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Most of the classified biomes are i
Most of the classified biomes are identified by the dominant plants found in their communities. For example, grasslands are dominated by a variety of annual and perennial species of grass, while deserts are occupied by plant species that require very little water for survival or by plants that have specific adaptations to conserve or acquire water.
The diversity of animal life and subdominant plant forms characteristic of each biome is generally controlled by abiotic environmental conditions and the productivity of the dominant vegetation. In general, species diversity becomes higher with increases in net primary productivity, moisture availability, and temperature.
Adaptation and niche specialization are nicely demonstrated in the biome concept. Organisms that fill similar niches in geographically separated but similar ecosystems usually are different species that have undergone similar adaptation independently, in response to similar environmental pressures. The vegetation of California, Chile, South Africa, South Australia, Southern Italy and Greece display similar morphological and physiological characteristics because of convergent evolution. In these areas, the vegetation consists of drought-resistant, hard-leaved, low growing woody shrubs and trees like eucalyptus, olive, juniper, and mimosa.
Arctic and Alpine Tundra
Tundra means marshy plain. The geographical distribution of the tundra biome is largely poleward of 60° North latitude. The tundra biome is characterized by an absence of trees, the presence of dwarf plants, and a ground surface that is wet, spongy, and hummocky. Soils of this biome are usually permanently frozen (permafrost) starting at a depth of a few centimeters to meter or more. The permafrost line is a physical barrier to plant root growth.
Within this biome, temperature, precipitation, and evaporation all tend to be at a minimum. Most tundra locations, have summer months with an average temperature below 10° Celsius. Precipitation in the wettest month is normally no higher that 25 millimeters. However, despite the low levels of precipitation the ground surface of the tundra biome is often waterlogged because of low rates of evapotranspiration.
The species diversity of tundra vegetation is relatively small. Plant communities are usually composed of a few species of dwarf shrubs, a few grass species, sedges, and mosses. Perhaps the most characteristic arctic tundra plants are lichens like Reindeer Moss (Cladonia spp.). The principal herbivores in this biome include caribou, musk ox, arctic hare, voles, and lemmings. Most of the bird species of the tundra have the ability to migrate and live in warmer locations during the cold winter months. The herbivore species support a small number of carnivore species like the arctic fox, snow owl, polar bear, and wolves. Reptiles and amphibians are few or completely absent because of the extremely cold temperatures.
Alpine tundra is quite similar to some arctic tundra but differs in the absence of permafrost and in the presence of better drainage.
Boreal Coniferous Forest
This moist-cool, transcontinental coniferous forest, or taiga lies largely between the 45th and 57th North latitudes. The climate of this biome is cool to cold with more precipitation than the tundra, occurring mainly in the summer because of mid-latitude cyclones. The predominant vegetation of boreal biome are needle-leaf evergreen variety tree species. Some common species include: White Spruce (Picea glauca) and Balsam Fir (Abies balsamea) east of the Rockies; Red Pine (Pinus resinosa), White Pine (Pinus strobus), and Hemlock (Tsuga canadensis) in the Great Lakes Region. In British Columbia, dominant boreal trees include: Black Spruce (Picea mariana), White Spruce (Picea glauca), Lodgepole Pine (Pinus contorta), Ponderosa Pine (Pinus pondersoa), Douglas Fir (Pseudotsuga menziesii), and Alpine Fir (Abies lasiocarpa). The understory is relatively limited as a result of the low light penetration even during the spring and fall months. Understory plants in the deciduous biome take advantage of the leafless condition of trees during these seasons concentrating there growth during this time period. Common understory species include orchids, shrubs like rose, blueberry, and cranberry (Figure 9k-2).
Figure 9k-2: The understory of boreal forest habitats is usually poorly developed.
Mammals common to the boreal forest include moose, bear, deer, wolverine, marten, lynx, wolf, snowshoe hare, vole, chipmunks, shrews, and bats (Figure 9k-3). Reptiles are rare, once again, because of cold temperatures .
Figure 9k-3: Bears are common in the boreal forest ecosystem. (Source: Wikipedia).
Boreal forest soils are characterized by a deep litter layer and slow decomposition. Soils of this biome are also acidic and mineral deficient because of the large movement of water vertically though the profile and subsequent leaching.
Temperate Deciduous Forest
As its name indicates, this biome is characterized by a moderate climate and deciduous trees. It once occupied much of the eastern half of the United States, central Europe, Korea, and China. This biome has been very extensively affected by human activity, and much of it has been converted into agricultural fields or urban developments. Dominant plants include trees like Maple (Acer spp.), Beech (Fagus spp.), Oak (Quercus spp.), Hickory (Carya spp.), Basswood (Tilia spp.), Cottonwood (Populus spp.), Elm (Ulmus spp.), and Willow (Salix spp.). The understory of shrubs and herbs in a mature deciduous forest is typically well developed and richly diversified. Many different types of herbivores and carnivores, and some reptiles and amphibians exist here.
Brown forest soils characterize temperate deciduous forest ecosystems. The surface litter layer in these soils is thin due to rapid decomposition.
Grassland
In central North America are the grasslands, the tall grass prairie toward the east and the short grass prairie westward. In Europe and Asia some grasslands are called Steppes. In South America, grasslands are known as Pampas. Prior to modern man, the tall grass prairie was dominated by species of Bluestem (Andropogon spp.) (Figure 9k-4). This particular species dominated much of the tall grass prairie forming dense covers 1.5 to 2.0 meters tall. In the western end of the prairie, where precipitation is less, Buffalo Grass (Buchloe dactyloides) and other grasses only a few inches above the soil surface are common in this habitat. Flowering herbs, including many kinds of composites and legumes, are common but much less important than grass species. Trees are limited to low lying areas and the narrow zone immediately adjacent to streams.
Figure 9k-4: Natural grassland ecosystems are dominated by various species of grass. (Source: NASA - Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC) Net Primary Productivity (NPP) Database).
