Xuhui Zhou

• Anthropogenic nitrogen (N) addition may substantially alter the terrestrial N cycle. However, a comprehensive understanding of how the ecosystem N cycle responds to external N input remains elusive. • Here, we evaluated the central tendencies of the responses of 15 variables associated with the ecosystem N cycle to N addition, using data extracted from 206 peer-reviewed papers. • Our results showed that the largest changes in the ecosystem N cycle caused by N addition were increases in soil inorganic N leaching (461%), soil NO₃⁻ concentration (429%), nitrification (154%), nitrous oxide emission (134%), and denitrification (84%). N addition also substantially increased soil NH₄+ concentration (47%), and the N content in belowground (53%) and aboveground (44%) plant pools, leaves (24%), litter (24%) and dissolved organic N (21%). Total N content in the organic horizon (6.1%) and mineral soil (6.2%) slightly increased in response to N addition. However, N addition induced a decrease in microbial biomass N by 5.8%. • The increases in N effluxes caused by N addition were much greater than those in plant and soil pools except soil NO₃⁻, suggesting a leaky terrestrial N system.

... According to Bayes' theorem, posterior PDFs of model parameters (p) can be obtained from prior knowledge of parameters and information generated by comparison of simulated and observed variables. The theorem can be described as (Mosegaard and Sambridge 2002). ...

... sensitivities to climate warming for land C storage compared with ocean C storage ... stimulates plant respiration more than photosynthesis, many plant-growth models predict an increase ... A simple substrate-based model of plant acclimation to temperature shows that respiration is ...

•Partitioning soil respiration into autotrophic (RA) and heterotrophic (RH) components is critical for understanding their differential responses to climate warming.•Here, we used a deconvolution analysis to partition soil respiration in a pulse warming experiment. We first conducted a sensitivity analysis to determine which parameters can be identified by soil respiration data. A Markov chain Monte Carlo technique was then used to optimize those identifiable parameters in a terrestrial ecosystem model. Finally, the optimized parameters were employed to quantify RA and RH in a forward analysis.•Our results displayed that more than one-half of parameters were constrained by daily soil respiration data. The optimized model simulation showed that warming stimulated RH and had little effect on RA in the first 2 months, but decreased both RH and RA during the remainder of the treatment and post-treatment years. Clipping of above-ground biomass stimulated the warming effect on RH but not on RA. Overall, warming decreased RA and RH significantly, by 28.9% and 24.9%, respectively, during the treatment year and by 27.3% and 33.3%, respectively, during the post-treatment year, largely as a result of decreased canopy greenness and biomass.•Lagged effects of climate anomalies on soil respiration and its components are important in assessing terrestrial carbon cycle feedbacks to climate warming.Partitioning soil respiration into autotrophic (RA) and heterotrophic (RH) components is critical for understanding their differential responses to climate warming.Here, we used a deconvolution analysis to partition soil respiration in a pulse warming experiment. We first conducted a sensitivity analysis to determine which parameters can be identified by soil respiration data. A Markov chain Monte Carlo technique was then used to optimize those identifiable parameters in a terrestrial ecosystem model. Finally, the optimized parameters were employed to quantify RA and RH in a forward analysis.Our results displayed that more than one-half of parameters were constrained by daily soil respiration data. The optimized model simulation showed that warming stimulated RH and had little effect on RA in the first 2 months, but decreased both RH and RA during the remainder of the treatment and post-treatment years. Clipping of above-ground biomass stimulated the warming effect on RH but not on RA. Overall, warming decreased RA and RH significantly, by 28.9% and 24.9%, respectively, during the treatment year and by 27.3% and 33.3%, respectively, during the post-treatment year, largely as a result of decreased canopy greenness and biomass.Lagged effects of climate anomalies on soil respiration and its components are important in assessing terrestrial carbon cycle feedbacks to climate warming.

Background : Climate manipulation experiments have found lagged responses in biomass and community composition. Aims : To look for lagged responses of flowering phenology and effects on duration of reproductive phases. Methods: Treatment and post-treatment year phenological data from 12 species in a 1-year step warming and double precipitation experiment was examined. Results: Changes in phenology due to the previous year's warming were in the opposite direction to those observed during the treatment year. Six species responded to warming in 2004, delaying flowering 6.2 days and fruiting 7.9 days. Unlike 2003, no species advanced flowering phenology in 2004. Delays resulted from a soil moisture deficit in formerly warmed plots that lasted 3 months or more after warming ended. Increased precipitation altered phenology in one species but did not affect duration of reproductive phases. While 10 of 11 responsive species entered bud phase earlier under warming than in controls in 2003, in only two species showed a phenological delay at the beginning of the bud phase in 2004. Warming tended to shorten flowering and fruiting stages and total duration in spring annuals. Conclusions: Together, these results suggest that climate anomalies can influence phenology in the following year, here due to a lag in soil moisture recharge.

Partitioning soil CO2 efflux into autotrophic (RA) and heterotrophic (RH) components is crucial for understanding their differential responses to climate change. We conducted a long-term experiment (2000–2005) to investigate effects of warming 2°C and yearly clipping on soil CO2 efflux and its components (i.e. RA and RH) in a tallgrass prairie ecosystem. Interannual variability of these fluxes was also examined. Deep collars (70 cm) were inserted into soil to measure RH. RA was quantified as the difference between soil CO2 efflux and RH. Warming treatment significantly stimulated soil CO2 efflux and its components (i.e. RA and RH) in most years. In contrast, yearly clipping significantly reduced soil CO2 efflux only in the last 2 years, although it decreased RH in every year of the study. Temperature sensitivity (i.e. apparent Q10 values) of soil CO2 efflux was slightly lower under warming (P>0.05) and reduced considerably by clipping (P<0.05) compared with that in the control. On average over the 4 years, RH accounted for approximately 65% of soil CO2 efflux with a range from 58% to 73% in the four treatments. Over seasons, the contribution of RH to soil CO2 efflux reached a maximum in winter (∼90%) and a minimum in summer (∼35%). Annual soil CO2 efflux did not vary substantially among years as precipitation did. The interannual variability of soil CO2 efflux may be mainly caused by precipitation distribution and summer severe drought. Our results suggest that the effects of warming and yearly clipping on soil CO2 efflux and its components did not result in significant changes in RH or RA contribution, and rainfall timing may be more important in determining interannual variability of soil CO2 efflux than the amount of annual precipitation.