Chapter 7, Problem 5CR

To determine

The differences between three types of desert, the vulnerability of desert ecosystems, survival mechanisms of desert plants and animals. The difference between the three types of grasslands, savanna. The methods by which the animals survive seasonal variations in savanna rainfall, the importance of elephant in the African savanna. Contributions of Tuy Sereivathana in preventing the extinction of elephants. The disappearance of temperate grasslands, arctic tundra and permafrost.

Three types of forests and their differences, high biodiversity in tropical rain forests, soils with fewer nutrients in tropical rain forests. The presence of a thick layer of decaying litter in temperate forests. Coastal or temperate rain forests. Survival mechanisms of coniferous evergreen trees in cold winters and ecological role of mountains.

Answer to Problem 5CR

The desert ecosystems are vulnerable due to harsh conditions. The desert plants and animals survive by conserving water and storing food.  The savanna is a mixed grassland with alternating warm and wet climate. The animals survive seasonal variations in rainfall by grazing more during the rains and saving it for warm seasons.

Elephants are important as they prevent overgrowth of plants and protect grasses from drying, they also dig water to maintain water supply in drought. Tuy Sereivathana helped prevent elephant extinction by educating farmers on how to deal with elephants rather than killing them for the protection of their food. The temperate grasslands have disappeared due to overgrazing and turning the areas into agricultural lands. High biodiversity in tropical rain forests is due to favourable climate and high rainfall.

Soils in tropical rain forests have low nutrient as the nutrients are stored in plants rather than in soils. The thick layer of litter in present in temperate forests as the cold temperature slows the decomposition of dead matter. The coastal or temperate rain forests are tall trees that thrive in warm summers and cold winters. The coniferous trees survive by modifying their leaves into needle shape to prevent accumulation of snow. Mountains help in regulating climate and sea level, it also protects valleys from harsh weathers.

Explanation of Solution

The three types of deserts that differ in terms of climate and vegetation are as follows:

No.	Characteristics	Tropical desert	Temperate desert	Cold desert
1	Climate	The tropical deserts are very hot and dry for the most part of the year. Rainfall is very less.	The temperature of the temperate deserts is high in summer and low during the winter time, however, rainfall is more than tropical deserts.	The temperature of the cold deserts is very low in winters while in summer it is relatively warm. The rainfall is low.
2	Vegetation	The vegetation is mostly a few plants that are hard to withstand the high winds carrying sand.	The vegetation is sparse that is dispersed and is adapted to tolerate drought. The main plants are shrubs, cactus and other succulents.	The vegetation is sparse in nature. The main plants include small plants with spiny leaves, pine, spruce and so on.
3	Examples	Sahara desert, Namib of Africa.	Deserts in Atacama, Chile, Great Basin and so on.	Gobi desert in Mongolia

The desert ecosystems are more likely to experience long term damage as the conditions of the desert ecosystem are harsher than any other ecosystem. The vegetation is low and the animals living in the ecosystem are also few that mainly consists of grazing herbivores. The rainfall ranges from low to very low around the year. The soil is not very fertile so the cultivation is not possible; the dry and hot climate makes it difficult for other types of plants and animals to survive in such conditions. Therefore, the conditions of the ecosystem make it more prone to damage from sandstorms, drought and so on and due to low water levels in the ground, it is difficult for the desert areas to cope with the damaging conditions.

The plants and animals in the desert survive mainly by conserving water in their bodies. The plants in the desert are mainly succulents that have modified fleshy stems to store a large amount of water. This prevents them from drying up in a hot climate with less rainfall. Whereas the animals also have modified systems to conserve water, like an excretion of more concentrated urine, large capacity to store water, for example in camels, and scarce body fur to prevent the body temperature to rise more than required. The animals in the desert also adapt a nocturnal mode to hunt at night and preserve energy and water during the day.

