关键词: 高寒草甸, 增温, 优势物种去除, 海拔梯度, 生态系统碳通量

Abstract:

Experiments were conducted to investigate the effects of warming and dominant plant species removal on net ecosystem CO₂ exchange (NEE), ecosystem respiration (ER) and gross ecosystem production (GEP) along elevational gradients (3200 m and 4000 m) in the alpine meadow on the Tibetan Plateau. The results showed that GEP was higher than ER at both elevations, indicating that both ecosystems were a net C sink during the growing season in 2017. At a lower elevation (3200 m), warming did not have a significant effect on ecosystem C flux due to water limitation caused by warming. At a wetter high elevation (4000 m), warming significantly stimulated ecosystem C fluxes, on average, the warming-induced increase in GEP (2.30 mg CO₂/(m²·s)) was higher than that in ER (0.62 mg CO₂/(m²·s)), leading to an increase in NEE. Dominant plant species removal did not have a significant effect on ecosystem C flux at either elevations, probably due to the compensatory effects of the remaining species, because the removal on above ground biomass (AGB) or below ground biomass (BGB) was not significant at both elevations. There was no significant interaction between warming and dominant species removal on the ecosystem C fluxes at either elevations. The results reveal the importance of soil moisture in mediating the response of ecosystem C flux to climate warming in alpine meadow ecosystems, and removal of a single dominant plant species may not have a significant impact on ecosystem C flux in species-rich regions.

Key words: alpine meadow, warming, dominant species removal, elevational gradients, ecosystem carbon fluxes