The Four Seasons: Change Marks the Passing of a Year

In the summer, temperatures may increase to their hottest of the year. If they spike too high, heat waves or droughts may cause trouble for people, animals, and plants. For example, in the summer of 2003, the high temperatures claimed more than 30,000 lives, according to Encyclopedia Britannica. Rainfall may increase in some areas, as well. Others may receive less water, and forest fires may become more frequent. 

In the autumn, or fall, temperatures cool again. Plants may begin to grow dormant. Animals might prepare themselves for the upcoming cold weather, storing food or traveling to warmer regions. Various cultures have celebrated bountiful harvests with annual festivals. Thanksgiving is a good example. "Thanksgiving in the United States is a historical commemoration but it has a spiritual dimension strongly associated with homecoming and giving praise for what has been bestowed upon us," Cristina De Rossi, an anthropologist at Barnet and Southgate College in London, told Live Science.  

Winter often brings a chill. Some areas may experience snow or ice, while others see only cold rain. Animals find ways to warm themselves, and may have changed their appearance to adapt. "In a similar way to the Autumnal theme, Winter festivals celebrate the return of the light during a time of deepest physical darkness," said De Rossi. The Indian festival of Diwali, for example, which takes place between October and November, celebrates the triumph of righteousness, and of light over darkness.

The four seasons vary significantly in characteristics, and can prompt changes in the world around them.

Credit: Shelli Jensen | Shutterstock

In the summer, temperatures may increase to their hottest of the year. If they spike too high, heat waves or droughts may cause trouble for people, animals, and plants. For example, in the summer of 2003, the high temperatures claimed more than 30,000 lives, according to Encyclopedia Britannica. Rainfall may increase in some areas, as well. Others may receive less water, and forest fires may become more frequent. 

In the autumn, or fall, temperatures cool again. Plants may begin to grow dormant. Animals might prepare themselves for the upcoming cold weather, storing food or traveling to warmer regions. Various cultures have celebrated bountiful harvests with annual festivals. Thanksgiving is a good example. "Thanksgiving in the United States is a historical commemoration but it has a spiritual dimension strongly associated with homecoming and giving praise for what has been bestowed upon us," Cristina De Rossi, an anthropologist at Barnet and Southgate College in London, told Live Science.  

Winter often brings a chill. Some areas may experience snow or ice, while others see only cold rain. Animals find ways to warm themselves, and may have changed their appearance to adapt. "In a similar way to the Autumnal theme, Winter festivals celebrate the return of the light during a time of deepest physical darkness," said De Rossi. The Indian festival of Diwali, for example, which takes place between October and November, celebrates the triumph of righteousness, and of light over darkness.

The timing and characteristics of the seasons depends upon the location on Earth. Regions near the equator experience fairly constant temperatures throughout the year, with balmy winters barely discernible from warm summers. This is because it gets fairly constant light from the sun, due to its position on the outer curve of the Earth, according to the Atmospheric Radiation Measurement (ARM) program.

For areas to the north and south, the seasons can change more significantly. People closer to the poles might experience icier, more frigid winters, while those closer to the equator might suffer hotter summers. Other factors can also affect the weather and temperature over the seasons; some areas experience dry summers as temperatures spike, while others might call summer their "wet season." A wet season is when the average precipitation of an area is 2.4 inches (60 millimeters) or more, according to the British Broadcasting Company (BBC). Mountainous regions might experience more snowfall than plains within the same latitude, while oceanfront property could see an increase in violent tropical storms as the weather shifts.

The time of year a region experiences a season depends on whether it is in the northern or southern hemisphere. The Southern Hemisphere experiences winter while its northern neighbors chart summer; the north sees the slow blossom of spring while the south brings in the autumn harvest. 

Earth and the sun

The cycle of seasons is caused by Earth's tilt toward the sun. The planet rotates around an (invisible) axis. At different times during the year, the northern or southern axis is closer to the sun. During these times, the hemisphere tipped toward the star experiences summer, while the hemisphere tilted away from the sun experiences winter, according to the National Oceanic and Atmospheric Administration (NOAA).

At other locations in Earth's annual journey, the axis is not tilted toward or away from the sun. During these times of the year, the hemispheres experience spring and autumn.

The astronomical definition of the seasons relates to specific points in Earth's trip around the sun. The summer and winter solstice, the longest and shortest day of the year, occur when Earth's axis is either closest or farthest from the sun. The summer solstice in the Northern Hemisphere occurs around June 21, the same day as the winter solstice in the Southern Hemisphere, according to NOAA. The south's summer solsticeoccurs around December 21, the winter solstice for the north. In both hemispheres, the summer solstice marks the first day of astronomical summer, while the winter solstice is considered the first day of astronomical winter.

Equinoxes are another significant day during Earth's journey around the Sun. On these days, the planet's axis is pointed parallel to the Sun, rather than toward or away from it. Day and night during the equinoxes are supposed to be close to equal. The spring, or vernal, equinox for the northern hemisphere takes place around March 20, the same day as the south's autumnal equinox. The vernal equinox in the southern hemisphere occurs around September 20, when people in the north celebrate the autumnal equinox. The vernal equinox marks the first day of astronomical spring for a hemisphere, while the autumnal equinox ushers in the first day of fall. [Infographic: Earth's Solstices & Equinoxes Explained]

But changes in the weather often precede these significant points. The meteorological seasons focus on these changes, fitting the seasons to the three months that best usher them in. December to February marks meteorological winter in the Northern Hemisphere and meteorological summer in the southern. March, April, and May are lauded as spring or autumn, depending on the location, while June through August are the months of summer for the north and winter for the south. September, October, and November conclude the cycle, ushering in fall in northern regions and spring in southern, according to NOAA.

