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The secret world of a single species: Why is competition among single plants so intense?
In nature, competition between plants seems to be an endless war. Obviously, this is not only a competition for resources, but also a struggle for survival and reproduction. When the number of plants of a single plant growing in the same area suddenly increases, how will competition among the plants affect their growth and development? This article will delve into the concept of plant density and the intensity of competition within a single species.
The definition and concept of plant density
Plant density refers to the number of individuals present per unit area. This concept is particularly clear in the case of a single species, where all plants sprout simultaneously and competition for resources is evident.
In some environments, such as after spring, seeds in the seed bank will germinate after winter, which will result in extremely high plant density. As the number of plants increases, there will be fierce competition among these individuals for the limited supply of light, nutrients, and water. Especially when it comes to light, smaller plants will not be able to use resources as efficiently as larger plants. One of the consequences of this competition is "asymmetric competition", which results in some plants being unable to survive. This process is called "self-thinning".
Single species complex
In monostands, the processes involved can be studied in detail. Under these conditions, competition for nitrogen and light will define the growth and development of each plant.
These single-species areas are often studied in agriculture, horticulture and forestry and are crucial to understanding competition between plants. Being part of a single-species ecosystem, the total biomass of these plants will grow with increasing density until a certain saturation point is reached. This phenomenon is often referred to as "constant final yield," which refers to the total plant biomass per unit of land area.
Plant density and self-thinning
In research, when the density reaches 80,000 plants per square meter, 95% of the plants will die. This phenomenon of self-thinning at high densities is avoided in agriculture because such densities do not contribute to increased seed yields.
In addition, in modern agriculture, depending on the final plant size, the normal density range will be between 5 and 300 plants per square meter. Some crops such as corn are about 5-10 plants per square meter, while rice or barley can reach 200-300 plants per square meter. In these high-density environments, the photosynthetic index (LAI) also increases with density, but because the increase in photosynthesis cannot match the increase in LAI, the growth of biomass reaches saturation.
Characteristics of single plant strains
Biomass changes
At higher densities, the average biomass of a single plant will decrease significantly, and each time the density doubles, the size of the plant shrinks by approximately 30-40%.
Dense plants tend to put more biomass into their stems, with less leaf and root growth. This phenomenon will affect the overall physiological performance of the plant, thereby causing phenotypic changes.
Leaf adaptation
High-density plants tend to have fewer leaves, and the leaves are usually smaller and thinner. Such leaves will affect overall photosynthesis and plant health.
Stems and roots
High-density plants generally have smaller stem diameters and fewer side branches. In terms of root distribution, although the total root length of each plant remains constant, the number of roots will decrease, which is quite detrimental to the future growth of the plant.
Physiological factors
In a high-density environment, light will be distributed in a gradient, causing the photosynthetic rate of lower leaves to decrease, and even the photosynthetic capacity of upper leaves may be reduced due to competition.
Seed production
Because densely planted plants are smaller, their seed production is also reduced, making the overall seed harvest worse than in low-density environments.
This means that when the plant's biomass changes, the yield and weight of the seeds will also be affected accordingly, further strengthening the competition between plants.
Conclusion
Through these explorations, we can see that competition between strains of the same plant not only affects the morphology and physiological state of the plants, but also directly determines whether they can survive and reproduce. This fierce competition reflects a process of constant reshaping and adjustment in the ecosystem. Faced with such a fierce competitive environment, how will plants adapt and survive?
