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Deciduous Forests Deciduous Forests

The temperate deciduous broadleaf forest (TDBF) is composed of broad-leaf angiosperm trees like the oaks, maples, and beeches familiar to many Americans and Europeans. The forests exist best in moderate climates that are neither too hot nor too cold and neither too wet nor too dry. In addition to the temperate zone, deciduous forests are found in tropical and sub-tropical climates in open savannas and/or in closed forests. While there are roughly thirty families and sixty-five genera in the TDBF, variation in the precise definition and defined area of the forest make absolute numbers impossible. With thousands of species, the TDBF is a highly diverse biome. Worldwide, there are five major groups of TDBFs. Within each group, botanists define TDBFs by the species that tend to occur in a given area. These collections of species, together with their environment, are called associations. Eastern North America today contains the most extensive TDBF. The forest reaches from about longitude 95°W (just west of the Mississippi River) to the Atlantic coast and from 30 to 45°N, thereby forming a quadrant that includes most of the northeastern quarter of the United States. The eastern United States TDBF was almost completely deforested for agricultural purposes by 1850. At that time, land was opened for agriculture in the Mississippi valley, and many farms were abandoned. Pines grew well in the remaining grassy fields, but after a catastrophic hurricane in 1937, the TDBF grew back. Today, there is much more TDBF in the United States than there was one hundred years ago (though still less than before the arrival of European settlers). There are nine generally recognized associations in the United States TDBF, each defined by differences in vegetation (see accompanying table). Though the species are representative of common dominants, many other species exist. TDBF associations are not completely separate. Many species, such as northern red oak and sugar maple, exist in more than one association. Nor are the boundaries between the associations sharp and easily identifiable. In particular, the Western Mesophytic association can be difficult to distinguish from its neighbors to the east (Mixed Mesophytic) and west (Oak-Hickory). Associations can change with time too. The Oak-Chestnut association is now almost completely devoid of chestnut, but many people still use the association name even though it is now mostly oak and maple. Association names in North America and elsewhere are most useful for distinguishing broad differences in forest type often associated with variation in soils, topography, and climate. The European TDBF, stretching through most of Europe (except for very hot and cold areas) from the Atlantic Ocean to the Ural Mountains, is the second-largest TDBF. Due to the moderating influences of the Gulf Stream, the TDBF exists as far as 60°N in northwestern Europe. Forests in Europe have been extensively modified by humans for more than two thousand years and are some of the most manipulated forests in the world. In the northern European TDBF, birch species are common, while in the middle European latitudes, beech (Fagus sylvatica ) is widely distributed and commercially valuable. Towards the south, various oak and maple species abound. As in North America, much of the once-cleared TDBF is now regrowing. The European TDBF is replaced by drought-resistant shrubs and evergreen broadleaf trees in the south and the boreal coniferous forest in the north. The last three TDBF areas are much smaller than the first two. East Asia, from 30° to 60°N and from central Japan to longitude 125°E in the northwest and longitude 115°E in the southwest, originally maintained very large forests. Today, even though the species mix is still very diverse, much of the East Asian forest outside of Japan is currently under cultivation and most existing forest fragments are protected refuges or in areas unsuitable for agriculture. Nearly all TDBF genera are present in East Asia, especially China. The Near