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Davis, CA, United States

Grieneisen M.L.,Air and Water Resources | Zhan Y.,Air and Water Resources | Potter D.,University of California at Davis | Zhang M.,Wenzhou Medical College
BioScience | Year: 2014

Geographic and political factors affect global research in many areas of biology with substantial field components. Progress in new species discovery continues to be undermined by sociopolitical impediments. The number of new species discovered from individual countries in 1 year is highly dependent on taxonomic infrastructure and country-scale biodiversity. Publication patterns suggest that alpha taxonomy is a higher research priority in high-biodiversity countries than in low-biodiversity countries. Alpha-taxonomy articles with authors affiliated with high-biodiversity, low-taxonomic-infrastructure tropical countries have very high rates of international collaboration, underscoring its importance in the discovery of new tropical species. Most new species descriptions include specimens collected less than 5 years prior to publication, which indicates the importance of ongoing collection efforts. National and international policies that strengthen both the taxonomic infrastructure of high-biodiversity countries and collaborations between high-biodiversity and high-taxonomic-infrastructure countries are necessary to accelerate global biodiversity discovery, given the current rapid rate of species extinctions. © 2014 The Author(s). Source

Soltanjalili M.-J.,University of Tehran | Haddad O.B.,University of Tehran | Marino M.A.,Air and Water Resources | Marino M.A.,University of California at Davis
Journal of Water Resources Planning and Management | Year: 2013

Population increase and requirements as well as water resource limitations reveal the necessity for the optimal operation of water distribution networks (WDNs), especially during shortage events. Because WDNs directly affect lifestyles, operational plans that take into account abnormal conditions are necessary. Under such circumstances, some possible solutions, such as transferring water from other basins or using recycled waters, may be inapplicable or insufficient, as continuous operation of WDNs would not be possible anymore. This paper proposes hedging or intermittent water supply as a contrasting way against a water shortage juncture. In this method of operation and in a specific time span during the operational period, the amount of water supplied to each consumer could be different even if their demands are equal. Thus, the selection of a policy that guarantees equity in supplying consumers' demands has to be considered. In addition, supplying demands with sufficient pressure would promote consumers' satisfaction. Hence, this method of operation needs a planning methodology that takes into account equity, satisfaction, available water, consumption fluctuations, and other social constraints besides hydraulic parameters influencing the behavior of WDNs and the interaction between them. The quantification of the aforementioned parameters and constraints requires mathematical models that simulate the behavior of networks and optimize the mentioned goals. In this paper, the operation of two networks is examined. The honey-bee mating optimization (HBMO) algorithm is used as the optimization tool linked to EPANET 2, which is the hydraulic simulator of the networks. To compare various methods of facing water shortage, WDN performance criteria are also calculated. Results show that a 100% resiliency criterion for hedging and intermittent water supply is 25-50% more favorable than other methods. In addition, a nodal resiliency criterion of water allocated under various operational methods and irrespective of initial storage volume of the reservoir show the superiority of intermittent water supply compared with other approaches, indicating the efficient management of available water allocated in the operational period. © 2013 American Society of Civil Engineers. Source

Fulton A.,University of California Cooperative Extension | Schwankl L.,University of California Kearney Research and Extension Center | Lynn K.,University of California Kearney Research and Extension Center | Lampinen B.,University of California at Davis | And 2 more authors.
Irrigation Science | Year: 2011

