Authors: Zhu Yongguan, Chen Baodong, Fu Wei
Source: "Science and Technology Herald"
Link: http://www.kjdb.org/CN/article/searchArticleResultByKeyword.do#
Summary
Soil ecology takes the soil ecosystem as the research object, and mainly discusses soil biodiversity and its ecological functions, as well as the interaction between soil organisms and the environment. The main research directions and research contents of soil ecology are reviewed, and the current research frontier hotspots in the research fields of large-scale soil microbial geographic distribution pattern, soil biological interaction and soil food web, soil biome and soil health, and new soil pollution are introduced. and prospects for future research directions. Soil ecology research contributes to the objective understanding and scientific utilization of soil biological resources, and provides scientific and technological support for coping with environmental and climate change, restoring degraded ecosystems, and promoting the sustainable use of land resources.
1 The concept, connotation and research significance of soil ecology
The soil sphere is the link between the atmosphere, lithosphere, hydrosphere and biosphere, and is the basis for maintaining the functions and services of terrestrial ecosystems. The biological groups in the soil are complex and diverse, and the number is huge. The interaction of different soil biological groups forms a complex trophic level and food web relationship. At the same time, soil organisms also interact with the soil environment, thus forming the most complex ecosystem in nature - soil ecosystem. Soil ecology is the science of studying soil biodiversity and its ecological functions, as well as the interaction between soil organisms and the environment, taking soil ecosystems as the research object. Soil ecology research has a long history. As early as 1881, Charles Darwin pioneered the study of the influence of earthworm activities on the occurrence, weathering and organic matter formation of soil, and discovered that earthworm activities had an impact on soil fertility. and plant growth. Due to the immeasurable biodiversity and biological quantity contained in the soil, and the complex interactions between soil organisms and between soil organisms and the environment, the development of soil ecology has been very slow in a long historical period. In recent years, with the continuous development of research methods and technologies, soil ecology has ushered in new development opportunities, and the depth and breadth of research has been continuously expanded, and has gradually become a hot spot in the fields of modern soil science, ecology and environmental research. Carrying out soil ecology research will help to comprehensively and objectively understand the occurrence, distribution and maintenance mechanism of soil biodiversity, explore and utilize soil biological resources, and develop soil ecological regulation technology, so as to respond to environmental and climate changes, restore Provide scientific and technological support for degrading ecosystems and promoting sustainable use of land resources.
2 Main research directions and contents of soil ecology
The study of soil ecology has a long history. In the early days, people’s interest in soil ecology research mainly stemmed from agricultural production activities. However, with the recognition of the importance of soil ecosystems, soil ecology research has rapidly extended to terrestrial ecosystems Various fields of research have become one of the hotspots in terrestrial ecosystem research. Today, research on soil ecology mainly focuses on the distribution pattern and driving mechanism of soil biodiversity, the function of soil biodiversity and the plant-soil feedback relationship. It plays an important role in changes and environmental pollution, and is committed to solving major frontier scientific problems facing the world today. Based on this, this paper will introduce the main research directions and contents of soil ecology from four aspects: soil biogeography, soil biodiversity and ecosystem versatility, soil biology and global change, and soil pollution and soil health.
2.1 Soil Biogeography
Soil biogeography research is one of the core contents of soil ecology research, which mainly focuses on the temporal and spatial distribution pattern and maintenance mechanism of soil biodiversity. Soil organisms, including soil bacteria, fungi, viruses, protozoa, arthropods, earthworms, and nematodes, constitute the most diverse and abundant biological clusters on Earth and perform important ecological functions. Carrying out soil biogeography research can help us deeply understand the formation and maintenance mechanism of soil biodiversity, and can predict the response and feedback law of soil biome to environmental and climate change and the evolution direction of related functions. Soil biogeography research mainly answers two key scientific questions: (1) Does the community construction of soil organisms have a geographical distribution pattern? (2) If there is a geographical distribution pattern in the construction of soil biomes, is this spatial variation caused by current environmental factors (such as light, precipitation, temperature and soil environment, etc.) or historical evolutionary factors (geographical distance, diffusion limitation, historical chance events, etc.), or both? There is increasing evidence that the abundance and diversity of soil organisms are not randomly distributed on spatial scales, but have distinct geographic distribution patterns. For example, a global-scale study found that bacterial diversity in the topsoil was highest in temperate regions at mid-latitudes, while fungal diversity decreased with increasing latitude. Further research found that the global distribution of soil bacterial and fungal diversity was highly correlated with soil pH and precipitation, respectively, and the bacterial community and fungal community showed an antagonistic relationship overall, indicating that environmental filtration and niche differentiation jointly determined the global surface layer. Community composition of soil microorganisms. The geographic distribution of soil biomes often differs from the distribution patterns of aboveground plant and animal communities. For example, the diversity distribution of soil earthworms at the global scale is strongly influenced by climatic factors, showing the highest diversity and abundance in the mid-latitudes and in the tropics. The distribution characteristics of the highest biomass in the region. However, a unified understanding of the formation mechanism of the distribution pattern of soil biomes has not yet been formed, and the specific research results are quite different due to different research scales, ecosystem types and soil biota.