The difference in the climate and the vegetation of three types of grasslands are as follows:

No	Characteristics	Tropical grassland	Temperate grassland	Cold grassland
1	Climate	The tropical grassland faces extreme hot and dry climate.	In such grasslands, the winters are bitter and cold while the summers are dry and hot.	The arctic tundra or cold deserts are very cold during the year, with bitter and harsh cold winds, the areas are covered with snow and ice. The day has a few hours of sunlight.
2	Vegetation	The vegetation mainly consists of small plants, succulents, cacti and so on.	The plants include small shrubs, some crop plants, grasses and so on.	The areas are mainly treeless however, some low-growing plants are present like mosses, lichens, grasses and shrubs.
3	Examples	African savannas.	Veldts of Africa.	Alpine tundra, arctic tundra

Savanna is a mixed grassland ecosystem that has alternating warm and wet climates. The grassland includes the mixed type of vegetation that ranges from the small desert plants to shrubs and some trees in the wet climate. The animals that inhabit are grazing herbivores like gazelles, zebras, giraffe and elephants. The predators are lions, humans and hyenas.

During the rainy seasons, the different types of grasses and shrubs grow and are able to cope up with seasonal fires. The animals return to their grazing activity as during rains the vegetation is abundant to store food and prevent them from dying in the drought.

Elephant serves as the keystone species in the savanna, as these are less in number among other herbivores but their existence influences the climate and the geography of the grasslands. They feed on woody shrubs and young trees. This aids the areas from being to have an overgrowth of woody plants and also ensures that the grasses do not die out. If the grasses would die out the herbivores and their subsequent predators would also leave the grassland for the search of food and water. The elephants also help in digging water from underground to provide water to all animals during drought conditions. They are a crucial part of the food web and so prevent it from collapsing.

Tuy Sereivathana has played a pivotal role in doubling the population of the Asian elephant that has been endangered due to hunting and deforestation. He has also helped the farmers of Cambodia to establish a nighttime lookout for the elephants so that they do not attack the humans that lead to the killing of elephants.

Many of the temperate grasslands have disappeared due to the high rate of grazing by herbivores that have removed the plants and grasses from the area. The dead and decaying plants have made the soil fertile which has to lead to their use by farmers for cultivation and turn them into agricultural lands. This has lead to the loss of temperate grasslands.

Arctic tundra is cold grassland that has very bitter cold and low vegetation, the plants found are mainly mosses, lichens, shrubs, small pine leaf plants and so on. The permafrost is the condition when the soil present underground surrounded by water stays frozen for more than two successive years.

No	Characteristics	Tropical rainforest	Temperate deciduous forest	Northern coniferous forests
1	Climate	Climate is warm and moist and receives high rainfall during the year.	They are warm in summers and face cold winters. They have abundant rain in summers and snow in winters	They have a cold and moist climate. Winters are long and summers are short and cool.
2	Vegetation	The forests are densely covered with tall trees and have very high biodiversity.	They have broadleaf deciduous trees like maple, aspen, oak, birch, hickory and so on.	They have spine leafed conifers like cedar, fir, spruce, hemlock and so on.

The biodiversity is high in tropical rain forests as the climatic conditions are favourable for the growth and development of flora and fauna. The area receives high rainfall throughout the year that promotes the growth of tall plants, the forests also receives abundant sunlight, carbon dioxide to carry out photosynthesis. For animals, the dense forest cover and abundance of vegetation allows high reproduction rate and safety from outside predators like humans.

The soils in tropical rain forests have few plant nutrients because most of the nutrients are stored in the plants that have already extracted the mineral from the soil for their growth. The only means of replenishing the soils with nutrients is through the decomposition of dead and decaying plants and animals.

The temperate deciduous forests have a thicker layer of decaying litter because they have cooler temperature which slows down the decomposition process when compared to other forests like tropical rain forests. This makes the rate of production of the dead organism more than the rate of decomposition leading to the production of a layer of decaying litter.

The coastal coniferous or the temperate rain forests are the trees that are dispersed along the coastal areas that receive ample amount of rainfall and persistently moist conditions. The regions are covered with dense ocean fog and these forests contain large and tall cone bearing conifer trees among which the most famous are the giant Sequoia trees.

The coniferous trees has needle-shaped leaves that do not allow the snow to accumulate on their surface to prevent the damage from snow and ice crystals, the trees are tall so as to receive maximum sunlight during summer seasons and store water to prevent themselves from dehydration.

The mountains have high ecological importance as they help in the regulation of climate and sea levels. They often provide habitat for endemic species and contribute to the global environment. The mountains also have large vegetations as they have fertile soils to promote the growth of large trees and bushes. Apart from this they also protect valleys from extremes of weather conditions and they serve as a source for many rivers.