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531.
Long-term experiments on different crop management systems provide essential information about turnover of soil organic matter
and changes in microbial properties over a period of time. A long-term field site trial, which was established in 1967 near
Vienna, Austria, to document the fate of 14C-labelled manure (straw and farmyard) under different crop management systems (crop rotation, spring wheat and bare fallow),
was investigated. Soil samples were taken in 1997 and separated into size fractions (>250 μm, 250–63 μm, 63–2 μm, 2–0.1 μm
and <0.1 μm) after aggregate dispersion using low-energy sonication. Organic C, total N and 14C content were measured in the bulk soil and the size fractions and microbial properties were analysed in the bulk soil. Additionally,
C mineralization in bulk soil samples was monitored at 20 °C over a period of 28 days, and subsequently 14C-CO2 content was analysed. The distribution of organic C and N within the size fractions was similar between crop rotation and
spring wheat; the highest amounts of organic C and N were found in the clay-sized fraction. The amounts of C and N were significantly
smaller in the bare fallow, which was depleted of organic matter in the coarse-sized fractions. 14C distribution differed significantly from unlabelled C distribution, labelled C was accumulated in the silt-sized fraction,
indicating weak humification of the applied manure C. The highest rate of C mineralization was measured in the crop rotation
and spring wheat, whereas the emission rate of the bare fallow was about 40% lower. The higher 14C:C ratio of the bulk soil in comparison to the emitted CO2 indicated that labelled C compounds still remained mineralizable after a period of 30 years. Microbial properties showed
a great difference between crop management systems and bare fallow, particularly regarding urease and xylanase activity.
Received: 31 May 1999 相似文献
532.
Celene Navarro Roberto Civera Olivia Arjona Crisalejandra Rivera‐Perez Hugo Sergio García Miguel ngel Hurtado‐Oliva Elena Palacios 《Aquaculture Research》2020,51(4):1602-1622
We substituted 10% of fishmeal with scallop (Argopecten ventricosus) or squid (Dosidiscus gigas) by‐product meal in a feed for shrimp (Litopenaeus vannamei) growth assay that lasted 60 days and then shrimps were submitted to handling stress. Shrimp fed the control diet had smaller weight gain and lower recovery after stress. Prostaglandins in gills were affected by diet and stress, with significant differences in shrimp fed the control diet before and after the stress. Hydroperoxides were increased after stress, while isoprostanoids were higher in shrimp fed the control diet. The gene expression of Glutathione peroxidase and Catalase was increased on the stressed shrimp fed the scallop diet, with no differences among diets for Superoxide dismutase or Cyclooxygenase. Arachidonic acid in the phospholipid fraction of muscle was the only fatty acid affected by stress and diet. Cholesterol oxidation products were significantly higher in shrimp fed the scallop diet compared to shrimp fed the control diet before applying the stress. A PCA analysis grouped in one‐factor growth variables, as well as Superoxide dismutase, esterified astaxanthin and isoprostane, while another factor was determined by stress, prostaglandin and hydroperoxide levels in gills. The partial substitution of fishmeal with scallop of squid by‐product meals affected growth and stress differently, indicating shrimp that grew up more were not necessarily more tolerant to handling stress, which can have a strong repercussion in aquaculture, particularly during density control, recording of growth and harvest. 相似文献
533.
Richard B. Sherley Hannah Ladd‐Jones Stefan Garthe Olivia Stevenson Stephen C. Votier 《Fish and Fisheries》2020,21(1):132-145
Every year fisheries discard >10 million tonnes of fish. This provides a bounty for scavengers, yet the ecological impact of discarding is understudied. Seabirds are the best‐studied discard scavengers and fisheries have shaped their movement ecology, demography and community structure. However, we know little about the number of scavenging seabirds that discards support, how this varies over time or might change as stocks and policy change. Here, we use a Bayesian bioenergetics model to estimate the number of scavenging birds potentially supported by discards in the North Sea (one of the highest discard‐producing regions) in 1990, around the peak of production, and again after discard declines in 2010. We estimate that North Sea discards declined by 48% from 509,840 tonnes in 1990 to 267,549 tonnes in 2010. This waste had the potential to support 5.66 (95% credible intervals: 3.33–9.74) million seabirds in the 1990s, declining by 39% to 3.45 (1.98–5.78) million birds by 2010. Our study reveals the potential for fishery discards to support very large scavenging seabird communities but also shows how this has declined over recent decades. Discard bans, like the European Union's Landing Obligation, may reduce inflated scavenger communities, but come against a backdrop of gradual declines potentially buffering deleterious impacts. More work is required to reduce uncertainty and to generate global estimates, but our study highlights the magnitude of scavenger communities potentially supported by discards and thus the importance of understanding the wider ecological consequences of dumping fisheries waste. 相似文献
534.
Farmers' perceptions of and responses to environmental change in southwest coastal Bangladesh
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Md Jahangir Kabir Rob Cramb Mohammad Alauddin Christian Roth Steven Crimp 《Asia Pacific viewpoint》2017,58(3):362-378
Coastal Bangladesh is highly vulnerable to climate change and salinisation; hence, farm‐level adaptation is critically important. Farmers' perceptions of and responses to environmental change were investigated in two villages in Khulna District. Perceived environmental trends included increases in temperature, extreme weather events, soil toxicity, erratic rainfall and scarcity of water for irrigation. Perceptions of climate trends were consistent with measured trends in Khulna. On‐farm adaptation strategies included adjusting planting dates, excavating trenches in rice‐fields, adopting new crops, salinity‐reducing technologies, livestock‐rearing and home‐yard cropping. Non‐farm adaptation strategies included wage employment, short‐term migration and self‐employment. Adaptation was facilitated by income‐earning opportunities, training, and credit, and impeded by lack of access to water, markets, capital, and extension services. Farmers suggested policy support for dissemination of stress‐tolerant cultivars, access to irrigation, and price stabilisation or crop insurance to assist adaptation. While the study shows an impressive degree of awareness and adaptation, external support is needed to increase adaptive capacity. 相似文献
535.
Roth 《Forstwissenschaftliches Centralblatt》1894,16(5):248-251
Ohne Zusammenfassung 相似文献
536.
Roth 《European Journal of Forest Research》1871,15(1):389-390
Ohne Zusammenfassung 相似文献
537.
Roth 《European Journal of Forest Research》1862,6(1):196-197
Ohne Zusammenfassung 相似文献
538.
Forstmeister Julius Roth 《Forstwissenschaftliches Centralblatt》1916,38(8-9):377-402
Ohne Zusammenfassung 相似文献
539.
Relationships between flour functional properties and protein composition were studied using a set of 138 Argentinean wheat samples. Among different protein groups, the incremental increase of gliadin with increasing grain protein content was highest followed by polymeric protein with albumin‐globulin content much lower. Functional properties could be divided into two groups based on dependence on protein composition. Properties such as dough extensibility and bake test loaf volume correlated highly with the percentage of polymeric protein in the grain. Properties such as mixograph dough development time were best correlated with the percentage of polymeric protein in the protein (PPP). Alveograph tenacity showed no significant dependence on PPP. as found previously for extensigraph maximum resistance, but it was correlated with the percentage of unextractable polymeric protein in the protein. Energy (W) appeared to be a more useful alveograph parameter for predicting flour quality. 相似文献