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。     

Managing the pattern of forest harvest: lessons from wildfire

Managing forests for sustainable use requires that both the biological diversity of the forests and a viable forest industry be maintained. A current approach towards maintaining biological diversity is to pattern forest management practices after those of natural disturbance events. This paradigm hypothesizes that ecological processes will be maintained best where active management approximates natural disturbance events. The forest management model now used in most sub-boreal and boreal forests calls for regularly dispersed clearcuts no greater than 60–100 ha in size. However, the spatial characteristics of the landscape produced by this model are distinctly different from the historic pattern generated by wildfire, which was heretofore the dominant stand-replacing process in these forests. Wildfire creates a more complex landscape spatial pattern with greater range in patch size and more irregular disturbance boundaries. Individual wildfires are often over 500 ha but leave patches of unburned forest within them. The combination of these attributes is not present in recent clearcuts. Allowing a proportion of larger (i.e.>500ha) harvest units may provide distinct economic advantages that could outweight the opportunity costs of leaving some patches of forest behind. For the forest type examined, further evaluation of modelling forest harvest patterns more closely after the patterns created by wildfire is required as it may achieve a good balance and strike a suitable compromise between certain ecological and economic objectives of sustainable development.     

Transgenic white clover. Studies with the auxin-responsive promoter,GH3, in root gravitropism and lateral root development

We report an improved method for white clover (Trifolium repens) transformation usingAgrobacterium tumefaciens. High efficiencies of transgenic plant production were achieved using cotyledons of imbibed mature seed. Transgenic plants were recovered routinely from over 50% of treated cotyledons. Thebar gene and phosphinothricin selection was shown to be a more effective selection system thannptII (kanamycin selection) oraadA (spectinomycin selection). White clover was transformed with the soybean auxin responsive promoter, GH3, fused to the GUS gene (-glucuronidase) to study the involvement of auxin in root development. Analysis of 12 independent transgenic plants showed that the location and pattern of GUS expression was consistent but the levels of expression varied. The level of GH3:GUS expression in untreated plants was enhanced specifically by auxin-treatment but the pattern of expression was not altered. Expression of the GH3:GUS fusion was not enhanced by other phytohormones. A consistent GUS expression pattern was evident in untreated plants presumably in response to endogenous auxin or to differences in auxin sensitivity in various clover tissues. In untreated plants, the pattern of GH3:GUS expression was consistent with physiological responses which are regarded as being auxin-mediated. For the first time it is shown that localised spots of GH3:GUS activity occurred in root cortical tissue opposite the sites where lateral roots subsequently were initiated. Newly formed lateral roots grew towards and through these islands of GH3:GUS expression, implying the importance of auxin in controlling lateral root development. Similarly, it is demonstrated for the first time that gravistimulated roots developed a rapid (within 1 h) induction of GH3:GUS activity in tissues on the non-elongating side of the responding root and this induction occurred concurrently with root curvature. These transgenic plants could be useful tools in determining the physiological and biochemical changes that occur during auxin-mediated responses.     

Dynamic properties of the advertisement calls of gray tree frogs: patterns of variability and female choice

We assessed the potential for several acoustic properties ofthe advertisement calls of male gray tree frogs to affect relativemating success by relating patterns of variation in these propertiesto minimum differences required to elicit female choice. Dynamicproperties (pulse number, PN; call rate, CR; and duty cycle,DC, the ratio of call duration to call period) varied much morewithin bouts of calling than a static property (dominant frequency,DF) but nevertheless exhibited significant between male variationin three of four breeding seasons. Many multiply recorded malesconsistently produced calls with values substantially aboveor below mean values of males recorded on the same nights. Nightlyranges of variation in PN and CR were often greater than theminimum differences required to elicit female preferences inthe laboratory. In most experiments, females chose high-PN orfast-CR calls over low-PN or slow-CR alternatives, respectively,even if the preferred stimuli were farther away or 6-10 dB lowerin sound pressure level (SPL), provided that differences inPN or CR were 100%. Consistent with these results, females didnot always choose the closer of two calling males in the field.Nightly ranges of variation in DF rarely equaled the minimumdifference required to elicit SPL independent preferences. Femalespreferred a stimulus of high-PN and slow-CR over an alternativeof low-PN or fast-CR with the same acoustic on-time; in twoexperiments, females chose calls of high-PN over low-PN alternativeseven though the playback of the high-PN call was interruptedand the low-PN call was broadcast continuously. Thus, femalepreferences were not merely based on the total time of acousticstimulation. Responses of females tested twice in the same experimentsuggest that phenotypic variation in preference was limitedin our study populations.     

