Moss-Dominated Biocrusts Increase Soil Microbial Abundance And

Applied Soil Ecology 117–118 (2017) 165–177 Contents lists available at ScienceDirect Applied Soil Ecology journal homepage: www.elsevier.com/locate/apsoil Moss-dominated biocrusts increase soil microbial abundance and MARK community diversity and improve soil fertility in semi-arid climates on the Loess Plateau of China ⁎ Bo Xiaoa,b, , Maik Vestec,d a Department of Soil and Water Sciences, China Agricultural University, Beijing, 100193, China b State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Chinese Academy of Sciences, Yangling, 712100, China c University of Hohenheim, Institute of Botany (210), Garbenstrasse 30, Stuttgart, 70599, Germany d Brandenburg University of Technology Cottbus-Senftenberg, Soil Protection and Recultivation, Konrad-Wachsmann-Allee 6, Cottbus, 03046, Germany ARTICLE INFO ABSTRACT Keywords: Various ecological functions of biocrusts are mostly determined by their bacterial and fungal abundance and Biological soil crust community diversity, which has not yet been fully investigated. To provide more insights into this issue, we Microbiotic crust collected samples of moss biocrusts, fixed sand, and mobile sand from a watershed with semi-arid climate on the Microbial community composition Loess Plateau of China. The relative abundances and community diversities of soil bacteria and fungi of the Microbial community diversity samples were determined using high-throughput DNA sequencing. Finally, we analyzed the characteristics of Relative abundance of species bacterial and fungal community of the moss biocrusts and their relationships to the content of soil nutrients. Our High-throughput sequencing results showed that the moss biocrusts had 1048 bacterial OTUs (operational taxonomic units) and 58 fungal OTUs, and their Shannon diversity indexes were 5.56 and 1.65, respectively. The bacterial community of the moss biocrusts was dominated by Acidobacteria (24.3%), Proteobacteria (23.8%), Chloroflexi (15.8%), and Actinobacteria (14.5%), and their fungal community was dominated by Ascomycota (68.0%) and Basidiomycota (23.8%). The moss biocrusts had far more bacterial OTUs (≥ 56.9%) but similar number of fungal OTUs as compared with the uncrusted soil, and their Sorenson’s similarity coefficients of bacterial and fungal communities were less than 0.768 and 0.596, respectively. Moreover, the contents of soil nutrients (C, N, P) were significantly correlated with the OTU numbers of bacteria and the relative abundances of bacteria and fungi. Our results indicated that moss biocrusts harbor a large number and high diversity of bacteria and fungi, and these diversified bacteria and fungi play important roles in ecosystem functioning through improving soil fertility. 1. Introduction (Porada et al., 2014; Lenhart et al., 2015; Belnap et al., 2016). The dominant components of biocrusts and their small-scale dis- Biocrusts (also named biological soil crusts) of dry environments are tribution depend on topography, soil characteristics, climates, plant formed by a highly specialized communities of moss and living communities, microhabitats, successional stages, and disturbance re- microorganisms (including soil lichens, green algae, cyanobacteria, gimes (Kidron et al., 2010; Bowker et al., 2016; Bu et al., 2016), but are fungi, and bacteria) as well by excretion of biopolymers (Belnap et al., mostly determined by the local water regimes which is regulated by soil 2016; Xiao et al., 2016). According to the dominating components and texture, microclimatic conditions, and precipitation (Bowker et al., successional development, biocrusts are usually classified as cyanobac- 2016). Generally, biocrusts are dominated by cyanobacteria and soil teria (blue-green algae)-, green algae-, soil lichen-, or moss-dominated lichens in super-arid and arid climates with less than 250 mm of annual biocrusts (Belnap et al., 2016). It has been reported that biocrusts are precipitation (e.g., the Gurbantunggut Desert of China (Zhang et al., widespread in arid and semi-arid climates throughout the world with 2011)), while they are mostly dominated by mosses in semi-arid climate varying species composition and coverage (Belnap et al., 2003a; with 250–500 mm of annual precipitation (e.g., the Loess Plateau of Bowker et al., 2016). Thus, they are considered as an important China (Xiao and Hu, 2017)). In the Negev Desert of Israel, cyanobacter- component of vegetation and land cover in dryland ecosystems ia and green-algae are characteristic for biocrusts in areas with less than ⁎ Corresponding author at: Department of Soil and Water Sciences, China Agricultural University, Beijing, 100193, China. E-mail addresses: [email protected], [email protected] (B. Xiao). http://dx.doi.org/10.1016/j.apsoil.2017.05.005 