scholarly journals Interactive effects of irradiance and water availability on the photosynthetic performance of Picea sitchensis seedlings: implications for seedling establishment under different management practices

2005 ◽  
Vol 62 (5) ◽  
pp. 413-422 ◽  
Author(s):  
Kevin Black ◽  
Phill Davis ◽  
Joseph Mc Grath ◽  
Pat Doherty ◽  
Bruce Osborne
Keyword(s):  
Water Availability ◽  
Seedling Establishment ◽  
Management Practices ◽  
Photosynthetic Performance ◽  
Picea Sitchensis ◽  
Interactive Effects

scholarly journals How downstream sub-basins depend on upstream inflows to avoid scarcity: typology and global analysis of transboundary rivers

2018 ◽  
Vol 22 (5) ◽  
pp. 2795-2809 ◽  
Author(s):  
Hafsa Ahmed Munia ◽  
Joseph H. A. Guillaume ◽  
Naho Mirumachi ◽  
Yoshihide Wada ◽  
Matti Kummu
Keyword(s):  
Water Stress ◽  
Water Use ◽  
Water Availability ◽  
Water Scarcity ◽  
Management Practices ◽  
Global Analysis ◽  
Water Shortage ◽  
River Basins ◽  
Analytical Framework ◽  
Available Water

Abstract. Countries sharing river basins are often dependent upon water originating outside their boundaries; meaning that without that upstream water, water scarcity may occur with flow-on implications for water use and management. We develop a formalisation of this concept drawing on ideas about the transition between regimes from resilience literature, using water stress and water shortage as indicators of water scarcity. In our analytical framework, dependency occurs if water from upstream is needed to avoid scarcity. This can be diagnosed by comparing different types of water availability on which a sub-basin relies, in particular local runoff and upstream inflows. At the same time, possible upstream water withdrawals reduce available water downstream, influencing the latter water availability. By developing a framework of scarcity and dependency, we contribute to the understanding of transitions between system regimes. We apply our analytical framework to global transboundary river basins at the scale of sub-basin areas (SBAs). Our results show that 1175 million people live under water stress (42 % of the total transboundary population). Surprisingly, the majority (1150 million) of these currently suffer from stress only due to their own excessive water use and possible water from upstream does not have impact on the stress status – i.e. they are not yet dependent on upstream water to avoid stress – but could still impact on the intensity of the stress. At the same time, 386 million people (14 %) live in SBAs that can avoid stress owing to available water from upstream and have thus upstream dependency. In the case of water shortage, 306 million people (11 %) live in SBAs dependent on upstream water to avoid possible shortage. The identification of transitions between system regimes sheds light on how SBAs may be affected in the future, potentially contributing to further refined analysis of inter- and intrabasin hydro-political power relations and strategic planning of management practices in transboundary basins.

scholarly journals Irrigation practices, nutrient applications, and mulches affect soil nutrient dynamics in a young Merlot (Vitis vinifera L.) vineyard

2016 ◽  
Vol 96 (1) ◽  
pp. 23-36 ◽  
Author(s):  
Kirsten D. Hannam ◽  
Gerry H. Neilsen ◽  
Thomas A. Forge ◽  
Denise Neilsen ◽  
Istvan Losso ◽  
...  
Keyword(s):  
Vitis Vinifera ◽  
Soil Carbon ◽  
Nutrient Dynamics ◽  
Management Practices ◽  
Soil Nutrient ◽  
Crop Productivity ◽  
Interactive Effects ◽  
Vitis Vinifera L ◽  
Nutrient Pools ◽  
Soil P

There is growing interest among commercial wine grape (Vitis vinifera L.) growers in reducing water and fertilizer consumption, but little information exists on how best to combine conservative irrigation and soil management practices in the vineyard. In a 3-year-old Merlot vineyard in the semi-arid Okanagan Valley, British Columbia, the interactive effects of resource-conserving micro-irrigation (drippers or microsprinkers), nutrient applications (fertigation or compost), and surface mulching (wood and bark chips) on nitrogen (N) and phosphorus (P) dynamics in the wetted zone of surface soils were examined throughout the growing season using ion-exchange resins. Treatment differences in soil carbon and major nutrient pools, temperature, and moisture were also measured. Higher NO3-N was adsorbed by resins buried under drippers than under microsprinklers except in mulched plots, where NO3-N was uniformly low. By enhancing soil carbon availability and moderating soil microclimate, surface mulches may have promoted microbial immobilisation of N. Compost applications increased soil ortho-P levels, especially on mulched plots, suggesting that both P inputs (from compost) and enhanced microbial biomass (from mulch) promoted soil P cycling. Future work will examine the interactive effects of these resource-efficient practices on leaching losses, greenhouse gas emissions, crop productivity, and fruit quality.

