Abstract
Increasing atmospheric nitrogen (N) deposition could profoundly impact community structure and ecosystem functions in forests. However, conventional experiments with understory addition of N (UAN) largely neglect canopy-associated biota and processes and therefore may not realistically simulate atmospheric N deposition to generate reliable impacts on forest ecosystems. Here we, for the first time, designed a novel experiment with canopy addition of N (CAN) vs. UAN and reviewed the merits and pitfalls of the two approaches. The following hypotheses will be tested: i) UAN overestimates the N addition effects on understory and soil processes but underestimates those on canopy-associated biota and processes, ii) with low-level N addition, CAN favors canopy tree species and canopy-dwelling biota and promotes the detritus food web, and iii) with high-level N addition, CAN suppresses canopy tree species and other biota and favors rhizosphere food web. As a long-term comprehensive program, this experiment will provide opportunities for multidisciplinary collaborations, including biogeochemistry, microbiology, zoology, and plant science to examine forest ecosystem responses to atmospheric N deposition.
Highlights
Introduction to the CAN vsUAN facilities Experimental sites.The N manipulative experiments are conducted in Central and South China, respectively (Fig. 1)
This paper described a novel aspect of N deposition manipulation, CAN vs. UAN, to examine forest ecosystem responses to atmospheric N deposition
Concerns about the potential impacts of N deposition on forest ecosystems have led to increasing studies over the last two decades[4,12,13,16,18,19,20,21]
Summary
Wei Zhang1,3,*, Weijun Shen1,*, Shidan Zhu[1], Shiqiang Wan[2], Yiqi Luo[3], Junhua Yan[1], Keya Wang[1], Lei Liu[4], Huitang Dai[5], Peixue Li5, Keyuan Dai[6], Weixin Zhang[1], Zhanfeng Liu[1], Faming Wang[1], Yuanwen Kuang[1], Zhian Li1, Yongbiao Lin[1], Xingquan Rao[1], Jiong Li1, Bi Zou[1], Xian Cai[1], Jiangming Mo1, Ping Zhao[1], Qing Ye1, Jianguo Huang1 & Shenglei Fu1. Conventional experiments with understory addition of N (UAN) largely neglect canopy-associated biota and processes and may not realistically simulate atmospheric N deposition to generate reliable impacts on forest ecosystems. As one of the global change drivers, increasing atmospheric N deposition has the potential to shift the structure and functions of forest ecosystems[3,9,15]. The aims of this study were: i) to provide a comprehensive analysis of the past and ongoing manipulative experiments of N deposition, ii) to introduce a novel approach-CAN, which can more realistically simulate and quantify the forest responses to increasing N deposition, and iii) to test whether the traditional approach-UAN have overestimated the effects of N addition on understory species and soil processes but underestimated the effects on canopy processes
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