East between 35° and 45°N, including areas around the eastern Black Sea and mountainous regions in Iran and near the Caspian Sea, supports a diverse TDBF. Finally, a narrow strip of South America including southern Chile and Argentina contain TDBF. Acacia caven and seven Nothofagus species are also found there. In nearly all cases, the deciduous trees of South America occur in mixtures with evergreen broadleaf species. Of the three major TDBFs, East Asia has by far the greatest diversity, followed by North America and Europe. East Asia was glaciated less severely than America and Europe, so most species were able to survive with little difficulty. In North America, the north-to-south orientation of major mountain ranges allowed species to migrate, and species diversity here is only slightly lower than in East Asia. In Europe, on the other hand, the east-to-west mountains caused the TDBF to be trapped by advancing glaciers. Many modern European TDBF species survived only in the Near East TDBF and migrated back after the glaciers retreated. Consequently, Europe has very low-species diversity. TDBFs are generally restricted to a warm temperate climate with four identifiable seasons in which the average temperature of the coldest month is between 3 and 18°C and the average temperature of the warmest month exceeds 10°C. The length of the frost-free period ranges from 120 to over 250 days. Precipitation is year-round and averages between 80 and 200 centimeters per year. Snowfall can range from nonexistent in the southeastern United States to extremely heavy in northern habitats. Climates that are wet and warm all year are occupied by tropical forest consisting of broadleaf evergreen trees. As climates become drier, as occurs at the western edge of the Oak-Hickory association, drought stresses are too extreme for TDBF and grasses become dominant. To the north of the major TDBF, extreme cold, short growing seasons and poor soils favor evergreen coniferous forests. TDBF soils tend to be deep and fertile and, unlike some soils in the northern coniferous forest, do not freeze year-round. For this reason, TDBFs have historically been popular for agricultural use. Deciduous leaves are the most distinctive feature of the TDBF. In the fall, spectacular reds, oranges, and yellows produce breathtaking displays across the TDBF. Why does this occur? During autumn, as temperatures cool and days shorten, trees send hormonal signals to their leaves causing them to turn colors and fall off the branch. First, leaves form a barrier between the leaf and the branch, known as the abscission layer. At the same time, chlorophyll, the compound that gathers light for photosynthesis, begins to degrade in the leaf. Many of the nutrients in the leaf are sucked back into the tree for next year's leaves. Chlorophyll is responsible for the usual green leaf color: once it is gone, yellow and orange pigments that were there all along become visible. Some of the sugar in the leaves of oaks and maples may be converted into red colors. Once the leaf is totally shut down and no longer conducting any photosynthesis, the abscission layer becomes very brittle. Any small breeze can snap the leaf off at this point. In the spring, using carbon from special storage cells in the trunk, trees grow a new batch of leaves. In an evolutionary adaptation designed to maximize the amount of light received, shrubs and small trees growing in the understory will begin growth before the overstory. The study of any recurring biological cycle and its connection to climate is called phenology. Patterns of bird migration and insect outbreaks are examples of phenological cycles. For centuries, scientists have been studying phenology in the TDBF. In the deciduous forest, phenology refers to the timing of spring leaf growth and fall leaf drop and their relationship to climatic variation. Observational evidence has shown that TDBF phenology is highly sensitive to variation in weather. Warm springs will cause leaves to grow earlier, sometimes by up to as much as one month. Conversely, plants respond to a cold fall by dropping th