Size of subsoil clods affects soil-water availability in sand–clay mixtures

Soil Research ◽  
2016 ◽  
Vol 54 (3) ◽  
pp. 276 ◽  
Author(s):  
Giacomo Betti ◽  
Cameron D. Grant ◽  
Robert S. Murray ◽  
G. Jock Churchman
Keyword(s):  
Hydraulic Conductivity ◽  
Soil Water ◽  
Best Management Practices ◽  
Water Availability ◽  
Water Retention ◽  
Management Practices ◽  
Crop Yields ◽  
Root Zone ◽  
Soil Water Availability ◽  
Application Rates

Clay delving in strongly texture-contrast soils brings up subsoil clay in clumps ranging from large clods to tiny aggregates depending on the equipment used and the extent of secondary cultivation. Clay delving usually increases crop yields but not universally; this has generated questions about best management practices. It was postulated that the size distribution of the subsoil clumps created by delving might influence soil-water availability (and hence crop yield) because, although the clay increases water retention in the root-zone, it can also cause poor soil aeration, high soil strength and greatly reduced hydraulic conductivity. We prepared laboratory mixtures of sand and clay-rich subsoil in amounts considered practical (10% and 20% by weight) and excessive (40% and 60% by weight) with different subsoil clod sizes (<2, 6, 20 and 45 mm), for which we measured water retention, soil resistance, and saturated hydraulic conductivity. We calculated soil water availability by traditional means (plant-available water, PAW) and by the integral water capacity (IWC). We found that PAW increased with subsoil clay, particularly when smaller aggregates were used (≤6 mm). However, when the potential restrictions on PAW were taken into account, the benefits of adding clay reached a peak at ~40%, beyond which IWC declined towards that of pure subsoil clay. Furthermore, the smaller the aggregates the less effective they were at increasing IWC, particularly in the practical range of application rates (<20% by weight). We conclude that excessive post-delving cultivation may not be warranted and may explain some of the variability found in crop yields after delving.

Interactive effects of UV radiation and water availability on seedlings of six woody Mediterranean species

2012 ◽  
Vol 147 (2) ◽  
pp. 234-247 ◽  
Author(s):  
Meritxell Bernal ◽  
Laura Llorens ◽  
Jordi Badosa ◽  
Dolors Verdaguer
Keyword(s):  
Uv Radiation ◽  
Water Availability ◽  
Interactive Effects ◽  
Mediterranean Species

scholarly journals Seed biology of brome grass weeds (Bromus diandrus and B hordeaceus) and effects of land management

2010 ◽  
Vol 63 ◽  
pp. 78-83
Author(s):  
F. Dastgheib ◽  
N. Poole
Keyword(s):  
Land Management ◽  
Seedling Establishment ◽  
Management Practices ◽  
Detrimental Effect ◽  
Soil Surface ◽  
Seed Burial ◽  
Bromus Diandrus ◽  
Seed Biology ◽  
Brome Grass ◽  
Brome Grasses

Aspects of seed biology of ripgut brome (Bromus diandrus) and soft brome (B hordeaceus) were studied in relation to land management practices Among the practices tested burning stubble had a detrimental effect on seed survival The majority of seeds close to the soil surface were charred or nonviable following a stubble fire Overall higher brome infestation was measured in notillage compared to minimum tillage or burning treatments More than 80 of the seeds of both species emerged in the field within the first couple of months after planting and full germination was achieved by spring Seed burial at depths from 1 to 20 cm did not significantly affect germination but seedling establishment and vigour was reduced with seed depth Implications of these results in management of brome grasses are discussed

Climatic and fire determinants of early life-history stages in the Mediterranean shrub Cistus albidus

