Long-term vegetational history of a Picea abies stand in south-eastern Norway: Implications for the conservation of biological values     

Chiara Molinari  Ole Risbøl  Mikael Ohlson 《Biological conservation》2005,126(2):155-165

The development of a forest stand in south-eastern Norway during the last 9000 years is investigated by pollen and charcoal analyses. The aims are to identify factors that have influenced current biodiversity, which includes the lichen Usnea longissima, and examine the immigration and establishment of the current dominant tree Picea abies. Fire has been a variable but major disturbance factor at the site throughout the study period but has ceased during the last 100 years. Picea immigration was primarily a natural process but local establishment occurred after a major disturbance. Cultural impact began 3500 years ago during the Bronze Age, but was most intensive between AD 1600 and AD 1900. It led to the local extinction of deciduous trees and created a biodiversity bottleneck that facilitated the rise to dominance of Picea. Guidelines are proposed for future management designed to preserve and enhance local biological values.  相似文献   

Soil microbial tests for discriminating between different cropping systems and fertiliser regimes   总被引：1，自引：0，他引：1  

K. Svensson  Mikael Pell 《Biology and Fertility of Soils》2001,33(2):91-99

The aim of this study was to evaluate a set of microbial soil tests for their ability to discriminate between different agricultural practices. For this purpose three sites included in the Swedish Long-Term Soil Fertility Experiments were chosen. The fertility experiments were designed to compare different cropping systems (simulating farming with and without livestock), PK-fertiliser and N-fertiliser regimes. Six different microbial tests were used to derive nine variables describing: (1) basal microbial activity (B-res), (2) potential microbial activities (substrate induced respiration, SIR; potential NH₄ ⁺ oxidation, PAO; potential denitrification activity, PDA; and alkaline phosphatase activity, Alk-P), (3) specific microbial growth rates (μ _res and μ _PDA) and (4) nutrient-limited respiration rates (maximal P-limited respiration, Max-P; and maximal N-limited respiration, Max-N?). Among the individual microbial variables B-res, SIR, μ _res and μ _PDA were the best discriminators of the two different cropping systems. All of them, except μ _PDA, showed some degree of interaction between different treatments. However, the best discriminators between cropping systems were the components [principal component (PC)?1 and 2] from a PC analysis (PCA). In all three soils PC?1 discriminated well between the two cropping systems. In addition, PC?1 and PC?2 reflected the P-fertilisation rate. Max-P alone had the best potential to reflect the microbially available P in the soil and thereby indirectly the plant-available P. The μ _res was also useful when assessing available P in the soil. The N-fertilisation rate seemed to be the most difficult treatment to assess with the microbial activity variables. In addition, PCA revealed a consistent functional relationship in all three soils between the potential activity variables (SIR, PAO, PDA, and Alk-P).  相似文献   

The Asian tsunami: a protective role for coastal vegetation     

Danielsen F  Sørensen MK  Olwig MF  Selvam V  Parish F  Burgess ND  Hiraishi T  Karunagaran VM  Rasmussen MS  Hansen LB  Quarto A  Suryadiputra N 《Science (New York, N.Y.)》2005,310(5748):643

The 26 December 2004 Indian Ocean tsunami had major effects on coastal communities and ecosystems. An assessment of coastlines after the tsunami indicates that coastal vegetation such as mangroves and beach forests helped to provide protection and reduce effects on adjacent communities. In recent years, mangroves and other coastal vegetation have been cleared or degraded along many coastlines, increasing their vulnerability to storm and tsunami damage. Establishing or strengthening greenbelts of mangroves and other coastal forests may play a key role in reducing the effect of future extreme events.  相似文献   

Canine specific ELISA for coagulation factor VII     

Knudsen T  Kjelgaard-Hansen M  Tranholm M  Wiinberg B  Clausen JT  Hansen JJ  Nichols TC  Kjalke M  Jensen AL  Kristensen AT 《Veterinary journal (London, England : 1997)》2011,190(3):352-358

Canine coagulation factor VII (FVII) deficiency can be hereditary or acquired and may cause life threatening bleeding episodes if untreated. FVII procoagulant activity can be measured by FVII activity (FVII:C), but assays for measurement of canine specific FVII antigen (FVII:Ag) have not been available to date. In this study, a canine specific ELISA for measurement of FVII:Ag in plasma was developed and validated. The FVII:Ag ELISA correctly diagnosed homozygous and heterozygous hereditary FVII deficiency. Together with activity based assays, such as FVII:C, the FVII:Ag ELISA should be valuable in the diagnosis of hereditary canine FVII deficiency.  相似文献   

Out of Tibet: Pliocene woolly rhino suggests high-plateau origin of Ice Age megaherbivores   总被引：1，自引：0，他引：1  

Deng T  Wang X  Fortelius M  Li Q  Wang Y  Tseng ZJ  Takeuchi GT  Saylor JE  Säilä LK  Xie G 《Science (New York, N.Y.)》2011,333(6047):1285-1288

