Ecosystem Ecology: Terrestrial Ecosystems

Ch. 20.2-20.3

what is an ecosystem

the biotic community and its abiotic environment, functioning as a system

examples of ecosystems

lakes, forests, tundra, tropical rain forests

what is ecosystem ecology

the study of natural systems with emphasis on energy flow and nutrient cycling

common types of ecosystem-level questions focus on ___________ and _____________

energy flow and nutrient cycling

what is primary productivity

the rate at which autotrophs convert carbon dioxide (in the atmosphere or water) into organic compounds

what is gross primary productivity (GPP)

total rate of photosynthesis (energy assimilated) by autotrophs

what is net primary productivity (NPP)

rate of energy story as organic molecules after energy is expended for cellular respiration (R)

NPP=

GPP - R

many environmental factors influence productivity in

terrestrial ecosystems

many environmental factors including __________ influence productivity in terrestrial ecosystems

climate

warm + wet =

high npp

warm + wet = high NPP

plants can photosynthesize quickly and have enough water

warm + dry =

low NPP

warm + dry = low NPP

warm temperatures increase water demand, but lack of water limits growth

cold =

low NPP (regardless of water)

cold = low NPP (regardless of water)

low temperatures slow down photosynthesis and growth

ecosystems with longer growing seasons have 

higher plant productivity

why do ecosystems with longer growing seasons have higher plant productivity

plants have more time to photosynthesize and produce biomass

the availability of essential nutrients also affects ecosystem productivity

more available nutrient → higher NPP

nutrients come from the

atmosphere or form rocks

nutrients enter the ______ or _______ and are absorbed by ________

soil or water and are absorbed by plants

many nutrients are stored in the

bodies of living organisms

when organisms die, those nutrients return to the

soil as dead organic matter, feeding decomposers

what is nutrient cycling

the mineralization of organic nutrient by microbial decomposers. these minerals are then available for the autotrophs to take up and use to build new tissues.

key decomposers include

fungi, bacteria, mites, springtails, millipedes, and earthworms

decomposition is influenced by

• quality of litter/OM

• soil/sediment properties (ex. pH)

• climate (temperature/precipitation)

climate and nutrient availability don’t just affect how much plants grow

it also affects what kinds of plants can grow

what are biomes

biotic units that are classified by predominant plant types

there are how many major terrestrial biomes

8

characteristics of tropical rainforest biome

• equatorial zone

• warm

• wet year-round

• high NPP

• dense vegetation

• high biodiversity

• nutrients are mostly stored in living plants, not soil

tropical rainforests cover less than ____% of earth’s surface

2

tropical rainforests are home to an estimated ___% of all terrestrial species

50

tropical rainforests are the most _______ and ________ terrestrial ecosystems on our planet

diverse and productive

plant growth forms found in rain forests include

climbing vine, epiphytes, and strangler figs

many trees grow buttresses

that function as prop roots in shallow soil that offers poor anchorage

many trees grow buttresses that function as

prop roots in shallow soil that offers poor anchorage

characteristics of tropical savanna biome

• warm

• semiarid regions

• seasonal rainfall (wet + dry season)

• high NPP

• drought resistant plants (shrubs and trees)

• fire-maintained ecosystem

  • diversity of herbivores that graze on vegetation

tropical savana supports a large number of

insects, carnivores (lions and hyenas), and scavengers (vultures)

savannas have a two-layer _______ _______

vertical structure (grasses + trees/shrubs)

in savannas, trees create small ___________

microenvironments

what are microenvironments

“resource hotspots” that support biodiversity than the surrounding grassland

characteristics of tree microenvironments

• soil is richer (more leaf litter and nutrients)

• shaded ground is cooler

• soil holds more moisture

characteristics of temperate deciduous forest biome

• moderate temperature + rainfall

• broadleaf deciduous trees dominate

• rich soils and understory of shrubs, ferns, wildflowers

• moderate NPP

• seasonal changes affect plant growth and animal behavior

in deciduous forests, there are usually _______ vertical layers

four

a diversity of anima life is associated with

vertical stratification and plant growth forms

highest diversity in the forrest occurs

on and just below the ground layer

characteristics of temperate grassland biome

• moderate temperature

• low precipitation

• often experience drought

• low to moderate NPP

• dominated by herbivores, insects, large grazers, burrowing animals

grasslands evolved under the __________ __________ of grazing

selective pressure

grasslands evolved under the selective pressure of 

grazing

grazing stimulates primary production to a point,

moderate grazing can stimulate grass growth, but heavy grazing reduces productivity

temperate grassland productivity is related to

annual precipitation

there are ______ strata in a grassland

3

what are the three strata in a grassland

• herbaceous plants

• ground cover

• belowground root layer

  • can make up more than half of the plant biomass and extends deep into the soil

characteristics of shrubland biome

• hot, dry summers

• cool, wet winters

• shrubs and dwarf trees dominate

• soils are deficient in nutrients

• plants are adapted for fire and low nutrients

• moderate NPP

sclerophyllous plants are characteristic of _______ _____

shrubland biomes

what are sclerophyllous plants

thick, tough, and leathery leaves with a waxy coating that helps reduce water loss

shrublands are home to ______-_______ mammals, birds, and reptiles that use shrubs for food and shelter

drought-tolerant

shrublands are home to drought-tolerant mammals, birds, and reptiles that use shrubs for

food and shelter

characteristics of desert biomes

• low precipitation

• hot (sahara)

• cold (gobi)

• high evaporation rates

  • dry conditions

• plants/animals adapt to very arid climate

• low NPP

hot deserts range from those lacking vegetation to ones with

some combination of herbs, dwarf shrubs, and succulents

in hot deserts, animals avoid heat and ______ ________

conserve water

cold deserts range from vegetation dominated by

sagebrush, shadscale, woody shrubs, and grasses adapted to cold, dry conditions

cold deserts range from vegetation dominated by sagebrush, shadscale, woody shrubs, and grasses adapted to

cold, dry conditions

animals in cold deserts conserve ____ and survive long dormant seasons

heat

characteristics of boreal forest (taiga) biome

• cold long winters

• around 6-10 weeks warm enough to photosynthesize

• dominated by evergreen conifers

  • needles prevent water loss

  • conical shape sheds snow

• primarily occupies formerly glaciated land

• low NPP

herbivores found in the boreal forest

caribou, moose, snowshoe hare, red squirrels, and procupine

predators found in the boreal forest

wolf, lynx, pine martin, and owls

as temperatures decreases and growing seasons shorten toward the Arctic,

trees become fewer, shorter, and more widely spaced

characteristics of the tundra biome

• very cold

• very low precipitation

• dominated by

  • small shrubs

  • grasses

  • herbs

  • mosses

  • lichens

• low animal diversity

• dominant vertebrates are herbivores

• very low NPP

in the tundra, only species that can withstand ______________ can survive

constant soil disturbance

arctic plants propagate almost entirely by

vegetative means