Yankun Zhu: A long-term precipitation manipulation field experiment in a shrub-encroached grassland in Inner Mongolia, China

In this new post, Yankun Zhu—Associate Professor at Sanming University, China—discusses his paper: Increased precipitation attenuates shrub encroachment by facilitating herbaceous growth in a Mongolian grassland—recently shortlisted for the 2022 Haldane Prize for Early Career Researchers.

About the paper

Widespread shrub encroachment is profoundly impacting the structures and functions of global drylands, and precipitation change is assumed to be one of the most critical factors contributing to this phenomenon. However, at present, there is little evidence to show how precipitation changes will affect widespread shrub encroachment. In our paper, we conducted a long-term precipitation manipulation experiment (-30%, ambient, +30%, and +50%) to investigate the effects of precipitation changes on the growth of shrubs and herbaceous plants in a shrub-encroached grassland in Inner Mongolia. The experimental platform was established in July 2015 during my graduate study at Institute of Botany, Chinese Academy of Sciences (IBCAS), China.

The long-term precipitation manipulation field experiment platform in a shrub-encroached grassland in Inner Mongolia, China (credit: Yankun Zhu)

We found that increasing precipitation significantly increased the mean height, coverage, and aboveground biomass of herbaceous species; however, the growth rate of shrub species did not show a significant response to precipitation changes. With increasing precipitation, the relative coverage of shrubs decreased while that of herbs increased. We tried to explain these processes from a perspective of maximum photosynthetic rate and photosynthetic nitrogen-use efficiency. The native dominant herbaceous plant (Leymus chinensis)—with a more sensitive maximum photosynthetic rate to precipitation changes—showed higher photosynthetic nitrogen-use efficiency and water-use efficiency than those of the encroached shrub species (Caragana microphylla) at high soil moisture contents, meaning that the ecophysiological characteristics of L. chinensis might provide a competitive advantage under increased precipitation.

Yankun Zhu measuring soil moisture using a Trime-Pico-IPH soil moisture profile instrument (credit: Yankun Zhu)

Our findings suggest that increasing precipitation may slow down shrub encroachment by facilitating herbaceous growth in Mongolian grasslands. Consequently, this slowing down may affect the forage value and carbon budget of these ecosystems. Our paper contributes greatly to the current understanding of coexistence mechanisms between shrubs and herbs in grasslands, and provides a theoretical basis for predicting the pattern of shrub expansion under future climate change scenarios.

About the research

We have continued our research in this field. Based on this long-term precipitation manipulation field experiment platform, we have evaluated herbaceous plant and soil microbial community dynamics in shrub-encroached grasslands under different precipitation conditions. In addition, we have assessed the impacts of shrub encroachment on soil carbon processes under altered precipitation. Furthermore, we have measured soil extracellular enzyme activity (EEA). Our study highlights that shrub encroachment and altered precipitation can influence soil EEA, which in turn may have consequential effects on nutrients availability and biochemical cycling.

Aijun Xing measuring soil respiration using a Li-Cor 8100A infrared gas analyser (credit: Mengying Zhao)

The next thing I want to investigate is how precipitation change and shrub encroachment jointly drive soil carbon and nitrogen cycling in grasslands. We hope to employ microbial molecular technology and biomarker technology—in conjunction with incubation experiments and model inversion—to elucidate the microbial mechanisms underlying the effects of precipitation change and shrub encroachment on soil carbon and nitrogen cycling in grasslands.

About the author

Yankun Zhu (credit: Yankun Zhu)

I am currently an Associate Professor at Sanming University, China. I received my bachelor degree from Jilin University, China, in 2014, and it was during this time that I joined Prof. Jingyun Fang’s lab at IBCAS. Six years later, in 2020, I received a PhD in Ecology and continued working at IBCAS as a post-doc for 2 years. My research interest is in how global changes affect terrestrial ecosystems. My current research focus is on investigating the mechanisms through which soil microorganisms mediate ecosystem responses to global changes.

I think that the best part about being an ecologist is being able to be close to, explore, and learn from nature. Conversely, I’d actually say that there is no ‘worst thing’ about being an ecologist. However, if forced to choose, in my early career time, meeting snakes when doing field work was definitely the worst thing! One piece of advice I want to offer to other young ecologists is to be fearless!

In my spare time, I enjoy reading, playing with my son, and traveling with my family.

Enjoyed the blogpost? Read the research here!

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