Received 20 December 2016; Received in revised form 2 May 2017; Accepted 5 May 2017 0929-1393/ © 2017 Elsevier B.V. All rights reserved. B. Xiao, M. Veste Applied Soil Ecology 117–118 (2017) 165–177 170 mm of annual precipitation (Kidron et al., 2010), while moss cover particularly important in nutrient-limited dryland ecosystems because and thickness increase with increasing annual rainfall along the of its usual low level, susceptibility to depletion, and difficulties of climatic gradient (Yair et al., 2011). replenishment (Ravi et al., 2010). Previous studies confirmed that Although the negative effects of biocrusts have been reported biocrusts play a significant role in N cycling of dryland ecosystems, as several times (for example, they smooth the soil surface and prevent they contribute major N inputs via biological fixation (Zhao et al., 2010; plant seeds from penetrating the soil (Deines et al., 2007; Su et al., Su et al., 2011) and capture of dust (Williams and Eldridge, 2011) and 2007; Langhans et al., 2009)), many studies have confirmed that depositional N, harbor intense internal N transformation processes (Hu biocrusts mostly perform positive roles in various ecological processes et al., 2015; Kidron et al., 2015b), and direct N losses via dissolved, such as preventing water and wind erosion (Bowker et al., 2008), gaseous (Lenhart et al., 2015), and erosional loss processes (Li et al., enhancing soil water retention (Zhang et al., 2008), increasing soil C 2013; Barger et al., 2016). Similarly, soil C cycling is also significantly and N (Green et al., 2008), facilitating vascular plant establishment and changed by biocrusts through photosynthetic activity (Hui et al., 2014; growth (Godínez-Alvarez et al., 2012), and promoting soil biodiversity Kidron et al., 2015a) and soil respiration (Castillo-Monroy et al., 2011b; (Castillo-Monroy et al., 2011a). On the other hand, they give strong Yu et al., 2014). On the other side, the soil microorganisms in biocrusts influences on hydrological processes through enhancing or weakening accelerate the decomposition of organic matter, mainly due to the soil infiltration and runoff production depending from the species increasing soil enzyme activities (e.g., urease, alkaline phosphatase, composition (Belnap, 2006; Yair et al., 2011). Particularly, moss invertase, and protease) (Zhang et al., 2012; Liu et al., 2014). In other biocrusts attract more attention because they usually generate much words, the mosses and other cryptogams (i.e., lichens and green-algae) stronger influences on various ecological processes than cyanobacteria, in biocrusts are mainly responsible for the effects on soil formation and green-algae or soil lichen biocrusts due to their greater biomass water conservation (soil physical processes) through their functions in − (> 10 mg cm 2) and larger thickness (> 15 mm vs. ∼3 mm), espe- stabilizing soil surface and holding soil water (Kidron and Tal, 2012; cially in stabilizing soil surface and changing soil water regimes (Xiao Xiao et al., 2016). Their roles in C and N cycling and improving soil et al., 2016; Xiao and Hu, 2017). In general, it is believed that biocrusts fertility (soil chemical and biological processes) are mostly attributed to are important communities for the soil processes and ecosystem the cyanobacteria, green-algae, bacteria, and fungi through their functioning (Bowker et al., 2010), and their rehabilitation are impor- photosynthesis, nitrogen fixation, and effects on soil enzyme activities tant measures for combating land degradation and desertification (Xiao (Belnap et al., 2003b). It is well known that both soil bacteria and fungi et al., 2015). are responsible for important processes (Paul, 2015) even in biocrusts Through stabilizing the soil surface (Zhang et al., 2006), conserving (Maier et al., 2014; Steven et al., 2014; Mueller et al., 2015). For these soil water (Langhans et al., 2009; Xiao et al., 2016), and accumulating reasons, the bacterial and fungal abundance and community diversity nutrients (Li et al., 2008), biocrusts create a favorable microhabitat for of biocrusts are of very high concern owing to their significant roles in other soil microorganisms in dry environments. Therefore, they usually maintaining and improving soil fertility, which are crucial for the harbor a large number and high diversity of soil microorganisms as restoration of degraded lands and vegetation in arid and semi-arid compared with uncrusted soil (Garcia-Pichel et al., 2003; Steven et al., climates (Abed et al., 2013; Steven et al., 2014; Zhang et al., 2014; 2014). These diversified soil microorganisms fundamentally determine Mueller et al., 2015). In addition, the bacterial and fungal community the various important

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