Evolution of river systems as plants colonized the land

古生代的“绿化”的陆地表面作为维管植物殖民景观是在所有地球历史上最深刻的进化变化。早古生代至中古生代的海洋和大气事件与陆地植被的扩张有着广泛的联系，这减少了大气中的二氧化碳，促进了全球变冷，增加了营养物质流入海洋，并导致海洋生物灭绝。然而，令人惊讶的是，古生代的河流几乎没有出现在这些讨论中，尽管早期的陆生植物在许多河流平原上定居。有限的先前研究表明，当河流平原是无植被的，渠道淹没了沿海地区的沙子，但蜿蜒的河流与泥泞的洪泛区出现在志留纪的植被稳定河岸。目前的研究计划旨在通过关键的寒武纪到泥盆纪间隔（5.4亿至3.6亿年前）记录河流沉积物，将事件的时间与已知的早期植物的首次出现和丰度进行比较。在文献汇编之后，将在北美和欧洲的选定地点对河流沉积物和世界上最早的一些植物组合进行研究。在较年轻的石炭纪岩石中，我们正在研究山区内河流盆地的植物，以评估植物何时蔓延到具有挑战性的内陆地区：然而，它们似乎从最早的日子就在那里。我们还将探索野火的早期证据，微生物对河流平原的贡献，以及一旦植物足够大和丰富，促进通道转换的原木堵塞。

The Paleozoic "greening" of the terrestrial surface as vascular plants colonized the landscape was among the most profound evolutionary changes in all of Earth history. Oceanic and atmospheric events during the early to mid Paleozoic have been widely linked to the spread of land vegetation, which decreased atmospheric CO2 , promoted global cooling, increased the runoff of nutrients to the oceans, and caused marine organisms to become extinct. Surprisingly, however, Paleozoic rivers barely feature in these discussions, even though early terrestrial plants colonized many river plains. Limited previous research suggests that, when river plains were unvegetated, channels inundated coastal areas with sand, but meandering rivers with muddy floodplains appeared in the Silurian as vegetation stabilized river banks. The present research programme aims to document river deposits through the crucial Cambrian to Devonian interval (540 to 360 million years ago), comparing the timing of events with what is known about the first appearances and abundance of early plants. Following a literature compilation, studies of river deposits and some of the world's earliest plant assemblages will be carried out at selected sites in North America and Europe. In younger Carboniferous rocks, we are studying the plants of river basins within mountain belts, in order to assess when plants spread into challenging inland areas: it seems, however, that they were there from the earliest days. We will also explore early evidence for wildfires, microbial contributions to river plains, and log jams that promoted channel switching once plants were sufficiently large and abundant.