The seasons can bring a wide variety to the year for those locations that experience them in full. The weather in each one may allow people to engage in activities that they cannot perform in others — skiing in the winter, swimming in the summer. Each season brings with it its own potential dangers, but also its own particular brand of beauty.

Additional reporting by Alina Bradford, Live Science Contributor.

The timing and characteristics of the seasons depends upon the location on Earth. Regions near the equator experience fairly constant temperatures throughout the year, with balmy winters barely discernible from warm summers. This is because it gets fairly constant light from the sun, due to its position on the outer curve of the Earth, according to the Atmospheric Radiation Measurement (ARM) program.

For areas to the north and south, the seasons can change more significantly. People closer to the poles might experience icier, more frigid winters, while those closer to the equator might suffer hotter summers. Other factors can also affect the weather and temperature over the seasons; some areas experience dry summers as temperatures spike, while others might call summer their "wet season." A wet season is when the average precipitation of an area is 2.4 inches (60 millimeters) or more, according to the British Broadcasting Company (BBC). Mountainous regions might experience more snowfall than plains within the same latitude, while oceanfront property could see an increase in violent tropical storms as the weather shifts.

The time of year a region experiences a season depends on whether it is in the northern or southern hemisphere. The Southern Hemisphere experiences winter while its northern neighbors chart summer; the north sees the slow blossom of spring while the south brings in the autumn harvest. 

Earth and the sun

The cycle of seasons is caused by Earth's tilt toward the sun. The planet rotates around an (invisible) axis. At different times during the year, the northern or southern axis is closer to the sun. During these times, the hemisphere tipped toward the star experiences summer, while the hemisphere tilted away from the sun experiences winter, according to the National Oceanic and Atmospheric Administration (NOAA).

At other locations in Earth's annual journey, the axis is not tilted toward or away from the sun. During these times of the year, the hemispheres experience spring and autumn.

The astronomical definition of the seasons relates to specific points in Earth's trip around the sun. The summer and winter solstice, the longest and shortest day of the year, occur when Earth's axis is either closest or farthest from the sun. The summer solstice in the Northern Hemisphere occurs around June 21, the same day as the winter solstice in the Southern Hemisphere, according to NOAA. The south's summer solsticeoccurs around December 21, the winter solstice for the north. In both hemispheres, the summer solstice marks the first day of astronomical summer, while the winter solstice is considered the first day of astronomical winter.

Equinoxes are another significant day during Earth's journey around the Sun. On these days, the planet's axis is pointed parallel to the Sun, rather than toward or away from it. Day and night during the equinoxes are supposed to be close to equal. The spring, or vernal, equinox for the northern hemisphere takes place around March 20, the same day as the south's autumnal equinox. The vernal equinox in the southern hemisphere occurs around September 20, when people in the north celebrate the autumnal equinox. The vernal equinox marks the first day of astronomical spring for a hemisphere, while the autumnal equinox ushers in the first day of fall. [Infographic: Earth's Solstices & Equinoxes Explained]

But changes in the weather often precede these significant points. The meteorological seasons focus on these changes, fitting the seasons to the three months that best usher them in. December to February marks meteorological winter in the Northern Hemisphere and meteorological summer in the southern. March, April, and May are lauded as spring or autumn, depending on the location, while June through August are the months of summer for the north and winter for the south. September, October, and November conclude the cycle, ushering in fall in northern regions and spring in southern, according to NOAA.

The seasons can bring a wide variety to the year for those locations that experience them in full. The weather in each one may allow people to engage in activities that they cannot perform in others — skiing in the winter, swimming in the summer. Each season brings with it its own potential dangers, but also its own particular brand of beauty.

Additional reporting by Alina Bradford, Live Science Contributor.

Location

The timing and characteristics of the seasons depends upon the location on Earth. Regions near the equator experience fairly constant temperatures throughout the year, with balmy winters barely discernible from warm summers. This is because it gets fairly constant light from the sun, due to its position on the outer curve of the Earth, according to the Atmospheric Radiation Measurement (ARM) program.

For areas to the north and south, the seasons can change more significantly. People closer to the poles might experience icier, more frigid winters, while those closer to the equator might suffer hotter summers. Other factors can also affect the weather and temperature over the seasons; some areas experience dry summers as temperatures spike, while others might call summer their "wet season." A wet season is when the average precipitation of an area is 2.4 inches (60 millimeters) or more, according to the British Broadcasting Company (BBC). Mountainous regions might experience more snowfall than plains within the same latitude, while oceanfront property could see an increase in violent tropical storms as the weather shifts.

The time of year a region experiences a season depends on whether it is in the northern or southern hemisphere. The Southern Hemisphere experiences winter while its northern neighbors chart summer; the north sees the slow blossom of spring while the south brings in the autumn harvest. 

Earth and the sun

The cycle of seasons is caused by Earth's tilt toward the sun. The planet rotates around an (invisible) axis. At different times during the year, the northern or southern axis is closer to the sun. During these times, the hemisphere tipped toward the star experiences summer, while the hemisphere tilted away from the sun experiences winter, according to the National Oceanic and Atmospheric Administration (NOAA).

At other locations in Earth's annual journey, the axis is not tilted toward or away from the sun. During these times of the year, the hemispheres experience spring and autumn.

