恐怖的黑沼泽

<正>小河溪流部干了,一道道黑沟交织分布在干沼泽里,宛如大地裂开的皮肤我们乘坐的汽车,以每小时5公里的时速在坑坑洼洼的草原土路上蹒跚而行。这是通往曼日玛乡智合桃大队夏季草场的必经之路,沿着黄河行进了不久,土路折转,进入山地草场。绕过一个又一个山头,突然之间,车窗外的景色突然发生了变化,展开了一幅罕见的画面:     

利用牧草生长-消费模型优化草场放牧方案

从理论上探讨了草场生态系统牧草的生长过程和消费过程,采用数学模型方法模拟了两者的动态变化规律,分析了两者在草场生态系统生态平衡中的作用机制．运用牧草的生长和消费模型模拟特定生产周期内草场生态系统的累积牧草消费量,提出优化的草场放牧方案。为实际生产提供参考依据．     

寻觅中华水塔的另一个侧面（二）——与扎多谈公路

我们的队伍是一路争论着走上高原的,有时争论到了剑拔弩张的程度。争论的内容包括：气候与人到底谁对草场退化的影响更大？城市与牧区的生活方式对于生态环境来说谁更合理？主流文化与多元文化应当是什么关系？尽是一些谁也不服谁的话题。尽管缺氧,吵起来气喘吁吁,大家还是热衷于讨论．动不动就宣布“开会!”或许是因为我们突然走进了一个截然不同的世界,     

一个属于牧民自己的合作社

洪格尔嘎查的一个村子位于内蒙古中部一片与外蒙古交界的半荒漠草原上．由于地理位置偏僻,这里受到农耕文化的影响较小。与内蒙古其他草原地区一样,这里在人民公社集体经济解体之后,也开始实行“草畜双承包”政策。牧民们分到了自己的牛羊和草场,盖上了砖瓦房,这一度提高了牧民们的生产积极性。然而．放牧面积小了,草场难以轮流休养生息,出现连年退化;单户牧民不得不以有限的劳动力应对繁重的劳动和自然灾害;而远离市场更使得他们被迫忍受商贩的盘剥;有钱的牧民用围栏保护了自家的草场,而无力设置围栏的牧民只好眼睁睁看着草场任由别人的牲畜践踏啃食。“草畜双承包”二十多年．草原出现了明显的退化．牧民经济也连年萎缩。     

对话蒙古马（二）——马倌寻访日记（二）

今天我们进入了东乌珠穆沁旗。听说那里保留着中国．甚至是世界上最好的草原。但是当我们看到第一群羊时．脚下却只有稀疏低矮的草和一片片裸露的砾石,这种场面让我们震惊。在和路边一个放羊的年轻人的聊天里．我们知道．这个地方已经很久没下雨了．草场一年不如一年．附近的牧民们凡是有门路的．都赶着自己的牲畜到别的地方租借草场,只有他因为家里没条件,还留在这儿。     

走进黑帐篷（二）

在与牧人们的接触中,我们不断听到感叹．就像佐瓦告诉我们的那样．在他们的概念里．有了野生动物的草场才算是好草场．自家牧场上有了野生动物就是好兆头。这种理念类似我们所说的“生物多样性”的概念,一个健康的系统必然是并存着多样的物种．维持平衡。而牧人们却是用了好兆头、好草场这种与他们的生活生计息息相关的说法表达这个规律。     

列措讲四季游牧的传统

过去的草原特别大,完全是游牧,走场都是部落头人发令．比如什么时候搬到夏季草场,牧户住在哪里没有规定。我们的部落叫宗据,沿着通天河都是我们的草场．冬天搬到河北岸,就是曲麻莱这边．春天还没开花的时候就回到南岸。那时候放牧是跟着牛羊走的．而不是把牲畜圈在一个地方．哪里草好哪里花好就去哪里,这样不光是为了好的草,     

