Hydrological processes and herbage production in shrub invaded Poplar Box (Eucalyptus populnea) woodlands.

1981 ◽  
Vol 3 (1) ◽  
pp. 45 ◽  
Author(s):  
GG Johns
Keyword(s):  
Soil Water ◽  
Water Storage ◽  
Free Water ◽  
Bare Soil ◽  
Hydrological Processes ◽  
Soil Water Storage ◽  
Water Losses ◽  
Run Off ◽  
Annual Distribution ◽  
Trees And Shrubs

The hydrological processes of relevance to herbage production in shrub invaded semi-arid popla box (Eucalvptus popuhea) woodlands are reviewed. Climatic limitations to herbage production in the poplar box lands are discussed in relation to the annual distribution of rainfall and evaporation. The limiting effects of trees and shrubs on herbage production within a woodland are then evaluated using data from a study site near Coolabah in north-western New South Wales. Hydrologic measurements made at the site include soil water storage, run-off and infiltration rates. Marked spatial variability in infiltration of water into the soil was in part related to the distribution of plants and redistribu- tion of water from ridges to adjacent flats occurred because of low rates of infiltration into bare soil areas between groups of trees and shrubs. From measurements of the depletion of soil water which accumulated during an exceptionally wet period the potential rate of evapotranspiration from the poplar box component of the woodland was estimated to be 0.5 times that from a free water surface. Bare soil evaporation accounted for approximately one half of water losses. Herbage production is shown to be poorly related to soil water storage alone, but the regression between herbage production and the product of water and nitrogen availabilities accounts for 70% of the vari~ce. It is concluded that the role of trees and shrubs in competing with herbage for nutrients, as well as water, is in need of clarification.

Accuracy of the neutron probe for measuring changes in soil water storage under potatoes

2002 ◽  
Vol 138 (2) ◽  
pp. 135-152 ◽  
Author(s):  
S. R. GAZE ◽  
M. A. STALHAM ◽  
E. J. ALLEN
Keyword(s):  
Field Experiment ◽  
Soil Water ◽  
Water Storage ◽  
Surface Profile ◽  
Soil Surface ◽  
Bare Soil ◽  
Irrigation Scheduling ◽  
Soil Water Storage ◽  
Neutron Probe ◽  
Areal Sampling

The neutron probe (NP) is used widely to measure changes in soil water storage in research and more recently to aid irrigation scheduling. Its accuracy is rarely questioned and most of the relationships between soil water changes and productivity are based on its use. A field experiment was conducted at Cambridge University Farm in 1999 to address whether the NP could accurately measure changes in soil water content (SWC) under irrigation or substantial rain (>10 mm). The experiment was a replicated split-plot design with four irrigation treatments allocated to the main plots, and surface profile (ridge, flat) and crop (potato cv. Saturna, bare soil) treatments allocated to the subplots. The mean results from four NP access tubes per plot installed to measure soil moisture deficit (SMD) across the row-width were analysed. The NP was inconsistent in measuring known irrigation or rainfall input. In relatively dry soil (SMD>40 mm), the NP generally measured 93 to 110% of 18 mm of irrigation within 4 h of irrigation. The NP recorded much less water applied as irrigation in wetter soil, and often only 40 to 70% of the applied irrigation (18 or 36 mm) was measured. There were occasions when the NP did not measure all the water input even when the SMDs before irrigation were greater than the water subsequently applied. Some of the ‘missing’ water might be attributed to drainage, however, results from an additional experiment using an open-topped tank of soil showed that the NP was unable to detect all the water added to the soil, particularly where the water was largely confined close to the soil surface. Replicated measurements of the change in SMD in the field experiment were precise for a given event and treatment (mean S.E. = 1·3 mm) but were not accurate when compared against the input measured in rain gauges. It was concluded, that the NP could not be used reliably to measure changes in soil water storage after irrigation or substantial rain. For periods when there were minimal inputs of water, there was a closer correlation between changes in SMD measured by the NP and those predicted by a modified Penman–Monteith equation than after substantial inputs of water. However, for predicted changes in SMD of c. 20 mm, there was a range of c. ±5 mm in the changes in SMD measured by the neutron probe.The value of the NP for monitoring SMDs where there is irrigation, or substantial rain, must be seriously doubted. Consequently, its limitations for scheduling irrigation, testing models or quantifying the effects of treatments on crop water use in potatoes must be appreciated, especially where the areal sampling limitations of single access tubes positioned only in the ridge centre have not been addressed.

scholarly journals Mudanças no Uso da Terra e Efeito nos Componentes do Balanço Hídrico no Agreste Pernambucano