The astronomical definition of the seasons relates to specific points in Earth's trip around the sun. The summer and winter solstice, the longest and shortest day of the year, occur when Earth's axis is either closest or farthest from the sun. The summer solstice in the Northern Hemisphere occurs around June 21, the same day as the winter solstice in the Southern Hemisphere, according to NOAA. The south's summer solstice occurs around December 21, the winter solstice for the north. In both hemispheres, the summer solstice marks the first day of astronomical summer, while the winter solstice is considered the first day of astronomical winter.

Equinoxes are another significant day during Earth's journey around the Sun. On these days, the planet's axis is pointed parallel to the Sun, rather than toward or away from it. Day and night during the equinoxes are supposed to be close to equal. The spring, or vernal, equinox for the northern hemisphere takes place around March 20, the same day as the south's autumnal equinox. The vernal equinox in the southern hemisphere occurs around September 20, when people in the north celebrate the autumnal equinox. The vernal equinox marks the first day of astronomical spring for a hemisphere, while the autumnal equinox ushers in the first day of fall. [Infographic: Earth's Solstices & Equinoxes Explained]

But changes in the weather often precede these significant points. The meteorological seasons focus on these changes, fitting the seasons to the three months that best usher them in. December to February marks meteorological winter in the Northern Hemisphere and meteorological summer in the southern. March, April, and May are lauded as spring or autumn, depending on the location, while June through August are the months of summer for the north and winter for the south. September, October, and November conclude the cycle, ushering in fall in northern regions and spring in southern, according to NOAA.

The seasons can bring a wide variety to the year for those locations that experience them in full. The weather in each one may allow people to engage in activities that they cannot perform in others — skiing in the winter, swimming in the summer. Each season brings with it its own potential dangers, but also its own particular brand of beauty.

Additional reporting by Alina Bradford, Live Science Contributor.

For further information log on website :
http://www.livescience.com/25202-seasons.html

Wetlands Biome

What is a Wetland?

A Wetland is described by the plant species that live in it. If an area is wet enough for long enough to support a majority of plants that are adapted to wet conditions then you have a wetland. An example might be a patch of land that is dominated by cattails. Since cattails are adapted to a life where they are partially submerged by water, then the area would be considered a wetland, even if it is dry for a part of the year. Not all wetlands are restricted to freshwater habitats either.  Many saltwater marshes thrive in the salty coastal zones.

Types of Wetlands

There are many types of wetlands. Scientists often divide them up into the following groups.

• Marshes
• Swamps
• Bogs
• Fens

Marshes are characterized by the presence of soft-stemmed vegetation adapted to saturated soils. These are typically grasses, sedges or rushes. Some common ones include prairie potholes, the expanses of the Everglades, and salt marshes.

Swamps are characterized by the domination of woody plants. There are many different kinds of swamps including the cypress swamps of Louisiana, Red Maple swamps in the Northeast and the Mangrove forests of tropical and subtropical regions.

Bogs are distinctive wetlands that are low in nutrients and often contain very acidic water and extensive peat deposits. Bogs are also one of the stages of succession as a lake fills in.

Fens are different from bogs in that they receive their water supply from either runoff or groundwater (not rainfall). This usually results in a different water chemistry. Fens have either neutral or alkaline waters and are typically not stages in lake succession.

Where are Wetlands Found?

Wetlands are found all over the world, within almost every terrestrial biome from deserts to alpine tundra. The map below shows the distribution of wetland areas in the United States. Notice the abundance of wetland areas in the Southeast, the Mississippi river system and in the northern states of Minnesota and Wisconsin.

Plants in a Wetland

Plants that are adapted to moist and humid conditions (such as those found in wetlands) are called hydrophytes. These include cattails, water lilies, bulltongue, sedges, tamarisk, and many kinds of rush.

Wetland plants are adapted to the saturated conditions that persist for a majority of the year. The different vegetation types in a wetland can be divided up into emergents, floating, and submerged plants.

An Invasive Wetland Plant: Hydrilla

For the species profile of a wetland plant we decided to pick hydrilla. It is an extremely competitive invader that we have only recently found ways to control. Of particular interest, there is a small fly larvae that eats through hydrilla. We filmed the following episode at the Army Corp of Engineer’s Lewisville, TX, research facility and at their Vicksburg, MS, research facility.

How you can help Save Wetlands

This may or may not come as a surprise, but Wetlands have been reported to be the most threatened ecosystem in the world today. People often see wetlands as wastelands and non-productive land, and these valuable regions are filled in and destroyed. This is endangering human, plant, and animal life at an alarming rate. So what can you do? To help, we’ve found some great links to help you plan your course of action:

• Volunteer your Vacation to Save a Wetland: Earthwatch.org is an organization that actually pairs researchers with volunteers in all kinds of habitats. Go to the webpage and search wetlands. You’ll see all sorts of trips planned. They change all the time so search often.
• Donate $$$ to a Charity: We’ve linked here to the Common Sense Environmental Fund that funds research and conservation projects. You give your money to them, and they pick the most qualified conservation initiatives to help fund.
• Join a Wetland Monitoring Group: The Izaak Walton League can help set you up with a local group. Give them a call at 1-800-BUG-IWLA.
• Reduce, Reuse, and Recycle: This is a no-brainer, but we might as well remind you. Everything you can do to reduce your trash will trickle down to less waste in our waterways, including wetlands.
• Be creative, and explore your own wetlands. Find something that you can do like setting up bird shelters, picking up trash, or just monitoring a wetland month to month. You’ll find that you’ll enjoy the time you spend at your wetland, and you’ll want to do everything you can to keep it just like it is.

