In our new post, Junwei Luan from International Centre for Bamboo and Rattan (China) presents his last work ‘’Litter decomposition affected by bamboo expansion is modulated by litter-mixing and microbial composition’, discusses about the effects of commercial plantations in ecosystems and shares his research career experiences.
About the paper
Our paper is about how a native woody grass (Moso bamboo, Phyllostachys edulis) expansion alters forest soil nutrients cycling via dead leaf litter decomposition. We found a trade-off mechanism between introduced litter and soil microbes which drives the decomposition process.
Due to its commercial value, Moso bamboo (Phyllostachys edulis), a native species in China, was widely planted and accounts for more than 70% of the nation’s bamboo forest area (i.e. 6.41 million hectare – data from the ninth national inventory of forest resources of China). But lack of management and its fast clonal growth led to the spreading of Moso bamboo to natural forests, causing unexpected disturbance and competition with native and protected species, so much so that nature reserves sometimes consider it as weed and have to control it as such.
Species that expand across their native range and outcompete other natives in response to human-mediated disturbances, are named “native invaders”. Although they can cause similarly harmful ecological and economic impacts as exotic invaders, we have limited knowledge of how native invaders alter ecosystem processes, and if the mechanisms of expansion of exotic invasive species apply to native invaders as well.
The decomposition of dead leaf litter in forests is crucial for soil organic carbon sequestration and nutrient cycling, which could be affected by changes in plant community composition caused by plant invasion or expansion. Shifts in plant community composition not only change leaf litter composition, but also alter soil microbial community structure (efficiency of decomposers varies with litter of different species). Understanding of how these changes affect decomposition is important to understand how bamboo alters ecosystem function from the ground up, thus providing logistic management practices.
The key messages of my article are that bamboo expansion does alter soil nutrient cycling (through both faster N loss and litter-mixing effect), We also found a trade-off between introduced litter and nutrient use efficiency (measured or defined as “the unit of nitrogen needed for decompose per unit of carbon”) of local microbial community to drive decomposition (suggesting a negative feedback). This means that elevated nutrient levels caused by bamboo will soon reach an equilibrium state and may not be able to facilitate further expansion of bamboo.
What we still don’t know is how these interactions between litter and microbes work in detail (e.g. which part or specific species of microbiome are responsible for the changes seen).The use of techniques such as stable isotope as functional tracers of nutrient cycling and DNA-based stable isotope probing might be helpful to detangle the underlying mechanism.
About the research
The broader impact of our work is that we have new insights into changes in soil C and nutrient cycling induced by shifts in plant community compositions, which commonly occur under climate changes and human disturbance. In depth knowledge into how plant composition alters ecosystem function is urgently needed to produce reliable predictions and future models.
We still do not know whether this trade-off mechanism is species-specific or widely applicable, regardless of whether the invader is native or exotic? Perhaps the answer to this will be trait dependent. More case studies are needed, from different continents and species, to test this mechanism of trade-off. The next thing I want to investigate is to test whether this trade-off is the same with exotic invaders, or those whose range has expanded as a result of climate change, getting a funding support would be the first step.
About The Author
I am a forest ecologist focusing on soil carbon sequestration and greenhouse gas emissions under climate changes and human disturbances. I studied several ecosystems ranging from warm-temperate forests to boreal peatlands thanks to my first two job opportunities. I joined the International Centre for Bamboo and Rattan (a research unit focused on resources, ecology, and uses related to bamboo and rattan) in 2016. Since then, I learned that planting bamboos could ease poverty in China by means of its function to provide thousands of products (from face tissue to floorboards). These bamboo products could replace other wood products, and thus sequester a huge amount of CO2), but it is a controversial plant due to ecological and environmental risks. My professional training allows me to help solve this debate, so I applied a grant from National Natural Science Foundation of China for this research.
The very first time that ecology made an impact on me I believe is the Xiaoshui river and Cimu mountain in my village (rural area of Anqiu city, Shandong province in east China). I spent most of my spare time there during my childhood, for fishing, flying kite, chasing grasshoppers… I loved to get close to nature. After I graduated from university, I decided to get a master degree in ecology – which I thought could bring me back to my childhood – so I joined Prof. Chenghua Xiang’s lab at Sichuan Academy of Forestry. Three years later, in 2007, I joined Prof. Shirong Liu’s lab at Chinese Academy of Forestry (CAF), this time pursuing a PhD degree of Ecology. After getting my PhD degree I worked at CAF as assistant research professor for 3 years and during this time I visited the Tibetan Plateau very frequently. Before joining my current institute, I travelled to Canada and worked with Prof. Jianghua Wu at Memorial University of Newfoundland as a postdoctoral fellow focusing on boreal peatlands for another 3 years. These experiences allowed me recognise and understand forests across China and the world.
I am currently a research professor at International Centre for Bamboo and Rattan, State Forestry and Grassland Administration, and leading a team of forest (bamboo) ecosystem structure and function. This article and its sister article (Luan et al., Journal of Ecology 109(3): 1236-1249) are two papers that I am most proud of. In that paper, we show that the functional diversity of decomposers modulates and largely determines litter decomposition affected by a woody grass invasion along a climate gradient. Including the changes in decomposer functional groups, particularly large-bodied soil animals, and their interaction with litter traits, would provide a mechanistic and more reliable prediction on ecosystem functions altered by invaders than a functional trait-based framework under current and future climate.
The best part about being an ecologist is being able to be close to, explore, and learn from nature. I am surprised by the tiny and slight gear of nature to changes or disturbances. There is no worst thing about being an ecologist. However, in my early career time, meeting mountain leeches or snakes when doing field work was the worst thing.
In my spare time, I enjoy reading, playing with my two boys, and playing table tennis. If I had to give one piece of advice to someone it would be devote yourself to it, you will find something surprises you. Open your mind, you will surprise yourself.