吉林西部草原地区蚂蚁种类及分布

在吉林西部草原地区蚂蚁是大型土壤动物的优势类群,数量巨大,但种类少,仅发现3亚科9属14种。放牧场、撂荒地、农田、人工林、乡间土路、院落6种生境中分布最多的蚂蚁是红林蚁和铺道蚁,撂荒地和人工林的蚂蚁种类和巢口密度最大。在割草场分布的蚂蚁主要是玉米毛蚁、黄墩蚁和铺道蚁,它们均修建明显的地上蚁丘,蚁丘呈环带状分布,即主要分布在草地与碱斑的交界处,并且从草场边缘向中心,蚁丘的数量逐渐减少。利用拥挤度指数对蚁丘的分布格局进行分析,表明蚁丘呈聚集分布,并对可能影响蚁巢分布的因素进行了探讨。     

黄土峁状丘陵区天然草场类型及可持续利用研究

以黄土高原峁状丘陵区为对象,研究了该区各类草场生境特点及生态条件,探讨了该地区草场草种组成及生产力变化因素,根据典型样区草场物种及生镜,将本区草场资源划分为低湿地草甸草场、农田隙地草场、干草原草场、草甸草原草场及人工灌木草丛草场5个类型,并对其产量及载畜量进行了分析。结果表明：该地区低湿地草甸草场单位面积产草量最高,牧草质量好,但仅占总土地面积的0.5%左右。只能作为辅助草场;干草原草场面积最大,约占总土地面积的5.1%左右,但单位面积产草量较低,而人工灌木草丛草场群落总盖度70%左右,产草量3500kg/hm^2,载畜量最大,是该区主要草场。同时本文对天然草场的更新能力及人工改良技术进行了研究,提出了适草补种、轮封轮收、固定草场使用权等草场复壮措施。     

陕北天然草场的类型研究

对陕北天然草场的植物种类组成,地域分布和群体生产力进行了调查和分析,将本区草场资源划分为6个类型,干草原草场,草甸草原草场,草本半灌木草场,灌木草丛草场,低湿地草甸草场及农林隙地杂类草草场,根据各类草场利用中存在的问题,提出了合理开发和改良的措施。     

On the origin of the Hirudinea and the demise of the Oligochaeta

The phylogenetic relationships of the Clitellata were investigated with a data set of published and new complete 18S rRNA gene sequences of 51 species representing 41 families. Sequences were aligned on the basis of a secondary structure model and analysed with maximum parsimony and maximum likelihood. In contrast to the latter method, parsimony did not recover the monophyly of Clitellata. However, a close scrutiny of the data suggested a spurious attraction between some polychaetes and clitellates. As a rule, molecular trees are closely aligned with morphology-based phylogenies. Acanthobdellida and Euhirudinea were reconciled in their traditional Hirudinea clade and were included in the Oligochaeta with the Branchiobdellida via the Lumbriculidae as a possible link between the two assemblages. While the 18S gene yielded a meaningful historical signal for determining relationships within clitellates, the exact position of Hirudinea and Branchiobdellida within oligochaetes remained unresolved. The lack of phylogenetic signal is interpreted as evidence for a rapid radiation of these taxa. The placement of Clitellata within the Polychaeta remained unresolved. The biological reality of polytomies within annelids is suggested and supports the hypothesis of an extremely ancient radiation of polychaetes and emergence of clitellates.     