For further information log on website :
http://www.untamedscience.com/biology/biomes/wetlands-biome/

Tropical Savanna Biome

Tropical grasslands (or tropical savannas) are grass-dominated ecosystems with scattered shrubs or trees, which lie in a wide band on either side of the equator. Huge tropical grasslands exist in Africa, Australia, South America, and India, and some well known ones include the Serengeti Plains in Tanzania, Los Llanos in Venezuela and Columbia, and the Everglades in North America.View Biology Item

Warm, Wet, and Dry

Tropical grasslands are often sandwiched between tropical rainforests, which need a lot of rainfall year round, and desert biomes, which need almost no rain at all. They occur where it’s warm all the time (where temperatures rarely drop below 18 degrees Celsius) and where there’s a very rainy and humid wet season, and a drought-like and fire-prone dry season.

Coping with these extremes isn’t easy for the plants of tropical grasslands, but every species has adaptations to help it get by. Many of the grasses are dormant throughout the dry season; the trees often have leaves that fall off during the dry season to conserve water, very thick bark to protect against fire, water storage tissues in their trunks, or the ability to re-sprout really quickly after fire.

Animal Inhabitants

Tropical grasslands support diverse groups of animals, which differ from region to region around the world. The grasses and trees of these ecosystems provide food for many large herbivorous mammals, which in Africa alone include: impalas, eland, gazelles, kudu, buffalo, wildebeest, zebra, rhinos, giraffes, elephants, warthogs, and more. These browsers and grazers manage to co-exist by having different preferences when it comes to food and where and when they eat.

Of course, where there are lots of herbivores, there are bound to be carnivores, too. Lions, leopards, cheetahs, jackals, wild dogs, and hyenas eat the grass- and tree-eaters on the savannas of Africa. Birds of prey, like hawks, eagles, and buzzards thrive in these environments as well, where they have wide, clear views to search for prey, hot air updrafts to help them soar, and essential resting and nesting sites in trees.

One of the most abundant but least seen animals in tropical grasslands is the termite. These ant-sized insects eat dead grass and wood and recycle the nutrients they contain back into the grassland ecosystem. Some species of termite in Africa, Australia, and South America build colossal mud mounds their colonies to live in that can reach more than five meters high!

Looking After Tropical Grasslands

Since tropical grasslands are great at supporting big, grass-eating mammals, they are often used by farmers as grazing grounds for livestock, which can cause them to degrade. Some tropical grasslands have had their makeup of grass and trees change dramatically because animals that wouldn’t usually live there have been forced in. And large areas of tropical grasslands all around the world have been cleared to make way for development. Because of these threats tropical grasslands need protection and careful management so they can remain one of our planet’s vast, complex, and critically important biomes.

Visiting Tropical Grasslands

Want to check out a tropical grassland in real life? Well, here are a few options you could investigate:

Africa

Explore the Serengeti Plains of Tanzania in Africa while you stay in the remote, southern part of these world famous grasslands at Sanctuary Kusini. Incredible wildlife can be seen here all year round.

South America

Head to Venezuela in South America to experience Los Llanos (“the Plains”). The capital of Apure state is a town called San Fernando, and it’s located right in the heart of Los Llanos. Try not to have a close encounter with an anaconda on your Los Llanos adventures!

North America

For something more hands-on, why not travel to the Everglades in Florida and help scientists find out more about this amazing grassland by doing some volunteer research? Everglades Hostel and Tours can help with both interesting work and a place to stay.

For further information log on website :
http://www.untamedscience.com/biology/biomes/tropical-savannas/

Tropical Rainforest Biome

The first thing you’ll notice when you visit a tropical rainforest is the abundance of plants, both in shear biomass and total biodiversity. Plants thrive when the yearly average temperature and precipitation, in the form of tropical rains, is high. Below, we describe their main characteristics, where they’re found, the layers of the forest and some common animals you might see on a visit to this biome.

Characteristics of the Tropical Rainforest Biome

All biomes are characterized by the dominant vegetation. In the rainforest biome there are tall trees and warm temperatures all year. The yearly average rainfall is from 50 to 260 inches. The temperature is warm but not hot. Almost every rainforest you might visit has a temperature range of 93°F to 69°F.  The average humidity is between 77 and 88 percent.

Where are Rainforests Found?

Tropical Rainforests are found in a tropical belt around the equator where annual temperature and precipitation are high. However, rainforests now cover much less of Earth’s surface than they once did.

Biodiversity of Rainforests?

Today, about 6 percent of the surface of Earth is covered in rainforests, and more than half of all the world’s plant and animal species live in them. The shear biomass of plants in the rainforest help produce about 40 percent of Earth’s oxygen.

Estimates of the Earth’s biodiversity originally came from studies in Panama, where tree species were logged and the number of insects within them categorized and counted. Estimates range from 10 to 100 million species on earth, most of them being insects found in the tropical rain forests.

The tropical rainforests have more kinds of trees than any other biome in the world. In a rainforest in South America, scientists counted from 100 to 300 species of tree in 2.5 acre sections of the forest. Not all plants in the rainforest are trees though. While they are the easiest to observe, there is a great diversity of epiphytes, plants that live on other plants, that make the rainforest their home. Plants like orchids live on rainforest trees high in the canopy.

It has been estimated that about 25 percent of the medicines we use come from plants in the rainforest, such as:

• Curare, a tropical vine, is used as an anesthetic and muscle relaxant during surgery.
• Quinine from the cinchona tree is taken to treat malaria.
• Rosy Periwinkle from Madagascar is used to treat lymphocytic leukemia.

