Hibernation behavior of Rana lessonae and R. esculenta in their natural habitat

We studied the hibernation behavior of the water frog Rana lessonae and its hybridogenetic associate R. esculenta in their natural habitat during three successive winters. Animals caught in pitfall traps at a fenced pond were individually marked with PIT tags and some (n=36) were additionally equipped with radio transmitters. Of the animals caught, 85% left the fenced pond for hibernation. More R. esculenta remained inside the fenced area compared to R. lessonae. R. lessonae emigrated earlier in autumn and came back later in spring than R. esculenta, but the distance to their hibernation sites did not differ. Both species left the fenced pond earlier in the year when ambient temperatures were lower. All radio-tracked animals hibernated in woodland, 3–7 cm below the surface in soil, under moss, fallen leaves or small branches. Soil temperatures at the actual hibernation sites were significantly higher than at randomly chosen control sites. A surprising finding was that most frogs changed their hibernation sites during winter, and often more than once. Movements were more frequent in the warmer first half of the winter than in the cooler second half, but some animals were active even on days with mean temperatures below 1°C. These results show that both species do not spend the whole winter torpid in one particular hibernation site but move around, especially at higher temperatures. Most of the animals lost weight during the winter, and the weight loss was greater in females than in males and higher in warm than in cold winters. To what extent weight loss and survival is influenced by the chosen hibernation sites and the amount of movement during winter, and whether this contributes to the differences in species and sex ratios found in mixed populations, needs more investigation. Received: 4 August 1999 / Accepted: 15 November 1999     

Initiation of early breeding in a population of Microtus townsendii (Rodentia) with the secondary plant compound 6-MBOA

Summary Feeding the secondary plant compound 6-Methoxybenzoxazolinone (6-MBOA) during winter to a free living population of Microtus townsendii accelerated breeding in females. Both the recruitment of young and sexual maturation of these young were advanced by four weeks in comparison with a control population. Overwintered females supplied with 6-MBOA matured at a lower body weight than control females. But there was no such weightat-maturity difference between the grids for males. During April and May 72% of all juveniles captured came from the experimental population. Winter reproduction and early recruitment of young stimulated by 6-MBOA could have important population consequences for these voles.     

冬小麦对不同海拔气候条件的反应 Ⅲ.植株光合作用特征

我们在原地测量了840米和2150米两地种植的冬小麦“凤麦13”苗期、拔节期、抽穗期和灌浆初期的光合作用速率的日变化,光合作用速率对光量子通量密度的反应和CO_2补偿点。结果表明生育前期(苗期和拔节期)和后期(抽穗期和灌浆初期)光合作用速率的一日内变化形式相反,而且低地种植的冬小麦其光合速率在前期高于高地种植的,后期高地种植的冬小麦有比低地高的光合速率。光饱和点基本相同。光补偿点在生育前期高地小麦比低地小麦低,而后期低地小麦的的光补偿点减低,并低于高地小麦的。高地小麦的光补偿点比较稳定。CO_2补偿点高地小麦比低地的较低。并就两地气候条件讨论了上述差异。     

The first born,their dispersal,and vole cycles

Summary On the basis of some empirical data and the existing theory of vole cycles, a new hypothesis is proposed. It explains cyclicity as an effect of obligatory dispersal of the first seasonal cohort of young (Y1) from their natal (optimal) habitats into vacant (suboptimal) habitats. This behaviour could evolve, because it increases contribution of genetic lineages with dispersing Y1, to subsequent generation. It is assumed that the dispersal of Y1 is common among vole species, it does not change during consecutive phases of the cycle, and it does not vary between cyclic and non-cyclic populations. It results in multiannual cycles only under a certain set of spatial and climatic conditions, which are discussed in a paper. Otherwise it results in annual dynamics.     

Association between dwarfing genes ‘Rht1’ and ‘Rht2’ and resistance toSeptoria tritici Blotch in winter wheat (Triticum aestivum L. em Thell)

Summary Differences in levels of resistance toSeptoria tritici blotch were observed in plants with a specific height-reducing gene. When the gene Rht ₂ was present either as an isoline or in the progeny, a higher degree of resistance was found. The most susceptible plants were observed in populations carrying the Rht ₁ gene. Associations, as determined by phenotypic correlations, were detected betweenSeptoria tritici blotch and tall stature, late heading, and maturity. Plants having short stature, early heading, early maturity, and acceptable levels of resistance were identified in the F₂ population whenRht ₂ was present. Results of this study indicated that wheat breeders must select the appropriate dwarfing source that may confer resistance and grow large F₂ populations, in order to increase the probability of obtaining desired genotypes.     

