Why do we care about the biodiversity–multifunctionality relationship under grassland degradation?
Grasslands cover approximately 40% of Earth’s terrestrial surface and provide vital ecosystem functions, such as forage production, carbon sequestration, and soil conservation. However, nearly half of the world’s grasslands are currently degraded, primarily due to overgrazing and climate change. Having conducted research on the Tibetan Plateau for over two decades, our team has observed widespread degradation in the Tibetan alpine grasslands, with the moderate stage emerging as the most extensive form. These firsthand experiences compelled us to investigate how grassland degradation influences the structure and function of these vulnerable ecosystems.
By integrating insights from the literature with discussions among experts, we recognized that grassland degradation could lead to a decline in ecosystem functioning and exert a profound influence on plant biodiversity. The synchronous shifts in ecosystem functioning and biodiversity brought to mind a fundamental concept in ecology: the biodiversity-ecosystem functioning (BEF) relationship. Numerous small-scale biodiversity manipulation experiments have demonstrated the central role of biodiversity in sustaining ecosystem functioning, and the strength of the BEF relationship can shift under different environmental conditions. Building on this knowledge, and through countless discussions within Professor Yuanhe Yang’s research group at the Institute of Botany, Chinese Academy of Sciences (IBCAS), one question kept resurfacing: “Do the positive biodiversity-functioning relationships still hold in the real world, when ecosystems experience degradation?” Moreover, we extended the BEF relationships from aboveground to belowground biodiversity, which was less explored across large-scale natural ecosystems. Specifically, we wanted to know whether aboveground (plants) and belowground (soil microbes) communities responded similarly to degradation, and whether their relative contributions to ecosystem functioning shifted under environmental stress. The Tibetan Plateau served as an ideal natural laboratory to address these knowledge gaps: vast alpine grasslands spanning steep environmental gradients, interwoven with clear mosaics of degradation. This study was, in a sense, a large-scale “natural experiment” to explore the responses of BEF relationships to environmental change.
Landscape on the Tibetan Plateau (credit: Guanqin Wang)
How did we explore biodiversity and multifunctionality across 2,600 kilometres?
In the summers of 2021 and 2022, the IBCAS Sampling Team (Prof. Yunfeng Peng, Dr. Xiaoxia Gao, Yaping Niu, Shiting Yao, Zan Wu, Qinlu Li, and Xuning Liu) embarked on an ambitious 2,600-kilometre transect survey across the Tibetan Plateau. We set up 44 paired sites, each comprising non-degraded and moderately degraded plots matched in climate and topography yet distinct in vegetation and soil characteristics. Most sites were above 4,000 m, where the air is thin and the ultraviolet radiation is intense. Carrying soil augers, sample bags, and coolers across the alpine grasslands became part of our daily routine. We are deeply grateful to our field drivers, Bin Zhou, Yuanchang Wu, and Jianmin Huo, whose skill and dedication ensured our safety throughout the long and often harsh plateau journey. Because of the large sampling workload, we also received invaluable assistance from local field workers, including Jiyu Xu, Shixiong Zhang, Rou Sai, Cuoni Songqun, Duojie Sende, and Qiwei Zhu, who helped us collect soil samples under challenging conditions. Their efforts made this large-scale survey possible.
Field surveys and sampling work (credit: Qinlu Li)
Those field days were both exhausting and unforgettable. Yet, each day was graced with the unique and breathtaking vistas of the Plateau, a sight that never failed to lift our spirits. Standing on the plateau, surrounded by endless Kobresia meadows under the piercing blue sky, we often paused and wondered: how are the invisible microbial worlds beneath our feet responding to this degradation? Back in Beijing, the exhilaration of fieldwork gave way to months of patient, meticulous lab work, including sorting hundreds of plant specimens, analyzing thousands of soil samples, and processing millions of DNA sequences. Then came the moment of revelation. When we began analyzing the data, one unexpected pattern emerged: ecosystem multifunctionality declined in degraded grasslands, yet both plant richness and soil biodiversity increased. At first, we doubted ourselves. Could this be a sampling artefact? But repeated checks confirmed the trend. That was the turning point. We realized that degradation did not simply mean “loss”, but reorganization. As dominant clonal species lost ground, new ecological niches opened up, allowing forbs and diverse microbial taxa to thrive. Grazing and trampling increased environmental heterogeneity, further stimulating biodiversity.
Laboratory experiments (credit: Xuehui Feng)
To understand how these shifts influenced ecosystem functioning, we used structural equation modelling (SEM) to quantify the relative contributions of plant and soil biota to multifunctionality. The results were striking: in non-degraded grasslands, multifunctionality was primarily driven by plant richness; in degraded grasslands, that influence weakened, while soil microbial diversity became the dominant driver. In other words, degradation transferred the control of multifunctionality from aboveground to belowground life. As plant productivity and biomass inputs declined, ecosystems increasingly depended on microbial decomposers to sustain nutrient cycling and carbon turnover. Co-occurrence network analyses further suggested that degradation enhanced positive interactions among microbes, which implied that cooperation, rather than competition, becomes the key to maintaining ecosystem functioning under degradation. Together, these findings provide the first large-scale empirical evidence that belowground biodiversity plays a pivotal role in sustaining ecosystem multifunctionality under moderate degradation. They highlight a profound ecological shift, from plant-dominated to microbe-dominated control of ecosystem processes, and emphasize that effective grassland restoration must focus not only on vegetation recovery, but also on conserving and rebuilding soil microbial communities.
Effects of grassland degradation on ecosystem functioning, biodiversity, and the biodiversity–ecosystem multifunctionality relationship (Image by Xiaoxia Gao and Yuxuan Bai)
What did we learn and where do we go next?
This study changed our view on degradation. It is not merely a downward path to collapse, but a reassembly process that reshapes who controls ecosystem functioning. It taught us that even under stress, life reorganizes and persists, often in unexpected ways. Moving forward, we are eager to explore whether this shift toward microbial control persists over time and during restoration. We want to uncover how specific microbial traits, such as nutrient acquisition strategies, enzymatic potentials, and interaction networks, translate into ecosystem resilience. By linking microbial traits with ecosystem outcomes, we hope to build a mechanistic understanding that can guide microbe-based restoration practices for degraded grasslands.
For me personally, this journey has been transformative. Entering my research career, I often wondered how large-scale ecological processes connect with microscopic life. This project, spanning the Tibetan Plateau, countless hours in the lab, and collaboration with inspiring mentors, gave me that connection. Publishing this study in Nature Plants is not an end point, but a beginning. It strengthens my resolve to continue exploring how biodiversity, from roots to microbes, safeguards the stability of our planet’s ecosystems.