Identifying spatial patterns and assembly rules in communities is a central study topic in ecology. With the unprecedented rate at which biodiversity is decreasing, it is necessary to recognize the spatial patterns and assembly rules in communities in order to understand why biodiversity is being lost and to be able to protect it. However, previous studies have focused more on plant communities in above-ground terrestrial ecosystems, neglecting below-ground ecosystems, especially soil faunal communities. Indeed, soil faunal biodiversity is a crucial component of global biodiversity because soil faunal communities assist in the maintenance of important ecosystem structures and functions. Therefore, one important aim of identifying spatial patterns and assembly rules in soil faunal communities is to clarify mechanisms of maintaining soil faunal biodiversity at multiple scales, so as to promote these processes, which also maintain ecosystem structures and functions. Soil faunal communities usually form complicated spatial patterns at multiple spatial scales. Here, we propose spatial autocorrelation characteristics, and then show how the complicated spatial patterns are demonstrated by patches and gaps of soil faunal communities at multiple scales. These spatial patterns are mainly controlled by processes of biotic interactions, environmental filtering and random dispersal. Consequently, we discuss the impacts of these processes on soil faunal communities. Finally, we suggest that these three processes are essential to evaluate and construct a theoretical framework for soil faunal communities and should continue to be studied in the future. Because interest in spatial patterns and assembly rules of soil faunal communities is relatively new in China, we expect this review will promote the development of related research areas.

Millipedes (Diplopoda) are a highly diverse group of soil invertebrates and play vital roles in terrestrial ecosystems. Millipedes contribute to the cycling of carbon and nutrients through their feeding activities and gut processes that help decompose litter. However, the functions of millipedes have been poorly researched compared to other groups of soil animals such as earthworms. Here, we briefly summarize the ecological functions of millipedes: Millipedes can fragment, consume and transform litter to accelerate its decomposition. Millipedes prefer large amounts of semi-decomposed litter and the efficiency of millipedes in assimilating litter can vary with litter source, temperature and microbial biomass in the litter. Millipedes can regulate the cycling of soil carbon and other key nutrients through feeding and excretion activities. Nitrogen enters to the soil when litter is fragmented by millipedes, but there are different views on how millipedes affect the soil carbon cycle. Millipede faeces decompose more rapidly than the pre-ingested litter. Such a transformation of litters to faeces would accelerate carbon cycling. However, other studies have suggested a relatively low decomposition rate of millipede faeces when compared with un-ingested litter, which could contribute to soil carbon sequestration and stabilization. In addition, the survival of millipedes affects soil phosphorus cycle. They can increase the content of available phosphorus in soil. Millipedes interact with other soil animals such as earthworms and also can regulate the abundances of soil microorganisms. Our review indicates that further studies are required to better understand and document the role of millipedes in ecosystem functioning.

Investigations into soil nematode ecology mainly focus on the relationship between soil nematode communities and their surrounding environment, both biotic and abiotic. This paper reviews a recent string of publications on soil nematode ecology by scholars in China. Research progress has been made on the distribution, composition, ecological function, diversity and drivers of soil nematode communities, as well as on their relationship with global climate change. Developments in new analysis methods for soil nematode ecology are also reviewed here. The developments in soil nematode ecology in domestic and international studies are compared and analyzed, and then the importance of nationwide monitor network construction is put forward. Future research directions of soil nematode ecology in China are also presented. In conclusion, more studies are needed on soil nematode ecology at a small scale within soil micro-food webs and at a large scale under global climate change, and new related technology and methods should continue to be developed.

