Effects of Different Nitrogen Additions on Soil Microbial Communities In

Effects of different nitrogen additions on soil microbial communities in different seasons in a boreal forest 1,2 1,3 1 2 1 1 GUOYONG YAN, YAJUAN XING, LIJIAN XU, JIANYU WANG, XIONGDE DONG, WENJUN SHAN, 1 1,2, LIANG GUO, AND QINGGUI WANG 1College of Agricultural Resource and Environment, Heilongjiang University, 74 Xuefu Road, Harbin 150080 China 2School of Forestry, Northeast Forestry University, 26 Hexing Road, Harbin 150040 China 3Institute of Forestry Science of Heilongjiang Province, 134 Haping Road, Harbin 150081 China Citation: Yan, G., Y. Xing, L. Xu, J. Wang, X. Dong, W. Shan, L. Guo, and Q. Wang. 2017. Effects of different nitrogen additions on soil microbial communities in different seasons in a boreal forest. Ecosphere 8(7):e01879. 10.1002/ecs2.1879 Abstract. In the global change scenario, nitrogen (N) deposition has the potential to affect the soil microbial communities that play critical roles in ecosystem functioning. Although the impacts of N deposition on soil microbial communities have been reasonably well studied, microorganism responses to the N addition combined with the seasonal change have rarely been reported. This study was conducted to evaluate À À the effects of different levels of N addition (0, 2.5, 5.0, and 7.5 g NÁm 2Áyr 1) on soil microbial communities in different seasons (spring, summer, and autumn) in a boreal forest. Our results showed that the soil phys- ical–chemical properties were found to be changed by N addition and seasonal changes were correlated with microbial community structure. The N addition and seasonal changes significantly affect the diversity and abundance of the microbial community, while their interactions only affect the bacterial abundance and the fungal diversity. In addition, our results also provided clear evidence for specific responses of microorganisms to the different N additions and each season. Our findings suggest that the microbial community response to N deposition could be the seasonal change and will strongly correlate with environmental change. Key words: boreal forest; nitrogen deposition; seasonal changes; soil microbial communities. Received 15 April 2017; accepted 24 May 2017; final version received 14 June 2017. Corresponding Editor: Michael F. Allen. Copyright: © 2017 Yan et al. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. E-mail: [email protected] INTRODUCTION deposition has increased by 8 kg N/hm2 com- pared with the 1980s (Liu et al. 2013). Increased Atmospheric nitrogen (N) deposition from N deposition can have dramatic impacts on the anthropogenic sources is currently estimated to structure and function of terrestrial ecosystem. be 30–50% greater than that from natural terres- Although attention has been paid to the effect of trial sources (Canfield et al. 2010) and has N deposition on ecosystem functioning, most increased approximately fourfold over the past studies focused on the response of the above- century (IPCC 2013). It is predicted that the rate ground portion, such as aboveground plant pro- of N deposition will continuously increase, and duction, plant community composition, plant by 2050, it may double (Phoenix et al. 2011). diversity, and lignin in the leaf litter (Galloway Especially in China, with the rapid economic et al. 2008, Xia and Wan 2008, Bleeker et al. 2011, growth, the average annual bulk deposition of N Phoenix et al. 2011, Frey et al. 2014). The effects increased to 21.1 kg N/hm2 in the 2000s from of N deposition on the soil microbial communi- 13.2 kg N/hm2 in the 1990s and atmospheric N ties and their related ecological processes remain ❖ www.esajournals.org 1 July 2017 ❖ Volume 8(7) ❖ Article e01879 YAN ET AL. unclear, although they are also important in glo- microorganisms will respond to environmental bal change ecology (Hoover et al. 2012, Li et al. change in the future. 2013a, b, Yao et al. 2014, Zhao et al. 2014, Xiong In addition to N deposition, soil microorgan- et al. 2016). isms also have to face the seasonal variations in Soil microbial communities are directly related environmental conditions such as temperature to soil biogeochemical processes, and they play an and moisture (Lopez-Mondejar et al. 2015). These important role in the soil carbon cycle and soil N seasonal variations result in the seasonal change turnover (Bardgett et al. 2008, Xiong et al. 2014a, in microbial community (Aponte et al. 2010, Kai- b, Zeng et al. 2016). The soil microorganisms can ser et al. 2010, Landesman and Dighton 2011, affect plant growth, soil organic matter decompo- Kuffner et al. 2012, Zhang et al. 2013, Zhou et al. sition and mineralization, nutrient cycling, and 2013, Vorıskova et al. 2014, Siles et al. 2016). Thus, soil degradation (Klaubauf et al. 2010, Li et