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551.
Darvishi Asef Yousefi Maryam Dinan Naghmeh Mobarghaee Angelstam Per 《Landscape Ecology》2022,37(1):305-327
Landscape Ecology - Evidence-based knowledge is crucial for place-based knowledge production and learning towards sustainable landscapes through stewardship and integrated spatial planning. We... 相似文献
552.
Anu Korosuo Per Sandström Karin Öhman Ljusk Ola Eriksson 《Scandinavian Journal of Forest Research》2014,29(7):234-251
In northern Sweden, the forests are used simultaneously for both timber production and reindeer husbandry. During the winter months, lichen is the most important fodder for reindeer. Forest management operations are generally considered having a negative impact on reindeer husbandry as harvesting and dense stands remove or obscure the ground lichen cover. In this study, we simulate three different scenarios for forest management, differing in the intensity and types of harvest operations. The resulting 100-year scenarios are analyzed with respect to their estimated suitability for providing reindeer pasture areas. Suitability is determined by vegetation type, stand density and stand height. The results indicate that the current trend of a decrease in lichen area will continue if existing forestry practice prevails. Implementing continuous cover forestry as a management alternative and carrying out precommercial thinning could halt the decrease in reindeer pasture area and even lead to a future increase in pasture area, with losses of approximately 5% in the net present value of forestry. 相似文献
553.
Fluxes and pathways of silicon in a marine rainbow trout cage farm were studied. The measured fluxes included those carried by fish food, juveniles, harvest, fish loss (death and escape), sedimentation from the cages, and benthic release measured with flux chambers in-situ. Two different types of Si mass balances for the farm were constructed. The mass balance according to the flux method was based on the measured fluxes and constructed for each of two consecutive growing seasons. The mass balance constructed according to the accumulation method was based on the total input and removal of Si to the cages of the farm since it was started, and the recovery of Si in the sediment originating from the farm. In both types of mass balances external input was the major source of Si, contributing a minimum of 55–80% of the total biogenic silica in the material collected in sediment traps below the farm and of the material accumulated in the farm-derived sediment. The Si removed from the farm with harvest contributed a very small part, 0.3%, of the amount of Si supplied to the farm with fish food and juveniles. The loss of Si to the environment was 2.4 kg (1985), 2.5 kg (1986) and 2.5 kg (1980–1986) for each ton of fish produced. On a seasonal basis, about 4.5% of the sedimented biogenic Si was returned in dissolved form from the sediment to the overlying water. This constituted about 0.3% of the biogenic Si content in the farm-derived sediment. The flux of reactive silicate from sediment below the fish farm was enhanced about 2.5 times compared to nearby sediments unaffected by the farm. 相似文献
554.
Trond Storebakken Per Foss Erland Austreng Synnøve Liaaen-Jensen 《Aquaculture (Amsterdam, Netherlands)》1985,44(4):259-269
Atlantic salmon (Salmo salar, L.), kept in sea pens were fed diets containing pure carotenoids. No significant preferential utilization of the (3S,3′S), (3R,3′S) or (3R,3′R) optical isomers of astaxanthin was observed. No epimerization occurred in the flesh at the chiral centres at C-3 and C-3′ in astaxanthin. 相似文献
555.
Dichelobacter nodosus, the etiological agent of ovine footrot, exists both as virulent and as benign strains, which differ in virulence mainly due to subtle differences in the three subtilisin-like proteases AprV2, AprV5 and BprV found in virulent, and AprB2, AprB5 and BprB in benign strains of D. nodosus. Our objective was a molecular genetic epidemiological analysis of the genes of these proteases by direct sequence analysis from clinical material of sheep from herds with and without history of footrot from 4 different European countries. The data reveal the two proteases known as virulent AprV2 and benign AprB2 to correlate fully to the clinical status of the individuals or the footrot history of the herd. In samples taken from affected herds, the aprV2 gene was found as a single allele whereas in samples from unaffected herds several alleles with minor modifications of the aprB2 gene were detected. The different alleles of aprB2 were related to the herds. The aprV5 and aprB5 genes were found in the form of several alleles scattered without distinction between affected and non-affected herds. However, all different alleles of aprV5 and aprB5 encode the same amino acid sequences, indicating the existence of a single protease isoenzyme 5 in both benign and virulent strains. The genes of the basic proteases BprV and BprB also exist as various alleles. However, differences found in samples from affected versus non-affected herds do not reflect the currently known epitopes that are attributed to differences in biochemical activity. The data of the study confirm the prominent role of AprV2 in the virulence of D. nodosus and shed a new light on the presence of the other protease genes and their allelic variants in clinical samples. 相似文献
556.
