摘要
通过盆栽试验,研究了不同施氮0、150和300mgN·kg-1水平下,冬小麦光合产物的分配和根系碳淀积量,分别在苗期、拔节期、花期和灌浆期用13CO2脉冲标记6h,标记6h后和生育期结束后破坏性取样,测定冬小麦地上部、根、土壤和土壤呼吸中的13C含量。结果表明,净光合固定的13C分配到地上部的比例从苗期36.8%~94.1%增加到灌浆期的39.9%~98.3%,施氮处理显著高于不施氮处理,而固定在地下部的13C占冬小麦净吸收比例的0.3%~30%,低氮处理显著高于高氮处理,转移到土壤中碳有1%左右,最大值为2.4%。整个生育时期,低氮处理冬小麦植株输入到土壤的碳量为51.4mgC·株-1,显著高于不施氮处理的36mgC·株-1和高氮处理的34mgC·株-1。生育期结束后,通过直接称量根系干重的方法,估算不同施氮水平下小麦仍有102、105和66mgC·株-1作为根系残体保留在土壤中,因此,在整个生育期结束后,在3个氮水平下冬小麦所固定的大气CO2的量分别是138、156和100mgC·株-1。由此可见,低氮能增加从根系到土壤碳的累积量。
A pot experiment, with winter wheat （ Trticum aestivums L. ）and ^13C pulse labeling technique, was conducted to quantify the distribution and net transloeation of the assimilated C from plants to soil, and investigate the effect of nitrogen（N ）supply on rbizodeposition. Three levels of N fertilizer were prepared： 0 （no nitrogen ）, 150 （ low nitrogen ）and 300 mg N·kg^-1 （high nitrogen ）, and four growth stages of wheat plant were chosen for pulse-labeling with exposure to ^13CO2 in 6-hour for each. Prior to labeling, the soil was isolated from shoot by a PVC sheet. Destructive samplings were applied right after labeling and at the end of the growing season. The results indicated ^13C distribution in shoots decreased from 36.8%-94.1% for the net assimilation at the seeding stage of winter wheat to 39.9%-98.3% for that at the grain filling stage of wheat and was lower in no nitrogen treatment than nitrogen applied. In other side, the proportion of 0.3%-30% retained in roots was higher at the low nitrogen rate than that at the higher one. The net assimilated C incorporated into soil was lower than 1%, with the maximum value 2.4%. Over the growing season, the estimated net plant C input into soil was 51.4 mg C·plant^-1 for low nitrogen treatment and significantly higher than 36 mg C·plant^-1 for no nitrogen and 34 mg C·plant^-1 for high nitrogen treatment. Based on total weight of root biomass at the harvest, winter wheat plant accumulated 102 mg C·plant^-1, 105 mg C·plant^-1 and 66 mg C ·plant^-1 in root residues which were retained in soil after harvest for no nitrogen, lower nitrogen and high nitrogen treatments respectively. Therefore, total of carbon input to soil were 138 mg C ·plant^-1, 156 mg C·plant^-1 and 100 mg C·plant^-1 after a growing season of plants for no, low and high nitrogen supply respectively. Our results demonstrated that in a pot experiment, low nitrogen application could significantly increase the accumulative net C input from root to soil.
出处
《农业环境科学学报》
CAS
CSCD
北大核心
2008年第6期2524-2530,共7页
Journal of Agro-Environment Science
基金
国家自然科学基金面上项目(30471004)
