Trees clustered together in the sub alpine stand a much better chance of surviving the harsh conditions. Called krumholtz, these tree islands are miniature ecosystems unto themselves, providing mutual protection against the elements while acting as a catch basin for moisture. A krumholtz provides habitat for lesser plant species as well as insects, birds and mammals big and small. Usually trees in the krumholtz, German for "crooked wood," are old if not ancient, stunted by a short growing season, harsh weather and a paucity of nutrient-rich soil. Branches tend to flourish on the downwind side only.