  
A Alvino ◽  
M Centritto ◽  
FD Lorenzi
Keyword(s):  
Water Potential ◽  
Capsicum Annuum ◽  
Leaf Water Potential ◽  
Co2 Exchange ◽  
Leaf Water ◽  
Predawn Leaf Water Potential ◽  
Water Regimes ◽  
Water Potentials ◽  
Sun And Shade ◽  
Shade Leaves

Pepper (Capsicum annuum L.) plants were grown in 1 m2 lysimeters under two different water regimes in order to investigate differences in the spatial arrangements of the leaves and to relate this to daily assimilation rates of leaves of the canopy. The control regime (well-watered (W) treatment) was irrigated whenever the accumulated 'A' pan evaporation reached 4 cm, whereas the water-stressed (S) treatment was watered whenever the predawn leaf water potential fell below -1 MPa. During the growing cycle, equal numbers of sun and shade leaves were chosen from the apical, middle and basal parts of the canopy, corresponding to groups of leaves of increasing age. The CO2 exchange rate (CER) was measured at 0830, 1230 and 1530 hours on 8 days along the crop cycle, on leaves in their natural inclination and orientation. Leaf water potentials were measured on apical leaves before dawn and concurrently with gas exchange measurements. Control plants maintained predawn leaf water potential at -0.3 MPa, but S plants reached values lower than -1.2 MPa. Midday leaf water potentials were about twice as low in the S plants as in the controls. Water stress reduced LA1 during the period of crop growth, and dry matter production at harvest. Stressed apical leaves appeared to reduce stress by changing their inclination. They were paraheliotropic around midday and diaheliotropic at 0830 and 1530 hours. The CER values of the S treatment were significantly lower than those of the W treatment in apical and middle leaves, whereas the CER of basal leaves did not differ in either treatments. In the S treatment, reduction in the CER values of sunlit apical leaves was more evident in the afternoon than at midday or early in the morning, whereas basal leaves were less affected by water than basal stress leaves if sunlit, and negligibly in shaded conditions.

Wind blown sediment mass budget of Sahelian village land units in Niger

2001 ◽  
Vol 172 (5) ◽  
pp. 523-531 ◽  
Author(s):  
Jean-Louis Rajot
Keyword(s):  
Wind Erosion ◽  
Size Range ◽  
Arable Land ◽  
Annual Rainfall ◽  
Complete Disappearance ◽  
Mass Budget ◽  
Sediment Mass ◽  
Aeolian Sediments ◽  
Average Annual Rainfall ◽  
The Village

Abstract To assess the mass budget of aeolian sediments transported by wind (erosion vs. deposition) at the scale of village land units (25 kmX25 km), measurements were carried out during 3 years (from 1996 to 1998) in a cultivated field and in a fallow area simultaneously. These were located in the Sahelian zone of Niger with an average annual rainfall of 560 mm. The vertical upward fluxes of particles <20 mu m exported from the study area were estimated from the horizontal sediment fluxes measured using BSNE sand catchers. This mass of exported dust was compared with the vertical downward fluxes of particles of the same size range (<20 mu m) measured using passive CAPYR collectors. Values of deposition recorded in the field and in the fallow were similar. In the field, wind erosion reached its maximum in May and June when the vegetation cover was minimal. In the fallow area, wind erosion was always very low in comparison with the field. It occurred during the strongest storms when the grass cover was minimal. Nevertheless, the net balance between deposition and erosion was highly positive in the fallow areas. These results have been extrapolated at the scale of the village land units based on the current land use. At this scale, the balance was positive for the arable land, indicating a net deposition of aeolian sediments of +0.36 t ha (super -1) yr (super -1) . However, the complete disappearance of fallow land would result in a balanced budget for the arable land.

scholarly journals Drought reduced monoterpene emissions from the evergreen Mediterranean oak <i>Quercus ilex</i>: results from a throughfall displacement experiment

2009 ◽  
Vol 6 (7) ◽  
pp. 1167-1180 ◽  
Author(s):  
A.-V. Lavoir ◽  
M. Staudt ◽  
J. P. Schnitzler ◽  
D. Landais ◽  
F. Massol ◽  
...  
Keyword(s):  
Water Potential ◽  
Leaf Water Potential ◽  
Quercus Ilex ◽  
Photochemical Efficiency ◽  
Leaf Water ◽  
Control Treatment ◽  
Summer Drought ◽  
Drought Period ◽  
Significant Difference ◽  
Monoterpene Emission

Abstract. The effects of water limitations on the emission of biogenic volatile organic compounds are not well understood. Experimental approaches studying drought effects in natural conditions are still missing. To address this question, a throughfall displacement experiment was set up in a natural forest of Quercus ilex, an evergreen Mediterranean oak emitting monoterpenes. Mature trees were exposed in 2005 and 2006 either to an additional drought, to irrigation or to natural drought (untreated control). In both years, absolute monoterpene emission rates as well as the respective standard factors of the trees exposed to normal and additional drought strongly declined during the drought periods. Monoterpene emissions were lower in year 2006 than in year 2005 (factor 2) due to a more pronounced summer drought period in this respective year. We observed a significant difference between the irrigation and additional drought or control treatment: irrigated trees emitted 82% more monoterpenes during the drought period 2006 than the trees of the other treatments. However, no significant effect on monoterpene emission was observed between normal and additional drought treatments, despite a significant effect on leaf water potential and photochemical efficiency. During the development of drought, monoterpene emissions responded exponentially rather than linearly to decreasing leaf water potential. Emissions rapidly declined when the water potential dropped below −2 MPa and photosynthesis was persistently inhibited. Monoterpene synthase activities measured in vitro showed no clear reduction during the same period. From our results we conclude that drought significantly reduces monoterpene fluxes of Mediterranean Holm oak forest into the atmosphere due to a lack of primary substrates coming from photosynthetic processes.

scholarly journals NATURAL PLANT SPECIES INVENTORY OF THE IMPORTANT PLANT AREAS IN ARABIAN PENINSULA: BANI OMAR, TAIZ GOVERNORATE, REPUBLIC OF YEMEN

2020 ◽  
Vol 1 (3) ◽  
pp. 135-150
Author(s):  
Abdul Wali Ahmed Al-Khulaidi ◽  
Abdul Habib Al-Qadasi ◽  
Othman Saad Saeed Al-Hawshabi
Keyword(s):  
Plant Species ◽  
Arabian Peninsula ◽  
Annual Rainfall ◽  
Vegetation Types ◽  
Salvadora Persica ◽  
Natural Plant ◽  
Vegetation Communities ◽  
Ecological Zones ◽  
Average Annual Rainfall ◽  
Semi Arid

The study area is located on the South western mountains of Republic of Yemen, It is characterized by arid and semi-arid climate with high temperatures and low average annual rainfall. The aims of this study are to explore the natural plant species of one of the Important Plant areas of Arabian Peninsula and to evaluate the chance to be a protected area. 61 sample sites covering the whole ecological zones haven been conducted. 135 plant species are found, in which 3 plant species were endemic, 7 near endemic, 29 regional endemic. The study revealed also three vegetation communities with 7 vegetation associations (vegetation types). Vegetation dominated by Ficus cordata, F. sycomorus, Salvadora persica Tamarix aphylla and Ziziphus spina-christi were found on main wadis. Vegetation communities dominated by Acacia asak, Anisotes trisulcus, Jatropha variegate and Zygocarpum yemenense were found on rocky slopes and stony plateau.

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