A total of 579 Megascolecidae species have been reported in China through 2017. Most belong to the genera Amynthas and Metaphire. The family’s rich diversity merits further investigation into its evolutionary history. The arc of research indicates that analysis based on taxonomical and molecular methods reveals the evolutionary history of the family Megascolecidae in China. This paper summarizes updated findings regarding origin, speciation and dispersal of Megascolecidae in China, and discusses the evolution of major familial characteristics (e. g. spermathecal pores, caeca). Several analyses suggest that the ancestors of Megascolecidae in China may have come from the Indo-China Peninsula. Speciation radiation likely occurred after the Cretaceous-Palaeogene mass extinction, and species richness increased rapidly during the Cenozoic period. Ancestral range reconstruction analysis shows that species-groups are polyphyletic and that evolutionary reversal often resulted in sharp evolution of caeca, so we suggest that the current taxonomic system of Megascolecidae, which is based on a few morphological characters, should be reconstructed. We also note that the specific mechanism of evolution in Megascolecidae has not been studied. Hence, future research to reveal the specific evolutionary mechanism of Megascolecidae earthworms requires more systematic sampling of this family, combined with morphological research, phylogeny construction and analysis of geographical patterns, geological history and environmental factors.

Soil fauna have a crucial influence on nutrient cycles and energy flows in ecosystems. In recent years, soil fauna ecology has become a hot topic and frontier in ecology, though it has been studied for more than 60 years at the international level. By contrast, in China, it wasn’t until the late 1970s that significant soil fauna ecology studies were performed in the Changbai Mountains. This article summarizes the three periods of soil fauna ecological studies in the forests of northeastern China and reviews the progress made in research in the last decade. Studies from the last decade can be divided into three categories: distribution patterns and diversity, responses to environmental factors, and ecological function. This article provides a reference for further development of soil fauna ecology in the forests of northeastern and other areas of China. Future investigations of soil fauna ecology in the forest of northeastern China should focus on the interaction between soil fauna and microbiota, the responses of soil fauna to global changes, the interaction between aboveground and underground ecosystems, and the application of molecular biology technology in soil biological research.

A key soil invertebrate, earthworms significantly affect soil quality and the broader ecosystem. In this paper, we review the ecological characteristics of earthworm species Amynthas corticis, A. morrisi, A. robustus, A. aspergillum, Pontoscolex corethrurus and Eisenia fetida in southern China and their effects on soil pH, enzyme activity, metal accumulation and availability, the formation of soil pores and micro-aggregates, and the decomposition of organic waste. In sum: (1) Earthworms in southern China can survive in soil with a wide range of pH (3.8-7.9), and their survival rates are related to soil type, organic matter content, soil contamination level and earthworm species; (2) Enzyme activity in earthworm guts, castings and drilosphere indicate the appetite of different earthworm species, the process of soil nutrient cycling and soil microbial characteristics, respectively; (3) Earthworms are capable of accumulating different metals and altering their availability, but this capability varies depending on earthworm species, element and soil type; (4) Earthworm activity and cast production can change soil structure, increase the amount of soil pores and affect the size, amount and distribution of soil aggregates. Moreover, we highlight the potential application of earthworms toward resolving the acidification of red soil, nutrient imbalance in tea gardens, soil metal contamination, the compaction and destruction of soil during expressway construction, and the utilization of agricultural and urban organic waste. At present, due to insufficient investigations into the physiological characteristics of earthworms and a lack of Amynthas sp. breeding technology, earthworm applications are scarcely conducted at medium and large scales. Hence the promotion of earthworm technology is especially limited in southern China. It will be necessary to explore the potential of earthworms in soil restoration further and to analyze the mechanisms earthworms employ during soil construction and management in order to develop technologies to perform the functions currently occupied by earthworms.

Obstacles to continuous cropping seriously affect crop yield and also lead to a series of microecological imbalance problems, such as the decline of soil biodiversity, the decrease of beneficial microbes, and the increase of pathogens. The imbalanced soil microecology affects plants and can lead to more serious disease and even greater reduction of crop yield. As soil ecosystem engineers, earthworms have important regulating effects on soil microecology. Earthworms can improve the soil environment and strengthen the function of soil biological communities through their activities (e.g. feeding, burrowing and creeping), thus providing a potential way to alleviate microecological obstacles to continuous cropping. This paper reviews the progress made in research on soil microecology, soil function maintenance, and earthworm regulation of soil biological function. Three mechanisms that earthworms employ to alleviate obstacles to continuous cropping through soil microecology regulation were identified: direct regulation of soil microbial communities, regulation of microbial colonies by changing allelochemical composition, and regulation of soil fauna communities. Through earthworm regulation of microbial communities, an imbalanced soil microenvironment in the rhizosphere is corrected, thereby alleviating obstacles to continuous cropping.