The look of a typical rainforest

All tropical rain forests resemble one another in some ways. Many of the trees have straight trunks that don’t branch out for 100 feet or more; there is no sense in growing branches below the canopy where there is little light. The majority of the trees have smooth, thin bark because there is no need to protect the them from water loss and freezing temperatures. It also makes it difficult for epiphytes and plant parasites to get a hold on the trunks. The bark of different species is so similar that it is difficult to identify a tree by its bark. Many trees can only be identified by their flowers.

Despite these differences, each of the three largest rainforests–the American, the African, and the Asian–has a different group of animal and plant species. Each rainforest has many species of monkeys, all of which differ from the species of the other two. In addition, different areas of the same rainforest may have different species. Many kinds of trees that grow in the mountains of the Amazon rainforest do not grow in the lowlands of that same forest.

Visiting The Tropical Rainforests

There is no one place to visit if your destination is tropical rainforests. The crew of Untamed Science particularly like the rainforests of Central and South America, but we have many other favorites as well. We spent nearly 9 months in Panama shooting videos and staying at the Smithsonian Tropical Research facility, Barro Colorado Island (BCI).  The following video is a short glimpse into what BCI is like.

For further information log on website :
http://www.untamedscience.com/biology/biomes/tropical-rainforests/

Boreal Forests – Taiga

The mysterious forests and treacherous quagmires of the far northern latitudes have inspired storytellers for centuries. The Nordic fables that we read as bedtime stories paint a vivid picture of the northern boreal forests. These are the kind of forests where a lost traveler could lay down on a thick bed of moss only to wake up and find himself surrounded by curious gnomes; where trolls guard bridges; where marsh-men are known to drag you into peat bogs and never let you go…

It’s no wonder people respected these forests and feared the creatures that may have lay in the shadows. Large mammals like moose, bears and wolves are commonly found here, and many people actually do get sucked into the bogs and marshes. Beyond these dangers, the forest itself is often dark and mysterious. Thick stands of Fir and Spruce trees create a canopy that blocks most of the sunlight, making it dark and difficult to navigate. Green and black lichens drape themselves from the tall trees like hag’s hair, playing tricks on your eyes, causing you to think very seriously about the existence of wood-goblins…

Wild fantasies and overactive imaginations aside, the boreal forest is the largest terrestrial biome on the planet, with much of it still undisturbed and unaltered by human beings. The bogs and marshes contain plant species with amazing adaptations for survival, and the forest can be truly enchanting, despite the lack of gingerbread-house-dwelling witches.

Where can we find them?

Boreal forests are only found in the northern hemisphere of Earth, mainly between latitudes 50° and 60° N. With short, cool summers and long, cold winters, these forests form an almost contiguous belt around the Earth, sandwiched between temperate deciduous forests to the south and tundra to the north.

Due to the short growing season in these regions, deciduous trees don’t have enough time to regrow their leaves, and very few of them are able to survive. Instead, coniferous trees dominate because they don’t have to regrow their leaves and are better adapted for a colder climate. South of the boreal forest, the growing season is longer, warmer, and better suited for deciduous trees, so temperate deciduous forests dominate. North of the boreal forest, temperatures stay cold enough to keep any trees from growing, and we call this region the tundra. Essentially, boreal forests occur in a “Goldilocks” zone, where temperatures are too cold for temperate forests and too warm to be considered tundra.

Abiotic Factors: Climate

As we have said, boreal forests are characterized by having a very short growing season in which plants only have about 50-100 frost-free days to grow. In these regions, winters can last over 6 months, with average temperatures generally staying around -20° C (-4° F). Summers are short and stay at about 50° F, but can get as high as 80° F in some areas. Precipitation rates are low (~15-20 inches annually) and fall mostly during the summer months. But in these regions, moisture tends to stick around for longer periods of time due to low temperatures and evaporation rates. Therefore, even though these regions receive as little precipitation as some deserts, they remain moist for most of the growing season!

This peculiar, dry-but-moist climate is mainly influenced by the interaction of two air masses during the summer and winter. You can think of “air masses” as big bubbles in the atmosphere that move air and water from one region of the world to another. Those big bubbles of air retain the same temperature and moisture levels as the region where they were “made” and essentially transport weather. For example, air masses that were created in arctic regions tend to be cold (for obvious reasons) and dry, because water does not evaporate into the air as much in the Arctic. So, when the arctic air mass moves to another region, it brings cold, dry weather with it. During the summer in the boreal forest, warm, moist air from the Pacific air mass moves north, bringing warm weather and rain. During the winter, cold, dry air from the Arctic air mass pushes south, into the boreal forest, causing the cold, dry winters.

Snowy Boreal Forest 
Interestingly, when temperatures start to drop in the fall, the snow that falls on the taiga actually helps to keep it warm! The thick snow drifts that accumulate in the forest insulate the ground below them like a thermos, allowing the soil temperatures to stay above freezing, while the air above them is well below it.

Abiotic Factors: Soil

One of the most important abiotic factors in any forest ecosystem is the condition of the soil. Factors like nutrient levels, moisture content, and decomposition rates determine what plants are able to grow there. The boreal forest soils are what soil scientists call spodosols and are considered to be very hostile soil conditions. The word “spodosol” comes from a Russian word meaning “under ash” and refers to a layer of gray, nutrient-poor soil beneath a thin layer of organic material. In soils like this, water leaches through the upper layer of sandy soil quickly, dragging almost all available nutrients with it. Then, the decomposed material (organic nutrients) and fine grained quartz (sand and clay) that leached through the soil are broken down and chemically altered to form a layer of gray, nutrient-poor clay.

