Net primary productivity response to precipitation varied with different ecosystems in the Tibetan Plateau over the past two millennia

Abstract

The long-term pattern of terrestrial net primary productivity (NPP) response to climate change is important for estimating aboveground biomass and assessing its ecosystem function. NPP accumulation generally increased during warming intervals. However, the relationship between terrestrial NPP and precipitation change has not been comprehensively elucidated owing to the lack of long-term quantitative NPP records. Here, we present an NPP sequence quantitatively reconstructed from annual layers of fossil pollen assemblages spanning the past two millennia. We also explore the relationship between NPP and precipitation during the periods dominated by different ecosystem types. The results revealed that the NPP variation is positively correlated with the alpine meadow, dominated by Cyperaceae species, and negatively correlated with the alpine steppe, dominated by Artemisia and Poaceae species. Additionally, the NPP sequence recorded a remarkable ∼200-year periodic oscillation, which was also recorded in the precipitation sequence. The periodic NPP showed an in-phase relationship with precipitation when the regional ecosystem was marked by the symbiosis of alpine steppe and alpine meadow, and showed an anti-phase relationship with precipitation when the regional ecosystem was dominated by alpine steppe. This study elucidates the relationships between terrestrial NPP and precipitation during the past two millennia and provides foundations for predicting future terrestrial productivity.