Figure 9k-5: Much of the prairies is now cultivated to grow crops like canola.
In the tall grass prairie organic rich and black chernozemic soils are common. Chernozems are among the richest in nutrients and consequently the most fertile in the world. In drier parts of prairies, soils can be influenced by salinization. As a result of their fertility, most grassland ecosystems have been modified by humans to grow grain and other dryland crops (Figure 9k-5).
Grassland mammals are dominated by smaller burrowing herbivores (prairie dogs, jack rabbits, ground squirrels, and gophers) and larger running herbivores such as bison, pronghorn antelope, and elk. Carnivores include badger, coyote, ferret, wolf, and cougar. The population size of many of these species has been drastically reduced because of habitat destruction (Figure 9k-5). Some of these species are on the edge of extinction.
Desert
In its most typical form, the desert consists of shrub covered land where the plants are spatially quite dispersed. In general, the major desert biomes of the Earth are geographically found at between 25 to 40° North and South latitude, in the interiors of continents. Climatically, deserts are influenced by descending air currents which limit the formation of precipitation. Many desert areas have less than 250 millimeters of precipitation annually. Dominant plants include drought resistant shrubs like the Creosote Bush (Larrea divaricata) and Sagebrush (Artemisia tridentata), water storing succulents like cactus (Figure 9k-6), and many species are short lived annuals that complete their life cycles during infrequent and short rainy periods. Desert habitats can be devoid of vegetation if precipitation is in very short supply (Figure 9k-7).
Figure 9k-6: Cactus are a common type of drought resistant plant found in deserts.
Figure 9k-7: Desert habitat devoid of vegetation. (Source: Wikipedia).
Most desert mammals tend to be nocturnal to avoid the high temperatures. Desert habitats have a rich lizard and snake fauna because high temperatures promote the success of cold blooded life forms (Figure 9k-8).
Figure 9k-8: Lizards are quite common in desert habitats. (Source: Wikipedia).
Because productivity is low, the litter layer is comparably limited and organic content of surface soil layers is very low. Also, evaporation tends to concentrate salts at the soil surface.
Chaparral
Chaparral has a very specific spatial distribution. It is found in a narrow zone between 32 and 40° latitude North and South on the west coasts of the continents. This area has a dry climate because of the dominance of the subtropical high pressure zone during the fall, summer, and spring months. Precipitation falls mainly in the winter months because of the seasonal movement of the polar front and its associated mid-latitude cyclone storms. Annual averages range from about 300 to 750 millimeters and most of this rain falls in a period between 2 to 4 months long. As a resul
The diversity of animal life and subdominant plant forms characteristic of each biome is generally controlled by abiotic environmental conditions and the productivity of the dominant vegetation. In general, species diversity becomes higher with increases in net primary productivity, moisture availability, and temperature.
Adaptation and niche specialization are nicely demonstrated in the biome concept. Organisms that fill similar niches in geographically separated but similar ecosystems usually are different species that have undergone similar adaptation independently, in response to similar environmental pressures. The vegetation of California, Chile, South Africa, South Australia, Southern Italy and Greece display similar morphological and physiological characteristics because of convergent evolution. In these areas, the vegetation consists of drought-resistant, hard-leaved, low growing woody shrubs and trees like eucalyptus, olive, juniper, and mimosa.
Arctic and Alpine Tundra
Tundra means marshy plain. The geographical distribution of the tundra biome is largely poleward of 60° North latitude. The tundra biome is characterized by an absence of trees, the presence of dwarf plants, and a ground surface that is wet, spongy, and hummocky. Soils of this biome are usually permanently frozen (permafrost) starting at a depth of a few centimeters to meter or more. The permafrost line is a physical barrier to plant root growth.
Within this biome, temperature, precipitation, and evaporation all tend to be at a minimum. Most tundra locations, have summer months with an average temperature below 10° Celsius. Precipitation in the wettest month is normally no higher that 25 millimeters. However, despite the low levels of precipitation the ground surface of the tundra biome is often waterlogged because of low rates of evapotranspiration.
The species diversity of tundra vegetation is relatively small. Plant communities are usually composed of a few species of dwarf shrubs, a few grass species, sedges, and mosses. Perhaps the most characteristic arctic tundra plants are lichens like Reindeer Moss (Cladonia spp.). The principal herbivores in this biome include caribou, musk ox, arctic hare, voles, and lemmings. Most of the bird species of the tundra have the ability to migrate and live in warmer locations during the cold winter months. The herbivore species support a small number of carnivore species like the arctic fox, snow owl, polar bear, and wolves. Reptiles and amphibians are few or completely absent because of the extremely cold temperatures.
Alpine tundra is quite similar to some arctic tundra but differs in the absence of permafrost and in the presence of better drainage.
Boreal Coniferous Forest
This moist-cool, transcontinental coniferous forest, or taiga lies largely between the 45th and 57th North latitudes. The climate of this biome is cool to cold with more precipitation than the tundra, occurring mainly in the summer because of mid-latitude cyclones. The predominant vegetation of boreal biome are needle-leaf evergreen variety tree species. Some common species include: White Spruce (Picea glauca) and Balsam Fir (Abies balsamea) east of the Rockies; Red Pine (Pinus resinosa), White Pine (Pinus strobus), and Hemlock (Tsuga canadensis) in the Great Lakes Region. In British Columbia, dominant boreal trees include: Black Spruce (Picea mariana), White Spruce (Picea glauca), Lodgepole Pine (Pinus contorta), Ponderosa Pine (Pinus pondersoa), Douglas Fir (Pseudotsuga menziesii), and Alpine Fir (Abies lasiocarpa). The understory is relatively limited as a result of the low light penetration even during the spring and fall months. Understory plants in the deciduous biome take advantage of the leafless condition of trees during these seasons concentrating there growth during this time period. Common understory species include orchids, shrubs like rose, blueberry, and cranberry (Figure 9k-2).
