scholarly journals Effects of drought – altered seasonality and low rainfall – in net ecosystem carbon exchange of three contrasting Mediterranean ecosystems

2007 ◽  
Vol 4 (3) ◽  
pp. 1703-1736 ◽  
Author(s):  
J. S. Pereira ◽  
J. A. Mateus ◽  
L. M. Aires ◽  
G. Pita ◽  
C. Pio ◽  
...  
Keyword(s):  
Soil Water ◽  
Tree Cover ◽  
Annual Rainfall ◽  
Oak Woodland ◽  
Water Deficits ◽  
Eucalypt Plantation ◽  
Use Efficiency ◽  
Rain Use Efficiency ◽  
Soil Water Resources

Abstract. Droughts cause reductions in gross primary production (GPP) and also in net ecosystem exchange (NEE), contributing to most of the inter-annual variability in terrestrial carbon sequestration. In seasonally dry climates (Mediterranean) droughts result from reductions in annual rainfall and from changes in rain seasonality. In western Iberia, the hydrological-year (i.e., from October to September) of 2004–2005 was extremely dry, with precipitation 50% below the long-term mean (691 mm in 1961–1990), but 2005–2006 was normal. We compared the carbon fluxes measured by the eddy covariance technique from three contrasting ecosystems in southern Portugal: an evergreen oak woodland (savannah-like) with ca. 21% tree cover; a Mediterranean C3/C4 grassland; and a coppiced eucalyptus plantation. During the dry hydrological-year of 2004–2005, NEE was lowest, the highest sink strength was in the eucalypt plantation (NEE = –399 g C m −2 year−1) as compared to the oak woodland (NEE = –88 g C m −2 year−1), and the grassland (NEE = +49 g C m −2 year −1). The latter was a source of carbon dioxide. The NEE values of the dry year were, however, much lower than those for wetter years, e.g. NEE = –861 g C m−2 year −1 in 2002–2003 in the eucalypt plantation. The NEE of the grassland and the oak savannah in the 2005–2006 hydrological-year, with annual precipitation above the long term mean, were –190 and –120 g C m −2 year−1, respectively. All ecosystems studied increased their rain-use efficiency (GPP per unit of rain volume) increased in dry years. In the case of annual vegetation – grassland and low tree density woodland, however &ndash, rain-use efficiency decreased with severe drought. However, this was more pronounced in the eucalypt plantation due to greater GPP and the use of deep soil water resources. Although both calendar years of 2004 and 2005 had equally low rainfall, the effect of drought on the eucalypt plantation was delayed until the second dry year. This suggests that the effects of water deficits on Mediterranean forests are exacerbated by prolonged droughts when long-term soil water reserves are depleted. The grassland, however, was more vulnerable and responded faster to water deficits. This effect of drought was less pronounced in the oak woodland due to the sparse tree cover.

scholarly journals Soil water cycle and crop water use efficiency after long-term nitrogen fertilization in Loess Plateau

2012 ◽  
Vol 59 (No. 1) ◽  
pp. 1-7 ◽  
Author(s):  
B. Wang ◽  
W. Liu ◽  
Q. Xue ◽  
T. Dang ◽  
C. Gao ◽  
...  
Keyword(s):  
Water Use Efficiency ◽  
Soil Water ◽  
Water Use ◽  
Water Cycle ◽  
Triticum Aestivum L ◽  
Growing Seasons ◽  
Water Recharge ◽  
Use Efficiency ◽  
N Management

The objective of this study was to investigate the effect of nitrogen (N) management on soil water recharge, available soil water at sowing (ASWS), soil water depletion, and wheat (Triticum aestivum L.) yield and water use efficiency (WUE) after long-term fertilization. We collected data from 2 experiments in 2 growing seasons. Treatments varied from no fertilization (CK), single N or phosphorus (P), N and P (NP), to NP plus manure (NPM). Comparing to CK and single N or P treatments, NP and NPM reduced rainfall infiltration depth by 20–60 cm, increased water recharge by 16–21 mm, and decreased ASWS by 89–133 mm in 0–300 cm profile. However, crop yield and WUE continuously increased in NP and NPM treatments after 22 years of fertilization. Yield ranged from 3458 to 3782 kg/ha in NP or NPM but was 1246–1531 kg/ha in CK and single N or P. WUE in CK and single N or P treatments was < 6 kg/ha/mm but increased to 12.1 kg/ha/mm in a NP treatment. The NP and NPM fertilization provided benefits for increased yield and WUE but resulted in lower ASWS. Increasing ASWS may be important for sustainable yield after long-term fertilization.