2020 ◽  
Vol 13 (2) ◽  
pp. 870
Author(s):  
Thyago Rodrigues do Carmo Brito ◽  
José Romualdo De Sousa Lima ◽  
Cássio Lopes de Oliveira ◽  
Rodolfo Marcondes Silva Souza ◽  
Antonio Celso Dantas Antonino ◽  
...  
Keyword(s):  
Land Use ◽  
Water Balance ◽  
Soil Water ◽  
Capillary Rise ◽  
Land Use Changes ◽  
Water Storage ◽  
Soil Water Storage ◽  
Water Balance Components ◽  
Water Losses ◽  
Regional Land

As mudanças no uso da terra podem provocar alterações no regime hídrico de várias regiões do mundo. Na região agreste de Pernambuco, essas mudanças consistem, principalmente, na retirada da Caatinga para a implantação de pastagens e culturas agrícolas. Contudo, pouco se sabe sobre o efeito dessas mudanças nos componentes do balanço hídrico. Desse modo, o objetivo do presente trabalho foi avaliar o efeito da conversão de áreas de Caatinga em áreas de pastagem nos componentes do balanço hídrico. Para isso, foram medidos, simultaneamente, o armazenamento de água no solo, os fluxos de água (drenagem e/ou ascensão capilar), o escoamento superficial e a evapotranspiração (ET) durante o período de 24 meses (outubro de 2013 a setembro de 2015), pela metodologia do balanço hídrico no solo, em áreas de Caatinga e de pastagem no município de São João-PE. Verificou-se que o armazenamento de água no solo na Caatinga foi menor que na pastagem, devido ao maior dossel e sistema radicular da Caatinga. As perdas de água por drenagem totalizaram -103,9 mm na pastagem e foram nulas na Caatinga. Em ambas as áreas a ET foi proporcional a precipitação pluvial. totalizando 1.195,6 mm com média de 1,64 mm d-1 na Caatinga e na pastagem totalizou 1.087,4 mm e 1,49 mm d-1. Conclui-se que as mudanças no uso da terra (retirada da Caatinga e implantação de pastagem) resultaram em aumento das perdas de água por drenagem e redução da evapotranspiração, que pode causar impacto no clima regional. Land Use Changes and Effects on the Water Balance Components in Agreste Pernambucano A B S T R A C TLand use changes can cause alterations in water regime in various regions of the world. In the Agreste region of Pernambuco, these changes consist mainly of the removal of Caatinga for the implantation of grassland and crops. However, little is known about the effect of these changes on water balance components. Thus, the objective of the present study was to evaluate the effect of the conversion of Caatinga areas into grassland in the water balance components. For this, we measured simultaneously the soil water storage, water fluxes (drainage and / or capillary rise), runoff and evapotranspiration (ET) over a 24-month period (October 2013 to September 2015), by the soil water balance method in Caatinga and grassland areas in São João-PE. It was found that the soil water storage in Caatinga was lower than in the grassland, due to the higher canopy and root system of the Caatinga. Water losses, via drainage, totaled -103.9 mm in the grassland and were zero in the Caatinga. In both areas, ET was proportional to rainfall, totaling 1,195.6 mm with an average of 1.64 mm d-1 in the Caatinga and in the grassland totaled 1,087.4 mm and 1.49 mm d-1. It concludes that land use changes (i.e., the conversion of Caatinga areas into grassland) resulted in increased losses of drainage and reduced evapotranspiration, which can impact on regional climate.Key words: Caatinga; grassland; evapotranspiration; soil water content.

Soil water storage in a semi-arid Eucalyptus populnea woodland invaded by woody shrubs, and the effects of shrub clearing and tree ringbarking.

1984 ◽  
Vol 6 (2) ◽  
pp. 75 ◽  
Author(s):  
GG Johns
Keyword(s):  
Soil Water ◽  
Water Storage ◽  
Soil Surface ◽  
Bare Soil ◽  
Arid Environment ◽  
Soil Water Storage ◽  
Water Response ◽  
Shrub Clearing ◽  
Eucalyptus Populnea ◽  
Semi Arid

