研究成果

Phosphorus Limitations Reduce Total Tropical Forest Production by 36%
― Contributes to improved accuracy of terrestrial carbon balance models―

Related Research Program
Environment
Related Research Project
Adaptive forestry

 

Phosphorus Limitations Reduce Total Tropical Forest Production by 36%
Contributes to improved accuracy of terrestrial carbon balance models

Main Points 

  • The extent to which photosynthesis is limited by phosphorus, which tends to be scarce in the tropics, is clarified based on measured data from tropical forests on four continents
  • The total production of tropical and subtropical forests around the world is 36% lower than previously estimated when phosphorus limiting photosynthesis is taken into account.

  • Contribution to improved accuracy in predicting total production in response to changes in the carbon balance of the world's tropical forests and atmospheric CO2 concentrations.

Overview

An international research group including JIRCAS and Kochi University, and led by Professor David Ellsworth of Western Sydney University (Australia), has successfully elucidated the photosynthetic capacity of tropical forest trees under phosphorus constraints. The group has shown that incorporating the limitation of photosynthesis by phosphorus, one of the essential elements of plants, into a model predicting total forest production reduces the total production of tropical and subtropical forests worldwide by 36%, compared to a model that does not incorporate this limitation.
 
Tropical forests account for more than one-third of the total production of terrestrial ecosystems and play an important role in climate change mitigation and adaptation. On the other hand, tropical soils have been weathered and are phosphorus deficient, but there are few measured data on the extent to which phosphorus limits photosynthesis, and its impact on total forest production was unknown.
 
Therefore, an analysis of a dataset sampled from 52 sites on four continents around the world clarified the relationship between phosphorus concentration in leaves and photosynthetic capacity. The results showed that even if nitrogen was abundant, phosphorus limitation caused a reduction in photosynthetic capacity. Furthermore, by incorporating phosphorus limitation into a model for predicting total forest production, the impact of phosphorus constraints on the total production of tropical and subtropical forests worldwide has been successfully quantified.
 
This study also found that the impact of phosphorus on photosynthesis in the tropics is considerably greater than previously assumed, and will contribute to the improvement of the prediction accuracy of carbon balance in land areas.
 
The results of this study were published in the scientific journal Nature Communications on August 25, 2022 (JST).

 

Publication

Authors
DS Ellsworth, KY Crous, MG De Kauwe, LT Verryckt, D Goll, S Zaehle, KJ Bloomfield, P Ciais, LA Cernusak, TF Domingues, ME Dusenge, S Garcia, R Guerrieri, FY Ishida, IA Janssens, Kenzo Tanaka, Tomoaki Ichie, BE Medlyn, P Meir, RJ Norby, PB Reich, L Rowland, LS Santiago, Y Sun, J Uddling, AP Walker, KWLK Weerasinghe, MJ van de Weg, Yun-Bing Zhang, Jiao-Lin Zhang, IJ Wright
Title
Convergence in phosphorus constraints to photosynthesis in forests around the world
Journal
Nature Communications
DOI : https://doi.org/10.1038/s41467-022-32545-0

For Inquiries

JIRCAS President KOYAMA Osamu

Program Director
HAYASHI Keiichi (Environment Program)
Principal Investigator
TANAKA Kenzo (Forestry Division)
Press Coordinator
OMORI Keisuke (Head, Information and Public Relations Office)
E-mail:koho-jircas@ml.affrc.go.jp

 

Reference Information

Tropical forest in Malaysia (left) and forest canopy crane gondola (right)

Tropical forests in Malaysia and other countries are covered with a wide variety of giant trees over 50 meters tall (left). A gondola of a 90m-high canopy observation crane is used to access the leaves of forest canopy trees over 50 m tall to measure photosynthesis (right).

Schematic diagram of photosynthetic capacity of phosphorus-deficient and non-phosphorus-deficient leaves

When phosphorus is deficient, photosynthetic capacity is reduced even when nitrogen is abundant. By incorporating this phenomenon into the model, phosphorus limitation can now be quantified.

Degree of decline in total production of tropical and subtropical forests in the world obtained from model calculations

When the phenomenon of photosynthesis limited by phosphorus is incorporated into the model, total production is predicted to decrease in darker colored areas.