scholarly journals Responses of soil water storage and crop water use efficiency to changing climatic conditions: A lysimeter-based space-for-time approach

2019 ◽  
Author(s):  
Jannis Groh ◽  
Jan Vanderborght ◽  
Thomas Pütz ◽  
Hans-Jörg Vogel ◽  
Ralf Gründling ◽  
...  
Keyword(s):  
Soil Water ◽  
Water Use ◽  
Grain Quality ◽  
Climatic Conditions ◽  
Soil Water Storage ◽  
Crop Water ◽  
Long Term Effects ◽  
Crop Water Use ◽  
Use Efficiency

Abstract. Future crop production will be affected by climatic changes. In several regions, the projected changes in total rainfall and seasonal rainfall patterns will lead to lower soil water storage (SWS) which in turn affects crop water uptake, crop yield, water use efficiency, grain quality and groundwater recharge. Effects of climate change on those variables depend on the soil properties and were often estimated based on model simulations. The objective of this study was to investigate the response of key variables in four different soils and for two different climates in Germany with different aridity index: 1.09 for the wetter (range: 0.82 to 1.29) and 1.57 for the drier climate (range: 1.19 to 1.77), by using high-precision weighable lysimeters. According to a “space-for-time” concept, intact soil monoliths that were moved to sites with contrasting climatic conditions have been monitored from April 2011 until December 2018. Evapotranspiration was lower for the same soil under the relatively drier climate whereas crop yield was significantly higher, without affecting grain quality. Especially non-productive water losses (evapotranspiration out of the main growing period) were lower which led to a more efficient crop water use in the drier climate. A characteristic decrease of the SWS for soils with a finer texture was observed after a longer drought period under a drier climate. The reduced SWS after the drought remained until the end of the observation period which demonstrates carry-over of drought from one growing season to another and the overall long term effects of single drought events. In the relatively drier climate, water flow at the soil profile bottom showed a small net upward flux over the entire monitoring period as compared to downward fluxes (ground water recharge) or drainage in the relatively wetter climate and larger recharge rates in the coarser- as compared to finer-textured soils. The large variability of recharge from year to year and the long lasting effects of drought periods on SWS imply that long term monitoring of soil water balance components is necessary to obtain representative estimates. Results confirmed a more efficient crop water use under less optimal soil moisture conditions. Long-term effects of changing climatic conditions on the SWS and ecosystem productivity should be considered when trying to develop adaptation strategies in the agricultural sector.

scholarly journals Net ecosystem carbon exchange in three contrasting Mediterranean ecosystems – the effect of drought

2007 ◽  
Vol 4 (5) ◽  
pp. 791-802 ◽  
Author(s):  
J. S. Pereira ◽  
J. A. Mateus ◽  
L. M. Aires ◽  
G. Pita ◽  
C. Pio ◽  
...  
Keyword(s):  
Photosynthetic Photon Flux Density ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Severe Drought ◽  
Photosynthetic Photon Flux ◽  
Oak Woodland ◽  
Eucalyptus Plantation ◽  
Use Efficiency ◽  
Rain Use Efficiency ◽  
Evergreen Oak

Abstract. Droughts reduce gross primary production (GPP) and ecosystem respiration (Reco), contributing to most of the inter-annual variability in terrestrial carbon sequestration. In seasonally dry climates (Mediterranean), droughts result from reductions in annual rainfall and changes in rain seasonality. We compared carbon fluxes measured by the eddy covariance technique in three contrasting ecosystems in southern Portugal: an evergreen oak woodland (savannah-like) with ca.~21% tree crown cover, a grassland dominated by herbaceous annuals and a coppiced short-rotation eucalyptus plantation. During the experimental period (2003–2006) the eucalyptus plantation was always the strongest sink for carbon: net ecosystem exchange rate (NEE) between −861 and −399 g C m−2 year−1. The oak woodland and the grassland were much weaker sinks for carbon: NEE varied in the oak woodland between −140 and −28 g C m−2 year−1 and in the grassland between −190 and +49 g C m−2 year−1. The eucalyptus stand had higher GPP and a lower proportion of GPP spent in respiration than the other systems. The higher GPP resulted from high leaf area duration (LAD), as a surrogate for the photosynthetic photon flux density absorbed by the canopy. The eucalyptus had also higher rain use efficiency (GPP per unit of rain volume) and light use efficiency (the daily GPP per unit incident photosynthetic photon flux density) than the other two ecosystems. The effects of a severe drought could be evaluated during the hydrological-year (i.e., from October to September) of 2004–2005. Between October 2004 and June 2005 the precipitation was only 40% of the long-term average. In 2004–2005 all ecosystems had GPP lower than in wetter years and carbon sequestration was strongly restricted (less negative NEE). The grassland was a net source of carbon dioxide (+49 g C m−2 year−1). In the oak woodland a large proportion of GPP resulted from carbon assimilated by its annual vegetation component, which was strongly affected by the shortage of rain in winter. Overall, severe drought affected more GPP than Reco leading to the deterioration of NEE. Although the rain-use efficiency of the eucalyptus plantation increased in the dry year, this was not the case of evergreen oak woodland, which rain-use efficiency was not influenced by drought. Recovery after drought alleviation, i.e., beginning with heavy rain in October 2005, was fully accomplished in 2006 in the oak woodland and grassland, but slow in the eucalyptus plantation.