On the ontogeny of the haptor and the evolution of the Monogenea

Data on the ontogeny of the posterior haptor of monogeneans were obtained from more than 150 publications and summarised. These data were plotted into diagrams showing evolutionary capacity levels based on the theory of a progressive evolution of marginal hooks, anchors and other attachment components of the posterior haptor in the Monogenea (Malmberg, 1986). 5 + 5 unhinged marginal hooks are assumed to be the most primitive monogenean haptoral condition. Thus the diagrams were founded on a 5 + 5 unhinged marginal hook evolutionary capacity level, and the evolutionary capacity levels of anchors and other haptoral attachement components were arranged according to haptoral ontogenetical sequences. In the final plotting diagram data on hosts, type of spermatozoa, oncomiracidial ciliation, sensilla pattern and protonephridial systems were also included. In this way a number of correlations were revealed. Thus, for example, the number of 5 + 5 marginal hooks correlates with the most primitive monogenean type of spermatozoon and with few sensillae, many ciliated cells and a simple protonephridial system in the oncomiracidium. On the basis of the reviewed data it is concluded that the ancient monogeneans with 5 + 5 unhinged marginal hooks were divided into two main lines, one retaining unhinged marginal hooks and the other evolving hinged marginal hooks. Both main lines have recent representatives at different marginal hook evolutionary capacity levels, i.e. monogeneans retaining a haptor with only marginal hooks. For the main line with hinged marginal hooks the name Articulon-choinea n. subclass is proposed. Members with 8 + 8 hinged marginal hooks only are here called Proanchorea n. superord. Monogeneans with unhinged marginal hooks only are here called Ananchorea n. superord. and three new families are erected for its recent members: Anonchohapteridae n. fam., Acolpentronidae n. fam. and Anacanthoridae n. fam. (with 7 + 7, 8 + 8 and 9 + 9 unhinged marginal hooks, respectively). Except for the families of Articulonchoinea (e.g. Acanthocotylidae, Gyrodactylidae, Tetraonchoididae) Bychowsky's (1957) division of the Monogenea into the Oligonchoinea and Polyonchoinea fits the proposed scheme, i.e. monogeneans with unhinged marginal hooks form one old group, the Oligonchoinea, which have 5 + 5 unhinged marginal hooks, and the other group form the Polyonchoinea, which (with the exception of the Hexabothriidae) has a greater number (7 + 7, 8 + 8 or 9 + 9) of unhinged marginal hooks. It is proposed that both these names, Oligonchoinea (sensu mihi) and Polyonchoinea (sensu mihi), will be retained on one side and Articulonchoinea placed on the other side, which reflects the early monogenean evolution. Except for the members of Ananchorea [Polyonchoinea], all members of the Oligonchoinea and Polyonchoinea have anchors, which imply that they are further evolved, i.e. have passed the 5 + 5 marginal hook evolutionary capacity level (Malmberg, 1986). There are two main types of anchors in the Monogenea: haptoral anchors, with anlages appearing in the haptor, and peduncular anchors, with anlages in the peduncle. There are two types of haptoral anchors: peripheral haptoral anchors, ontogenetically the oldest, and central haptoral anchors. Peduncular anchors, in turn, are ontogenetically younger than peripheral haptoral anchors. There may be two pairs of peduncular anchors: medial peduncular anchors, ontogentically the oldest, and lateral peduncular anchors. Only peduncular (not haptoral) anchors have anchor bars. Monogeneans with haptoral anchors are here called Mediohaptanchorea n. superord. and Laterohaptanchorea n. superord. or haptanchoreans. All oligonchoineans and the oldest polyonchoineans are haptanchoreans. Certain members of Calceostomatidae [Polyonchoinea] are the only monogeneans with both (peripheral) haptoral and peduncular anchors (one pair). These monogeneans are here called Mixanchorea n. superord. Polyonchoineans with peduncular anchors and unhinged marginal hooks are here called the Pedunculanchorea n. superord. The most primitive pedunculanchoreans have only one pair of peduncular anchors with an anchor bar, while the most advanced have both medial and lateral peduncular anchors; each pair having an anchor bar. Certain families of the Articulonchoinea, the Anchorea n. superord., also have peduncular anchors (parallel evolution): only one family, the Sundanonchidae n. fam., has both medial and lateral peduncular anchors, each anchor pair with an anchor bar. Evolutionary lines from different monogenean evolutionary capacity levels are discussed and a new system of classification for the Monogenea is proposed.In agreeing to publish this article, I recognise that its contents are controversial and contrary to generally accepted views on monogenean systematics and evolution. I have anticipated a reaction to the article by inviting senior workers in the field to comment upon it: their views will be reported in a future issue of this journal. EditorIn agreeing to publish this article, I recognise that its contents are controversial and contrary to generally accepted views on monogenean systematics and evolution. I have anticipated a reaction to the article by inviting senior workers in the field to comment upon it: their views will be reported in a future issue of this journal. Editor