2019 ◽  
Vol 13 (1) ◽  
pp. 3-11 ◽  
Author(s):  
Sandra Saura-Mas ◽  
Anna Saperas ◽  
Franciso Lloret
Keyword(s):  
Life History ◽  
Heat Shock ◽  
Water Availability ◽  
Seedling Establishment ◽  
Reproductive Traits ◽  
Fruit Production ◽  
Fire Disturbance ◽  
Drought Event ◽  
Adult Density ◽  
Cistus Albidus

Abstract Aims Cistus albidus reproductive traits have been studied on typical Mediterranean shrublands along a water availability gradient in Northeastern Iberian Peninsula. Germination of this species is known to be highly favoured by fire. Moreover, Mediterranean species are particularly dependent on water availability. Therefore, we establish the hypothesis that in addition to fire disturbance, seedling recruitment in this Mediterranean seeder will be improved in drought-induced episodes resulting in generalized canopy die-off. Methods Individuals of several populations of C. albidus were collected and the size, weight and number of fruits and seeds were measured. Germination tests were also carried out on five pre-germination treatments: seeds’ exposure to heat shock, imbibition, two cycles of imbibition/desiccation and the combination of heat shock and imbibition and imbibition/desiccation cycles. Moreover, the number of seedlings after a drought event was surveyed in the field and correlated with canopy die-off. Important findings Our study shows the variability of the C. albidus reproductive traits, such as germination rate or fruit production, along the water availability gradient. This variability resulted in a decrease in fruit production but an increase in successful germination under drier conditions. Cistus albidus seeds increased germination with heat, demonstrating their ability to successfully establish after fire. However, recruitment was not exclusively fire dependent since seedling establishment was higher under C. albidus canopies that had collapsed after the extreme drought. Finally, adult density increased C. albidus die-off and mortality, as well as seedling establishment. These results suggest that this species exhibits a trade-off between different reproductive outcomes (i.e. seed production vs. viability), which in turn is determined by climate. This study also provides evidence of how intra-specific competition, climate, particularly drought events and fire disturbance, can determine the success of key early stages of the life history of a common, representative Mediterranean fire-prone seeder shrub.

scholarly journals Quantification of Key Genes Steering the Microbial Nitrogen Cycle in the Rhizosphere of Sorghum Cultivars in Tropical Agroecosystems

2009 ◽  
Vol 75 (15) ◽  
pp. 4993-5000 ◽  
Author(s):  
Brigitte Hai ◽  
Ndeye Hélène Diallo ◽  
Saidou Sall ◽  
Felix Haesler ◽  
Kristina Schauss ◽  
...  
Keyword(s):  
Microbial Communities ◽  
Nitrogen Cycle ◽  
Plant Development ◽  
Water Availability ◽  
Management Practices ◽  
Ammonia Oxidation ◽  
Organic Fertilizers ◽  
Ammonia Oxidizing Bacteria ◽  
Development Stages ◽  
The Impact

ABSTRACT The effect of agricultural management practices on geochemical cycles in moderate ecosystems is by far better understood than in semiarid regions, where fertilizer availability and climatic conditions are less favorable. We studied the impact of different fertilizer regimens in an agricultural long-term observatory in Burkina Faso at three different plant development stages (early leaf development, flowering, and senescence) of sorghum cultivars. Using real-time PCR, we investigated functional microbial communities involved in key processes of the nitrogen cycle (nitrogen fixation, ammonia oxidation, and denitrification) in the rhizosphere. The results indicate that fertilizer treatments and plant development stages combined with environmental factors affected the abundance of the targeted functional genes in the rhizosphere. While nitrogen-fixing populations dominated the investigated communities when organic fertilizers (manure and straw) were applied, their numbers were comparatively reduced in urea-treated plots. In contrast, ammonia-oxidizing bacteria (AOB) increased not only in absolute numbers but also in relation to the other bacterial groups investigated in the urea-amended plots. Ammonia-oxidizing archaea exhibited higher numbers compared to AOB independent of fertilizer application. Similarly, denitrifiers were also more abundant in the urea-treated plots. Our data imply as well that, more than in moderate regions, water availability might shape microbial communities in the rhizosphere, since low gene abundance data were obtained for all tested genes at the flowering stage, when water availability was very limited.

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