What Is Soil Respiration?

Soil respiration refers to the metabolic activities of plant roots, detritus, fungi and bacteria in the soil. The process of consuming organic matter and producing carbon dioxide. The strict meaning of soil respiration refers to all metabolic processes that produce carbon dioxide in the soil without disturbing it. It includes three biological processes, namely soil microbial respiration, root respiration and soil animal respiration, and a non-biological process, that is, carbon-containing minerals. Chemical oxidation. Soil respiration can be divided into autotrophic respiration and heterotrophic respiration, the former refers to root respiration and rhizosphere microbial respiration, and the latter refers to soil microbial and animal respiration. The substrate consumed by autotrophic respiration is directly derived from the part of the photosynthesis product that is distributed to the ground, while heterotrophic respiration uses organic or inorganic carbon in the soil. Soil respiration is often used to measure the total activity of soil microorganisms and is also used to evaluate soil fertility. Forest soil respiration is an important part of terrestrial ecosystem soil respiration, and its dynamic changes will have a profound impact on global carbon balance. ^[1]

Forest soil respiration is an important part of terrestrial ecosystem soil respiration, and its dynamic changes will have a profound impact on global carbon balance. The increase in soil CO2 release caused by global over-exploitation of forests and other land use changes accounts for half of the total CO2 released by human activities in the past two centuries. factor. Forest soil respiration is also one of the important research objects of the established long-term monitoring CO2 flux website. Is to study the world

Everyone knows that people must breathe when they are alive, and once breathing stops, life will end. Through breathing, the human body absorbs oxygen (O ₂ ) needed for metabolism from the atmosphere and emits carbon dioxide (CO ₂ ). So do you know that the soil also breathes? The breathing process is just as important to it? How is its breathing closely related to our living environment?

Soil

CO2 Soil respiration

Early measurements of soil respiration were based on the release of CO2 from the topsoil, which began more than 80 years ago. With the development of scientific research, soil respiration has been regarded as one of the largest fluxes of the global carbon cycle because of its global CO2 release, and has attracted great attention from the scientific community. Due to its large amount, a small change in the amount of soil respiration may have a considerable effect on changes in the concentration of CO2 in the atmosphere. Because of this, it is important for policymakers in all countries to fully understand some changes in soil respiration fluxes that may accompany rising global atmospheric CO2 concentrations.

Soil respiration

If the warming of the earth is due to the greenhouse effect, global soils are expected to become warmer, especially in high latitudes. Except for some deserts, soil respiration increases with increasing temperature, which can be found from research focused on soil warming. For every 10 ° C increase in temperature, the increase in soil respiration, that is, the Q10 relationship is about 2.0. Studies on surface debris samples and soils in cold climates show that soil respiration has the largest response value, and root respiration has a significant response to temperature, with a Q10 value as high as 4.6. Domestic scholars reviewed the influencing factors of soil respiration and the effect of temperature on a global scale according to the literature, analyzed the relationship between soil respiration and latitude, and annual average temperature of forest vegetation in humid regions around the world. . Studies on the soil carbon storage and CO2 emissions from tropical forests in Jianfengling, Hainan Island show that there is a significant exponential function relationship between soil CO2 emission rates and surface temperature. Soil respiration in temperate forests is also better correlated with soil temperature of 5 cm below ground. Almost all models of global climate change predict that soil carbon loss is one of the causes of global warming, and global warming will promote soil carbon loss, especially sensitive to tropical ecosystems.

CO2 Soil respiration with increasing CO2 concentration and temperature

Under the simultaneous interaction of rising CO2 concentration and global warming, soil respiration is one of the most important scientific issues to be addressed in scientific research. But this is also a poorly understood issue. In the future global environment, is soil a net "source" or "sink" of carbon? Some scientists have boldly believed that nature has completed this experiment for us: tropical rainforests have the largest NPP (as CO2 concentrations rise), It has a warm and humid environment, but the carbon content of tropical soils is much smaller than that of northern soils. Studies on the world's major biomes have shown that there is a direct correlation between soil respiration and NPP (r2 = 0.87). When soil organic carbon content increases, soil respiration rate increases. In tropical areas, plants grow lush and the environment Ideal for decomposers, the soil is found to have the highest respiratory rate. This shows that the increase in CO2 and temperature does not mean an increase in soil carbon content. On the other hand, in the biomes in the world, there is only a weak correlation between soil organic matter banks and NPPs. It is clear that the large accumulation of soil organic matter does not come from large inputs, but more correctly, Soil organic matter accumulates where decomposers are limited by other factors, such as temperature. The CO2 flux in the soil is closely related to the growth of the plants, because the organic residues in the soil are provided by the plants for decomposition. With the warming of the earth, the temperature-limited areas of decomposition will decrease, and at the same time, soil will increasingly become the source of atmospheric CO2.

Soil respiration effect

When soil is disturbed by tillage, their soil organic matter content decreases. This decrease is visible because decomposition conditions such as soil permeability and soil moisture content are improved when the soil is disturbed. When natural vegetation land is converted into agricultural land, the input of fresh plant debris is reduced compared to the past. Tillage also destroys the soil's aggregate structure, making stable, adsorbed organic matter susceptible to decomposition, and the global carbon loss caused by farming is as high as 0.8 × 1015 gC / a. The exponential population growth requires increasing crop yields. In the 21st century, this will require more new land to be converted into farmland, while existing agricultural land will be intensively managed. The implementation of "no-till" agriculture will reduce the loss of soil organic matter. Implementing a "no-till" technical system on previous cultivated land may in fact restore soil organic matter. However, the "no-till" measures widely used in American agriculture will only play a role of carbon sink of 277 × 1012 452 × 1012gC in the following 30 years, which is about 1% of the amount of fossil fuel released. Also in Europe, the improvement of land management and the rotation of land use, the potential carbon sink is only 0.8% of the total CO2 released from the burning of fossil fuels in the world.