Not only is the soil lacking vital nutrients for plant growth, but coniferous trees poison it to keep other plants from sprouting! The needles from coniferous trees in these forests contain a high concentration of resins, oils and other chemicals that can help prevent them from freezing solid in the winter. When they fall off the tree, though, all of those chemicals leach into the soil, making it very acidic and often toxic to other plants.

Finally, remember that evaporation does not happen very quickly in a boreal forest. The little precipitation that does fall in these forests accumulates in the soil, decreasing the amount of available oxygen and slowing the rate of decomposition. Put it all together and you get a poisonous, acidic soil that leaches the few nutrients it has available for plants to grow; harsh conditions indeed!

What do they look like?

Types of Taiga: Light and Dark

Like fine chocolate, boreal forests come in two flavors: light and dark. The dark taiga is commonly found in the southern range, where the climate and soil conditions are more favorable for plants and thick stands of Spruce and Hemlock create a closed canopy. The light taiga is found more often in regions where the soil is too nutrient-poor to support as many trees. In these areas, Pines and Larches are spread further apart and create an open canopy.

Oddly enough, the dark, dank, spooky forests described in Nordic fairy tales are actually more supportive of life than the bright, open pine forests of the light taiga. While both versions of the boreal forest have low biological diversity, the soils of the dark taiga tend to be more nutrient-rich and thus more supportive of plant life. In areas where light can penetrate the canopy, the herbaceous layer of the forest can be downright lush; filled with ferns, Fireweed, Shrub Alders, raspberries, salmonberries, blueberries, black currant, red currant… (It’s no wonder the bear poop here is filled with fruit seeds!) On the other hand, the light taiga has drier, more infertile soil and a more open understory.

Why so Coniferous?!

Conifers like Pine, Fir, Larch, Spruce, and Hemlock are are well adapted for harsh conditions and are the dominant trees species in the boreal forest. As opposed to deciduous trees, which lose their leaves as soon as it gets cold, conifers retain their needles throughout the winter. The dark green needles help to absorb heat and allow them to begin photosynthesis as soon as temperatures rise above freezing. Needles also help to prevent water loss because the stomatal openings (pores that exchange gas and water) are positioned on the underside of the needle, underneath a waxy cuticle.

In the winter, when heavy snowfall accumulates, their conical shape helps to shed snow and prevents branches from breaking off. To combat temperatures well below freezing, conifers produce resins and other chemicals that act like antifreeze and keep the tree from freezing solid in the winter. When the needles fall off the tree, the chemicals that helped them resist freezing leach into the soil. This helps the tree outcompete other plants by creating a toxic environment in the soil, an adaptation called allelopathy.

Other Plant Adaptations

While conifers are the dominant tree species, some deciduous trees have found a foothold in the boreal forest, despite the cold, infertile conditions. Trees and shrubs of the genus Alnus (Alder) have bacteria-filled nodules in their roots which help to convert atmospheric nitrogen into useable nutrients, feeding not only themselves but the plants around them as well. Other deciduous trees like Willow and Aspen require a large amount of water to grow and can be found where soil moisture levels are too high for conifers.

Other plants have found ways to get the nutrients they need without having to gather much from the infertile soil. Sun Dew and Pitcher Plants are carnivorous plants that you may spot in the bogs and fens of the taiga. These plants get nutrients by trapping and digesting insects and other arthropods.

Ancient History and Succession

Given Earth’s loooong geologic history, our boreal forests are relative newcomers to the world biome scene. This is not to say coniferous forests like this haven’t existed before. They have. Just not where you would expect them to be. This is because throughout Earth’s climatic history, temperatures have fluctuated regularly, and glaciers have expanded and retracted over enormous distances. Approximately 20,000 years ago, when ice sheets were at their last glacial maximum, tundra and permafrost covered much of what is now boreal forest, and coniferous forests grew where we now see temperate deciduous forests. As the glaciers retreated, they literally paved the way for modern boreal forests.

Glaciers, Lakes, and Bogs

As the glaciers retreated north, they scraped and gouged the Earth below them, leaving behind vast expanses of tundra and landscapes pockmarked with deep depressions. The tundra eventually gave way to coniferous forests when the temperatures were right, and the depressions filled with water, forming thousands and thousands of glacial lakes. In the northern latitudes, a unique moss called sphagnum moss helped to drastically change the landscape.

Sphagnum moss is crazy awesome, y’all. It is most often found along the edges of lakes and bogs, where it absorbs an unbelievable amount of water. (One ounce of dry sphagnum can hold almost a pound of water!) As more and more sphagnum builds up around the lake, some of it dies and begins to decompose. Remember that decomposition is a slow process in the Boreal forest, due to acidic and oxygen-poor conditions. When sphagnum decomposes under these conditions it turns into peat, a rich organic sediment, which accumulates around the lake’s edges and fills in from below. When enough sphagnum moss and peat have displaced the water in a lake, it can be called a bog. When the peat layers displace all of the water in the bog, trees are able to take root, and eventually, boreal forest takes the place of the bog. The eventual succession from bog to forest can take a very long time because the soil conditions in a bog are even more acidic and oxygen-starved than the boreal forest. Due to the extreme acidity and low oxygen conditions in a bog, they usually host a very unique set of plants which are adapted to the most extreme conditions. Cranberries, lingonberries, and dwarf blueberries are small, tart berries that do well in these conditions, and can be a sweet treat for a bog-traveler, if they don’t get pulled down by subterranean marsh kings first!

Actually, marsh kings don’t really exist (as far as we know), but bogs can be dangerous places to wander if you aren’t careful. The real reason is the peat layers at the bottom of a bog can be deceptively deep. If you stepped in an area where the peat was not fully compact, you could end up sinking up to your waist, or deeper, and be unable to climb out.

