Associate professor Cancan Zhao from the School of Life Sciences, Henan University, shared the paper “Drought shifts soil nematode trophic groups and mediates the heterotrophic respiration”, published in the Journal of Plant Ecology.

Why study soil nematodes?

Soil nematodes are among the most abundant, diverse, and widely distributed invertebrate groups in soil ecosystems, making them an ideal candidate for uncovering the secrets of the soil black box. They occupy multiple trophic levels in the soil micro-food web and can be categorized by feeding habits into bacterivores, fungivores, herbivores, and omnivore-predators. Though difficult to observe with the naked eye, soil nematodes may form intricate food webs. They actively participate in the decomposition of organic matter and drive the cycling of key elements such as carbon, nitrogen, and phosphorus by consuming bacteria, fungi, and others. However, their roles have long been overlooked in mainstream carbon cycle models. Due to their dependence on water films around soil particles for survival, nematodes are highly sensitive to changes in moisture , making them excellent indicators of biological activity under drought stress. Their diverse ecological strategies and dynamic community structures provide an ideal model for understanding how drought influences the carbon cycle function of soil ecosystems. Based on this, our study was conducted by combining field investigations with microcosm experiments, systematically investigating how drought alters the diversity, abundance, and functional role of soil nematodes in the carbon cycle.

What are the findings of this study?

We conducted field surveys along an aridity gradient of grasslands and found that drought significantly reduced the abundance, biomass, carbon footprint, and diversity of soil nematodes. Concurrently, drought lowered the nematode channel ratio and increased the relative abundance of fungivores, indicating a shift in the soil decomposition pathway from a bacterial-dominated to a fungal-dominated energy channel, which in turn suppressed soil heterotrophic respiration. To validate these findings, we subsequently designed a microcosm experiment in the laboratory, establishing multiple moisture gradients to simulate varying degrees of drought. The results were highly consistent with our previous field observations. The abundance, biomass, diversity, and carbon footprint of nematodes all exhibited a declining trend along the aridity gradient. This shift drove a functional restructuring of the nematode community, characterized by a transition in the energy channel from bacterial to fungal dominance. This transition had a dual effect: on one hand, the reduced nematode carbon footprint directly lowered the CO₂ flux from metabolism; on the other hand, the shift of community towards a fungal channel signified the formation of a micro-food web with a slower carbon turnover. These two effects acted synergistically with nematodes serving as a pivotal link, collectively slowing down the process of soil carbon cycling. Therefore, soil nematodes are not only sensitive bioindicators of drought, but their intrinsic link between carbon footprint and soil heterotrophic respiration also underscores the critical importance of incorporating them into Earth System Models for accurately predicting future carbon cycle dynamics.

Some views on ecological research

Ecology is at a historic turning point, with its core mission shifting from describing nature to providing solutions for global crises in the Anthropocene. To achieve this transformation, the key lies in unlocking the “soil black box”, with soil nematodes being one of the most representative “codes” within this black box. However, the difficulty of deciphering this code constitutes the core challenge facing current research. Soil nematodes are minuscule in size and their communities are difficult to artificially construct. Furthermore, their highly similar morphology means that identification methods reliant on expert experience are becoming increasingly unsustainable due to the dwindling number of taxonomists. Even cutting-edge technologies such as high-throughput sequencing are hampered in their species annotation by incomplete reference databases. It is precisely these deep-rooted research difficulties that point the way toward the next critical directions for technological breakthroughs and innovation.

About the author

Cancan Zhao

I am an associate professor in School of Life Sciences, Henan University. My research focuses on the structure and function of soil nematode-microbial food webs. I serve as a young editorial board member for journals including Journal of Plant Ecology, Climate Smart Agriculture, and Biological Diversity. I have led 4 projects of National Natural Science Foundation of China and published over 50 papers such as Geoderma and Canena.

If you are interested in more details about the story, please read our paper “Cancan Zhao, Yuanhu Shao, Huijie Lu, Aimée T Classen, Zuyan Wang, Ying Li, Yanchun Liu, Zhongling Yang, Guoyong Li, Shenglei Fu. Drought shifts soil nematode trophic groups and mediates the heterotrophic respiration” published in Journal of Plant Ecology (https://doi.org/10.1093/jpe/rtae012).