State Key Lab. of Vegetation and Environmental Change, Inst. of Botany, Chinese Academy of Sciences, Xiangshan, Beijing 100093, China.
J Environ Qual. 2009 Dec 30;39(1):251-9. doi: 10.2134/jeq2009.0109. Print 2010 Jan-Feb.
The impact of elevated atmospheric CO(2) concentration on plant communities is varied and strongly dependent on the dominant species response, as well as nutrient conditions. Responses of a dominant species (Leymus chinensis) to elevated CO(2) and N application were examined with open-top chambers in a typical temperate grassland in northern China for 3 yr. The significant effect of elevated CO(2) on L. chinensis growth was mainly reflected in the higher photosynthetic rates, increased leaf number, larger shoot and root biomass, and higher root/shoot (R/S) ratio. Enhancement of root biomass induced by elevated CO(2) was larger (40%) than that of shoot biomass (9%). In contrast, N application had a significant impact on most growth indices examined in this study, which was reflected in the enhanced aboveground growth and depressed belowground growth. Nitrogen application significantly reduced the R/S ratio by an average of 40%. Nitrogen addition significantly enhanced the proportion of senescent biomass and decreased the proportion of green leaf biomass under elevated CO(2). There were no CO(2) x N interactions on most of the measured variables, except on photosynthetic rate and the proportion of aboveground biomass. Plant growth variables showed high interannual variation. These results indicate that belowground growth of L. chinensis is more sensitive to elevated CO(2) than is the aboveground. Aboveground growth of L. chinensis is much more sensitive to N application than to CO(2) enrichment. Therefore, the effect of elevated CO(2) on L. chinensis steppe is more likely to be underestimated if only aboveground parts are considered.
大气 CO2 浓度升高对植物群落的影响是多样的，强烈依赖于优势物种的响应以及养分条件。通过在中国北方典型温带草原的开顶式气室，对优势物种（中华羊茅）对 CO2 升高和 N 应用的响应进行了 3 年的研究。CO2 升高对中华羊茅生长的显著影响主要反映在更高的光合速率、增加的叶片数、更大的地上和地下生物量以及更高的根/茎比（R/S）上。CO2 升高诱导的根生物量增加（40%）大于地上生物量增加（9%）。相比之下，N 应用对本研究中大多数生长指数都有显著影响，反映在地上生长增强和地下生长抑制上。N 应用平均降低 R/S 比 40%。N 添加显著增强了 CO2 升高下衰老生物量的比例，降低了绿叶生物量的比例。除了光合速率和地上生物量比例外，大多数测量变量上都没有 CO2 x N 相互作用。植物生长变量表现出高度的年际变化。这些结果表明，中华羊茅的地下生长对 CO2 升高比地上生长更敏感。中华羊茅的地上生长对 N 应用比对 CO2 富集更敏感。因此，如果只考虑地上部分，CO2 升高对中华羊茅草原的影响可能被低估。