Common Disturbances

Boreal forests are not as long lived as many old-growth deciduous forests. While many stands of boreal forest can reach a mature age, frequent disturbances often keep the forest from reaching late successional stages. Insects are one of the most common disturbances that keep these forests from getting too old. In North America, for example, Spruce Bark Beetles are responsible for killing millions of mature Spruce trees every year. The beetles dig their way in between the bark and wood of the tree, eating away the cambium layer. Eventually, the tree is unable to transport its nutrients and it dies. While the beetle attacks both young and old trees, young trees are able to defend themselves more readily than mature trees, and are less affected by beetle infestations. While beetle infestations are a natural component of the boreal forest, global climate change has allowed them to speed up their life cycle, and damage from beetle attacks has escalated as a result.

Fire is another common disturbance in the dry areas of a boreal forest. In this case, mature trees normally survive the blaze, but young trees and ground cover burn quickly, recycling their nutrients back into the soil. Working in tandem, these disturbances keep the forest young and healthy.

For further information log on website :
http://www.untamedscience.com/biology/biomes/taiga/

Temperate Deciduous Forests Biome

Not every region of the world experiences a change in seasons like the temperate deciduous forests. Some are always blanketed in ice, while others have warm sunshine year round. For those of us who live in temperate regions, seasonal changes happen every few months. You could be darting across a lake on water skis in July, and, 6 months later, you could be racing across that same lake on ice skates!

There is no season such delight can bring, as summer, autumn, winter, and the spring.
William Browne – “Variety”

When you grow up experiencing four seasons every year, you begin to notice and appreciate the seasonal ebb and flow of life around you. Winter is peaceful and quiet; critters that don’t migrate stay hunkered down in warm dens, waiting for the spring (Humans included!). Spring is a welcome awakening; as the snow melts away and leaves begin to bud on the trees, life reappears and prepares for a new year. Summer is a bustle of energy and life; insects are busy pollinating the next generation of wildflowers, and birds sing from every corner of the forest. Autumn is a time for harvesting and a time for goodbyes; mammals fatten themselves up to prepare for a winter food shortage, and birds of a feather flock together to follow their food south.

For many of us, seasonal change is old news. It drums along at a steady, predictable rhythm. But few people realize that this predictable pattern is what has allowed temperate deciduous forests to evolve and flourish all over the world.

Temperate Deciduous Forest in Virtual Reality – 360 Degrees

The following video is a short we shot for you to see this deciduous forest biome in 360 degrees. If you are on a mobile device you may have to open the youtube video in the mobile youtube app to see it in virtual reality. If it looks funny, its because the system you’re on doesn’t support this viewing experience.

Where Can You Find the Temperate Deciduous Forest Biome?

When you look at a map of of the world, lines of latitude run east and west, forming invisible belts that circle the globe. These lines of latitude can be grouped into three different categories as you move away from the equator. Regions that lie between 0° and 23° north and south latitude are called the Tropics, regions between 23° and 66° are called the Temperate latitudes, and regions between 66° and 90° are called the Polar latitudes. Temperate deciduous forests are found within the temperate latitudes, just like Tropical Rainforests are found within the Tropics (makes sense, right?).

In the southern hemisphere, temperate forests can be found on the southern tip of South America and in Eastern Australia. In the northern hemisphere, they can be found in northeast Asia (China, Korea and Japan), Western Europe, and the eastern third of the United States.

Abiotic Factors: Temperature and Precipitation

Temperate climates (and all other climates for that matter) are influenced in large part by circulating air currents in the atmosphere. Watch this animation of global air circulation and try to locate regions of the world where the clouds accumulate:

As you can see, most of the clouds accumulate along the equator. This is what scientists call a low-pressure zone. (Clouds just can’t handle high pressure situations.) Low-pressure zones are regions of high precipitation. If you watch carefully, you can spot another low-pressure zone in the temperate latitudes.

Due to their global position, temperate forests generally receive about 75-150 cm of precipitation every year (That’s a lot, second only to the Tropics). Remember, though, precipitation can fall in the form of rain or snow because temperate climates experience all four seasons. Temperatures can range from -1°C to -30° C in the winter and 27° to 32° in the summer.

What do they look like?

Temperate deciduous forests are among the oldest and most beautiful forests in the world. Take a walk through the northern hardwood forests of Wisconsin, or taste the sap from a Sugar Maple stand in Vermont, and you will know exactly what I mean. As you walk, tall trees form a leafy canopy above your head, blocking the sun and casting dappled shadows over ground. Leaves from last season crunch noisily underfoot as you scrape through a thick, woody understory. If you dig into the ground, you pull through layer upon layer of wet, decaying leaf litter, and white threads of fungus stand out against the dark soil. Fungus, bacteria and insects underground decompose fallen leaves and organic matter quickly, producing a thick layer of nutrient rich soil, which scientists call humus (Not to be confused with hummus, Yum!). The humus feeds the trees and supports a biodiverse community of lichens, mosses, grasses and wildflowers on the forest floor.

Not all temperate deciduous forests are created equally, though. Every forest you visit can differ greatly in the species of plants that populate it. In the same way that the Earth can be classified into separate biomes, where specific groups of plants and animals exist within a regional climate, temperate deciduous forests can be classified into different communities depending on the local climate.
Click here to find out more information regarding specific temperate forest communities!

What types of plants can you find here?

You may hear temperate deciduous forests also called “broadleaf forests,” because the tree species that populate them have… wait for it… broad leaves! Trees like Maple, Oak, Beech, Chestnut, Elm, Hickory, ect. have big, broad leaves that are attached to the branch by a special stem called a petiole. Unlike pine needles, these leaves are soft and easily digestible to browsing herbivores.

