What is the origin of the tundra ecosystem?

According to plant fossil records, the high latitudes of the northern hemisphere were still warm-loving forests before the Tertiary period, but at the end of the Tertiary period, due to the cooling and drying of the climate, this kind of forest was gradually replaced by subarctic coniferous forests. At the beginning of the Quaternary period, the climate became even colder, which created the conditions for the formation of the tundra. The tundra first appeared in northern Eastern Siberia, because during the Ice Age, continental Europe, Western Siberia and most of North America were covered by glaciers, only in northern Eastern Siberia, where glaciers had a lesser impact, but there was an ancient tundra core (what Tormachev called "primordial Arctic vegetation"), which gradually spread from the mountains to the plains.

According to the characteristics of the fauna, the zoologist Kuznetsov analyzed that Eastern Siberia is the birthplace of the Arctic fauna.

At the beginning of the Quaternary period, the ancient tundra divided into two branches, east and west, stretched around the North Pole, forming a belt-like distribution, and with the alternation of glacial and interglacial periods, the Arctic continental ice sheet periodically expanded and contracted southward. At the same time, tundra organisms continue to migrate southward, and in the process, some species die in large numbers until they disappear; Some species have survived and joined forces with those that migrated down from the high mountains. When the glaciers retreated, some of these species moved north; Others retreated to the mountains, where they were preserved and became part of the mountain tundra.

For example, animals such as black-edged bean butterflies, snow rabbits and ptarmigans; Among the plants, it is pearl tooth knotweed, dwarf birch, multi-petaled wood, kidney leaf mountain knotweed, etc. It should also be pointed out here that the formation age of the northern tundra zone is shorter than that of the entire tundra zone, and because the northern part of the ice age was still covered by glaciers, it was only gradually formed in the late glacial period, after the glaciers retreated. Therefore, it can be said that the tundra ecosystem is the youngest of all terrestrial ecosystems.

Answer D The permafrost tundra ecosystem has few species of animals and plants, simple community trophic structure, weak resistance stability, and strong resilience stability, so A is wrong. Item B has a lot of high temperature and rainfall, because there is no environment with high temperature and high rain in the tundra ecosystem, so it is wrong. The resistance stability of permafrost tundra ecosystem in item C is weaker than that of tropical rainforest ecosystem, so item C is incorrect.

Item dWhen investigating a certain population density in an ecosystem, the population density of animals can be investigated by the marker recapture method, and the population density of plants can be investigated by the sample method, so item D is correct. This question is more difficult.

The tundra, also known as tundra, refers to the area near the Arctic Lixu Bench and above the tree line of the temperate mountains, where low vegetation grows and there is a permafrost underground.

The tundra has a cold climate and has only a very short plant growth period each year, with only a few low, hardy woody and perennial herbaceous plants, as well as mosses and lichens.

An ecosystem in the tundra is a tundra ecosystem!

The tundra ecology is mainly distributed in the Arctic plain, called flat tundra or polar tundra; The tundra is found on the top of a mountain. Mountain tundra is a variant of flat tundra in mountainous areas. The polar tundra is located between the taiga and the Arctic desert, along the northern part of Eurasia and North America, and forms a vast tundra belt around the Arctic Ocean.

The western part of Eurasia is affected by the Mexican Warm Current, so the tundra zone is very narrow. As the continentality increases from west to east, the extent of the tundra extends southward, especially in Western Siberia and Central Siberia. In northeastern Asia and northwestern North America, the tundra zone is narrow, but montane tundra is widely developed in mountainous areas.

The northeastern part of North America is relatively flat and affected by cold snaps, where the tundra extends southward, reaching as far south as about 52°N. In mountainous areas, tundra often occurs in the upper part of the vertical zone, the top of which transitions to the alpine ice and snow zone. Due to the low latitude of China, there is no flat tundra, but there are some mountain tundra near the top of the Changbai Mountains and the Altai Mountains.

According to the statistics of Whitaker (1970) et al., the world's tundra covers an area of about 8 million square kilometers, accounting for a total land area.

(1) Richness refers to the number of species in a community

2) Compared with tropical forest ecosystems, the lower temperature in tundra ecosystems is not conducive to the decomposition of soil organic matter by microorganisms (decomposers) in the soil, and is conducive to the accumulation of soil organic matter

3) In an ecosystem, the more trophic levels, the more energy is consumed in the process of energy flow, so the food chain in the ecosystem is generally no more than 4 5, and the food chain of the ecosystem will not be very long

Therefore, the answer is: (1) the number of species in the community.

2) The low temperature in the tundra ecosystem is not conducive to the decomposition of soil organic matter by microorganisms (decomposers) in the soil.

3) In an ecosystem, the more trophic levels, the more energy is consumed in the process of energy flow, so the food chain in the ecosystem generally does not exceed 4 5, which is not very long.

Commentary: The tundra ecosystem is also known as the tundra ecosystem. It is a complex of biomes of polar plains and alpine tundra and their living environment.

According to the different distribution areas, it is divided into polar (tundra) ecosystems and alpine (tundra) ecosystems. The main characteristics are low temperature, poor biological species, short growth period, and low precipitation. The global tundra covers an area of about 8 million square kilometers, accounting for about about the total land area.

The ecology of the tundra is very harsh. The climate is characterized by cold, with long and severe winters and short, cool summers. The annual precipitation is not much, but the number of precipitations is large, and the evaporation of water is weak, so the air humidity is high.

Tundra soils have permafrost at a certain depth and are widely distributed. Tundra plants have a range of physiological characteristics that are resistant to cold and drought, many plants are protected from damage to their vegetative organs in cold wipes, and some plants grow under snow. Tundra plants are usually perennials.

There are few species of tundra animals, mainly large herbivores, which are physiologically cold-resistant.

The tundra is a plant community dominated by hardy arctic and arctic-alpine mosses, lichens, small shrubs, and perennial herbaceous plants. The tundra is a zone biota of the boreal zone, formerly translated as "tundra", because the typical tundra vegetation is dominated by mosses and lichens. In fact, this type of tundra is only a part of the tundra vegetation.

The general characteristic of the whole tundra is that there is a permafrost layer underground, so it is more appropriate to call it "tundra".