Long-term steady state 13 C labelling to investigate soil carbon turnover in grasslands
Long-term steady state 13 C labelling to investigate soil carbon turnover in grasslands
复制标题
长期稳态 13 C 标记研究草原土壤碳周转
DOI：
--
复制
发表时间：
2007
期刊：
影响因子：
--
通讯作者：
R. Falcimagne
中科院分区：
文献类型：
--
作者：
K. Klumpp;J. Soussana;R. Falcimagne
抽象的。我们已经建立了一个设施，允许稳态13 CO2标记的矮身材植被（12平方米）几年。13 C标记是通过用自我再生的分子筛从室外空气中洗涤CO2，并将其替换为13 C耗尽（−34.7±0.03‰）的化石燃料产生的CO2来获得的。该设施由16个复制的中生态系统组成，可以在自然光和室外温度下追踪植物-土壤系统中光合作用碳的命运。将该方法应用于温带草原土壤有机碳周转的研究。我们测试的假设，放牧和切割草地的低干扰增加粗（>0.2 mm）土壤有机组分中碳的平均停留时间。在长期（14年）的放牧试验中，从高低干扰处理中取样0.5×0.5×0.4 m的草地块体，并将其放置在中型生态系统中，为期两年。在白天，每个围隔中的树冠围栏以开放的气流供应，平均CO2浓度为425 µmol mol−1，δ 13 C为−21.5±0.27‰。在低干扰和高干扰处理中，完全标记的成熟草叶的δ 13 C分别达到−40.8（±0.93）和−42.2‰（±0.60），表明与未标记的对照草叶相比，平均13 C标记强度为12.7‰。两年后，与对照相比，标记的整料中0.2mm以上的土壤总有机质的δ 13 C值平均降低了7.8‰。同位素质量平衡技术被用来计算顶部（0-10厘米）土壤的13 C标记的碳在0.2毫米以上的土壤有机质（即根，根茎和颗粒有机质）的分数。一阶指数衰减模型拟合的未标记的C在这一部分中显示的平均停留时间从22个月增加到31个月，在低相比，高干扰。因此，0.2毫米以上的根，根茎和颗粒有机物的腐烂速度较慢，可能有助于观察到的增加土壤固碳在草原整料暴露于低干扰。
Abstract. We have set up a facility allowing steady state 13CO2 labeling of short stature vegetation (12 m2) for several years. 13C labelling is obtained by scrubbing the CO2 from outdoors air with a self-regenerating molecular sieve and by replacing it with 13C depleted (−34.7±0.03‰) fossil-fuel derived CO2 The facility, which comprises 16 replicate mesocosms, allows to trace the fate of photosynthetic carbon in plant-soil systems in natural light and at outdoors temperature. This method was applied to the study of soil organic carbon turnover in temperate grasslands. We tested the hypothesis that a low disturbance by grazing and cutting of the grassland increases the mean residence time of carbon in coarse (>0.2 mm) soil organic fractions. Grassland monoliths (0.5×0.5×0.4 m) were sampled from high and low disturbance treatments in a long-term (14 yrs) grazing experiment and were placed during two years in the mesocosms. During daytime, the canopy enclosure in each mesocosm was supplied in an open flow with air at mean CO2 concentration of 425 µmol mol−1 and δ13C of −21.5±0.27‰. Fully labelled mature grass leaves reached a δ13C of −40.8 (±0.93) and −42.2‰ (±0.60) in the low and high disturbance treatments, respectively, indicating a mean 13C labelling intensity of 12.7‰ compared to unlabelled control grass leaves. After two years, the delta 13C value of total soil organic matter above 0.2 mm was reduced in average by 7.8‰ in the labelled monoliths compared to controls. The isotope mass balance technique was used to calculate for the top (0–10 cm) soil the fraction of 13C labelled carbon in the soil organic matter above 0.2 mm (i.e. roots, rhizomes and particulate organic matter). A first order exponential decay model fitted to the unlabelled C in this fraction shows an increase in mean residence time from 22 to 31 months at low compared to high disturbance. A slower decay of roots, rhizomes and particulate organic matter above 0.2 mm is therefore likely to contribute to the observed increased in soil carbon sequestration in grassland monoliths exposed to low disturbance.