In a mature forest, these tall trees form a canopy which blocks most of the sunlight from penetrating through to the plants below. To compensate, the plants that make up the understory and herbaceous layer are shade-tolerant, meaning they can survive with a lower amount of sunlight. Due to the seasonal nature of temperate deciduous forests, many of the plants in this region are perennial, meaning they grow and flower only during the warm, summer months. Thick, woody shrubs like rhodedendron, buckthorn, sumac, honeysuckle, or dogwood dominate the dense understory. This region of the forest is generally the most biodiverse area of the forest; a single forest can have over a hundred different species of plants! Throughout the early spring and summer, shade-tolerant herbs and wildflowers like Jack-in-the-Pulpit, May-apple, Bedstraw, Purslanes, and mustards flower and go to seed within a few weeks to months.

What does “Deciduous” mean?

The term deciduous refers to the plant’s ability to lose it’s leaves when times get tough. For example, some species of trees and shrubs in the chaparral are called drought-deciduous, which means that they lose their leaves in the dry season to conserve water.

Deciduous trees in temperate forests lose their leaves in the fall to better survive winter conditions like extreme cold and reduced daylight. For a more detailed explanation of how trees lose and regrow their leaves, check out Rob and Jonas’ video on plant hormones here!

The ability for a tree to lose its leaves to conserve energy is a useful but costly adaptation. As opposed to evergreen trees, deciduous trees have to regrow thousands of leaves every year. This requires the plant to take precious nutrients from the soil to make them. In some temperate regions, if the soil is too dry or nutrient poor to afford the cost of new leaves, the populations of plants change to suit the environment. For example, in many temperate regions of the United States, the soil is too sandy and nutrient poor to support many deciduous trees and evergreen trees are a big part of the forest. In areas like this, we call it a “temperate broadleaf mixed deciduous forest”. Yes, the names can get complicated…

Why do the leaves change color?

Temperate deciduous forests are famous for their dramatic color change that occurs every fall. Amazingly, this seasonal effect begins within each cell of every leaf on the tree! To help you understand this better, picture each plant cell as a jar full of red, yellow, and green beads. If there were more green beads than anything else, the jar would appear green. If you took all of the green beads out, the jar would appear red and yellow.

This is essentially what happens within each cell of the plant every year. As the days get shorter and the temperature drops in the fall, plant cells stop producing green pigments (chlorophyll) in the cells of their leaves. When the cells stop producing chlorophyll and the green pigment slowly disappears from each cell in the leaf, other pigments become more vibrant, and the leaves begin to appear yellow, red and orange.

Every year, hundreds of extraordinary migrations occur all over the world: The Swallows of Capistrano, the Monarch Butterflies from Mexico, and of course, The New England Leaf-Peepers. Every year, thousands of New Yorkers and Bostonians make the long journey north to watch the leaves change color; truly this one of nature’s most beautiful spectacles (the leaves, not the city people).

Temperate Deciduous Forests Through Time

As we have said, in a typical temperate forest, tall trees create a thick canopy that blocks most of the sunlight from penetrating. This creates a layer of shade-tolerant herbs and shrubs in the understory. But what happens when the trees fall down? What if a fire burns hot enough to turn everything into ash? What if a tornado sweeps through and delivers everything to the Land of Oz? (It happens you know…) Here, we will talk about how these forests change over time and what happens after a disturbance.

Forest Succession

Forests, like any other living thing, grow old and change over time. In fact, every forest you see was once a pile of bare rock! Slowly, lichens and mosses grow over the rocks and decay to form a layer of soil that is capable of supporting grasses and wildflowers. At this point, our temperate forest is not a forest at all, its a grassland! Temperate deciduous forests and temperate grasslands are almost one and the same. The two are often found right next to each other and share many of the same plant and animal species.

Over time, tree seeds from the forest make their way to the grassland and begin to sprout. As the trees begin to shade out the plants under them, the grassland begins to resemble a forest more and more. Grasses in these habitats are not very shade-tolerant. As more trees sprout up, fewer grass seeds are able to germinate, and they remain dormant in the soil until conditions are right again.

At this point, more shade-tolerant herbs and shrubs are able to grow, and they create a thick understory in this young forest. When the majority of the trees in the forest have reached a mature age, we call it a climax community. Forests that have reached this stage in development are also called old-growth forests, for obvious reasons. Many of the old-growth forests in the United States have been cut down to make space for cities and to make use of the valuable timber. But some old growth forests remain in northern Wisconsin, Michigan and Minnesota, and given enough time, more will grow again!

Natural Disturbances

What makes a temperate forest different from a temperate grassland? Sunlight! Grasslands receive a lot of it; forests do not. Now, imagine a tree falls in the woods (don’t worry about whether or not you can hear it…) Suddenly, the canopy opens where that tree has fallen and light pours into the forest. When this happens, seeds that have been dormant in the soil are finally able to germinate again. Grasses, flowers and other fast growing plants quickly sprout up and take the place of the fallen tree. Over time, new trees will grow up tall enough to shade these plants out again, but that could take years. In the meantime, these areas of the forests remain sunny oases of diverse plant life!

Tree falls, fires, tornadoes and insects are common natural disturbances in these forests. Every time something like this occurs, the forest rebounds within a few years. Sometimes it begins at an earlier successional step, and sometimes the disturbance is just what it needs to clear out the excess and keep the forest healthy.

For further information log on website :
http://www.untamedscience.com/biology/biomes/temperate-deciduous-forests/