An Ecology Teaching Notebook

By

Chen Zhang-He

March, 2004

Chapter Two: Life on Land

Terrestrial biomes

I. Soil and climate factors

II. Terrestrial main biomes

I. Soil and climate factors

1. Soil 2. Climate factors

1. Soil (1) Vertical structure: Fig. 2.3 O horizon: Upper layer contains loose,

somewhat fragmented plant litter; A horizon: Mineral soil mixed with some

organic matter. B horizon: Deposition horizon. Materials

leached from A horizon are deposited in B horizon.

C horizon: Weathered parent material. The horizon may include many rock fragments.

(2) Affecting factors on soil structure:

Climate: weathering, leaching, erosing and transporting of minerals, decomposing, etc.

Organisms: structure and texture, biological characteristics, etc.

Topography: water flow, erosion, etc. Parent material: physical, chemical and bi

ological characteristics, etc. Time: soil structure.

2. Climate factors: Seasonality Light: Intensity and day length (Fig.2.4). Temperature: Latitude: Average temp. decreases with latitudes. Longitude: Different daily and seasonal variations exist at different longitudes. Elevation: Average temp. decreases

with elevations. (Next fig.)

Fig. 2C1. Variation of air temperature with elevation

2004-8-30 　第二章 生物与环境

Precipitation: Latitude (Fig.2.5), Longitude, Elevation variation. (Next fig.)

Distribution of rainfall at different elevations and slopes.

2004-8-30 　第二章 生物与环境

Climate diagrams

Structure of climate diagrams The months are plotted on the

horizontal axis, beginning with Jan. and ending with Dec. for locations in the Northern Hemisphere and beginning with Jul. and ending with Jun. in the Southern Hemisphere.

Temperature is plotted on left vertical axis and precipitation on the right vertical axis. 10 oC is equivalent to 20mm precipitation on the vertical axes. For precipitation more than 100mm per month, scale is compressed as 200mm equivalent to 10 oC.

Relative positions of rainfall line and temperature line reflect water availability.

Representative climate diagrams of some different climate zones. (Fig. 2.8)

(2) Terrestrial main biomes

1. Tropical Rain Forest (Fig.2.9) Geography: Distributes in tropical humid area

s, mainly in Southeast Asia, West Africa, and South and Central America

(Fig. 2.10).

Climate: Temperature 25—27 ℃ with little annual and daily variation, annual rainfall 2000—4000mm, quite evenly distributes year round.

Soil: Organic matter is low, often nutrient poor, acidic and thin.

Biology: Trees are tall, about 40--80m, well-developed buttresses, high diversity, climbing vines, epiphytes, stranglets, etc. Fig.2-46, Fig.2-45, Fig.2-47, Fig.2-48.

Human Influences: Foods, building materials, drugs, hunting, shifting agriculture, etc. Fig.2-49.

2. Tropical Dry Forest (Fig. 2.12)

Geography: It distributes in both south and north of the central African rain forest, of the Amazon rain forest; and in India, Indochina peninsula. In Australia, it form a continuous band across the northern and northeastern portions (Fig. 2.13).

Climate: A wet season about 5-6 months and dry seasons about 6-7 months in a year, the rain season comes during the warmer part of the year (Fig. 2.13).

Soil: Great age, less acidic, rich in nutrients, vulnerable to erosion.

Biology: Tree height correlated with average precipitation, drop leaves during dry season. Animal-dispersed seeds are less than rain forest, and wind-dispersed seeds, more than rain forest. Share many animals with the rain forest and savanna.

Human Influences: Higher population density, fertile soil, easy to burn.

3. Tropical Savanna/Savanna: a tropical grassland dotted with scattered trees. (Fig. 2.15)

Geography: Occurring north and south of tropical dry forest within 10o to 20o of the equator (Fig. 2.16).

Climate: Generally drier than tropical dry forest, mean annual rainfall of about 300-500 mm, with a rhythm of alternating dry and wet seasons (Fig. 2.16).

Fire is a important physical factor in savanna.

Soil: Low permeability to water. Biology: Grass dominating, with scattere

d trees. Flora of fire resistance/adapted to fire. Rich in fauna: Elephant, wildbeest, giraffe, zebra, lion, kangaroo, bird, etc. Most of them migrate to respond to seasonal and year-to-year variation of food availability.

Human influences: Setting fire, hunting, gathering, livestock raising, etc.

4. DesertAn extremely dry and sparse vegetation

(Fig.2.50 )

Geography: distributing mostly on the Tropic of Cancer and Tropic of Capricorn (Fig. 2.19).

Climate: Annual rainfall generally <300mm, evaporation exceeds precipitation during most of the year. Great variation in temperature: very hot during summer and daytime; very cold during winter and nighttime.

Soil: Very low organic matter generally, but with great variation resulted from animal activities.

Salt accumulation in poorly drained areas and lowlands.

Biology: Plant cover is sparse or absent. Plant adaptations: covering with hairs,

dropping leaves during dry periods or no leaves at all, dormant during dry or cold periods, etc.

Animal adaptations: active at dusk

and dawn or at night in summer, or during days in winter, lessening water loss, etc.

Human influences: desert becomes worse, and increases its area because of human activities.

5. Temperate woodland and shrubland

Geography: Distributing on between 30o and 40o latitude, north of the subtropical deserts in the Northern Hemisphere, and south of the subtropical deserts in the Southern Hemisphere, most extensive around the Mediterranean Sea and in North America (Fig. 2.22).

Climate: Cool and moist during fall, winter and spring, usually hot and dry during summer.

danger of frost, but usually not severe, frequent and intense fires (Fig. 2.22).

Soil: generally low to moderate

fertility, easy to erosion, especially under fires and overgrazing.

Under careful stewardship, it can maintain for long period (thousands of years).