Figure 9k-2: The understory of boreal forest habitats is usually poorly developed.
Mammals common to the boreal forest include moose, bear, deer, wolverine, marten, lynx, wolf, snowshoe hare, vole, chipmunks, shrews, and bats (Figure 9k-3). Reptiles are rare, once again, because of cold temperatures .
Figure 9k-3: Bears are common in the boreal forest ecosystem. (Source: Wikipedia).
Boreal forest soils are characterized by a deep litter layer and slow decomposition. Soils of this biome are also acidic and mineral deficient because of the large movement of water vertically though the profile and subsequent leaching.
Temperate Deciduous Forest
As its name indicates, this biome is characterized by a moderate climate and deciduous trees. It once occupied much of the eastern half of the United States, central Europe, Korea, and China. This biome has been very extensively affected by human activity, and much of it has been converted into agricultural fields or urban developments. Dominant plants include trees like Maple (Acer spp.), Beech (Fagus spp.), Oak (Quercus spp.), Hickory (Carya spp.), Basswood (Tilia spp.), Cottonwood (Populus spp.), Elm (Ulmus spp.), and Willow (Salix spp.). The understory of shrubs and herbs in a mature deciduous forest is typically well developed and richly diversified. Many different types of herbivores and carnivores, and some reptiles and amphibians exist here.
Brown forest soils characterize temperate deciduous forest ecosystems. The surface litter layer in these soils is thin due to rapid decomposition.
Grassland
In central North America are the grasslands, the tall grass prairie toward the east and the short grass prairie westward. In Europe and Asia some grasslands are called Steppes. In South America, grasslands are known as Pampas. Prior to modern man, the tall grass prairie was dominated by species of Bluestem (Andropogon spp.) (Figure 9k-4). This particular species dominated much of the tall grass prairie forming dense covers 1.5 to 2.0 meters tall. In the western end of the prairie, where precipitation is less, Buffalo Grass (Buchloe dactyloides) and other grasses only a few inches above the soil surface are common in this habitat. Flowering herbs, including many kinds of composites and legumes, are common but much less important than grass species. Trees are limited to low lying areas and the narrow zone immediately adjacent to streams.
Figure 9k-4: Natural grassland ecosystems are dominated by various species of grass. (Source: NASA - Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC) Net Primary Productivity (NPP) Database).
Figure 9k-5: Much of the prairies is now cultivated to grow crops like canola.
In the tall grass prairie organic rich and black chernozemic soils are common. Chernozems are among the richest in nutrients and consequently the most fertile in the world. In drier parts of prairies, soils can be influenced by salinization. As a result of their fertility, most grassland ecosystems have been modified by humans to grow grain and other dryland crops (Figure 9k-5).
Grassland mammals are dominated by smaller burrowing herbivores (prairie dogs, jack rabbits, ground squirrels, and gophers) and larger running herbivores such as bison, pronghorn antelope, and elk. Carnivores include badger, coyote, ferret, wolf, and cougar. The population size of many of these species has been drastically reduced because of habitat destruction (Figure 9k-5). Some of these species are on the edge of extinction.
Desert
In its most typical form, the desert consists of shrub covered land where the plants are spatially quite dispersed. In general, the major desert biomes of the Earth are geographically found at between 25 to 40° North and South latitude, in the interiors of continents. Climatically, deserts are influenced by descending air currents which limit the formation of precipitation. Many desert areas have less than 250 millimeters of precipitation annually. Dominant plants include drought resistant shrubs like the Creosote Bush (Larrea divaricata) and Sagebrush (Artemisia tridentata), water storing succulents like cactus (Figure 9k-6), and many species are short lived annuals that complete their life cycles during infrequent and short rainy periods. Desert habitats can be devoid of vegetation if precipitation is in very short supply (Figure 9k-7).
Figure 9k-6: Cactus are a common type of drought resistant plant found in deserts.
Figure 9k-7: Desert habitat devoid of vegetation. (Source: Wikipedia).
Most desert mammals tend to be nocturnal to avoid the high temperatures. Desert habitats have a rich lizard and snake fauna because high temperatures promote the success of cold blooded life forms (Figure 9k-8).
Figure 9k-8: Lizards are quite common in desert habitats. (Source: Wikipedia).
Because productivity is low, the litter layer is comparably limited and organic content of surface soil layers is very low. Also, evaporation tends to concentrate salts at the soil surface.
