干旱区生态环境知识资源中心

This investigation examines the contributions of autotrophic respiration (R-A) and heterotrophic respiration (R-H) to total soil respiration (R-T) in two typical forests (Armeniaca sibirica Lam. (AS) and Vitex negundo Linn. var.. Heterophylla (VN)) in semi-arid region of North China. The soil respiration components’ responses to changing temperatures were also examined. A similar pattern was identified in the diurnal variation of R-T and R-H; R-A exhibited a different diurnal pattern with nighttime values being greater than daytime values. On the seasonal scale, the variations of R-T, R-H and R-A exhibited a similar and strong single-peak pattern with values peaking in early August for both forest sites. The seasonal variations of RT, R-A and R-H were strongly affected by soil temperature and moisture, with soil temperature accounting for more variations in soil respiration components at both sites. The contributions of R-A to R-T (R-A/R-T ratio) exhibited remarkable diurnal and seasonal variations. Due to the lag time between photosynthesis and root respiration, diurnal variation of R-A/R-T was lower during the daytime than at night in both AS and VN sites. Meanwhile, under the influence of plant physiology, the seasonal variation of R-A/R-T presented a bimodal curve, with ratios peaking in April and August and bottoming out in October, In addition, due to having higher fine root biomass, VN had a significantly higher annual mean R-A/R-T ratio (24.44%) than AS (17.46%). Regardless of vegetation type, the responses of R-T, R-A and R-H to soil temperature were more sensitive during the dormant season than during the growing season, with their Qio ranked as R-A > R-T > R-H. Our results indicate that R-A is more sensitive to temperature variation than RH, and that the dormant season may have greater soil respiration potential than the growing season in our study areas in the context of increasing global temperatures. The response of R-T, R-A and R-H to soil temperature showed greater sensitivity for VN than for AS during the annual time scale. We can infer that soil respiration under VN may be more sensitive to temperature variations under global warming scenarios. (C) 2016 Elsevier B.V. All rights reserved.