Transgenic sugar beet tolerant to glyphosate 总被引:4,自引:0,他引:4
Phenology (i.e. the influence of environment on ontogeny) is the most important single factor influencing crop adaptation. The timing of flowering is particularly important since it largely determines when annual cereal, pulse and oilseed crops will subsequently be ripe for harvest. Two environmental factors are of overriding importance in the induction of flowering – photoperiod (daylength) and temperature. In seeking to predict times from sowing to flowering, f, it has proved profitable to analyse photothermal responses in terms of the rate of progress from sowing to flowering, 1/f. This paper summarises the advantages of a model based on rates rather than the traditional approach based on f. Over a wide range of photothermal regimes, the model involves just six coefficients, all of which (and their derivatives) have clearly defined biological meaning. Of paramount importance too is that the coefficients are not affected by the environment; they are genetic characters which determine phenotypic responses to the environment in a quantitative and predictable way. 相似文献
557.
Growing a resilient landscape depends heavily on finding an appropriate match between the scales of demands on ecosystems by human societies and the scales at which ecosystems are capable of meeting these demands. While the dynamics of environmental change and ecosystem service provision form the basis of many landscape ecology studies, enhancing landscape resilience is, in many ways, a problem of establishing relevant institutions that act at appropriate scales to modify and moderate demand for ecosystem services and the resulting exploitation of ecosystems. It is also of central importance for landscape sustainability that institutions are flexible enough to adapt to changes in the external environment. The model provided by natural ecosystems suggests that it is only by encouraging and testing a diversity of approaches that we will be able to build landscapes that are resilient to future change. We advocate an approach to landscape planning that involves growing learning institutions on the one hand, and on the other, developing solutions to current problems through deliberate experimentation coupled with social learning processes. 相似文献
558.
Dorette Müller-St?ver Henrik Hauggaard-Nielsen J?rgen Eriksen Per Ambus Anders Johansen 《Biology and Fertility of Soils》2012,48(4):371-383
A laboratory incubation study with clover grass pasture soils of seven different ages (0, 1, 2, 3, 4, 5, and 16 production
years) was carried out to determine initial soil carbon (C) and nitrogen (N) stocks and potentials for greenhouse gas emissions
(N2O and CO2). Compared with the soil from the recently established pasture, an increase of total soil C and N was observed along with
pasture age. Greenhouse gas emissions were low and not significantly different among the soils from younger pastures (0–5 years),
but especially N2O emissions increased markedly in the soil from 16-year-old grass–clover. Low emissions might mainly be due to an early C
limitation occurring in the soils from younger pastures, which was also corroborated by decreasing levels of cold water-extractable
C and early shifts within the microbial community. However, higher emissions from the old pasture soil were offset by its
increase in total soil C. A longer ley phase without soil disturbance may therefore be beneficial in terms of overall C sequestration
in systems with temporary grass–clover swards. 相似文献
559.
Elevated nitrogen (N) deposition in humid tropical regions may aggravate phosphorus (P) deficiency in forest on old weathered soil found in these regions. From January 2007 to August 2009, we studied the responses of soil microbial biomass and community composition to P addition (in two monthly portions at level of 15 g P m?2 yr?1) in three tropical forests in southern China. The forests were an old-growth forest and two disturbed forests (mixed species and pine dominated). The objective was to test the hypothesis that P addition would increase microbial biomass and change the composition of the microbial community, and that the old-growth forests would be more sensitive to P addition due to its higher soil N availability. Microbial biomass C (MBC) was estimated twice a year and the microbial community structure was quantified by phospholipid fatty acid (PLFA) analysis at the end of the experiment. Addition of P significantly increased the microbial biomass and altered the microbial community composition in the old-growth forest, suggesting that P availability is one of the limiting factors for microbial growth. This was also reflected by significant increases in soil respiration after P addition. In contrast, P addition had no effect on the microbial biomass and the microbial community composition in the pine forests. Also in the mixed forest, the microbial biomass did not significantly respond to P addition, but soil respiration and the ratio of fungal-to-bacteria was significantly increased. 相似文献
560.
【目的】分析苦荞籽粒的化学成分,为进一步了解苦荞籽粒的次生代谢成分提供参考。【方法】采用试管法对苦荞籽粒化学成分进行系统预试,以工业乙醇为溶剂对其化学成分进行超声辅助提取,采用硅胶柱层析、聚酰胺柱层析和凝胶柱层析(Sephadex LH-20)对化合物进行分离,通过紫外-可见光谱法(UV)、红外光谱法(IR)、质谱法(MS)、核磁共振法(1 H NMR、13 C NMR)的综合分析结果对化合物结构进行鉴定。【结果】从苦荞籽粒中共分离得到10个单体化合物,其中5个分别被鉴定为伞形花内酯、槲皮素、山奈酚-3-O-芸香糖苷、(-)-表儿茶素和芦丁。【结论】苦荞籽粒中的主要化学成分为黄酮类化合物,伞形花内酯为首次从该植物中发现。 相似文献