Forests with rich tree species grow more consistently – Eurasia Review

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A recent study in Scientists progress shows that extreme weather conditions affect species-rich forests less than forests with fewer species. In addition, species rich forests also produce more timber, largely due to the diversity of functional characteristics among species.

This study was conducted by researchers from the German Center for Integrative Biodiversity Research (iDiv) and the Institute of Botany of the Chinese Academy of Sciences (IBCAS). It is based on data from the Biodiversity Ecosystem Functioning Experiment China (BEF-China), the world’s largest experiment studying forest biodiversity and ecosystem functioning.

Forests all over the world are under pressure. Due to increased global warming, they must adapt more and more quickly to climatic fluctuations and the extreme events that accompany them. This leads to tree dieback and reduced growth, resulting in less carbon uptake. Together with increasing emissions, these factors contribute to climate change. In addition, ecosystem services such as climate regulation, water storage and the provision of materials, for example for construction, are also declining.

Researchers studied which factors influence the functioning of forests under climatic stress and how these factors interact. They found that species-rich forests are better protected from the effects of climate stress. For example, if some tree species in a forest grow less due to extreme weather conditions such as heavy rains or drought, others may offset the loss. This mechanism stabilizes the entire system and ensures its productivity.

They also found that species-rich forest stands provide more stable biomass production than monocultures due to protection from weather fluctuations. As a result, the annual growth of wood is less variable.

Lead author Florian Schnabel from iDiv and the University of Leipzig said that the link between species richness and stable productivity, as well as the mechanisms underlying this link, had previously only been demonstrated in grassland experiments.

“We can now, for the first time, show it under experimental conditions for very diverse subtropical forest ecosystems,” he said.

The main reason for the stability of forest growth in this study was not the number of different tree species but their different functional characteristics. For example, one species may grow well in a wet year and another in a dry year. This characteristic, known as “asynchrony,” stems from how different species use inputs such as water, light, and nutrients, and how species subsequently interact. The growth stability of the entire tree community is determined by these characteristics and interactions.

“In particular, the trait-based mechanism underlying the links between tree species richness, asynchrony and community stability remains unknown for forests,” said co-first author, the Dr LIU Xiaojuan from IBCAS.

The study shows that drought tolerance, hydraulic conductance and evaporation capacity are particularly important factors in the growth stability of trees. The more diverse the characteristics of a forest community, the more stable the biomass production rate of this community is under fluctuating climatic conditions. The forest communities with the most stable growth were not those dominated by drought tolerant species, but those with various drought tolerance and water use strategies.

Another study published recently in Ecology and evolution of nature also supports the results of this study.

Both studies show that the stability of growth and productivity in secondary and plantation forests can be improved by increasing the number of tree species. These studies give an important impetus to forest management strategies not only in the subtropics.

They encourage global forest management and carbon offsetting initiatives to focus on planting, restoring and maintaining diverse and species-rich forests. This effort is essential to maintain and increase the stability and productivity of forest growth in the face of climate change.

“These findings have important implications for the United Nations Decade for Ecosystem Restoration (2021-2030). Restoration projects should consider focusing on various mixed species forests to improve stability, especially in the climate change scenario, ”said Prof. MA Keping, President of BEF-China and participant in this study.

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