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1.
Nitrogen yield advantage from grass–legume mixtures is robust over a wide range of legume proportions and environmental conditions 下载免费PDF全文
Matthias Suter John Connolly John A. Finn Ralf Loges Laura Kirwan Maria‐Teresa Sebastià Andreas Lüscher 《Global Change Biology》2015,21(6):2424-2438
Current challenges to global food security require sustainable intensification of agriculture through initiatives that include more efficient use of nitrogen (N), increased protein self‐sufficiency through homegrown crops, and reduced N losses to the environment. Such challenges were addressed in a continental‐scale field experiment conducted over 3 years, in which the amount of total nitrogen yield (Ntot) and the gain of N yield in mixtures as compared to grass monocultures (Ngainmix) was quantified from four‐species grass–legume stands with greatly varying legume proportions. Stands consisted of monocultures and mixtures of two N2‐fixing legumes and two nonfixing grasses. The amount of Ntot of mixtures was significantly greater (P ≤ 0.05) than that of grass monocultures at the majority of evaluated sites in all 3 years. Ntot and thus Ngainmix increased with increasing legume proportion up to one‐third of legumes. With higher legume percentages, Ntot and Ngainmix did not continue to increase. Thus, across sites and years, mixtures with one‐third proportion of legumes attained ~95% of the maximum Ntot acquired by any stand and had 57% higher Ntot than grass monocultures. Realized legume proportion in stands and the relative N gain in mixture (Ngainmix/Ntot in mixture) were most severely impaired by minimum site temperature (R = 0.70, P = 0.003 for legume proportion; R = 0.64, P = 0.010 for Ngainmix/Ntot in mixture). Nevertheless, the relative N gain in mixture was not correlated to site productivity (P = 0.500), suggesting that, within climatic restrictions, balanced grass–legume mixtures can benefit from comparable relative gains in N yield across largely differing productivity levels. We conclude that the use of grass–legume mixtures can substantially contribute to resource‐efficient agricultural grassland systems over a wide range of productivity levels, implying important savings in N fertilizers and thus greenhouse gas emissions and a considerable potential for climate change mitigation. 相似文献
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Using euhalophytes to understand salt tolerance and to develop saline agriculture: Suaeda salsa as a promising model 总被引:5,自引:0,他引:5
Background As important components in saline agriculture, halophytes can help to provide food for a growing world population. In addition to being potential crops in their own right, halophytes are also potential sources of salt-resistance genes that might help plant breeders and molecular biologists increase the salt tolerance of conventional crop plants. One especially promising halophyte is Suaeda salsa, a euhalophytic herb that occurs both on inland saline soils and in the intertidal zone. The species produces dimorphic seeds: black seeds are sensitive to salinity and remain dormant in light under high salt concentrations, while brown seeds can germinate under high salinity (e.g. 600 mm NaCl) regardless of light. Consequently, the species is useful for studying the mechanisms by which dimorphic seeds are adapted to saline environments. S. salsa has succulent leaves and is highly salt tolerant (e.g. its optimal NaCl concentration for growth is 200 mm). A series of S. salsa genes related to salt tolerance have been cloned and their functions tested: these include SsNHX1, SsHKT1, SsAPX, SsCAT1, SsP5CS and SsBADH. The species is economically important because its fresh branches have high value as a vegetable, and its seed oil is edible and rich in unsaturated fatty acids. Because it can remove salts and heavy metals from saline soils, S. salsa can also be used in the restoration of salinized or contaminated saline land.Scope Because of its economic and ecological value in saline agriculture, S. salsa is one of the most important halophytes in China. In this review, the value of S. salsa as a source of food, medicine and forage is discussed. Its uses in the restoration of salinized or contaminated land and as a source of salt-resistance genes are also considered. 相似文献
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China has the highest greenhouse-based production in the world. In 2010, the area of greenhouses devoted to vegetable production was estimated at 4.7 million ha. With the increasing costs of pest control, expanding pesticide resistance and the growing consumer concern regarding pesticide residues in fresh vegetables, a strong demand for applying non-chemical control methods is emerging in China. Biological control in the greenhouse environment is a viable alternative to pesticide use from both environmental and economic perspectives. Although we have only 17 cases of fully documented, successful biological control operations from China, involving 8 crops, 8 pest species and 14 species of natural enemies, the use of the biological control agents is much more widespread. There are 7 commercial companies and facilities producing 21 species of natural enemies, and most of them are available country-wide. Several of these employ a rearing system using artificial diets, and many now move to an integrated production system, including the mass production of the biocontrol agents, quality control, methods of long-distance transportation, release recommendations, and user feedback. While initially these systems relied on introduced natural enemies, they increasingly develop modified systems using native natural enemies. The increasing demand for pesticide-free, high quality vegetable produce year-round and the existing certification schemes make it very likely that the use of biocontrol agents will continue to increase in China. 相似文献
4.
