Biodiversity supports the foundation for ecosystem functions and services. Extensive research has shown that global changes have significantly impacted above-ground biodiversity and its associated ecosystem functions and services. However, below-ground soil microbial biodiversity has received relatively less attention, leading to significant knowledge gaps. It remains uncertain whether below-ground biodiversity responds to global changes in a similar magnitude and direction as above-ground biodiversity. In addition, different experimental conditions and environmental backgrounds may also affect the response of biodiversity. Integrated conclusions at regional scale obtained based on the results of multiple single-site studies is more conducive to biodiversity conservation and ecosystem management.
The Qinghai-Tibetan Plateau, known as the “Third Pole,” is a hotspot for biodiversity research. Our study focuses on this unique and beautiful region that is experiencing more rapid climate warming and nitrogen deposition than the global average. With approximately 64% of the Tibetan Plateau covered by alpine grasslands, pastoralism has been the dominant ecological and economic land use for thousands of years. These ecological factors have impact on land use in this region. Although this study is a meta-analysis, we also conducted some field experiments in this area.
We conducted an integrated analysis of the sensitive and fragile alpine grasslands on the Qinghai-Tibetan Plateau to assess the impacts of warming, nutrient addition, and grazing on plant and soil microbial biodiversity. The analysis compiled 819 experimental observations from 152 studies, focusing on three main biodiversity indices. This huge amount of data did take us a lot of time to sort and analyse, however support from colleagues and finding answers were valuable motivating factors.
Our study focused on three main questions: (1) Do aboveground (plants) and belowground (soil microbes) biodiversity show mismatched responses to warming, nutrient addition, and grazing treatment? (2) How do plant and soil microbial biodiversity respond to warming, nutrient addition, and grazing treatment? (3) Are experimental conditions, grassland types, and environmental conditions modulate plant and soil microbial biodiversity responses?
The results indicate that plant and soil microbial biodiversity inconsistently responded to warming, nutrient addition and grazing in terms of both magnitude and direction, with plant biodiversity being more sensitive. Specifically, plant species richness and Shannon diversity significantly decreased with warming and nutrient addition, while plant evenness increased with grazing. However, only microbial richness increased with grazing, and microbial evenness showed a slight increase with warming.
Furthermore, biodiversity responses to climate warming and anthropogenic activities are modulated by various factors. Notably, warming’s negative impacts on plant biodiversity are more pronounced under warmer or drier environmental conditions or in long-term experiments. The negative effects of nitrogen addition on biodiversity strengthen with higher nitrogen application rates and longer durations. Appropriate grazing intensity and frequency are beneficial for maintaining plant diversity. Soil microbial diversity is less influenced.
- Conclusion and Implications
Our study reveals that above-ground plant biodiversity and below-ground soil microbial biodiversity exhibit unmatched responses to climate warming and anthropogenic activities, with plant biodiversity being more sensitive. As global change continues to intensify, plant diversity may face greater risks. Additionally, distinguishing biodiversity responses under different experimental and environmental conditions is essential, with greater attention needed for biodiversity conservation in sites with warmer and drier environments, high fertilization intensity, or heavy grazing intensity.
Compared to research on plant biodiversity, there has been limited investigation into soil microbial responses to climate warming, nutrient addition, and grazing, let alone simultaneous examination of plant and soil microbial diversity responses. Our study contributes to filling knowledge gaps; however, we acknowledge that the lack of below-ground research and long-term data may influence our judgement. In future studies, further investigations on below-ground biodiversity and long-term experiments are necessary to enhance our comprehensive understanding of biodiversity responses and its consequences for ecosystem functions and services in the Anthropocene.
This post is by Zijian Shangguan of Peking University, College of Urban and Environmental Sciences, Department of Ecology, 100871 Beijing, CHINA. You can read the full paper here: https://besjournals.onlinelibrary.wiley.com/doi/abs/10.1111/1365-2745.14222