中科院采用同位素示追踪技术揭示森林土壤“激发效应”规律变

中科院西双版纳热带植物园博士研究生乔娜和副研究员Douglas Allen Schaefer与中科院地理所、德国哥廷根大学相关研究人员合作，通过同位素示追踪技术，揭示森林土壤的“激发效应”与有机碳平衡。相关文章发表于2013年12月02日的《Global Change biology》杂志上。

中科院采用同位素示追踪技术揭示森林土壤“激发效应”规律变化

由于全球变暖和二氧化碳浓度增加，植物可能提高向地下土壤的碳输入，而这种输入的增加可能影响土壤中原来固持的有机碳释放，形成“激发效应”，但具体的变化规律并不十分清楚。

研究组选择地处热带的西双版纳红壤和地处亚热带的哀牢山棕壤为研究对象，用连续输入可利用性13C的添加方式，模拟植物凋落物分解、根系分泌物向地下碳输入的过程，并与目前多数采用单次添加模拟方式进行了比较。

研究发现：1)单次添加方式高估激发效应对原有土壤有机质的分解;2)尽管可利用性碳输入促进原有有机质的分解，但是残留在土壤中的可利用性碳补偿了因“激发效应”损失的有机碳，这种补偿方式以连续添加方式最高，单次添加方式最低;3)该研究对先前提出的负净碳平衡的观念提出挑战。

该项研究分别在版纳植物土壤生态学研究组与动植物关系研究组完成，哀牢山生态站、西双版纳生态站及公共技术服务中心中心实验室提供了大力支持。

原文摘要：

Labile carbon retention compensates for CO2 released by priming in forest soils

Na Qiao, Douglas Schaefer, Evgenia Blagodatskaya, Xiaoming Zou, Xingliang Xu, Yakov Kuzyakov

Increase of belowground C allocation by plants under global warming or elevated CO2 may promote decomposition of soil organic carbon (SOC) by priming and strongly affects SOC dynamics. The specific effects by priming of SOC depend on the amount and frequency of C inputs. Most previous priming studies have investigated single C additions, but they are not very representative for litterfall and root exudation in many terrestrial ecosystems. We evaluated effects of 13C-labeled glucose added to soil in three temporal patterns: single, repeated, and continuous on dynamics of CO2 and priming of SOC decomposition over 6 months. Total and13C labeled CO2 were monitored to analyze priming dynamics and net C balance between SOC loss caused by priming and the retention of added glucose-C. Cumulative priming ranged from 1.3 to 5.5 mg C g−1 SOC in the subtropical, and from −0.6 to 5.5 mg C g−1 SOC in the tropical soils. Single addition induced more priming than repeated and continuous inputs. Therefore, single additions of high substrate amounts may overestimate priming effects over the short term. The amount of added glucose C remaining in soil after 6 months (subtropical: 8.1–11.2 mg C g−1 SOC or 41-56% of added glucose; tropical: 8.7–15.0 mg C g−1 SOC or 43–75% of glucose) was substantially higher than the net C loss due to SOC decomposition including priming effect. This overcompensation of C losses was highest with continuous inputs and lowest with single inputs. Therefore, raised labile organic C input to soils by higher plant productivity will increase SOC content even though priming accelerates decomposition of native SOC. Consequently, higher continuous input of C belowground by plants under warming or elevated CO2can increase C stocks in soil despite accelerated C cycling by priming in soils.