Timing irrigation to suit citrus phenology: a means of reducing water use without compromising fruit yield and quality?

2007 ◽  
Vol 47 (1) ◽  
pp. 71 ◽  
Author(s):  
R. J. Hutton ◽  
J. J. Landsberg ◽  
B. G. Sutton
Keyword(s):  
Water Stress ◽  
Water Use Efficiency ◽  
Soil Water ◽  
Water Use ◽  
Fruit Size ◽  
Fruit Growth ◽  
Fruit Yield ◽  
Juice Quality ◽  
Water Deficits ◽  
Use Efficiency

This paper addresses the question of whether a citrus crop has the same need for water at all stages of development or whether it is possible to withhold water at times when the crop is less sensitive to water stress, thus, reducing total water use and improving water use efficiency while still maintaining yield. To answer this question water applied by irrigation was reduced by up to 33% relative to standard full irrigation by extending the intervals between applications from 3 to 17 days during fruit growth stages II and III in the annual growth cycle. As expected, the longer intervals resulted in greater depletion in soil moisture and significant water stress developed as soil water deficits approached the lower limits of plant available water. Stressed trees exhibited mean pre-dawn water potential (ψl) values of –0.93 MPa and midday ψl values decreased to between –2.0 and –2.5 MPa. Periodic soil water deficits in late summer and autumn reduced shoot growth, but fruit yield was unaffected, and there was no evidence of reduced canopy size. Water use efficiency (mass of fruit produced per unit water applied) improved, but fruit growth was extremely sensitive to moisture stress and extended irrigation intervals in summer and autumn reduced fruit size. Fruit juice quality was also affected, as there was an increase in both total soluble solids and juice acidity, but the practical consequences of these were limited because there were only small changes to the sugar : acid ratios. This work has demonstrated that deficient irrigation during summer can be used to manipulate growth and reduce water use, but at the risk of a marginal reduction in fruit size.

Water Use, Grain Yield, and Osmoregulation in Wheat

1986 ◽  
Vol 13 (4) ◽  
pp. 523 ◽  
Author(s):  
JM Morgan ◽  
AG Condon
Keyword(s):  
Grain Yield ◽  
Water Use Efficiency ◽  
Soil Water ◽  
Water Use ◽  
Harvest Index ◽  
High Water ◽  
Total Water ◽  
Water Deficits ◽  
Turgor Maintenance ◽  
Use Efficiency

Genotypic differences in turgor maintenance in wheat were shown to be associated with differences in grain yield in the field at both high and Low water deficits. High water deficits were produced by growing plants in field plots using water stored in the soil at sowing, and excluding rain with a rain cover. At low water deficits plants received rainfall, and irrigation was supplied before and immediately after sowing, at tillering, at jointing, at ear emergence, and during grain filling. Yield differences were analysed in terms of harvest index, water use, and water use efficiency. Water use was calculated from changes in soil water contents. At high water deficits all three factors were associated with differences in turgor maintenance. However, only the variations in water use and harvest index could be logically associated with differences in turgor maintenance. Analysis of the soil water extraction data showed that the differences in water use efficiency were due solely to differences in water use at depth while surface water losses were the same, i.e. the ratio of transpiration to soil evaporation would have been higher in low-osmoregulating genotypes. At low water deficits, no differences were observed in harvest index, though there were non-significant correlations between turgor maintenance and total water use efficiency or total water use. A similar result was obtained when the water use and yield data were related to osmoregulation measurements made in the glasshouse. It is therefore concluded that effects of turgor maintenance or osmoregulation on grain yield were primarily associated with differences in water use which were, in turn, due to differences in water extraction at soil depths between 25 and 150 cm.