Biology: Trees and shrubs have evergreen, small, tough leaves, many plants can fix atmospheric nitrogen.

Many herbaceous plants grow during the cool, moist seasons, and die back in summer. Plants are well adapted to resistant to fire.

Animals: highly diverse, including resident and migratory species, which spend winter here.

Human influences: Impacts of human include: clearing of forests for agriculture, setting fires for controlling woody species and encouraging grass species, harvesting brush for fuel, grazing and browsing livestock, habiting of population, etc.

6. Temperate grassland (Fig. 2.24) Geography: A vegetation occupying the

central latitude. In North America, Eurasia, and in Argentina, Uruguay, southern Brazil, and New Zealand (Fig. 2.25)

Climate: Annual precipitation 300 –1000 mm, known as semi-drought areas. Wet season goes with the hotter season, winters are generally cold and summers hot.

Fires.

Soil: Deep, fertile, high % of organic matter, basic or neutral.

Biology: Plant, dominated by grasses and other herbs, height about 5cm to 20cm. Animal, huge herds of roving herbivores, social groups.

Human influences: Nomadic hunters, nomadic herders, farmers. The most fertile farmlands on earth and fed much of the world (Fig. 2.26).

Soil lost caused by agriculture.

7. Temperate forest: Forest in temperate humid area (Fig. 2.27)

Geography: Found between 30o—55o latitude, mainly between 40o—50o.

In Asia (Japan, eastern China, Korea, eastern Siberia), Western Europe, North America, Chile, New Zealand, South Australia (Fig. 2.28).

Climate: Annual precipitation about 650—3000mm (Fig. 2.28).

Deciduous forest, growth season is moist and more than 4 months.

Coniferous forest, winters are more severe or summer drier.

Soil: usually fertile, generally neutral or slight acidic, rich both in organic and inorganic matters

Coniferous forest can also grow in poorer soil.

Biology: Great height of trees about 40—70m, great biomass, diversity and vertical stratification simpler than tropical rain forest.

Animal, deer, bear, fox, etc. Fungi and bacteria (Fig. 2.29) Moss (Fig. 2.29)

Human influence: Once major population centers, settlement, agriculture, animal and plant products, etc.

8. Boreal forest: Forest made up by coniferous trees (Fig. 2.30)

Geography: Distributing on the Northern Hemisphere, forming a band between 50o—60oN (Fig.2.31). It is bounded in the south by temperate forest, and in north by tundra.

Climate: Long winter > 6 months; short summer, growth period < 120 days.

Precipitation, 200mm– 600mm, > evaporation, generally moist.

Soil: Low fertility, thin, acidic. Decomposition is low.

Biology: Plant, dominated by evergreen conifers, such as spruce, fir, tamarack, in some places, pine, larch. Structure is simple.

Animal, animals migrating for winters, such as migratory caribou (北美驯鹿 ) and reindeer (驯鹿 ). Animals habiting year-round, such as moose（鸵鹿） , woodland bison（野牛） . Wolf, bears, lynx（猞猁） , wolverine（狼爟） , snowshoe hare, porcupines（箭猪） , red squirrels, and many species birds.

Human influences: Harvesting for food (such as berries), hunting, trapping, cutting trees for lumber and pulp, etc.

9. Tundra: Vegetation around the arctic area (Fig. 2.33)

Geography: Covering most of the lands north of the Arctic Circle (Fig. 2.34), locating north of the boreal forest.

Climate: typically cold and wet. In comparison with boreal forest climate, it is less cold in winter, and less hot in summer, but the summers are shorter. Precipitation 200mm to 600mm, >evaporation, so tundra landscape is alive with ponds and streams.

Soil: Forming slowly because of the cold. Decomposition rate is also low. Annual freezing and thawing (融化 ) in the surface soil.

Solifluction (泥流 ): slowly moves soils down slopes. Netlike or polygonal pattern. (Fig. 2.35)

Biology: Perennial herbaceous plants dominate, esp. gr

asses, sedges (莎草 ), mosses and lichens. There are also woody species, such as dwarf

willows, birches. Animals, large mammals: caribou, reindeer, m

usk ox, bear, wolf. Small mammals, arctic foxes, weasels, lemmings (旅鼠 ), ground squirrels, bird (resident and migratory), diverse insects.

Human influences: ever been less influenced area in the world. However, it has also pesticides, radionuclides, etc. deposition.

Example: radioactive cesium-137 deposition from the Chernobyl power more than 2000km away.

Has been the focus of intense oil exploitation and extraction.

10. Mountains (Fig.2.36)

Geography: Forming during geological processes, such as volcanism,and movements of the earth’s crust. These processes are not even on the earth, so forming a variety of ranges and mountains. Ranges go from north to south, or from east to west, or other orientation.

Climate: Generally, temperatures becomes lower from low elevation to high elevation, and becomes wetter (Fig.2.38). Other situation, there is less precipitation at the higher elevations of polar mountains and on some tropical mountains. In other tropical regions, precipitation increases up to some middle elevation and then decreases higher up the mountain. Compared to temperate mountains, tropical mountains show a much greater daily temperature range.

Different slopes of the mountain sometime present very different precipitation (Fig补充）

Soil: generally thin, vulnerable to erosion. From lower to higher elevation, % of organic matter increases, decomposition rate decreases, soil types change similarly with that from lower latitude to higher latitude.

Biology: Vegetation changes from lower altitude to higher one similarly with that it changes from lower latitude to higher latitude.

For example, Tropical rain forest –evergreen broad-leaved forest – deciduous broad-leaved forest – coniferous forest – tundra.

Same vegetations have also similar community prognomy and structure.

But species composition is very different between high mountains and their surround regions.

Mountains are isolated from their surround areas like islands in the ocean.