What are Anthropogenic Biomes?

Biological community ^[1] : A collection of various biological populations gathered in the same area or environment at the same time. Although it is composed of various biological organisms such as plants, animals, and microorganisms, it is still a combination with a certain composition and relatively uniform appearance. Different populations in a community are not scattered randomly, but live together in an orderly and coordinated manner. The basic characteristics of biological communities include species diversity in the community, growth forms of the community (such as forests, thickets, grasslands, swamps, etc.) and structure (spatial structure, temporal organization and species structure), and dominant species (which Species that are large, numerous, or highly active that determine the characteristics of the community), relative abundance (relative proportions of different species in the community), nutritional structure, etc.

Biomes

1. Has certain dynamic characteristics

2. Has certain boundary characteristics

3 Have a certain distribution range

4 Have a certain structure

5. Have a certain kind of composition

6. Have a certain community environment

7. Interaction between different species

8. Species are not equally important in community

include

Available from productivity,

Biological communities are always in constant change. There are day and night changes, seasonal changes, and inter-annual fluctuations. However, such changes and fluctuations do not cause the essential changes of the community. Some of its basic characteristics are still Keep it up. But sometimes another phenomenon is also common in nature: a community develops into a completely different community, which is called community succession or ecological succession. For example, in abandoned farmland near Beijing, the first year of growth is mainly annual weeds, and after a series of changes, finally deciduous broad-leaved forests are formed. Each stage in the succession process is called a series of communities. Succession finally reached a relatively stable community, called the climax community.

Biome succession

In most cases, the dominant component in the succession of biomes is plants, and animals and microorganisms are only changed with plant changes. The basic reason for the evolution of plants is that the plants that first settled in a place, through the accumulation and decomposition of their debris, added organic matter to the soil, changed the properties of the soil (including fertility), and changed the surroundings by shading. Some of the microclimates also add certain organic compounds to the soil through the secretion of roots, so that changes in the environment within the community create conditions for the invasion of other species. When the change accumulates to a certain degree, it is not conducive to the original plant's own survival and reproduction, so succession occurs. Of course, changes in external factors can also induce succession.

Biome succession

Some successions can be completed in a relatively short period of time. For example, a series of rapidly changing communities appeared on the ground after a forest fire, and finally returned to the stable original type. But sometimes succession progresses very slowly, even hundreds or thousands of years to complete. According to research by Soviet scholars, birches, aspens, and alders appeared first on barren arable land in the spruce forest region of Taiga, because the seeds of these tree species are easily carried by the wind, and they fall on weakly grassy soil Began to germinate. These are the so-called pioneer species. Among them, the strongest settled on the barren or reclaimed land, where it was consolidated and gradually changed the environment. After 30 to 50 years, the birch canopy was densely formed to form new conditions. The new conditions are suitable for the growth of spruce, which is not good for the birch itself, so a mixed forest is gradually formed. However, this mixed forest has not existed for a long time because the birch trees of Xiguang can not stand the shade and cannot be renewed under the spruce canopy. About 80 to 120 years after the emergence of the first birch seedlings, a stable spruce forest was formed.

Biome succession types

There are two types of succession: successions that started in places that were originally inanimate (such as sand dunes, lava lava condensed rocks, glacial receding ground, hillside collapse and landslides, etc.) are called native successions. In the case of native succession, the rate of community change is generally not large. A series of successively replaced communities maintain a large time interval with each other, and the biological community sometimes takes hundreds of years or more to reach the climax. If the community develops in a place where there have been organisms before, this succession is called a secondary succession. Such sites often hold mature soils and abundant biological propagules, so climax communities are formed much faster by secondary succession than by primary succession. Under modern conditions, secondary succession can be observed everywhere, and they often occur after fires, floods, grassland reclamation, deforestation, swamp dewatering, etc.

Biological community succession

Succession of different biological communities has its own characteristics, but there are many development trends that are common to most communities. For example, in the succession process, not only does biomass accumulation generally increase, but communities are heightened and stratified. It is becoming more complicated, productivity is increasing, and the impact of communities on the environment is increasing. In addition, soil development, cyclic nutrient storage, species diversity, longevity of dominant organisms, and the relative stability of communities tend to increase. But in some successions, there are exceptions to these trends. For example, productivity and species diversity decrease in the late stages of succession, so the climax stage of succession is not characterized by maximum productivity, but by maximum biomass and low net productivity.

Cold spring biome

There are three doctrines for the climax: the first is the single climax theory, which was mainly developed by FE Clements (1916, 1936). This theory emphasizes that successions from different habitats in a certain landscape tend to converge to similar climaxes. For example, in a forest area, succession that occurs on stony hillsides or valley bottoms will evolve into forests, although these forests may be composed of different tree species. Because of this relative convergence, in principle, all succession communities in a region may converge to a single (broad) climax community; this climax community is entirely determined by the climate, so it is also called the climax. If one of the communities in the area is blocked for some reason and cannot develop into a climatic climax and stays in a non-climatic climax for a long time, this stable community is called a quasi-climax.

The second theory was proposed by AG Tansley in 1939. He was one of the early founders of the multi-climax doctrine. The multiclimax theory holds that there may be more than one climax community in a region. Due to the influence of soil moisture, soil nutrients, slope orientation, animal activities, etc., many stable communities or climax communities can be distinguished in an area. This theory is accepted by many ecologists. Among the many climax communities in an area, one of them can be considered the most typical, or the most representative for the general climate of the area. This community is the climax; other stable communities include the climax. (Different from climatic climax due to terrain location) and soil climax (different due to soil characteristics).

The third doctrine is the climax-mode hypothesis, which is a variant of the multiclimax concept proposed by RH Whitaker in 1970. He believes that there are gradients of multiple environmental factors (temperature, moisture, soil fertility, soil salinity, biological factors, wind, etc.) in a region, and together form an environmental gradient model, and various environments gradually change. Biomes are also adapted to this environmental gradient pattern and are therefore not distinctly separated into discrete climax types. The climax type gradually transitions along the environmental gradient. The community type that constitutes the largest part of the climax model and is the most widely distributed in the landscape is the dominant climax, that is, the climatic climax.

The concept of climax cannot be understood mechanically, because succession reaching the climax stage does not mean the termination of community development. In fact, the climax community is still developing, but the speed of development is very slow, and it is not easy to see from the appearance.

The above classic concept of community succession by FE Clements is strictly deterministic, and he arranges the communities in the succession into a strict sequence. However, observations from various places prove that the succession of the community is very random. FE Clements' concept is being challenged.