内蒙古锡林郭勒草原不同固氮植物的固氮酶活性季节变化

 本文对内蒙古锡林郭勒典型草原栗钙土地带8种植物根瘤固氮酶活性的季节变化进行了测定。结果表明：1．不同种植物固氮酶活性表现了明显的季节性变化,夏季最高,平均值达到529.6n·mol C2H4／min·g,秋季较低,而春季只有夏季的10%左右。2．不同种植物,其根瘤固氮酶活性变化有不同的特点,杂花苜蓿是8种植物中固氮酶活性一直最高的,而小叶锦鸡儿与沙棘在8种植物中根瘤固氮酶活性一直较低,扁蓿豆,沙打旺前期较低,后期相对较高。3．同种植物在不同季节固氮酶活性表现了明显差别。     

锡林郭勒草原景观多样性的时间变化

利用锡林郭勒草原典型区段的两个不同年代的遥感信息源,结合实地考察目视解释研究区１９７８年（ＭＳＳ）、１９９２年（ＴＭ）的卫片影像,得到研究两张不同时期的植被图,以植物群落做为确定景观单元的最主要因子,在ＡＲＣ／ＩＮＦＯ软件的支持下,通过景观元素空间格局的变化,进一步分析得出在１４ａ的时间进程中,研究区景观破碎花现象加剧,多样性指数增加,优势度指数下降,人类不合理的放牧利用、农田开展等经营活动,引起     

松嫩草原主要草本植物种间关系及其对水淹干扰的响应

为弄清草地植物种间关系对水淹干扰的响应,在松嫩平原羊草(Leymus chinensis)草地1998年部分遭受水淹的吉林省大安市三家甸子草场内,设置了经历不同水淹强度或水淹时间的样带,并通过种间关联分析及种间协变的秩相关分析对这些样带上植物的种间关系进行了比较研究．结果表明,水淹干扰对大多数植物种对的关联类型影响不显著,对种间协变的秩相关系数却有一定程度影响,而且不同种对之间的协变关系对水淹干扰的响应有较大差异,说明植物种间协变关系既受环境波动和干扰因子的影响。也取决于组成种对的植物种的生物生态学特性,其中主要是对土壤水分状况反应的差异．以组成群落物种的数量特征为基础的种间协变系数比仅仅根据物种出现与否的二元数据为基础的种间关联指数对于外界干扰的反应更为敏感．     

艾鼬气味对根田鼠社会行为和繁殖的影响

在实验室条件下 ,主要测定艾鼬 (Mustelaeversmanni)气味对根田鼠 (Microtusoeconomus)社会行为、繁殖特征及性激素水平作用的格局 ,并探讨艾鼬气味使根田鼠产生繁殖迟滞的机制。结果表明 ,艾鼬气味对根田鼠一般动作、探究、自我修饰及婚配行为的频次具有显著的抑制作用 (P <0 0 5 ) ,而对各种行为累积时间的作用则产生明显的性别差异。艾鼬气味可提高雄体及雌体一般动作及雌体亲密行为的累积时间 ;对雄体自我修饰行为 ,以及雌体攻击、探究及自我修饰行为的累积时间有显著的降低作用 (P <0 0 5 )。艾鼬气味能显著制约根田鼠对食物的摄入 (P <0 0 5 ) ,并使其体重显著 (P <0 0 1)降低。在艾鼬气味条件下 ,82 %的配对根田鼠产生显著的繁殖迟滞 ,其雄体附睾精子计数、雌体卵巢指数及胚胎重量极显著地减低 (P <0 0 1) ,相应地 ,雌体血清孕酮显著地提高 (P <0 0 1)。上述结果验证了本文提出的捕食风险使田鼠类动物产生繁殖迟滞的假设     