Seed transmission of turnip yellow mosaic virus in winter turnip and winter oilseed rapes

This is the first record of seed transmission of turnip yellow mosaic virus (TYMV) in oilseed and turnip rapes. The seed transmission of TYMV in a naturally infected winter turnip rape (Brassica napus var. silvestris) cultivar Perko PVH was investigated. By ELISA 1.6%, 3.2% and 8.3% seed transmission of the virus was found in seed of plants from three localities. The proportion of infected seeds produced by artificially infected plants of winter oilseed rape (Brassica napus ssp. oleifera) and winter turnip rape cultivars was determined. The virus transmission rate, expressed as the proportion of virus-infected plants which germinated from the seed was for the oilseed rape cvs Jet Neuf 0.1%, Solida 0.4%, Silesia 0.8%, Darmor 1.2%, SL-507 0.2%, SL-509 0.0% and for the winter turnip rape cv. Perko 1.5%. ELISA cannot be used in direct tests on bulk seed lots to estimate proportion of infected seed, but must be used on germinated seedlings.     

陕西佛坪国家级自然保护区羚牛的容纳量

陕西佛坪国家级自然保护区位于秦岭南坡的中段 ,1998～ 1999年冬季通过分层抽样的方法 ,测定了保护区内羚牛秦岭亚种 (Budorcastaxicolorbedfordi) 10种栖息地类型的单位面积食物资源量和含有的能量 ,估计了越冬区可以利用的总能量。结果表明 ,羚牛越冬区提供的可供羚牛和其它草食动物利用的能量为 (9 877±5 173)× 10 12 J,每只羚牛平均每天需要的能量为 2 6 4 8± 11 88kJ ,整个冬季需要的能量为 4 82 0± 2 16 3× 10 6J ,保护区的羚牛容纳量为 2 0 4 9± 10 37只。考虑到羚牛对空间的需求、保持最佳繁殖状态、其它草食动物种群的需求和保护当地植被等因素 ,建议保护区将羚牛种群的数量控制在 10 0 0只左右.     

紫貂冬季食性的分析

１９９１至１９９８年的三个冬季,在大兴安岭地区共收集紫貂粪样２２３个．食性分析结果表明,紫貂冬季食物主要为小型哺乳类（５４．１％）、植物浆果和种子（３２．４％）、鸟类（１２．５％）和昆虫（１．０％）．在紫貂选择的７种小型哺乳类中,主要以棕背（２７．３％）和红背（１９．２％）为食,其次为雪兔和冬眠的花鼠。对于鸟类,紫貂主要捕食花尾榛鸡（８．１％）,松鸦（０．７％）,大山雀（０．５％）和黑啄本鸟等。有２．２％的粪样中含有小型鸟的卵壳、紫貂的植物性食物主要为越桔浆果（２０．８％）和偃松种籽（８．８％）。昆虫中只有蚂蚁在紫貂食性中出现（１．０％）．紫貂冬季食物构成没有年度间差异（Ｐ＞０．０５）。通过捕食迹,我们还发现紫貂捕食黑嘴松鸡。虽然红背的捕获率（７９．４％）高于棕背（２．９％）,但食性分析结果却相反,说明紫貂更喜欢捕捉身体较大的鼠类。有较强气味的中虽有一定的数量,但在紫貂冬季食物中未出现过。     

Water potential gradients of tall and short cultivars of winter wheat

Summary Water and osmotic potentials were measured with thermocouple psychrometers, weekly after heading, two times each day at pre-dawn and at noon, in flag leaves and grain of tall and short cultivars of winter wheat grown in the field under rain-fed conditions.Water was held with less tension in the grain than in the leaf for both tall and short cultivars. The tall cultivars had lower leaf water potentials, but higher grain water potentials, than the short cultivars. The grain osmotic potential was lower in the short cultivars compared to the tall ones. Grain yield of short cultivars (1810 kg/ha) was more than that of tall cultivars (1730 kg/ha). Apparently higher leaf water potentials of short cultivars enabled more photosynthates to move into the grain.