Definition: An alpine condition is an environmental condition in which the monthly mean temperature is less than 10 degrees Celsius and which occurs at altitudes above the tree line and below the snowline.
Definition: A shallow stretch of a river or stream, where the current is above the average stream velocity and where the water forms small rippled waves as a result. It often consists of a rocky bed of gravels or other small stones.
Definition: A habitat that is in or on a body of water containing low concentrations of dissolved salts and other total dissolved solids (<0.5 grams dissolved salts per litre).