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Question:I really need help with these questions about plant cells... if someone can answer all or the ones they know, that would be GREAT!! pleasee & thank you =) 1. What is the advantage of a flat, thin leaf blade to the photosynthetic capacity of a plant? 2. How does the arrangement of leaves on a stem relate to the photosynthetic capacity of a plant? 3. Which cells in the leaf are the main photosynthetic cells? How do you know?? 4. Leaves need carbon dioxide, water, minerals, and sunlight for photosynthesis. How does the leaf get each of these? 5. Leaves make sugars and oxygen. Where do each of these go? 6. Many house plants have very small, thick, waxy leaves and few stomates. They do not wilt as quickly as houseplants with thinner leaves. Explain why. What climate might these plants be best adapted to live in? 7. Describe the leaves of a plant that is adapted to live in the rainforest.

Answers:The advantages to a flat thin leafs blade is that the green chlorophyll has more exposed surface area to absorb sunlight and allows for photosynthesis to take place and more progressively than in smaller leaves with less surface area, however its less adventitious because, the more surface area a leaf has the more likely it will lose moisture( why needle leaves off of Christmas trees have needs is to conserve moisture, though non rainy or snowy times. ) 2. More leaves, that are separated, greater result of photosynthesis, more tightly nit leaf system, greater result of containing water. 3. The photosystetic cells are chlorplast cells, there green. and what gives plant leaves their color 4. Leaves in plants, go through a process called photosysthesis. Thats when light reacts with chloroplasts on the leaves surface(light is energy source) and takes in water from the leaf (through the xylem) and Carbon dioxide from the air [animals do a similar process, which is called cellurlar respiration in which we release as a product the Co2 that the plants require into the atmosphere(air)] and Creates food for itself (carbohydrates or sugars) and releases as its product Oxygen. 5. The oxygen is released in the air, just as when humans undergo cellular respiration we expel into the air Carbon Dioxide. The Sugar or C6 H12 O6(glucose) is taken in by the plant at the cellular level. and can be transported around the plants cells via the phloem. 6. The stomata in a plant are tiny openings along the leaf surface, water is "perspired" (like human sweat) though the stoma openings along the leaf surface, the more stomas the more opening, the more openings the more likely the plant will dehydrate and wilt. The waxer or smaller the leaves the more likely they are to keep there water. and Maintain healthy leaves. At present there are three classifications of leaves, according to plants leaves surface area(how large the leaves are), and according to stomas. The few stoma openings are more suited to live in dry areas, like cactus.(Xerophyte) Water lilies and things would have broad large leaves, to absorb as much water as possible(hydrophyte). and a mesophyte is the inbetween. Probably the most common form of house plant. Thought I am not completely positive. Also check spellings. 7.As for the rain forest question, best bet is Large broad leaves which would make for lost of surface area for photosystesis, and also would absorb lots of water when it rains. I'm not positive on the last question, but fairly certain of the rest, I've been doing biology as a major, but Herbology is not my speciality. So DOUBLE CHECK!.(plus I suck at spelling) Hope it helps!!!

Question:xerophytes are plants adapted to dry conditions hydophytes are plants adapted to living in water mesophytes are plants adapted to neither a particularly dry nor particularly wet environment. the plants are: spinach umbrella plant lettuce tradescantia peace lily money plant eucalyptus ivy geranium actually can you tell me which (if any) are hydrophytes

Answers:lets see 1st one is an mesophyte 2nd is an mesophyte 3rd one is an mesophyte well donot know all surley but i think peace lilly is an hydrophyte,money plant a mesophyte,eucalyptus a mesophyte too thats it i know i think some may be wrong but i m 89% sure

Question:something about ephiphytes,mesophytes,xerophytes,hydrophytes etc

Answers:epiphyte adaptation: xerophtytes adaptation: 1.waxy stomata prickly pear 2.few stomata 3.sunken stomata pine 4.stomata open at night tea plant 5.CAM photosynthesis eg. cactus 6.large hairs on surface eg. Bromeliads 7.curled leaves eg.esparto grass 8.Storage of water succulent leaves eg. Bryophyllum 9.succulent stems eg. Euphorbia 10.fleshy tuber eg.Raphionacme 11.Water uptake deep root system eg. Acacia 12.below water table eg.Nerium oleander 13.laterally extensive, shallow root systems eg. cactus absorbing surface moisture from leaf hairs or trichomes Tillandsia Importance of water conservation mesophytes adaptation: Mesophytes are terrestrial plants which are adapted to neither a particularly dry nor particularly wet environment. An example of a mesophytic habitat would be a rural temperate meadow, which might contain Goldenrod, Clover, Oxeye Daisy, and Rosa multiflora. Properties: Mesophytes generally require a more or less continuous water supply, and have only basic features for water conservation, such as a cuticle and stomata. They usually have larger, thinner leaves compared to xerophytes, sometimes with a greater number of stomata on the undersides of leaves. Because of their lack of particular xeromorphic adaptations, when they are exposed to extreme conditions they lose water rapidly, and are not tolerant of drought. hydrophytes adaptation: Characteristics of hydrophytes: 1.A thin cuticle. Cuticles primarily prevent water loss, thus most hydrophytes have no need for cuticles. 2.Stomata that are open most of time: so water is (abundant). This means that guard cells on the stomata are generally inactive. 3.An increased number of stomata, that can be on either side of leaves. 4.A less rigid structure: water pressure supports them. flat leaves on surface plants for flotation. 5.Air sacs for flotation. 6.Smaller roots: water can diffuse directly into leaves. Feathery roots: no need to support the plant. Specialized roots able to take in oxygen.

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