The mechanism that causes the difference in carbon (C) turnover rate in root populations is unclear. The carbon utilization strategy is assumed to be the main causal factor responsible for differences in root turnover rate. In this study, we determined the correlations between root turnover rate, production, and proportions of C allocated to roots using 13CO2 as a labeling gas in a 13C pulse labeling experiment. The proportions of δ13C were measured in various organs of the grass Bothriochloa ischaemum sampled 0, 6, 24, 48, 216, and 360 h after labeling in three treatments: control (CK), mild water stress (MS), and serious water stress (SS). We found that drought stress increased short-term C allocation to belowground. Fine roots have stronger C demand than coarse root under drought condition. The amount of 13C gradually decreased in leaves and increased in soil with time after 13C pulse labeling. Stem 13C increased with the level of stress and peaked at 24 h, while both fine- and coarse-root 13C peaked at 216 h. 13C distributed to fine roots in MS was significantly higher than in the other treatments at 216 h. The fine-root turnover rate in SS treatment was positively correlated with root biomass but not the amount of 13C. Larger C allocation to roots increased fine-root mass in MS, stimulated rapid fine-root turnover, and increased C input to both the rhizosphere and soil. The fine-root turnover in CK was significantly positively correlated with both 13C amount and biomass, which indicated that increasing short-term C input accelerated turnover in the fine-root pool. The C allocation difference between the fine roots and coarse roots may be a key cause of the different turnover rate in the root population.

中文翻译：

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根系碳分配的高度异质性影响干旱胁迫下白草的根周转率和产量

导致根系碳（C）周转率差异的机制尚不清楚。碳利用策略被认为是造成根周转率差异的主要因素。在这项研究中，我们在 13C 脉冲标记实验中使用 13CO2 作为标记气体，确定了根周转率、产量和分配给根的 C 比例之间的相关性。分别在标记后 0、6、24、48、216 和 360 小时采样的草本草的各器官中 δ13C 的比例在三个处理中进行测量：对照（CK）、轻度水分胁迫（MS）和严重水分胁迫(SS)。我们发现干旱胁迫增加了对地下的短期碳分配。在干旱条件下，细根比粗根有更强的碳需求。13C脉冲标记后，随着时间的推移，叶片中的13C含量逐渐减少，土壤中的13C含量逐渐增加。茎 13C 随应力水平增加并在 24 小时达到峰值，而细根和粗根 13C 均在 216 小时达到峰值。在 216 h 时，MS 中细根分布的 13C 显着高于其他处理。SS 处理中细根周转率与根生物量呈正相关，但与 13C 的量无关。对根的更大碳分配增加了 MS 中的细根质量，刺激了细根的快速周转，并增加了对根际和土壤的碳输入。CK中细根周转与13C量和生物量均显着正相关，这表明短期C输入的增加加速了细根池中的周转。