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121.
122.
Gotthilft von Studnitz 《Die Naturwissenschaften》1934,22(13):193-196
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Ökophysiologische Untersuchungen an Pflanzen der Namib-Wüste 总被引:1,自引:0,他引:1
D. J. von Willert E. Brinckmann B. Scheitler E. -D. Schulze D. A. Thomas S. Treichel 《Die Naturwissenschaften》1980,67(1):21-28
The southern Namib desert has a vegetation cover of mainly succulent plants in which species of the Mesembryanthemaceae are predominant. Climatically this area is characterized by hot and dry days, and cool and humid nights with episodic rainfalls only in winter. In this environment a great number of species perform a crassulaceaen acid metabolism (CAM). The responses of these plants to water stress as well as the regulation of CAM in the natural habitat are described and discussed. 相似文献
126.
C. L. Huffard S. von Thun A. D. Sherman K. Sealey K. L. Smith Jr. 《Marine Biology》2014,161(12):2735-2751
Pelagic forms of the brown algae (Phaeophyceae) Sargassum spp. and their conspicuous rafts are defining characteristics of the Sargasso Sea in the western North Atlantic. Given rising temperatures and acidity in the surface ocean, we hypothesized that macrofauna associated with Sargassum in the Sargasso Sea have changed with respect to species composition, diversity, evenness, and sessile epibiota coverage since studies were conducted 40 years ago. Sargassum communities were sampled along a transect through the Sargasso Sea in 2011 and 2012 and compared to samples collected in the Sargasso Sea, Gulf Stream, and south of the subtropical convergence zone from 1966 to 1975. Mobile macrofauna communities exhibited changes in community structure and declines in diversity and evenness within a 6-month time period (August 2011–February 2012). Equivalent declines in diversity and evenness were recorded in the same region (Sargasso Sea, 25°–29°N) in 1972–1973. Recent community structures were unlike any documented historically, whether compared to sites of the same latitude range within the Sargasso Sea, or the broader historical dataset of sites ranging across the Sargasso Sea, Gulf Stream, and south of the subtropical convergence zone. Recent samples also recorded low coverage by sessile epibionts, both calcifying forms and hydroids. The diversity and species composition of macrofauna communities associated with Sargassum might be inherently unstable. While several biological and oceanographic factors might have contributed to these observations, including a decline in pH, increase in summer temperatures, and changes in the abundance and distribution of Sargassum seaweed in the area, it is not currently possible to attribute direct causal links. 相似文献
127.
Erna von Heimburg Jon Ingulf Medbø Mariann Sandsund Randi Eidsmo Reinertsen 《International journal of occupational safety and ergonomics》2013,19(2):227-243
Aim. Firefighters must meet minimum physical demands. The Norwegian Labour Inspection Authority (NLIA) has approved a standardised treadmill walking test and 3 simple strength tests for smoke divers. The results of the Trondheim test were compared with those of the NLIA tests taking into account possible effects of age, experience level and gender. Methods. Four groups of participants took part in the tests: 19 young experienced firefighters, 24 senior male firefighters and inexperienced applicants, 12 male and 8 female. Results. Oxygen uptake (VO2) at exhaustion rose linearly by the duration of the treadmill test. Time spent on the Trondheim test was closely related to performance time and peak VO2 on the treadmill test. Senior experienced firefighters did not perform better than equally fit young applicants. However, female applicants performed poorer on the Trondheim test than on the treadmill test. Performance on the Trondheim test was not closely related to muscle strength beyond a minimum. Conclusion. Firefighters completing the Trondheim test in under 19 min fit the requirements of the NLIA treadmill test. The Trondheim test can be used as an alternative to the NLIA tests for testing aerobic fitness but not for muscular strength. Women’s result of the Trondheim test were poorer than the results of the NLIA treadmill test, probably because of their lower body mass. 相似文献
128.
Ben Vanpeperstraete Sébastien Duyck Medani P. Bhandari Janis Brizga Leida Rijnhout Sylvia Lorek A. Peter Castro Chiung Ting Chang Herman Daly Robert J. Didham Gianluca Ferraro Oliver Greenfield Ashok Khosla Ernst Ulrich von Weizsäcker Birgit Lode Simon Miles Henrique Pacini Semida Silveira Leisa Perch Jaap Rijnsburger Mukul Sanwal Sameera Savarala S. Jacob Scherr Kallidaikurichi E. Seetharam A.M.M. Adeeb Donna Shepherd Adrian Smith Lisinka Ulatowska Alice Vincent Werner John 《Natural resources forum》2011,35(4):334-342
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Oliver Behr Mirjam Knörnschild Otto von Helversen 《Behavioral ecology and sociobiology》2009,63(3):433-442
In many animal species, individuals compete for resources but avoid escalated conflicts by threat displays, i.e. a mutual
signalling behaviour that enables the opponents to predict the outcome of the conflict without the necessity of actual fighting.
For example, territory holders may use acoustic signals to communicate not only their own identity and the borders of their
territory but also their competitive quality, fighting ability and motivation. Here, we show that male sac-winged bats, Saccopteryx bilineata, adjust their vocal territorial displays according to the fundamental frequency of territorial songs of their opponents.
In playback experiments with territorial males, low-frequency stimuli elicited a higher territorial song rate and length than
high-frequency stimuli. Male S. bilineata that sing more often and with lower fundamental frequencies have been shown to sire more offspring than their competitors.
Fundamental frequency of territorial songs, hence, may reveal male quality and, consequently, the resulting threat posed to
competing males. We argue that this is reflected in the increased response of competitors to low-frequency territorial songs
shown here. Such competitive signalling behaviour has been shown in a few mammal species like red deer and baboons but, thus
far, not in bats.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献