Short lifespan and ‘prime period’ of carbon sequestration call for multi-ages in dryland tree plantations

Enhancing forest cover is important for effective climate change mitigation. Studies suggest that drylands are promising areas for expanding forests, but conflicts arise with increased forest area and water consumption. Recent tree mortality in drylands raises concerns about carbon sequestration potential in tree plantations. Using Chinese dryland tree plantations as an example, we compared their growth with natural forests. Our results suggested plantation trees grew 1.6–2.1 times faster in juvenile phases, significantly shortening time to maturity (13.5 vs. 30 years) compared to natural forests, potentially stemming from simple plantation age structures. Different from natural forests, 74% of trees in plantations faced growth decline, indicating a short "prime period" for carbon sequestration and even a short lifespan. Additionally, a negative relationship between evapotranspiration and tree growth was observed in tree plantations since maturity, leading to high sensitivities of trees to vapor pressure deficit and soil water. However, this was not observed in natural forests. To address this, we suggest afforestation in drylands should consider complex age structures, ensuring a longer prime period for carbon sequestration and life expectancy in tree plantations.