干旱区生态环境知识资源中心

There is still great uncertainty about the response of global carbon dynamics to land use change and nitrogen (N) fertilizer, especially how to balance between forage production and CO2 emission under land use change and N fertilizer times in alpine meadows.

This objective of this study was to determine the effects of three land uses (i.e., abandoned cropland/pastureland (APL), perennial Elymus nutans (PEN), and annual Avena sativa L. pasture (AO)) and nitrogen fertilizer applied three times a year with the same N dose on aboveground net primary productivity (ANPP) and ecosystem respiration (Re) from 2011 to 2013.

We found that AO had the highest average ANPP and lowest average Re compared with APL and PEN and that there were no significant differences for them between APL and PEN during the experimental period. Nitrogen fertilization did not significantly affect ANPP, root biomass, and seasonal mean Re. Soil temperature could explain about 21.1 and 13-15% of the variation in daily Re for APL and PEN, respectively, but 20.7 and 15.0% of the variation in daily Re for APL and PEN under both with and without N fertilization, respectively. ANPP explained about 49.4% of the variation in seasonal average Re for AO, and the ratio of root biomass and ANPP explained about 45% of the variation in seasonal average Re for AO-N treatment during 2011-2013.

Land use significantly affected ANPP, root biomass, and seasonal mean Re. However, nitrogen addition with different times did not significantly affect seasonal average Re or ANPP and root biomass for all treatments during the experimental period. Therefore, our results suggested that N could not be a limiting factor for plant production in this alpine region.