The text begins with an introduction to alpine ecosystems.
Alpine environments are here described as those that exist above
timberline, a rather rich concept in itself as five different
kinds of timberline are listed: forest limit (physiognomic
forest line), economic forest line (above which trees cannot be
economically harvested), tree limit (the elevation above which
some species reach tree size), tree species limit (the elevation
above which tree species are stunted but present, i.e.
krummholz, elfinwood or krupelkiefer), and historic tree line
(indicating earlier climatic regimes). The Alpine Flora of the
Rocky Mountains is limited to those species growing above the
elevation where more or less continuous trees are found (tree
limit), trees being defined as arborescent species 3 m or more
in height. A few geomorphic processes such as nivation,
solifluction, and frost action are then briefly outlined. Next
follows a compact but informative discussion of alpine
environments. The general introductory materia