Chaparral
Chaparral has a very specific spatial distribution. It is found in a narrow zone between 32 and 40° latitude North and South on the west coasts of the continents. This area has a dry climate because of the dominance of the subtropical high pressure zone during the fall, summer, and spring months. Precipitation falls mainly in the winter months because of the seasonal movement of the polar front and its associated mid-latitude cyclone storms. Annual averages range from about 300 to 750 millimeters and most of this rain falls in a period between 2 to 4 months long. As a resul
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Hầu hết các biomes phân loại được xác định bởi các nhà máy chiếm ưu thế trong cộng đồng của họ. Ví dụ, đồng cỏ bị áp đảo bởi một loạt các hàng năm và lâu năm loài cỏ, trong khi sa mạc được chiếm bởi loài thực vật đòi hỏi rất ít nước cho sự sống còn hoặc bởi các nhà máy có các thích nghi cụ thể để tiết kiệm hoặc có được nước.Sự đa dạng của cuộc sống động vật và thực vật subdominant hình thức đặc trưng của mỗi quần xã sinh vật thường được điều khiển bởi abiotic điều kiện môi trường và năng suất của các thảm thực vật thống trị. Nói chung, tính đa dạng loài trở nên cao hơn với tăng năng suất chính net, sẵn có độ ẩm và nhiệt độ.Thích ứng và thích hợp chuyên môn độc đáo đã chứng minh trong các khái niệm quần xã sinh vật. Các sinh vật điền vào hốc tương tự như trong hệ sinh thái về mặt địa lý tách biệt nhau nhưng tương tự như thường là loài khác nhau đã trải qua tương tự như phiên bản một cách độc lập, để đáp ứng với áp lực môi trường tương tự. Các thảm thực vật California, Chile, Nam Phi, Nam Úc, Nam Italy và Hy Lạp Hiển thị tương tự như các đặc điểm hình thái học và sinh lý do tiến hóa hội tụ. Tại các khu vực, thảm thực vật bao gồm khả năng chịu hạn hán, lá cứng, thấp phát triển cây bụi thân gỗ và cây như bạch đàn, ô liu, juniper và mimosa. Đài nguyên Bắc cực và AlpineĐài nguyên có nghĩa là đồng bằng đầm lầy. Sự phân bố địa lý của quần xã sinh vật đài nguyên là chủ yếu này của 60° vĩ bắc. Quần xã sinh vật đài nguyên được đặc trưng bởi một sự vắng mặt của cây, sự hiện diện của nhà máy lùn, và nền đất ẩm ướt, xốp và hummocky. Đất của quần xã sinh vật này thường là vĩnh viễn đông lạnh (băng giá vĩnh cửu) bắt đầu từ một chiều sâu của một vài cm đến mét hoặc hơn. Đường băng giá vĩnh cửu là một rào cản vật lý để trồng tăng trưởng gốc.Trong này quần xã sinh vật, nhiệt độ, mưa, và bay hơi tất cả có xu hướng ở mức tối thiểu. Hầu hết lãnh nguyên vị trí, có mùa hè với nhiệt độ trung bình dưới 10° c. Mưa trong tháng ẩm nhất thường là không cao hơn rằng 25 mm. Tuy nhiên, mặc dù mức độ thấp của mưa mặt đất của đài nguyên quần xã sinh vật thường waterlogged vì các mức giá thấp của evapotranspiration.Sự đa dạng loài của thảm thực vật đài nguyên là tương đối nhỏ. Cộng đồng thực vật thường bao gồm một vài loài cây bụi lùn, một vài cỏ loài, sedges và rêu. Có lẽ các nhà máy đài nguyên Bắc cực đặc trưng nhất là loài địa y như tuần lộc Moss (Cladonia spp.). Các động vật ăn cỏ chính trong quần xã sinh vật này bao gồm tuần lộc, bò xạ, thỏ, voles, và lemmings. Phần lớn các loài chim của đài nguyên có khả năng để di chuyển và sống trong vị trí ấm hơn trong những tháng mùa đông lạnh. Các loài động vật ăn cỏ hỗ trợ một số ít loài động vật ăn thịt như cáo Bắc cực, cú tuyết, gấu Bắc cực và chó sói. Loài bò sát và lưỡng cư rất ít hoặc hoàn toàn vắng mặt vì nhiệt độ rất lạnh.Đài nguyên núi cao là khá giống với một số đài nguyên Bắc cực nhưng khác trong sự vắng mặt của băng giá vĩnh cửu và sự hiện diện của hệ thống thoát nước tốt hơn. Rừng tùng bách phương BắcRừng tùng bách ẩm mát mẻ, xuyên lục địa này, hay rừng taiga nằm chủ yếu giữa vĩ độ Bắc 45 và 57. Khí hậu của quần xã sinh vật này là mát mẻ để lạnh với nhiều mưa hơn các lãnh nguyên, xảy ra chủ yếu là vào mùa hè bởi vì giữa vĩ độ xoáy. Các thảm thực vật chủ yếu của quần xã sinh vật taiga là loài cây lá kim thường xanh nhiều. Một số loài phổ biến bao gồm: Vân sam trắng (Picea glauca) và Balsam Fir (Abies balsamea) về phía đông của Rockies; Thông đỏ (Pinus resinosa), trắng (Pinus strobus), và các cây độc cần (Tsuga canadensis) trong vùng ngũ đại hồ. Ở British Columbia, thống trị phương Bắc cây bao gồm: Vân sam đen (Picea mariana), vân sam trắng (Picea glauca), Lodgepole Pine (Pinus contorta), Ponderosa Pine (Pinus pondersoa), linh sam Douglas (linh sam Douglas), và Alpine Fir (Abies lasiocarpa). Loài là khá hạn chế là kết quả của sự xâm nhập thấp ánh sáng ngay cả trong những tháng mùa xuân và mùa thu. Loài thực vật trong quần xã sinh vật rụng lá tận dụng lợi thế của tình trạng lá của cây trong những mùa tập trung có tốc độ tăng trưởng trong thời kỳ này. Loài loài phổ biến bao gồm Hoa Lan, cây bụi như hoa hồng, blueberry và cranberry (hình 9k-2).Con số 9k-2: loài của môi trường sống rừng phương Bắc được thường kém phát triển. Động vật có vú phổ biến đến rừng phương bắc bao gồm con nai sừng tấm, gấu, hươu, wolverine, marten, lynx, wolf, snowshoe thỏ, vole, chipmunks, Shrewsbury, và dơi (hình 9k-3). Bò sát là rất hiếm, một lần nữa, bởi vì nhiệt độ lạnh.Con số 9k-3: gấu là phổ biến trong các hệ sinh thái rừng phương Bắc. (Nguồn: Wikipedia). Rừng phương bắc đất được đặc trưng bởi một lớp sâu rụng và phân hủy chậm. Đất của quần xã sinh vật này đều thiếu có tính axit và