Rapid human populations growth in inland arid regions of northwestern China has resulted in rapid oasis expansion, mainly through transforming natural grasslands to arable land, afforested forest and shrub plantations. However, little is known about how different oasis expansion regimes affect soil biodiversity and ecosystem function. In this study, we measured the abundance of nine dominant functional groups of soil biota across multiple trophic levels, including soil macrofauna (oligochaetes, ants, predatory arthropods and herbivorous insects), soil mesofauna decomposers (Oribatida and Collembola) and soil microbial decomposers (bacteria and fungi) in natural grasslands (NG), arable lands (AL), tree (Populus gansuensis) plantations (TP) and shrub (Haloxylon ammodendron) plantations (SP). The study was performed in Zhangye Oasis in the middle reaches of the Heihe River Basin in northwestern China. We measured the contents of soil organic carbon (SOC), total nitrogen (TN) and total phosphorus (TP), as well as the activities of four soil enzymes (catalase, urease, sucrase and phosphatase). The results showed the following important findings. First, the land conversion of NG to SP significantly lowered the abundance of Oribatida and herbivorous insects, while increasing the abundance of Collembola, predatory mites and fungal OTU numbers. However, converting NG to TP significantly increased the abundance of predatory arthropods, herbivorous insects, Collembola, Oribatida, predatory mites and numbers of both bacterial OTUs and fungal OTUs, whereas converting NG to AL significantly increased the abundance of all the above plus oligochaetes. Second, converting NG to either TP or SP significantly enhanced SOC and TN stocks, whereas converting NG to AL significantly enhanced the above plus TP stocks. Finally, converting NG to either SP, TP or AL significantly enhanced the activities of catalase, urease, sucrase and phosphatase, but these four soil enzymes show significantly higher activity in AL and TP sites with irrigation than in SP sites without irrigation. Our results suggest that different oasis expansion regimes significantly and differentially affect the structure and diversity of the desert soil food web, which in turn, cascades down to ecosystem functioning. Understanding the responses of both different soil food web components and of different ecological function variables to changes in land use and management level is essential for developing novel and more effective strategies for oasis ecosystem management in arid regions worldwide. Overall, this study provided key insights into the assessment of the functional stability of the oasis ecosystem.

The effect of elevated atmospheric CO₂ concentrations was investigated on soil fauna communities, controlling the concentrations at 370, 550 and 700 ppm in open top chambers in Sanjiang Plain. Samples were taken and separated by Tullgren or Baermann funnel methods in autumn 2017. Our results showed that: (1) 6,268 individuals belonging to seven classes and 15 orders were collected. Oribatida was the dominant group, accounting for 88.13% of the total individuals. Collembola and Diptera larvae were the other most common groups, accounting for 9% in total, respectively. Different groups varied in their responses to elevated CO₂ concentrations. Oribatida was the dominant group. Collembola and Diptera larvae were the most common groups in AC, EC1 and EC2, but rare groups also differed in AC, EC1 and EC2. (2) The elevated CO₂ concentration significantly increased the density of Oribatida, but reduced the density of Collembola. However, no other soil fauna were significantly affected. (3) The Shannon-Wiener index and the Pielou index of soil fauna exhibited the order of AC > EC1 > EC2, the Simpson index showed the order of EC2 > EC1 > AC, and the Margalef index showed the order of AC > EC2 > EC1. Our results indicate that the soil fauna community composition and diversity might be affected by climate change.