Qi Jingen, Marshall John D, Mattson Kim G
Department of Forest Resources, University of Idaho, Moscow, ID 83844-1133, USA.
New Phytol. 1994 Nov;128(3):435-442. doi: 10.1111/j.1469-8137.1994.tb02989.x.
Total and basal respiration (R and R , respectively) of intact and undisturbed roots of one-year-old Douglas fir seedlings, Pseudotsuga menziesii var. glauca [Beissn] Franco, were measured at experimentally varied soil carbon dioxide concentrations ([CO ]). Use of specially designed root boxes and a CO gas-flow compensating system designed around an infrared gas analyzer (IRGA) allowed controlled delivery of CO to roots and simultaneous measurements of CO released by roots. Root respiration rate responded to each inlet [CO ], independent of whether the previous concentration had been higher or lower, within two to three hours (paired t test = 0.041, P= 0.622, and n= 13). Total and basal respiration rates decreased exponentially as soil [CO ] rose from 130 ppm, well below atmospheric [CO ], to 7015 ppm, a concentration not uncommon in field soils. Analyses of variance (ANOVA) showed that the effects of soil [CO ] on rates of total and basal root respiration were statistically significant. Root respiration rates decreased by 4 to 5 nmol CO g dry weight of roots s for every doubling of [CO ] according to the following equations: ln(R ) (nmol CO g s ) = 5.24-0.30*ln[CO ] with r= 0.78, P < 0.0001, and n= 70; and ln(R ) (nmol CO g s ) = 6.29-0.52 * ln[CO ] with r= 0.82, P < 0.0001, and n= 35. The sensitivity of root respiration to [CO ] suggests that some previous laboratory measurements of root respiration at atmospheric [CO ], which is 3 to 10-fold lower than [CO ] in field soils, overestimated root respiration in the field. Further, the potential importance of soil [CO ] indicates that it should be accounted for in models of below-ground carbon budgets.
在实验控制的不同土壤二氧化碳浓度（[CO₂]）条件下，对一年生花旗松（Pseudotsuga menziesii var. glauca [Beissn] Franco）幼苗完整且未受干扰的根系的总呼吸速率和基础呼吸速率（分别为R和R₀）进行了测定。使用专门设计的根箱以及围绕红外气体分析仪（IRGA）设计的CO₂气流补偿系统，能够向根系控制性地输送CO₂，并同时测量根系释放的CO₂。根系呼吸速率在两到三小时内对每个输入的[CO₂]都有响应，与之前的浓度是高还是低无关（配对t检验 = 0.041，P = 0.622，n = 13）。当土壤[CO₂]从远低于大气[CO₂]浓度的130 ppm上升至7015 ppm（该浓度在田间土壤中并不罕见）时，总呼吸速率和基础呼吸速率均呈指数下降。方差分析（ANOVA）表明，土壤[CO₂]对根系总呼吸速率和基础呼吸速率的影响具有统计学意义。根据以下方程，每使[CO₂]翻倍，根系呼吸速率就会降低4至5 nmol CO₂ g⁻¹干重根系 s⁻¹：ln(R)（nmol CO₂ g⁻¹ s⁻¹） = 5.24 - 0.30 * ln[CO₂]，r = 0.78，P < 0.0001，n = 70；以及ln(R₀)（nmol CO₂ g⁻¹ s⁻¹） = 6.29 - 0.52 * ln[CO₂]，r = 0.82，P < 0.0001，n = 35。根系呼吸对[CO₂]的敏感性表明，之前一些在大气[CO₂]浓度（比田间土壤中的[CO₂]浓度低3至10倍）下对根系呼吸进行的实验室测量高估了田间的根系呼吸。此外，土壤[CO₂]的潜在重要性表明，在地下碳预算模型中应考虑这一因素。
