Pattern and Process in Northern Rocky Mountain Headwaters: Ecological Linkages in the Headwaters of the Crown of the Continent¹

Abstract

The Crown of the Continent is one of the premiere ecosystems in North America containing Waterton‐Glacier International Peace Park, the Bob Marshall‐Great Bear‐Scapegoat Wilderness Complex in Montana, various Provincial Parks in British Columbia and Alberta, several national and state forest lands in the USA, and Crown Lands in Canada. The region is also the headwater source for three of the continent’s great rivers: Columbia, Missouri and Saskatchewan that flow to the Pacific, Atlantic and Arctic Oceans, respectively. Headwaters originate in high elevation alpine environs characterized by high snow accumulations in winter and rainstorms in summer. Most headwaters of the region contain high quality waters with few ions in solution and extremely low nutrient concentrations. Alpine streams have few species of aquatic organisms; however, they often possess rare species and have hydrogeomorphic features that make them vulnerable to climatic change. Subalpine and valley bottom streams of the Crown of the Continent Ecosystem (CCE) flow through well forested watersheds. Along the elevation gradient, the streams and rivers of the CCE flow through series of confining and nonconfining valleys resulting in distinct canyon and floodplain reaches. The alluvial floodplains are characterized by high species diversity and bioproduction maintained by the hydrologic linkages of habitats. The streams and rivers of the CCE have low nutrient concentrations, but may be significantly affected by wildfire, various resource extraction activities, such as logging or mining and exurban encroachment. Wildfire has been shown to increase nutrient loading in streams, both during a fire and then following the fire for as much as 5 years. Logging practices increase nutrient loading and the algal productivity of stream periphyton. Logging and associated roads are also known to increase sediment transport into Crown of the Continent streams directly affecting spawning success of native trout. The CCE is one of the fastest growing regions in the USA because of the many recreational amenities of the region. And, while the region has many remarkably pristine headwater streams and receiving rivers, there are many pending threats to water quality and quantity. One of the most urgent threats comes from the coal and gas fields in the northern part of the Crown of the Continent, where coal deposits are proposed for mountain‐top removal and open‐pit mining operations. This will have significant effects on the waters of the region, its native plants and animals and quality of life of the people.

Seasonal variation of allochthonous and autochthonous energy inputs in an alpine stream

“…Mean chlorophyll a values were in the range of what reported in other studies regarding mountain lotic systems (Hauer et al, 2007), but slightly lower compared to values reported by LodsCrozet et al (2001) for a Swiss glacial stream at the same altitude. Seasonal patterns of chlorophyll a presented a time-lag compared to what reported for glacial-fed streams, where the lowest values of chlorophyll a are in the summer (July and August) when, despite elevated light availability, high temperatures favour ice melt which in turn increases fine particulate transport, shear stress, abrasion and turbidity (Uehlinger et al, 1998;Rott et al, 2006;Uehlinger et al, 2010, Bona et al, 2011.…”

Climate change links fate of glaciers and an endemic alpine invertebrate

“…Glaciers and permanent snow sources will soon disappear in WGIPP (Hall and Fagre 2003). These changes in the hydrological cycle will warm perennial streams and some may transition to ephemeral flows (Hauer et al 1997), thereby threatening the stability of sensitive alpine ecosystems that provide critical habitat for L. tumana and other alpine-restricted stream invertebrates, such as the rare caddisfly Allomyia bifosa (Hauer et al 2007). In some cases, however, reduced meltwater from snow and ice masses may favor a more diverse suite of species adapted to warmer temperature regimes (Ward 1994), resulting in increased local (alpha) diversity (Brown et al 2007).…”

“…Cold-water stenothermic species inhabiting alpine stream environments are especially vulnerable to warming and snow loss (Brown et al 2007), yet little is known about such species in glacier-fed streams in the Rocky Mountains of North America (Hauer et al 2007). Aquatic invertebrates may be useful biological indicators of climate-induced changes in aquatic ecosystems because they are integral components of aquatic food webs and their distributions and abundances are strongly influenced by temperature and stream flow gradients (Milner et al 2001;Hauer and Resh 2006;Jacobsen et al 2009).…”

Influence of groundwater spring discharge on small‐scale spatial variation of an alpine stream ecosystem

“…Aquatic ecosystems in alpine environments may act as sensitive indicators to hydrologic changes brought about by changes in climate and land use (Hauer et al, 1997(Hauer et al, , 2007Rott et al, 2006). Changing climatic patterns may influence the balance of water inputs (rain, snow melt, glacier melt, condensation) and outputs (evaporation, transpiration, sublimation, river runoff, groundwater outflow), including changes in the magnitude and seasonality of stream flows (Barnett et al, 2005).…”