Root production and demography in a california annual grassland under elevated atmospheric carbon dioxide
Root production and demography in a california annual grassland under elevated atmospheric carbon dioxide
复制标题
DOI：
10.1046/j.1365-2486.2002.00514.x
复制
发表时间：
2002-09-01
影响因子：
11.6
通讯作者：
Field, CB
中科院分区：
文献类型：
--
作者：
Higgins, PAT;Jackson, RB;Field, CB
本研究探讨了根生产和营业额在加州草原在第三年的长期实验与环境（LO）和两个环境大气CO2（HI），使用收获，向内生长的核心，和minirrectrons。根据一次性收获的数据，根生物量是32%以上的HI治疗，相当于刺激地上生产在研究年。然而，在我们的系统中的优势物种在CO2浓度升高的情况下光合作用增加30-70%，这比地上和地下生物量的增加要大得多。一个可能的解释是，增加了根系周转，这可能是额外固定碳的汇。在四个日期收获的两种处理的向内生长核心的累积根产量是在单一收获的核心的2-3倍，这表明在生长季节内大量的根周转。微型电子管数据证实了这一结果，表明生产和死亡率同时发生在大部分季节。结果表明，无室（X）、LO和HI试验区的累积根产量分别比最大根长高54%、47%和44%。然而，CO2浓度升高对周转率的影响不大（即在LO和HI地块中，全年大部分时间的周转率是相等的），累积根产量不受治疗的影响。CO2浓度升高增加每月生产的新根长度（59%），只有在本赛季结束时（4月至6月），根生长基本上停止在LO地块，但继续在HI地块。这种季末产量的增加与先前描述的HI地块中土壤含水量增加18%相吻合。CO2处理对根系总长度无明显影响。根死亡率不受影响的升高CO2在所有月份，除了4月，在HI地块生长的植物有较高的死亡率。总之，这些结果表明，根周转是相当大的草地群落，很容易错过破坏性的土壤取芯。然而，在CO2浓度升高下细根周转率的增加显然不是该系统中额外光合产物的主要吸收库。
This study examined root production and turnover in a California grassland during the third year of a long-term experiment with ambient (LO) and twice-ambient atmospheric CO2 (HI), using harvests, ingrowth cores, and minirhizotrons. Based on one-time harvest data, root biomass was 32% greater in the HI treatment, comparable to the stimulation of aboveground production during the study year. However, the 30-70% increase in photosynthesis under elevated CO2 for the dominant species in our system is considerably larger than the combined increase in above and belowground biomass. One possible explanation is, increased root turnover, which could be a sink for the additional fixed carbon. Cumulative root production in ingrowth cores from both treatments harvested at four dates was 2-3 times that in the single harvested cores, suggesting substantial root turnover within the growing season. Minirhizotron data confirmed this result, demonstrating that production and mortality occurred simultaneously through much of the season. As a result, cumulative root production was 54%, 47% and 44% greater than peak standing root length for the no chamber (X), LO, and HI plots, respectively. Elevated CO2 , however, had little effect on rates of turnover (i.e. rates of turnover were equal in the LO and HI plots throughout most of the year) and cumulative root production was unaffected by treatment. Elevated CO2 increased monthly production of new root length (59%) only at the end of the season (April-June) when root growth had largely ceased in the LO plots but continued in the HI plots. This end-of-season increase in production coincided with an 18% greater soil moisture content in the HI plots previously described. Total standing root length was not affected by CO2 treatment. Root mortality was unaffected by elevated CO2 in all months except April, in which plants grown in the HI plots had higher mortality rates. Together, these results demonstrate that root turnover is considerable in the grassland community and easily missed by destructive soil coring. However, increased fine root turnover under elevated CO2 is apparently not a major sink for extra photosynthate in this system.