SFB 1211: Earth - Evolution at the Dry Limit

水是宜居地球的决定性特征；正如我们所知，它是所有生命所必需的。地球上大部分地区都是在极度缺水的环境中生活，人们对这种环境下的生命进化还不是很了解。与生命类似，水驱动的过程在地球表面留下了独特的印记。火星是已知的唯一一颗有水驱动表面过程痕迹的行星，尽管它是化石，而且年代久远。即使在几乎没有液态水的情况下，也可能发生的缓慢的地表过程基本上是未知的。显而易见的是，在极度缺水的环境中，短暂的水供应增加会留下持久的痕迹。有趣的是，这些地球表面进化的爆发痕迹很少与生物殖民化/进化的爆发有关，反之亦然，尽管两者都与同一个触发因素有关：水。第二阶段的研究目标是深化地球表面过程与生物群相互演化关系的开创性研究。目标地区是干旱到极度干旱的系统，在这些系统中，生物群和地球表面过程都受到水供应的严重和主要限制。在第一阶段，我们专注于阿塔卡马沙漠，在第二阶段，我们想扩大我们的研究领域，包括纳米布沙漠；来比较地球上两个最古老的沙漠的进化轨迹。在第一阶段取得的进展的基础上，我们的目标是在可居住地球的（水）极限下分离出生物活动的关键指纹，并表征在（虚拟）缺乏液态水的情况下运行的地球表面过程。我们的目标是描述生物定植和河流景观同步转变的阈值，确定生物和非生物控制的地球表面系统的临界点，并建立地球上最古老和最干旱地区的详细长期陆地气候记录。生物区系定殖和辐射的时间和空间信息将与景观演变及其共同驱动因素：气候有关。在第二阶段，我们的目标是建立统一的景观和生物共同进化的数字和概念模型，并研究适应干旱环境的共同遗传性状。

Water is the defining feature of the habitable Earth; it is essential for all life as we know it. Evolution of life in extremely water-limited environments, which cover significant portions on Earth, is not well understood. Akin to life, water-driven processes leave unique marks on the Earth’s surface. Mars is the only other planet known to bear the marks of water-driven surface processes, albeit fossil and of great age. The slow surface processes that may operate even in the virtual absence of liquid water are essentially unknown. What is evident is that transient episodes of increased water availability leave long-lasting traces in extremely water-limited environments. Intriguingly those traces of bursts in Earth-surface evolution have rarely been related to bursts in biological colonization/evolution, and vice versa, although both relate to the same trigger: water. The objective of the CRC Earth – Evolution at the Dry Limit in the proposed second phase is to deepen the pioneering research on the mutual evolutionary relationships between Earth-surface processes and biota. The target areas are arid to hyper-arid systems, where both biota and Earth-surface processes are severely and predominantly limited by the availability of water. In the first phase we focussed on the Atacama Desert, in the second phase we want to expand our research area to include the Namib Desert; to compare the evolutionary trajectories of the two oldest deserts on Earth. Building on the progress made in the first phase we aim to isolate the key fingerprints of biological activity at the (water) limit of the habitable Earth, and to characterize the Earth-surface processes operating in the (virtual) absence of liquid water. We aim to characterize thresholds for biological colonization and concurrent fluvial transformation of landscapes, identify the tipping point(s) of biotically and abiotically controlled Earth-surface systems, and establish detailed long-term terrestrial climatic records of the oldest and most arid zones on Earth. Chronometric and spatial information on the colonization and radiation of biota will be related to the landscape evolution and their common driver: climate. In the second phase we aim to build unified numeric and conceptual models of landscape- and biological co-evolution, and investigate common genetic traits for adaptation to arid environments.