龙血树真菌群及其对血竭形成的影响

从柬埔寨龙血树（Ｄｒａｃａｅｎａｃｏｃｈｉｎｃｈｉｎｅｎｓｉｓ）茎杆中分离到３０３株真菌,其中镰刀菌属（Ｆｕｓａｒｉｕｍ）菌株占总分离频率的５２％,其次是短梗霉（Ａｕｒｅｏｂａｓｉｄｉｕｍ）和枝孢霉（Ｃｌａｄｏｓｐｏｒｉｕｍ）。通过活体接种对血竭产生的影响试验表明,对血竭形成起重要作用的真菌主要是禾谷镰刀菌龙血树变种（Ｆ．ｇｒａｍｉｎｕｍｖａｒ．ｄｒａｃａｅｎａ）等４株红色镰刀菌,可使血竭形成量提高６６％－１２０％。     

甜玉米籽实含糖量的配合力分析

采用不完全双列杂交设计研究了 6个母本3个父本甜玉米自交系籽实含糖量的配合力效应。结果表明,父母本一般配合力和特殊配合力效应均方都显著。根据各亲本的表现把亲本5033归为一般配合力高而特殊配合力方差大的最理想类型;亲本5012和5011属一般配合力高而特殊配合力方差小的类型;亲本5018、5034、5028和5024为一般配合力低,但特殊配合力方差高的类型; 亲本5023和5009属一般配合力效应和特殊配合力方差都低的类型,最缺少实用价值。     

西藏厚厉螨属一新种和毛绥螨属一新种(蜱螨亚纲:厚厉螨科,裂胸螨科)

本文报道革螨二新种,西藏厚厉螨Pachylaelapsxizangensissp．nov．和亚东毛绥螨Lasioseiusyadongensissp．nov,1985年采自西藏亚东。     

雕盾螨属一新种记述（蜱螨亚纲：巨螯螨科）

本文记述雕盾螨属一新种;吴氏雕盾螨采自吉林省白城的土壤和马粪中。模式标本保存于全国鼠疫布氏菌病防治基地。     

北京东灵山地区植物群落多样性研究 Ⅹ.不同尺度下群落样带的β多样性及分形分析

选取不同尺度,采用β多样性指数和分形分析方法对东灵山暖温带森林样带上群落多样性随海拔梯度的空间变异规律进行了研究。结果表明,１）Ｃｏｄｙ指数揭示出乔木层在取样尺度２０ｍ和灌木层在取样尺度８０ｍ时,随海拔梯度变化呈明确的物种替代规律性;乔木层和灌木层在同一地点的物种替代速率具有互补性;群落多样性的空间变异在样带的起始（山底）和终止（山顶）地段较高。２）笔者提出的群落结构变异（ＣｏｍｍｕｎｉｔｙＳｔｒｕｃｔｕｒｅＶａｒｉａｔｉｏｎ,ＣＳＶ）指数介于０～１之间,作为Ｃｏｄｙ指数的改进,它对群落多样性沿环境梯度变化的揭示更接近于实际情况;ＣＳＶ指数分析显示乔木层在＞４０ｍ取样尺度,灌木层＞２０ｍ取样尺度群落结构出现明确变异规律;物种丰富度（Ｃｏｄｙ指数）和群落结构（ＣＳＶ指数）变化规律性的表现尺度（取样尺度）不同。３）分形分析的结果,乔木主林层在２００ｍ内不同尺度间不存在相关规律,乔木更新层只在＜４０ｍ尺度显示出尺度依赖性,灌木层的尺度依赖特征则表现为小尺度变异显著而较大尺度上变异程度降低;乔木更新层与灌木层的异质性规律发生显著变化（拐点）的尺度不同,分别为４０ｍ和９０～１００ｍ。同时,还对群落学研究中的取样尺度问题进行了探讨。     

小麦根区的化感物质及其生物活性的研究

小麦根区的化感物质及其生物活性的研究ＳＴＵＤＹＯＮＴＨＥＡＬＬＥＬＯＣＨＭＩＣＡＬＳＰＲＯＤＵＣＥＤＢＹＢＡＣＴＥＲＩＡＡＮＤＦＵＮＧＩＩＮＲＨＩＺＯＳＰＨＥＲＥＡＮＤＴＨＥＩＲＢＩＯＡＣＴＩＶＩＴＹ马瑞霞刘秀芬袁光林孙思恩ＭａＲｕｘｉａＬｉｕＸｉｕ...