Response of carbon budget to climate change of the alpine meadow in Gannan using the CENTURY model

Abstract

Alpine meadows have become particularly vulnerable to climate change. Variations in precipitation and temperature affect the ecological production of a region. The matrices for ecosystem change include net primary production (NPP), net photosynthesis (PsnNet), and net ecosystem production (NEP), of which NEP is the most important. Using the CENTURY model for alpine meadows, we investigated the response of NEP to climate change from 1969 to 2018 in Gannan, Gansu Province, China. The distribution pattern of NEP in Gannan was simulated with the model. The Mann–Kendall trend test was used to analyze the interannual variation of NEP for the individual counties and the entire study area over a 50-year period. The results showed the annual NEP distribution pattern varied widely in the region, with the highest NEP values in the southeastern part while the northwestern part showed the lowest. The highest NEP was measured in summer with sufficient precipitation and higher temperatures, whereas the lowest values occurred in winter. The total carbon sequestered in the Gannan alpine meadow over the last 50 years was 43580.9 gC, with the average annual NEP of the alpine meadow being approximately 813.62 gC m−2 year−1. Due to the combined effects of precipitation and temperature variations, NEP exhibits significant seasonal and interannual variations. The simulated NEP values of the seven counties fluctuated over the last 50 years, with each county showing an upward trend and the simulated NEP in the entire Gannan area also showing a clear upward trend that mutated around the year 1990. Both precipitation and temperature were found to be significantly and positively correlated with NEP. Precipitation was a significant driving factor, while temperature interacted with precipitation on the carbon budget. The carbon budget in the alpine meadow was stabilized by increasing precipitation and temperature. Estimates from NEP were in satisfactory correlation with measurements (r2=0.74, n=25 at p<0.01). Our findings provide preliminary understanding of the carbon budget and climatic feedback in Gannan alpine meadows which will help to predict carbon fluxes in the terrestrial biosphere and the impacts of climate change. HIGHLIGHTS Mapping the distribution pattern of NEP in Gannan from 1969 to 2018.; Determining the inter-annual changes in NEP.; Evaluating the potential driving mechanisms responsible for the changes in the carbon budget.;

Keywords

• alpine meadow
• century model
• climate change
• mann–kendall analysis
• net ecosystem productivity