khoáng sản vì sự chuyển động lớn của nước theo chiều dọc mặc dù hồ sơ và sau đó lọc quặng. Rừng lá sớm rụng ôn đớiNhư tên gọi của nó ngụ ý, quần xã sinh vật này được đặc trưng bởi một khí hậu ôn hoà và deciduous trees. Nó từng chiếm phần lớn đông một nửa của các Hoa Kỳ, Trung ương châu Âu, Triều tiên và Trung Quốc. Quần xã sinh vật này đã bị ảnh hưởng rất rộng rãi bởi các hoạt động của con người, và nhiều của nó đã được chuyển đổi vào lĩnh vực nông nghiệp hoặc phát triển đô thị. Thống trị thực vật bao gồm cây như phong (Acer spp.), sồi (Fagus spp.), sồi (Quercus spp.), Hickory (Carya spp.), Basswood (Tilia spp.), Cottonwood (Populus spp.), Elm (Ulmus spp.) và liễu (Salix spp.). Loài cây bụi và các loại thảo mộc ở một khu rừng rụng lá trưởng thành thông thường cũng phát triển và đa dạng đa dạng. Nhiều loại khác nhau của động vật ăn cỏ và ăn thịt, và một số loài bò sát và lưỡng cư tồn tại ở đây.Rừng nâu đất đặc trưng hệ sinh thái rừng lá sớm rụng ôn đới. Lớp bề mặt rụng trong các loại đất là mỏng do nhanh chóng phân hủy. Đồng cỏỞ miền trung Bắc Mỹ là các đồng cỏ, đồng cỏ cỏ cao về phía đông và đồng cỏ cỏ ngắn về phía tây. Ở châu Âu và á đồng cỏ một số được gọi là các thảo nguyên. Ở Nam Mỹ, đồng cỏ được gọi là Pampas. Trước khi con người hiện đại, đồng cỏ cỏ cao chủ yếu là loài Bluestem (Andropogon spp.) (Hình 9k-4). Loài này cụ thể chi phối hầu hết đồng cỏ cỏ cao hình thành vỏ dày đặc cao 1,5 đến 2,0 m. Ở cuối phía tây của đồng cỏ, nơi mưa là ít hơn, Buffalo cỏ (Buchloe dactyloides) và khác cỏ chỉ một vài inch ở trên mặt đất là phổ biến trong môi trường sống này. Thảo dược thực vật có hoa, bao gồm nhiều loại vật liệu tổng hợp và đậu, được phổ biến nhưng nhiều ít quan trọng hơn loài cỏ. Cây được giới hạn thấp nằm khu vực và vùng hẹp ngay lập tức tiếp giáp với dòng.Con số 9k-4: hệ sinh thái đồng cỏ tự nhiên chủ yếu là các loài cỏ. (Nguồn: NASA - Oak Ridge quốc gia phòng thí nghiệm (ORNL) phân phối hoạt động Trung tâm lưu trữ (DAAC) sản xuất chính Net (NPP) cơ sở dữ liệu). Con số 9k-5: hầu hết các đồng cỏ bây giờ được trồng để phát triển cây trồng như dầu canola. Trong cỏ cao prairie hữu cơ phong phú và đen chernozemic đất là phổ biến. Chernozems là một trong giàu chất dinh dưỡng và kết quả là màu mỡ nhất trên thế giới. Trong phần khô của đồng cỏ, đất có thể bị ảnh hưởng bởi salinization. Là kết quả của khả năng sinh sản của họ, hầu hết các hệ sinh thái đồng cỏ đã được sửa đổi bởi con người phát triển ngũ cốc và các loại cây trồng khô (hình 9 k-5).Đồng cỏ động vật có vú bị áp đảo bởi nhỏ hơn rắn cỏ (prairie chó, jack thỏ, đất sóc và chuột túi má) và động vật ăn cỏ lớn hơn chạy như bò rừng bizon, linh dương pronghorn và Nai sừng tấm. Động vật ăn thịt bao gồm badger, coyote, ferret, chó sói, và cougar. Kích thước dân của nhiều người trong số các loài đã được giảm đáng kể vì phá hủy môi trường sống (hình 9 k-5). Một số những loài đang trên bờ tuyệt chủng. Sa mạcỞ dạng tiêu biểu nhất của nó, sa mạc bao gồm cây bụi phủ đất nơi mà các nhà máy trong không gian khá được phân tán. Nói chung, sa mạc biomes lớn của trái đất về mặt địa lý nằm tại khoảng 25-40° Bắc và Nam vĩ độ, trong nội thất của lục địa. Climatically, sa mạc chịu ảnh hưởng của dòng không khí mà hạn chế sự hình thành của mưa giảm dần. Nhiều khu vực sa mạc có ít hơn 250 mm mưa hàng năm. Thống trị thực vật bao gồm khả năng chịu hạn hán cây bụi như Creosote Bush (Larrea divaricata) và Sagebrush (Artemisia tridentata), nước lưu trữ succulents như cây xương rồng (hình 9k-6), và nhiều loài là cây một năm ngắn mà hoàn thành của chu kỳ cuộc sống trong thời kỳ mưa không thường xuyên và ngắn. Môi trường sống sa mạc có thể không có những thảm thực vật nếu mưa là rất ngắn cung cấp (hình 9 k-7).Con số 9k-6: cây xương rồng là một loại phổ biến của khả năng chịu hạn hán thực vật được tìm thấy trong sa mạc. Con số 9k-7: môi trường sống sa mạc devoid của thảm thực vật. (Nguồn: Wikipedia). Hầu hết các động vật có vú sa mạc có xu hướng ăn đêm để tránh các nhiệt độ cao. Môi trường sống sa mạc có một động vật phong phú thằn lằn và con rắn vì nhiệt độ cao thúc đẩy sự thành công của hình thức cuộc sống lạnh máu (hình 9k-8).Con số 9k-8: thằn lằn là khá phổ biến trong môi trường sống sa mạc. (Nguồn: Wikipedia). Bởi vì năng suất thấp, lớp rụng là comparably hạn chế và các nội dung hữu cơ của lớp bề mặt đất là rất thấp. Ngoài ra, bay hơi có xu hướng tập trung muối ở bề mặt đất. ChaparralChaparral đã phân phối không gian rất cụ thể. Nó nằm trong một khu vực hẹp giữa 32 và 40 ° vĩ Bắc và Nam trên bờ biển Tây của các lục địa. Khu vực này có khí hậu khô vì sự thống trị của vùng nhiệt đới áp lực cao trong mùa thu, mùa hè và mùa xuân vài tháng. Mưa rơi chủ yếu là trong những tháng mùa đông vì sự chuyển động theo mùa của frông và của nó kết hợp giữa vĩ độ cơn bão. Hàng năm trung bình khoảng từ khoảng 300 đến 750 mm và hầu hết trong số này mưa rơi vào một giai đoạn từ 2 đến 4 tháng dài. Như là một resul
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Most of the classified biomes are identified by the dominant plants found in their communities. For example, grasslands are dominated by a variety of annual and perennial species of grass, while deserts are occupied by plant species that require very little water for survival or by plants that have specific adaptations to conserve or acquire water.