Water-use efficiency of dryland canola in an equi-seasonal rainfall environment

2005 ◽  
Vol 56 (12) ◽  
pp. 1373 ◽  
Author(s):  
Michael J. Robertson ◽  
John A. Kirkegaard
Keyword(s):  
Water Supply ◽  
Water Use Efficiency ◽  
Soil Water ◽  
Water Use ◽  
Seasonal Rainfall ◽  
Annual Rainfall ◽  
Maximum Efficiency ◽  
Rainfall Distribution ◽  
Potential Yield ◽  
Use Efficiency

The French and Shultz approach that relates seasonal rainfall to potential yield in wheat has yet to be applied to dryland canola. Relationships were derived between grain yield of 42 experimental crops (yield range 0.5–5.4 t/ha) free of weeds, pests, diseases, and nutrient deficiencies in southern New South Wales, and various measures of observed (rainfall, available soil water) and simulated (evapotranspiration) seasonal water supply. April to October rainfall and in-crop rainfall were the poorest predictors of yield (R2 < 0.5). By adjusting in-crop rainfall to account for stored soil water at sowing and that remaining at harvest (termed ‘seasonal water supply’), 68% of the variance in yield could be explained. Estimates derived using the APSIM-Canola simulation model or simulated totals of evapotranspiration or transpiration explained 73–82% of the variance. The slope of the regression line between yield of the 42 crops, which simulation indicated had all yielded to their water-limited potential, and seasonal water supply (termed here the water-use efficiency for grain production, WUE) was 11 kg/ha.mm above an intercept of 120 mm. WUE varied from 4 to 18 kg/ha.mm and the upper boundary for WUE in those seasons where rainfall distribution facilitated maximum efficiency was 15 kg/ha.mm. Long-term simulations, conducted at locations with mean annual rainfall of 430–660 mm, confirmed the variability of WUE due to rainfall distribution and also that WUE would be expected to decline, on average, by one-third between sowings in early April and early July. This necessitates caution in accepting a single WUE value as an indicator of agronomic constraints to yield. For the purposes of practical application by farmers and advisors, water-limited potential yield can be calculated in the region as a function of seasonal water supply minus 120 mm up to a limit of 450 mm, beyond which potential yield is not limited by water. Available soil water at sowing can be estimated from summer fallow rainfall above a threshold of 80 mm, and water remaining at harvest can be estimated from post-anthesis rainfall above a threshold of 50 mm. This improved method for estimating water-limited potential yield in canola retains the ease of use of the French and Shultz approach, so that other constraints to yield can be more accurately diagnosed in dryland environments by farmers and advisors.

Changes in the soil quality attributes of continuous no-till farming systems following a strategic tillage

Soil Research ◽  
2015 ◽  
Vol 53 (3) ◽  
pp. 263 ◽  
Author(s):  
M. H. Crawford ◽  
V. Rincon-Florez ◽  
A. Balzer ◽  
Y. P. Dang ◽  
L. C. Carvalhais ◽  
...  
Keyword(s):  
Enzymatic Activity ◽  
Soil Water ◽  
Weed Control ◽  
Farming Systems ◽  
Annual Rainfall ◽  
First Year ◽  
Depth Range ◽  
Management Option ◽  
No Till

The adoption of no-till farming systems has greatly reduced energy and machinery inputs while significantly improving soil health and productivity. However, the control of crop weeds and diseases in no-till (NT) systems has become increasingly difficult for landholders in Australia’s northern grains regions, with occasional strategic tillage (ST) being considered as a potential management option. This study investigated the effects of occasional ST on physical, chemical and biological soil properties, productivity, and weed control on five long-term (7–44 years) NT-managed soils. The study area extended from Biloela (Vertosol, 666 mm annual rainfall), Condamine (Sodosol, 624 mm annual rainfall), Moonie (Dermosol, 636 mm annual rainfall) and Warwick (Vertosol, 675 mm annual rainfall) in Queensland to Wee Waa (Vertosol, 582 mm annual rainfall) in New South Wales. Tillage treatments included chisel, offset disc and prickle–disc chain with various timings and frequencies. Soil samples (0–0.3 m) obtained 3 and 12 months after occasional ST were analysed for total and particulate organic carbon (TOC, POC), available phosphorus (P), bulk density, soil water, and microbial enzymatic activity. In-crop weed density was also recorded. One-time tillage, with chisel tines, offset disc or chain harrows, in long-term NT helped to control winter weeds in the first year, with variable results in the second year. Grain yield overall showed no significant impact in either year, except on the Brown Sodosol (P = 0.08) in the first year. The initial impacts of strategic tillage on soil water were largely restricted to the 0–0.1 m depth range, with slight, non-significant decreases occurring. Available P, TOC, POC and total microbial enzymatic activity were not significantly impacted by either cultivation frequency or implement type. The use of an occasional ST for the purpose of weed control could be utilised as a viable management option for NT systems in the region without impacting on long-term productivity.

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