al. interaction between seasonal change and N depo- 2012, Graham et al. 2016). However, the commu- sition might have an impact on microbial community structure is considered to be a key determi- nities. However, previous studies on the response nant of the functions: Direct change in microbial of microbial communities to the N deposition community structure may alter microbial func- have rarely focused on the seasonal changes. tions and soil N and C dynamics (Fierer et al. Therefore, we designed an experiment to study 2012, Chen et al. 2014, Matulich and Martiny the responses of the soil microbial community to 2014, Leff et al. 2015, Mannisto et al. 2016). There- N addition and seasonal changes. The average fore, the shifts in the structure and composition of annual N deposition in China increased to À À À À the microbial communities are strong indicators 3.5 g NÁm 2Áyr 1 in 2012 from 1.3 g NÁm 2Áyr 1 of soil biochemical processes and essential ecosys- in 1980 due to the increased anthropogenic activi- tem functions (Edmeades 2003, Liu et al. 2006, ties and excessive application of fertilizer, and the À À Pardo et al. 2011). current N deposition rate is 2.5 g NÁm 2Áyr 1 in Nitrogen deposition can affect structure and northern China (Liu et al. 2013). Therefore, we composition of soil microbial communities (Tre- investigated the soil microbial community in a seder 2008, Klaubauf et al. 2010, Tian and Niu controlled experiment plot that has received N 2015, Shi et al. 2016). Many previous experi- addition at four different levels (0, 2.5, 5.0, and À À ments (including field and laboratory) have also 7.5 g NÁm 2Áyr 1) for 4 yr in a boreal forest, identified the major shifts in the microbial com- northern China. The objective of this study was to munity structure under N addition treatments examine the effects of N additions, seasonal (Ramirez et al. 2010a, b, Fierer et al. 2012, changes, and their interaction on soil microbial Ramirez et al. 2012, Koyama et al. 2014, Leff community composition and diversity. We et al. 2015). Moreover, several meta-analyses hypothesized that (1) N addition, seasonal have demonstrated that the responses of soil changes, and their interaction will cause a change microbial communities to experimental N in the microbial community structure; (2) this manipulations might alter soil ecosystem func- change will be via modifying the soil properties tions (Treseder 2008, Janssens et al. 2010, Zhou and underground micro-environmental factors. et al. 2014, Carey et al. 2016). Although previous The Illumina MiSeq sequencing analysis was used studies suggested that N availability was an to determine the taxa of soil bacteria and fungi. important determinant for the dominant life strategy of the soil microbial community (Fierer MATERIALS AND METHODS et al. 2012, Chen et al. 2014, Leff et al. 2015), the relationships between the different microbial Site description taxa and N addition level are variable (Williams Our experiment was conducted in a boreal for- et al. 2013, Zhong et al. 2015), and the mecha- est that is located in Nanwenghe National Natu- nisms underlying the soil microbial feedback in ral Reserve (51°050–51°390 N, 125°070–125°500 E) response to N deposition remain elusive (Zeng in the Greater Khingan Mountains, China. The et al. 2016). Understanding the effect of N depo- climate of the station is a typical cold temper- sition on soil microbial communities is beneficial ate continental climate with a long, cold winter in the prediction of the manner in which soil and a short, warm summer. Mean annual ❖ www.esajournals.org 2 July 2017 ❖ Volume 8(7) ❖ Article e01879 YAN ET AL. temperature is À2.4°C, ranging from À26.3°Cin two sub-samples: One of them was immediately ° January to 18.6 C in July. The mean annual pre- frozen in liquid N2, put into the box containing cipitation is about 489 mm, mainly falling during dry ice, taken back to the laboratory, and stored short summer (July and August). The soil type of at À80°C for nucleic acid extraction, and the the studied areas is mainly stony to sandy loam, other one was packed in an icebox and trans- and the mean soil depth is 20 cm. The dominant ported to the laboratory for nutrient analysis. and principal tree species is Larix gmelinii with a mean stand density of 2852 Æ 99 trees/hm2 and Soil physicochemical properties ° a mean diameter at breast height (1.3 m height, The soil temperature (T5cm, C) and the soil Æ 3 dbh) of 8.98 0.32 cm. moisture (W5cm, volumetric water content, m / m3) at the 5 cm depth were simultaneously mon- Experimental design itored by using a soil temperature probe (EM50; To investigate the effects of N deposition, the N Decagon Devices, Pullman, Washington, USA) addition experiment was established in May 2011.

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