The diversity of animal life and subdominant plant forms characteristic of each biome is generally controlled by abiotic environmental conditions and the productivity of the dominant vegetation. In general, species diversity becomes higher with increases in net primary productivity, moisture availability, and temperature.
Adaptation and niche specialization are nicely demonstrated in the biome concept. Organisms that fill similar niches in geographically separated but similar ecosystems usually are different species that have undergone similar adaptation independently, in response to similar environmental pressures. The vegetation of California, Chile, South Africa, South Australia, Southern Italy and Greece display similar morphological and physiological characteristics because of convergent evolution. In these areas, the vegetation consists of drought-resistant, hard-leaved, low growing woody shrubs and trees like eucalyptus, olive, juniper, and mimosa.
Arctic and Alpine Tundra
Tundra means marshy plain. The geographical distribution of the tundra biome is largely poleward of 60° North latitude. The tundra biome is characterized by an absence of trees, the presence of dwarf plants, and a ground surface that is wet, spongy, and hummocky. Soils of this biome are usually permanently frozen (permafrost) starting at a depth of a few centimeters to meter or more. The permafrost line is a physical barrier to plant root growth.
Within this biome, temperature, precipitation, and evaporation all tend to be at a minimum. Most tundra locations, have summer months with an average temperature below 10° Celsius. Precipitation in the wettest month is normally no higher that 25 millimeters. However, despite the low levels of precipitation the ground surface of the tundra biome is often waterlogged because of low rates of evapotranspiration.
The species diversity of tundra vegetation is relatively small. Plant communities are usually composed of a few species of dwarf shrubs, a few grass species, sedges, and mosses. Perhaps the most characteristic arctic tundra plants are lichens like Reindeer Moss (Cladonia spp.). The principal herbivores in this biome include caribou, musk ox, arctic hare, voles, and lemmings. Most of the bird species of the tundra have the ability to migrate and live in warmer locations during the cold winter months. The herbivore species support a small number of carnivore species like the arctic fox, snow owl, polar bear, and wolves. Reptiles and amphibians are few or completely absent because of the extremely cold temperatures.
Alpine tundra is quite similar to some arctic tundra but differs in the absence of permafrost and in the presence of better drainage.
Boreal Coniferous Forest
This moist-cool, transcontinental coniferous forest, or taiga lies largely between the 45th and 57th North latitudes. The climate of this biome is cool to cold with more precipitation than the tundra, occurring mainly in the summer because of mid-latitude cyclones. The predominant vegetation of boreal biome are needle-leaf evergreen variety tree species. Some common species include: White Spruce (Picea glauca) and Balsam Fir (Abies balsamea) east of the Rockies; Red Pine (Pinus resinosa), White Pine (Pinus strobus), and Hemlock (Tsuga canadensis) in the Great Lakes Region. In British Columbia, dominant boreal trees include: Black Spruce (Picea mariana), White Spruce (Picea glauca), Lodgepole Pine (Pinus contorta), Ponderosa Pine (Pinus pondersoa), Douglas Fir (Pseudotsuga menziesii), and Alpine Fir (Abies lasiocarpa). The understory is relatively limited as a result of the low light penetration even during the spring and fall months. Understory plants in the deciduous biome take advantage of the leafless condition of trees during these seasons concentrating there growth during this time period. Common understory species include orchids, shrubs like rose, blueberry, and cranberry (Figure 9k-2).
Figure 9k-2: The understory of boreal forest habitats is usually poorly developed.
Mammals common to the boreal forest include moose, bear, deer, wolverine, marten, lynx, wolf, snowshoe hare, vole, chipmunks, shrews, and bats (Figure 9k-3). Reptiles are rare, once again, because of cold temperatures .
Figure 9k-3: Bears are common in the boreal forest ecosystem. (Source: Wikipedia).
Boreal forest soils are characterized by a deep litter layer and slow decomposition. Soils of this biome are also acidic and mineral deficient because of the large movement of water vertically though the profile and subsequent leaching.
Temperate Deciduous Forest
As its name indicates, this biome is characterized by a moderate climate and deciduous trees. It once occupied much of the eastern half of the United States, central Europe, Korea, and China. This biome has been very extensively affected by human activity, and much of it has been converted into agricultural fields or urban developments. Dominant plants include trees like Maple (Acer spp.), Beech (Fagus spp.), Oak (Quercus spp.), Hickory (Carya spp.), Basswood (Tilia spp.), Cottonwood (Populus spp.), Elm (Ulmus spp.), and Willow (Salix spp.). The understory of shrubs and herbs in a mature deciduous forest is typically well developed and richly diversified. Many different types of herbivores and carnivores, and some reptiles and amphibians exist here.
Brown forest soils characterize temperate deciduous forest ecosystems. The surface litter layer in these soils is thin due to rapid decomposition.
Grassland
In central North America are the grasslands, the tall grass prairie toward the east and the short grass prairie westward. In Europe and Asia some grasslands are called Steppes. In South America, grasslands are known as Pampas. Prior to modern man, the tall grass prairie was dominated by species of Bluestem (Andropogon spp.) (Figure 9k-4). This particular species dominated much of the tall grass prairie forming dense covers 1.5 to 2.0 meters tall. In the western end of the prairie, where precipitation is less, Buffalo Grass (Buchloe dactyloides) and other grasses only a few inches above the soil surface are common in this habitat. Flowering herbs, including many kinds of composites and legumes, are common but much less important than grass species. Trees are limited to low lying areas and the narrow zone immediately adjacent to streams.
