Effects of warming and nitrogen addition on soil respiration, microbial properties and plant growth in grassland ecosystems

• Main Author: Fang, Chao
• Other Authors: Reynolds, James F.
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2020
• Subjects: Arctic; Climate change
• Online Access: https://hdl.handle.net/10067/1701020151162165141; https://repository.uantwerpen.be/docstore/d:irua:1592

Abstract: Climate warming and atmospheric nitrogen deposition are two important components of global changes, which have profound impacts on the carbon cycle of terrestrial ecosystems. In the context of global changes, microbes and plants produce carbon feedback to the atmosphere through respiration. Therefore, a comprehensive understanding of the responses of soil respiration, microbial community and plant growth to climate change is of great significance for the parameterization of earth process models and the accurate prediction of the future global carbon cycle. Grassland, one important biota in terrestrial ecosystems, accounts for 40% of the terrestrial vegetation cover. However, the study of key soil carbon processes in grassland ecosystems in areas sensitive to climate change (high latitude or high altitude) is still lacking. Thus, we conducted field manipulative warming and nitrogen addition experiments in a semi-arid alfalfa-pasture and a fenced semi-arid natural grassland in the Loess Plateau of China, and evaluated the responses of above- and belowground biomass distribution and production to long-term (10 years) geothermal warming in a sub-arctic grassland. Open-top chambers were used to elevate temperature passively and geothermal warming was achieved due to an earthquake including three soil temperature treatments (+0 oC, +3.6 oC and +7.6 oC) above soil ambient. N was enriched at a rate of 4.42 g m-2 yr-1 with NH4NO3. The main findings are as following: (1) During April 2014 to March 2016 in the semi-arid alfalfa-pasture, N addition increased Rs by 14% over the two-year period; and warming stimulated Rs by 15% in the non-growing season, and inhibited it by 5% in the growing season, which can be explained by decreased plant coverage and soil water. The main effect of N addition did not change with time, but that of warming changed with time, with the stronger inhibition observed in the dry year. When N addition and warming were combined, an antagonistic effect was observed in the growing season, ...