Lengthening vegetation carbon turnover time across China's forests

Area of Science:

• Terrestrial Ecosystem Science
• Climate Change Research
• Forest Ecology

Background:

• Vegetation carbon turnover time (τ_veg) is a key factor in terrestrial carbon cycle uncertainty.
• Mature forests in Europe and North America show decreased τ_veg due to climate change.
• The trend of τ_veg in younger forests remains unclear.

Purpose of the Study:

• To investigate the temporal trend of vegetation carbon turnover time (τ_veg) in China's predominantly young forests.
• To understand the drivers of τ_veg dynamics in young forest ecosystems.
• To inform land surface models and forest management strategies.

Main Methods:

• Utilized multisource data-model assimilation.
• Employed long-term network observations across China's forests.
• Analyzed forest age structure and environmental factors like nitrogen deposition and CO₂ levels.

Main Results:

• Revealed a significant overall increase in τ_veg across China's forests (0.025 ± 0.002 years per year).
• Observed that in young forests with high nitrogen deposition, rising CO₂ accelerates growth, increasing τ_veg.
• Demonstrated that young forests sequester carbon more effectively due to slower decomposition relative to growth.

Conclusions:

• Forest age significantly influences τ_veg dynamics, with younger forests showing increasing turnover times.
• Accurate assessment of terrestrial carbon cycling and climate mitigation requires incorporating age-dependent τ_veg into land surface models.
• Findings offer insights for forest management to enhance carbon retention and sequestration by optimizing stand dynamics.