Figure 9k-4: Natural grassland ecosystems are dominated by various species of grass. (Source: NASA - Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC) Net Primary Productivity (NPP) Database).
Figure 9k-5: Much of the prairies is now cultivated to grow crops like canola.
In the tall grass prairie organic rich and black chernozemic soils are common. Chernozems are among the richest in nutrients and consequently the most fertile in the world. In drier parts of prairies, soils can be influenced by salinization. As a result of their fertility, most grassland ecosystems have been modified by humans to grow grain and other dryland crops (Figure 9k-5).
Grassland mammals are dominated by smaller burrowing herbivores (prairie dogs, jack rabbits, ground squirrels, and gophers) and larger running herbivores such as bison, pronghorn antelope, and elk. Carnivores include badger, coyote, ferret, wolf, and cougar. The population size of many of these species has been drastically reduced because of habitat destruction (Figure 9k-5). Some of these species are on the edge of extinction.
Desert
In its most typical form, the desert consists of shrub covered land where the plants are spatially quite dispersed. In general, the major desert biomes of the Earth are geographically found at between 25 to 40° North and South latitude, in the interiors of continents. Climatically, deserts are influenced by descending air currents which limit the formation of precipitation. Many desert areas have less than 250 millimeters of precipitation annually. Dominant plants include drought resistant shrubs like the Creosote Bush (Larrea divaricata) and Sagebrush (Artemisia tridentata), water storing succulents like cactus (Figure 9k-6), and many species are short lived annuals that complete their life cycles during infrequent and short rainy periods. Desert habitats can be devoid of vegetation if precipitation is in very short supply (Figure 9k-7).
Figure 9k-6: Cactus are a common type of drought resistant plant found in deserts.
Figure 9k-7: Desert habitat devoid of vegetation. (Source: Wikipedia).
Most desert mammals tend to be nocturnal to avoid the high temperatures. Desert habitats have a rich lizard and snake fauna because high temperatures promote the success of cold blooded life forms (Figure 9k-8).
Figure 9k-8: Lizards are quite common in desert habitats. (Source: Wikipedia).
Because productivity is low, the litter layer is comparably limited and organic content of surface soil layers is very low. Also, evaporation tends to concentrate salts at the soil surface.
Chaparral
Chaparral has a very specific spatial distribution. It is found in a narrow zone between 32 and 40° latitude North and South on the west coasts of the continents. This area has a dry climate because of the dominance of the subtropical high pressure zone during the fall, summer, and spring months. Precipitation falls mainly in the winter months because of the seasonal movement of the polar front and its associated mid-latitude cyclone storms. Annual averages range from about 300 to 750 millimeters and most of this rain falls in a period between 2 to 4 months long. As a resul
The diversity of animal life and subdominant plant forms characteristic of each biome is generally controlled by abiotic environmental conditions and the productivity of the dominant vegetation. In general, species diversity becomes higher with increases in net primary productivity, moisture availability, and temperature.
Adaptation and niche specialization are nicely demonstrated in the biome concept. Organisms that fill similar niches in geographically separated but similar ecosystems usually are different species that have undergone similar adaptation independently, in response to similar environmental pressures. The vegetation of California, Chile, South Africa, South Australia, Southern Italy and Greece display similar morphological and physiological characteristics because of convergent evolution. In these areas, the vegetation consists of drought-resistant, hard-leaved, low growing woody shrubs and trees like eucalyptus, olive, juniper, and mimosa.
Arctic and Alpine Tundra
Tundra means marshy plain. The geographical distribution of the tundra biome is largely poleward of 60° North latitude. The tundra biome is characterized by an absence of trees, the presence of dwarf plants, and a ground surface that is wet, spongy, and hummocky. Soils of this biome are usually permanently frozen (permafrost) starting at a depth of a few centimeters to meter or more. The permafrost line is a physical barrier to plant root growth.
Within this biome, temperature, precipitation, and evaporation all tend to be at a minimum. Most tundra locations, have summer months with an average temperature below 10° Celsius. Precipitation in the wettest month is normally no higher that 25 millimeters. However, despite the low levels of precipitation the ground surface of the tundra biome is often waterlogged because of low rates of evapotranspiration.
The species diversity of tundra vegetation is relatively small. Plant communities are usually composed of a few species of dwarf shrubs, a few grass species, sedges, and mosses. Perhaps the most characteristic arctic tundra plants are lichens like Reindeer Moss (Cladonia spp.). The principal herbivores in this biome include caribou, musk ox, arctic hare, voles, and lemmings. Most of the bird species of the tundra have the ability to migrate and live in warmer locations during the cold winter months. The herbivore species support a small number of carnivore species like the arctic fox, snow owl, polar bear, and wolves. Reptiles and amphibians are few or completely absent because of the extremely cold temperatures.
Alpine tundra is quite similar to some arctic tundra but differs in the absence of permafrost and in the presence of better drainage.
Boreal Coniferous Forest
This moist-cool, transcontinental coniferous forest, or taiga lies largely between the 45th and 57th North latitudes. The climate of this biome is cool to cold with more precipitation than the tundra, occurring mainly in the summer because of mid-latitude cyclones. The predominant vegetation of boreal biome are needle-leaf evergreen variety tree species. Some common species include: White Spruce (Picea glauca) and Balsam Fir (Abies balsamea) east of the Rockies; Red Pine (Pinus resinosa), White Pine (Pinus strobus), and Hemlock (Tsuga canadensis) in the Great Lakes Region. In British Columbia, dominant boreal trees include: Black Spruce (Picea mariana), White Spruce (Picea glauca), Lodgepole Pine (Pinus contorta), Ponderosa Pine (Pinus pondersoa), Douglas Fir (Pseudotsuga menziesii), and Alpine Fir (Abies lasiocarpa). The understory is relatively limited as a result of the low light penetration even during the spring and fall months. Understory plants in the deciduous biome take advantage of the leafless condition of trees during these seasons concentrating there growth during this time period. Common understory species include orchids, shrubs like rose, blueberry, and cranberry (Figure 9k-2).