In general, compared with the geographical distribution pattern of animals and plants, our understanding of soil biodiversity and its geographical distribution pattern is still relatively shallow, and we cannot answer the above two scientific questions well, and the existing theories and models Most of them are derived from the study of animals and plants, and often cannot overcome the theoretical extrapolation of "adaptation to the soil and water", it is difficult to integrate the coupling process of the above-ground and underground parts of the ecosystem, and it is impossible to establish the connection between the distribution of soil biological species and their functional attributes, which makes us The understanding of soil biogeographical distribution is still lacking systematic and holistic.
2.2 Soil biodiversity and ecosystem multifunctionality
More and more studies have confirmed that soil biodiversity is closely related to multiple ecosystem functions and services such as primary production, plant diversity, nutrient cycling, litter decomposition, climate regulation, and pollutant absorption. The relationship between diversity and ecosystem multifunctionality is becoming a hotspot in soil ecology research. Conceptually, ecosystem versatility can be defined as the ability of an ecosystem to simultaneously provide multiple ecosystem functions and services. In the past 20 years, researchers have carried out a lot of research on how the loss of biodiversity affects the multi-functionality of the ecosystem, but the role of soil biodiversity has been largely ignored from the perspective of animal and plant diversity. In recent years, with the deepening of soil ecology research, a large number of indoor simulation experiments and ecological surveys have shown that soil biodiversity is crucial to soil versatility and crop productivity. For example, by regulating soil biomes, the researchers found that soil biodiversity, abundance and interaction strength showed a significant positive correlation with ecosystem multifunctionality, suggesting that subsurface soil biomes are also responsible for maintaining ecosystem multifunctionality. key. At the same time, ecological survey studies at the global scale have also found that soil microbial diversity drives the versatility of terrestrial ecosystems.
Although there is a significant positive correlation between biodiversity and ecosystem multi-functionality at the macro level, this does not mean that different species have the same functional properties. Rare species in a microbial community can exhibit different functional and environmental response characteristics from the dominant species, and can often play the role of "four liang and one thousand jin", thereby providing extensive functional redundancy for the community. For example, by cultivating natural bacterial communities, researchers found that there are essential differences in the ecological functions of dominant and rare species in the community. Abundant species mainly affect broader measures of community function such as respiration, metabolism and cell proliferation, while rare species affect The functional measures of , are relatively narrow (eg, degradation of specific substrates). In addition, rare species may be key groups in soil biomes, such soil organisms often show high connectivity in the community, have a strong influence on the structure and function of the community, and are important for maintaining soil biofunctionality. key. For example, the researchers found in field experiments that rare microbial taxa in soil (such as cyanobacteria and mycorrhizal fungi) rather than dominant taxa (such as proteobacteria and ascomycetes) were the main drivers of soil versatility.
2.3 Soil biology and global change
Changes in biotic and abiotic environments caused by global change are profoundly affecting the structure and function of ecosystems. The response of soil ecosystem to global change has always been the focus of global change ecology research. On the one hand, soil, as an important carrier of ecosystem structure and function, plays an important role in the process of ecosystem response and adaptation to global changes; The biogeochemical cycles of elements such as nitrogen and phosphorus are deeply involved in the decomposition and retention of soil organic carbon, the production and emission of greenhouse gases (such as CO 2 , CH 4 , N 2 O, etc.), and the growth of aboveground plants. global change process. For example, due to the increase in soil microbial activity caused by climate warming, soil heterotrophic respiration on a global scale has been significantly enhanced in recent decades, resulting in a significant increase in soil CO2 output to the atmosphere , which may exacerbate global change.
Soil organisms are very sensitive to environmental changes, and a large number of studies have shown that global change factors, such as the increase of atmospheric CO2 concentration , nitrogen deposition, climate warming, alien species invasion, extreme climate and land use changes have become soil biomes. Major drivers of change and loss of diversity. For example, at the regional scale, the researchers found that soil arthropod diversity and biomass declines are associated with landscape-level land use patterns; at the global scale, the proportion of pathogenic bacteria in soil fungal communities may be significantly increased by climate warming increase, potentially affecting global agricultural production. There may also be large differences in the responses of different soil taxa to environmental changes. For example, soil protozoa communities were more responsive to cropland nitrogen application than soil bacterial and fungal communities. In addition, considering that under natural conditions, soil biomes are bound to be affected by multiple global change factors at the same time, Rillig et al. set up multiple global change factors in their experiments and found that the combined effect of multiple factors will aggravate soil ecological processes and microbial communities. response, indicating that considering only a single global change factor may underestimate the strength of the soil ecosystem response, thus affecting the accurate assessment of the ecological effects of global change.
