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- Barron, Jennie, 1968-
(författare)
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Dry spell mitigation to upgrade semi-arid rainfed agriculture : Water harvesting and soil nutrient management for smallholder maize cultivation in Machakos, Kenya
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Improvements in on-farm water and soil fertility management through water harvesting may prove key to up-grade smallholder farming systems in dry sub-humid and semi-arid sub-Sahara Africa (SSA). The currently experienced yield levels are usually less than 1 t ha-1, i.e., 3-5 times lower than potential levels obtained by commercial farmers and researchers for similar agro-hydrological conditions. The low yield levels are ascribed to the poor crop water availability due to variable rainfall, losses in on-farm water balance and inherently low soil nutrient levels. To meet an increased food demand with less use of water and land in the region, requires farming systems that provide more yields per water unit and/or land area in the future. This thesis presents the results of a project on water harvesting system aiming to upgrade currently practised water management for maize (Zea mays, L.) in semi-arid SSA. The objectives were to a) quantify dry spell occurrence and potential impact in currently practised small-holder grain production systems, b) test agro-hydrological viability and compare maize yields in an on-farm experiment using combinations supplemental irrigation (SI) and fertilizers for maize, and c) estimate long-term changes in water balance and grain yields of a system with SI compared to farmers currently practised in-situ water harvesting. Water balance changes and crop growth were simulated in a 20-year perspective with models MAIZE1&2. Dry spell analyses showed that potentially yield-limiting dry spells occur at least 75% of seasons for 2 locations in semi-arid East Africa during a 20-year period. Dry spell occurrence was more frequent for crop cultivated on soil with low water-holding capacity than on high water-holding capacity. The analysis indicated large on-farm water losses as deep percolation and run-off during seasons despite seasonal crop water deficits. An on-farm experiment was set up during 1998-2001 in Machakos district, semi-arid Kenya. Surface run-off was collected and stored in a 300m3 earth dam. Gravity-fed supplemental irrigation was carried out to a maize field downstream of the dam. Combinations of no irrigation (NI), SI and 3 levels of N fertilizers (0, 30, 80 kg N ha-1) were applied. Over 5 seasons with rainfall ranging from 200 to 550 mm, the crop with SI and low nitrogen fertilizer gave 40% higher yields (**) than the farmers’ conventional in-situ water harvesting system. Adding only SI or only low nitrogen did not result in significantly different yields. Accounting for actual ability of a storage system and SI to mitigate dry spells, it was estimated that a farmer would make economic returns (after deduction of household consumption) between year 2-7 after investment in dam construction depending on dam sealant and labour cost used. Simulating maize growth and site water balance in a system of maize with SI increased annual grain yield with 35 % as a result of timely applications of SI. Field water balance changes in actual evapotranspiration (ETa) and deep percolation were insignificant with SI, although the absolute amount of ETa increased with 30 mm y-1 for crop with SI compared to NI. The dam water balance showed 30% productive outtake as SI of harvested water. Large losses due to seepage and spill-flow occurred from the dam. Water productivity (WP, of ETa) for maize with SI was on average 1 796 m3 per ton grain, and for maize without SI 2 254 m3 per ton grain, i.e, a decerase of WP with 25%. The water harvesting system for supplemental irrigation of maize was shown to be both biophysically and economically viable. However, adoption by farmers will depend on other factors, including investment capacity, know-how and legislative possibilities. Viability of increased water harvesting implementation in a catchment scale needs to be assessed so that other down-stream uses of water remains uncompromised.
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- Barthel, Stephan, 1968-
(författare)
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Recalling Urban Nature : Linking City People to Ecosystem Services
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Societal development is dependent on the generation of ecosystem services (ES) to sustain it; however, many ES are degrading. This thesis investigates how social-ecological features behind practices of actor groups shape the generation of ES. The empirical basis is case studies in the urban landscape of Stockholm, Sweden, and the methodological approach is interdisciplinary. Paper I shows that the urban landscape owes it current flow of ES to co-evolutionary processes and that governance with the aim of sustaining ES must take into account historical property rights and the involvement of a diversity of actor groups, as well as ecological processes of the larger landscape. Paper II studies allotment gardens, cemeteries and city parks in relation to the generation of pollination, seed dispersal and pest regulation. Differences in social features behind practice are reflected primary as higher abundance of pollinators in the informally managed allotment gardens and as differences in the compositions of seed dispersers and insectivores’ birds. Thus, voluntary and often ignored actor groups, motivated by sense-of-place, support the generation of some ES here. Paper III shows how practice, linked to ES generation, is retained and stored among allotment gardeners, and modified and transmitted through time, by means of social-ecological memory (SE-memory). SE-memory is an emergent property of a dual process of participation and reification and it facilitates monitoring of local change and links practice, often in habits, to place specific processes that underlie provisioning ES. Paper IV explores how spatial scale mismatches between ecological process and processes of management can be bridged by a spatially explicit and flexible social network structure of governance. Urban ES are a product of human driven co-evolution, consequently sustaining ES in urban landscapes is not about conservation without people, but shaped by and dependent on management practice by people. Practice that links to generation of ES are facilitated by SE-memory of local actors that holds long term management rights. Consequently, local communities of ecosystem practice, which contribute to the production of ES should explicitly be taken into account in urban green governance.
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- Bergeron, Tor, et al.
(författare)
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'Fimbulvinter'
- 1956
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Ingår i: Fornvännen. - 0015-7813 .- 1404-9430. ; 51, s. 1-18
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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- Biggs, Reinette, et al.
(författare)
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Regime Shifts
- 2011
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Ingår i: Sourcebook in Theoretical Ecology. - : University of California Press.
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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- Bäckman, Carl G, et al.
(författare)
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A case-control study of the influence of the ICU-diary concept on mastery and hopelessness six months after critical illness
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The ICU-diary concept is associated with less post-traumatic stress syndrome and improved perceived health-related quality-of-life (HRQoL) after critical illness, but little is known about its effect on the coping- mastery process, or whether it reduces hopelessness. Objective: To see if the ICU-diary concept improves the patient’s ability to master his/her situation after critical illness, and if it reduces the feeling of hopelessness. Design: Case control study (subgroup analysis of a multi-centre study on health-related quality-of-life (HRQoL). Setting: Non-academic 8-bed general ICU. Patients: Adults admitted between March 2002 and June 2004. Measurements: Mastery and hopelessness were determined using validated questionnaires (the Mastery-Coping scale and a consolidated 2–item hopelessness questionnaire) which were sent home to patients 6 months after critical illness. Responses were compared between patients that received (Cases: n=38) or did not receive an ICU-diary (Controls: n=76) . Diaries were used when a long and complicated stay on the ICU was expected. Controls were matched with diary patients by gender and age. The effect of the ICU-diary was also examined using a multiple regression model. Results: The ICU-diary concept group scored significantly higher than the No-diary group in mastery (22.1 vs. 20.4, P<0.05) and lower in hopelessness scores (1.3 vs. 1.6, P<0.05). The positive influence of the ICU-diary disappeared after adjustment for confounding factors in a multiple regression model. Conclusion: We were unable to verify any positive influence of the ICU-diary concept on mastery and hopelessness 6 months after critical illness.
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