Human caused global change and loss of biodiversity have adverse effects on ecosystem functions, for example, can reduce ecosystem productivity and unbalance nutrient cycling. For this reason, research on biodiversity and ecosystem functions that started in the 1990s has been a hotspot in ecology. A large number of earlier research focused on how the above-ground plant community attributes (e.g. species richness, plant quality, and inter-specific genetic relationship) and their interaction with environmental factors affect single ecosystem functions (such as productivity).  

However, considering only the impact of biodiversity on single ecological processes ignores the fact that ecosystems provide multiple functions and services simultaneously, thus often underestimated the role of biodiversity, which not only comprises the diversity of plants on the ground, but also the diversity of organisms hidden underground, on ecosystem functions. Soil biota participates and plays a key role in almost all biogeochemical processes.  To date, however, it is still unclear how above- and under-ground biodiversity jointly affect forest ecosystem multifunctionality. 

In view of this, YUAN Zuoqiang, WANG Xugao, ZHANG Xiaoke, LI Hui and other members of the innovation team of the Key Laboratory of Forest Ecology and Management of the Chinese Academy of Sciences, measured a total of eight ecosystem functions including forest productivity, plant/soil carbon pool, soil/litter water-holding capacity, seed/litter production in a 25 ha forest plot in a broad-leaved Korean pine forest in Changbai Mountains in Northeast China.

They estimated multifunctionality of the forest ecosystem using a combination of the average method, multi-threshold method (50%, 75%, and 95%) and the single function method, and analyzed the direct and interactive effects of plant diversity, stand structure, tree species trait composition and soil microorganisms (bacteria, fungi and nematodes) on ecosystem multifunctionality. 

Though the eight single ecosystem functions were driven by different factors, the researchers found that multifunctionality of the forest ecosystem was positively related to phylogenetic diversity of woody plants and stand structure, and negatively related to resource-acquiring traits of tree species (e.g., specific leaf area). Phylogenetic diversity indirectly affects forest ecosystem multifunctionality by increasing stand structural complexity.

Soil microorganisms have no direct effect on multifunctionality, but their diversity is a key driver maintaining high levels of multifunctionality. Local abiotic factors mainly affect ecosystem functions indirectly by regulating plant community structure and composition. For example, complex topography reduces stand structural diversity, while soil fertility increases species diversity via reducing the dominance of tree species with resource-acquiring traits.  

In contrast with previous studies examining the impacts of biodiversity at single trophic levels (e.g. plant or microbial diversity) on ecosystem functioning, this study reveals the importance of stand structural- and soil microbial-diversity in maintaining multifunctionality in temperate natural forests. 

This study has been published in Journal of Ecology under the title "Above‐ and below‐ground biodiversity jointly regulate temperate forest multifunctionality along a local‐scale environmental gradient."  

This study was funded by the National Natural Science Foundation of China, the Priority Science & Technology Programme and the Youth Innovation Promotion Association of the Chinese Academy of Sciences.