Lecture 2The physical environment and the

earth’s biomes

Principles of EcologyEben Goodale

College of Forestry, Guangxi University

Today’s class

• The physical environment– Climate– Chemical factors

• A tour of the world’s biomes• How to read a scientific paper

Chapters 2 and 3 of the textbook

What we know about ecology is always changing

• Our definition of ecology from last time:Ecology is the science probing connections (or interactions) between organisms and their abiotic and biotic （无机） environment.

• Today we are going to concentrate on the abiotic (physical) environment…– Sounds simple. But even our knowledge about the

abiotic environment is changing…

What we know about ecology is always changing

• Case study for Chapter 2 (the physical environment): the Pacific Decadal Oscillation (PDO) （太平洋十年动荡） .

• Discovery came through finding repeated patterns in the abundance of salmon in （鲑鱼） Northern Pacific.

1925 1980

AmtOf Catch

What we know about ecology is always changing

• PDO: Now thought to be a major influence on climate over 18 year time intervals( 时间间隔 ). One reason why climate change predictions currently too high?

Climate （气候）Climate is the long term description of weather at any particular place.•Major determinants （决定因素）•Global scale•Regional scale•Seasonal and long term variations

Extremes (minimum, maximum) important as well as average.Why?

Picture shows die-off of pine trees after drought

Climate: major determinants• Solar radiation 太阳辐射 and where it goes

Note the importance of atmosphere （大气层） in regulating temperature of earth

100

Absorbed by surface: 49

Infrared radiation from surface

Back radiation

Atmosphere

Hadley cells:Predictable areas of high, Low atmospheric pressure （低气压）

Tropics get more direct irradiance

Difference in irradiance drive global weather patterns

Hadley cells,polar cellsform bands of with different climates

Difference in irradiance drive global weather patterns

LOW PRESSURE (WET)

30° HIGH PRESSURE – DRY

Creation of wind patterns

• Winds go from high pressure to low pressure. • Earth’s rotation makes paths appear curved

If you did international trade before 1900, need to know your winds!

Creation of ocean currents （洋流）

• Ocean currents are created by surface winds

Dover EnglandHigh lat (51°N)Warm current7-21 °C

Consider that Harbin has Latitude of 46°!

Creation of ocean currents• Ocean currents are created by surface winds• Also winds create vertical （垂直）

movement known as upwelling （上升流）

Upwelling producesNutrient rich waters

Global temperature influenced by latitude, ocean currents, topology

• Land holds heat less well than water seasonal variation （季节性波动） higher in the interior of continents （内陆） .

• Higher elevation （海拔） colder. Why?– Atmosphere warmed mostly by infrared radiation

（红外线） emitted off surface of ground.– Temperature of atmosphere decreases with

distance from ground.– Further, at high elevations, fewer air molecules to

absorb infrared energy.

Patterns of atmospheric pressure and topography influence precipitation （降

水）

LOW PRESSURE (WET)

30°DRY

Regional influences

• How close to ocean?• How nearby, what sides

of mountains?

A mountain’s rain shadow （地形雨）

Vegetation changes climate, too.

• Deforestation （采伐森林） changes energy, water transfer.– Grassland absorb less solar radiation.– But, evapotranspiration （蒸腾作用） (return of

water from plants) is lower, returning less precipitation, and making warmer.

Climate variation （气候变化） : seasonal

The tilt of the earth’s axis underlies the seasonal changes in climate

Check it yourselfUsing a flashlight and a ball!

Climate variation: seasonal

• Oceans freeze less than fresh water because of salinity （含盐分） .

• Freshwater lakes have “turnover” event

Climate variation: multi-annual （多年一次） oscillations

El Niño•Change in where high pressure cells are in Pacific ocean, off South America•Trade winds disrupted•Leads to buildup of hot water; decrease in upwelling. •La Niño: opposite effects. •Transitions happen every 3-6 years; once started good predictions for 6-9 months, but hard to predict when starts

Climate variation: multi-annual oscillations

• El Niño– Immense changes– Poor fishing off SA– Dry conditions in Indonesia,

Australia leads to fire; La Niño leads to fires in N America

– May trigger mass flowering of the Dipterocarps, the dominant timber trees of SE Asia.

As we talked about in Case Study, PDO another oscillation, longer time scale, and even less understood

Climate variation: long term oscillations

• 10,000 yrs: ice ages• Million yrs: regular

oscillations between warm and cold periods.

Last glacial maximum: 18,000 yrs ago

600 mya 300 2

Climate variation: long term oscillations

• Mechanisms (known as Milankovitch cycles):Changes in shape of earth’s totation; changes in tilt, angle of

orientation

Today’s class

• The physical environment– Climate– Chemical factors

• A tour of the world’s biomes• How to read a scientific paper

Chemical environment: salinity

• Salinity is important for organisms to regulate the amount of water vs. particles in their internal fluids (blood for animals).

• Varies in oceans• Can build up in fresh water in arid areas; salt in soil

produced by irrigation or in maritime areas big problem for farming.

Floating in the Dead Sea

Salinization（盐碱化）In California

Chemical environment: acidity

• Acidity （酸度） has important effects on enzymes.

• Can naturally range in soil/water due to rock base.

• Important to fertility of soil.• CO2 buildup may change acidity of water

Chemical environment: oxygen

• Oxygen fairly invariant across earth currently.• But some areas such as deep underneath

water, or in certain soils, has “anoxic” conditions.

• Early in history of life, no oxygen. Slowly been produced by living organisms.