General aspects of the large branchiopod crustacean fauna of Mongolia

 The Gobi Steppe of Mongolia supports numerous temporary water bodies of various sizes. No accurate information is available on the factors that shape the structure of their fauna, partly because they have been regarded as less important environments than permanent lakes. This study represents the first comprehensive survey of the Recent large branchiopod fauna of Mongolia, which consists of at least 16 species. This faunal composition may have resulted from colonization through diversification in East Asia during the Cretaceous period of the Mesozoic era (ca. 135–65 My ago), and to some extent from immigration from Europe into Asia during the Cenozoic era. The distribution patterns of some geologically ancient taxa most probably reflect the ancient hydrosphere. Five new records from Mongolia are presented: three species of Anos-traca, Branchinectella media (Schmankewitsch, 1873), Chirocephalus mongolianus Uéno, 1940, and Chirocephalus sp. (undescribed); one Spinicaudata, Cyzicus sp. (undescribed); and one Laevicaudata, Lynceus sp. (undescribed). The three undescribed species are localized-endemic to the Gobi Steppe. The purpose of this paper is to draw attention to some of the scientific interest and value of ephemeral aquatic habitats in Mongolia, and to argue that hydrobiologists, water resource managers, and conservationists need to take greater interest in temporary habitats. Received: June 5, 2002 / Accepted: August 31, 2002 Mailing address: Daifukucho 5-13-1, Gifu-shi, Gifu 502-0934, Japan Acknowledgments Special thanks are due to Dr. Ján Brtek (Hornonitrianske Múzeum, Slovakia) and the late Dr. Denton Belk (U.S.A.) who initiated the first author into large branchiopod studies. We also thank Prof. Tatsuo Kira (Otsu, Japan) for giving us the opportunity to organize our project. In addition, we thank the staff of Kaze Travel Co., Ltd. [Tokyo/Yokohama/Osaka, Japan; Ulaanbaatar, Mongolia (Mongol Kaze Travel Co., Ltd.: MKT)] for making the travel arrangements. The present study could not have been successful without sponsorship from the Chunichi Shimbun Social Welfare Association (Nagoya/Gifu, Japan). The research team and many Mongolian laypeople provided advice and assistance in our fieldwork. Correspondence to:H. Naganawa     

香鼬、艾虎和大kuang的食物资源分割——来自稳定性同位素的证据(英文)

通过对高寒草甸生态系统内香鼬、艾虎和大kuang 3种食肉类稳定性碳和氮同位素比值(δ[13]C和δ[15]N)的测定,依据同位素的质量平衡原理和IsoSource软件计算得到：小型哺乳类在香鼬、艾虎和大kuang食谱中的分配比例分别为26.8%、27.0%和29.2%;雀形目成鸟的分配比例为22.3%、47.7%和69.1%;雀形目幼鸟为50.9%、25.6%和1.70%。3种食肉类的稳定性碳和氮同位素分布模式在二维空间上存在明显分割,由此说明,香鼬、艾虎和大kuang之间存在明显的食物资源分割现象,同时也反映了三者在高寒草甸生态系统内共存的基础。     

Sexual differences in microhabitat selection of breeding little bustards Tetrax tetrax: Ecological segregation based on vegetation structure

We examined sexual differences in patterns of vegetation structure selection in the sexually dimorphic little bustard. Differences in vegetation structure between male, female and non-used locations during reproduction were examined and used to build a presence/absence model for each sex. Ten variables were measured in each location, extracting two PCA factors (PC1: a visibility-shelter gradient; PC2: a gradient in food availability) used as response variables in GLM explanatory models. Both factors significantly differed between female, male and control locations. Neither study site nor phenology was significant. Logistic regression was used to model male and female presence/absence. Female presence was positively associated to cover of ground by vegetation litter, as well as overall vegetation cover, and negatively to vegetation density over 30 cm above ground. Male presence was positively related to litter cover and short vegetation and negatively to vegetation density over 30 cm above ground. Models showed good global performance and robustness. Female microhabitat selection and distribution seems to be related to the balance between shelter and visibility for surveillance. Male microhabitat selection would be related mainly to the need of conspicuousness for courtship. Accessibility to food resources seems to be equally important for both sexes. Differences suggest ecological sexual segregation resulting from different ecological constraints. These are the first detailed results on vegetation structure selection in both male and female little bustards, and are useful in designing management measures addressing vegetation structure irrespective of landscape composition. Similar microhabitat approaches can be applied to manage the habitat of many declining farmland birds.     

