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中国西南干热河谷萨王纳植被综述

Review on savanna vegetation in the dry hot river valleys of southwestern China

  • 摘要: 中国西南的深切河谷因“焚风”效应形成干热河谷,具有干热性气候和河谷型萨王纳植被。萨王纳植被的植物群落以禾草占绝对优势,形成背景,其间散生灌木和乔木,在外观上类似“稀树草原”。在生活型构成上,它们以高位芽植物为主(占总种数的48.0%),但地面芽植物(占23.3%)占比较高;在叶级谱上,小叶植物占总种数的42.5%,微叶植物占20.6%;在乔木树种中,复叶占乔木总种数的39.3%,表现出明显适应干旱生境的特征。西南干热河谷萨王纳植被的植物区系总体上以热带成分占优势,但不同的干热河谷萨王纳植被的植物区系在演化过程中受地质历史和自然地理的影响发生了明显的分化。在植物区系的相似性上,金沙江干热河谷与元江干热河谷属相似性为73.8%,种相似性为53.8%,在本文比较的西南干热河谷中具有最大的属、种相似性。研究发现,中国西南干热河谷萨王纳植被和植物区系在起源和演化上与自第三纪以来,伴随着喜马拉雅的隆升,在云南发生的主要地质事件密切相关。在其植物区系中,一些种类显示与印度和非洲的萨王纳植被有关联,这在一定程度上支持印度板块从非洲分离,筏运了部分非洲植物到亚洲的理论。 金沙江与元江干热河谷具有最高的属、种相似性,支持了金沙江曾流到元江,后来因河流袭夺改道的假说。怒江干热河谷植物区系中热带成分占绝对优势,这可能与印度板块向北推挤亚洲板块,缅甸北部随之发生了北移密切相关。这些地区发生的地质历史事件可以较好地解释西南干热河谷的植物区系组成、特征和分布格局。

     

    Abstract: The deep valleys in southwestern China experience a dry, hot climate and support savanna-like vegetation, largely shaped by the “foehn” effect. This vegetation is primarily dominated by grasses, interspersed with scattered shrubs and trees, resembling the physiognomy of savannas in other parts of the world. The savanna-like ecosystem hosts a rich diversity of species adapted to the dry, hot valley habitat, including many local endemic plants. In terms of life forms, phanerophytes dominate, accounting for 48.0% of the total species, while hemicryptophytes account for 23.3%. Regarding leaf characteristics, microphyllous and nanophyllous plants represent 42.5% and 20.6% of the total, respectively; among tree species, 39.3% have compound leaves, reflecting adaptations to arid habitats. The flora in the hot, dry valleys of southwest China are generally dominated by tropical elements, but are influenced by regional geological history and geography. Floristic similarity between the Jinshajiang and Yuanjiang river valleys is high, with 73.8% and 53.8% at the genus and species levels, respectively, representing the greatest similarity among the hot, dry valleys. The origin and evolution of this flora are closely related to major geological events in Yunnan since the Tertiary, including uplift of the Himalayas. Some species exhibit floristic affinities with the savannas of India and Africa, supporting the hypothesis that the Indian plate separated from Africa, collided with Asia, and transported African plants to the continent. The high generic similarity between the Jinshajiang and Yuanjiang river valleys supports the river capture hypothesis. In contrast, the savanna-like vegetation in the Nujiang River valley is dominated by tropical floristic elements, which is likely related to the northward push of the Indian plate into the Asian plate and the subsequent northward shift of northern Myanmar. These geological events help explain the floristic composition, characteristics, and distribution patterns of the savanna-like vegetation in the dry, hot valleys of southwestern China.

     

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