Plant species, atmospheric CO2 and soil N interactively or additively control C allocation within plant-soil systems.
Two plant species, Medicago truncatula (legume) and Avena sativa (non-legume), were grown in low- or high-N soils under two CO2 concentrations to test the hypothesis whether C allocation within plant-soil system is interactively or additively controlled by soil N and atmospheric CO2 is dependent upon plant species. The results showed the interaction between plant species and soil N had a significant impact on microbial activity and plant growth. The interaction between CO2 and soil N had a significant impact on soil soluble C and soil microbial biomass C under Madicago but not under Avena. Although both CO2 and soil N affected plant growth significantly, there was no interaction between CO2 and soil N on plant growth. In other words, the effects of CO2 and soil N on plant growth were additive. We considered that the interaction between N2 fixation trait of legume plant and elevated CO2 might have obscured the interaction between soil N and elevated CO2 on the growth of legume plant. In low-N soil, the shoot-to-root ratio of Avena dropped from 2.63 +/- 0.20 in the early growth stage to 1.47 +/- 0.03 in the late growth stage, indicating that Avena plant allocated more energy to roots to optimize nutrient uptake (i.e. N) when soil N was limiting. In high-N soil, the shoot-to-root ratio of Medicago increased significantly over time (from 2.45 +/- 0.30 to 5.43 +/- 0.10), suggesting that Medicago plants allocated more energy to shoots to optimize photosynthesis when N was not limiting. The shoot-to-root ratios were not significantly different between two CO2 levels.
F U
Shenglei
S
Institute of Ecology, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China. sfu@scbg.ac.cn
Ferris
Howard
H
D000388:Air; D018554:Avena / Q000378:metabolism*; D002244:Carbon / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology; D002245:Carbon Dioxide / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology; D017753:Ecosystem; D046913:Medicago truncatula / Q000378:metabolism*; D009584:Nitrogen / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology; D012987:Soil
D012987:Soil; D002245:Carbon Dioxide; D002244:Carbon; D009584:Nitrogen