Differential responses of ecosystem respiration components to experimental warming in a meadow grassland on the Tibetan Plateau

Abstract

a b s t r a c tGlobal warming is anticipated to have profound effects on terrestrial carbon fluxes and thus feed backs to future climate change. Ecosystem respiration (R eco ) is one of the dominant components of biosphere CO 2 fluxes, but the effects of warming on R eco are still unclear. A field warming experiment using open top chambers (OTCs) was conducted in a meadow grassland on the Tibetan Plateau to study the effects of warming on the components of R eco . Warming significantly enhanced above-ground plant respiration (R agb ) and total autotrophic plant respiration (R plant ) by 28.7% and 19.9%, respectively, but reduced heterotrophic respiration (R h ) by 10.4%. These different responses resulted in the insensitive responses of R eco and soil respiration (R s ) to the experimental warming. The warming treatment also increased R plant /R eco and R agb /R eco by 8.4% and 17.3%, respectively, while decreasing R h /R eco by 19.0%, suggesting that warming could eventually cause R eco to be dominated by R plant . Enhancements in R plant and R agb were related to the warming-induced increases in aboveground biomass (AGB) while reduced R h was closely coupled with warming-induced decrease of microbial biomass carbon. Our results highlight that the differential responses of the components of R eco to different environmental physics under warming scenarios should be taken into consideration to project the future carbon-climate feed backs.

Comparison of Carbon-Use Efficiency Among Different Land-Use Patterns of the Temperate Steppe in the Northern China Pastoral Farming Ecotone

“…The root respiration, as a component of Ra and Re, showed no significant correlation with CUE (Figure 8d). Previous studies have rarely considered Rr, because it is a very small proportion of Re and is hard to accurately determine [24,50]. Similarly, we did not find a comparable conclusion on the relation between Rr and CUE.…”

“…The LAI is a major explanatory factor for CUE changes under different land uses of steppe (91%, Figure 9a). Although it was slightly lower than Ra (Figure 8b, 97%), LAI still explained more of the CUE variation than Re (Figure 8a, 84%), whereas previous research has mostly focused on the contribution of Re [20,24,52]. The relation between LAI and productivity has been proven repeatedly and applied in biomass modeling with remote-sensing data [53,54].…”

“…Previous research has already promoted deep understanding of how artificial experimental temperature increases change the ecosystem CUE by influencing soil organic carbon release [24,34,36]. Also, using an experimental approach, Metcalfe et al [41] studied the influence of drought on CUE, which suggested that severe drought restrained the respiration of plants and soil microbial of ecosystems, causing the decrease of Re, and finally decreased the ecosystem CUE.…”

“…According to our results, the variation of ecosystem CUE may be primarily influenced by the change of the Ra consumption of plants themselves. The high correlation of Rab to CUE (91%, Figure 8c) was assumed to rely on the Ra regulation mechanism mentioned above, as in steppe ecosystems, Rab was the major part of Ra and the intensity ( Figure 6) and proportion of Rr to Ra [24,48] were both low. Though Rh and Rb were both significantly correlated with CUE (Figure 8e,f), we contend that this correlation is not a universal phenomenon.…”

“…Therefore, the key to measuring the ecosystem CUE accurately during experimental determinations is the accurate division of Re into Ra and Rh [24,25]. In addition, Re also can be roughly divided into two parts: belowground respiration (Rb) and aboveground respiration (Rab), according to the location in which the respiration takes place [26].…”