Soil water was monitored over a six year period in an intact shrub invaded semi-arid Elrcalyptlts popztlrlea woodland (control) and on areas which had been treated by either shrub-clearing, or by ringbarking of trees and shrub-clearing. Measurements were made under both the shrubby thicket areas near the eucalypt, and the sparsely shrubbed interthicket areas more distant from the trees. Average soil water storage over the six years for all treatments was only 26 nun. Much of this water was stored in the upper 500 Inm of the profile and hence was susceptible to direct evaporation from the usually bare soil surface. In the intact n.oodland and following wet weather, significantly more soil water was stored under thickets than under the interthicket areas. With the return of dry weather this cxtra soil water was rapidly depleted, and thicket soils would often become drier than interthicket soils. After pro- longed dry weather, soil matric potentials of - 10 to -1 2 MPa were recorded at a depth of 500 mm. Matric potentials by this time were least negative under thickets. Shrub clearing without rinpbarking increased thicket and interthicket soil water storage by 17% and 2396 respectively. The ring- barking and shrub clearing treatment increased thicket profile storage more than that of the interthicket (81% and 64% respectively). The effect of ringbarkinp lvas often pronounced at a distance of 25 rn from the tree. The contrasting soil water response to the two treatments indicated that in this semi-arid environment only a relatively srnaU change in soil water balance may accrue from incomplete clearing. The ren~oval of both shrubs and trees is probably necessary to make a large difference to soil water storage.

Herbage Production Following Rainfall Redistribution in a Semi-Arid Mulga (Acacia Aneura) Woodland in Western New South Wales.

1998 ◽  
Vol 20 (2) ◽  
pp. 206 ◽  
Author(s):  
JC Noble ◽  
RSB Greene ◽  
WJ Muller
Keyword(s):  
Soil Water ◽  
New South ◽  
Water Storage ◽  
Rainfall Event ◽  
Soil Water Storage ◽  
Stocking Rate ◽  
South Wales ◽  
Run Off ◽  
Acacia Aneura ◽  
Semi Arid

The effects of stocking rate (nominally ranging from 0.3 up to 0.8 dry sheep equivalents per ha) on rainfall redistribution, soil-water storage and herbage production were studied in three contiguous geomorphic zones (run-off, interception and run-on zones) in a semi-arid mulga (Acacia aneura) woodland in western New South Wales. The amount of rainfall redistribution increased directly with rainfall but there was no significant effect of stocking rate on the amount of soil-water stored in various zones. while soil-water storage differed little between zones following a minor rainfall event (11.9 mm), it was significantly higher (P < 0.001) in the run-on zone following a major rainfall event (42.7 mm). The interception zone was by far the most productive herbage zone contributing a significantly (P < 0.01) disproportionate amount of forage (c. 90% of total paddock production at low stocking rates) despite this zone only occupying a relatively small proportion (c. 12%) of landscape catenae. Herbage in the interception zone principally comprised palatable C3 perennial grasses such as Thyridolepis mitchelliana (mulga grass) and Monachather paradoxa (bandicoot grass). Experimental manipulation confirmed the fundamental importance of rainfall redistribution as a landscape process mediating herbage production in these semi-arid plant communities. Dry matter production by Eragrostis eriopoda (woollybutt) was significantly enhanced (P < 0.05) in the run-off zone when incident rainfall was retained in situ by metal barriers. Conversely, production by Thyridolepis mitchelliana in the lower interception zone was significantly depressed (P < 0.01) where similar barriers prevented access by overland flow. The results are discussed in the context of developing conservative management strategies designed to maintain effective landscape processes in these extensive ecosystems.

scholarly journals Regression Models for Soil Water Storage Estimation Using the ESA CCI Satellite Soil Moisture Product: A Case Study in Northeast Portugal

Water ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 37
Author(s):  
Tomás de Figueiredo ◽  
Ana Caroline Royer ◽  
Felícia Fonseca ◽  
Fabiana Costa de Araújo Schütz ◽  
Zulimar Hernández
Keyword(s):  
Soil Moisture ◽  
Soil Water ◽  
Regression Models ◽  
Meteorological Data ◽  
Water Storage ◽  
Model Performance ◽  
Soil Water Balance ◽  
Soil Water Storage ◽  
The Relationship

The European Space Agency Climate Change Initiative Soil Moisture (ESA CCI SM) product provides soil moisture estimates from radar satellite data with a daily temporal resolution. Despite validation exercises with ground data that have been performed since the product’s launch, SM has not yet been consistently related to soil water storage, which is a key step for its application for prediction purposes. This study aimed to analyse the relationship between soil water storage (S), which was obtained from soil water balance computations with ground meteorological data, and soil moisture, which was obtained from radar data, as affected by soil water storage capacity (Smax). As a case study, a 14-year monthly series of soil water storage, produced via soil water balance computations using ground meteorological data from northeast Portugal and Smax from 25 mm to 150 mm, were matched with the corresponding monthly averaged SM product. Linear (I) and logistic (II) regression models relating S with SM were compared. Model performance (r2 in the 0.8–0.9 range) varied non-monotonically with Smax, with it being the highest at an Smax of 50 mm. The logistic model (II) performed better than the linear model (I) in the lower range of Smax. Improvements in model performance obtained with segregation of the data series in two subsets, representing soil water recharge and depletion phases throughout the year, outlined the hysteresis in the relationship between S and SM.

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