Anaerobic bacteria(do not use oxygen for metabolism)In a sea trench

A tour of the ecological biomes（生物群落） of the world

(Material from Chapter 3)

Biomes

Biomes are “large-scale biological communities” shaped by different climates.

Temperature

Precipitation (Rainfall)

Biomes

Biomes are “categorized by the dominant life forms of plants. Why?

Forbs

Needle-leafedEvergreen trees

Schlerophyllous(tough leaves)schrubs

Deciduoustrees

Grasses andsedges

Cacti and succulent shrubs

Evergreen broad-leaved trees

Our world tour

Clim

Climate chart

Temp(blueline)

Rainfall(redline)

Tropical Rainforests

• Very high diversity• Poor soils (high rate of decomposition （分

解） ) ~400,000 kg biomass per ha50 ha plot in Lambir (Malaysia) has 1175 tree species

Tropical Rainforests

• Complex structure

Deforestation （森林砍伐） not as great as in other biomes, but continuing andb ig price, as biodiversity so high.

Jianfenglin Forest Reserve in Hainan

Tropical Seasonal Forests and Savannahs

Often trees lose leaves during dry periodsMay have regular fires

One of most threatened biomes because of high population pressure

Taklimikan Desert

Deserts

• Blooms during short wet periods• Amazing adaptations （适应性） of plants to

these conditions demonstrate evolutionary（进化） convergence.

Cactus N America Euphorb S Africa

Temperate grasslands

• Grass continued by browsing animals, fires

Threatened by large amount of agriculture.

Temperate Shrublands （灌木） and Woodlands

• Mediterranean climate （地中海气候） : warm, hot summer and cool, wet winter.

Surprisingly diverse biome, threatened by agriculture, urbanization

Temperate Forest

• Biggest areas in China, Europe, US

Temperate Evergreen forests

• Conifer-dominated forests• Include temperate rainforests

Boreal forests （北方针叶林）• Also known as taiga

(Russian word)• Low diversity forests with

low decomposition.

Tundra

• Permafrost （永久冻土） , low light, cold stops growth of trees.

Mountainous areas

• Decrease in temp of 6.4°C for every 1000 m.• Hence, dramatic shifts in communities within

short distances.

Our biome tour can be done in China!

• Take, for example, Yunnan Province

Himalayans near Lijiang “Hot Dry Valley” in central Yunnan

Tropical rainforests ofXishuangbanna

What biome dowe have here inGuangxi?

Freshwater systems

• Streams, rivers• Importance of speed of

water: faster river more dissolved oxygen.

• Changes from headwaters to estuaries

Large changes due to pollution, divergence of water and damming.Colorado River doesn’t reach the sea!

Freshwater systems

Lakes-Importance of depth (reduction in light)

Threatened by pollution, irrigation

The disappearing Aral Sea

1973

1995

Marine systems

• 97% of earth’s water in the oceans.

• Distinguish between near-shore areas, shallow ocean, and open ocean （公海） (“pelagic”).

Photic(0-200m)

Near-shore marine communities

Mangrove forests （红树林）

Salt marshes （盐碱滩） Estuaries （河口）

Near-shore marine communitiesRocky intertidal zones

Sandy shores

Regular tidal changes producedifferent communities

Swallow sea communitiesCoral reefs（珊瑚礁）

The topical rainforests of the seas with remarkable diversity.

Coral reefs highly threatened by over-harvesting.“Coral bleaching” due to warming waters and stress increasing.

Swallow sea communities

Kelp （海藻） beds

Open ocean

• Narrow “photic” zone (0-200 m), 80% of light gone by 10 m.

• Rest of ocean relies on nutrients falling from photic zone and has less high diversity.

A submersible vehicle to explore sea trench

Deep sea fishPhyto-plankton: base of oceanic foodchain

Reading a scientific paper

Why do we want to read the scientific literature?

• Reading primary literature is how scientists identify questions, keep up with their field.

• This literature can be “intimidating （吓人的）” (scary)!

• But the process can be broken down into several steps: title, abstract, figures, and then discussion and introduction.

First steps

• The title is what you usually search for.• http://www.gfsoso.com/scholar/• Abstract is a mini-summary of the whole

paper. (1-2 sentences from each of traditional parts of a paper: introduction, methods, results, discussion).

Figures

• Read the axes （轴线） !

• Think about the relationship show. As you increase X axis, how does Y change?

• Try to describe the general message of the figure in 1 sentence.

Ways to remember your reading

• Write a reading report. As well as a summary, include your opinions about the paper (strengths, weaknesses).

• Keep an excel file with a 1 sentence recap of each paper.

Discussion: the Kiesecker paper

3 ponds with pesticide

ponds without

pesticide

%LimbDeform

Mass Of Frog

Black bars represent condition inwhich frogs exposed to Riberiroia

What were thecontrols for this experiment?

For pesticide, the control was….

For effect of the worm, the control was….

Homework

• Review: Lecture 2 notes.• Primary literature: Rutz et al. 2010 on New

Caledonian crows using tools. Prepare to discuss next week!

• Problem solving: http://sites.sinauer.com/ecology3e/problem02.html

Key concepts

• Climate is the central feature of the physical environment that affects living organisms.

• Variation in solar radiation in different places and over time produce the different climates and seasonality.

• The physical environment also varies chemically (salinity, acidity, oxygen)

• Biomes are broad categories of communities that allow us to understand the diversity of climates and vegetation in a simple way.

• Reading a scientific paper is a skill that mastered allows you a better window into the scientific world.