Effects of roads and land use on frog distributions across spatial scales and regions in the Eastern and Central United States 下载免费PDF全文
David M. Marsh Bradley J. Cosentino Kara S. Jones Joseph J. Apodaca Karen H. Beard Jane Margaret Bell Christine Bozarth Derrick Carper Julie F. Charbonnier Andreia Dantas Elizabeth A. Forys Miran Foster Jaquelyn General Kristen S. Genet Macie Hanneken Kyle R. Hess Shane A. Hill Faisal Iqbal Nancy E. Karraker Eran S. Kilpatrick Tom A. Langen James Langford Kathryn Lauer Alison J. McCarthy Joseph Neale Saumya Patel Austin Patton Cherie Southwick Nathaniel Stearrett Nicholas Steijn Mohammad Tasleem Joseph M. Taylor James R. Vonesh 《Diversity & distributions》2017,23(2):158-170
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M. A. Burgess 《Biodiversity and Conservation》1994,3(2):126-136
Understanding the relationships between indigenous people and their threatened economic plants can aid the conservation effort on many levels. Understanding ethnic perceptions of the taxon is critical toin situ andex situ conservation projects and enhances the accompanying educational effort. Examples are discussed from the experience of a grassroots conservation group in southwestern United States, Native Seed/SEARCH. Four levels of economic plant vulnerability are examined among 1) wild-harvested plants, 2) husbanded wild plants, 3) domesticates, and 4) wild relatives of domesticates. Legal interpretations of endangered husbanded and domestic plants are discussed, and further documentation encouraged. Genetic dynamism of threatened indigenous crops is examined and the concept of Systems Conservation (i.e. the plant/human interactive systems) is introduced. Guidelines are offered for incorporating better cultural responsibility intoex situ conservation strategies. The concept of Biocultural Restoration is introduced with an example from an O'odham community. Examples are given of ways indigenous peoples and their knowledge can assist in the conservation effort. 相似文献
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Environmental Stewardship (ES) is the main mechanism for reversing the decline in farmland birds in England, and includes a range of options designed to provide winter foraging for seed‐eating species. We estimated granivorous songbird densities on ES options designed to provide winter food, on farms within the Entry Level (ELS) or Higher Level (HLS) strata of ES. ES Wild Bird Mixtures (WBMs) hosted higher densities and a wider range of granivores than non‐ES game covers, although in East Anglia the enhanced HLS WBM was used no more than the basic ELS WBM. In the West Midlands there were low densities of granivores on all WBMs and game covers. The widespread ELS WBM appeared to provide little food for buntings but supported finches, partially through greater weed burdens. There was a weak, non‐significant trend for Skylarks Alauda arvensis to make greater use of ELS cereal stubbles than non‐ES stubbles, possibly because of post‐harvest herbicide restrictions allowing overwinter weed growth. At the field scale, this work demonstrates that although some ES options provide winter food resources for birds, there is limited evidence for additional benefits of Higher Level vs. Entry Level Stewardship to wintering farmland songbirds. 相似文献
10.
William Olupot 《Ostrich》2016,87(3):263-270
The Grey Crowned Crane Balearica regulorum was uplisted to globally Endangered in 2012. There is urgent need to determine the threats they face at local levels for their conservation. I conducted formal point-count surveys around the wetlands of eastern Uganda and observed no cranes. Groups of cranes were encountered when following directions from local inhabitants. Results from a questionnaire survey suggested that cranes make use of most of the wetlands in the region, and that the birds occur in small flocks averaging 6–8 individuals. Wetland loss through farming was reported to be the main threat, but I also documented poisoning, roost disturbance, and the collection of eggs and chicks. Rigorous conservation and education programs are needed to ensure the long-term survival of cranes and storks in this region. 相似文献