CO2浓度增加和不同氮肥水平对冬小麦根系呼吸及生物量的影响

 依托FACE(Free-air CO₂ enrichment)研究平台, 利用特制分根集气生长箱, 采用静态箱-GC(Gas chromatography)法, 连续两年研究 了大气CO₂浓度升高和不同氮肥水平对冬小麦拔节期、孕穗抽穗期和灌浆末期的根系呼吸及生物量的影响。两季结果表明, CO₂浓度升高和高氮 肥量均不同程度地增加了3个阶段的地上部和地下部的生物量, 这有利于增加根茬的还田量; CO₂浓度升高对冬小麦不同生长阶段的根系呼吸影 响不同, 在拔节期影响较小;孕穗抽穗期显著增加了根系呼吸, 2004~2005季分别增加33.8%(148.1 mg N&;#8226;kg^-1 干土, HN)和43.9%(88.9 mg N&;#8226;kg^-1 干土, LN), 2005~2006季分别为23.8%(HN)和28.9%(LN); 而灌浆末期显著降低了根系呼吸, 2004~2005季分别降低31.4%(HN)和23.3% (LN), 2005~2006季分别为25.1%(HN)和18.5%(LN); 高施氮量比低施氮量促进了根系呼吸; 随着作物生长根系呼吸与地下生物量呈显著线性负相 关, 高CO₂环境中的R²变小,表明随着作物生长发育高CO₂浓度降低了作物根系呼吸与地下部生物量积累间的相关性.

EFFECT OF ELEVATED ATMOSPHERIC CO2 CONCENTRATION AND LEVEL OF NITROGEN FERTILIZER ON ROOT RESPIRATION AND BIOMASS OF WINTER WHEAT

Aims Understanding belowground processes will help in determining the potential feedback of soil C storage on increased atmospheric CO2 concentration. Information on root respiration and biomass are important for understanding implications of environmental change on soil carbon cycling and sequestration. Because cropland is an important terrestrial ecosystem within the global climate change context, separately quantifying the response of crop root respiration and biomass to CO2 enrichment has important implications for agro-ecosystems, for predicting the magnitude and direction of soil C feedbacks. We observe them in a field experiment and evaluate the potential effect of elevated atmospheric CO2 concentration. Methods We used a free-air carbon dioxide enrichment (FACE) system and static chamber-GC (gas chromatography) method to study the effects of elevated atmospheric CO₂ concentration and nitrogen fertilizer on root respiration and biomass of wheat (Triticum aestivum cv Yangmai 14) during two consecutive seasons, determined by a novel split root growth and gas collection system. Important finding Both elevated CO₂ concentration and high nitrogen (HN, 148.1 mg N&;#8226;kg^-1 dry soil weight) application enhanced above- and belowground biomass in three different growth stages. The increase in belowground biomass under elevated CO₂ concentration favors more residual roots to revert to field. Elevated CO₂ concentration significantly stimulated root respiration at the booting-heading stages, which increased by 33.8% and 43.9% in 2004–2005, and by 23.8% and 28.9% in 2005– 2006 in both high and low nitrogen (LN, 88.9 mg N&;#8226;kg^-1 dry soil weight) application, respectively, and significantly depressed root respiration at the late of filling stage by 31.4% and 23.3% in 2004–2005, and by 25.1% and 18.5% in 2005– 2006 in both HN and LN treatments, respectively; however, no significant effect was found at the jointing stage. High nitrogen application promoted more root respiration than low nitrogen. While a significantly negative liner correlation between root respiration rate and belowground biomass was observed, the R² of correlative coefficient under elevated CO₂ concentration was small, which showed elevated CO₂ concentration reduced the correlation of both root respiration and accumulation of belowground biomass with wheat growing.