Bin Wei: External nitrogen inputs inhibit plant litter decomposition in an alpine steppe

In this new post, Bin Wei, a Ph.D. student from the Institute of Botany, Chinese Academy of Sciences, China, discusses his recently published paper, “Decreased ultraviolet radiation and decomposer biodiversity inhibit litter decomposition under continuous nitrogen inputs.”

Bin Wei preparing samples for carbon and nitrogen analyses at the Institute of Botany, Chinese Academy of Sciences, China ( credit: Wei Zhou)

About the paper

Anthropogenic nitrogen (N) inputs could alter key processes in terrestrial ecosystems. Of them, litter decomposition is a key process which functions as the main pathway for carbon dioxide (CO2) returning to the atmosphere and a critical step for terrestrial nutrient cycling. The prevailing view states that N-induced changes in litter quality and microbial activities are the main factors mediating litter decomposition under N addition. However, external N inputs usually lead to more closed vegetation canopy, which might reduce the amount of ultraviolet (UV) radiation reaching the litter layer, thus suppressing litter decomposition. External N inputs could also reduce soil biodiversity, which may weaken the facilitative interactions and resource-use complementarity among microbial decomposers, potentially inhibiting plant litter decomposition. Nevertheless, the interactions of UV radiation, soil biodiversity (bacteria, fungi and invertebrates), and traditional drivers (e.g. litter chemistry and microbial activities) in regulating litter decomposition under increasing N inputs remains unclear. To address this knowledge gap, we examined the responses of litter decomposition to external N input by conducting a multilevel N addition experiment in an alpine steppe on the Tibetan Plateau. Based on a two-year in situ litter decomposition experiment and laboratory analysis, we explored the relative importance of N-induced changes in UV radiation, soil biodiversity and conventional drivers in mediating the responses of litter decomposition to continuous N inputs.

About the research

We found that litter decomposition rates among three species and their mixture exhibited consistent decreases in response to N enrichment because of the following two aspects. First, the declined decomposition rates were associated with N-induced reductions in UV radiation. N addition stimulated plant growth and increased community height and leaf area, which promoted canopy UV radiation interception and weakened litter photodegradation. The additional experiment in which we manipulated UV confirmed the significant role of photodegradation in regulating litter decomposition under N enrichment. Second, the N-induced reduction decreased soil bacterial diversity, which could subsequently inhibit litter decomposition by altering the secretion of extracellular enzyme, and weaken facilitative interactions among decomposers. Our findings highlight that N-induced declines in UV radiation and soil bacterial diversity inhibit plant litter decomposition, challenging the traditional view that changes in litter chemistry and microbial activities determine the responses of litter decomposition to external N inputs.

Above: Plant litter decomposition experiment. Below: an additional UV radiation manipulative experiment (right) in an alpine steppe (credit: Dan Kou and Bin Wei)

About the author

During my undergraduate studies as a freshman, I developed an interest in various flowers and plants on the campus in Lanzhou University, China, after attending a plant taxonomy course. Following this, I gained an opportunity to take part in a field experiment on the Tibetan Plateau in 2015. This experience ignited my strong interest in ecology, especially when I knew that more than 30 species could co-exist within a 50 ×50 cm2 quadrat. Both theoretical studies and practical activities drove me to realize that plant ecology research was what really excited me. These experiences equipped and encouraged me to pursue a graduate degree. Currently, I am a Ph.D. student in Prof. Yuanhe Yang’s Lab at the Institute of Botany, Chinese Academy of Sciences, China. Along with my supervisor, and others members in this research group, I am studying how environmental changes (e.g. climate warming and N inputs) affect plant-soil interactions and ecosystem carbon cycling in alpine grasslands on the Tibetan Plateau.

What is the best thing about being an ecologist?

I think that the best thing about being an ecologist is to discover amazing things about a variety of species and across natural ecosystems by conducting fantastic field work. By doing so, we can know better about nature which enables us to learn more from nature.

Landscape of the alpine steppe on the Tibetan Plateau (credit: Guanqin Wang)

Enjoyed the blog? Read the research here.

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