Environmental Problems, Their Causes, and Sustainability 1

with sunlight available only 6–8 hours a day in thenorthernmost taiga. Summers are short, with mild towarm temperatures (Figure 6-28, right), and the suntypically shines 19 hours a day.Most boreal forests are dominated by a few speciesof coniferous (cone-bearing) evergreen trees such asspruce, fir, cedar, hemlock, and pine that keep some oftheir narrow-pointed leaves (needles) all year long.This adaptation also allows the trees to take advantageof the brief summers without having to take time togrow new needles. Plant diversity is low because fewspecies can survive the winters when soil moisture isfrozen.Beneath the stands of trees is a deep layer of partiallydecomposed conifer needles and leaf litter. Decompositionis slow because of the low temperatures,waxy coating of conifer needles, and high soil acidity.As the conifer needles decompose, they make the thin,nutrient-poor soil acidic and prevent most other plants(except certain shrubs) from growing on the forestfloor (Figure 4-27, bottom right, p. 75).These biomes contain a variety of wildlife, as depictedin Figure 6-32. Trace the flow of energy and nutrientsin this diagram. During the brief summer thesoil becomes waterlogged, forming acidic bogs, ormuskegs, in low-lying areas of these forests. WarblersBlue jayGreathornedowlBalsam firMartenMooseWhitespruceWolfBebbwillowPine sawyerbeetleand larvaeFigure 6-32 Natural capital:some components and interactionsin an evergreen coniferous(boreal or taiga) forest ecosystem.When these organisms die,decomposers break down theirorganic matter into minerals thatplants use. Colored arrows indicatetransfers of matter and energybetween producers, primaryconsumers (herbivores),secondary, or higher-level, consumers(carnivores), and decomposers.Organisms are notdrawn to scale.StarflowerProducerto primaryconsumerSnowshoeharePrimaryto secondaryconsumerBacteriaFungiSecondary tohigher-levelconsumerBunchberryAll producers andconsumers todecomposers124 CHAPTER 6 Climate and Terrestrial Biodiversity