In cool temperate, humid, maritime environments, a dense cover of low shrubs with small tough leaves is interspersed with grasses and ferns. Cold temperatures and low-fertility acid soils limit productivity, with wet subsoils limiting decomposition so that organic matter accumulates. Low intensity fires may occur in the warmer months. Browsing mammals, such as rabbits and deer, bring nutrients from more productive systems and maintain the shrubby composition. Canids and raptors are common predators of ground-nesting birds and rodents, in a relatively simple foodweb.