Nonlinear responses of total belowground carbon flux and its components to increased nitrogen availability in temperate forests
Nonlinear responses of total belowground carbon flux and its components to increased nitrogen availability in temperate forests
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温带森林地下总碳通量及其组成部分对氮可用性增加的非线性响应
DOI：
10.1016/j.scitotenv.2020.136954
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发表时间：
2020
影响因子：
9.8
通讯作者：
Hui Zeng
中科院分区：
文献类型：
--
作者：
Wenjing Zeng;Jiangyong Zhang;Lizheng Dong;Wei Wang;Hui Zeng
随着人们对地下碳分配的兴趣日益增加，地下碳通量及其动态已成为一个重要的研究课题。然而，它仍然不确定是否TBCF非线性响应增加氮（N）的可用性和它的主要成分（根和外生菌根（ECM）真菌）如何有助于TBCF。在中国北方温带森林中，我们建立了一个为期4年的N添加试验，包括对照、低N、中N和高N施肥处理。我们测量了TBCF及其三个主要组成部分，包括根呼吸，ECM真菌呼吸和根生产。还测定了相关的土壤和植物因子。TBCF对氮素添加量的增加呈非线性响应，低氮处理对TBCF的促进作用为10.37%，高氮处理对TBCF的抑制作用为10.29%。根系呼吸和ECM真菌呼吸对TBCF贡献模式的对比表明，在不同的氮素有效性条件下，根系和ECM真菌的投资策略不同。氮素处理下根系碳生产与呼吸的比值接近1：2，表明当土壤氮素有效性增加时，根系更倾向于通过溢流呼吸损失碳，而不是将碳固定在新生物量中。低氮处理通过直接增加根系呼吸和间接增加粗根生物量来提高土壤总生物量。中氮添加正影响TBCF通过增加根系呼吸，但这种积极的影响被抵消了显着的负面影响，增加土壤全氮浓度。土壤pH值的降低是高氮条件下降低土壤总有机碳的最有效途径。由于近年来大规模的碳汇管理造林计划，我们的研究结果的TBCF的非线性响应不同的N施肥处理可以提供洞察力，预测地下C固存潜力及其对大气N沉降的响应。
With the increased interest in allocating more carbon (C) belowground for C sequestration, total belowground C flux (TBCF) and its dynamics have become an important research topic. However, it remains uncertain whether TBCF responds nonlinearly to increased nitrogen (N) availability and how its main components (root and ectomycorrhizal (ECM) fungi) contribute to TBCF. We established a four-year N addition experiment with control, low-N, medium-N, and high-N fertilization treatments in a N-limited temperate forest in northern China. We measured TBCF and its three main components including root respiration, ECM fungal respiration, and root production. The involved edaphic and plant factors were also measured. TBCF showed a nonlinear response to the increasing amounts of N addition, accelerated by 10.37% in low-N addition and restrained by 10.29% in high-N addition. Contrasting patterns of the contributions of root respiration and ECM fungal respiration to TBCF implies different strategies of investment in roots and ECM fungi under the different N-availability statuses. The ratio of production and respiration in roots under N addition was nearly 1:2, which indicated that when soil N availability increases, roots prefer to lose C by overflow respiration rather than fix C in new biomass. The low-N addition increased TBCF by directly increasing root respiration and indirectly increasing coarse root biomass. The medium-N addition positively affected TBCF by increasing root respiration but this positive effect was cancelled out by the significantly negative effect of the increased soil total N concentration. The decrease in soil pH was the most effective pathway to decrease TBCF in high-N addition. Because of a large-scale reforestation program for C sink management in recent years, our findings of the nonlinear response of TBCF to different N fertilization treatments could provide insight for predicting belowground C sequestration potential and its response to atmospheric N deposition.