Bird assemblages in pine plantations replacing native ecosystems in NW Patagonia

Forest plantations of exotic conifers represent an important economic activity in NW Patagonia, Argentina. However, there is a remarkable lack of information on the impact of forestry on native biodiversity. We analyzed the effect of Pinus ponderosa plantations on bird communities, considering different stand management practices (dense and sparse tree covers), and different landscape contexts where they are planted (Austrocedrus chilensis forest and steppe). Ultimately we wished to assess in which way plantations may be designed and managed to improve biodiversity conservation. Bird richness and abundance did not change significantly in the steppe, although community composition did, and was partially replaced by a new community, similar to that of ecotonal forests. In contrast, in the A. chilensis forest areas, species richness decreased in dense plantations, but bird community composition remained relatively constant when replacing the native forest with pine plantations. Also, in A. chilensis forest, stand management practices aiming at maintaining low tree densities permit the presence of many bird species from the original habitat. In the steppe area in turn, both dense and sparse plantations are unsuitable for most steppe species, thus it is necessary to manage them at higher scales, maintaining the connectivity of the native matrix to prevent the fragmentation of bird populations. We conclude that pine plantations can provide habitat for a substantial number of native bird species, and this feature varies both with management practices and with the landscape context of areas where afforestation occurs.     

Differences in the compensatory growth of two co-occurring grass species in relation to water availability

We compared the potential for compensatory growth of two grass species from the Mongolian steppe that differ in their ability to persist under grazing: the rhizomatous Leymus chinensis and the caespitose Stipa krylovii, and investigated how this ability might be affected by drought. Plants were grown in a greenhouse under wet and dry conditions and subjected to a clipping treatment (biweekly removal of 75–90% of the aerial mass). Leymus exhibited a much stronger compensatory growth after clipping than Stipa. Leymus showed a significant increase in its relative growth rate (RGR) after clipping, while for Stipa RGR was negatively affected. Clipped Leymus plants maintained leaf productivity levels that were similar to undamaged individuals, while leaf-productivity in clipped Stipa dropped to less than half of that of the controls. In Leymus, there was less compensatory growth under dry than under wet conditions, while in Stipa the compensation was increased under drought. This difference probably reflects the fact that Stipa is more drought-tolerant than Leymus. The greater compensatory growth of Leymus compared to Stipa mainly resulted from a greater stimulation of its net assimilation rate (NAR), and its greater capacity to store and reallocate carbohydrates by clipping. The greater increase in NAR was probably the result of a stronger reduction in self-shading, because Leymus shoots were much denser than those of Stipa, which resulted in a higher increase in light penetration to remaining leaves after clipping. The results of this study suggest that the greater ability of Leymus to persist under grazing is the result of its larger capacity for compensatory growth.     

盐胁迫对两种无芒雀麦种子萌发的影响

 在实验室中对两种无芒雀麦本地种（Bromus inermis cv. Xilinguole）和引进种 (Bromus stamineus)种子在浓度为0.5%、1.0%、1.5%的Na₂SO₄、NaCl和MgCl₂ 3种单盐胁迫下进行发芽实验，结果表明：与对照相比，在以上3种盐胁迫下，随着胁迫浓度的增加，两种无芒雀麦种子的发芽率、发芽指数和发芽值均有不同程度的降低，相对盐害率升高，种子开始发芽的时间推迟且其发芽过程延长；在3种盐中，NaCl的胁迫对两种植物种子萌发的抑制作用最大，其中浓度为1.0% NaCl的胁迫对引进种和本地种无芒雀麦发芽率的抑制分别达到了68.67%和14%，在浓度为1.5%的NaCl胁迫下两种供试植物的发芽率均为零；通过建立不同盐分处理与两种无芒雀麦种子发芽率之间的回归方程得出，引进无芒雀麦种子芽期的耐盐性较本地无芒雀麦强。