Figure 9k-2: The understory of boreal forest habitats is usually poorly developed.
Mammals common to the boreal forest include moose, bear, deer, wolverine, marten, lynx, wolf, snowshoe hare, vole, chipmunks, shrews, and bats (Figure 9k-3). Reptiles are rare, once again, because of cold temperatures .
Figure 9k-3: Bears are common in the boreal forest ecosystem. (Source: Wikipedia).
Boreal forest soils are characterized by a deep litter layer and slow decomposition. Soils of this biome are also acidic and mineral deficient because of the large movement of water vertically though the profile and subsequent leaching.
Temperate Deciduous Forest
As its name indicates, this biome is characterized by a moderate climate and deciduous trees. It once occupied much of the eastern half of the United States, central Europe, Korea, and China. This biome has been very extensively affected by human activity, and much of it has been converted into agricultural fields or urban developments. Dominant plants include trees like Maple (Acer spp.), Beech (Fagus spp.), Oak (Quercus spp.), Hickory (Carya spp.), Basswood (Tilia spp.), Cottonwood (Populus spp.), Elm (Ulmus spp.), and Willow (Salix spp.). The understory of shrubs and herbs in a mature deciduous forest is typically well developed and richly diversified. Many different types of herbivores and carnivores, and some reptiles and amphibians exist here.
Brown forest soils characterize temperate deciduous forest ecosystems. The surface litter layer in these soils is thin due to rapid decomposition.
Grassland
In central North America are the grasslands, the tall grass prairie toward the east and the short grass prairie westward. In Europe and Asia some grasslands are called Steppes. In South America, grasslands are known as Pampas. Prior to modern man, the tall grass prairie was dominated by species of Bluestem (Andropogon spp.) (Figure 9k-4). This particular species dominated much of the tall grass prairie forming dense covers 1.5 to 2.0 meters tall. In the western end of the prairie, where precipitation is less, Buffalo Grass (Buchloe dactyloides) and other grasses only a few inches above the soil surface are common in this habitat. Flowering herbs, including many kinds of composites and legumes, are common but much less important than grass species. Trees are limited to low lying areas and the narrow zone immediately adjacent to streams.
Figure 9k-4: Natural grassland ecosystems are dominated by various species of grass. (Source: NASA - Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC) Net Primary Productivity (NPP) Database).
Figure 9k-5: Much of the prairies is now cultivated to grow crops like canola.
In the tall grass prairie organic rich and black chernozemic soils are common. Chernozems are among the richest in nutrients and consequently the most fertile in the world. In drier parts of prairies, soils can be influenced by salinization. As a result of their fertility, most grassland ecosystems have been modified by humans to grow grain and other dryland crops (Figure 9k-5).
Grassland mammals are dominated by smaller burrowing herbivores (prairie dogs, jack rabbits, ground squirrels, and gophers) and larger running herbivores such as bison, pronghorn antelope, and elk. Carnivores include badger, coyote, ferret, wolf, and cougar. The population size of many of these species has been drastically reduced because of habitat destruction (Figure 9k-5). Some of these species are on the edge of extinction.
Desert
In its most typical form, the desert consists of shrub covered land where the plants are spatially quite dispersed. In general, the major desert biomes of the Earth are geographically found at between 25 to 40° North and South latitude, in the interiors of continents. Climatically, deserts are influenced by descending air currents which limit the formation of precipitation. Many desert areas have less than 250 millimeters of precipitation annually. Dominant plants include drought resistant shrubs like the Creosote Bush (Larrea divaricata) and Sagebrush (Artemisia tridentata), water storing succulents like cactus (Figure 9k-6), and many species are short lived annuals that complete their life cycles during infrequent and short rainy periods. Desert habitats can be devoid of vegetation if precipitation is in very short supply (Figure 9k-7).
Figure 9k-6: Cactus are a common type of drought resistant plant found in deserts.
Figure 9k-7: Desert habitat devoid of vegetation. (Source: Wikipedia).
Most desert mammals tend to be nocturnal to avoid the high temperatures. Desert habitats have a rich lizard and snake fauna because high temperatures promote the success of cold blooded life forms (Figure 9k-8).
Figure 9k-8: Lizards are quite common in desert habitats. (Source: Wikipedia).
Because productivity is low, the litter layer is comparably limited and organic content of surface soil layers is very low. Also, evaporation tends to concentrate salts at the soil surface.
Chaparral
Chaparral has a very specific spatial distribution. It is found in a narrow zone between 32 and 40° latitude North and South on the west coasts of the continents. This area has a dry climate because of the dominance of the subtropical high pressure zone during the fall, summer, and spring months. Precipitation falls mainly in the winter months because of the seasonal movement of the polar front and its associated mid-latitude cyclone storms. Annual averages range from about 300 to 750 millimeters and most of this rain falls in a period between 2 to 4 months long. As a resul
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- A multidisciplinary company.
- We see from (5.4) that in the general ca
- Environmental Development Corp.
- Shanda has over 600 million registered a
- Tien, I forgot to tell you the most cruc
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- trả lời câu hỏi phỏng vấn
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- On a political map, country borders are
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- It has been expanding its online section
- trả lời câu hỏi phỏng vấn
- It has been expanding its online section
- I don't know why but I don't see this
- 늘 똑같은 하늘에 늘 같은 하루 그대가 없는것말고는 달라진게 없는데 난
- nơi có truyền thống đấu tranh kiên cường
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- Tôi rất xin lỗi,
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