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Soil moisture, temperature and nitrogen availability interactively regulate carbon exchange in a meadow steppe ecosystem
Agricultural and Forest Meteorology ( IF 5.6 ) Pub Date : 2021-03-23 , DOI: 10.1016/j.agrformet.2021.108389
Muqier Hasi , Xueyao Zhang , Guoxiang Niu , Yinliu Wang , Qianqian Geng , Quan Quan , Shiping Chen , Xingguo Han , Jianhui Huang

Primary productivity in terrestrial ecosystems can be significantly altered by the predicted increases in nitrogen (N) deposition, but it is still unclear how N deposition influences the carbon (C) exchange processes especially in dryland ecosystems. In this study, a 3-year experiment with two types of fertilizers and five N addition levels was conducted in a semiarid steppe of Erguna, Inner Mongolia to assess the effects of exogenous N input on net ecosystem productivity (NEP), gross ecosystem productivity (GEP) and ecosystem respiration (ER). Our results showed that enhanced N input significantly increased NEP and GEP when the volumetric soil water content (VWC) was greater than 15% (v/v%), but had trivial and inconsistent effects when VWC was less than that threshold. Moreover, the NEP and GEP increased significantly with increasing N addition but leveled off when the N input reached 10 g N m–2 year–1 and the VWC was above 15%. However, the ER showed a significant increase with N addition rates, regardless of soil water content. Our main findings are as follows. First, the ecosystem C exchange can be significantly enhanced by addition of N only when soil moisture exceeds certain threshold, suggesting co-limitation of water and N in the grassland ecosystem that we studied. Second, in addition to concurrent consideration of water, temperature and N as well as their interactions also need to be accounted for. Third, the frequency of days with the VWC being higher than 15% accounted only around one third of days during the three growing seasons. Taken together, our findings imply that the expected increases of carbon sequestration should be minimal under N deposition in the Inner Mongolia grassland ecosystems.



中文翻译:

土壤水分,温度和氮的有效利用以交互方式调节草甸草原生态系统中的碳交换

预计氮(N)沉积量的增加会大大改变陆地生态系统的初级生产力,但目前尚不清楚氮沉积如何影响碳(C)交换过程,尤其是在旱地生态系统中。在这项研究中,在内蒙古额尔古纳的半干旱草原上进行了为期3年的试验,使用两种肥料和5种氮素添加水平,以评估外源氮素输入对净生态系统生产力(NEP),生态系统总生产力的影响( GEP)和生态系统呼吸(ER)。我们的研究结果表明,当土壤含水量(VWC)大于15%(v / v%)时,增加的氮输入会显着增加NEP和GEP,但当VWC小于该阈值时,其影响却微不足道。而且,–2–1VWC高于15%。但是,无论土壤含水量如何,ER随N的添加而显着增加。我们的主要发现如下。首先,仅当土壤水分超过一定阈值时,通过添加氮可以显着增强生态系统的碳交换,这表明我们研究的草地生态系统中水和氮的共限制。其次,除了同时考虑水,温度和氮以及它们之间的相互作用外,还需要考虑在内。第三,在三个生长季节中,VWC高于15%的天数仅占三分之一。综上所述,我们的研究结果表明,在内蒙古草原生态系统中,在氮沉降下,碳固存的预期增加应该最小。

更新日期:2021-03-23
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