2.4 Soil pollution and soil health
Soil health refers to the ability of soil to maintain the survival and health of plants, animals and humans, and its essence is the sustainability of soil providing ecosystem functions and services. With the rapid development of society and economy, a large number of pollutants produced by human production and life, such as heavy metals, organic pollutants and antibiotics, have been discharged into the soil in large quantities, exceeding the absorption capacity of the soil itself and affecting the soil ecosystem. structure and function, a serious threat to soil health and safety. Soil biomes are the key to maintaining soil health and vitality. On the one hand, soil pollution can change the composition and structure of soil biomes and thus have a negative impact on soil ecosystems; on the other hand, soil biomes can also metabolize and adapt through their own growth. Mechanisms are involved in the absorption, migration and transformation of soil pollutants, so as to remediate contaminated soil to a certain extent and maintain the stability of soil ecosystem functions and services. For example, soil heavy metal pollution can significantly reduce the diversity of soil microorganisms, leading to the loss of related functions of soil biomes; while some soil functional microorganisms, such as mycorrhizal fungi, can participate in the migration and transformation of heavy metals in the soil-plant system, reducing the toxicity of heavy metals in plants. , which can play an active role in the remediation of heavy metal-contaminated soils.
Although we have carried out a lot of research on the law of some specific soil biological groups, such as bacterial and fungal communities in response to soil pollution, but little attention has been paid to the interaction between different soil biological groups, ignoring the integrity of the soil ecosystem Therefore, it is difficult to explore the ecological effects of soil pollution at the community and ecosystem levels. For example, soil organisms form a soil food web through the relationship between feeding and being eaten. Can the response of a certain type of soil organisms to pollutants affect other soil organism groups through the cascading effect of the food web? What are the similarities and differences in the effects of responses at different trophic levels in the food web on the overall connectivity and stability of the food web? These questions remain to be further answered.
3 Frontiers and hotspots of soil ecology research
3.1 Research on the geographic distribution pattern of large-scale soil microorganisms
In recent years, large-scale research on the geographic distribution pattern of soil microbial diversity has attracted much attention, and biogeographical research on soil bacteria and fungi, nematodes, earthworms and protozoa on a global scale has been published in high-level journals one after another. These pioneering studies have revealed the global distribution pattern of soil biodiversity at the macro level, and explored the mechanisms of soil biome construction and its underlying functional characteristics. For example, global-scale soil biogeography studies have found that species richness of bacteria and earthworms tend to peak at mid-latitudes, while nematodes are most abundant at high latitudes, exhibiting patterns that differ from above-ground flora and fauna. Further research on community construction mechanisms found that the construction of soil microbial (bacteria and fungi) communities at the global scale was mainly affected by environmental factors such as soil pH and precipitation, while soil animals (earthworms/protists) were mainly affected by climate such as precipitation. influence of elements. In the future, this research direction needs to consider more different soil biological groups and different functional attributes of soil organisms, in order to connect biodiversity with ecological functions, and then better predict soil biodiversity and its functions under global change. evolution law.
3.2 Soil biological interaction and soil food web
Soil organisms do not exist in isolation, but form a complex interaction network through symbiosis, competition and predation among species, and participate in soil ecological processes together. For example, through targeted regulation of microbial communities, the researchers found a positive correlation between the strength of interactions between microbes and ecosystem versatility. Soil organisms can also affect the structure and function of soil biotic communities through the soil food web established by the predation relationship. The latest study found that the predation of bacteria and fungi by soil protozoa at low temperature can increase the decomposition of soil organic matter and the release of CO2 ; similar, studies based on the natural restoration process of abandoned cultivated land found that the complexity of the soil food web increased This was accompanied by an increase in soil nutrient cycling and carbon uptake efficiency. In addition, soil protozoa can also widely participate in the construction of plant rhizosphere microbial communities through their predation on plant rhizosphere bacteria and fungi, thereby affecting the growth and health of aboveground plants. For example, Jiang et al. found that soil protozoa and nematodes can affect the community composition and biomass of soil arbuscular mycorrhizal fungi through food web predation, thereby affecting the productivity of aboveground plants. These studies strongly imply the critical role of soil food webs in maintaining the structure, processes, and functions of soil ecosystems, and research in this area is in the ascendant.