Orchard and vineyard producers conduct preplant site evaluations to help prevent planting permanent tree and vine crops on lands where the crop will not perform to its highest potential or attain its full life expectancy. Physical soil characteristics within specific soil profiles and spatially throughout an orchard influence decisions on land preparation, irrigation system selection, horticultural choices, and nutrient management. Producers depend on soil surveys to help them understand the soil characteristics of the land and may be interested in technology that provides additional information. Electromagnetic induction (EM38) and four-probe soil resistance sensors (VERIS) are being used in combination with global positioning systems to map spatial variability of soils using apparent soil electrical conductivity (ECa). The hypothesis evaluated in this study is whether rapid, in situ, and relatively low-cost methods of measuring ECa (EM38 and VERIS) can effectively identify and map physical soil variability in non-saline soils. The supposition is that in non-saline soils, ECa levels will relate well to soil texture and water-holding capacity and can be used to map physical soil variability. In turn, the information can be used to guide decisions on preplant tillage, irrigation system design, water and nutritional management, and other horticultural considerations. Two sites in the Sacramento Valley were mapped each with EM38 and VERIS methods. Site-specific management zones were identified by each provider on ECa maps for each site, and then soil samples were collected by University of California researchers to verify these zones. Results showed that on non-saline soils, ECa measured with both EM38 and VERIS correlate with physical soil properties such as gravel, sand, silt, and clay content but the relationship between conductivity and these physical soil properties varied from moderately strong to weak. The strength of the correlation may be affected by several factors including how dominant soil texture is on conductivity relative to other soil properties and on methods of equipment operation, data analysis and interpretation. Overall, the commercial providers of ECa surveys in this study delivered reasonable levels of accuracy that were consistent with results reported in previous studies. At one site, an ECa map developed with VERIS provided more detail on physical soil variability to supplement published soil surveys and aided in the planning and development of a walnut orchard. At a second site, almond yield appeared to correlate well with distinctly different soil zones identified with EM38 mapping. © 2010 The Author(s). Source

Tomich T.P.,University of California at Davis | Tomich T.P.,UC Statewide Sustainable Agriculture Research and Education Program | Brodt S.,University of California at Davis | Brodt S.,UC Statewide Sustainable Agriculture Research and Education Program | And 9 more authors.
Annual Review of Environment and Resources | Year: 2011

This review by a multidisciplinary team maps key components and emerging connections within the intellectual landscape of agroecology. We attempt to extend and preview agroecology as a discipline in which agriculture can be conceptualized within the context of global change and studied as a coupled system involving a wide range of social and natural processes. This intrinsic coupling, combined with powerful emerging drivers of change, presents challenges for the practice of agroecology and agriculture itself, as well as providing the framework for some of the most innovative research areas and the greatest potential for innovation for a sustainable future in agriculture. The objective of this review is to identify forward-looking scientific questions to enhance the relevance of agroecology for the key challenges of mitigating environmental impacts of agriculture while dramatically increasing global food production, improving livelihoods, and thereby reducing chronic hunger and malnutrition over the coming decades. © 2011 by Annual Reviews. All rights reserved. Source

Saaltink R.,University Utrecht | van der Velde Y.,Wageningen University | Dekker S.C.,University Utrecht | Lyon S.W.,University of Stockholm | Dahlke H.E.,Air and Water Resources
Journal of Hydrology: Regional Studies | Year: 2014

Study region: River basins draining into the Baltic Sea, known as the Baltic Sea Drainage Basin (BSDB). Study focus: Dramatic shifts in water quality have been observed in the Baltic Sea in past decades. This study investigated the spatial distribution of trends in nitrogen (N) and phosphorus (P) in relation to societal, land cover and climatic changes. A 31-year record of observed catchment scale nutrient concentration and discharge data for the period 1970-2000 was combined with climate and land cover data. A Mann-Kendall test was applied to reveal trends in N and P, the N:P ratio, discharge, temperature and precipitation. Classical factor analysis and Kendall's rank correlation identified the most important relationships between nutrients, land cover and climate. New hydrological insights for the region: A large spatial variability in N and P trends was observed with a notable difference between the east and west of the BSDB. The existence of regional trend variations are important for nutrient load reduction management strategies. Specifically, it is recommended that strategies targeting seawater eutrophication should focus more on P rather than N reduction because increasing P in the eastern catchments is responsible for the overall declining trend in the N:P ratio, an important trigger for algal blooms. © 2014 The Authors. Source

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