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Tropical Forests Adjust Strategies
Context:
Tropical forests, storing a third of global carbon in their wood and soils, face an uncertain future as a carbon sink due to concerns about nutrient-poor soils potentially hindering the growth of mature and recovering forests.
Tropical Forests as Carbon Sinks:
- Tropical forests store one-third of the world’s carbon in their wood and soils.
- Uncertainty existed about their ability to thrive due to nutrient-poor soils.
Hopeful Findings:
- Study in New Phytologist suggests flexible nutrient acquisition strategies in forests.
- Higher atmospheric CO2 could boost tropical forest growth.
- Concerns about phosphorus scarcity limiting forest growth.
- Trees use phosphatase enzyme and mycorrhizal fungi to access phosphorus.
- Strategies involve significant carbon and nitrogen costs.
Study Parameters:
- Conducted in Panama’s lowland tropical wet forest.
- Covered 76 plots across 16 square kilometres, ranging from pastures to 600-year-old forests.
- Plots fertilised with nitrogen, phosphorus, or both.
Nutrient Response in Forests:
- Variable Responses
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- Younger forests: Nitrogen addition increased phosphatase activity.
- Older forests: Phosphorus addition increased phosphatase activity.
- Phosphatase Flexibility:
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- Phosphatase activity increased with nitrogen and decreased with phosphorus.
- Mycorrhizal responses were less predictable.
- Activity of phosphatase and mycorrhizal fungi measured over a year.
Implications for Climate Solutions:
- Encouraging Results:
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- Flexibility in nutrient acquisition strategies shows trees actively respond to nutrient availability.
- Potential buffering capacity to alleviate future nutrient limitations.
- Cautions:
- Uncertainty if flexibility will suffice for all future nutrient needs.
- Phosphatase’s reliance on potentially scarce phosphorus could limit its effectiveness.
- Resilience: The ability to adjust strategies suggests forests may maintain productivity and recover from land-use changes in a carbon-rich world.
Recommendations for Reforestation:
- Nutrient Considerations:
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- Importance of considering nutrient limitations in reforestation efforts.
- Use diverse tree species with various phosphorus acquisition strategies.
- Use species adapted to local phosphorus levels.
- Optimism for Forests as Climate Solutions
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- Forests offer immediate, low-cost climate solutions with co-benefits like watershed protection and biodiversity enhancement.
- Science can guide proper implementation to ensure long-term carbon sequestration.