3.3 Soil biome and soil health
With the popularization of high-throughput sequencing technology and the rapid development of bioinformatics, soil ecology research has ushered in a blowout development. A large number of studies have shown that soil biomes, including soil microorganisms and soil animals, are the key to maintaining soil health. . For example, Wei et al. found that the composition and function of the initial soil microbial community determines whether plants can resist soil-borne diseases, and the plant disease resistance mediated by this microbial community can be obtained through soil transplantation. In recent years, the research on soil biota and soil health has been paid more and more attention, and has become the frontier and hotspot of soil ecology research. This is because: on the one hand, soil biological diversity and community composition are very sensitive to changes in soil environment and can better indicate soil health; on the other hand, more and more studies have shown that soil biological diversity and soil There was a significant positive correlation between the multifunctionality of the ecosystems. More importantly, soil organisms can also be used by me to serve the needs of human society. For example, harnessing the rhizosphere microbiome could enhance crop resilience and restore degraded ecosystems. The establishment of the relationship between soil biological community and soil function provides a basis for the development of soil health regulation theory and technology system with soil organisms as the core.
3.4 New soil pollutants
In recent years, due to the irrational use and disposal of antibiotics, a large number of antibiotics have entered the soil ecosystem, which has caused continuous selection pressure on soil microbial communities, resulting in a large number of antibiotic resistance genes amplifying and widely spreading in soil, causing serious damage to soil health. a serious threat. At present, soil resistance genes have been widely regarded as a new soil pollutant, and its migration and spread in soil ecosystems have received extensive attention from researchers. By modeling the food chain in farmyard manure-applied soils, the researchers confirmed that resistance genes can be transmitted through predatory relationships in the food chain, and that soil bacterial communities and mobile genetic elements are the main drivers of resistance gene transfer. In the process of resistance genes passing along the food chain, different biological groups have different effects on soil resistance genes. Under the condition of long-term fertilization, the level of resistance genes in the gut of soil nematodes was significantly higher than that of earthworms, and due to the reduction of resistance genes in the intestinal flora of earthworms, the transfer efficiency of resistance genes gradually increased with the increase of fertilization years. reduce. In addition, other soil contamination may also affect the spread of resistance genes in the soil. For example, Hu et al. found that long-term nickel exposure significantly increased resistance gene diversity, abundance, and horizontal migration potential in farmland soils. In summary, in-depth research on the process and mechanism of antibiotic resistance gene transmission in soil will provide an important scientific basis for biological pollution risk assessment and management.
Soil-borne pathogenic microorganisms, such as Rhizoctonia solani , Fusarium oxysporum , Alternaria alternata and Ralstonia solanacearum , are also considered to be a new soil contaminant It can cause a wide range of crop diseases and seriously endanger food security and soil health, so it has received extensive attention from researchers. Recent studies have shown that microbial communities in healthy soils can control the spread of soil-borne diseases and enhance soil immunity through microbial competition and interaction, secretion of resistant substances, predation in food webs, and occupation of rhizosphere niches. The researchers found that certain bacteriophages can "specially hunt" the soil bacterial wilt bacteria, greatly reducing the incidence of tomato bacterial wilt disease, showing a strong biocontrol effect. Specific microbial communities in the soil not only have pathogen resistance themselves, but also enhance the pathogen resistance of plants by interacting with plants. For example, Hou et al. found that under normal and adverse conditions, the interaction between root flora and plants Both significantly reduced the incidence of plant leaves and enhanced the systemic resistance of plants. These studies have shown that the soil microbial community has a strong biocontrol potential. Therefore, the exploration and utilization of soil biocontrol microbial resources will help to build a soil-borne disease biocontrol system and enhance soil immunity, thereby inhibiting the outbreak of soil-borne diseases.
4 Outlook
In the past 20 years, thanks to the advancement of genomics technology, soil ecology research has developed rapidly, largely updating our understanding of soil ecosystems. However, due to the complexity of the soil ecosystem, the current understanding of the mechanism of soil ecological processes is still relatively shallow, and the existing theories are mostly borrowed from macroecological research. Therefore, it is urgent to develop its own theoretical system of soil ecology and improve research. level and depth. First, in order to deconstruct the complexity of the soil microbiome, soil ecology research should embrace more new technologies and methods, and develop from metagenomics to meta-phenomics to explore the microbiome in situ ecological function, spanning current genome- and metagenomic-based functional prediction studies. Secondly, considering the coupling of above-ground and underground ecological processes and their environment and scale dependencies, it is imperative for field positioning experiments to cooperate with large-scale monitoring and networking research. A scale for soil ecology research. Finally, in the context of global change, soil ecology, like other ecological environment and resource disciplines, faces a series of major challenges such as coping with global change and environmental pollution, and maintaining sustainable resource utilization. How to use soil ecology theory and research Achievements The development of soil ecological regulation technology, the exploration and utilization of soil biological resources, the restoration of degraded soil, the maintenance of soil health, and the support of ecological civilization construction and national strategies for sustainable development have become important tasks in current soil ecology research.
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