Ice Age megafauna have long been known to be associated with global cooling during the Pleistocene, and their adaptations to cold environments, such as large body size, long hair, and snow-sweeping structures, are best exemplified by the woolly mammoths and woolly rhinos. These traits were assumed to have evolved as a response to the ice sheet expansion. We report a new Pliocene mammal assemblage from a high-altitude basin in the western Himalayas, including a primitive woolly rhino. These new Tibetan fossils suggest that some megaherbivores first evolved in Tibet before the beginning of the Ice Age. The cold winters in high Tibet served as a habituation ground for the megaherbivores, which became preadapted for the Ice Age, successfully expanding to the Eurasian mammoth steppe.  相似文献   

Posttranslational modification of pili upon cell contact triggers N. meningitidis dissemination   总被引：1，自引：0，他引：1  

Chamot-Rooke J  Mikaty G  Malosse C  Soyer M  Dumont A  Gault J  Imhaus AF  Martin P  Trellet M  Clary G  Chafey P  Camoin L  Nilges M  Nassif X  Duménil G 《Science (New York, N.Y.)》2011,331(6018):778-782

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Disorder-enhanced transport in photonic quasicrystals     

Levi L  Rechtsman M  Freedman B  Schwartz T  Manela O  Segev M 《Science (New York, N.Y.)》2011,332(6037):1541-1544

Quasicrystals are aperiodic structures with rotational symmetries forbidden to conventional periodic crystals; examples of quasicrystals can be found in aluminum alloys, polymers, and even ancient Islamic art. Here, we present direct experimental observation of disorder-enhanced wave transport in quasicrystals, which contrasts directly with the characteristic suppression of transport by disorder. Our experiments are carried out in photonic quasicrystals, where we find that increasing disorder leads to enhanced expansion of the beam propagating through the medium. By further increasing the disorder, we observe that the beam progresses through a regime of diffusive-like transport until it finally transitions to Anderson localization and the suppression of transport. We study this fundamental phenomenon and elucidate its origins by relating it to the basic properties of quasicrystalline media in the presence of disorder.  相似文献   

Natural food and artificial,dry starter diets: effects on growth and survival in intensively reared European grayling     

Mikael Carlstein 《Aquaculture International》1993,1(2):112-123

Four artificial, dry feeds and two diets consisting of natural, live food were evaluated for use as starter diets in the intensive rearing of European grayling (Thymallus thymallus). Long-term effects of the different diets were also studied. The investigation was divided into two parts: a 14 day starter period and the subsequent 115 days, during which the long-term effects were studied. Diets differed between the different treatment groups during the initial 2 weeks, whereafter all fish were offered a single diet. At the end of the starter period, significant differences in weight (p<0.001) were obtained between natural (control) feed groups and three of the artificial feed groups. The highest growth rate (9.6% day^–1), and length increase (9 mm) as well as the lowest mortality rate (6.0%) were obtained with one of the artificial diets. Growth rate, length increase and mortality of grayling in the other diet groups varied from 3.6 to 7.7% day^–1, 5 to 7 mm and 7.0 to 9.1%, respectively. The switchover to a different dry diet resulted in an increase in mean daily mortality for all groups previously fed a dry diet. For the fish previously fed live food the mortality rate remained about the same. Groups of fish growing slowly during one period seemed to compensate for their initially low growth by increasing their growth rates during the next period. The highest mean daily mortality for all groups during the experiment was observed during the period with the highest water temperature. It was concluded that European grayling can be intensively reared during the start-feeding phase on artificial as well as natural diets, and that artificial dry diets can be used exclusively throughout the first summer.  相似文献   

The evolution of maximum body size of terrestrial mammals     

Smith FA  Boyer AG  Brown JH  Costa DP  Dayan T  Ernest SK  Evans AR  Fortelius M  Gittleman JL  Hamilton MJ  Harding LE  Lintulaakso K  Lyons SK  McCain C  Okie JG  Saarinen JJ  Sibly RM  Stephens PR  Theodor J  Uhen MD 《Science (New York, N.Y.)》2010,330(6008):1216-1219

The extinction of dinosaurs at the Cretaceous/Paleogene (K/Pg) boundary was the seminal event that opened the door for the subsequent diversification of terrestrial mammals. Our compilation of maximum body size at the ordinal level by sub-epoch shows a near-exponential increase after the K/Pg. On each continent, the maximum size of mammals leveled off after 40 million years ago and thereafter remained approximately constant. There was remarkable congruence in the rate, trajectory, and upper limit across continents, orders, and trophic guilds, despite differences in geological and climatic history, turnover of lineages, and ecological variation. Our analysis suggests that although the primary driver for the evolution of giant mammals was diversification to fill ecological niches, environmental temperature and land area may have ultimately constrained the maximum size achieved.  相似文献   

Phytostabilisation of a copper contaminated topsoil aided by basic slags: assessment of Cu mobility and phytoavailability     

Lydie Le Forestier  Mikael Motelica-Heino  Philippe Le Coustumer  Michel Mench 《Journal of Soils and Sediments》2017,17(5):1262-1271

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