Dr. Dianye Zhang, a postdoc from Prof. Yuanhe Yang’s Lab in the Institute of Botany, Chinese Academy of Sciences, discusses his recent paper “Changes in above-/below-ground biodiversity and plant functional composition mediate soil respiration response to nitrogen input” published in Functional Ecology.

What is the background behind your paper?

Intensified human activities accelerate the deposition of reactive nitrogen (N) into terrestrial ecosystems. Reactive N enrichment, the second largest C flux in terrestrial ecosystems, can directly affect soil respiration components (autotrophic respiration generated by plant roots, and heterotrophic respiration produced by soil microbes and fauna) by altering soil N availability, soil temperature as well as plant and microbial physiology. Besides, external N input-induced changes in biodiversity (plant species richness, plant functional diversity and soil biodiversity) and plant functional composition can also indirectly mediate the trajectories of autotrophic and heterotrophic respiration under N enrichment. Although the indirect effects of N enrichment could be even stronger than its direct effects, limited studies have established the associations of soil respiration components with above-/below-ground biodiversity and plant community composition in the case of N input. In this study, we addressed this issue by conducting a multilevel N-manipulation experiment in a Tibetan alpine steppe. Based on soil respiration observations as well as biotic and abiotic measurements under this N addition experiment, we quantified the relative and interactive effects of above/belowground biodiversity, plant community composition and other explanatory variables (e.g., soil temperature, pH, gross primary productivity, root biomass and extracellular enzyme activity) on autotrophic and heterotrophic respiration.

What are the key messages of your article?

Our results illustrated that above-/below-ground biodiversity loss and changes in plant community composition exhibited substantial effects on the response of autotrophic and heterotrophic respiration to N input in this alpine steppe. The decreased plant functional diversity and the increased sedge relative biomass promoted autotrophic respiration. However, the inhibition of declined above/belowground productivity exceeded the promotion of altered plant biodiversity and community composition under high N addition treatments, resulting in a hump-shaped response of autotrophic respiration along the experimental N gradient. Conversely, the loss of soil biodiversity together with the decreased plant functional diversity consistently inhibited heterotrophic respiration along the experimental N gradient. Our results highlight that the indirect regulation of N input on ecosystem function through changes in plant community composition and above/belowground biodiversity loss should be considered for better understanding the responses of terrestrial ecosystems to atmospheric N deposition.

How is your paper new or different from other work in this area?

The most significant feature of our work is the observation of the joint roles of plant and soil biodiversity loss in determining the response of heterotrophic respiration to N enrichment. This finding expands the biodiversity effects on heterotrophic respiration from aboveground to belowground.

What would you like to do next?

We intend to focus on the linkage between biodiversity and soil carbon cycling on the Tibetan Plateau. Particularly, we want to explore the effects of aboveground animal biodiversity on key soil carbon cycling processes. There are many kinds of animals on the Tibetan Plateau, including domestic yak, horse and sheep as well as wild caterpillar, pika, marmot etc. These animals can affect soil carbon cycling by altering microenvironment as well as plant and microbial community structure. Thus, the quantification of the effects of aboveground plant and animal as well as soil biota biodiversity on soil carbon cycling could be conducive to reveal the mechanisms underlying the biodiversity-carbon cycling association from the aspect of multitrophic interactions and food webs.

How did you get involved in ecology?

I like flowers and grasses since I was a little boy. In my first year of graduate school, I got a chance to go to the Tibetan Plateau. The vast grassland and colorful flowers fascinated me. After that field trip, I decided to learn more about them. This curiosity incents me to open the door of ecology.

What is the best thing about being an ecologist?

The most exciting thing about being an ecologist is that I can enjoy various natural scenery. I have conducted my research in the grassland of the Tibetan Plateau, the hilly land of the Loess Plateau and the Ala Shan Desert. These experiences really rejoice me.

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