ABSTRACT

A complex landscape lies on an alpine plateau in the high Sierra Nevada, California, and comprises spatially organized physical and ecological features that interact to create a unique ecosystem. At the upslope end a tree-limited ribbon forest of whitebark pines grows on the crest of a short, steep slope, which is the only deformation on the otherwise flat plateau. A long-persistent snowbank forms on the slope in the lee of the ribbon forest; meltwater provides moisture to support a productive wet meadow just below. Below the meadow is a narrow, linear “rampart” comprising large sorted stones, and below this lies a large patterned-ground area of cryogenically sorted circles. The soil domains are densely covered with species-rich vegetation and are abruptly segregated from stone domains. The latter serve as distributed springheads in the otherwise dry patterned-ground terrain. American pikas have colonized the rocky nets of the stone domains and forage plants of the soil circles. The unusual context of this landscape enables pika territories to be more tightly packed than in traditional habitat. We propose a scenario for the Pleistocene origin of this ecosystem and a unique lithologic subsurface barrier that contributes to spring formation during warm intervals.

摘要

复杂的景观位于加利福尼亚州内华达山脉的高山高原上，由空间组织的物理和生态特征组成，它们相互作用以创建独特的生态系统。在上坡的尽头，在一个短而陡的斜坡的顶部生长着一片树木限制的带状白皮松林，这是原本平坦的高原上唯一的变形。在带状森林背风处的斜坡上形成了一个长期存在的雪堤；融水提供水分，以支持下方多产的潮湿草地。草地下方是一个狭窄的、线性的“城墙”，由大块分选的石头组成，下面是一个大的有图案的地面区域，由低温分选的圆圈组成。土壤域被物种丰富的植被密集覆盖，并突然与石域隔离。后者在原本干燥的有图案的地面地形中充当分布的源头。美国鼠兔已在石域的岩石网和土壤圈的饲料植物中定居。这种景观的不同寻常的环境使鼠兔的领地比传统栖息地更紧密。我们为该生态系统的更新世起源提出了一个方案，以及一个独特的岩性地下屏障，有助于在温暖的间隔期间形成春季。